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Sample records for ge sb atraves

  1. I8Sb10Ge36

    Directory of Open Access Journals (Sweden)

    Mohammed Kars

    2010-06-01

    Full Text Available Single crystals of the title compound, octaiodide decaantimonate hexatriacontagermanide, were grown by chemical transport reactions. The structure is isotypic with the analogous clathrates-I. In this structure, the (Ge,Sb46 framework consists of statistically occupied Ge and Sb sites that atoms form bonds in a distorted tetrahedral arrangement. They form polyhedra that are covalently bonded to each other by shared faces. There are two polyhedra of different sizes, viz. a (Ge,Sb20 dodecahedron and a (Ge,Sb24 tetracosahedron in a 1:3 ratio. The guest atom (iodine resides inside these polyhedra with symmetry m3 (Wyckoff position 2a and overline{4}2m (Wyckoff position 2d, respectively.

  2. Phase segregation in Pb:GeSbTe chalcogenide system

    Science.gov (United States)

    Kumar, J.; Ahmad, M.; Chander, R.; Thangaraj, R.; Sathiaraj, T. S.

    2008-01-01

    Effect of Pb substitution on the amorphous-crystalline transformation temperature, optical band gap and crystalline structure of Ge{2}Sb{2}Te{5} has been studied. In Pb:GeSbTe chalcogenide films prepared by thermal evaporation, an amorphous to crystallization transition is observed at 124, 129, 136 and 138 °C in Pb{0}Ge{20}Sb{24}Te{56}, Pb{1.6}Ge{19}Sb{26}Te{54}, Pb{3}Ge{17}Sb{28}Te{53} and Pb{5}Ge{12}Sb{28}Te{55} respectively. XRD investigations of annealed samples reveal that Pb substitution retains NaCl type crystalline structure of GST but expands the lattice due to large atomic radii. The increase in amorphous-crystalline transformation temperature is followed with the increase in phase segregation. The optical gap shows marginal variations with composition.

  3. Density functional simulations of Sb-rich GeSbTe phase change alloys.

    Science.gov (United States)

    Gabardi, S; Caravati, S; Bernasconi, M; Parrinello, M

    2012-09-26

    We generated models of the amorphous phase of Sb-rich GeSbTe phase change alloys by quenching from the melt within density functional molecular dynamics. We considered the two compositions Ge(1)Sb(1)Te(1) and Ge(2)Sb(4)Te(5). Comparison with previous results on the most studied Ge(2)Sb(2)Te(5) allowed us to draw some conclusions on the dependence of the structural properties of the amorphous phase on the alloy composition. Vibrational and electronic properties were also scrutinized. Phonons at high frequencies above 200 cm(-1) are localized in tetrahedra around Ge atoms in Sb-rich compounds as well as in Ge(2)Sb(2)Te(5). All compounds are semiconducting in the amorphous phase, with a band gap in the range 0.7-1.0 eV.

  4. Density functional simulations of Sb-rich GeSbTe phase change alloys

    Science.gov (United States)

    Gabardi, S.; Caravati, S.; Bernasconi, M.; Parrinello, M.

    2012-09-01

    We generated models of the amorphous phase of Sb-rich GeSbTe phase change alloys by quenching from the melt within density functional molecular dynamics. We considered the two compositions Ge1Sb1Te1 and Ge2Sb4Te5. Comparison with previous results on the most studied Ge2Sb2Te5 allowed us to draw some conclusions on the dependence of the structural properties of the amorphous phase on the alloy composition. Vibrational and electronic properties were also scrutinized. Phonons at high frequencies above 200 cm-1 are localized in tetrahedra around Ge atoms in Sb-rich compounds as well as in Ge2Sb2Te5. All compounds are semiconducting in the amorphous phase, with a band gap in the range 0.7-1.0 eV.

  5. Nuclear Magnetic Resonance Studies of Tellurium and Antimony Bonding in Crystal Sb2Te3, GeTe, and Ge2Sb2Te5

    Science.gov (United States)

    Bobela, David C.; Taylor, P. Craig

    2008-10-01

    As a starting point in understanding the magnetic resonance data for amorphous Ge2Sb2Te5, the prototypical phase change material, we have used 121Sb and 125Te nuclear magnetic resonance (NMR) to study crystalline Sb2Te3, GeTe, and Ge2Sb2Te5. The frequency space data are affected by a quadrupole (121Sb only) and chemical shift (121Sb and 125Te) interaction, which reflect the bonding asymmetries occurring around each nuclei. The 125Te data indicate there are two distinct Te sites in Sb2Te3 and one Te site in the GeTe, in agreement with the known crystal structures. The Ge2Sb2Te5125Te data are less well-resolved, which is probably a consequence of the random arrangement of Sb/Ge atoms around the Te sites. Despite the lack of resolution, these data do correspond to the spectral positions and breadths observed in Sb2Te3 and GeTe, which suggests that Ge2Sb2Te5 contains similar Te bonding structures. The 121Sb data in Sb2Te3 show that the Sb sites have an approximately axially symmetric bonding environment. The Sb data in Ge2Sb2Te5 reveal that the average bonding structure of Sb is very different from the Sb sites occurring in Sb2Te3.

  6. Radiation-modified structure of Ge25Sb15S60 and Ge35Sb5S60 glasses.

    Science.gov (United States)

    Kavetskyy, T; Shpotyuk, O; Kaban, I; Hoyer, W

    2008-06-28

    Atomic structures of Ge(25)Sb(15)S(60) and Ge(35)Sb(5)S(60) glasses are investigated in the gamma-irradiated and annealed after gamma-irradiation states by means of high-energy synchrotron x-ray diffraction technique. The first sharp diffraction peak (FSDP) is detected at around 1.1 A(-1) in the structure factors of both alloys studied. The FSDP position is found to be stable for radiation/annealing treatment of the samples, while the FSDP intensity shows some changes between gamma-irradiated and annealed states. The peaks in the pair distribution functions observed between 2 and 4 A are related to the Ge-S, Ge-Sb, and Sb-Sb first neighbor correlations and Ge-Ge second neighbor correlations in the edge-shared GeS(42) tetrahedra, and S-S and/or Ge-Ge second neighbor correlations in the corner-shared GeS(42) tetrahedra. Three mechanisms of the radiation-/annealing-induced changes are discussed in the framework of coordination topological defect formation and bond-free solid angle concepts.

  7. Electrical conduction mechanism in GeSeSb chalcogenide glasses

    Indian Academy of Sciences (India)

    Vandana Kumari; Anusaiya Kaswan; D Patidar; Kananbala Sharma; N S Saxena

    2016-02-01

    Electrical conductivity of chalcogenide glassy system Ge$_{30−x}$Se$_{70}$Sb$_{x}$ ( = 10, 15, 20 and 25) prepared by melt quenching has been determined at different temperatures in bulk through the $I$–$V$ characteristic curves. It is quite evident from results that Poole–Frenkel conduction mechanisms hold good for conduction in these glasses in a given temperature range. The variation in electrical conductivity with composition was attributed to the Se–Sb bond concentration in the Se–Ge–Sb system. Results indicated that Ge$_5$Se$_{70}$Sb$_{25}$ showed the minimum resistance. In view of this the composition Ge$_5$Se$_{70}$Sb$_{25}$ may be coined as ‘critical composition’ in the proposed series. Also the activation energies of conduction of these glassy alloys have been calculated in higher and lower temperature range using the Arrhenius equation.

  8. Ferro electrical properties of GeSbTe thin films; Propiedades ferroelectricas de peliculas delgadas de GeSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Gervacio A, J. J.; Prokhorov, E.; Espinoza B, F. J., E-mail: jgervacio@qro.cinvestav.m [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Queretaro, Libramiento Norponiente No. 2000, Juriquilla, 76230 Queretaro (Mexico)

    2011-07-01

    The aim of this work is to investigate and compare ferro electrical properties of thin GeSbTe films with composition Ge{sub 4}Sb{sub 1}Te{sub 5} (with well defined ferro electrical properties) and Ge{sub 2}Sb{sub 2}Te{sub 5} using impedance, optical reflection, XRD, DSc and Piezo response Force Microscopy techniques. The temperature dependence of the capacitance in both materials shows an abrupt change at the temperature corresponding to ferroelectric-paraelectric transition and the Curie-Weiss dependence. In Ge{sub 2}Sb{sub 2}Te{sub 5} films this transition corresponds to the end from a NaCl-type to a hexagonal transformation. Piezo response Force Microscopy measurements found ferroelectric domains with dimension approximately equal to the dimension of grains. (Author)

  9. Interface effect and stress effect on Ge2Sb2Te5/Sb superlattice-like thin films

    Science.gov (United States)

    Zheng, Long; Zhu, Xiaoqin; Zhai, Liangjun; Hu, Yifeng; Zou, Hua; Liu, Bo; Pei, Mingxu; Song, Zhitang

    2017-04-01

    Ge2Sb2Te5 superlattice-like thin films show great potential for phase-change memory applications. Improvement of the thermal properties of Ge2Sb2Te5 is believed to be related to the Ge2Sb2Te5/Sb interface. The stress effect and interface effect on Ge2Sb2Te5 manifest in structural changes that are observed via X-ray diffraction and Raman spectroscopy experiments. The structure changes from corner-sharing GeTe4-nGen (n = 0) in single-layered Ge2Sb2Te5 to GeTe4-nGen (n = 1, 2, 3) tetrahedra in the superlattice-like thin films that are observed. As a result, Ge2Sb2Te5 prefers the hexagonal structure rather than the face-centred cubic structure during heating.

  10. Fabrication of Multilevel Switching High Density Phase Change Data Recording Using Stacked GeTe/GeSbTe Structure

    Science.gov (United States)

    Hong, Sung-Hoon; Lee, Heon; Kim, Kang-In; Choi, Yunjung; Lee, Young-Kook

    2011-08-01

    The multilevel switching characteristics of stacked phase change materials with the structures of Ge2Sb2Te5, AgInSbTe/Ge2Sb2Te5, and GeTe/Ge2Sb2Te5 were investigated at the nano scale using nanoimprint lithography and conductive atomic force microscopy. Stacked phase change materials devices consisting of nano pillars 200 nm in diameter were fabricated using nanoimprint lithography, and their electrical characteristics were evaluated using conductive atomic force microscopy, with a pulse generator and a voltage source. The stacked GeTe/Ge2Sb2Te5 phase change materials exhibited three levels of resistance with a difference of 2 orders in magnitude between them, while the single-layer and stacked phase change materials with similar electrical resistances, such as Ge2Sb2Te5/AgInSbTe exhibited only bi level switching characteristics.

  11. Sb-Se系和Ge-Sb-Te系粉末材料热力学参数测试%Thermodynamic Parameters of Sb-Se-based and Ge-Sb-Te-based Phase Change Optical Disk Recording Media

    Institute of Scientific and Technical Information of China (English)

    陈志武; 张喜燕

    2001-01-01

    利用DSC对Sb-Se系和Ge-Sb-Te系粉末热力学参数进行了研究,对于Sb-Se系合金,仅在温度为220℃左右时出现一个放热峰,而对于GeSb2Te4与GeSb4Te4合金,分别在140℃及200℃左右各出现一个放热峰,加热速度不同放热峰出现温度略有差别.

  12. Polarity-dependent resistance switching in GeSbTe phase-change thin films : The importance of excess Sb in filament formation

    NARCIS (Netherlands)

    Pandian, Ramanathaswamy; Kooi, Bart J.; Oosthoek, Jasper L. M.; van den Dool, Pim; Palasantzas, George; Pauza, Andrew

    2009-01-01

    We show that polarity-dependent resistance switching in GeSbTe thin films depends strongly on Sb composition by comparing current-voltage characteristics in Sb-excess Ge(2)Sb(2+x)Te(5) and stoichiometric Ge(2)Sb(2)Te(5) samples. This type of switching in Ge(2)Sb(2+x)Te(5) films is reversible with bo

  13. Raman spectra and XPS studies of phase changes in Ge2Sb2Te5 films

    Institute of Scientific and Technical Information of China (English)

    Liu Bo; Song Zhi-Tang; Zhang Ting; Feng Song-Lin; Chen Bomy

    2004-01-01

    Ge2Sb2Te5 film was deposited by RF magnetron sputtering on Si (100) substrate. The structure of amorphous and crystalline Ge2Sb2Te5 thin films was investigated using XRD, Raman spectra and XPS. XRD measurements revealed the existence of two different crystalline phases, which has a FCC structure and a hexagonal structure, respectively.The broad peak in the Raman spectra of amorphous Ge2Sb2Te5 film is due to the amorphous -Te-Te- stretching. As the annealing temperature increases, the broad peak separates into two peaks, which indicates that the heteropolar bond in GeTe4 and the Sb-Sb bond are connected with four Te atoms, and other units such as (TeSb) Sb-Sb (Te2)and (Sb2) Sb-Sb (Te2), where some of the four Te atoms in the above formula are replaced by Sb atoms, remain in crystalline Ge2Sb2Te5 thin film. And from the results of Raman spectra and XPS, higher the annealing temperature,more Te atoms bond to Ge atoms and more Sb atoms substitute Te in (Te2) Sb-Sb (Te2).

  14. GeSbTe deposition for the PRAM application

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Junghyun [Nano Fabrication Center, SAIT, Suwon, P.O. Box 111 (Korea, Republic of); Choi, Sangjoon [Nano Fabrication Center, SAIT, Suwon, P.O. Box 111 (Korea, Republic of); Lee, Changsoo [Nano Fabrication Center, SAIT, Suwon, P.O. Box 111 (Korea, Republic of); Kang, Yoonho [Nano Fabrication Center, SAIT, Suwon, P.O. Box 111 (Korea, Republic of); Kim, Daeil [School of Materials Science and Engineering. University of Ulsan, San 29, Mugeo-Dong, Nam-Gu, Ulsan 680-749 (Korea, Republic of)]. E-mail: dkim84@mail.ulsan.ac.kr

    2007-02-15

    GeSbTe (GST) chalcogenide thin films for the phase-change random access memory (PRAM) were deposited by an atomic layer deposition (ALD) process. New precursors for GST thin films made with an ALD process were synthesized. Among the synthesized precursors, Ge(N(CH{sub 3}){sub 2}){sub 4}, Sb(N(CH{sub 3}){sub 2}){sub 4}, and Te(i-Pr){sub 2} (i-Pr = iso-propyl) were selected. Using the above precursors, GST thin films were deposited using an H{sub 2} plasma-assisted ALD process. Film resistivity abruptly changed after an N{sub 2} annealing process above a temperature of 350 deg. C. Cross-sectional scanning electron microscope (SEM) photographs of the GST films on the patterned substrate with aspect ratio of 7 shows that the step coverage is about 90%.

  15. Nonlinear characterization of GeSbS chalcogenide glass waveguides

    Science.gov (United States)

    Choi, Ju Won; Han, Zhaohong; Sohn, Byoung-Uk; Chen, George F. R.; Smith, Charmayne; Kimerling, Lionel C.; Richardson, Kathleen A.; Agarwal, Anuradha M.; Tan, Dawn T. H.

    2016-12-01

    GeSbS ridge waveguides have recently been demonstrated as a promising mid – infrared platform for integrated waveguide – based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.55 μm. Using self – phase modulation experiments, we characterize a waveguide nonlinear parameter of 7 W‑1/m and nonlinear refractive index of 3.71 × 10‑18 m2/W. GeSbS waveguides are used to generate supercontinuum from 1280 nm to 2120 nm at the ‑30 dB level. The spectrum expands along the red shifted side of the spectrum faster than on the blue shifted side, facilitated by cascaded stimulated Raman scattering arising from the large Raman gain of chalcogenides. Fourier transform infrared spectroscopic measurements show that these glasses are optically transparent up to 25 μm, making them useful for short – wave to long – wave infrared applications in both linear and nonlinear optics.

  16. Characteristics of phase transition and separation in a In-Ge-Sb-Te system

    Science.gov (United States)

    Park, Sung Jin; Jang, Moon Hyung; Park, Seung-Jong; Cho, Mann-Ho; Ko, Dae-Hong

    2012-10-01

    In-doped GeSbTe films were deposited by ion beam sputtering deposition (IBSD) using Ge2Sb2Te5 (GST) and In3Sb1Te2 (IST) as targets. The phase change characteristics of the resulting films were then investigated by electrical measurements, including static testing, in situ 4-point Rs measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The threshold voltage of the films increased, with increasing levels of IST. This phenomenon is consistent with the increased crystallization temperature in X-ray data and in situ 4-point Rs data. In addition, in In28Ge12Sb26Te34, multiple Vth values with a stepwise change are observed. The minimum time for the crystallization of InGeSbTe films was shorter than that for GST. X-ray data and Raman data for the crystalline structure show that phase separation to In2Te3 occurred in all of the InGeSbTe samples after annealing at 350 °C. Moreover, in the case of InGeSbTe films with high concentrations of In (28 at.%), Sb phase separation was also observed. The observed phases indicate that the origin of the phase separation of InGeSbTe films is from the enthalpy change of formation and differences in Ge-Te, In-Te, Sb-Te, In-Sb and In-In bond energies.

  17. Phase analysis of aluminium modified GeSbTe bulk prepared from XRD of samples

    Science.gov (United States)

    Sandhu, Sharanjit; Singh, D.; Kumar, S.; Thangaraj, R.

    2016-05-01

    Various compositions of Aluminium modified GST as Alx(Ge2Sb2Te5)1-x x= 0, 0.15, 0.20, 0.25, 0.30 are prepared to study as a phase change material. Bulk prepared is studied with XRD scans for various phases formed. Phases other than Ge2Sb2Te5 do come in but dominated one is Ge2Sb2Te5 hexagonal phase.

  18. Phase-Change Memory Properties of Electrodeposited Ge-Sb-Te Thin Film

    OpenAIRE

    Huang, Ruomeng; Kissling, Gabriela; Jolleys, Andrew; Bartlett, Philip; Hector, Andrew; Levason, William; Reid, Gillian; De Groot, Cornelis

    2015-01-01

    We report the properties of a series of electrodeposited Ge-Sb-Te alloys with various compositions. It is shown that the Sb/Ge ratio can be varied in a controlled way by changing the electrodeposition potential. This method opens up the prospect of depositing Ge-Sb-Te super-lattice structures by electrodeposition. Material and electrical characteristics of various compositions have been investigated in detail, showing up to three orders of magnitude resistance ratio between the amorphous and ...

  19. Electrical phase change of CVD-grown Ge-Sb-Te thin film device

    OpenAIRE

    Huang, C.C.; B. Gholipour; Ou, J.Y.; Knight, K.J.; Hewak, D. W.

    2011-01-01

    A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film ha...

  20. Polarity-dependent resistance switching in GeSbTe phase-change thin films: The importance of excess Sb in filament formation

    Science.gov (United States)

    Pandian, Ramanathaswamy; Kooi, Bart J.; Oosthoek, Jasper L. M.; van den Dool, Pim; Palasantzas, George; Pauza, Andrew

    2009-12-01

    We show that polarity-dependent resistance switching in GeSbTe thin films depends strongly on Sb composition by comparing current-voltage characteristics in Sb-excess Ge2Sb2+xTe5 and stoichiometric Ge2Sb2Te5 samples. This type of switching in Ge2Sb2+xTe5 films is reversible with both continuous and pulsed dc voltages less than 1.5 V. Low and high resistance states of this switching can be attributed to formation and rupture, respectively, of electrically conductive Sb-bridges between the Ge2Sb2Te5 crystals and electrodes through the resistive amorphous phase. The coexistence of polarity-dependent resistance switching with amorphous-crystalline phase-changes renders great opportunities to expand the applicability of GeSbTe films for data storage applications.

  1. Group IV semiconductor Ge integration with topological insulator Sb2Te3 for spintronic application

    Science.gov (United States)

    Zheng, Beining; Sun, Yu; Wu, Jie; Han, Mei; Wu, Xiaofeng; Huang, Keke; Feng, Shouhua

    2017-03-01

    Sb2Te3/Ge heterojunctions were grown on deoxidized GaAs (0 0 1) substrates by molecular beam epitaxy to explore a new type of spin torque device. Despite the large lattice mismatch between Ge and Sb2Te3, the films display highly uniform fabrication and good crystallinity, which have been confirmed by structural characterization. The band structures of Sb2Te3/Ge heterojunctions were investigated by x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Small chemical shift of Sb 3d5/2 indicates that TI conducting surface is not destroyed, and Ge valence band bending contributes to Fermi level depinning. The band offset of Sb2Te3/Ge heterojunctions is different from common gate dielectric/Ge heterojunctions. The integral quality of the heterostructure reveals the potential of combining topological insulators with semiconductors for the advancement of spintronic devices.

  2. Scanning tunneling microscope light emission spectra of polycrystalline GeSbTe and SbTe

    Science.gov (United States)

    Uehara, Y.; Kuwahara, M.; Katano, S.; Ushioda, S.

    2009-11-01

    We have observed scanning tunneling microscope light emission (STM-LE) spectra of Ge 2Sb 2Te 5 and Sb 2Te 3. Although these chalcogenide alloys exhibit band gaps less than 0.5 eV, the STM-LE was observed with a narrow spectral width at a photon energy of 1.5 eV for both materials. By analyzing its bias voltage, polarity, and temperature dependencies combined with recently reported theoretical electronic structures, we concluded that the STM-LE is excited by electronic transitions taking place in the local electronic structure having a direct gap-like shape with a band gap of 1.5 eV, commonly found in the electronic structures of both materials.

  3. Segregation of Sb in Ge epitaxial layers and its usage for the selective doping of Ge-based structures

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, A. V.; Drozdov, M. N.; Novikov, A. V., E-mail: anov@ipmras.ru; Yurasov, D. V. [Institute for Physics of Microstructures of the Russian Academy of Sciences (Russian Federation)

    2015-11-15

    The segregation of Sb in Ge epitaxial layers grown by the method of molecular beam epitaxy on Ge (001) substrates is investigated. For a growth temperature range of 180–325°C, the temperature dependence is determined for the segregation ratio of Sb in Ge, which shows a sharp increase (by more than three orders of magnitude) with increasing temperature. The strong dependence of the segregation properties of Sb on the growth temperature makes it possible to adapt a method based on the controlled use of segregation developed previously for the doping of Si structures for the selective doping of Ge structures with a donor impurity. Using this method selectively doped Ge:Sb structures, in which the bulk impurity concentration varies by an order of magnitude at distances of 3–5 nm, are obtained.

  4. Comparison of thermal stabilities between Zr9(Ge2Sb2Te5)91 and Ge2Sb2Te5 phase change films

    Science.gov (United States)

    Li, Zengguang; Lu, Yegang; Ma, Yadong; Song, Sannian; Shen, Xiang; Wang, Guoxiang; Dai, Shixun; Song, Zhitang

    2016-10-01

    Phase change memory is regarded as one of the most promising candidates for the next-generation non-volatile memory. Zr9(Ge2Sb2Te5)91 film was investigated as storage material for phase-change memory application. The crystallization temperature (Tc) and 10 years data retention temperature of the Zr9(Ge2Sb2Te5)91 film are about 195 and 106.7°C, respectively, and both higher than that of Ge2Sb2Te5 (GST). The sheet resistance ratio between amorphous and crystalline states is up to four orders of magnitude. The crystalline resistance of Zr9(Ge2Sb2Te5)91 film is higher than GST for one order of magnitude, which contribute to reduce the power consumption for PCM device. Zr9(Ge2Sb2Te5)91 film exhibit larger optical band gap in comparison with GST. Zr9(Ge2Sb2Te5)91 is considered to be a promising material for phase change memory.

  5. Replacement of Ge in GeTe by [Ag +Sb] and rare earths: effect on thermoelectric properties

    Science.gov (United States)

    Levin, E. M.; Hanson, M.; Hanus, R.; Schmidt-Rohr, K.

    2013-03-01

    High-efficiency p-type Te-Sb-Ge-Ag (TAGS) thermoelectric materials are based on the GeTe narrow-band self-dopant semiconductor where Ge can be replaced by up to 16 at.% [Ag +Sb]. To understand the effect of Ge replacement by 4 at.% [Ag +Sb] as well as rare earths atoms, we have synthesized and studied XRD, thermopower, electrical resistivity, thermal conductivity, and 125Te NMR of GeTe and Ag2Sb2Ge46-xRxTe50 with R =Gd, Dy and x = 1, 2. At 700 K, GeTe exhibits a thermopower of +146 μVK-1 and a large power factor, 42 μWcm-1K-2. Replacement of Ge by [Ag +Sb] and rare earths enhances the thermopower, but slightly reduces the power factor due to an increase in electrical resistivity. The thermal conductivity at 300 K of all alloys studied is reduced by a factor of two compared to GeTe. 125Te NMR spin-lattice relaxation time and resonance frequency reflect changes in carrier concentration. However, decrease of thermal conductivity due to carriers and increase of electrical resistivity are mostly due to a reduction of carrier mobility and indicate strong scattering produced by [Ag +Sb] and rare earth atoms. At 700 K, the thermoelectric figure of merit of GeTe is 0.8, whereas that in Ag2Sb2Ge45Dy1Te50 is much larger, 1.2, due to a reduction in thermal conductivity. Enhancement of thermopower is discussed within a model of energy filtering.

  6. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

    OpenAIRE

    Xiaoming Yu; John Robertson

    2016-01-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density fu...

  7. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices.

    OpenAIRE

    Yu, X.; Robertson, J

    2016-01-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density fu...

  8. Phase transformation in Pb:GeSbTe chalcogenide films

    Science.gov (United States)

    Kumar, J.; Kumar, P.; Ahmad, M.; Chander, R.; Thangaraj, R.; Sathiaraj, T. S.

    2008-11-01

    A comprehensive analysis on the amorphous to crystalline phase transformation in Pb:GeSbTe chalcogenide alloy has been discussed. The structure identified with X-ray measurements has been discussed in relation to thermal analysis carried out on bulk samples. Optical constants have been calculated in the 350 to 800 nm wavelength range, using Fresnel's equation. The effect of Pb substitution on the optical contrast in terms of change in reflectivity and optical parameters (viz. refractive index, extinction coefficient) has been discussed. Marginal decrease in the optical contrast has been observed with a small increase in Pb content, which is effective to maintain the sufficient signal to noise ratio for optical phase-change storage.

  9. GeSbTe 与 AgInSbTe 体系相变光盘的研究进展%Compact discs based on phase transformations in GeSbTe and AgInSbTe systems

    Institute of Scientific and Technical Information of China (English)

    张广军; 顾冬红; 王阳; 吴谊群; 干福熹

    2004-01-01

    自Ovshinsky把相变材料用于光存储以来,一大批具有可逆光存储性能的材料不断出现,其中研究较多的是GeSbTe 和AgInSbTe两种体系.文章着重介绍了利用这两种材料制成的相变光盘记录介质的微观结构特点,阐述了其晶化机理;同时,较详细地概述了光盘的堆栈结构及掺杂其他元素对相变光盘性能的影响,并对比说明了GeSbTe 和AgInSbTe两种体系在蓝光记录方面的各自特点.

  10. Characteristics of phase transition and separation in a In-Ge-Sb-Te system

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sung Jin [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Jang, Moon Hyung [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104 (United States); Park, Seung-Jong [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Cho, Mann-Ho, E-mail: mh.cho@yonsei.ac.kr [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Ko, Dae-Hong [Department of Material Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer InGeSbTe films were fabricated via co-deposition stoichiometric GST and IST targets. Black-Right-Pointing-Pointer As the amount of IST was increased in InGeSbTe, the value for V{sub th} and the phase transition temperature were increased. Black-Right-Pointing-Pointer The phase separation in InGeSbTe is caused by differences in the enthalpy change for formation and different atomic concentrations. - Abstract: In-doped GeSbTe films were deposited by ion beam sputtering deposition (IBSD) using Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) and In{sub 3}Sb{sub 1}Te{sub 2} (IST) as targets. The phase change characteristics of the resulting films were then investigated by electrical measurements, including static testing, in situ 4-point R{sub s} measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The threshold voltage of the films increased, with increasing levels of IST. This phenomenon is consistent with the increased crystallization temperature in X-ray data and in situ 4-point R{sub s} data. In addition, in In{sub 28}Ge{sub 12}Sb{sub 26}Te{sub 34}, multiple V{sub th} values with a stepwise change are observed. The minimum time for the crystallization of InGeSbTe films was shorter than that for GST. X-ray data and Raman data for the crystalline structure show that phase separation to In{sub 2}Te{sub 3} occurred in all of the InGeSbTe samples after annealing at 350 Degree-Sign C. Moreover, in the case of InGeSbTe films with high concentrations of In (28 at.%), Sb phase separation was also observed. The observed phases indicate that the origin of the phase separation of InGeSbTe films is from the enthalpy change of formation and differences in Ge-Te, In-Te, Sb-Te, In-Sb and In-In bond energies.

  11. Microstructure and Mechanical Properties of Heat-treated GeSb2Te4 Thin Films

    Institute of Scientific and Technical Information of China (English)

    DING Jianning; XIE Guoxin; FAN Zhen; FU Yongzhong; LING Zhiyong

    2007-01-01

    The effect of annealing on microstructure, adhesive and frictional properties of GeSb2Te4 films were experimentally studied. The GeSb2Te4 films were prepared by radio frequency (RF) magnetron sputtering, and annealed at 200℃ and 340℃ under vacuum circumstance, respectively. The adhesion and friction experiments were mainly conducted with a lateral force microscope (LFM) for the GeSb2Te4 thin films before and after annealing. Their morphology and phase structure were analyzed by using atomic force microscopy (AFM) and X-ray Diffraction (XRD) techniques, and the nanoindention was employed to evaluate their hardness values. Moreover, an electric force microscope (EFM) was used to measure the surface potential. It is found that the deposited GeSb2Te4 thin film undergoes an amorphous-to-fcc and fcc-to-hex structure transition; the adhesion has a weaker dependence on the surface roughness, but a certain correlation with the surface potential of GeSb2Te4 thin films. And the friction behavior of GeSb2Te4 thin films follows their adhesion behavior under a lower applied load. However, such a relation is replaced by the mechanical behavior when the load is relatively higher. Moreover, the GeSb2Te4 thin film annealed at 340℃ presents a lubricative property.

  12. Pulsed laser annealing of highly doped Ge:Sb layers deposited on different substrates

    Science.gov (United States)

    Batalov, R. I.; Bayazitov, R. M.; Faizrakhmanov, I. A.; Lyadov, N. M.; Shustov, V. A.; Ivlev, G. D.

    2016-10-01

    Germanium (Ge) is a promising material for micro- and optoelectronics to produce high speed field-effect transistors, photodetectors, light-emitting diodes and lasers. For such applications tensile-strained and/or highly n-doped Ge layers are needed. The authors have performed the formation of such layers by ion-beam sputtering of composite Sb/Ge target, deposition of thin amorphous Ge:Sb films (~200 nm thick) on different substrates (c-Si, c-Al2O3, α-SiO2) followed by pulsed laser annealing (PLA) for their crystallization and Sb dopant activation. Structural, electrical and optical characterization of Ge:Sb films was carried out using scanning electron microscopy, x-ray diffraction, micro-Raman spectroscopy, secondary ion mass spectrometry methods and by measuring sheet resistance, carrier concentration and photoluminescence. The obtained polycrystalline n-Ge:Sb layers (N Sb ~ 1 at.%) are characterized by increased values of tensile strain (up to 1%) and homogenious Sb dopant distribution within layer thickness. The electrical measurements at 300 K revealed the low sheet resistance (up to 40 Ω/□) and extremely high electron concentration (up to 5.5  ×  1020 cm-3) in Ge:Sb/SiO2 samples that indicated full electrical activation of Sb dopant on SiO2 substrate. The increased values of tensile strain and electron concentration of Ge:Sb films on α-SiO2 are explained by low values of thermal conductivity and thermal expansion coefficients of quartz substrate.

  13. Epitaxial growth of Ge-Sb-Te based phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Perumal, Karthick

    2013-07-30

    Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence X-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb{sub 2}Te{sub 3} thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb{sub 2}Te{sub 3} to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by X-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed.

  14. Influence of sputtering parameters on microstructure and mechanical properties of GeSbTe films

    Institute of Scientific and Technical Information of China (English)

    FU Yong-zhong

    2008-01-01

    GeSb2Te4 films were deposited on Si substrates by RF magnetron sputtering, and the effects of sputtering power on the surface topography and anti-compression properties were studied with atomic force microscope(AFM) and nanoindenter. Meanwhile, the mechanical properties of GeSb2Te4 films with oxygen impurity were also investigated. The results indicate that proper sputtering power is important for obtaining GeSb2Te4 films with high compact structure and low surface roughness, which present good load-support capacity. Although the effect of oxygen impurity on the anti-compression properties of GeSb2Te4 films is not very significant as a whole, certain oxygen dosage can relax the internal stress, thereby the hardness of the films drops slightly.

  15. Electrophysical Properties of Ge-Sb-Te Thin Films for Phase Change Memory Devices

    Science.gov (United States)

    Lazarenko, P. I.; Kozyukhin, S. A.; Sherchenkov, A. A.; Babich, A. V.; Timoshenkov, S. P.; Gromov, D. G.; Zabolotskaya, A. V.; Kozik, V. V.

    2017-01-01

    In this work, we studied temperature dependences of the resistivity and current-voltage characteristics of amorphous thin films based on the materials of a Ge-Sb-Te system of compositions GeSb4Te7 (GST147), GeSb2Te4 (GST124), and Ge2Sb2Te5 (GST225) applied in the phase change memory devices. The effect of changes in the composition of thin films on the crystallization temperature, resistivity of films in amorphous and crystalline states, and on the activation energy of conductivity is determined. It is found that the peculiarity of these materials is the mechanism of two-channel conductivity where the contribution to the conductivity is made by charge carriers excited into localized states in the band tails and by carriers of the delocalized states in the valence band.

  16. Electrically induced phase transition in GeSbTe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bruns, Gunnar; Schlockermann, Carl; Woda, Michael; Wuttig, Matthias [I. Physikalisches Institut Ia, RWTH Aachen, 52056 Aachen (Germany)

    2008-07-01

    While phase change materials have already successfully been applied in rewriteable optical data storage, they are now also promising to form the basis for novel non-volatile electrical data storage devices. To understand the physical concepts of these so-called Phase Change Random Access Memory (PCRAM) it is mandatory to gain a deeper insight into the switching process between the highly resistive amorphous and the lowly resistive crystalline phase. The fast phase transitions between the amorphous and crystalline state of GeSbTe-based alloys has so far often been studied using pulsed laser irradiation. In this work an alternative approach is employed to investigate this transition. Electrical pulses are used to rapidly and reversibly switch between the two states. For these experiments a setup was built with a specially designed contacting circuit board to meet the requirements of electrical measurements on a nanosecond timescale. The influence of the pulse parameters on the change of device resistance was determined for different initial states. Furthermore the high time resolution of 0.4 ns allows investigation of transient electrical effects like the so-called threshold switching first described by Ovshinsky in the late 1960s.

  17. Study of Ge2Sb2Te5 Film for Nonvolatile Memory Medium

    Institute of Scientific and Technical Information of China (English)

    Baowei QIAO; Yunfeng LAI; Jie FENG; Yun LING; Yinyin LIN; Ting'ao TANG; Bingchu CAI; Bomy CHEN

    2005-01-01

    The amorphous Ge2Sb2Te5 film with stoichiometric compositions was deposited by co-sputtering of separate Ge,Sb, and Te targets on SiO2/Si (100) wafer in ultrahigh vacuum magnetron sputtering apparatus. The crystallization behavior of amorphous Ge2Sb2Te5 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). With an increase of annealing temperature, the amorphous Ge2Sb2Te5 film undergoes a two-step crystallization process that it first crystallizes in face-centered-cubic (fcc) crystal structure and finally fcc structure changes to hexagonal (hex) structure. Activation energy values of 3.636±0.137and 1.579±0.005 eV correspond to the crystallization and structural transformation processes, respectively. From annealing temperature dependence of the film resistivity, it is determined th at the first steep decrease of the resistivity corresponds to crystallization while the second one is primarily caused by structural transformation from "fcc"to "hex" and growth of the crystal grains. Current-voltage (I-V) characteristics of the device with 40 nm-thick Ge2Sb2Te5 film show that the Ge2Sb2Te5 film with nanometer order thickness is still applicable for memory medium of nonvolatile phase change memory.

  18. Structural, electric and kinetic parameters of ternary alloys of GeSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Sanchez, E. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Libramiento Norponiente 2000, Ap. Postal 13, Juriquilla, Queretaro, C. P. 76230, (Mexico)]. E-mail: m6007@ciateq.net.mx; Prokhorov, E.F. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Libramiento Norponiente 2000, Ap. Postal 13, Juriquilla, Queretaro, C. P. 76230, (Mexico); Gonzalez-Hernandez, J. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Libramiento Norponiente 2000, Ap. Postal 13, Juriquilla, Queretaro, C. P. 76230, (Mexico); Mendoza-Galvan, A. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Libramiento Norponiente 2000, Ap. Postal 13, Juriquilla, Queretaro, C. P. 76230, (Mexico)

    2005-01-03

    Thin amorphous films of GeSbTe have been widely employed in the technology used for phase change optical memory or compact disks. In this article, we report on measurements of resistance, transmittance, and X-ray diffraction in thin films with stoichiometric compositions of Ge{sub 1}Sb{sub 4}Te{sub 7}, Ge{sub 1}Sb{sub 2}Te{sub 4}, Ge{sub 2}Sb{sub 2}Te{sub 5}, and Ge{sub 4}Sb{sub 1}Te{sub 5.} The resistivity, lattice constant, and the temperature at which transformation from the amorphous phase to the cubic crystalline structure occurs were calculated for each stoichiometric composition, and the energy activation was determined, applying Kissinger's model. It was found that the Ge{sub 4}Sb{sub 1}Te{sub 5} composition has the highest crystallization temperature (425 K), the highest resistivity (0.178 {omega} cm), the greatest E{sub a} (3.09 eV), and the lowest lattice constant (a=5.975 A) in the cubic phase at 170 deg C.

  19. Microstructures and thermoelectric properties of GeSbTe based layered compounds

    Energy Technology Data Exchange (ETDEWEB)

    Yan, F.; Zhu, T.J.; Zhao, X.B. [Zhejiang University, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Hangzhou (China); Dong, S.R. [Zhejiang University, Department of Information and Electronics Engineering, Hangzhou (China)

    2007-08-15

    Microstructures and thermoelectric properties of Ge{sub 1}Sb{sub 2}Te{sub 4} and Ge{sub 2}Sb{sub 2}Te{sub 5} chalcogenide semiconductors have been investigated to explore the possibility of their thermoelectric applications. The phase transformation from the face-centered cubic to hexagonal structure was observed in Ge{sub 2}Sb{sub 2}Te{sub 5} compounds prepared by the melt spinning technique. The Seebeck coefficient and electrical resistivity of the alloys were increased due to the enhanced scattering of charge carriers at grain boundaries. The maximum power factors of the rapidly solidified Ge{sub 1}Sb{sub 2}Te{sub 4} and Ge{sub 2}Sb{sub 2}Te{sub 5} attained 0.975 x 10{sup -3} Wm{sup -1}K{sup -2} at 750 K and 0.767 x 10{sup -3} Wm{sup -1}K{sup -2} at 643 K respectively, higher than those of water quenched counterparts, implying that thermoelectric properties of GeSbTe based layered compounds can be improved by grain refinement. The present results show this class of chalcogenide semiconductors is promising for thermoelectric applications. (orig.)

  20. Dielectric Function and Critical Point of GeSbTe Pseudo-binary Compound Thin Films

    Science.gov (United States)

    Lee, Hosun; Park, Jun-Woo; Kang, Youn-Seon; Lee, Tae-Yon; Suh, Dong-Seok; Kim, Ki-Joon; Kim, Cheol Kyu; Kang, Yoon Ho; da Silva, Juarez L. F.

    2009-03-01

    We measure the dielectric functions of GeSbTe pseudo-binary thin films by using spectroscopic ellipsometry. We anneal the thin films at various temperatures. According to x-ray diffraction, the as-grown thin films are amorphous and the annealed films have metastable and stable crystalline phases. By using standard critical point model, we obtain the accurate values of the energy gap of the amorphous phase as well as the critical point energies of the crystalline thin films. The critical point energies are compared to the band gap energies determined by the method of linear extrapolation of the optical absorption. As the Sb to Ge atomic ratio increases, the optical (band) gap energy of amorphous (crystalline) phase decreases. Standard critical point fitting show several higher band gaps. The electronic band structures and the dielectric functions of the thin films are calculated by using density functional theory and are compared to the measured ones. The band structure calculations show in stable phase that GeTe, Ge2Sb2Te5, and Ge1Sb2Te4 have indirect gap whereas Ge1Sb4Te7 and Sb2Te3 have direct gap. The measured indirect band gap energies match well with the electronic band structure calculations.

  1. Ultralow Resistivity Ge:Sb heterostructures on Si Using Hydride Epitaxy of Deuterated Stibine and Trigermane.

    Science.gov (United States)

    Xu, Chi; Senaratne, Charutha L; Sims, Patrick; Kouvetakis, John; Menéndez, José

    2016-09-14

    The nonconventional deuterated stibine (SbD3) compound has been used for the first time in combination with trigermane (Ge3H8) to produce hyper-doped Ge-on-Si films with carrier concentrations n > 10(20) cm(-3) and record-low resistivities ρ = 1.8 × 10(-4) Ω cm. The growth takes place on Ge and Ge1-xSix buffered Si(100) wafers at ultralow temperatures (∼330 °C) at which Sb diffusion is negligible, leading to extremely flat atomic profiles of the constituents. The Sb substitution in the Ge lattice is determined by RBS channeling and corroborated by high-resolution XRD, which also reveal a systematic increase in lattice constant vs concentration, as expected due to the incorporation of the larger Sb. High-resolution TEM illustrates defect-free monocrystalline structures with device-quality morphologies. The electrical characteristics of the samples are measured using Hall effect and resistivity measurements combined with contactless infrared ellipsometry and are found to be consistent with an extrapolation of the bulk Ge:Sb properties to the high carrier concentrations achieved in our films. The Sb/Ge ratio in the doped layers is approximately the same as that in the precursor reaction mixture, indicating a highly efficient Sb incorporation afforded by the compatible reactivity of the molecules employed in this study. The resultant films are attractive for next generation germanium technologies that require low-resistance n+ junctions or a Fermi level that approaches the direct gap minimum in the conduction band, which drastically enhances the optical emission efficiency of n-type Ge.

  2. Fabrication of SiGeSb heating electrodes and their application for four-terminal chalcogenide programmable switches

    Science.gov (United States)

    Park, Young Sam; Lee, Seung-Yun

    2015-03-01

    This paper reports on sputter-deposited SiGeSb thin films and their application for four-terminal chalcogenide switch devices. The microstructures and electrical properties of the SiGeSb films were highly dependent on antimony concentration and annealing temperature. Microstructural changes such as surface roughening and formation of antimony grains were observed only for the Sb-rich SiGeSb films after annealing at 400 °C and higher. The sheet resistance of the SiGeSb films containing a small amount of antimony changed sporadically with annealing temperature because of a trade-off between activation and surface depletion of antimony. The resistance of the SiGeSb heating electrodes was varied by changing sputtering power for the antimony target and by changing the annealing temperature. Four-terminal chalcogenide switch devices were fabricated with SiGeSb heating electrodes of varying resistance. It was found that the switching voltage of the fabricated switch device was proportional to the resistance of the SiGeSb heating electrode. This indicates that the SiGeSb films with tunable sheet resistance are of great importance in fabricating chalcogenide switch devices and the optimization of the resistance of the SiGeSb film is essential to ensure proper switch operation.

  3. Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge-Sb-Te alloys

    Science.gov (United States)

    Yoon, Sung-Min; Lee, Seung-Yun; Jung, Soon-Won; Park, Young-Sam; Yu, Byoung-Gon

    2009-05-01

    For realizing the next-generation phase-change memories (PCM), it is required to reduce the fluctuation of resistance values in SET state. The Sb-rich phase of GeSbTe was proposed to fulfill the complete crystallization process at each SET programming and the PCM devices were fabricated by using the double-layered phase-change materials composed of GeSbTe and GeSbTe. It was found that the SET resistances and their fluctuation were reduced as the increase of volume ratio of the GeSbTe. We can conclude that the compositional modification into the Sb-rich phase can be a good way for improving the SET performances for the PCM applications.

  4. Effects of Sn Substitution on Thermoelectric Properties of Ge4SbTe5

    Science.gov (United States)

    Williams, Jared B.; Mather, Spencer; Morelli, Donald T.

    2016-02-01

    Phase-change materials are identified by their ability to rapidly alternate between amorphous and crystalline phases upon heating, exhibiting large contrast in the optical/electrical properties of the respective phases. Such materials are primarily used in memory storage applications, but recently they have also been identified as potential thermoelectric materials. Many of the phase-change materials studied today can be found on the pseudobinary (GeTe)1- x (Sb2Te3) x tie-line. Ge4SbTe5, a single-phase compound just off of the (GeTe)1- x (Sb2Te3) x tie-line, forms in a metastable rocksalt crystal structure at room temperature. It has been found that stoichiometric and undoped Ge4SbTe5 exhibits thermal conductivity of ~1.2 W/m-K at high temperature and a dramatic decrease in electrical resistivity at 623 K due to a structural phase transition, which leads to a large enhancement in both thermoelectric power factor and thermoelectric figure of merit at 823 K. Introducing point defects via isoelectronic substitutions can be an effective means of reducing thermal conductivity and enhancing thermoelectric performance. We present a study of the effects of Sn substitution for Ge on the electrical and thermal transport properties of Ge4SbTe5.

  5. The origin of the resistance change in GeSbTe films

    Science.gov (United States)

    Jang, Moon Hyung; Park, Seung Jong; Park, Sung Jin; Cho, Mann-Ho; Kurmaev, E. Z.; Finkelstein, L. D.; Chang, Gap Soo

    2010-10-01

    Amorphous Ge2Sb2Te5 (a-GST) films were deposited by ion beam sputtering deposition. Extended x-ray absorption fine structure (EXAFS) data confirmed the existence of the Ge-Ge homopolar bonds in the films. Raman spectra also indicated that the Ge tetrahedral coordination in the a-GST film disappeared after an annealing treatment above 220 °C. Resonantly excited Ge L2,3 x-ray emission spectra (which probe occupied Ge 3d4s-electronic states) show that the phase change from the amorphous to crystalline state is accompanied by a reduction in the Ge I(L2)/I(L3) intensity ratio due to a L2L3N Coster-Kronig transition, indicating that the number of carriers is increased in the Ge 4sp valence state. These findings constitute direct evidence for the contribution of the Ge electronic states to the resistivity change.

  6. Role of Ge Switch in Phase Transition: Approach using Atomically Controlled GeTe/Sb2Te3 Superlattice

    Science.gov (United States)

    Tominaga, Juniji; Fons, Paul; Kolobov, Alexander; Shima, Takayuki; Chong, Tow Chong; Zhao, Rong; Koon Lee, Hock; Shi, Luping

    2008-07-01

    Germanium-antimony-tellurite (GST) is a very attractive material not only for rewritable optical media but also for realizing solid state devices. Recently, the study of the switching mechanism between the amorphous and crystal states has actively been carried out experimentally and theoretically. Now, the role of the flip-flop transition of a Ge atom in a distorted simple-cubic unit cell is the center of discussion. Turning our viewpoint towards a much wider region beyond a unit cell, we can understand that GeSbTe consists of two units: one is a Sb2Te3 layer and the other is a Ge2Te2 layer. On the based of this simple model, we fabricated the superlattice of GST alloys and estimated their thermal properties by differential scanning calorimetry (DSC). In this paper, we discuss the proof of the Ge switch on the basis of thermo-histories.

  7. Te-centric view of the phase change mechanism in Ge-Sb-Te alloys.

    Science.gov (United States)

    Sen, S; Edwards, T G; Cho, J-Y; Joo, Y-C

    2012-05-11

    The short-range structure of amorphous and fcc Ge1Sb2Te4 and Ge2Sb2Te5 phase-change alloys is investigated using 125Te NMR spectroscopy. Both amorphous and fcc structures consist solely of heteropolar Ge/Sb-Te bonds that may enable rapid displacive phase transformation without the need for extensive atomic rearrangement. The vacancy distribution is random in microcrystalline fcc phases while significant clustering is observed in their nanocrystalline counterparts that may result in the formation of tetrahedrally coordinated Ge atoms in the latter. This structural commonality may further facilitate the kinetics of transformation between amorphous and nanocrystalline fcc phases, a situation relevant for high-density memory storage.

  8. A Novel Approach to Obtain GeSbTe-Based High Speed Crystallizing Materials for Phase Change Optical Recording

    Science.gov (United States)

    2001-04-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012318 TITLE: A Novel Approach to Obtain GeSbTe -Based High Speed...UNCLASSIFIED Mat. Res. Soc. Symp. Proc. Vol. 674 © 2001 Materials Research Society A Novel Approach to Obtain GeSbTe -Based High Speed Crystallizing...fast crystallizing materials based on a conventional GeSbTe alloy for rewritable phase change optical data storage. By means of co-sputtering

  9. New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

    OpenAIRE

    Yong-Jin Park; Ju-Young Cho; Min-Woo Jeong; Sekwon Na; Young-Chang Joo

    2016-01-01

    The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm2), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modu...

  10. Chemical and structural arrangement of the trigonal phase in GeSbTe thin films

    Science.gov (United States)

    Mio, Antonio M.; Privitera, Stefania M. S.; Bragaglia, Valeria; Arciprete, Fabrizio; Bongiorno, Corrado; Calarco, Raffaella; Rimini, Emanuele

    2017-02-01

    The thermal and electrical properties of phase change materials, mainly GeSbTe alloys, in the crystalline state strongly depend on their phase and on the associated degree of order. The switching of Ge atoms in superlattice structures with trigonal phase has been recently proposed to develop memories with reduced switching energy, in which two differently ordered crystalline phases are the logic states. A detailed knowledge of the stacking plane sequence, of the local composition and of the vacancy distribution is therefore crucial in order to understand the underlying mechanism of phase transformations in the crystalline state and to evaluate the retention properties. This information is provided, as reported in this paper, by scanning transmission electron microscopy analysis of polycrystalline and epitaxial Ge2Sb2Te5 thin samples, using the Z-contrast high-angle annular dark field method. Electron diffraction clearly confirms the presence of compositional mixing with stacking blocks of 11, 9 or 7 planes corresponding to Ge3Sb2Te6, Ge2Sb2Te5, and GeSb2Te4, alloys respectively in the same trigonal phase. By increasing the degree of order (according to the annealing temperature, the growth condition, etc) the spread in the statistical distribution of the blocks reduces and the distribution of the atoms in the cation planes also changes from a homogenous Ge/Sb mixing towards a Sb-enrichment in the planes closest to the van der Waals gaps. Therefore we show that the trigonal phase of Ge2Sb2Te5, the most studied chalcogenide for phase-change memories, is actually obtained in different configurations depending on the distribution of the stacking blocks (7-9-11 planes) and on the atomic occupation (Ge/Sb) at the cation planes. These results give an insight in the factors determining the stability of the trigonal phase and suggest a dynamic path evolution that could have a key role in the switching mechanism of interfacial phase change memories and in their data

  11. Chemical and structural arrangement of the trigonal phase in GeSbTe thin films.

    Science.gov (United States)

    Mio, Antonio M; Privitera, Stefania M S; Bragaglia, Valeria; Arciprete, Fabrizio; Bongiorno, Corrado; Calarco, Raffaella; Rimini, Emanuele

    2017-02-10

    The thermal and electrical properties of phase change materials, mainly GeSbTe alloys, in the crystalline state strongly depend on their phase and on the associated degree of order. The switching of Ge atoms in superlattice structures with trigonal phase has been recently proposed to develop memories with reduced switching energy, in which two differently ordered crystalline phases are the logic states. A detailed knowledge of the stacking plane sequence, of the local composition and of the vacancy distribution is therefore crucial in order to understand the underlying mechanism of phase transformations in the crystalline state and to evaluate the retention properties. This information is provided, as reported in this paper, by scanning transmission electron microscopy analysis of polycrystalline and epitaxial Ge2Sb2Te5 thin samples, using the Z-contrast high-angle annular dark field method. Electron diffraction clearly confirms the presence of compositional mixing with stacking blocks of 11, 9 or 7 planes corresponding to Ge3Sb2Te6, Ge2Sb2Te5, and GeSb2Te4, alloys respectively in the same trigonal phase. By increasing the degree of order (according to the annealing temperature, the growth condition, etc) the spread in the statistical distribution of the blocks reduces and the distribution of the atoms in the cation planes also changes from a homogenous Ge/Sb mixing towards a Sb-enrichment in the planes closest to the van der Waals gaps. Therefore we show that the trigonal phase of Ge2Sb2Te5, the most studied chalcogenide for phase-change memories, is actually obtained in different configurations depending on the distribution of the stacking blocks (7-9-11 planes) and on the atomic occupation (Ge/Sb) at the cation planes. These results give an insight in the factors determining the stability of the trigonal phase and suggest a dynamic path evolution that could have a key role in the switching mechanism of interfacial phase change memories and in their data

  12. Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures

    Science.gov (United States)

    Lotnyk, Andriy; Ross, Ulrich; Bernütz, Sabine; Thelander, Erik; Rauschenbach, Bernd

    2016-05-01

    Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications. In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous-crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge2Sb2Te5, Ge1Sb2Te4 and Ge3Sb2Te6 crystal structures intercalated within randomly oriented grains. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature.

  13. Origin, secret, and application of the ideal phase-change material GeSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Noboru [Advanced Technology Research Laboratories, Panasonic Corporation, 3-4 Hikaridai, Seika-cho, Soraku-gun, 619-0237 Kyoto (Japan); Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Central 4, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8562 (Japan)

    2012-10-15

    Discovery of the GeSbTe phase-change alloy in particular along the GeTe-Sb{sub 2}Te{sub 3} tie-line took place in the mid-1980s. The amorphous alloys showed ideal properties, for example, high thermal stability at r.t. and laser-induced rapid crystallization with large optical changes. Thereafter, GeSbTe was successively applied to various optical disks such as DVDs and BDs. Through DSC and XRD analyses, the appearance of the metastable phase having a NaCl-type structure was observed over a wide compositional region. This was the ''key'' to realizing the ideal phase-change properties. During this year, the role of the constituent elements of Ge and Sb became clear by RMC modeling using AXS data at SPring-8, where the ''nucleation dominant crystallization process'' was well explained. The aspect of the latest Blu-ray Disc (BD) product of Panasonic: GeSbTe phase-change films are utilized in every recording layer. It is seen that the front-side recording layers, L1 and L2, are highly transparent. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. A comparison of the Ge-Sb-Te and Si-Sb-Te film oxidization at atmosphere

    Science.gov (United States)

    Ren, Wanchun; Liu, Bo; Song, Zhitang; Jing, Xuezhen; Xiang, Yanghui; Xiao, Haibo; Wang, Zongtao; Zhang, Beichao; Xu, Jia; Wu, Guanping; Qi, Ruijuan; Fan, Chunyan; Duan, Shuqing; Yu, Qinqin; Feng, Songlin

    New phase change materials development has become one of the most critical modules in the fabrication of low power consumption and good data retention phase change memory (PCM). Among various candidates of new phase change materials, SiSbTe (SST) is one of the most promising materials due to its benefits of low RESET current, high crystallization temperature, good adhesion and small volume shrinkage during phase change from amorphous to crystalline state. However, the oxidization of SST film was found when exposing to the atmosphere. By analyzing the depth profile of chemical states, we found oxygen more easily penetrated into the SST film and bonded with Si and Sb compared to GeSbTe (GST) film. The oxidization mechanism between SST and GST was briefly discussed. We achieved 80% improvement of oxidization issue by nitrogen and argon surface treatment. We proposed a manufacturing solution of SST for PCM.

  15. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

    Science.gov (United States)

    Yu, Xiaoming; Robertson, John

    2016-11-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs.

  16. Enhanced thermoelectric performance of In-substituted GeSb6Te10 with homologous structure

    Directory of Open Access Journals (Sweden)

    Atsuko Kosuga

    2014-08-01

    Full Text Available We studied the crystal structure and thermoelectric properties of polycrystalline GeInxSb6−xTe10 (x = 0, 0.18, 0.3, and 0.6. Rietveld and Le Bail analyses showed that all compositions crystallized in trigonal structures with a 51-layer period. Substituting In decreased both the lattice and electronic thermal conductivity, as well as markedly increased the Seebeck coefficient. We ascribed this increase to increases in the effective mass of the carriers, likely caused by the formation of additional energy states near the Fermi level. In GeIn0.6Sb5.4Te10, we found a maximum ZT of 0.75 at 710 K, 1.9 times higher than that of GeSb6Te10.

  17. Effects of oxygen incorporation in GeSbTe films on electrical properties and thermal stability

    Science.gov (United States)

    Jang, Moon Hyung; Park, Seung Jong; Lim, Dong Hyeok; Park, Sung Jin; Cho, Mann-Ho; Cho, Seong Jin; Cho, Yoon Ho; Lee, Jong-Heun

    2010-03-01

    Oxygen incorporated Ge2Sb2Te5 (GST) films were prepared by an ion beam sputtering deposition method. I-V curves of the oxygen incorporated GST active layer showed that the threshold voltage (Vth) varied, depending on the level of incorporated oxygen. In the case of a GST film with an elevated oxygen content of 30.8%, the GST layer melted at 9.02 V due to the instability conferred by the high oxygen content. The formation of Ge-deficient hexagonal phases such as GeSb2Te4 and Sb2Te3 appear to be responsible for the Vth variation. Impedance analyses indicated that the resistance in GST films with oxygen contents of 16.7% and 21.7% had different origins. Thermal desorption spectroscopy data indicate that moisture and hydrocarbons were more readily desorbed at higher oxygen content because the oxygen incorporated GST films are more hydrophilic than undoped GST films.

  18. Thickness and stoichiometry dependence of the thermal conductivity of GeSbTe films

    Science.gov (United States)

    Reifenberg, John P.; Panzer, Matthew A.; Kim, SangBum; Gibby, Aaron M.; Zhang, Yuan; Wong, Simon; Wong, H.-S. Philip; Pop, Eric; Goodson, Kenneth E.

    2007-09-01

    Thermal conduction in GeSbTe films strongly influences the writing energy and time for phase change memory (PCM) technology. This study measures the thermal conductivity of Ge2Sb2Te5 between 25 and 340°C for layers with thicknesses near 60, 120, and 350nm. A strong thickness dependence of the thermal conductivity is attributed to a combination of thermal boundary resistance (TBR) and microstructural imperfections. Stoichiometric variations significantly alter the phase transition temperatures but do not strongly impact the thermal conductivity at a given temperature. This work makes progress on extracting the TBR for Ge2Sb2Te5 films, which is a critical unknown parameter for PCM simulations.

  19. Effects of Ge replacement in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration modified by local electron imbalance

    Science.gov (United States)

    Levin, E. M.; Howard, A.; Straszheim, W. E.

    2015-03-01

    XRD, SEM, EDS, 125Te NMR, Seebeck coefficient, and electrical resistivity of AgxGe50-xTe50 and SbxGe50-xTe50 alloys have been studied. Replacement of Ge in GeTe by Sb significantly increases the Seebeck coefficient, while replacement by Ag decreases it. These effects can be attributed to a change in carrier concentration observed via 125Te NMR spin-lattice relaxation measurements and NMR signal position, which mostly depends on the Knight shift. Variation in carrier concentration in AgxGe50-xTe50 and SbxGe50-xTe50 can be attributed to different electron configurations of valence electrons of Ag (4d105s1) and Sb (5s25p3) compared to that of Ge (4s24p2) resulting in local electron imbalances and changing the concentration of charge carrier (holes) generated by Ge vacancies. In contrast, our 125Te NMR and Seebeck coefficient data for Ag2Sb2Ge46Te50 are similar to those observed for GeTe. This shows that effects from Ag and Sb compensate each other and indicates the existence of [Ag +Sb] pairs. The effects of Ge replacement in GeTe by Ag, Sb, or [Ag +Sb] on rhombohedral lattice distortion also have been analyzed. Interplay between the Seebeck coefficient and electrical resistivity in these alloys results in variation of power factor; the value of 45 mW/cm K2, the highest among known tellurides, was found for Sb2Ge48Te50.

  20. Vacancy Structures and Melting Behavior in Rock-Salt GeSbTe

    OpenAIRE

    Bin Zhang; Xue-Peng Wang; Zhen-Ju Shen; Xian-Bin Li; Chuan-Shou Wang; Yong-Jin Chen; Ji-Xue Li; Jin-Xing Zhang; Ze Zhang; Sheng-Bai Zhang; Xiao-Dong Han

    2016-01-01

    Ge-Sb-Te alloys have been widely used in optical/electrical memory storage. Because of the extremely fast crystalline-amorphous transition, they are also expected to play a vital role in next generation nonvolatile microelectronic memory devices. However, the distribution and structural properties of vacancies have been one of the key issues in determining the speed of melting (or amorphization), phase-stability, and heat-dissipation of rock-salt GeSbTe, which is crucial for its technological...

  1. Shape effects of GeSbTe nanodots on the near-field interaction with a silver triangle antenna

    Science.gov (United States)

    Kojima, Naoto; Ota, Norio; Asakawa, Kiyoshi; Shiraishi, Kenji; Yamada, Keisaku

    2015-04-01

    We investigated the shape effects of GeSbTe nanodots on the near-field interaction with a silver triangle antenna using the three-dimensional finite-difference time-domain method, avoiding the difficulty of detecting near-field signals from a single dot that occurs in current measurements. The surface plasmon resonance of silver strengthens the near-field around nanodots made of GeSbTe, commonly used in phase-change recording. Using GeSbTe spheres and pillar dots with various top plane shapes, we investigated the relationship between the inner electric field concentration of GeSbTe nanodots and the radius of curvature of the corners facing the antenna tip. Reducing the radius of curvature strengthens the inner electric field of the dots, enhancing the near-field difference in intensity for the GeSbTe phase change. GeSbTe diamond pillars with a radius of curvature of 1 nm exhibit a near-field difference in intensity of 28% for the phase change. Using the antenna and the GeSbTe nanodot array, optical write-once recording is realized. The preliminary research in this study is expected to realize future optical disk storage using GeSbTe nanodots with diameters below 10 nm.

  2. Atomic-scale quantification of interdiffusion and dopant localization in GeSbTe-based memory devices

    Science.gov (United States)

    Chae, B.-G.; Seol, J.-B.; Song, J.-H.; Jung, W.-Y.; Hwang, H.; Park, C.-G.

    2016-09-01

    Fabrication of phase-change memory devices at modest or ambient temperatures leads to nanoscale compositional variations in phase-transition layers, where amorphous-polycrystalline phase change takes place via electrical switching, and can alter the device's performances. Here, by transmission electron microscopy and atom probe tomography, we address that thermal annealing at 400 °C for 20 min induces an elemental interdiffusion in the devices consisting of TiN (top electrode), carbon-doped GeSbTe (phase-transition layer), and TiSiN (bottom heater). With respect to the employed annealing process, the Ge atoms of GeSbTe layer have diffused into TiSiN layer at a given sample volume, while the Ti atoms of TiSiN layer into GeSbTe layer. Furthermore, non-random nature of dopant distribution in the GeSbTe materials leads to a Ti-localization including dopants at the GeSbTe/TiSiN interfaces. Our findings have two important implications: First, the annealing-driven interdiffusion of Ge and Ti is a predominant mechanism responsible for nanoscale compositional variations in GeSbTe layer; second, such an interdiffusion and the resultant dopant localization play a crucial role on the driving force for amorphous-polycrystalline transition of GeSbTe-based memory devices.

  3. Grayscale image recording on Ge2Sb2Te5 thin films through laser-induced structural evolution.

    Science.gov (United States)

    Wei, Tao; Wei, Jingsong; Zhang, Kui; Zhao, Hongxia; Zhang, Long

    2017-02-14

    Chalcogenide Ge2Sb2Te5 thin films have been widely exploited as binary bit recording materials in optical and non-volatile electronic information storage, where the crystalline and amorphous states are marked as the information bits "0" and "1", respectively. In this work, we demonstrate the use of Ge2Sb2Te5 thin films as multi-level grayscale image recording materials. High-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through taking advantage of laser-induced structural evolution characteristic. Experimental results indicate that the change of laser energy results in the structural evolution of Ge2Sb2Te5 thin films. The structural evolution induces the difference of electronic polarizability and reflectivity, and high-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through direct laser writing method, accordingly.

  4. Grayscale image recording on Ge2Sb2Te5 thin films through laser-induced structural evolution

    Science.gov (United States)

    Wei, Tao; Wei, Jingsong; Zhang, Kui; Zhao, Hongxia; Zhang, Long

    2017-02-01

    Chalcogenide Ge2Sb2Te5 thin films have been widely exploited as binary bit recording materials in optical and non-volatile electronic information storage, where the crystalline and amorphous states are marked as the information bits “0” and “1”, respectively. In this work, we demonstrate the use of Ge2Sb2Te5 thin films as multi-level grayscale image recording materials. High-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through taking advantage of laser-induced structural evolution characteristic. Experimental results indicate that the change of laser energy results in the structural evolution of Ge2Sb2Te5 thin films. The structural evolution induces the difference of electronic polarizability and reflectivity, and high-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through direct laser writing method, accordingly.

  5. Effect of Annealing Temperature on the Microstructure and Resistivity of Ge2Sb2Te5 Films

    Institute of Scientific and Technical Information of China (English)

    LIU Bo; SONG Zhi-Tang; FENG Song-Lin; CHEN Bomy

    2004-01-01

    @@ The effect of annealing temperature on crystallization of amorphous Ge2Sb2 Te5 films with thickness of 40 nm is studied by TEM and AFM methods. The relationship between microstructure and resistivity of the Ge2Sb2 Te5film is investigated. From the TEM measurements, the grain size of crystallites increases gradually as the annealing temperature increases. When the annealing temperature is too high, voids are formed, which may originate from evaporation of the Ge2Sb2 Te5 film at the elevated temperatures, formation of sink, being nucleated by residual vacancies, and surface roughness. The resistivity of the Ge2Sb2 Te5 film decreases with the increasing annealing temperature and has slight changes when the temperature is higher than 400 ℃. Phase transitions and scattering of crystallite boundaries may be the major factors affecting the resistivity of the Ge2Sb2 Te5 film.

  6. Grayscale image recording on Ge2Sb2Te5 thin films through laser-induced structural evolution

    Science.gov (United States)

    Wei, Tao; Wei, Jingsong; Zhang, Kui; Zhao, Hongxia; Zhang, Long

    2017-01-01

    Chalcogenide Ge2Sb2Te5 thin films have been widely exploited as binary bit recording materials in optical and non-volatile electronic information storage, where the crystalline and amorphous states are marked as the information bits “0” and “1”, respectively. In this work, we demonstrate the use of Ge2Sb2Te5 thin films as multi-level grayscale image recording materials. High-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through taking advantage of laser-induced structural evolution characteristic. Experimental results indicate that the change of laser energy results in the structural evolution of Ge2Sb2Te5 thin films. The structural evolution induces the difference of electronic polarizability and reflectivity, and high-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through direct laser writing method, accordingly. PMID:28195209

  7. Sb含量对GeTe-Sb相变薄膜电学性能和微观结构的影响%The characteristics of GeTe-Sb thin films with different Sb concentration for phase change memory

    Institute of Scientific and Technical Information of China (English)

    谷立新; 周夕淋; 张斌; 张滔; 刘显强; 韩晓东; 吴良才; 宋志棠; 张泽

    2013-01-01

    通过磁控溅射方法制备了不同成分的GeTe-Sb薄膜,利用电阻-温度(R-T)测试、X射线衍射(XRD)和电子显微学方法对其进行了电学性能和微观结构的表征.发现薄膜的晶化温度随着Sb含量的增加先升高后降低;XRD分析表明Sb含量的不同导致薄膜晶体结构的不同,GeTe-9.9%Sb和GeTe-21%Sb为GeTe型立方结构,GeTe-58% Sb,GeTe-72%Sb和GeTe-81.5% Sb呈Sb型菱方结构.在GeTe型和Sb型结构中,薄膜的晶粒尺寸都与晶化温度变化趋势相反.原位加热实验证实了Sb的加入对薄膜结晶机制产生了很大影响,GeTe-9.9% Sb是典型的形核主导,而GeTe-72%Sb则更趋向于生长为主导的结晶机制.%By electrical resistivity measurement,X-ray diffraction techniques and advanced in situ TEM annealing techniques,the thermal stability of GeTe-Sb films with different Sb concentrations (0%,9.9%,21%,58%,72%,81.5% Sb) and their corresponding microstructures were thoroughly investigated.The crystallization temperature shows a summit when Sb concentration approximates 58%.After crystallized,the GeTe-0% Sb and GeTe-0% Sb films are identified as GeTe-type cubic structure.The GeTe58% Sb,72% Sb and 81.5% Sb films are Sb-type rhombohedra structure.The in-situ TEM annealing experiments show that the optimization of the properties by tuning Sb concentration is related to the corresponding crystallization behavior change,indicating a promising way for material optimization.

  8. Theoretical and experimental investigations of the properties of Ge2Sb2Te5 and indium-doped Ge2Sb2Te5 phase change material

    Science.gov (United States)

    Singh, Gurinder; Kaura, Aman; Mukul, Monika; Singh, Janpreet; Tripathi, S. K.

    2014-06-01

    We have carried out comprehensive computational and experimental study on the face-centered cubic Ge2Sb2Te5 (GST) and indium (In)-doped GST phase change materials. Structural calculations, total density of states and crystal orbital Hamilton population have been calculated using first-principle calculation. 5 at.% doping of In weakens the Ge-Te, Sb-Te and Te-Te bond lengths. In element substitutes Sb to form In-Te-like structure in the GST system. In-Te has a weaker bond strength compared with the Sb-Te bond. However, both GST and doped alloy remain in rock salt structure. It is more favorable to replace Sb with In than with any other atomic position. X-ray diffraction (XRD) analysis has been carried out on thin film of In-doped GST phase change materials. XRD graph reveals that In-doped phase change materials have rock salt structure with the formation of In2Te3 crystallites in the material. Temperature dependence of impedance spectra has been calculated for thin films of GST and doped material. Thickness of the as-deposited films is calculated from Swanepoel method. Absorption coefficient (α) has been calculated for amorphous and crystalline thin films of the alloys. The optical gap (indirect band gap) energy of the amorphous and crystalline thin films has also been calculated by the equation α hν = β (hν - E_{{g }} )2 . Optical contrast (C) of pure and doped phase change materials have also been calculated. Sufficient optical contrast has been found for pure and doped phase change materials.

  9. Thermal and Electrical Conductivity of Ge1Sb4Te7 Chalcogenide Alloy

    Science.gov (United States)

    Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

    2017-02-01

    The unique properties of the Ge1Sb4Te7 alloy as a chalcogenide make it a good candidate for application in phase-change random access memory as well as thermoelectric materials. The thermal and electrical conductivity of the Ge1Sb4Te7 alloy play an important role in both applications. This work aims to determine the thermal conductivity and electrical resistivity of the Ge1Sb4Te7 alloy as a function of temperature and to discuss the thermal conduction mechanism. Thermal conductivity and electrical resistivity were measured from room temperature to 778 K using the hot strip method and the four-terminal method, respectively. The thermal conductivity of the Ge1Sb4Te7 alloy shows an interesting temperature dependence: it decreases up to about 600 K, and then increases with increasing temperature. The electrical resistivity shows a monotonic increase with increasing temperature. Through a discussion of the thermal conductivity results together with electrical resistivity results, it is proposed that electronic thermal conductivity dominates the thermal conductivity, while the bipolar diffusion contributes to the increase in the thermal conductivity at higher temperatures. The resonance bonding existing in this chalcogenide alloy accounts for the low lattice thermal conductivity.

  10. Phase Transition Phenomena in Ultra-Thin Ge2Sb2Te5 Film

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ting; LIU Bo; SONG Zhi-Tang; LIU Wei-Li; FENG Song-Lin; CHEN Bomy

    2005-01-01

    @@ We observe reversible phase transition phenomena in proto-type chalcogenide random access memory (C-RAM)devices adopting ultra-thin (12nm) Ge2Sb3 Te5 thin film. In this kind of proto-type device, the ultra-thin amorphous Ge2Sb2 Te5 thin film undergoes a crystallization process when a voltage is applied. The polycrystalline Ge2Sb3 Te5 remain unchanged when the voltage is below 0.6 V. A higher power is needed if the transition from polycrystalline to amorphous is expected. The re-amorphization process can be realized by applying a voltage higher than 0.7 V. The threshold voltage Vth and threshold electric field Eth of the transition from the polycrystalline state to the amorphous state in this proto-type device are ~0.7 V and ~ 5 × 105 V/cm, respectively. The programming voltage is significantly reduced compared to the values of C-RAM devices adopting a 200-nm-thick Ge2Sb2 Te5 inset.

  11. Topological states and phase transitions in Sb2Te3-GeTe multilayers

    Science.gov (United States)

    Nguyen, Thuy-Anh; Backes, Dirk; Singh, Angadjit; Mansell, Rhodri; Barnes, Crispin; Ritchie, David A.; Mussler, Gregor; Lanius, Martin; Grützmacher, Detlev; Narayan, Vijay

    2016-06-01

    Topological insulators (TIs) are bulk insulators with exotic ‘topologically protected’ surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb2Te3 and the band insulator GeTe, we provide experimental evidence of multiple topological modes in a single Sb2Te3-GeTe-Sb2Te3 structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb2Te3-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases.

  12. Young's modulus and residual stress of GeSbTe phase-change thin films

    NARCIS (Netherlands)

    Nazeer, Hammad; Bhaskaran, Harish; Woldering, Léon A.; Abelmann, Leon

    2015-01-01

    The mechanical properties of phase change materials alter when the phase is transformed. In this paper, we report on experiments that determine the change in crucial parameters such as Young's modulus and residual stress for two of the most widely employed compositions of phase change films, Ge1Sb2T

  13. Compositional Dependence Of Hardness Of Ge-Sb-Se Glass For Molded Lens Applications

    Directory of Open Access Journals (Sweden)

    Park J.K.

    2015-06-01

    Full Text Available Chalcogenide glass in the ternary Ge-Sb-Se system is inherently moldable, thus being considered as a strong candidate material for use in infrared-transmitting lens applications from the viewpoint of thermal and mechanical stability. In an effort to experimentally determine compositional region suitable for the molded lens applications, we evaluate its compositional dependence of hardness. Among the constituent atoms, Ge content turns out to exert a most conspicuous correlation with hardness. This phenomenological behavior is then explained in connection with the structural evolution that Ge brings about.

  14. First principles study of crystal Si-doped Ge2Sb2Te5

    Science.gov (United States)

    Yan, Beibei; Yang, Fei; Chen, Tian; Wang, Minglei; Chang, Hong; Ke, Daoming; Dai, Yuehua

    2017-02-01

    Ge2Sb2Te5 (GST) and Si-doped GST with hexagonal structure were investigated by means of First-principles calcucations. We performed many kinds of doping types and studied the electronic properties of Si-doped GST with various Si concentrations. The theoretical calculations show that the lowest formation energy appeared when Si atoms substitute the Sb atoms (SiSb). With the increasing of Si concentrations from 10% to 30%, the impurity states arise around the Fermi level and the band gap of the SiSb structure broadens. Meanwhile, the doping supercell has the most favorable structure when the doping concentration keeps in 20%. The Si-doped GST exhibits p-type metallic characteristics more distinctly owing to the Fermi level moves toward the valence band. The Te p, d-orbitals electrons have greater impact on electronic properties than that of Te s-orbitals.

  15. Ge2Sb2Te5/SnSe2 nanocomposite multilayer thin films for phase change memory application

    Science.gov (United States)

    Feng, Xiaoyi; Wen, Ting; Zhai, Jiwei; Lai, Tianshu; Wang, Changzhou; Song, Sannian; Song, Zhitang

    2014-10-01

    By nanocompositing Ge2Sb2Te5 and SnSe2, the electrical and thermal proprieties of Ge2Sb2Te5/SnSe2 multilayer films for phase change random access memory (PCRAM) are better than those of Ge2Sb2Te5 films. The crystallization temperature rises and can be controlled. The resistance gap can reach approximately five orders of magnitude to ensure high data reliability. The activity energy (Ea) is more than 2.60 eV and the temperature for 10 year data retention reach 110 °C. The analysis of both XRD patterns and TEM images confirmed the reversible phase change transition between amorphous and crystalline state in Ge2Sb2Te5/SnSe2 nanocomposite multilayer films. According to transient photoreflectance traces, the speed of crystallization process was about 33 ns. Among different Ge2Sb2Te5/SnSe2 multilayer films, the film constitute of [Ge2Sb2Te5 (4 nm)/SnSe2(10 nm)]7 showed better properties and was manufactured by CMOS technology to phase change memory (PCM) cells. This result revealed that the Ge2Sb2Te5/SnSe2 nanocomposite multilayer film is a promising phase change material.

  16. XPS study on the selective wet etching mechanism of GeSbTe phase change thin films with tetramethylammonium hydroxide

    Science.gov (United States)

    Deng, Changmeng; Geng, Yongyou; Wu, Yiqun

    Phase change lithography has pretty potential applications for high density optical data storage mastering and micro/nano structure patterning because it is not restricted by optical diffraction limitation and at relatively low cost. GeSbTe, as an initially investigated material for phase change lithography, its mechanism of selective etching in inorganic or organic alkaline aqueous solutions, such as NaOH and tetramethylammonium hydroxide (TMAH), is still unknown. In this paper, XPS measurement is used to study the selective wet etching mechanism of GeSbTe phase change thin films with TMAH solution, and the results show that oxidization played an important role in the etching process. Ge, Sb and Te are oxidized into GeO2, Sb2O5 and TeO2, respectively, and then as the corresponding salts dissolved into the etchant solution. Ge-X (X is Ge, Sb or Te) bonds are first broken in the etching, then Sb-X bonds, and finally Te-Te bonds. To confirm the effect of oxidization in the etching, H2O2 as an oxidant is added into the TMAH solution, and the etching rates are increased greatly for both amorphous and crystalline states. The selective etching mechanism of Ge2Sb2Te5 phase change films is discussed by the difference of bonds breakage between the amorphous and crystalline states.

  17. Using Ge Secondary Phases to Enhance the Power Factor and Figure of Merit of Ge17Sb2Te20

    Science.gov (United States)

    Williams, Jared B.; Morelli, Donald T.

    2016-08-01

    Thermoelectric materials are the leading candidate today for applications in solid-state waste-heat recovery/cooling applications. Research and engineering has pushed the ZT, and overall conversion efficiency, of these materials to values which can be deemed practical for commercialization. However, many of the state-of-the-art thermoelectric materials of today utilize elements which are toxic, such as Ag, Pb, Tl, and Cd. Alloys of GeTe and Sb2Te3 were first explored for their applications in phase-change memory, because of their ability to rapidly alternate between crystalline and amorphous phases. Recently, these materials have been identified as materials with ZT (S 2 T/ρκ, where S is the Seebeck coefficient, ρ is the electrical resistivity, T is the operating temperature, and κ is the thermal conductivity) much greater than unity. In this work, the influence of elemental Ge as a secondary phase on transport in Ge17Sb2Te20 was explored. It was found that Ge introduces an additional scattering mechanism, which leads to increased electrical resistivity, Seebeck coefficient, and power factor values as high as 36 μW cm-1 K-2. The thermal conductivity was slightly reduced and the ZT was enhanced across the entire temperature range of measurement, with peak values greater than 2.

  18. Effect of Sb on the optical properties of the Ge-Se chalcogenide thin films

    Science.gov (United States)

    Abdel-Wahab, F.; Ali karar, N. N.; El Shaikh, H. A.; Salem, R. M.

    2013-08-01

    Thin films of Ge30-xSbxSe70 (x=0, 5, 10 and 15) were prepared by thermal evaporation technique. All samples were confirmed as amorphous according to XRD results. The complex dielectric functions and optical parameters of the films determined by using the Swanepoel's method from transmittance spectra at room temperature in the range of wavelength 400-1100 nm. It has been found that by increasing Sb content, the optical band gap decreases, while the refractive index and the extinction coefficient increase. The optical energy gap of the films under test was discussed in terms of the chemically ordered model (COM) and random covalent network model (RCNM). We confirmed, using Raman spectroscopy, by addition of Sb the intensity of Ge-Ge and Ge-Se bands decreased; however, Sb-Se, and Se-chain band increased, in agreement with COM and RCNM. The results of the refractive index were studied using the Wemple equation. The variations of the refractive index and real part of dielectric constant associated with the changes of the density were examined with the well-known Lorentz-Lorenz relation. The experimental results were found to be in good agreement with those of theoretical ones.

  19. Interband characterization and electronic transport control of nanoscaled GeTe/Sb 2Te3 superlattices

    Science.gov (United States)

    Caretta, Antonio; Casarin, Barbara; Di Pietro, Paola; Perucchi, Andrea; Lupi, Stefano; Bragaglia, Valeria; Calarco, Raffaella; Lange, Felix Rolf Lutz; Wuttig, Matthias; Parmigiani, Fulvio; Malvestuto, Marco

    2016-07-01

    The extraordinary electronic and optical properties of the crystal-to-amorphous transition in phase-change materials have led to important developments in memory applications. A promising outlook is offered by nanoscaling such phase-change structures. Following this research line, we study the interband optical transmission spectra of nanoscaled GeTe/Sb2Te3 chalcogenide superlattice films. We determine, for films with varying stacking sequence and growth methods, the density and scattering time of the free carriers, and the characteristics of the valence-to-conduction transition. It is found that the free carrier density decreases with increasing GeTe content, for sublayer thicknesses below ˜3 nm. A simple band model analysis suggests that GeTe and Sb2Te3 layers mix, forming a standard GeSbTe alloy buffer layer. We show that it is possible to control the electronic transport properties of the films by properly choosing the deposition layer thickness, and we derive a model for arbitrary film stacks.

  20. GeSb2 Te4亚稳相原子结构的透射电子显微学研究%The atomic structure of the GeSb2 Te4 metastable phase

    Institute of Scientific and Technical Information of China (English)

    朱海音; 宋建祥; 刘显强

    2015-01-01

    由于Ge原子在相变过程中的重要作用,使其在GeSbTe合金亚稳相中的局域结构长期以来为人们所关注。本文利用电子衍射技术和基于电子衍射的径向分布函数,以及高分辨电子显微学,对GeSb2 Te4亚稳相的原子结构进行了深入研究。径向分布函数G( r)显示,在GeSb2 Te4亚稳相中几乎所有的Ge原子都为四面体构型;实验及模拟高分辨像结果表明,由于几乎所有的Ge占据Te四面体的中心,GeSb2 Te4亚稳相形成了一种类尖晶石结构而非人们广泛接受的岩盐矿结构。%The local structures of Ge in metastable GeSbTe crystalline phases have long been concerned due to their key role in the phase transition. In this paper, the atomic structure of the GeSb2 Te4 metastable phase was investigated by using the radial distribution function based on the electron diffraction and high resolution transmission electron microscopy. The radial distribution function G( r) reveals that almost all of Ge are located in the tetrahedral centers of Te fcc lattice in the well⁃developed GeSb2 Te4 metastable phase. The high resolution transmission electron microscopy image and the corresponding simulations further indicate that a pseudo⁃spinel structure with tetrahedral Ge has formed, but not the generally accepted rocksalt structure.

  1. Structural and vibrational investigations on Ge{sub 34}Sb{sub 66} solid solutions produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Rebelo, Q.H.F.; Cotta, E.A. [Departamento de Física, Universidade Federal do Amazonas, 69077-000 Manaus, Amazonas (Brazil); Souza, S.M. de, E-mail: s.michielon@gmail.com [Departamento de Física, Universidade Federal do Amazonas, 69077-000 Manaus, Amazonas (Brazil); Trichês, D.M. [Departamento de Física, Universidade Federal do Amazonas, 69077-000 Manaus, Amazonas (Brazil); Machado, K.D. [Departamento de Física, Centro Politécnico, Universidade Federal do Paraná, 81531-990 Curitiba, Paraná (Brazil); Lima, J.C. de; Grandi, T.A. [Departamento de Física, Centro de Ciências Exatas, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina (Brazil); Poffo, C.M. [Departamento de Eng. Mecânica, Centro de Ciências Tecnológicas, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina (Brazil); Manzato, L. [Instituto Federal de Educação, Ciência e Tecnologia do Amazonas, 69075-351 Manaus, Amazonas (Brazil)

    2013-10-25

    Highlights: •A Ge{sub 34}Sb{sub 66} solid solution was prepared by mechanical alloying. •X-ray diffraction results indicate complete dissolution of Ge on the Sb matrix. •Raman measurements indicate the presence of nanocrystalline Ge dispersed in the matrix. -- Abstract: A nanostructured solid solution Ge{sub 34}Sb{sub 66} was produced from Ge and Sb by mechanical alloying and its structural and vibrational properties were investigated by X-ray diffraction (XRD) and micro-Raman spectroscopy. The Rietveld refinement of the XRD measurements allowed the investigation of the evolution of the solid solution with the milling time. The Bragg peaks of the Sb solvent phase showed a strongly reflection-indices-dependent line broadening due to the spatial variation of the Sb/Ge ratio. The asymmetric broadening in the deformed peaks was analyzed considering the Stephens model. Volume fractions of crystalline and interfacial components of the milled powder were estimated from the XRD patterns. Although XRD measurements indicated the formation of a solid solution, Raman measurements revealed the presence of nanocrystalline Ge, and its crystallite size was estimated from the Raman analysis.

  2. Ultrafast optical manipulation of atomic motion in multilayer Ge-Sb-Te phase change materials

    Directory of Open Access Journals (Sweden)

    Fons P.

    2013-03-01

    Full Text Available Phase change random access memory devices have evolved dramatically with the recent development of superlattice structure of Ge-Sb-Te material (GST-SL in terms of its low power consumption. The phase change in GST-SL is mainly characterized by the displacement of Ge atoms. Here we examine a new phase change method, that is the manipulation of Ge-Te bonds using linearly-polarized femtosecond near-infrared optical pulses. As a result, we found that the p-polarized pump pulse is more effective in inducing the reversible and irreversible displacement of Ge atoms along [111] direction in the local structure. This structural change would be induced by the anisotropic carrier-phonon interaction along the [111] direction created by the p-polarized pulse.

  3. Thermoelectric properties of c-GeSb{sub 0.75}Te{sub 0.5} to h-GeSbTe{sub 0.5} thin films through annealing treatment effects

    Energy Technology Data Exchange (ETDEWEB)

    Vora-ud, Athorn, E-mail: athornvora-ud@snru.ac.th [Program of Physics, Faculty of Science and Technology, Sakon Nakhon Rajabhat University, Mueang District, Sakon Nakhon 47000 (Thailand); Thermoelectrics Research Center, Research and Development Institution, Sakon Nakhon Rajabhat University, Mueang District, Sakon Nakhon 47000 (Thailand); Horprathum, Mati, E-mail: mati.horprathum@nectec.or.th [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Eiamchai, Pitak [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Muthitamongkol, Pennapa; Chayasombat, Bralee; Thanachayanont, Chanchana [National Metal and Materials Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Pankiew, Apirak [National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Klamchuen, Annop [National Nanotechnology Center, National Science and Technology Development Agency, Pathumthani 12120 (Thailand); Naenkieng, Daengdech; Plirdpring, Theerayuth; Harnwunggmoung, Adul [Thermoelectric and Nanotechnology Research Center, Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, Huntra Phranakhon, Si Ayutthaya 13000 (Thailand); Charoenphakdee, Anek [NANO-Thermoelectrics Research Center, Division of Applied Physics, Faculty of Sciences and Liberal Arts, Rajamangala University of Technology Isan, Mueng Nakorn Ratchasima 30000 Thailand (Thailand); Somkhunthot, Weerasak [Program of Physics, Faculty of Science and Technology, Loei Rajabhat University, Muang District, Loei 42000 (Thailand); and others

    2015-11-15

    Germanium–Antimony–Tellurium (Ge–Sb–Te) thin films were deposited on silicon wafers with 1-μm silicon dioxide (SiO{sub 2}/Si) by pulsed dc magnetron sputtering from a 99.99% GeSbTe target of 1:1:1 ratio at ambient temperature. The samples were annealed at 573, 623, 673, and 723 K for 3600 s in a vacuum state. The effects of the annealing treatment on phase identification, atomic composition, morphology and film thickness, carrier concentration, mobility, and Seebeck coefficient of the Ge–Sb–Te samples have been investigated by grazing-incidence X-ray diffraction, auger electron spectroscopy, field-emission scanning electron microscopy, Hall-effect measurements, and steady state method, respectively. The results demonstrated that the as-deposited Ge–Sb–Te sample was amorphous. Atomic composition of as-deposited and annealed films at 573 K and 623 K were GeSb{sub 0.75}Te{sub 0.5} while annealed films at 673 K and 723 K were GeSbTe{sub 0.5} due to Sb-rich GeSb{sub 0.75}Te{sub 0.5}. The samples annealed at 573 K and 623 K showed the crystal phases of cubic structure (c-GeSb{sub 0.75}Te{sub 0.5}) into hexagonal structure (h-GeSbTe{sub 0.5}) after annealing at 673 K and 723 K. The study demonstrated the insulating condition from the as-deposited GeSbTe film, and the changes towards the thermoelectric properties from the annealing treatments. The GeSbTe films annealed at 673 K yielded excellent thermoelectric properties with the electrical resistivity, Seebeck coefficient, and power factor at approximately 1.45 × 10{sup −5} Ωm, 71.07 μV K{sup −1}, and 3.48 × 10{sup −4} W m{sup −1} K{sup −2}, respectively. - Highlights: • GeSbTe thin films were successfully sputtered for thermoelectric properties. • GeSbTe films were examined among physical, electrical and thermoelectric properties. • Thermoelectric properties were discussed based on composition of the films.

  4. Infrared-Induced Sluggish Dynamics in the GeSbTe Electron Glass

    Science.gov (United States)

    Ovadyahu, Z.

    2015-07-01

    The electron-glass dynamics of Anderson-localized GeSbTe films is dramatically slowed down following a brief infrared illumination that increases the system carrier concentration (and thus its conductance). These results demonstrate that the dynamics exhibited by electron glasses is more sensitive to carrier concentration than to disorder. In turn, this seems to imply that many-body effects such as the orthogonality catastrophe must play a role in the sluggish dynamics observed in the intrinsic electron glasses.

  5. Coexistence of electron-glass phase and persistent photoconductivity in GeSbTe compounds

    Science.gov (United States)

    Ovadyahu, Z.

    2015-03-01

    It is demonstrated that persistent photoconductivity (PPC), well studied in lightly-doped semiconductors, is observable in GeSbTe compounds using infrared excitation at cryogenic temperatures. The low levels of energy flux necessary to induce an appreciable effect seems surprising given the high carrier concentration n of these ternary alloys (n >1020cm-3 ). On the other hand, their high density of carriers makes GeSbTe films favorable candidates for exhibiting intrinsic electron-glass effects with long relaxation times. These are indeed observed in GeSbTe thin films that are Anderson-localized. In particular, a memory dip is observed in samples with sheet resistances larger than ≈105Ω at T ≈4 K with similar characteristics as in other systems that exhibit intrinsic electron-glass effects. Persistent photoconductivity, however, is observable in GeSbTe films even for sheet resistances of the order of 103Ω , well below the range of disorder required for observing electron-glass effects. These two nonequilibrium phenomena, PPC and electron glass, are shown to be of different nature in terms of other aspects as well. In particular, their relaxation dynamics is qualitatively different; the excess conductance Δ G associated with PPC decays with time as a stretched exponential whereas a logarithmic relaxation law characterizes Δ G (t ) of all electron glasses studied to date. Surprisingly, the magnitude of the memory dip is enhanced when the system is in the PPC state. This counter-intuitive result may be related to the compositional disorder in these materials extending over mesoscopic scales. Evidence in support of this scenario is presented and discussed.

  6. Vacancy Structures and Melting Behavior in Rock-Salt GeSbTe

    Science.gov (United States)

    Zhang, Bin; Wang, Xue-Peng; Shen, Zhen-Ju; Li, Xian-Bin; Wang, Chuan-Shou; Chen, Yong-Jin; Li, Ji-Xue; Zhang, Jin-Xing; Zhang, Ze; Zhang, Sheng-Bai; Han, Xiao-Dong

    2016-05-01

    Ge-Sb-Te alloys have been widely used in optical/electrical memory storage. Because of the extremely fast crystalline-amorphous transition, they are also expected to play a vital role in next generation nonvolatile microelectronic memory devices. However, the distribution and structural properties of vacancies have been one of the key issues in determining the speed of melting (or amorphization), phase-stability, and heat-dissipation of rock-salt GeSbTe, which is crucial for its technological breakthrough in memory devices. Using spherical aberration-aberration corrected scanning transmission electron microscopy and atomic scale energy-dispersive X-ray mapping, we observe a new rock-salt structure with high-degree vacancy ordering (or layered-like ordering) at an elevated temperature, which is a result of phase transition from the rock-salt phase with randomly distributed vacancies. First-principles calculations reveal that the phase transition is an energetically favored process. Moreover, molecular dynamics studies suggest that the melting of the cubic rock-salt phases is initiated at the vacancies, which propagate to nearby regions. The observation of multi-rock-salt phases suggests another route for multi-level data storage using GeSbTe.

  7. Compositional modification of Se-Ge-Sb chalcogenide glasses by addition of arsenic element

    Science.gov (United States)

    Ghayebloo, M.; Tavoosi, M.; Rezvani, M.

    2017-06-01

    The modification of structural, thermal and optical properties of Se-Ge-Sb glasses by addition of arsenic element was the goal of this study. In this regards, six different glasses of Se60Ge40-xSb5Asx (0 ≤ x ≤ 15) were prepared by conventional melt quenching technique in quartz ampoule. The produced samples were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), UV-Vis-NIR spectrophotometer, Fourier transform infrared (FTIR) and Raman spectroscopy. The fundamental absorption edge for of the glasses was analyzed in terms of the theory proposed by Davis and Mott. Based on the obtained results, the glass transition temperature, optical energy gap and Urbach energy of prepared glasses in this alloying system were in the range of 325-380 °C, 1.43-1.64 eV and 0.03-0.3547 eV, respectively. The as prepared glasses show anomalous behavior at 5-7.5 mole% of arsenic for the glass transition temperature, transmittance, absorption edge, optical energy gap and Urbach energy. Based on the Raman spectra, the structural analysis indicates that, increasing the network connectivity upon increasing the arsenic content up to 7.5 mole% is the main reason of anomalous behavior in Se60Ge40-xSb5Asx (0 ≤ x ≤ 15) system.

  8. Effect of InP Doping on the Phase Transition of Thin GeSbTe Films

    Science.gov (United States)

    Bang, Ki Su; Oh, Yong Jun; Lee, Seung-Yun

    2015-08-01

    We report the crystallization and phase-transition behavior of GeSbTe thin films doped with indium phosphorus (InP). Pure GeSbTe thin films and InP-doped GeSbTe thin films were prepared by use of an rf magnetron sputtering method. After thermal annealing, electrical and optical changes in the thin films were observed. Sheet resistance and reflectance measurements revealed that InP doping suppresses crystallization of GeSbTe. X-ray diffraction analysis confirmed that addition of In and P atoms inhibits the phase transition from face-centered cubic to hexagonal closed-packed. Nucleation of the doped GeSbTe thin films was delayed at an annealing temperature of 100°C; after thermal annealing, neither segregation nor formation of a secondary phase occurred. These results indicate that InP doping improves the amorphous stability of GeSbTe thin films. It is believed this enhanced amorphous stability is a result of the formation of multiple, strong crosslinks by the In and P atoms.

  9. Phase-change properties of GeSbTe thin films deposited by plasma-enchanced atomic layer depositon

    Science.gov (United States)

    Song, Sannian; Yao, Dongning; Song, Zhitang; Gao, Lina; Zhang, Zhonghua; Li, Le; Shen, Lanlan; Wu, Liangcai; Liu, Bo; Cheng, Yan; Feng, Songlin

    2015-02-01

    Phase-change access memory (PCM) appears to be the strongest candidate for next-generation high-density nonvolatile memory. The fabrication of ultrahigh-density PCM depends heavily on the thin-film growth technique for the phase-changing chalcogenide material. In this study, Ge2Sb2Te5 (GST) and GeSb8Te thin films were deposited by plasma-enhanced atomic layer deposition (ALD) method using Ge [(CH3)2 N]4, Sb [(CH3)2 N]3, Te(C4H9)2 as precursors and plasma-activated H2 gas as reducing agent of the metallorganic precursors. Compared with GST-based device, GeSb8Te-based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth-dominated crystallization mechanism of the Sb-rich GeSb8Te films. These results show that ALD is an attractive method for preparation of phase-change materials.

  10. Evolution of E-centers during the annealing of Sb-doped Si0.8Ge0.2

    DEFF Research Database (Denmark)

    Kilpeläinen, S.; Tuomisto, F.; Slotte, J.

    2011-01-01

    evolution was observed at the temperature range 450–650 K. Both treatments were shown to induce changes in the chemical surroundings of the E-centers via introduction of Ge near the defects. Moreover, Sb was found to hinder these changes by stabilizing the E-centers and thus preventing them from finding Ge...

  11. Switching of localized surface plasmon resonance of gold nanoparticles on a GeSbTe film mediated by nanoscale phase change and modification of surface morphology

    Science.gov (United States)

    Hira, T.; Homma, T.; Uchiyama, T.; Kuwamura, K.; Saiki, T.

    2013-12-01

    As a platform for active nanophotonics, localized surface plasmon resonance (LSPR) switching via interaction with a chalcogenide phase change material (GeSbTe) was investigated. We performed single-particle spectroscopy of gold nanoparticles placed on a GeSbTe thin film. By irradiation with a femtosecond pulsed laser for amorphization and a continuous wave laser for crystallization, significant switching behavior of the LSPR band due to the interaction of GeSbTe was observed. The switching mechanism was explained in terms of both a change in the refractive index and a modification of surface morphology accompanying volume expansion and reduction of GeSbTe.

  12. Switching of localized surface plasmon resonance of gold nanoparticles on a GeSbTe film mediated by nanoscale phase change and modification of surface morphology

    Energy Technology Data Exchange (ETDEWEB)

    Hira, T.; Homma, T.; Uchiyama, T.; Kuwamura, K.; Saiki, T. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama, Kanagawa 223-8522 (Japan)

    2013-12-09

    As a platform for active nanophotonics, localized surface plasmon resonance (LSPR) switching via interaction with a chalcogenide phase change material (GeSbTe) was investigated. We performed single-particle spectroscopy of gold nanoparticles placed on a GeSbTe thin film. By irradiation with a femtosecond pulsed laser for amorphization and a continuous wave laser for crystallization, significant switching behavior of the LSPR band due to the interaction of GeSbTe was observed. The switching mechanism was explained in terms of both a change in the refractive index and a modification of surface morphology accompanying volume expansion and reduction of GeSbTe.

  13. Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope

    Energy Technology Data Exchange (ETDEWEB)

    Yang Fei [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhang Rui; Geng Lei; Tong Liang; Xu Jun [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Su Weining; Yu Yao [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Ma Zhongyuan; Chen Kunji [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2012-10-01

    Graphical abstract: Nano-sized marks on GST thin film were fabricated using Conductive-AFM (Atomic Force Microscope). The AFM morphology images show that the marks are ablated at the center and a raised ring surrounding it. Highlights: Black-Right-Pointing-Pointer Microstructure of GeSbTe thin films was characterized by XRD and AFM. Black-Right-Pointing-Pointer Annealing and applying electrical field can induce crystallization on thin film. Black-Right-Pointing-Pointer Conductive-AFM was used to modify the surface of GeSbTe thin film. - Abstract: GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20 Degree-Sign C to 300 Degree-Sign C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase. Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I-V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I-V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I-V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I-V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

  14. Electrical Properties of Ag-Doped Ge2Sb2Te5 Films Used for Phase Change Random Access Memory

    Institute of Scientific and Technical Information of China (English)

    XIA Ji-Lin; LIU Bo; SONG Zhi-Tang; FENG Song-Lin; CHEN Bomy

    2005-01-01

    @@ Ag-doped Ge2Sb2 Te5 films were deposited by rf magnetron sputtering on SiO2/Si substrates.The content of Ag ranging from 4.5 to 11.3 at.% is determined by inductively coupled plasma atomic emission spectrometry.The crystallization temperature of Ag-doped Ge2Sb2 Te5 increases with the increasing Ag content and the stability of phase change film is improved greatly.Structures were measured by x-ray diffraction and the face-centered-cubic structure was more stable after Ag doping.Four-point probe was used to measure the sheet resistance of Agdoped Ge2Sb2 Te5 films annealed at different temperatures and it is indicated that Ag atoms increase the sheet resistance of Ge2Sb2 Te5 thin film when the annealing temperature is higher than about 360℃, which is beneficial for reducing the reset current.Current-voltage curves were tested and it is demonstrated that 4.5 at.% Ag doping into the Ge2Sb2Te5 film can reduce the threshold current from 1.46mA to 0.25mA and can only increase the threshold voltage slightly, which is very useful for low energy consumption.

  15. Investigation on the crystallization properties and structure of oxygen-doped Ge8Sb92 phase change thin films

    Science.gov (United States)

    Wu, Weihua; He, Zifang; Chen, Shiyu; Zhai, Jiwei; Song, Sannian; Song, Zhitang

    2017-03-01

    Effects of oxygen incorporation on the crystallization characteristics and crystal structure of Ge8Sb92 films were systematically investigated. The amorphous-to-crystalline transition was studied by in situ resistance measurement. The thermal stability, electrical resistance and band gap of Ge8Sb92 material increase significantly by the addition of oxygen. X-ray diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy illustrate that a small amount of oxygen dopant can inhibit the grain growth and limit the grain size because of the formation of Ge and Sb oxide. Atomic force microscopy and x-ray reflectivity results indicate that the film surface becomes smoother and the film thickness change becomes smaller after oxygen doping. Phase change memory cells based on oxygen-doped Ge8Sb92 film were fabricated to evaluate the electrical properties as well. All the results demonstrate that suitable incorporation of oxygen is an effective way to enhance the comprehensive performance of Ge8Sb92 thin films for phase change memory application.

  16. Temperature dependence of structural and optical properties of GeSbTe alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chabli, A. E-mail: achabli@cea.fr; Vergnaud, C.; Bertin, F.; Gehanno, V.; Valon, B.; Hyot, B.; Bechevet, B.; Burdin, M.; Muyard, D

    2002-09-01

    Ge{sub 2}Sb{sub 2}Te{sub 5} films sandwiched by ZnS-SiO{sub 2} layers were studied by spectroscopic ellipsometry from room temperature up to 800 deg. C. An irreversible modification of both materials is pointed out. ZnS cubic phase precipitation occurs after heating at 650 deg. C, shown by grazing incidence X-ray diffraction. Chemical modification in phase change material is observed above 300 deg. C, revealed by a typical behavior of a transparent layer.

  17. Photo-induced structural changes in Ge-Sb-Se films

    Science.gov (United States)

    Lin, Li; Wang, Guoxiang; Shen, Xiang; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua

    2017-03-01

    Amorphous Ge-Sb-Se thin films have been prepared by the radio-frequency (RF) magnetron co-sputtering deposition technique, and their intrinsic photosensitivity and photo-induced structural changes have been investigated. The results show a crossover from photodarkening (PD) to photobleaching (PB) in the films when the film compositions change from Se-deficient to rich. Further Raman analysis on these as-prepared thin films irradiated with a laser of wavelength 655 nm in every five minutes provides direct evidence of photo-induced structure rearrangements.

  18. Radiation-optical effects in glassy Ge-As(Sb)-S systems

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.I. E-mail: karat@ipm.lviv.ua; Golovchak, R.Ya.; Kavetsky, T.S.; Kovalskiy, A.P.; Vakiv, M.M

    2000-05-02

    The influence of {gamma}-irradiation on the optical properties of chalcogenide bulk glasses from both As{sub 2}S{sub 3}-Ge{sub 2}S{sub 3} and Sb{sub 2}S{sub 3}-Ge{sub 2}S{sub 3} sections of the corresponding glass forming regions has been studied. The '{gamma}-darkening' effect has been observed after radiation treatment by {sup 60}Co {gamma}-quanta with 4.4x10{sup 6} Gy dose. The changes in the optical transmission coefficient have been analyzed according to network arrangement and degree of disorder in the different compositions of chalcogenide glasses.

  19. Short Range Order Signature in Crystalline and Amorphous GeSbTe Xanes Spectra

    Science.gov (United States)

    Raty, Jean-Yves; Otjacques, C. Éline; Pekoz, Rengin; Bichara, Christophe; Lordi, Vince

    2011-03-01

    A new implementation of XANES spectra calculations within DFT and PAW potentials is used to compute the XANES spectra of various amorphous and crystalline GeSbTe structures. A clear correlation between the local order, either tetrahedral or distorted octahedral, and the shape of the XANES signal is observed. These calculations provide a new interpretation of past XANES measurements, relating essentially the phase change mechanism to a moderate modification of the local environment of the Ge atoms. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work was supported by the Belgian PAI 3/42 program and the FNRS-FRFC.

  20. Enhanced thermoelectric performance of In-substituted GeSb{sub 6}Te{sub 10} with homologous structure

    Energy Technology Data Exchange (ETDEWEB)

    Kosuga, Atsuko, E-mail: a-kosuga@21c.osakafu-u.ac.jp; Matsuzawa, Mie; Fujii, Yousuke [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Nakai, Kazuki [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Funahashi, Ryoji [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577 (Japan); Tachizawa, Takuya; Kubota, Yoshiki [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Kifune, Kouichi [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Faculty of Engineering, Hiroshima Institute of Technology, Hiroshima 731-5193 (Japan)

    2014-08-01

    We studied the crystal structure and thermoelectric properties of polycrystalline GeIn{sub x}Sb{sub 6−x}Te{sub 10} (x = 0, 0.18, 0.3, and 0.6). Rietveld and Le Bail analyses showed that all compositions crystallized in trigonal structures with a 51-layer period. Substituting In decreased both the lattice and electronic thermal conductivity, as well as markedly increased the Seebeck coefficient. We ascribed this increase to increases in the effective mass of the carriers, likely caused by the formation of additional energy states near the Fermi level. In GeIn{sub 0.6}Sb{sub 5.4}Te{sub 10}, we found a maximum ZT of 0.75 at 710 K, 1.9 times higher than that of GeSb{sub 6}Te{sub 10}.

  1. Land/groove optical recording with GeTe/Sb2Te3 superlattice-like structure

    Institute of Scientific and Technical Information of China (English)

    Wei Qiang(墙威); Luping Shi; Towchong Chong; Yang Cao(曹阳)

    2004-01-01

    A superlattice-like (SLL) structure was applied to phase-change optical recording. The recording layer consisting of alternating thin layers of two different phase-change materials, GeTe and Sb2Tes, were grown by magnetron sputtering on polycarbonate substrates. Land/groove optical recording was adopted to suppress crosstalk and obtain a large track density. Dynamic properties of the SLL disc were investigated with the shortest 1T pulse duration of 8 ns. Clear eye pattern was observed after 10000 direct overwrite cycles. Erasability above 20 dB was achieved at a constant linear velocity of 19 m/s. Carrier-noise ratio (CNR) kept above 46 dB when the recording frequency reaches 21 MHz. The SLL phase change optical disc demonstrates a better recording performance than the Ge1Sb2Te4 and Ge1Sb4Te7 discs in terms of CNR, erasability, and overwrite jitter.

  2. Dislocation-templated amorphization of Ge2Sb2Te5 nanowires under electric pulses: A theoretical model

    Science.gov (United States)

    Ji, Xiang-Ying; Feng, Xi-Qiao

    2013-06-01

    Owing to their unique phase change property, GeSbTe alloys hold promise for applications as a candidate material for nonvolatile electronic data storage. In this paper, we theoretically investigate the dislocation mechanisms underlying the phase change phenomenon of GeSbTe alloys under electric pulses. On the basis of the recent experiments by Nam et al. (Science 336, 1561-1566 (2012)), a theoretical model is presented to rationalize the dislocation-templated amorphization process under the action of electric pulses. The physical mechanisms of the nucleation, movement, and multiplication of dislocations in the electric field are analyzed. Using the model, the evolutions of temperature and dislocation density in a Ge2Sb2Te5 nanowire under electric pulses are computed and the critical voltage of amorphization is predicted.

  3. Theoretical study of the reactions M(+)+CH(3)F (M=Ge, As, Se, Sb).

    Science.gov (United States)

    Méndez, Oscar; Colmenares, Fernando

    2010-06-21

    CASSCF-MRMP2 calculations have been carried out to analyze the reactions of the methyl fluoride molecule with the atomic ions Ge(+), As(+), Se(+) and Sb(+). For these interactions, potential energy curves for the low-lying electronic states were calculated for different approaching modes of the fragments. Particularly, those channels leading to C-H and C--F oxidative addition products, H(2)FC-M-H(+) and H(3)C-M-F(+), respectively were explored, as well as the paths which evolve to the abstraction (M-F(+)+CH(3)) and the elimination (CH(2)M(+)+HF) asymptotes. For the reaction Ge(+)+CH(3)F the only favorable channel leads to fluorine abstraction by the ion. As(+) and Sb(+) can react with CH(3)F along pathways yielding stable addition products. However, a viable path joining the oxidative addition product H(3)C-M-F(+) with the elimination asymptote CH(2)M(+)+HF was found for the reaction of the fluorocarbon compound with As(+). No favorable channels were detected for the interaction of fluoromethane with Se(+). The results discussed herein allow rationalizing some of the experimental data found for these interactions through gas-phase mass spectrometry.

  4. Effect of electrical field on crystallization and ferroelectric properties of Ge:Sb:Te films

    Energy Technology Data Exchange (ETDEWEB)

    Gervacio Arciniega, J.J.; Prokhorov, E.; Espinoza Beltran, F.J.; Trapaga Martinez, L.G. [CINVESTAV, Unidad Queretaro (Mexico); Gonzalez-Hernandez, J. [Centro de Investigacion en Materiales Avanzados, S.C. and Laboratorio Nacional de Nanotecnologia, Chihuahua (Mexico)

    2011-11-15

    In this work impedance spectroscopy has been used to investigate of the NaCl type-hexagonal transition in stoichiometric Ge{sub 2}Sb{sub 2}Te{sub 5} and in non-stoichiometric (Ge{sub 24}Sb{sub 15}Te{sub 61}) films. The temperature dependence of capacitance in all films shows an abrupt change (about 4-6 times) at the temperature corresponding to the end of the NaCl type-hexagonal transition. Additional, impedance measurements were carried out in films which have been crystallized with an external DC electric field. Comparing the results in the films crystallized with and without the external electric field, it is observed that in films crystallized with an external electric field, the capacitance increases during the NaCl type-hexagonal transition for about 9-15 times and that the piezoresponse force microscopy measurements have shown ferroelectric domains in the NaCl type phase. External electrical field changes significantly the onset of amorphous-NaCl type crystallization temperature which could be related with an increase in atomic diffusion, promoting the growth of the crystalline phase. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Mapping of GeSbTe Thin Film Electrical Properties with Conductive AFM

    Science.gov (United States)

    Brocious, Jordan; Inglefield, Colin; Bobela, David; Herring, Thomas; Taylor, P. Craig

    2007-10-01

    The phase-change material system GeSbTe (GST) is currently used for optical data storage, however many details of the mechanism governing the phase change are not understood. GST's optical properties and electrical conductivities differ between the amorphous and crystalline phases. For instance, the electrical conductivity in the amorphous phase can be ˜10^3 times smaller than electrical conductivity in the crystalline phase. Thin films of Ge2Sb2Te5 and other alloys were created by a RF sputtering technique, which is known to produce amorphous samples. Crystalline regions were created after growth by localized laser heating. We characterized these films with Conductive Atomic Force Microscopy, which provides physical and electrical topography images. From this characterization we have identified sparse ˜100 nm highly conductive regions in the overall low-conductivity amorphous material. Although the laser treatment does not result in a uniformly conductive film, conductive regions in the treated material are significantly denser and larger.

  6. Impact of defect occupation on conduction in amorphous Ge2Sb2Te5

    Science.gov (United States)

    Kaes, Matthias; Salinga, Martin

    2016-08-01

    Storage concepts employing the resistance of phase-change memory (PRAM) have matured in recent years. Attempts to model the conduction in the amorphous state of phase-change materials dominating the resistance of PRAM devices commonly invoke a connection to the electronic density-of-states (DoS) of the active material in form of a “distance between trap states s”. Here, we point out that s depends on the occupation of defects and hence on temperature. To verify this, we numerically study how the occupation in the DoS of Ge2Sb2Te5 is affected by changes of temperature and illumination. Employing a charge-transport model based on the Poole-Frenkel effect, we correlate these changes to the field- and temperature-dependent current-voltage characteristics of lateral devices of amorphous Ge2Sb2Te5, measured in darkness and under illumination. In agreement with our calculations, we find a pronounced temperature-dependence of s. As the device-current depends exponentially on the value of s, accounting for its temperature-dependence has profound impact on device modeling.

  7. Crystallisation kinetics and optical properties of Ge sub 2 Sb sub 2 Te sub 5

    CERN Document Server

    Ruitenberg, G

    2001-01-01

    systems. E sub p , DELTA and GAMMA were determined before and after crystallisation of amorphous Ge sub 2 Sb sub 2 Te sub 5 films. From the numerical values of these parameters, it was concluded that the change in the reflectivity upon crystallisation is primarily due to the change in DELTA. The change in the co-ordination of nearest neighbours upon crystallisation was investigated. The topological co-ordination was found to be very similar in both phases. The change in the optical properties is thought to be due to the change in chemical order of the nearest neighbours. This thesis reports on the work carried out by the on the crystallisation kinetics and optical properties of thin amorphous Ge sub 2 Sb sub 2 Te sub 5 films. This study is prompted by the application of these films in optical phase change recording media. The work is partly theoretical and partly experimental in nature. Starting from the general nucleation and growth theory, it was shown that the Johnson-MehI-Avrami-Kolmogorov (JMAK) equation...

  8. Optical properties of opaline photonic crystals covered by phase-change material Ge$_2$Sb$_2$Te$_5$

    CERN Document Server

    Dyakov, Sergey A; Voronov, Mikhail M; Yakovlev, Sergey A; Pevtsov, Alexander B; Akimov, Ilya A; Tikhodeev, Sergei G

    2016-01-01

    Reflection spectra from 3D opaline photonic crystals covered with phase-change material Ge$_2$Sb$_2$Te$_5$ are studied for different incident angles of light both experimentally and theoretically. We demonstrate that in presence of Ge$_2$Sb$_2$Te$_5$ chalcogenide capping layer, the reflection spectra have peaks associated with resonant Wood's anomalies. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form. The electromagnetic near-field distributions of incident light at resonant frequencies are calculated.

  9. Chemical Vapor Deposition of GeSbTe Thin Films for Next-Generation Phase Change Memory

    Science.gov (United States)

    Machida, Hideaki; Hamada, Seichi; Horiike, Takafumi; Ishikawa, Masato; Ogura, Atsushi; Ohshita, Yoshio; Ohba, Takayuki

    2010-05-01

    In this paper, we describe chemical vapor deposition (CVD) of GeSbTe (GST) films for fabricating phase change memory. A low-carbon-impurity GST film was deposited by CVD. Film composition and structure varied significantly depending on deposition temperature and pressure. The tendency of composition variation on a TiN substrate was the same as that on a SiO2 substrate. Finally, flat Ge2Sb2Te5 thin films were obtained below 300 °C using tert-butylgermanium, triisopropylantimony and diisopropyltellurium as precursors.

  10. Effects of Ge substitution in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration derived from 125Te NMR

    Science.gov (United States)

    Levin, E. M.

    2016-01-01

    GeTe, a self-doping p -type semiconductor where the high free hole concentration is determined by Ge vacancies is a well-known base for high-efficiency A gxS bxG e50 -2 xT e50 (a tellurium-antimony-germanium-silver series) thermoelectric materials. Here it is shown that the replacement of Ge by Ag in GeTe (a A gxG e50 -xT e50 system) significantly decreases the Seebeck coefficient, whereas the replacement by Sb (S bxG e50 -xT e50 ) increases it. These effects can be attributed to a change in carrier concentration and consistent with 125Te NMR spin-lattice relaxation measurements and NMR signal position, which is mostly dependent on the Knight shift. Opposite changes in carrier concentration in A gxG e50 -xT e50 and S bxG e50 -xT e50 can be explained by different valence electron configurations of Ag and Sb compared to that of Ge, which results in a different local electron imbalance and/or in a change in Ge vacancy formation energy and affects the total carrier concentration. Comparison of our data for GeTe, A g2G e48T e50 , and S b2G e48T e50 with those for A g2S b2G e46T e50 shows that the effects from Ag and Sb compensate for each other and supports the formation of [Ag +Sb ] atomic pairs suggested earlier based on theoretical calculations.

  11. Influence of the Composition on the Thermoelectric and Electro-physical Properties of Ge-Sb-Te Thin Films for Phase Change Memory Application

    Directory of Open Access Journals (Sweden)

    P.I. Lazarenko

    2016-10-01

    Full Text Available Influence of the composition variation along the quasi-binary line GeTe-Sb2Te3 on the thermoelectric and electro-physical properties of thin films was investigated. GST amorphous thin films have high Seebeck coefficients, which drops nearly on the order of magnitude after the crystallization. Temperature dependences of the resistivities were studied, and it was determined that crystallization temperature increases with moving along the quasi-binary line GeTe-Sb2Te3 from GeSb4Te7 to GeSb2Te4, and then to Ge2Sb2Te5, while the phase transition temperature range decreases. Current-voltage characteristics of amorphous thin films have three voltage ranges with different dependencies due to the different mechanisms of charge carrier transport.

  12. Improvement of Electrical Properties of the Ge2Sb2Te5 Film by Doping Si for Phase-Change Random Access Memory

    Institute of Scientific and Technical Information of China (English)

    QIAO Bao-Wei; FENG Jie; LAI Yun-Feng; LING Yun; LIN Yin-Yin; TANG Ting-Ao; CAI Bing-Chu; CHEN Bomy

    2006-01-01

    Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phasetransition temperature from face-centred-cubic (fcc) phase to hexagonal (hex) phase. The resistivity of the Ge2Sb2Te5 film shows a significant increase with the Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460℃ annealing increases from 1 to 11mΩ·cm and dynamic resistance increase from 64 to 99Ω compared to the undoped Ge2Sb2Te5 film. This is very helpful to writing current reduction of phase-change random access memory.

  13. Mechanism of GeSbTe phase change materials: an ab initio molecular dynamics study

    Science.gov (United States)

    Raty, Jean-Yves; Otjacques, Céline; Gaspard, Jean-Pierre; Bichara, Christophe

    2008-03-01

    Among phase change materials, Ge2Sb2Te5 (225) is one of the most successfully used in applications. Accepted models are based on EXAFS spectra and suppose a complete reorganization of bonds during amorphization, with Ge changing from sixfold to tetrahedral coordination. We perform ab initio MD simulations of the (225), (124) and (415) liquid alloys. We show that the crystalline, liquid and amorphous structure of these systems are similar, with very little sp3 hybridization around Ge atoms and a majority of p-sigma bonds. Using a set of quenched liquid configurations we reproduce the EXAFS measurements on the (225) composition and explain how the static Debye Waller factor due to the vacancies in the crystal phase leads to a cancellation of individual neighbors contribution to the EXAFS signal while in the amorphous, a larger coherence occurs, enhancing the EXAFS signal. The computed electrical conductivities of the three phases (cubic solid, liquid and amorphous) prove to be very different, accordingly with the experiment.

  14. Controlling Lateral Fano Interference Optical Force with Au-Ge2Sb2Te5 Hybrid Nanostructure

    DEFF Research Database (Denmark)

    Cao, Tun; Bao, Jiaxin; Mao, Libang;

    2016-01-01

    We numerically demonstrate that a pronounced dipole-quadrupole (DQ) Fano resonance (FR) induced lateral force can be exerted on a dielectric particle 80 nm in radius (R-sphere = 80 nm) that is placed 5 nm above an asymmetric bow-tie nanoantenna array based on Au/Ge2Sb2Te5 dual layers. The DQ-FR-i...

  15. Characteristics of Sn-Doped Ge2Sb2Te5 Films Used for Phase-Change Memory

    Institute of Scientific and Technical Information of China (English)

    XU Cheng; LIU Bo; SONG Zhi-Tang; FENG Song-Lin; CHEN Bomy

    2005-01-01

    @@ Sn-doped Ge2Sb2 Te5 thin films deposited on Si(100)/SiO2 substrates by rf magnetron sputtering are investigatedby a differential scanning calorimeter, x-ray diffraction and sheet resistance measurement. The crystallizationtemperatures of the 3.58 at. %, 6.92 at. % and 10.04 at. % Sn-doped Ge2Sb2 Te5 thin films have decreases of 5.3,6.1 and 0.9 ℃, respectively, which is beneficial to reduce the switching current for the amorphous-to-crystallinephase transition. Due to Sn-doping, the sheet resistance of crystalline Ge2Sb2 Te5 thin films increases about 2-10times, which may be useful to reduce the switching current for the amorphous-to-crystalline phase change. Inaddition, an obvious decreasing dispersibility for the sheet resistance of Sn-doped Ge2Sb2 Te5 thin films in thecrystalline state has been observed, which can play an important role in minimizing resistance difference for thephase-change memory cell element arrays.

  16. Low temperature epitaxy of Ge-Sb-Te films on BaF{sub 2} (111) by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Thelander, E., E-mail: erik.thelander@iom-leipzig.de; Gerlach, J. W.; Ross, U.; Lotnyk, A.; Rauschenbach, B. [Leibniz-Institut für Oberflächenmodifizierung e.V., Leipzig 04318 (Germany)

    2014-12-01

    Pulsed laser deposition was employed to deposit epitaxial Ge{sub 2}Sb{sub 2}Te{sub 5}-layers on the (111) plane of BaF{sub 2} single crystal substrates. X-ray diffraction measurements show a process temperature window for epitaxial growth between 85 °C and 295 °C. No crystalline growth is observed for lower temperatures, whereas higher temperatures lead to strong desorption of the film constituents. The films are of hexagonal structure with lattice parameters consistent with existing models. X-ray pole figure measurements reveal that the films grow with one single out-of-plane crystal orientation, but rotational twin domains are present. The out-of-plane epitaxial relationship is determined to be Ge{sub 2}Sb{sub 2}Te{sub 5}(0001) || BaF{sub 2}(111), whereas the in-plane relationship is characterized by two directions, i.e., Ge{sub 2}Sb{sub 2}Te{sub 5} [-12-10] || BaF{sub 2}[1-10] and Ge{sub 2}Sb{sub 2}Te{sub 5}[1-210] || BaF{sub 2}[1-10]. Aberration-corrected high-resolution scanning transmission electron microscopy was used to resolve the local atomic structure and confirm the hexagonal structure of the films.

  17. Real-Time Growth Control of Ge-Sb-Te Multilayer Film as Optical Recording Media by In Situ Ellipsometry

    Science.gov (United States)

    An, Sung Hyuck; Kim, Jong Hyouk; Li, Xuezhe; Kim, Sang Jun; Kim, Sang Youl

    2004-09-01

    Using an in situ ellipsometer, we monitored the thin film growth curve of optical recording media in real time. Utilizing the complex refractive indices of Ge2Sb2Te5 and ZnS-SiO2 obtained from the analysis of spectroscopic ellipsometry data, we calculated the growth curves of ellipsometric constants vs thickness. By comparing the calculated growth curve of ellipsometric constants with the measured one, and by analyzing the effect of the density variation of the Ge2Sb2Te5 recording layer on ellipsometric constants, we precisely monitored the growth rate of Ge2Sb2Te5 and ZnS-SiO2 films, respectively, and eventually controlled the whole growth process of a multilayer sample made of Ge2Sb2Te5 and ZnS-SiO2 films. The accurate thickness control using in situ ellipsometry was verified through the analysis of the deposited multilayer sample using an ex situ spectroscopic ellipsometer.

  18. Controlling Lateral Fano Interference Optical Force with Au-Ge2Sb2Te5 Hybrid Nanostructure

    DEFF Research Database (Denmark)

    Cao, Tun; Bao, Jiaxin; Mao, Libang

    2016-01-01

    We numerically demonstrate that a pronounced dipole-quadrupole (DQ) Fano resonance (FR) induced lateral force can be exerted on a dielectric particle 80 nm in radius (R-sphere = 80 nm) that is placed 5 nm above an asymmetric bow-tie nanoantenna array based on Au/Ge2Sb2Te5 dual layers. The DQ-FR-i...

  19. Temperature-driven topological quantum phase transitions in a phase-change material Ge2Sb2Te5

    Science.gov (United States)

    Eremeev, S. V.; Rusinov, I. P.; Echenique, P. M.; Chulkov, E. V.

    2016-12-01

    The Ge2Sb2Te5 is a phase-change material widely used in optical memory devices and is a leading candidate for next generation non-volatile random access memory devices which are key elements of various electronics and portable systems. Despite the compound is under intense investigation its electronic structure is currently not fully understood. The present work sheds new light on the electronic structure of the Ge2Sb2Te5 crystalline phases. We demonstrate by predicting from first-principles calculations that stable crystal structures of Ge2Sb2Te5 possess different topological quantum phases: a topological insulator phase is realized in low-temperature structure and Weyl semimetal phase is a characteristic of the high-temperature structure. Since the structural phase transitions are caused by the temperature the switching between different topologically non-trivial phases can be driven by variation of the temperature. The obtained results reveal the rich physics of the Ge2Sb2Te5 compound and open previously unexplored possibility for spintronics applications of this material, substantially expanding its application potential.

  20. Disorder-induced structural transitions in topological insulating Ge-Sb-Te compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeongwoo; Jhi, Seung-Hoon, E-mail: jhish@postech.ac.kr [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2015-05-21

    The mechanism for the fast switching between amorphous, metastable, and crystalline structures in chalcogenide phase-change materials has been a long-standing puzzle. Based on first-principles calculations, we study the atomic and electronic properties of metastable Ge{sub 2}Sb{sub 2}Te{sub 5} and investigate the atomic disorder to understand the transition between crystalline hexagonal and cubic structures. In addition, we study the topological insulating property embedded in these compounds and its evolution upon structural changes and atomic disorder. We also discuss the role of the surface-like states arising from the topological insulating property in the metal-insulator transition observed in the hexagonal structure.

  1. Photonic-crystal switch divider based on Ge2Sb2Te5 thin films.

    Science.gov (United States)

    Ma, Beijiao; Zhang, Peiqing; Wang, Hui; Zhang, Tengyu; Zeng, Jianghui; Zhang, Qian; Wang, Guoxiang; Xu, Peipeng; Zhang, Wei; Dai, Shixun

    2016-11-10

    A three-port phase-change photonic-crystal switch divider based on Ge2Sb2Te5 chalcogenide thin film was proposed. The chalcogenide material used was determined to have a high refractive index and fast phase-change speed by using laser radiation. The structure with a T-junction cavity was used to achieve three switch functions: switching "ON" in only one output port, switching "OFF" in both output ports, and dividing signals into two output ports. The transmission properties of the designed device at 2.0 μm were studied by the finite difference time domain method, which showed that the switch divider can achieve very high switching efficiency by optimizing T-junction cavity parameters. The scaling laws of photonic crystals revealed that the operating wavelength of the designed structure can be easily extended to another wavelength in the midinfrared region.

  2. Metal - Insulator Transition Driven by Vacancy Ordering in GeSbTe Phase Change Materials

    Science.gov (United States)

    Bragaglia, Valeria; Arciprete, Fabrizio; Zhang, Wei; Mio, Antonio Massimiliano; Zallo, Eugenio; Perumal, Karthick; Giussani, Alessandro; Cecchi, Stefano; Boschker, Jos Emiel; Riechert, Henning; Privitera, Stefania; Rimini, Emanuele; Mazzarello, Riccardo; Calarco, Raffaella

    2016-04-01

    Phase Change Materials (PCMs) are unique compounds employed in non-volatile random access memory thanks to the rapid and reversible transformation between the amorphous and crystalline state that display large differences in electrical and optical properties. In addition to the amorphous-to-crystalline transition, experimental results on polycrystalline GeSbTe alloys (GST) films evidenced a Metal-Insulator Transition (MIT) attributed to disorder in the crystalline phase. Here we report on a fundamental advance in the fabrication of GST with out-of-plane stacking of ordered vacancy layers by means of three distinct methods: Molecular Beam Epitaxy, thermal annealing and application of femtosecond laser pulses. We assess the degree of vacancy ordering and explicitly correlate it with the MIT. We further tune the ordering in a controlled fashion attaining a large range of resistivity. Employing ordered GST might allow the realization of cells with larger programming windows.

  3. Fano resonant Ge2Sb2Te5 nanoparticles realize switchable lateral optical force

    Science.gov (United States)

    Cao, Tun; Mao, Libang; Gao, Dongliang; Ding, Weiqiang; Qiu, Cheng-Wei

    2016-03-01

    Sophisticated optical micromanipulation of small biomolecules usually relies on complex light, e.g., structured light, highly non-paraxial light, or chiral light. One emerging technique is to employ chiral light to drive the chiral nanoparticle along the direction perpendicular to the propagation of the light, i.e., the lateral optical force. Here, we theoretically study the lateral optical force exerted by a entirely Gaussian beam. For the very first time we demonstrate that the Fano resonances (FRs) of the Ge2Sb2Te5 (GST) phase-change nanoparticles encapsulated with Au shells could enable a conventional Gaussian laser to exert a lateral force on such a dielectric GST nanoparticle, attributed to the strongly asymmetric energy flow around the sphere in the dipole-quadrupole FRs. More interestingly, the direction of this lateral force could be reversible during the state transition (i.e., from amorphous to crystalline). By bonding small biomolecules to the outer surface of the phase-change nanoparticle, the particle behaves as a direction-selective vehicle to transport biomolecules along opposite directions, at pre-assessed states of the Ge2Sb2Te5 core correspondingly. Importantly, the origin of the reversal of the lateral optical force is further unveiled by the optical singularity of the Poynting vector. Our mechanism of tailoring the FRs of phase-change nanoparticles, not just limited to GST, may bring a new twist to optical micromanipulation and biomedical applications.Sophisticated optical micromanipulation of small biomolecules usually relies on complex light, e.g., structured light, highly non-paraxial light, or chiral light. One emerging technique is to employ chiral light to drive the chiral nanoparticle along the direction perpendicular to the propagation of the light, i.e., the lateral optical force. Here, we theoretically study the lateral optical force exerted by a entirely Gaussian beam. For the very first time we demonstrate that the Fano resonances

  4. Ultrafast terahertz-induced response of GeSbTe phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Michael J. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Zalden, Peter [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Chen, Frank [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Weems, Ben [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Chatzakis, Ioannis [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Xiong, Feng; Jeyasingh, Rakesh; Pop, Eric; Philip Wong, H.-S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Hoffmann, Matthias C. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Wuttig, Matthias [I. Physikalisches Institut, RWTH Aachen University, 52056 Aachen (Germany); JARA–Fundamentals of Information Technology, RWTH Aachen University, 52056 Aachen (Germany); Lindenberg, Aaron M., E-mail: aaronl@stanford.edu [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2014-06-23

    The time-resolved ultrafast electric field-driven response of crystalline and amorphous GeSbTe films has been measured all-optically, pumping with single-cycle terahertz pulses as a means of biasing phase-change materials on a sub-picosecond time-scale. Utilizing the near-band-gap transmission as a probe of the electronic and structural response below the switching threshold, we observe a field-induced heating of the carrier system and resolve the picosecond-time-scale energy relaxation processes and their dependence on the sample annealing condition in the crystalline phase. In the amorphous phase, an instantaneous electroabsorption response is observed, quadratic in the terahertz field, followed by field-driven lattice heating, with Ohmic behavior up to 200 kV/cm.

  5. Ultrafast terahertz-induced response of GeSbTe phase-change materials

    Science.gov (United States)

    Shu, Michael J.; Zalden, Peter; Chen, Frank; Weems, Ben; Chatzakis, Ioannis; Xiong, Feng; Jeyasingh, Rakesh; Hoffmann, Matthias C.; Pop, Eric; Philip Wong, H.-S.; Wuttig, Matthias; Lindenberg, Aaron M.

    2014-06-01

    The time-resolved ultrafast electric field-driven response of crystalline and amorphous GeSbTe films has been measured all-optically, pumping with single-cycle terahertz pulses as a means of biasing phase-change materials on a sub-picosecond time-scale. Utilizing the near-band-gap transmission as a probe of the electronic and structural response below the switching threshold, we observe a field-induced heating of the carrier system and resolve the picosecond-time-scale energy relaxation processes and their dependence on the sample annealing condition in the crystalline phase. In the amorphous phase, an instantaneous electroabsorption response is observed, quadratic in the terahertz field, followed by field-driven lattice heating, with Ohmic behavior up to 200 kV/cm.

  6. Structural change upon annealing of amorphous GeSbTe grown on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Bragaglia, V., E-mail: bragaglia@pdi-berlin.de; Jenichen, B.; Giussani, A.; Perumal, K.; Riechert, H.; Calarco, R. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2014-08-07

    The structural change upon annealing of an amorphous GeSbTe (GST) film deposited by molecular beam epitaxy on a Si(111) substrate is studied by means of X-ray diffraction (XRD), X-ray reflectivity (XRR), and atomic force microscopy (AFM). XRD profiles reveal that both metastable cubic and stable hexagonal phases are obtained with a single out-of-plane orientation. XRR study shows a density increase and consequent thickness decrease upon annealing, in accordance with literature. From both, the XRD and the AFM study, it emerges that the crystalline substrate acts as a template for the film, favoring the crystallization of the amorphous GST into the [111] oriented metastable cubic phase, and the latter turns into the [0001] stable hexagonal phase for higher annealing temperature.

  7. Parallel nanostructuring of GeSbTe film with particle mask

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.B.; Hong, M.H.; Wang, Q.F.; Chong, T.C. [Data Storage Institute, DSI Building, 5 Engineering Drive 1, 117608, Singapore (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 119260, Singapore (Singapore); Luk' yanchuk, B.S.; Huang, S.M.; Shi, L.P. [Data Storage Institute, DSI Building, 5 Engineering Drive 1, 117608, Singapore (Singapore)

    2004-09-01

    Parallel nanostructuring of a GeSbTe film may significantly improve the recording performance in data storage. In this paper, a method that permits direct and massively parallel nanopatterning of the substrate surface by laser irradiation is investigated. Polystyrene spherical particles were deposited on the surface in a monolayer array by self-assembly. The array was then irradiated with a 248-nm KrF laser. A sub-micron nanodent array can be obtained after single-pulse irradiation. These nanodents change their shapes at different laser energies. The optical near-field distribution around the particles was calculated according to the exact solution of the light-scattering problem. The influence of the presence of the substrate on the optical near field was also studied. The mechanisms for the generation of the nanodent structures are discussed. (orig.)

  8. Structural change upon annealing of amorphous GeSbTe grown on Si(111)

    Science.gov (United States)

    Bragaglia, V.; Jenichen, B.; Giussani, A.; Perumal, K.; Riechert, H.; Calarco, R.

    2014-08-01

    The structural change upon annealing of an amorphous GeSbTe (GST) film deposited by molecular beam epitaxy on a Si(111) substrate is studied by means of X-ray diffraction (XRD), X-ray reflectivity (XRR), and atomic force microscopy (AFM). XRD profiles reveal that both metastable cubic and stable hexagonal phases are obtained with a single out-of-plane orientation. XRR study shows a density increase and consequent thickness decrease upon annealing, in accordance with literature. From both, the XRD and the AFM study, it emerges that the crystalline substrate acts as a template for the film, favoring the crystallization of the amorphous GST into the [111] oriented metastable cubic phase, and the latter turns into the [0001] stable hexagonal phase for higher annealing temperature.

  9. Fabrication and characterization of bare Ge-Sb-Se chalcogenide glass fiber taper

    Science.gov (United States)

    Luo, Baohua; Wang, Yingying; Sun, Ya'nan; Dai, Shixun; Yang, Peilong; Zhang, Peiqing; Wang, Xunsi; Chen, Feifei; Wang, Rongping

    2017-01-01

    In this work, Ge15Sb20Se65 bare glass fiber with a diameter of 500 μm was fabricated, and then tapered with different tapering parameters. The analysis of Raman and energy dispersive X-ray spectra (EDS) indicated that, a slight change in the chemical composition of the glass, fiber and tapering fiber has negligible effect on the glass structure. It was found that, the waist diameter decreases exponentially with increasing tapering length and speed, and high quality taper fiber with the cone diameter of 2.65 μm can be achieved under the optimal tapering conditions. Finally, the simulated and experimental results of the output transmission under different waist length and taper ratio show that the transmission decreases with increasing waist length and taper ratio.

  10. Investigation of basic thermal behavior of a-Te-Se-Ge-Sb glassy system

    Science.gov (United States)

    Nidhi, Anant Vidya; Modgil, Vivek; Chaudhary, Shobhna; Kumar, Prashant; Rangra, V. S.

    2015-05-01

    The bulk material Te9Se72Ge19-xSbx (8≤x≤12) has been prepared by melt quenching technique. The amorphous and glassy nature has been confirmed using XRD and DSC analysis respectively. The thermal kinetics of material is studied through differential scanning calorimetry under non-isothermal condition at constant heating rate. The thermal behavior, activation energy of glass transition and crystallization has been determined using appropriate models. The thermal parameter accounting for thermal stability and quality has been explored along with compositional dependence. A stable glass with high value of Tg and quality has been formed. The mild phase separation has been observed in the material at x=8, 9 and this phase separation dissolves when the Sb content further increases in glassy matrix.

  11. Electronic structure of GaSb/GaAs and Si/Ge quantum dots

    CERN Document Server

    North, S M

    2001-01-01

    There are significant differences between experiment and theoretical calculations of the electronic structure of GaSb/GaAs self-assembled quantum dots. Using a multi-band effective mass approximation it is shown that the influence of size and geometry of quantum dots has little or no effect in determining the hydrostatic strain. Furthermore, the valence-band ground state energies of the quantum dots studied are surprisingly consistent. This apparent paradox attributed to the influence of biaxial strain in shaping the heavy-hole and light-hole potentials. Consequently, it is shown that a simple, hydrostatically derived potential is insufficient to accurately describe the electronic structure of such quantum dots. In addition, using the latest experimental results measuring the conduction-band offset, it has been shown that much better experimental contact may be achieved for the magnitude of the transition energies derived compared to theoretically derived transition energies. The transition energies of Si/Ge ...

  12. Crystal structure, microstructure, and thermoelectric properties of GeSb{sub 6}Te{sub 10} prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kosuga, Atsuko, E-mail: a-kosuga@21c.osakafu-u.ac.jp [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Nakai, Kazuki [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Matsuzawa, Mie; Fujii, Yousuke [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Funahashi, Ryoji [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577 (Japan); Tachizawa, Takuya; Kubota, Yoshiki [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Kifune, Kouichi [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Faculty of Engineering, Hiroshima Institute of Technology, Hiroshima 731-5193 (Japan)

    2015-01-05

    Highlights: • Spark plasma sintering effects on GeSb{sub 6}Te{sub 10} properties are described. • Sintered GeSb{sub 6}Te{sub 10} contains homologous GeSb{sub 6}Te{sub 10} and Sb{sub 2}Te{sub 3} tetradymite structures. • Spark plasma sintering causes elemental compositional deviations from GeSb{sub 6}Te{sub 10}. • SPS-consolidated and melt-prepared samples have similar ZT{sub max} values. • Spark plasma sintering significantly changes crystal structure and microstructure. - Abstract: We report the effects of spark plasma sintering (SPS) and subsequent annealing on the crystal structure, microstructure, and thermoelectric properties of polycrystalline GeSb{sub 6}Te{sub 10}. GeSb{sub 6}Te{sub 10} consolidated using SPS consisted of a mixture of GeSb{sub 6}Te{sub 10}-type homologous and Sb{sub 2}Te{sub 3}-type tetradymite structures, whereas the sample prepared by melting had a single homologous structure. SPS produced small amounts of Ge-rich precipitates with a few micrometers in size. Even excluding these precipitates, the elemental compositional deviation from the nominal composition was wider than that for the sample prepared by melting. This implies that SPS promoted atomic diffusion and rearrangement of elements, leading to a substantial change in the crystal structure and elemental distribution of GeSb{sub 6}Te{sub 10}. SPS improved the power factor but also increased the thermal conductivity, as a result of the increased electrical conductivity, yielding a maximum dimensionless figure of merit, ZT{sub max}, of 0.33 at 710 K, which is similar to the value for the sample prepared by melting (0.39 at 710 K)

  13. Avalanche atomic switching in strain engineered Sb2Te3–GeTe interfacial phase-change memory cells

    Science.gov (United States)

    Zhou, Xilin; Behera, Jitendra K.; Lv, Shilong; Wu, Liangcai; Song, Zhitang; Simpson, Robert E.

    2017-09-01

    By confining phase transitions to the nanoscale interface between two different crystals, interfacial phase change memory heterostructures represent the state of the art for energy efficient data storage. We present the effect of strain engineering on the electrical switching performance of the {{Sb}}2{{Te}}3–GeTe superlattice van der Waals devices. Multiple Ge atoms switching through a two-dimensional Te layer reduces the activation barrier for further atoms to switch; an effect that can be enhanced by biaxial strain. The out-of-plane phonon mode of the GeTe crystal remains active in the superlattice heterostructures. The large in-plane biaxial strain imposed by the {{Sb}}2{{Te}}3 layers on the GeTe layers substantially improves the switching speed, reset energy, and cyclability of the superlattice memory devices. Moreover, carefully controlling residual stress in the layers of {{Sb}}2{{Te}}3–GeTe interfacial phase change memories provides a new degree of freedom to design the properties of functional superlattice structures for memory and photonics applications.

  14. Elastic phases of Ge(x)Sb(x)Se(100-2x) ternary glasses driven by topology.

    Science.gov (United States)

    Gunasekera, Kapila; Boolchand, P; Micoulaut, M

    2013-08-29

    Topology offers a practical set of computational tools to accurately predict certain physical and chemical properties of materials including transformations under deformation. In network glasses with increased cross-linking three generic elastic phases are observed. We examine ternary Ge(x)Sb(x)Se(100-2x) glasses in Raman scattering, modulated DSC and volumetric measurements, and observe the rigidity transition, x = x(c)(1) = 14.9% that separates the flexible phase from the Intermediate phase, and the stress transition, x = x(c)(2) = 17.5% that separate the intermediate phase from the stressed rigid one. Raman scattering provides evidence of the structural motifs populated in these networks. Using size increasing cluster agglomeration, we have calculated the rigidity and stress transitions to occur near x(c)(1)(t) = 15.2% and x(c)(2)(t) = 17.5%, respectively. Theory predicts and experiments confirm that these two transitions will coalesce if edge-sharing Ge-tetrahedral motifs were absent in the structure, a circumstance that prevails in the Ge-deficient Ge7Sb(x)Se(93-x) ternary, underscoring the central role played by topology in network glasses. We have constructed a global elastic phase diagram of the Ge-Sb-Se ternary that provides a roadmap to network functionality. In this diagram, regions labeled A, B, and C comprise networks that are flexible, rigid but unstressed, and stressed-rigid, respectively.

  15. Effect of Si-Implantation on the Structure and Resistance of Ge2Sb2Te5%硅离子注入对Ge2Sb2Te5结构和电阻的影响

    Institute of Scientific and Technical Information of China (English)

    刘波; 宋志棠; 封松林; Chen Bomy

    2006-01-01

    采用磁控射频溅射法制备了Ge2Sb2Te5薄膜,利用离子注入法研究了硅掺杂对薄膜结构和电阻性能的影响.研究发现,由于硅的掺杂,Ge2Sb2Te5薄膜的结构不仅保留了原有的面心立方低温晶相和六方高温晶相,而且出现了菱形六面体的Sb2Te3晶相;掺杂硅后,Ge2Sb2Te5薄膜的电阻有较大变化,晶态电阻的提高有利于降低非晶化相变过程的操作电流,薄膜电阻-温度稳定性的改善可保证有较宽的操作电流波动范围.

  16. Silicon doping effect on the crystallization behavior of Ge{sub 2}Sb{sub 2}Te{sub 5} film

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yifan; Xu, Ling; Chen, Jing; Zhang, Rui; Su, Weining; Yu, Yao; Ma, Zhongyuan; Xu, Jun [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, Nanjing University (China)

    2013-10-15

    Pure Ge{sub 2}Sb{sub 2}Te{sub 5} thin films and Si-doped Ge{sub 2}Sb{sub 2}Te{sub 5} thin films were deposited by electron beam evaporation method. The property of Si-doped Ge{sub 2}Sb{sub 2}Te{sub 5} films are compared with that of pure Ge{sub 2}Sb{sub 2}Te{sub 5} films. Through in situ resistance measurement and I-V characteristic tests, an improvement of amorphous stability and an increase of crystalline resistivity are observed. The phase-separation phenomenon is observed in TEM pictures and a distinct decrease of crystal grain size in Si-doped Ge{sub 2}Sb{sub 2}Te{sub 5} thin film can be seen in HRTEM pictures. A blueshift and broadening of peaks after Si doping in Raman spectra are found and from absorption spectra, the broadening of crystalline optical bandgap in Si-doped Ge{sub 2}Sb{sub 2}Te{sub 5} thin film is proved. Finally, the behavior of doped Si atoms is proposed to explain the effect of Si doping in Ge{sub 2}Sb{sub 2}Te{sub 5} thin film. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Ag掺杂对Ge2 Sb2 Te5结晶行为的影响%Crystallization behavior of phase change material Ge2 Sb2 Te5 doped with Ag

    Institute of Scientific and Technical Information of China (English)

    张滔; 郑坤; 张斌; 邵瑞文; 韩晓东; 张泽

    2014-01-01

    通过磁控溅射仪制备了Ge2 Sb2 Te5( GST)和Ag10�6( GST)89�4薄膜,利用X射线衍射( XRD)、电阻-温度( R-T)测试、透射电子显微学以及径向分布函数(RDF)等方法对比研究了GST和Ag10�6(GST)89�4的结晶过程和微观结构及其演化的差异。发现掺Ag的薄膜非晶态、晶态电阻均比GST更高,而且结晶过程只有非晶相到面心立方相( fcc)的转变,没有出现GST的非晶到fcc再到六方相( hcp)的过程,XRD分析进一步证实了这一结果。同时,透射电镜原位加热实验证实了在300℃时,Ag10�6( GST)89�4仍然保持着fcc结构,而GST中已经出现了hcp相。通过统计230℃下时效处理的晶态薄膜的晶粒尺寸,发现Ag10�6( GST)89�4的平均晶粒尺寸小于Ge2 Sb2 Te5薄膜的,这可能是造成其晶态电阻高于GST的主要原因。%Ag-doped Ge2 Sb2 Te5 films have been prepared, and the influence of Ag doping on the crystallization behavior, structure was investigated through X-ray diffraction techniques, electrical resistivity measurement and in situ TEM annealing techniques. The results show that the addition of Ag into GST films could result in an enhancement in electrical resistance compared with Ge2 Sb2 Te5 films. Ag doping can lead to one-step crystallization process from amorphous to single face-centered cubic ( fcc ) phase without any other crystalline phase. HRTEM images show that the grain size in Ag-doped Ge2 Sb2 Te5 films is smaller than that in conventional Ge2 Sb2 Te5 films.

  18. The Role of Anti-Phase Domains in InSb-Based Structures Grown on On-Axis and Off-Axis Ge Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, M. C.; Mishima, T. D.; Santos, M. B. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Hossain, K.; Holland, O. W. [Amethyst Research, Inc., 1405 4th Ave NW, Ardmore, OK 73401 (United States)

    2011-12-26

    Anti-phase domains form in InSb epilayers and InSb/Al{sub 0.20}In{sub 0.80}Sb single quantum wells when grown upon on-axis (001) Ge substrates by molecular beam epitaxy. Domain formation is partially suppressed through growth on Ge substrates with surfaces that are several degrees off the (001) or (211) axis. By using off-axis Ge substrates, room-temperature electron mobilities increased to {approx}60,000 cm{sup 2}/V-s and {approx}14,000 cm{sup 2}/V-s for a 4.0-{mu}m-thick InSb epilayer and a 25-nm InSb quantum well, respectively.

  19. Electrical conductivity and hardness of ternary Ge-In-Sb alloys and calculation of the isothermal section at 300 C

    Energy Technology Data Exchange (ETDEWEB)

    Premovic, Milena; Minic, Dusko; Mitrovica, Kosovska [Pristina Univ., Kosovska Mitrovica (Serbia). Faculty of Technical Science; Manasijevic, Ivana; Zivkovic, Dragana [Belgrade Univ., Bor (Serbia). Dept. of Metallurgical Engineering

    2015-07-01

    This publication presents results of experimental investigation and thermodynamic calculation of the ternary Ge-In-Sb system. Isothermal section of the Ge-In-Sb system at 300 C has been extrapolated using optimized thermodynamic parameters for the constitutive binary systems. Microstructure analysis was carried out by light microscope, scanning electron microscopy with energy dispersive spectrometry and X-ray powder diffraction methods and obtained results were compared with predicted phase equilibria. Hardness of selected alloys annealed at 300 C was measured using Vickers microhardness test and Brinell hardness test. Electrical conductivity of a number of alloys annealed at 300 C was experimentally determined. Good overall agreement between experimental and calculated values was obtained.

  20. Durability of rewritable phase-change Ge$_{X}$Sb$_{Y}$ Te$_{1−X−Y}$ memory devices

    Indian Academy of Sciences (India)

    N Parvathala Reddy; Ch Bapanayya; Rajeev Gupta; S C Agarwal

    2013-06-01

    The bond constraint theory (BCT) dealing with the rigidity caused by bond constraints and the long-range potential fluctuations (LRPF) arising from the defects and heterogeneities in the disordered semiconductors are important for understanding the atomic and electronic properties of amorphous semiconductors. Here, they are applied to the already commercialized Ge$_{X}$Sb$_{Y}$ Te$_{1−X−Y}$ (GST) chalcogenide glasses used in the rewritable phase change memory (PCM) devices. The main concern at present is to improve their ability to withstand a large number of phase change cycles, by choosing the right composition. The two considerations (BCT and LRPF) are briefly described and tested on the most commonly used Ge2Sb2Te5 and the nearby compositions. While these considerations provide significant insight into their atomic and electronic structures, the ansatz linking them with the durability of the PCM devices need to be justified by more work.

  1. Electronic stress tensor analysis of molecules in gas phase of CVD process for GeSbTe alloy

    CERN Document Server

    Nozaki, Hiroo; Ichikawa, Kazuhide; Tachibana, Akitomo

    2015-01-01

    We analyze the electronic structure of molecules which may exist in gas phase of chemical vapor deposition process for GeSbTe alloy using the electronic stress tensor, with special focus on the chemical bonds between Ge, Sb and Te atoms. We find that, from the viewpoint of the electronic stress tensor, they have intermediate properties between alkali metals and hydrocarbon molecules. We also study the correlation between the bond order which is defined based on the electronic stress tensor, and energy-related quantities. We find that the correlation with the bond dissociation energy is not so strong while one with the force constant is very strong. We interpret these results in terms of the energy density on the "Lagrange surface", which is considered to define the boundary surface of atoms in a molecule in the framework of the electronic stress tensor analysis.

  2. Electronic stress tensor analysis of molecules in gas phase of CVD process for GeSbTe alloy.

    Science.gov (United States)

    Nozaki, Hiroo; Ikeda, Yuji; Ichikawa, Kazuhide; Tachibana, Akitomo

    2015-06-15

    We analyze the electronic structure of molecules which may exist in gas phase of chemical vapor deposition process for GeSbTe alloy using the electronic stress tensor, with special focus on the chemical bonds between Ge, Sb, and Te atoms. We find that, from the viewpoint of the electronic stress tensor, they have intermediate properties between alkali metals and hydrocarbon molecules. We also study the correlation between the bond order which is defined based on the electronic stress tensor, and energy-related quantities. We find that the correlation with the bond dissociation energy is not so strong while one with the force constant is very strong. We interpret these results in terms of the energy density on the "Lagrange surface," which is considered to define the boundary surface of atoms in a molecule in the framework of the electronic stress tensor analysis.

  3. A 4F2-cross-point phase change memory using nano-crystalline doped GeSbTe material

    Science.gov (United States)

    Takaura, Norikatsu; Kinoshita, Masaharu; Tai, Mitsuharu; Ohyanagi, Takasumi; Akita, Kenichi; Morikawa, Takahiro

    2015-04-01

    This paper reports on the use of nano-crystalline doped GeSbTe, or nano-GST, to fabricate a cross-point phase change memory with 4F2 cell size and test results obtained for it. We show the characteristics of a poly-Si diode select device with a high on-off ratio and data writing in a 4F2 memory cell array. The advantages of nano-GST over conventional GeSbTe are presented in terms of neighboring disturbance and 4F2 cross-point array formation. The memory cells’ high drivability, low power, and selective write and read performances are demonstrated. The scalability of the diode current density is also presented.

  4. Electronic properties of GeTe and Ag- or Sb-substituted GeTe studied by low-temperature 125Te NMR

    Science.gov (United States)

    Cui, J.; Levin, E. M.; Lee, Y.; Furukawa, Y.

    2016-08-01

    We have carried out 125Te nuclear magnetic resonance (NMR) in a wide temperature range of 1.5-300 K to investigate the electronic properties of Ge50Te50 ,Ag2Ge48Te50 , and Sb2Ge48Te50 from a microscopic point of view. From the temperature dependence of the NMR shift (K ) and nuclear spin lattice relaxation rate (1 /T1 ), we found that two bands contribute to the physical properties of the materials. One band overlaps the Fermi level providing the metallic state where no strong electron correlations are revealed by Korringa analysis. The other band is separated from the Fermi level by an energy gap of Eg/kB˜67 K, which gives rise to semiconductorlike properties. First-principles calculation reveals that the metallic band originates from the Ge vacancy while the semiconductorlike band is related to the fine structure of the density of states near the Fermi level. Low-temperature 125Te NMR data for the materials studied here clearly show that Ag substitution increases hole concentration while Sb substitution decreases it.

  5. Surface diffusion of Sb on Ge(111) investigated by second harmonic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, K.A.

    1992-01-01

    Surface diffusion of Sb on Ge(111) has been measured with the newly-developed technique of second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by second harmonic generation with 5 [mu]m spatial resolution. A Boltzmann-Matano analysis of the concentration profiles yields the coverage dependence of the diffusivity D without parameterization. Experiments were performed at roughly 70% of the bulk melting temperature T[sub m]. In the coverage range of 0 < [theta] < 0.6, the activation energy E[sub diff] remains constant at 47.5 [+-] 1.5 kcal/mol. The corresponding pre-exponential factor decreases from 8.7 [times] 10[sup 3[+-]0.4] to 1.6 [times] 10[sup 2[+-]0.4] cm[sup 2]/sec. The results are explained in terms of a new vacancy model for surface diffusion at high-temperatures. The model accounts semiquantitatively for the large values of E[sub diff] and D[sub o], and suggest that these quantities may be manipulated by bulk doping levels and photon illumination of the surface.

  6. Surface diffusion of Sb on Ge(111) monitored quantitatively with optical second harmonic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, K.A.; Seebauer, E.G. (Department of Chemical Engineering, University of Illinois, Urbana, Illinois 61801 (United States))

    1992-11-01

    Surface diffusion of Sb on Ge(111) has been measured with the newly developed technique of optical second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by surface second harmonic generation with 5 {mu} spatial resolution. A Boltzmann--Matano analysis yields the coverage dependence of the diffusivity {ital D} without parametrization. Experiments were performed at roughly 70% of the bulk melting temperature {ital T}{sub {ital m}}. In the coverage range 0{le}{theta}{le}0.6, the activation energy {ital E}{sub diff} remains constant at 47.5{plus minus}1.5 kcal/mol, but the pre-exponential factor {ital D}{sub 0} decreases from 8.7{times}10{sup 3{plus minus}0.4} to 1.6{times}10{sup 2{plus minus}0.4} cm{sup 2}/s. Both {ital E}{sub diff} and {ital D}{sub 0} are quite large, which is consistent with high-temperature measurements in other systems. The inadequacies of current theories for high-temperature surface diffusion are outlined, and a new vacancy model is proposed for low-coverage diffusion. The model accounts semiquantitatively for the large values of {ital E}{sub diff} and {ital D}{sub 0}, and suggests that these quantities may be manipulated using doping levels and photon illumination. An islanding mechanism is proposed to explain the decrease in {ital D}{sub 0} with {theta}.

  7. Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope

    Science.gov (United States)

    Yang, Fei; Xu, Ling; Zhang, Rui; Geng, Lei; Tong, Liang; Xu, Jun; Su, Weining; Yu, Yao; Ma, Zhongyuan; Chen, Kunji

    2012-10-01

    GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20 °C to 300 °C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase. Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I-V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I-V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I-V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I-V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

  8. Size-dependent and tunable crystallization of GeSbTe phase-change nanoparticles

    Science.gov (United States)

    Chen, Bin; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.

    2016-12-01

    Chalcogenide-based nanostructured phase-change materials (PCMs) are considered promising building blocks for non-volatile memory due to their high write and read speeds, high data-storage density, and low power consumption. Top-down fabrication of PCM nanoparticles (NPs), however, often results in damage and deterioration of their useful properties. Gas-phase condensation based on magnetron sputtering offers an attractive and straightforward solution to continuously down-scale the PCMs into sub-lithographic sizes. Here we unprecedentedly present the size dependence of crystallization for Ge2Sb2Te5 (GST) NPs, whose production is currently highly challenging for chemical synthesis or top-down fabrication. Both amorphous and crystalline NPs have been produced with excellent size and composition control with average diameters varying between 8 and 17 nm. The size-dependent crystallization of these NPs was carefully analyzed through in-situ heating in a transmission electron microscope, where the crystallization temperatures (Tc) decrease when the NPs become smaller. Moreover, methane incorporation has been observed as an effective method to enhance the amorphous phase stability of the NPs. This work therefore elucidates that GST NPs synthesized by gas-phase condensation with tailored properties are promising alternatives in designing phase-change memories constrained by optical lithography limitations.

  9. High temperature electrical resistivity and Seebeck coefficient of Ge2Sb2Te5 thin films

    Science.gov (United States)

    Adnane, L.; Dirisaglik, F.; Cywar, A.; Cil, K.; Zhu, Y.; Lam, C.; Anwar, A. F. M.; Gokirmak, A.; Silva, H.

    2017-09-01

    High-temperature characterization of the thermoelectric properties of chalcogenide Ge2Sb2Te5 (GST) is critical for phase change memory devices, which utilize self-heating to quickly switch between amorphous and crystalline states and experience significant thermoelectric effects. In this work, the electrical resistivity and Seebeck coefficient are measured simultaneously as a function of temperature, from room temperature to 600 °C, on 50 nm and 200 nm GST thin films deposited on silicon dioxide. Multiple heating and cooling cycles with increasingly maximum temperature allow temperature-dependent characterization of the material at each crystalline state; this is in contrast to continuous measurements which return the combined effects of the temperature dependence and changes in the material. The results show p-type conduction (S > 0), linear S(T), and a positive Thomson coefficient (dS/dT) up to melting temperature. The results also reveal an interesting linearity between dS/dT and the conduction activation energy for mixed amorphous-fcc GST, which can be used to estimate one parameter from the other. A percolation model, together with effective medium theory, is adopted to correlate the conductivity of the material with average grain sizes obtained from XRD measurements. XRD diffraction measurements show plane-dependent thermal expansion for the cubic and hexagonal phases.

  10. Structure and Electrical Properties of Ge2Sb2Te5 Thin Film Used for Ovonic Unified Memory

    Institute of Scientific and Technical Information of China (English)

    张挺; 刘波; 夏吉林; 宋志棠; 封松林; 陈宝明

    2004-01-01

    Annealing temperature effects on the structure and electrical resistance of Ge2Sb2 Te5 thin film were studied. The crystallization and melting temperature of the thin film are about 175 ℃ and 610 ℃ respectively. The structure of the as-deposited and the annealed film at different annealing temperatures are identified by the x-ray diffraction method. The thin film changes from an amorphous state to the fcc structure at about 200 ℃, and then changes into the hexagonal close-packed (hcp) structure at about 400 ℃. Electrical resistance of as-deposited thin film reaches as high as 1.7 × 108 Ω/sq. Then it decreases to 1.6 × 104 Ω/sq and 165Ω/sq after the annealing process at 250℃ and 400℃ respectively. The current-voltage curve of the Ge2Sb2Te5 thin film is also investigated.Due to the large resistance difference between the amorphous, the fcc crystalline and the hcp crystalline states,Ge2Sb2 Te5 film may be used to realize multilevel storage for Ovonic unified memory.

  11. Element-resolved atomic structure imaging of rocksalt Ge2Sb2Te5 phase-change material

    Science.gov (United States)

    Zhang, Bin; Zhang, Wei; Shen, Zhenju; Chen, Yongjin; Li, Jixue; Zhang, Shengbai; Zhang, Ze; Wuttig, Matthias; Mazzarello, Riccardo; Ma, Evan; Han, Xiaodong

    2016-05-01

    Disorder-induced electron localization and metal-insulator transitions (MITs) have been a very active research field starting from the seminal paper by Anderson half a century ago. However, pure Anderson insulators are very difficult to identify due to ubiquitous electron-correlation effects. Recently, an MIT has been observed in electrical transport measurements on the crystalline state of phase-change GeSbTe compounds, which appears to be exclusively disorder driven. Subsequent density functional theory simulations have identified vacancy disorder to localize electrons at the Fermi level. Here, we report a direct atomic scale chemical identification experiment on the rocksalt structure obtained upon crystallization of amorphous Ge2Sb2Te5. Our results confirm the two-sublattice structure resolving the distribution of chemical species and demonstrate the existence of atomic disorder on the Ge/Sb/vacancy sublattice. Moreover, we identify a gradual vacancy ordering process upon further annealing. These findings not only provide a structural underpinning of the observed Anderson localization but also have implications for the development of novel multi-level data storage within the crystalline phases.

  12. Super-Resolution Near-Field Disk with Phase-Change Sn-Doped GeSbTe Mask Layer

    Science.gov (United States)

    Lee, Mei Ling; Thong Yong, Kok; Lip Gan, Chee; Hou Ting, Lee; Shi, Lu Ping

    2009-03-01

    A new mask layer of Sn-doped (7 at. %) Ge2Sb2Te5 was developed and used on super-resolution near-field phase-change optical disks (super-RENS). Temperature-dependent reflectivity result showed a reflectivity change at 169 °C with Sn doping into Ge2Sb2Te5. The mask material also showed high thermal stability. Optical study indicated the suitability of the film for use in blue-laser recording and as a mask layer. Fast crystallization within 90 ns was achieved using a pulsed high-power laser beam of 405 nm wavelength. Dynamic recording performance of the new structure showed carrier-to-noise ratios (CNR) of 37 and 18 dB obtained for 80 and 50 nm mark sizes, respectively. Readout thermal stability of 12,000 cycles was realized for 80 nm mark sizes. The incorporation of Sn-doped GeSbTe (GST) as mask layer in the super-RENS structure significantly improved the CNR and thermal stability of the disk.

  13. In situ X-ray diffraction study of crystallization process of GeSbTe thin films during heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Naohiko [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan)]. E-mail: e0957@mosk.tytlabs.co.jp; Konomi, Ichiro [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Seno, Yoshiki [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Motohiro, Tomoyoshi [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan)

    2005-05-15

    The crystallization processes of the Ge{sub 2}Sb{sub 2}Te{sub 5} thin film used for PD and DVD-RAM were studied in its realistic optical disk film configurations for the first time by X-ray diffraction using an intense X-ray beam of a synchrotron orbital radiation facility (SPring-8) and in situ quick detection with a Position-Sensitive-Proportional-Counter. The dependence of the amorphous-to-fcc phase-change temperature T{sub 1} on the rate of temperature elevation R{sub et} gave an activation energy E{sub a}: 0.93 eV much less than previously reported 2.2 eV obtained from a model sample 25-45 times thicker than in the real optical disks. The similar measurement on the Ge{sub 4}Sb{sub 1}Te{sub 5} film whose large reflectance change attains the readability by CD-ROM drives gave E{sub a}: 1.13 eV with larger T{sub 1} than Ge{sub 2}Sb{sub 2}Te{sub 5} thin films at any R{sub et} implying a lower sensitivity in erasing as well as a better data stability of the phase-change disk.

  14. Studies of Nano-structured Se77Sb23- x Ge x Thin Films Prepared by Physical Vapor Condensation Technique

    Science.gov (United States)

    Alvi, M. A.

    2017-02-01

    Bulk Se77Sb23- x Ge x material with x = 4 and 12 was prepared by employing a melt quench technique. Its amorphous as well as glassy nature was confirmed by x-ray diffraction analysis and nonisothermal differential scanning calorimetry measurements. The physical vapor condensation technique was applied to prepare nanostructured thin films of Se77Sb23- x Ge x material. The surface morphology of the films was examined using field-emission scanning electron microscopy, revealing average particle size between 20 nm and 50 nm. Systematic investigation of optical absorption data indicated that the optical transition was indirect in nature. The dark conductivity (dc conductivity) of nano-structured Se77Sb23- x Ge x thin films was also investigated at temperatures from 313 K to 463 K, revealing that it tended to increase with increasing temperature. Analyses of our experimental data also indicate that the conduction is due to thermally supported tunneling of charge carriers in confined states close to the band edges. The calculated values of activation energy agree well with the optical bandgap.

  15. Effect of composition on optical properties of GeSe3–Sb2Se3–ZnSe thin films

    Indian Academy of Sciences (India)

    M R Balboul; H M Hosni; M A Soliman; S A Fayek

    2014-10-01

    Optical properties of the chalcogenides GeSe3, Sb2Se3, ZnSe, (GeSe3)80(Sb2Se3)20 and (GeSe3)70 (Sb2Se3)10(ZnSe)20 thin films are investigated. Incorporation of ZnSe into both GeSe3, Sb2Se3 results in amorphous (GeSe3)70(Sb2Se3)10(ZnSe)20 composition. The estimated optical energy gap, g, is found to decrease from 3.06 eV for ZnSe to 1.81 eV for (GeSe3)70(Sb2Se3)10(ZnSe)20. While, the band tail width, e, exhibits an opposite trend. The g behaviour is believed to be associated with cohesive energy, CE, as the incorporation of ZnSe lowers its value. The calculated number of the excess of Se–Se homopolar bonds is found to affect mainly the e values. The refractive index, , is discussed in terms of Wemple–DiDomenico single oscillator dispersion model in the normal dispersion region. The oscillator energy, o, and the dispersion energy, d, are determined for films under investigation.

  16. Distribution of Sb, As, Ge, and In between metal and silicate during accretion and core formation in the Earth

    Science.gov (United States)

    Righter, K.; Nickodem, K.; Pando, K.; Danielson, L.; Boujibar, A.; Righter, M.; Lapen, T. J.

    2017-02-01

    A large number of siderophile (iron-loving) elements are also volatile, thus offering constraints on the origin of volatile elements in differentiated bodies such as Earth, Moon, Mars and Vesta. Metal-silicate partitioning data for many of these elements is lacking, making their overall mantle concentrations in these bodies difficult to model and origin difficult to distinguish between core formation and volatile depletion. To address this gap in understanding, we have undertaken systematic studies of four volatile siderophile elements - Sb, As, Ge and In - at variable temperature and variable Si content of metal. Several series were carried out at 1 GPa, and between 1500 and 1900 °C, for both C saturated and C-free conditions. The results show that temperature causes a decrease in the metal/silicate partition coefficient for all four elements. In addition, activity coefficients for each element have been determined and show a very strong dependence on Si content of Fe alloy. Si dissolved in metal significantly decreases the metal/silicate partition coefficients, at both 1600 and 1800 °C. The combination of temperature and Si content of the metal causes reduction of the metal-silicate partition coefficient to values that are close to those required for an origin of mantle As, Sb, Ge, and In concentrations by metal-silicate equilibrium processes. Combining these new results with previous studies on As, Sb, Ge, and In, allowed derivation of predictive expressions for metal/silicate partition coefficients for these elements which can then be applied to Earth. The expressions are applied to two scenarios for continuous accretion of Earth; specifically for constant and increasing fO2 during accretion. The results indicate that mantle concentrations of As, Sb, Ge, and In can be explained by metal-silicate equilibrium during an accretion scenario. The modeling is not especially sensitive to either scenario, although all element concentrations are explained better by a

  17. Effect of antimony (Sb) addition on the linear and non-linear optical properties of amorphous Ge-Te-Sb thin films

    Science.gov (United States)

    Kumar, P.; Kaur, J.; Tripathi, S. K.; Sharma, I.

    2017-06-01

    Non-crystalline thin films of Ge20Te80-xSbx (x = 0, 2, 4, 6, 10) systems were deposited on glass substrate using thermal evaporation technique. The optical coefficients were accurately determined by transmission spectra using Swanepoel envelope method in the spectral region of 400-1600 nm. The refractive index was found to increase from 2.38 to 2.62 with the corresponding increase in Sb content over the entire spectral range. The dispersion of refractive index was discussed in terms of the single oscillator Wemple-DiDomenico model. Tauc relation for the allowed indirect transition showed decrease in optical band gap. To explore non-linearity, the spectral dependence of third order susceptibility of a-Ge-Te-Sb thin films was evaluated from change of index of refraction using Miller's rule. Susceptibility values were found to enhance rapidly from 10-13 to 10-12 (esu), with the red shift in the absorption edge. Non-linear refractive index was calculated by Fourier and Snitzer formula. The values were of the order of 10-12 esu. At telecommunication wavelength, these non-linear refractive index values showed three orders higher than that of silica glass. Dielectric constant and optical conductivity were also reported. The prepared Sb doped thin films on glass substrate with observed improved functional properties have a noble prospect in the application of nonlinear optical devices and might be used for a high speed communication fiber. Non-linear parameters showed good agreement with the values given in the literature.

  18. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Science.gov (United States)

    Liang, Guangfei; Li, Simian; Huang, Huan; Wang, Yang; Lai, Tianshu; Wu, Yiqun

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge2Sb2Te5 (GeSbTe) and Ag8In14Sb55Te23 (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  19. Interface formation of two- and three-dimensionally bonded materials in the case of GeTe-Sb2Te3 superlattices

    Science.gov (United States)

    Momand, Jamo; Wang, Ruining; Boschker, Jos E.; Verheijen, Marcel A.; Calarco, Raffaella; Kooi, Bart J.

    2015-11-01

    GeTe-Sb2Te3 superlattices are nanostructured phase-change materials which are under intense investigation for non-volatile memory applications. They show superior properties compared to their bulk counterparts and significant efforts exist to explain the atomistic nature of their functionality. The present work sheds new light on the interface formation between GeTe and Sb2Te3, contradicting previously proposed models in the literature. For this purpose [GeTe(1 nm)-Sb2Te3(3 nm)]15 superlattices were grown on passivated Si(111) at 230 °C using molecular beam epitaxy and they have been characterized particularly with cross-sectional HAADF scanning transmission electron microscopy. Contrary to the previously proposed models, it is found that the ground state of the film actually consists of van der Waals bonded layers (i.e. a van der Waals heterostructure) of Sb2Te3 and rhombohedral GeSbTe. Moreover, it is shown by annealing the film at 400 °C, which reconfigures the superlattice into bulk rhombohedral GeSbTe, that this van der Waals layer is thermodynamically favored. These results are explained in terms of the bonding dimensionality of GeTe and Sb2Te3 and the strong tendency of these materials to intermix. The findings debate the previously proposed switching mechanisms of superlattice phase-change materials and give new insights in their possible memory application.GeTe-Sb2Te3 superlattices are nanostructured phase-change materials which are under intense investigation for non-volatile memory applications. They show superior properties compared to their bulk counterparts and significant efforts exist to explain the atomistic nature of their functionality. The present work sheds new light on the interface formation between GeTe and Sb2Te3, contradicting previously proposed models in the literature. For this purpose [GeTe(1 nm)-Sb2Te3(3 nm)]15 superlattices were grown on passivated Si(111) at 230 °C using molecular beam epitaxy and they have been characterized

  20. Efecto del Oxigeno en la Cristalización de Películas Delgadas de GeSbTe

    OpenAIRE

    E. Morales- Sánchez; C. Rivera- Rodríguez; E. Prokhorov; J. González Hernández

    2010-01-01

    En este trabajo se desarrolló un nuevo material para capa activa en Memorias Ópticas Reversibles (MOR), el cual permite grabar información utilizando tres o cuatro niveles de reflectividad en cada punto. Este nuevo material esta basado en Ge1Sb2Te4 dopadas con oxigeno. La técnica de difracción de rayos X muestran que para películas con porcentajes de oxigeno de entre 2 y 8% at. de oxigeno presente en la muestra y cristalizadas a 110° C, la fase cristalina corresponde a la composición estequio...

  1. Role of mechanical stress in the resistance drift of Ge2Sb2Te5 films and phase change memories

    Science.gov (United States)

    Rizzi, M.; Spessot, A.; Fantini, P.; Ielmini, D.

    2011-11-01

    In a phase change memory (PCM), the device resistance increases slowly with time after the formation of the amorphous phase, thus affecting the stability of stored data. This work investigates the resistance drift in thin films of amorphous Ge2Sb2Te5 and in PCMs, demonstrating a common kinetic of drift in stressed/unstressed films and in the nanometer-size active volume of a PCM with different stress levels developed via stressor layers. It is concluded that stress is not the root cause of PCM drift, which is instead attributed to intrinsic structural relaxation due to the disordered, metastable nature of the amorphous chalcogenide phase.

  2. The influence of oxygen and nitrogen doping on GeSbTe phase-change optical recording media properties

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrov, D.; Shieh, H.-P.D

    2004-03-15

    Nitrogen and oxygen doped and co-doped GeSbTe (GST) films for phase-change optical recording are investigated. It is found that the crystallization temperature increased as well as the crystalline microstructure refined by doping. The carrier-to-noise ratio (CNR) and erasability of phase-change optical disks are improved being up to 52 and 35 dB, respectively, by using an appropriate nitrogen doping or co-doping concentration in the recording layer. Optical disks with co-doped recording layer are found to be superior in the recording characteristics then the single doped recording layer disks.

  3. X-ray Stress Evaluation in Phase Change GeSbTe Material and TiW Electrodes

    Science.gov (United States)

    Minghua Li,; Luping Shi,; Rong Zhao,; Tow Chong Chong,; Yi Li,

    2010-05-01

    Stress generation and relaxation upon Ge2Sb2Te5 (GST) crystallization were studied by X-ray diffraction technique, which allows the stress in either GST or Ti3W7 (TiW) to be evaluated independently within TiW/GST/TiW multilayer film. The GST crystallization results in tensile stress in the GST film and additional compressive stress in the TiW film, due to volume shrinkage of the GST film. Moreover, the tensile stress in the GST film is significantly increased when it is sandwiched between TiW films. Interfacial effect is proposed to attribute the dependence of stress on the capping layer thickness.

  4. Laser induced photoluminescence from Ge{sub 28}Se{sub 60}Sb{sub 12} chalcogenide nano colloids

    Energy Technology Data Exchange (ETDEWEB)

    Tintu, R., E-mail: tintu_tillanivas@yahoo.co.in [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam-686560 (India); Nampoori, V.P.N.; Radhakrishnan, P.; Thomas, Sheenu [International School of Photonics, Cochin University of Science and Technology, Cochin 689110 (India); Unnikrishnan, N.V. [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam-686560 (India)

    2013-04-01

    We report the observation of two-photon induced photoluminescence from Ge{sub 28}Se{sub 60}Sb{sub 12} nano colloid solutions using frequency doubled Nd:YAG laser. Quadratic emission intensity dependence verifies the two photon absorption for the observed luminescence at an excitation of 532 nm. The optical band gap of the material is found to be tunable depending on the cluster size of the nano colloids. The cluster formation and the dependence of the cluster size with concentration were confirmed by the SEM analysis. Confocal imaging was done to confirm the emission from the clusters in the nano colloid solutions.

  5. Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Jos E. Boschker

    2017-01-01

    Full Text Available The realization of textured films of 2-dimensionally (2D bonded materials on amorphous substrates is important for the integration of this material class with silicon based technology. Here, we demonstrate the successful growth by molecular beam epitaxy of textured Sb2Te3 films and GeTe/Sb2Te3 superlattices on two types of amorphous substrates: carbon and SiO2. X-ray diffraction measurements reveal that the out-of-plane alignment of grains in the layers has a mosaic spread with a full width half maximum of 2.8°. We show that a good texture on SiO2 is only obtained for an appropriate surface preparation, which can be performed by ex situ exposure to Ar+ ions or by in situ exposure to an electron beam. X-ray photoelectron spectroscopy reveals that this surface preparation procedure results in reduced oxygen content. Finally, it is observed that film delamination can occur when a capping layer is deposited on top of a superlattice with a good texture. This is attributed to the stress in the capping layer and can be prevented by using optimized deposition conditions of the capping layer. The obtained results are also relevant to the growth of other 2D materials on amorphous substrates.

  6. Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

    Science.gov (United States)

    Boschker, Jos E.; Tisbi, E.; Placidi, E.; Momand, Jamo; Redaelli, Andrea; Kooi, Bart J.; Arciprete, Fabrizio; Calarco, Raffaella

    2017-01-01

    The realization of textured films of 2-dimensionally (2D) bonded materials on amorphous substrates is important for the integration of this material class with silicon based technology. Here, we demonstrate the successful growth by molecular beam epitaxy of textured Sb2Te3 films and GeTe/Sb2Te3 superlattices on two types of amorphous substrates: carbon and SiO2. X-ray diffraction measurements reveal that the out-of-plane alignment of grains in the layers has a mosaic spread with a full width half maximum of 2.8°. We show that a good texture on SiO2 is only obtained for an appropriate surface preparation, which can be performed by ex situ exposure to Ar+ ions or by in situ exposure to an electron beam. X-ray photoelectron spectroscopy reveals that this surface preparation procedure results in reduced oxygen content. Finally, it is observed that film delamination can occur when a capping layer is deposited on top of a superlattice with a good texture. This is attributed to the stress in the capping layer and can be prevented by using optimized deposition conditions of the capping layer. The obtained results are also relevant to the growth of other 2D materials on amorphous substrates.

  7. Influence of peripheral vibrations and traveling magnetic fields on VGF growth of Sb-doped Ge crystals

    Science.gov (United States)

    Dropka, Natasha; Frank-Rotsch, Christiane; Rudolph, Peter

    2016-11-01

    We performed 3D numerical and experimental studies to assess the potential of peripheral low frequency mechanical vibrations for improving the homogeneity of Sb-doped 4″ Ge crystals grown by vertical gradient freeze (VGF). For this study, a novel bell-shaped graphite vibrator was developed for the generation of the axial vibrations in the direction of three-phase junction. Melt stirring by downward traveling magnetic field (TMF) was used as a benchmark. The results showed superiority of peripheral vibrations to TMF stirring concerning radial and longitudinal doping distribution and initial stirring rate. Experimentally observed standing free surface waves in Ge were caused by shielding effect of the vibrator on TMF.

  8. 基于GeSbTe膜的探针存储机制的研究%Study of Data Storage Mechanism with GeSbTe Film based on SPM

    Institute of Scientific and Technical Information of China (English)

    范真; 丁建宁; 朱守星; 解国新; 凌智勇; 杨平

    2006-01-01

    针对基于原子力显微镜(AFM)的探针相变存储研究中存储介质和存储方贩性的研究.比较了用直流磁控溅射部分不同工艺参数所制备的GeSb2Te4薄膜的表面性能,同时对探针诱导相变机理进行了初步探讨.试验观察的结果表明,利用AFM导电探针对相变化材料GeSb2Te4膜施加一定的直流电压,可以通过形貌和相结构的变化来获得存储的信息点,并且通过施加一定时间的反向电压可以实现信息点的消除.

  9. Ge1Sb2Te4 Based Chalcogenide Random Access Memory Array Fabricated by 0.18-μm CMOS Technology

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ting; SONG Zhi-Tang; FENG Gao-Ming; LIU Bo; WU Liang-Cai; FENG Song-Lin; CHEN Bomy

    2007-01-01

    Ge1Sb2Te4-based chalcogenide random access memory array, with a tungsten heating electrode of 260nm in diameter, is fabricated by 0.18-μm CMOS technology. Electrical performance of the device, as well as physical and electrical properties of Ge1Sb2Te4 thin film, is characterized. SET and RESET programming currents are 1.6 and 4.1 mA, respectively, when pulse width is 100ns. Both the values are larger than those of the Ge2Sb2 Te5-based ones with the same structure and contact size. Endurance up to 106 cycles with a resistance ratio of about 100 has been achieved.

  10. Density functional study of the TiN/Ge{sub 2}Sb{sub 2}Te{sub 5} interface

    Energy Technology Data Exchange (ETDEWEB)

    Mandelli, D.; Bernasconi, M. [Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via R. Cozzi 53, 20125 Milano (Italy); Caravati, S. [Department of Chemistry and Applied Biosciences, ETH Zurich (Switzerland); Facolta di Informatica, Istituto di Scienze Computazionali, Universita della Svizzera Italiana, Lugano (Switzerland)

    2012-11-15

    We studied the epitaxial TiN(001)/Ge{sub 2}Sb{sub 2}Te{sub 5}(001) (GST) interface of interest for applications in phase change non-volatile memories by means of density functional calculations. The cubic phase of GST of interest for the memory devices was considered. From geometry optimization we found an equilibrium distance of about 3.0 Aa between Ti and Te, Ge and Sb atoms located directly above along the [001] direction. The interface formation energy of a large 1440-atom model is {gamma}{sub int} = 50 meV/Aa{sup 2}. The surface energy of TiN(001) and GST(001) are {gamma}{sub S} = 81 and 10 meV/Aa{sup 2} resulting in an adhesion energy of {gamma}{sub ad} = 41 meV/Aa{sup 2}. A good adhesion between the two materials can thus be achieved in the ideal epitaxial configuration. The presence of metal induced gap states (MIGS) is revealed by the analysis of Kohn-Sham (KS) orbitals. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Electronic and Optical Properties of Ca3MN (M = Ge, Sn, Pb, P, As, Sb and Bi) Antiperovskite Compounds

    Science.gov (United States)

    Iqbal, Samad; Murtaza, G.; Khenata, R.; Mahmood, Asif; Yar, Abdullah; Muzammil, M.; Khan, Matiullah

    2016-08-01

    The electronic and optical properties of cubic antiperovskites Ca3MN (M = Ge, Sn, Pb, P, As, Sb and Bi) were investigated by applying the full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) scheme based on density functional theory. Different exchange correlation potentials were adopted for the calculations. The results of band structure and density of states show that, by changing the central anion of Ca3MN, the nature of the materials change from metallic (Ca3GeN, Ca3SnN, Ca3PbN) to semiconducting with small band gaps (Ca3SbN and Ca3BiN) to insulating (Ca3PN and Ca3AsN). The optical properties such as dielectric function, absorption coefficient, optical conductivity, reflectivity and refractive indices have also been calculated. The results reveal that all the studied compounds are optically active in the visible and ultraviolet energy regions, and therefore can be effectively utilized for optoelectronic devices.

  12. First Principles Study of structural characteristics and phase change mechanism of Ge-Sb-Te based materials

    Science.gov (United States)

    Park, Hanjin; Kim, Cheol-Woon; Lee, Hyung-June; Song, Hosin; Kwon, Young-Kyun

    Using ab initio density functional theory, we investigate the structural properties and their phase transition mechanism of the crystalline and amorphous phases of Ge-Sb-Te (GST) based phase change materials, which would be utilized for phase change random access memory. Among various stochiometries of GST, we focus on compositions along the (GeTe)n(Sb2Te3)m pseudo-binary line, denoted simply by (n , m) with integer n and m. We explore various GST materials corresponding (n , m) sets including (1,0), (0,1), (1,1), (2,1) and (1,2) by modeling their both phases. Especially, their amorphous phases can be constructed based on experimental data available or molecular dynamics (MD) simulations performing melt-quench processes. To understand the phase transition mechanism, we evaluate their coordination numbers, radial distribution functions, and angle distribution functions, which enables us to identify the characteristic local geometry representing each phase. We further investigate the thermal properties of various phases by evaluating their phonon densities of states obtained by Fourier-transforming the velocity autocorrelation functions calculated directly from our MD simulation.

  13. {sup 197}Au irradiation study of phase-change memory cell with GeSbTe alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Liangcai; Song, Zhitang; Lian, Jie; Rao, Feng; Liu, Bo; Song, Sannian; Liu, Weili; Feng, Songlin [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Zhou, Xilin; Liu, Xuyan [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100080 (China)

    2010-10-15

    A {sup 197}Au ion source was used to irradiate a Ge{sub 2}Sb{sub 2}Te{sub 5}-alloy-based phase-change memory (PCM) cell to study the ion-irradiation effect on the properties of the cell. The PCM devices with the tungsten (W) heating electrode of 260 nm diameter were fabricated by 0.18 {mu}m complementary metal-oxide-semiconductor (CMOS) technology. Four different doses (10{sup 10}, 10{sup 11}, 10{sup 12}, and 5 x 10{sup 12} ions/cm{sup 2}, respectively) were applied to irradiate the PCM cell. The samples before and after irradiation were characterized by current-voltage and resistance measurements at room temperature. It is found that the cell properties (resistance value of the amorphous and crystalline states, threshold voltage, and current for phase transition, etc.) have hardly changed, even for the sample irradiated up to 10{sup 12} ions/cm{sup 2} dose, and the cell still has good set-reset operation ability (above 10{sup 5} cycles). Furthermore, the resistance ratio remains at 1000 even after 10{sup 5} cycles of the set-reset operation. The results show the PCM cell with Ge{sub 2}Sb{sub 2}Te{sub 5} alloy has a strong ion-irradiation tolerance. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  14. Growth and thermal stability of single crystal metastable semiconducting (GaSb)/sub 1-x/Ge/sub x/ films

    Energy Technology Data Exchange (ETDEWEB)

    Cadien, K.C.; Eltoukhy, A.H.; Greene, J.E.

    1981-01-01

    Epitaxial metastable (GaSb)/sub 1-x/)Ge/sub x/ alloys with compositions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. The maximum growth temperature T/sub s/ ranged from 490 to 520/sup 0/C depending on the alloy composition. An essential feature allowing the growth of these metastable materials was low energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second phase precipitates. A phase map plotted as a function of T/sub s/ showed a very narrow transition region between metastable single phase alloys and equilibrium two phase structures. Annealing experiments indicated that the metastable films exhibit good high temperature stability and that they transform through a continuous series of GaSb-rich and Ge-rich phases in which the solute concentrations decrease until the equilibrium two phase alloy is obtained. While the calculated free energy difference between the single phase metastable and equilibrium states is approx. 18 MeV atom/sup -1/, the measured activation barrier for the transformation is approx. 3 eV. All films were p-type with room temperature hole concentrations varying from 10/sup 16/ to 10/sup 19/ cm/sup -3/ and mobilities between 10 and 720 cm/sup 2//V-s, depending on film composition.

  15. Growth of single-crystal metastable semiconducting (GaSb)/sub 1//sub -//sub x/Ge/sub x/ films

    Energy Technology Data Exchange (ETDEWEB)

    Cadien, K.C.; Eltoukhy, A.H.; Greene, J.E.

    1981-05-15

    Epitaxial metastable (GaSb)/sub 1-x/Ge/sub x/ alloys with compostions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. An essential feature allowing the growth of these metastable materials was low-energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second-phase precipitates. Annealing experiments indicated that the metastable films exhibit good high-temperature stability and that they transform through a continuous series of GaSb-rich and Ge-rich phases in which the solute concentrations decrease until the equilibrium two-phase alloy is obtained. While the calculated free-energy difference between the single-phase metastable and equilibrium states is approx.18 meV, the measured activation barrier for the transformation is approx.3 eV. All films were p-type with room-temperature hole concentrations varying from 10/sup 16/ to 10/sup 19/ cm/sup -3/ and mobilities between 10 and 720 cm/sup 2// V s, depending on film composition.

  16. Deposition of Ge{sub 23}Sb{sub 7}S{sub 70} chalcogenide glass films by electrospray

    Energy Technology Data Exchange (ETDEWEB)

    Novak, Spencer, E-mail: spencen@g.clemson.edu [Department of Materials Science and Engineering, COMSET, Clemson University, Clemson, SC (United States); College of Optics and Photonics, CREOL, University of Central FL (United States); Johnston, Danvers E.; Li, Cheng; Deng, Weiwei [Department of Mechanical and Aerospace Engineering, University of Central FL (United States); Richardson, Kathleen [Department of Materials Science and Engineering, COMSET, Clemson University, Clemson, SC (United States); College of Optics and Photonics, CREOL, University of Central FL (United States)

    2015-08-03

    Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge{sub 23}Sb{sub 7}S{sub 70} films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films. - Highlights: • Electrospray film deposition processing of Ge{sub 23}Sb{sub 7}S{sub 70} films was developed. • Traditional spin-coated films were also fabricated in parallel. • Optical properties and surface quality found to be similar between two approaches.

  17. Role of interfaces on the stability and electrical properties of Ge2Sb2Te5 crystalline structures.

    Science.gov (United States)

    Mio, A M; Privitera, S M S; Bragaglia, V; Arciprete, F; Cecchi, S; Litrico, G; Persch, C; Calarco, R; Rimini, E

    2017-06-01

    GeSbTe-based materials exhibit multiple crystalline phases, from disordered rocksalt, to rocksalt with ordered vacancy layers, and to the stable trigonal phase. In this paper we investigate the role of the interfaces on the structural and electrical properties of Ge2Sb2Te5. We find that the site of nucleation of the metastable rocksalt phase is crucial in determining the evolution towards vacancy ordering and the stable phase. By properly choosing the substrate and the capping layers, nucleation sites engineering can be obtained, thus promoting or preventing the vacancy ordering in the rocksalt structure or the conversion into the trigonal phase. The vacancy ordering occurs at lower annealing temperatures (170 °C) for films deposited in the amorphous phase on silicon (111), compared to the case of SiO2 substrate (200 °C), or in presence of a capping layer (330 °C). The mechanisms governing the nucleation have been explained in terms of interfacial energies. Resistance variations of about one order of magnitude have been measured upon transition from the disordered to the ordered rocksalt structure and then to the trigonal phase. The possibility to control the formation of the crystalline phases characterized by marked resistivity contrast is of fundamental relevance for the development of multilevel phase change data storage.

  18. Photo-induced changes of the optical constants of chalcodenide Ge19Sb1Te80 films

    Science.gov (United States)

    Pamukchieva, Vesela; Szekeres, Anna M.; Todorova, Kalina

    2004-10-01

    In this work a preliminary study of the influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge19Sb1Te80 composition is presented. Films of Ge19Sb1Te80 with a thickness of ~1 μm were deposited onto glass substrates by vacuum thermal evaporation of parent glasses. The as-deposited films were exposed to light by using a 500 W HBO mercury lamp. The optical constants of the films, before and after their illumination, were evaluated from the ellipsometric measurements in the spectral range of 300 - 820 nm. It has been established that illumination of the films leads to a decrease of the refractive index in the studied spectral region, while a slight increase of the extinction coefficient in the 600 - 800 nm range is observed. For the given film composition the optical bandgap energy of 0.76 eV reduces to 0.62 eV. The film structure shows a very slow recovery expresed in the increase of bandgap energy towards its initial value. The observed decrease of the bandgap energy after illumination is indicative that the film structure undergoes rearrangements upon exposure to light leading to the effect of photodarkening.

  19. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ni [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Jiang, Shiuh-Jen, E-mail: sjjiang@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Yen-Ling [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Sahayam, A.C. [National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad (India)

    2015-02-20

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL{sup −1} Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g{sup −1} for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  20. Nanoscale mechanically induced structural and electrical changes in Ge{sub 2}Sb{sub 2}Te{sub 5} films

    Energy Technology Data Exchange (ETDEWEB)

    Cecchini, R.; Benitez, J. J.; Sanchez-Lopez, J. C.; Fernandez, A. [Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Avenida Americo Vespucio 49, 41092 -Seville (Spain)

    2012-01-01

    We demonstrate that the microstructure and electrical properties of Ge{sub 2}Sb{sub 2}Te{sub 5} films can be changed by a nanoscale mechanical process. Nanoscratching is used to define modified areas onto an as-deposited crystalline Ge{sub 2}Sb{sub 2}Te{sub 5} film. Scanning tunneling microscopy measurements show that the modified areas have a very low electrical conductivity. Micro-Raman measurements indicate that the mechanically induced microstructural changes are consistent with a phase transformation from crystalline to amorphous, which can be reversed by laser irradiation.

  1. First principle study of structural, electronic and magnetic properties of half-Heusler IrCrZ (Z=Ge, As, sn and sb) compounds

    Science.gov (United States)

    Allaf Behbahani, Marzieh; Moradi, Mahmood; Rostami, Mohammad; Davatolhagh, Saeed

    2016-05-01

    First-principle calculations based on the density functional theory for new half-Heusler IrCrZ (Z=Ge, As, Sn and Sb) alloys are performed. It is found that the half-Heusler IrCrGe and IrCrSn compounds have an antiferromagnetic ground state while the ferromagnetic state is more stable than the antiferromagnetic and non-magnetic states for both IrCrAs and IrCrSb compounds. IrCrAs and IrCrSb exhibit half-metallic property with integer magnetic moments of 2.00 μB per formula unit and half-metallic gaps of 0.28 and 0.27 eV at their equilibrium volume, respectively. In addition, the density of states (DOSs) and band structures of IrCrAs and IrCrSb compounds are studied and the origin of their half-metallic gaps are discussed in detail. The estimation of Curie temperatures of IrCrAs and IrCrSb compounds is performed within the mean field approximation (MFA). The Curie temperatures of IrCrAs and IrCrSb are estimated to be 1083 and 1470 K, respectively. The stability of the half-metallicity in IrCrAs and IrCrSb compounds with the variation of lattice constant are also investigated.

  2. Reduction of RESET current in phase change memory devices by carbon doping in GeSbTe films

    Science.gov (United States)

    Park, J. H.; Kim, S.-W.; Kim, J. H.; Wu, Z.; Cho, S. L.; Ahn, D.; Ahn, D. H.; Lee, J. M.; Nam, S. U.; Ko, D.-H.

    2015-03-01

    Phase Change Memory (PCM) has been proposed for use as a substitute for flash memory to satisfy the huge demands for high performance and reliability that promise to come in the next generation. In spite of its high scalability, reliability, and simple structure, high writing current, e.g., RESET current, has been a significant obstacle to achieving a high density in storage applications and the low power consumption required for use in mobile applications. We report herein on an attempt to determine the level of carbon incorporated into a GeSbTe (GST) film that is needed to reduce the RESET current of PCM devices. The crystal structure of the film was transformed into an amorphous phase by carbon doping, the stability of which was enhanced with increasing carbon content. This was verified by the small grain size and large band gap that are typically associated with carbon. The increased level of C-Ge covalent bonding is responsible for these enhancements. Thus, the resistance of the carbon doped Ge2Sb2Te5 film was higher than that for an undoped GST film by a factor of 2 orders of magnitude after producing a stable face-centered cubic phase by annealing. As a consequence, the PCM devices showed a significant reduction in RESET current as low as 23% when the carbon content was increased to 11.8 at. %. This can be attributed to the elevated SET resistance, which is proportional to the dynamic resistance of the PCM device, caused by the high resistance due to a carbon doped GST film.

  3. Adhesion and friction properties of GeSbTe phase change films prepared by magnetron sputtering%磁控溅射GeSbTe相变薄膜黏附与摩擦特性

    Institute of Scientific and Technical Information of China (English)

    付永忠; 程广贵; 王权

    2012-01-01

    室温下通过调整磁控溅射时间制备了不同厚度的GeSbTe薄膜.利用原子力显微镜和台阶仪观察薄膜的表面形貌,测量薄膜厚度,并借助TriboIndenter纳米力学测试系统,分析探讨了薄膜的黏附和摩擦特性.研究结果表明:随着溅射时间的增加,薄膜表面粗糙度减小,厚度增加,同时表面质量提高;探针直径、相对湿度、薄膜表面质量以及探针载荷等因素对薄膜的黏附和摩擦特性均有重要影响;在满足存储要求的前提下,通过减小探针直径、降低相对湿度能够有效降低黏附力和摩擦力;而提高薄膜表面质量,为探针施加合适的载荷,有助于改善探针与薄膜表面之间的摩擦特性.%The GeSbTe films were prepared with different RF magnetron sputtering time at room temperature. The surface topography, thickness, adhesion and friction properties of films were investigated by a-tomic force microscopy (AFM) , Talystep and Tribolndenter nanomechanical test system. The results show that the surface roughness decreases with the increasing of sputtering time, while the thickness and quality increase. The tip diameter(TD) , relative humidity(RH) ,normal load(NL) applied the tip are important factors on adhesion and friction properties of films. The adhesion and friction between the tip and GeSbTe films can be reduced obviously by the decreasing of TD and RH. The frictional performance can be improved by enhancing surface quality and choosing appropriate NL on the tip.

  4. Effects of dopants on the amorphous-to-fcc transition in Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Privitera, S. [R and D Department, Micro, Power, Analog (MPA) Group, STMicroelectronics, MP8, Stradale Primosole 50, 95121 Catania (Italy)]. E-mail: stefania.privitera@st.com; Rimini, E. [Istituto di Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Stradale Primosole 50, 95121 Catania (Italy); Bongiorno, C. [Istituto di Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Stradale Primosole 50, 95121 Catania (Italy); Pirovano, A. [FTM, Advanced R and D, NVMTD, STMicroelectronics, Via Olivetti 2, 20041, Agrate Brianza (Italy); Bez, R. [FTM, Advanced R and D, NVMTD, STMicroelectronics, Via Olivetti 2, 20041, Agrate Brianza (Italy)

    2007-04-15

    The amorphous-to-crystal transition has been studied through in situ resistance measurements in Ge{sub 2}Sb{sub 2}Te{sub 5} thin films doped by ion implantation with nitrogen, oxygen or fluorine at different concentrations. Enhancement of the thermal stability has been observed in O and N amorphous doped Ge{sub 2}Sb{sub 2}Te{sub 5}. Larger effects have been found in the case of nitrogen doping. On the contrary, doping with Fluorine produced a decrease in the crystallization temperature. The electrical properties have been related to the structural phase change through in situ transmission electron microscopy analysis. The comparison between undoped and doped Ge{sub 2}Sb{sub 2}Te{sub 5} shows that the introduction of oxygen or nitrogen modifies in a different way the kinetics of the amorphous-to-fcc transition and gives new insight on the effects of doping with light elements in GeSbTe alloys.

  5. Interface formation of two- and three-dimensionally bonded materials in the case of GeTe-Sb2Te3 superlattices

    NARCIS (Netherlands)

    Momand, Jamo; Wang, Ruining; Boschker, Jos E.; Verheijen, Marcel A.; Calarco, Raffaella; Kooi, Bart J.

    2015-01-01

    GeTe-Sb2Te3 superlattices are nanostructured phase-change materials which are under intense investigation for non-volatile memory applications. They show superior properties compared to their bulk counterparts and significant efforts exist to explain the atomistic nature of their functionality. The

  6. Reversible electrical resistance switching in GeSbTe thin films : An electrolytic approach without amorphous-crystalline phase-change

    NARCIS (Netherlands)

    Pandian, Ramanathaswamy; Kooi, Bart J.; Palasantzas, George; De Hosson, Jeff Th. M.; Wouters, DJ; Hong, S; Soss, S; Auciello, O

    2008-01-01

    Besides the well-known resistance switching originating from the amorphous-crystalline phase-change in GeSbTe thin films, we demonstrate another switching mechanism named 'polarity-dependent resistance (PDR) switching'. 'Me electrical resistance of the film switches between a low- and high-state whe

  7. Thermomechanical Analysis on the Phase Stability of Nitrogen-Doped Amorphous Ge2Sb2Te5 Films

    Science.gov (United States)

    Park, Il-Mok; Cho, Ju-Young; Yang, Tae-Youl; Park, Eun Soo; Joo, Young-Chang

    2011-06-01

    The phase stability of amorphous Ge2Sb2Te5 (GST) films affects the performance and reliability of phase change memory (PRAM) devices. The viscosity and the glass forming ability of nitrogen (N)-doped amorphous GST films were investigated in terms of thermomechanical behavior using wafer curvature measurements. The viscosity which increased by two orders of magnitude was observed in the N-doped amorphous GST film by measuring the stress relaxation accompanied by bimolecular structural relaxation. The glass forming ability (ΔTx), difference between the glass transition temperature (Tg) and the crystallization temperature (Tc), of GST increased as the nitrogen contents increased. These increases in the viscosity and ΔTx indicate the retardation of atomic diffusion in amorphous GST and the stabilization of the amorphous phase.

  8. The Si(100)-Sb 2{times}1 and Ge(100) 2{times}1 surfaces: A multi-technique study

    Energy Technology Data Exchange (ETDEWEB)

    Richter, M.

    1993-08-01

    The electronic and geometric structures of the clean and Sb terminated Si(100)2{times}1 and Ge(100)-2{times}1 surfaces have been investigated using a multi-technique approach. Low energy electron diffraction (LEED), scanning tunneling microscopy (STM), surface extended X-ray absorption fine structure (SEXAFS) spectroscopy and angle-integrated core-level photoemission electron spectroscopy (PES) were employed to measure the surface symmetry, defect structure, relevant bond lengths, atomic coordination and electronic structure. By employing a multi-technique approach, it is possible to correlate changes in the geometric structure to specific features of the core-level lineshape of the substrate. This allows for the assignment of components of the core-level lineshape to be assigned to specific surface and near-surface atoms.

  9. Ultrafast sub-threshold photo-induced response in crystalline and amorphous GeSbTe thin films

    Science.gov (United States)

    Shu, M. J.; Chatzakis, I.; Kuo, Y.; Zalden, P.; Lindenberg, A. M.

    2013-05-01

    Pump-probe optical reflectivity and terahertz transmission measurements have been used to investigate time resolved sub-threshold photo-induced effects in crystalline and amorphous GeSbTe films at MHz repetition rates. The reflectivity in both phases exhibits long-lived modulations consistent with the sign of the changes that occur upon switching but of smaller magnitude. These can be understood by the generation of acoustic strains with the crystalline phase response dominated by thermal effects and the amorphous phase response associated with electronically induced changes. Evidence for a photo-induced distortion is observed in the amorphous phase which develops homogeneously within the excited region on few-picosecond time scales.

  10. Bipolar resistive switching behavior of an amorphous Ge2Sb2Te5 thin films with a Te layer

    Science.gov (United States)

    Yoo, Sijung; Eom, Taeyong; Gwon, Taehong; Hwang, Cheol Seong

    2015-03-01

    The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (~103) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole-Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (~5 nm) Te-rich layer formed at the bottom electrode interface.

  11. Effect of Sb addition on linear and non-linear optical properties of amorphous Ge-Se-Sn thin films

    Science.gov (United States)

    Sharma, Navjeet; Sharma, Surbhi; Sarin, Amit; Kumar, Rajesh

    2016-01-01

    Optical characterization of amorphous thin films of Ge20Sn10Se70-xSbx (x = 0, 3, 6, 9, 12, 15) has been carried out. Thin films were deposited onto pre cleaned glass substrates using thermal evaporation technique. Transmission spectra of the films were recorded, for normal incidence, in range 400-2400 nm. Refractive index of the films was calculated using the envelope method by Swanepoel. Dispersion analysis has been carried out using single effective oscillator model. Other optical constants such as absorption coefficients, extinction coefficients have also been evaluated. Tauc plots were used to evaluate the optical band gap. The refractive index has been found to be increasing while the band gap decreases with increasing Sb concentration. The observed optical behavior of the films has been explained using chemical bond approach. Cohesive energy is found to be decreasing in the present work, which reflects that bond strength decreases with the increasing content of Sb. Non-linear optical parameters (i.e. n2 and χ(3)) have been derived from linear optical parameters (i.e. n, k, Eg). Observed changes in linear and non-linear parameters have been reported in this study.

  12. Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bong-Sub, E-mail: bongsub@gmail.com; Bogle, Stephanie N.; Darmawikarta, Kristof; Abelson, John R. [Department of Materials Science and Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1-109 Engineering Sciences Building, 1101 West Springfield Avenue, Urbana, Illinois 61801 (United States); Shelby, Robert M.; Retter, Charles T.; Burr, Geoffrey W. [IBM Research—Almaden, 650 Harry Rd., San Jose, California 95120 (United States); Raoux, Simone [IBM Research—Almaden, 650 Harry Rd., San Jose, California 95120 (United States); IBM/Macronix PCRAM Joint Project, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Bishop, Stephen G. [Department of Electrical and Computer Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1406 West Green Street, Urbana, Illinois 61801 (United States)

    2014-02-14

    Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growth speed, which was predicted by theory of phase transformation but rarely demonstrated.

  13. Spectroscopic Properties of Ho3+-DOped Ge-In-Sb-S Glass-Ceramics%HO3+ 杂Ge-In-Sb-S玻璃陶瓷光谱特性

    Institute of Scientific and Technical Information of China (English)

    应磊; 戴世勋; 聂秋华; 林常规; 陈飞飞; 徐铁峰

    2011-01-01

    采用熔融淬冷法和热处理工艺制备了系列掺Ho3+的透明G eS2-In2S3-Sb2S3硫系玻璃陶瓷.测试了Ho3掺杂的基质玻璃和玻璃陶瓷样品的密度、显微硬度、红外光谱以及在900 nm激光泵浦下的近红外及中红外荧光光谱.结果表明:热处理后样品析出的晶相为In2S3和Sb2S3颗粒的混合体,晶粒尺寸限制在~100 nm以内;而原本掺杂在玻璃基质中的Ho3+富集在析出的In2S3晶体周围引起了Ho3+局部浓度的增加.因此,热处理后玻璃陶瓷样品的近红外和中红外荧光强度增加.%Ho3 + -doped chalcogenide glass-ceramics in GeS2-In2S3-Sb2S3 system were prepared by appropriate heat treatment, and their properties including density, microhardness, infrared transmittance spectrum and fluorescence in the near- and mid-infrared region under 900 ran excitation, were measured. The results showed that the crystalline phases in the obtained glass-ceramics were mixture of In2S3 and Sb2S3 with the grain sizes about 100 nm. The Ho3+ , in the host glass network, was aggregated around the In2S3 grains after crystallization processing, which caused the increase of local concentration of Ho3 +. Therefore, the intensities of near- and mid-infrared luminescence in the samples were enhanced.

  14. Effect of tungsten on the phase-change properties of Ge8Sb2Te11 thin films for the phase-change device

    Science.gov (United States)

    Park, Cheol-Jin; Kong, Heon; Lee, Hyun-Yong; Yeo, Jong-Bin

    2017-07-01

    In this study, the electrical, optical, and structural properties of tungsten (W)-doped Ge8Sb2Te11 thin films were investigated. Previously, GeSbTe alloys were doped with various materials in an attempt to improve the thermal stability. Ge8Sb2Te11 and W-doped Ge8Sb2Te11 films with a thickness of 200 nm were fabricated by using an RF magnetron reactive co-sputtering system at room temperature on Si ( p-type, 100) and glass substrate. The fabricated thin films were annealed in a furnace in the 0 - 400 ° C temperature range. The optical properties were analyzed using a UV-Vis-IR spectrophotometer, and by using Beer's Law equation, the optical-energy band gap ( E op ), slope B 1/2, and slope 1/ F were calculated. For the crystalline materials, an increase in the slope B 1/2 and 1/ F was observed, exhibiting a good effect on the thermal stability in the amorphous state after the phase change. The structural properties were analyzed by X-ray diffraction, and the result showed that the W-doped Ge8Sb2Te11 had a face-centered-cubic (fcc) crystalline structure increased crystallization temperature ( T c ). An increase in the T c increased the thermal stability in the amorphous state. The electrical properties were analyzed using a 4-point probe, exhibiting an increase in the sheet resistance ( R s ) in the amorphous and the crystalline states indicating a reduced programming current in the memory device.

  15. First-principles study of new series of quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb)

    Energy Technology Data Exchange (ETDEWEB)

    Bouabça, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Rozale, H., E-mail: hrozale@yahoo.fr [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Amar, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Wang, X.T. [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400044 (China); Sayade, A. [UCCS, CNRS-UMR 8181, Université d’Artois, Faculté des Sciences Jean Perrin, Rue Jean Souvraz, SP 18, 62307 Lens Cedex (France); Chahed, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria)

    2016-12-01

    The structural, electronic, magnetic, and thermal properties of new quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson as the exchange correlation. The results showed that all Heusler compounds were stable in Type (I) structure. The CsSrCZ (Z=Si, Ge, Sn) compounds had a nearly HM characteristic, and CsSrCZ (Z=P, As, Sb) compounds were true half-metallic (HM) ferromagnets. The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. The half-metallicity is preserved up to a lattice contraction of 3.45%, 1.69%, 1.69%, 7.16%, 7.16%, and 11.2% for all six quaternary Heusler compounds. We also investigated the thermal effects using the quasi-harmonic Debye model. - Highlights: • Electronic, magnetic, and thermodynamic properties of CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) are investigated. • Until now, there have been no reports theoretical and experimental studies on d{sup 0} half-metals with quaternary structures. • The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. • The half-metallicity is preserved up to a lattice contraction.

  16. A study on the properties of C-doped Ge8Sb2Te11 thin films during an amorphous-to-crystalline phase transition

    Science.gov (United States)

    Park, Cheol-Jin; Kong, Heon; Lee, Hyun-Yong; Yeo, Jong-Bin

    2016-04-01

    In this work, we evaluated the structural, electrical and optical properties of carbon-doped Ge8Sb2Te11 thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve the thermal stability. Ge8Sb2Te11 and carbon-doped Ge8Sb2Te11 films of 250 nm in thickness were deposited on p-type Si (100) and glass substrates by using a RF magnetron reactive co-sputtering system at room temperature. The fabricated films were annealed in a furnance in the 0 ~ 400°C temperature range. The structural properties were analyzed by using X-ray diffraction (XRD), and the result showed that the carbon-doped Ge8Sb2Te11 had a face-centeredcubic (fcc) crystalline structure and an increased crystallization temperature ( T c ). An increase in the T c leads to thermal stability in the amorphous state. The optical properties were analyzed by using an UV-Vis-IR spectrophotometer, and the result showed an increase in the optical-energy band gap ( E op ) in the crystalline materials and an increase in the E op difference (Δ E op ), which is a good effect for reducing the noise in the memory device. The electrical properties were analyzed by using a 4-point probe, which showed an increase in the sheet resistance ( R s ) in the amorphous state and the crystalline state, which means a reduced programming current in the memory device.

  17. Gd4Ge(3-x)Pn(x) (Pn = P, Sb, Bi, x = 0.5-3): stabilizing the nonexisting Gd4Ge3 binary through valence electron concentration. Electronic and magnetic properties of Gd4Ge(3-x)Pn(x).

    Science.gov (United States)

    Cheung, Yan Yin Janice; Svitlyk, Volodymyr; Mozharivskyj, Yurij

    2012-10-01

    Gd(4)Ge(3-x)Pn(x) (Pn = P, Sb, Bi; x = 0.5-3) phases have been prepared and characterized using X-ray diffraction, wavelength-dispersive spectroscopy, and magnetization measurements. All Gd(4)Ge(3-x)Pn(x) phases adopt a cubic anti-Th(3)P(4) structure, and no deficiency on the Gd or p-element site could be detected. Only one P-containing phase with the Gd(4)Ge(2.51(5))P(0.49(5)) composition could be obtained, as larger substitution levels did not yield the phase. Existence of Gd(4)Ge(2.51(5))P(0.49(5)) and Gd(4)Ge(2.49(3))Bi(0.51(3)) suggests that the hypothetical Gd(4)Ge(3) binary can be easily stabilized by a small increase in the valence electron count and that the size of the p element is not a key factor. Electronic structure calculations reveal that large substitution levels with more electron-rich Sb and Bi are possible for charge-balanced (Gd(3+))(4)(Ge(4-))(3) as extra electrons occupy the bonding Gd-Gd and Gd-Ge states. This analysis also supports the stability of Gd(4)Sb(3) and Gd(4)Bi(3). All Gd(4)Ge(3-x)Pn(x) phases order ferromagnetically with relatively high Curie temperatures of 234-356 K. The variation in the Curie temperatures of the Gd(4)Ge(3-x)Sb(x) and Gd(4)Ge(3-x)Bi(x) series can be explained through the changes in the numbers of conduction electrons associated with Ge/Sb(Bi) substitution.

  18. Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge -V -Te (V =As , Sb) Liquid Alloys: The Difference One Element Can Make

    Science.gov (United States)

    Wei, Shuai; Coleman, Garrett J.; Lucas, Pierre; Angell, C. Austen

    2017-03-01

    Glass-transition temperatures (Tg ) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of Tg vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e., in the order S ambient pressure) melting point.

  19. Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

    Science.gov (United States)

    Sun, Xinxing; Ehrhardt, Martin; Lotnyk, Andriy; Lorenz, Pierre; Thelander, Erik; Gerlach, Jürgen W.; Smausz, Tomi; Decker, Ulrich; Rauschenbach, Bernd

    2016-01-01

    The amorphous to crystalline phase transformation of Ge2Sb2Te5 (GST) films by UV nanosecond (ns) and femtosecond (fs) single laser pulse irradiation at the same wavelength is compared. Detailed structural information about the phase transformation is collected by x-ray diffraction and high resolution transmission electron microscopy (TEM). The threshold fluences to induce crystallization are determined for both pulse lengths. A large difference between ns and fs pulse irradiation was found regarding the grain size distribution and morphology of the crystallized films. For fs single pulse irradiated GST thin films, columnar grains with a diameter of 20 to 60 nm were obtained as evidenced by cross-sectional TEM analysis. The local atomic arrangement was investigated by high-resolution Cs-corrected scanning TEM. Neither tetrahedral nor off-octahedral positions of Ge-atoms could be observed in the largely defect-free grains. A high optical reflectivity contrast (~25%) between amorphous and completely crystallized GST films was achieved by fs laser irradiation induced at fluences between 13 and 16 mJ/cm2 and by ns laser irradiation induced at fluences between 67 and 130 mJ/cm2. Finally, the fluence dependent increase of the reflectivity is discussed in terms of each photon involved into the crystallization process for ns and fs pulses, respectively. PMID:27292819

  20. Structural transformations in Ge{sub 2}Sb{sub 2}Te{sub 5} under high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Mio, A. M.; Privitera, S., E-mail: stefania.privitera@imm.cnr.it; D' Arrigo, G.; Rimini, E. [IMM-CNR, Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, Strada VIII 5, Zona Industriale, I-95121 Catania (Italy); Ceppatelli, M. [ICCOM-CNR, Istituto di Chimica dei Composti OrganoMetallici, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino (Italy); Gorelli, F.; Santoro, M. [LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino (Italy); INO-CNR, Istituto Nazionale di Ottica, Via Nello Carrara 1, I-50019 Sesto Fiorentino (Italy); Miritello, M. [MATIS-IMM-CNR, via S. Sofia 64, I-95123 Catania (Italy); Bini, R. [LENS, European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino (Italy); Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Italy)

    2015-08-14

    The structural transformations occurring in Ge{sub 2}Sb{sub 2}Te{sub 5} films heated at temperature up to 400 °C, and under hydrostatic pressure up to 12 GPa, have been investigated through in-situ X ray diffraction measurements. The adopted experimental conditions are close to those experienced by the phase change material during the SET (crystallization)/RESET (amorphization) processes in a nonvolatile memory device. The compression enhances the thermal stability of the amorphous phase, which remains stable up to 180 °C at 8 GPa and to 230 °C at 12 GPa. The structure of the crystalline phases is also modified, with the formation of a CsCl-type structure instead of rock-salt and of a GeS-type structure at the temperature at which usually the trigonal stable phase is formed. Overall, the stability of the stable phase appears to be more affected by the compression. We argue that the presence of weak bonds associated to the van der Waals gaps is a determining factor for the observed reduced stability.

  1. The correlation of electrical conductivity with the microstructure of Ge2Sb2Te5 thin films alloyed with Sn

    Science.gov (United States)

    Yin, Qixun; Chen, Leng

    2017-01-01

    In this research, the effects of Sn alloying on structure transformation and electrical characteristics of Ge2Sb2Te5 (GST) thin films were studied. It was discovered that the SnTe phase formed in GST thin films when Sn content exceeded 26 at%, and the addition of Sn atoms expanded the lattice parameter, as a result of atomic radii difference between Ge and Sn atoms. Furthermore, temperature dependent sheet resistance measurements on the GST:Sn thin films were performed for the electrical characteristics to be studied. Sn substitution fraction of 16 at% was discovered to maximize the crystallization temperature of GST thin films. Compared to the GST thin films, crystallization temperature difference and lower amorphous resistance of the GST:Sn thin films were mainly due to lower bonding energy of Sn–Te. Moreover, the amorphous conductivity activation energies (E σ) corresponding to different grain sizes were calculated with the Arrhenius equation. The E σ value of GST:Sn thin films decreased significantly as the Sn content increased due to grain size effects, which appears to improve the temperature stability of conductivity of phase change memory.

  2. Investigation of basic physical properties and dielectric behavior of a-Se-Sn-Ge-Sb system

    Science.gov (United States)

    Chaudhary, Shobhna; Modgil, Vivek; Nidhi, Anant Vidya; Kumar, Prashant; Rangra, V. S.

    2015-05-01

    The material is investigated for various physical parameters which gives us the formation about glass rigidity and glass forming ability. The cohesive energy has been interpreted using Chemical Bond Approach and glass transition temperature (Tg) has been calculated by using Tichy-Ticha approach. The decrease in glass transition temperature and weakening of structure of the material has been observed due to decrease in mean bond energy. The effect of Sb addition on the dielectric behavior of a bulk glassy material has also been studied at room temperature in the frequency range 20Hz to 1MHz.

  3. Site preference and electronic structure of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb: a theoretical study

    Directory of Open Access Journals (Sweden)

    Ren Zhi

    2016-06-01

    Full Text Available The electronic structure and magnetism of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb Heusler alloys have been studied by using first-principles calculations. Three half-metallic ferromagnets, namely, Mn2RhAl, Mn2RhGe and Mn2RhSb have been considered. The calculated equilibrium lattice constant increases with increasing atomic number of Z atoms lying in same column of periodic table. The calculated total magnetic moments Mtot are 2 µB/f.u. for Mn2RhAl and Mn2RhGa, 3 µB/f.u. for Mn2RhSi, Mn2RhGe and Mn2RhSn, and 4 µB/f.u. for Mn2RhSb, which agrees with the Slater-Pauling curve quite well. In all these compounds, except for Mn2RhSb, the moments of Mn (A and Mn (B are antiparallel to each other. The total magnetic moments of the three considered half-metals assume integral values in a wide range of equilibrium lattice parameters.

  4. Ge20Sb15Se65薄膜的热致光学特性变化研究*%Thermal-induced optical changes in the amorphous Ge20Sb15Se65 film∗

    Institute of Scientific and Technical Information of China (English)

    宗双飞; 沈祥; 徐铁峰; 陈昱; 王国祥; 陈芬; 李军; 林常规; 聂秋华

    2013-01-01

    The amorphous Ge20Sb15Se65 thin film was prepared by magnetron sputtering deposition technique. Effect of heat treatment temperature in the range of 150—400◦C on the optical properties of Ge20Sb15Se65 thin films has been investigated. The microstructure and optical properties of the films were characterized by UV-Vis, Raman spectroscopy and XRD, the optical constant was calculated using the Swanepoel method and Tauc’s law from the optical transmission spectra. Results indicate that when the annealing temperature (Ta) is lower than the glass transition temperature (Tg), the optical band gap (Eoptg ) increases from 1.845 to 1.932 eV, and the refractive index decreases from 2.61 to 2.54, while the optical band gap decreases from 1.932 to 1.822 eV and the refractive index increases from 2.54 to 2.71 with a further increase of Ta. The results were explained in terms of the Mott and Davis model for amorphous materials and amorphous to crystalline structural transformations. It is well consistent with the results of structure analysis by XRD and Raman spectroscopy.%  采用磁控溅射法制备了Ge20Sb15Se65薄膜,研究热处理温度(150-400◦C)对薄膜光学特性的影响.通过分光光度计、X射线衍射仪、显微拉曼光谱仪对热处理前后薄膜样品的光学特性和微观结构进行了表征,并根据Swanepoel方法以及Tauc公式分别计算了薄膜折射率色散曲线和光学带隙等参数.结果表明当退火温度(Ta)小于薄膜的玻璃转化温度(Tg)时,薄膜的光学带隙(Eoptg )随着退火温度的增加由1.845 eV上升至1.932 eV,而折射率由2.61降至2.54;当退火温度大于薄膜的玻璃转化温度时,薄膜的光学带隙随退火温度的增加由1.932 eV降至1.822 eV,折射率则由2.54增至2.71.最后利用Mott和Davis提出的非晶材料由非晶到晶态的结构转变模型对结果进行了解释,并通过薄膜XRD和Raman光谱进一步验证了结构变化是薄膜热致变化的重要原因.

  5. The lower-valence coexisting ferrimagnetic Cr{sub 2}VX (X = Ga, Si, Ge, Sb) Heusler compounds: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Li Jia [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)], E-mail: jiali@mail.hebut.edu.cn; Chen Guifeng; Li Jianfeng [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li Yangxian [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)], E-mail: admat@jsmail.hebut.edu.cn; Sun, Chang Q. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2008-11-15

    First-principles investigation of the Heusler compounds Cr{sub 2}VX (X = Ga, Si, Ge, Sb) revealed that the Cr{sub 2}VSb exhibits a half-metallic nature yet Cr{sub 2}VSi and Cr{sub 2}VGe show nearly half-metallic ferromagnetism. Their band structures show a striking difference between the majority and minority spin directions. The Cr-V covalence bonding strength increases in the Ga {yields} Si {yields} Sb direction, with the d-d and p-d gaps developing gradually. The V atom shows a larger moment, of around 2.0 {mu}{sub B}, than previously reported values.

  6. Molecular beam epitaxy of GeTe-Sb{sub 2}Te{sub 3} phase change materials studied by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Shayduk, Roman

    2010-05-20

    The integration of phase change materials into semiconductor heterostructures may lead to the development of a new generation of high density non-volatile phase change memories. Epitaxial phase change materials allow to study the detailed structural changes during the phase transition and to determine the scaling limits of the memory. This work is dedicated to the epitaxial growth of Ge-Sb-Te phase change alloys on GaSb(001). We deposit Ge-Sb-Te (GST) films on GaSb(001) substrates by means of molecular beam epitaxy (MBE). The film orientation and lattice constant evolution is determined in real time during growth using grazing incidence X-ray diffraction (GID). The nucleation stage of the growth is studied in situ using reflection high energy electron diffraction (RHEED). Four growth regimes of GST on GaSb(001) were observed: amorphous, polycrystalline, incubated epitaxial and direct epitaxial. Amorphous film grows for substrate temperatures below 100 C. For substrate temperatures in the range 100-160 C, the film grows in polycrystalline form. Incubated epitaxial growth is observed at temperatures from 180 to 210 C. This growth regime is characterized by an initial 0.6nm thick amorphous layer formation, which crystallizes epitaxially as the film thickness increases. The determined lattice constant of the films is 6.01 A, very close to that of the metastable GST phase. The films predominantly possess an epitaxial cube-on-cube relationship. At higher temperatures the films grow epitaxially, however the growth rate is rapidly decreasing with temperature. At temperatures above 270 C the growth rate is zero. The composition of the grown films is close to 2:2:5 for Ge, Sb and Te, respectively. The determined crystal structure of the films is face centered cubic (FCC) with a rhombohedral distortion. The analysis of X-ray peak widths gives a value for the rhombohedral angle of 89.56 . We observe two types of reflections in reciprocal space indicating two FCC sublattices in

  7. Modeling of switching mechanism in GeSbTe chalcogenide superlattices

    Science.gov (United States)

    Yu, Xiaoming; Robertson, John

    2015-07-01

    We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.

  8. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Guangfei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, Simian [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Huang, Huan [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Yang, E-mail: ywang@siom.ac.cn [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Wu, Yiqun [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (GeSbTe) and Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  9. Research and Development of Chemical Mechanical Planarization for Ge2Sb2Te5%Ge2Sb2Te5的化学机械抛光研究进展

    Institute of Scientific and Technical Information of China (English)

    何敖东; 刘波; 宋志棠; 冯高明; 朱南飞; 任佳栋; 吴关平; 封松林

    2013-01-01

    相变存储器由于具有非易失性、高速度、低功耗等优点被认为最有可能成为下一代存储器的主流产品,Ge2Sb2Te5 (GST)作为一种传统相变材料已经被广泛应用在相变存储器中,而GST的化学机械抛光作为相变存储器生产的关键工艺目前已被采用.本工作综述了有关GST的化学机械抛光技术研究进展,讨论了GST化学机械抛光过程的影响因素,如下压力、转速、抛光垫、磨料、氧化剂、表面活性剂等,并对目前GST的化学机械抛光机理进行了归纳,进一步展望了GST的化学机械抛光技术的发展前景.%Phase change memory (PCM) is considered a major candidate for next-generation memory due to its nonvolatile,fast program access times,low consumable power.So far chalcogenide Ge2Sb2Te5 (GST),as a traditional phase material,has been widely adopted and investigated for PCM application.Recently,chemical mechanical planarization (CMP) of GST as a key technique for confined structure has been applied in the fabrication of PCM.In this paper,research and development of CMP for GST is reviewed firstly and the impact factors of down force,rotation velocity,polishing pads,and the slurry on the GST CMP are discussed.For the mechanical parameter,the removal rate (RR) of GST increases with the increasing of pressure and rotation velocity firstly,and then reaches saturation or slightly decreases.The gentle mechanical parameter is a better choice for GST CMP due to its lower hardness.With regard to polishing pads,GST polished using Politex reg can attain a better surface quality,and almost no residue and scratches can be found,compared with IC1010.The oxidizer of slurry,such as H2O2,(NH4)2S2O8,KMnO4 and FeCl3 have a great influence on the GST performance,the oxidization capacity of each element in GST alloy is different.Among these elements,Ge is preferentially oxidized,but Te is hard oxidized due to their different electronegativity.RR strongly depends on the p

  10. Structure of and phase transformations in bulk amorphous (GaSb) sub 1 sub - sub x (Ge sub 2) sub x

    CERN Document Server

    Sapelkin, A V

    1997-01-01

    temperatures, under high pressures and at ambient conditions. Combined EXAFS and powder diffraction methods have been used to study the high pressure behavior of materials. The results revealed a complex picture of structural transformations in (GaSb) sub 1 sub - sub x (Ge sub 2) sub x owing to the meta-stable nature of samples. The semiconductor-to-metal transition observed previously is found to be due to percolation through the high pressure metallic phase GaSb II. It is showed that the combination of two structural techniques, powder diffraction and EXAFS, can provide quite detailed information on the structural behavior of amorphous materials under high pressures. The temperature-dependent EXAFS studies showed that semiconducting amorphous GaSb is likely to be chemically ordered. Issues concerning determination of the structure of amorphous materials and information theory are widely discussed. Amorphous materials are not new to scientists and mankind -- man has been using glass and glassy materials for ...

  11. Structural, electronic and kinetic properties of the phase-change material Ge2Sb2Te5 in the liquid state

    Science.gov (United States)

    Schumacher, Mathias; Weber, Hans; Jóvári, Pál; Tsuchiya, Yoshimi; Youngs, Tristan G. A.; Kaban, Ivan; Mazzarello, Riccardo

    2016-06-01

    Phase-change materials exhibit fast and reversible transitions between an amorphous and a crystalline state at high temperature. The two states display resistivity contrast, which is exploited in phase-change memory devices. The technologically most important family of phase-change materials consists of Ge-Sb-Te alloys. In this work, we investigate the structural, electronic and kinetic properties of liquid Ge2Sb2Te5 as a function of temperature by a combined experimental and computational approach. Understanding the properties of this phase is important to clarify the amorphization and crystallization processes. We show that the structural properties of the models obtained from ab initio and reverse Monte Carlo simulations are in good agreement with neutron and X-ray diffraction experiments. We extract the kinetic coefficients from the molecular dynamics trajectories and determine the activation energy for viscosity. The obtained value is shown to be fully compatible with our viscosity measurements.

  12. Logic gates realized by nonvolatile GeTe/Sb2Te3 super lattice phase-change memory with a magnetic field input

    Science.gov (United States)

    Lu, Bin; Cheng, Xiaomin; Feng, Jinlong; Guan, Xiawei; Miao, Xiangshui

    2016-07-01

    Nonvolatile memory devices or circuits that can implement both storage and calculation are a crucial requirement for the efficiency improvement of modern computer. In this work, we realize logic functions by using [GeTe/Sb2Te3]n super lattice phase change memory (PCM) cell in which higher threshold voltage is needed for phase change with a magnetic field applied. First, the [GeTe/Sb2Te3]n super lattice cells were fabricated and the R-V curve was measured. Then we designed the logic circuits with the super lattice PCM cell verified by HSPICE simulation and experiments. Seven basic logic functions are first demonstrated in this letter; then several multi-input logic gates are presented. The proposed logic devices offer the advantages of simple structures and low power consumption, indicating that the super lattice PCM has the potential in the future nonvolatile central processing unit design, facilitating the development of massive parallel computing architecture.

  13. All-optical switching of localized surface plasmon resonance in single gold nanosandwich using GeSbTe film as an active medium

    Science.gov (United States)

    Hira, T.; Homma, T.; Uchiyama, T.; Kuwamura, K.; Kihara, Y.; Saiki, T.

    2015-01-01

    Localized surface plasmon resonance (LSPR) switching was investigated in a Au/GeSbTe/Au nanosandwich as a key active element for plasmonic integrated circuits and devices. Near-infrared single-particle spectroscopy was conducted to examine the interaction of a Au nanorod (AuNR) and Au film, between which a GeSbTe layer was incorporated as an active phase-change media. Numerical calculation revealed that hybridized modes of the AuNR and Au film exhibit a significant change of scattering intensity with the phase change. In particular, the antisymmetric (magnetic resonance) mode can be modulated effectively by the extinction coefficient of GST, as well as its refractive index. Experimental demonstration of the switching operation was performed by alternate irradiation with a picosecond pulsed laser for amorphization and a continuous wave laser for crystallization. Repeatable modulation was obtained by monitoring the scattering light around the LSPR peak at λ = 1070 nm.

  14. All-optical switching of localized surface plasmon resonance in single gold nanosandwich using GeSbTe film as an active medium

    Energy Technology Data Exchange (ETDEWEB)

    Hira, T.; Homma, T.; Uchiyama, T.; Kuwamura, K.; Kihara, Y.; Saiki, T. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama, Kanagawa 223-8522 (Japan)

    2015-01-19

    Localized surface plasmon resonance (LSPR) switching was investigated in a Au/GeSbTe/Au nanosandwich as a key active element for plasmonic integrated circuits and devices. Near-infrared single-particle spectroscopy was conducted to examine the interaction of a Au nanorod (AuNR) and Au film, between which a GeSbTe layer was incorporated as an active phase-change media. Numerical calculation revealed that hybridized modes of the AuNR and Au film exhibit a significant change of scattering intensity with the phase change. In particular, the antisymmetric (magnetic resonance) mode can be modulated effectively by the extinction coefficient of GST, as well as its refractive index. Experimental demonstration of the switching operation was performed by alternate irradiation with a picosecond pulsed laser for amorphization and a continuous wave laser for crystallization. Repeatable modulation was obtained by monitoring the scattering light around the LSPR peak at λ = 1070 nm.

  15. Effect of ion irradiation on the stability of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

    Energy Technology Data Exchange (ETDEWEB)

    De Bastiani, R. [Dipartimento di Fisica e Astronomia, Universita di Catania and MATIS CNR-INFM, Via S. Sofia 64, I-95123 Catania (Italy)], E-mail: riccardo.debastiani@ct.infn.it; Piro, A.M.; Crupi, I.; Grimaldi, M.G. [Dipartimento di Fisica e Astronomia, Universita di Catania and MATIS CNR-INFM, Via S. Sofia 64, I-95123 Catania (Italy); Rimini, E. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), Stradale Primosole 50, I-95121 Catania (Italy)

    2008-05-15

    The archival life of phase-change memories (PCM) is determined by the thermal stability of amorphous phase in a crystalline matrix. In this paper, we report the effect of ion beam irradiation on the crystallization kinetics of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} alloy (GST). The transition rate of amorphous GST films was measured by in situ time resolved reflectivity (TRR). The amorphous to crystal transformation time decreases considerably in irradiated amorphous GST samples when ion fluence increases. The stability of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films subjected to ion irradiation is discussed in terms of the free energy variation of the amorphous state because of damage accumulation.

  16. Preferred orientation of nanoscale order at the surface of amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} films

    Energy Technology Data Exchange (ETDEWEB)

    Tony Li, Tian; Abelson, John R. [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, Illinois 61801 (United States); Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1308 W. Main St., Urbana, Illinois 61801 (United States); Hoon Lee, Tae; Elliott, Stephen R. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

    2013-11-11

    We report evidence that as-deposited amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films contain nanoscale clusters that exhibit a preferred orientation, attributed to the earliest stages of heterogeneous nucleation. Fluctuation transmission electron microscopy reveals structural order in the samples, but (220)-related contributions are suppressed. When homogeneous nucleation is promoted via electron bombardment, the sample remains diffraction amorphous but the (220) contribution appears. We simulated data for randomly oriented nanoscale order using ab initio molecular-dynamics models of Ge{sub 2}Sb{sub 2}Te{sub 5}. The simulated (220) contribution always has larger magnitude than higher-order signals; thus, the lack of the experimental signal indicates a significant preferred orientation.

  17. SbGeO3.5作为锂离子电池负极材料的研究

    Institute of Scientific and Technical Information of China (English)

    吕成学; 褚嘉宜; 翟玉春; 田彦文

    2004-01-01

    采用共沉淀法制备了SbGeO3.5氧化物粉末。XRD分析表明,这种氧化物的谱峰与JCPDS卡片(No.46-0425)完全一致,证明采用此法可得到纯的SbGeO3.5化合物。SEM的形貌观察发现,SbGeO3.5晶粒呈立方三角形,晶粒粒径平均约为2.5μm。将其作为锂离子电池负极材料的活性物质,利用恒电流电池测试仪研究其电化学性能发现,以SbGeO3.5为活性物质的电极的嵌/脱锂平台在0.25V和0.5V左右;这种氧化物具有较高的电化学容量,其首次嵌锂反应的可逆容量为950mAh/g。其电化学容量远远高于碳材料(石墨的理论容量为327mAh/g),因此,这种氧化物可以作为锂离子电池负极材料的候选材料。

  18. Morphology and Electric Conductance Change Induced by Voltage Pulse Excitation in (GeTe)2/Sb2Te3 Superlattices

    Science.gov (United States)

    Bolotov, Leonid; Saito, Yuta; Tada, Tetsuya; Tominaga, Junji

    2016-09-01

    Chalcogenide superlattice (SL) phase-change memory materials are leading candidates for non-volatile, energy-efficient electric memory where the electric conductance switching is caused by the atom repositioning in the constituent layers. Here, we study the time evolution of the electric conductance in [(GeTe)2/(Sb2Te3)1]4 SLs upon the application of an external pulsed electric field by analysing the structural and electrical responses of the SL films with scanning probe microscopy (SPM) and scanning probe lithography (SPL). At a low pulse voltage (1.6-2.3 V), a conductance switching delay of a few seconds was observed in some SL areas, where the switch to the high conductance state (HCS) is accompanied with an SL expansion under the strong electric field of the SPM probe. At a high pulse voltage (2.5-3.0 V), the HCS current was unstable and decayed in a few seconds; this is ascribed to the degradation of the HCS crystal phase under excessive heating. The reversible conductance change under a pulse voltage of opposite polarity emphasised the role of the electric field in the phase-transition mechanism.

  19. Iron trichloride as oxidizer in acid slurry for chemical mechanical polishing of Ge2Sb2Te5

    Science.gov (United States)

    Yan, Wei-Xia; Wang, Liang-Yong; Zhang, Ze-Fang; Liu, Wei-Li; Song, Zhi-Tang

    2014-04-01

    The effect of iron trichloride (FeCl3) on chemical mechanical polishing (CMP) of Ge2Sb2Te5 (GST) film is investigated in this paper. The polishing rate of GST increases from 38 nm/min to 144 nm/min when the FeCl3 concentration changes from 0.01 wt% to 0.15 wt%, which is much faster than 20 nm/min for the 1 wt% H2O2-based slurry. This polishing rate trends are inversely correlated with the contact angle data of FeCl3-based slurry on the GST film surface. Thus, it is hypothesized that the hydrophilicity of the GST film surface is associated with the polishing rate during CMP. Atomic force microscope (AFM) and optical microscope (OM) are used to characterize the surface quality after CMP. The chemical mechanism is studied by potentiodynamic measurements such as Ecorr and Icorr to analyze chemical reaction between FeCl3 and GST surface. Finally, it is verified that slurry with FeCl3 has no influence on the electrical property of the post-CMP GST film by the resistivity-temperature (RT) tests.

  20. Pair potential modeling of atomic rearrangement in GeTe-Sb2Te3 superlattice via first-principles calculations

    Science.gov (United States)

    Song, Young-Sun; Kim, Jeongwoo; Jhi, Seung-Hoon

    2017-03-01

    We study the nature of atomic rearrangement during the phase-change processes in the superlattice of GeTe and Sb2Te3 by developing a new approach combining the first-principles calculations and a pair-potential model. We investigate the phase-change process in terms of energy changes from individual pairs or atoms by applying the pair (atom)-projection analysis to the intermediate structures between the initial and final states obtained from the climbing-image nudged elastic band method. Among the prototypical steps that can lead to the atomic layer rearrangement, we find that the required energy for the phase change is dominated by specific atoms responsible for the intrinsic energy barrier and the response to external pressure. Our approach of combining the first-principles methods and pair potential model with the projecting analysis can be a very efficient method in revealing the detailed atomic motions and the mechanism of fast atomic transition of the phase-change materials.

  1. Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials.

    Science.gov (United States)

    Kalkan, B; Sen, S; Clark, S M

    2011-09-28

    The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge(1)Sb(2)Te(4) (GST124) phase change materials as a function of pressure and temperature using high-resolution synchrotron x-ray diffraction in a diamond anvil cell. The phase transformation sequences upon compression, for cubic and hexagonal GST124 phases are found to be: cubic → amorphous → orthorhombic → bcc and hexagonal → orthorhombic → bcc. The Clapeyron slopes for melting of the hexagonal and bcc phases are negative and positive, respectively, resulting in a pressure dependent minimum in the liquidus. When taken together, the phase equilibria relations are consistent with the presence of polyamorphism in this system with the as-deposited amorphous GST phase being the low entropy low-density amorphous phase and the laser melt-quenched and high-pressure amorphized GST being the high entropy high-density amorphous phase. The metastable phase boundary between these two polyamorphic phases is expected to have a negative Clapeyron slope. © 2011 American Institute of Physics

  2. Morphology and Electric Conductance Change Induced by Voltage Pulse Excitation in (GeTe)2/Sb2Te3 Superlattices

    Science.gov (United States)

    Bolotov, Leonid; Saito, Yuta; Tada, Tetsuya; Tominaga, Junji

    2016-01-01

    Chalcogenide superlattice (SL) phase-change memory materials are leading candidates for non-volatile, energy-efficient electric memory where the electric conductance switching is caused by the atom repositioning in the constituent layers. Here, we study the time evolution of the electric conductance in [(GeTe)2/(Sb2Te3)1]4 SLs upon the application of an external pulsed electric field by analysing the structural and electrical responses of the SL films with scanning probe microscopy (SPM) and scanning probe lithography (SPL). At a low pulse voltage (1.6–2.3 V), a conductance switching delay of a few seconds was observed in some SL areas, where the switch to the high conductance state (HCS) is accompanied with an SL expansion under the strong electric field of the SPM probe. At a high pulse voltage (2.5–3.0 V), the HCS current was unstable and decayed in a few seconds; this is ascribed to the degradation of the HCS crystal phase under excessive heating. The reversible conductance change under a pulse voltage of opposite polarity emphasised the role of the electric field in the phase-transition mechanism. PMID:27618797

  3. Characterizations and thermal stability improvement of phase-change memory device containing Ce-doped GeSbTe films

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yu-Jen; Tsai, Min-Chuan; Wang, Chiung-Hsin; Hsieh, Tsung-Eong, E-mail: tehsieh@mail.nctu.edu.tw

    2012-02-29

    Phase-transition temperature of GeSbTe (GST) chalcogenide film was drastically increased from 159 to 236 Degree-Sign C by cerium (Ce) doping (up to 8.6 at.%) without altering the resistivity property of GST. Grain refinement via the solid-solution mechanism and the amplification of p-type semiconducting behavior in Ce-doped GST were observed. They were correlated with the enhancement of thermal stability and data retention property of GST as revealed by exothermal and isothermal analyses. Phase-change memory (PCM) device characterized at various temperatures revealed an effective thermal stability improvement on the threshold voltage of PCM device by Ce doping. - Highlights: Black-Right-Pointing-Pointer Ce doping increased phase-change temperature of GST from 159 to 236 Degree-Sign C. Black-Right-Pointing-Pointer No suppression of resistivity level in amorphous Ce-doped GST. Black-Right-Pointing-Pointer Resistance ratio of amorphous and crystalline Ce-doped GST was preserved at 10{sup 5}. Black-Right-Pointing-Pointer p-type semiconducting behavior of GST was enhanced by Ce-doping. Black-Right-Pointing-Pointer Ce-doping improved the thermal stability of threshold voltage of GST PCM device.

  4. Conductive Atomic Force Microscopy (C-AFM) observation of conducting nanofilaments formation in GeSbTe phase change materials

    Science.gov (United States)

    Yang, Fei; Xu, Ling; Fang, Li; Jiang, Yifan; Xu, Jun; Su, Weining; Yu, Yao; Ma, Zhongyuan; Chen, Kunji

    2013-09-01

    GST (GeSbTe) thin films were deposited on glass substrates by electron beam evaporation; Ni was used as the top and bottom electrodes. The I- V (current-voltage) characteristic of the phase change memory (PCM) cell was measured; results showed an electrical threshold switching characteristic for the sample with a threshold voltage of 3.08 V. The threshold switching is attributed to the formation of conductive filaments in the amorphous matrix. Current-voltage spectra which were obtained by C-AFM show that the GST thin film switching from amorphous to the crystalline phase occurs at 1.51 V. C-AFM was used to fabricate crystalline nanoarrays on the sample surface and examine the electrical properties of arrays. In the I- V measurements by C-AFM, when the applied voltage is higher than threshold voltage, conducting nanofilaments with average sizes of 15-60 nm were formed and crystallized spots with current signals were observed. Different times of I- V spectroscopies were applied on thin films to investigate the electrical properties of films during the phase change process. C-AFM results show that as the times of I- V spectroscopies increased, the morphology of crystallized spots changed from bump to pit; the sizes of conductive nanofilaments and detected current signals increased. These results can be attributed to the energy induced by Joule heating dissipated to surrounding films increases with the increasing times of I- V spectroscopies.

  5. Ge-Sb-Se glass fiber-optics for in-vivo mid-infrared optical biopsy

    Science.gov (United States)

    Parnell, H.; Butterworth, J. H.; Sakr, H.; Tang, Z.; Furniss, D.; Benson, T. M.; Scotchford, C.; Seddon, A. B.

    2016-03-01

    In the UK, it is now recognised that 1 in 2 people born after 1960 will develop some form of cancer during their lifetime. Diagnosing patients whilst in the early stages drastically improves their chances of survival but up until now the gold standard for cancer detection is via a lengthy excision biopsy procedure, which relies on the skill of a histopathologist. Evidently, the need for a faster solution is paramount. The mid-infrared (MIR) spectral region covers the wavelengths 3-25 μm and characteristic vibrational spectra unique to each molecular type. Subtle changes in the specific spectral response within this region are indicative of changes within the cells relative to normal cells, signifying the presence or absence of a disease. Our goal is to carry out disease diagnosis in vivo. Reaching these wavelengths has previously presented difficulties as conventional MIR blackbody light sources are weak and optical fibers for transmitting MIR light to/from tissue in vivo can be limited by strong material absorption such as silica glass >2.4 μm and tellurite, and heavy metal fluoride, >4.75 μm. However, chalcogenide glasses have been shown to transmit MIR light out to 25 μm. This paper reports on a glass composition in the Ge-Sb-Se system and its suitability as an optical fiber for the transmission of MIR to and from tissue samples, enabling in vivo mapping for an immediate diagnostic response- a technique termed `optical biopsy'.

  6. Filled Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) Skutterudites: Processing and Thermoelectric Properties

    Science.gov (United States)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2016-01-01

    Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) system has been investigated as a p-type thermoelectric material, and is stable up to 600 C. The influence of Fe and Ge content, along with filler Nd, was investigated on thermoelectric transport properties. In addition to the chemical influence on properties, some processing details of the system will also be addressed.

  7. Filled Nd(sub z) Fe(sub x) Co(sub 4-x) Sb(sub 12-y) Ge(sub y) Skutterudites: Processing and Thermoelectric Properties

    Science.gov (United States)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2016-01-01

    Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Nd (sub z) Fe (sub x) Co (sub 4-x) Sb (sub 12-y)Ge (sub y) system has been investigated as a p-type thermoelectric material, and is stable up to 600 degrees Centigrade. The influence of Fe and Ge content, along with filler Nd, was investigated on thermoelectric transport properties. In addition to the chemical influence on properties, some processing details of the system will also be addressed.

  8. Chemical mechanical planarization of amorphous Ge2Sb2Te5 using KClO4 as oxidizer in acidic slurry

    Science.gov (United States)

    He, Aodong; Song, Zhitang; Bo, Liu; Zhong, Min; Weili, Liu; Wang, Liangyong; Yan, Weixia; Lei, Yu; Wu, Guangping

    Amorphous Ge2Sb2Te5 (a-GST) chemical mechanical planarization (CMP) using KClO4 as the oxidizer in an acidicslurry is investigated in the present work. It is shown that the removal rate (RR ) of the a-GST firstly increases and thentends to saturate when the KClO4 concentration is greater than 0.8 wt%, but the static etch rate (SER) linearly increasesfrom low to high KClO4 concentration. To understand the oxidation-reaction capability of Ge, Sb and Te, depth profilesof composition of elements and etch morphology of a-GST immersed in the slurry for some time are measured,respectively. It is found that selective corrosion occurs among Ge, Sb and Te, and an accumulation of Te and loss of Gein a-GST surface region are obvious observed, especially at high KClO4 concentrations. Temperature dependent sheetresistance measurements of all the samples pre- and post-CMP reveal a similar trend, which implies a-GST CMP is ableto keep its characteristic well.

  9. Work function contrast and energy band modulation between amorphous and crystalline Ge{sub 2}Sb{sub 2}Te{sub 5} films

    Energy Technology Data Exchange (ETDEWEB)

    Tong, H.; Yang, Z.; Yu, N. N.; Zhou, L. J.; Miao, X. S., E-mail: miaoxs@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-08-24

    The work function (WF) is of crucial importance to dominate the carrier transport properties of the Ge-Sb-Te based interfaces. In this letter, the electrostatic force microscopy is proposed to extract the WF of Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) films with high spatial and energy resolution. The measured WF of as-deposited amorphous GST is 5.34 eV and decreases drastically after the amorphous GST is crystallized by annealing or laser illumination. A 512 × 512 array 2D-WF map is designed to study the WF spatial distribution and shows a good consistency. The WF contrast between a-GST and c-GST is ascribed to band modulation, especially the modification of electron affinity including the contribution of charges or dipoles. Then, the band alignments of GST/n-Si heterostructures are obtained based on the Anderson's rule. Due to the band modulation, the I-V characteristics of a-GST/Si heterojunction and c-GST/Si heterojunction are very different from each other. The quantitative relationship is calculated by solving the Poisson's equation, which agrees well with the I-V measurements. Our findings not only suggest a way to further understand the electrical transport properties of Ge-Sb-Te based interfaces but also provide a non-touch method to distinguish crystalline area from amorphous matrix with high spatial resolution.

  10. Enhancement of a cyclic endurance of phase change memory by application of a high-density C15(Ge21Sb36Te43 film

    Directory of Open Access Journals (Sweden)

    J. H. Park

    2016-02-01

    Full Text Available The lower cyclic endurance of Phase Change Memory (PCM devices limits the spread of its applications for reliable memory. The findings reported here show that micro-voids and excess vacancies that are produced during the deposition process and the subsequent growth in sputtered carbon-doped GeSbTe films is one of the major causes of device failure in PCM with cycling. We found that the size of voids in C15(Ge21Sb36Te43 films increased with increasing annealing temperature and the activation energy for the growth rate of voids was determined to be 2.22 eV. The film density, which is closely related to voids, varies with the deposition temperature and sputtering power used. The lower heat of vaporization of elemental Sb and Te compared to that for elemental Ge and C is a major cause of the low density of the film. It was possible to suppress void formation to a considerable extent by optimizing the deposition conditions, which leads to a dramatic enhancement in cyclic endurance by 2 orders of magnitude in PCM devices prepared at 300oC-300W compared to one prepared at 240oC-500W without change of compositions.

  11. First-principles study of new series of quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb)

    Science.gov (United States)

    Bouabça, A.; Rozale, H.; Amar, A.; Wang, X. T.; Sayade, A.; Chahed, A.

    2016-12-01

    The structural, electronic, magnetic, and thermal properties of new quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson as the exchange correlation. The results showed that all Heusler compounds were stable in Type (I) structure. The CsSrCZ (Z=Si, Ge, Sn) compounds had a nearly HM characteristic, and CsSrCZ (Z=P, As, Sb) compounds were true half-metallic (HM) ferromagnets. The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. The half-metallicity is preserved up to a lattice contraction of 3.45%, 1.69%, 1.69%, 7.16%, 7.16%, and 11.2% for all six quaternary Heusler compounds. We also investigated the thermal effects using the quasi-harmonic Debye model.

  12. Enhancement of a cyclic endurance of phase change memory by application of a high-density C15(Ge21Sb36Te43) film

    Science.gov (United States)

    Park, J. H.; Kim, S. W.; Kim, J. H.; Ko, D. H.; Wu, Z.; Ahn, D.; Ahn, D. H.; Lee, J. M.; Kang, S. B.; Choi, S. Y.

    2016-02-01

    The lower cyclic endurance of Phase Change Memory (PCM) devices limits the spread of its applications for reliable memory. The findings reported here show that micro-voids and excess vacancies that are produced during the deposition process and the subsequent growth in sputtered carbon-doped GeSbTe films is one of the major causes of device failure in PCM with cycling. We found that the size of voids in C15(Ge21Sb36Te43) films increased with increasing annealing temperature and the activation energy for the growth rate of voids was determined to be 2.22 eV. The film density, which is closely related to voids, varies with the deposition temperature and sputtering power used. The lower heat of vaporization of elemental Sb and Te compared to that for elemental Ge and C is a major cause of the low density of the film. It was possible to suppress void formation to a considerable extent by optimizing the deposition conditions, which leads to a dramatic enhancement in cyclic endurance by 2 orders of magnitude in PCM devices prepared at 300oC-300W compared to one prepared at 240oC-500W without change of compositions.

  13. Study of Nanotribology of Different Amorphous GeSbTe Thin Films with Lateral Force Microscope (LFM)%用侧向力显微镜对不同非晶态GeSbTe薄膜的摩擦性能研究

    Institute of Scientific and Technical Information of China (English)

    解国新; 丁建宁; 范真; 付永忠; 朱守星

    2005-01-01

    采用侧向力显微镜研究了磁控溅射方法制备的GeSbTe薄膜在大气环境中的纳米级摩擦性能,考虑了相对湿度、扫描速度及表面粗糙度对其摩擦性能的影响,对比不同成分的GeSbTe薄膜的摩擦特性.结果表明:在相对湿度较大时,扫描速度对针尖和GeSbTe薄膜之间的摩擦力影响很大;在其它条件相同、外加载荷较大时,同一载荷下的摩擦力与表面粗糙度呈线性关系,但在外加载荷较小的情况下,二者呈现非线性变化规律;相对湿度对Ge2Sb2Te5薄膜和针尖的粘附力影响较GeSb2Te4薄膜弱,且粘附力使得摩擦系数减小;在同一相对湿度下,由于薄膜成分的变化导致硬度不同,其对薄膜的摩擦性能也有一定影响.

  14. Electronic structures and magnetism in the Li{sub 2}AgSb-type Heusler alloys, Zr{sub 2}CoZ (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb): A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.T.; Cui, Y.T. [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400044 (China); Liu, X.F. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Liu, G.D., E-mail: gdliu1978@126.com [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400044 (China)

    2015-11-15

    The electronic and magnetic properties of Zr{sub 2}CoZ (Z=Al, Ga, In, Si, Ge, Sn, Pb, and Sb) alloys with a Li{sub 2}AgSb-type structure were investigated systematically using the first-principle calculations. Zr{sub 2}CoZ (Z=Al, Ga, In, Si, Ge, Sn, and Pb) alloys are predicted to be half-metallic ferromagnets at their equilibrium lattice constants. The Zr{sub 2}Co-based alloys have M{sub t} (the total magnetic moment per unit cell) and Z{sub t} (the valence concentration) values following Slater–Pauling rule of M{sub t}=Z{sub t}−18. The effects of lattice constants on the electronic and the magnetic properties are discussed in detail. Moreover, all the alloys investigated in this paper have a negative formation energy, which implies that they are thermodynamically stable. - Highlights: • We studied the electronic and magnetic properties of Zr{sub 2}CoZ alloys. • Zr{sub 2}CoZ alloys are HM ferromagnets in Li{sub 2}AgSb-type structure. • Zr{sub 2}CoZ alloys retain a high spin polarization in a wide range of lattice distortions. • Zr{sub 2}CoZ alloys follow the Slater–Pauling rule M{sub t}=Z{sub t}−18.

  15. Thermal, structural and optical properties of new TeO2sbnd Sb2O3sbnd GeO2 ternary glasses

    Science.gov (United States)

    Pereira, C.; Barbosa, J.; Cassanjes, F. C.; Gonçalves, R. R.; Ribeiro, S. J. L.; Poirier, G.

    2016-12-01

    In this work the novel glass system TeO2sbnd Sb2O3sbnd GeO2 was investigated and promising glass compositions were selected for further specific studies. Glass samples in the (80-0.8x)TeO2-(20-0.2x)Sb2O3-xGeO2 molar composition were prepared by the melt-quenching method with a glass-forming domain from x = 10 to x = 90. Samples were investigated by XRD, DSC, FTIR, Raman spectroscopy and UV-visible absorption. The XRD and DSC results bring informations about the non-crystalline state and thermal properties of these materials. It has been observed that higher GeO2 contents lead to higher glass transition temperatures and thermal stabilities against crystallization. FTIR and Raman spectroscopies suggest a progressive incorporation of GeO2 in the covalent network of TeO2 with conversion of structural units TeO4 to TeO3. Absorption spectra revealed the high visible transparency of these samples and an increase of the optical band gap with GeO2 addition, in agreement with a decreasing polarizability of the glass network. Er3+ doped and Er3+/Yb3+ codoped samples were also studied with respect to their infrared emission properties and higher GeO2 contents lead to an increase in IR emission intensity at 1,5 μm as well as longer radiative lifetimes. Finally, upconversion emission in the visible were also recorded and were shown to be strongly dependent of the composition.

  16. Ge20Sb15Se65薄膜的热致光学特性变化研究

    Institute of Scientific and Technical Information of China (English)

    宗双飞; 沈祥; 徐铁峰; 陈昱; 王国祥; 陈芬; 李军; 林常规; 聂秋华

    2013-01-01

    采用磁控溅射法制备了Ge20Sb15Se65薄膜,研究热处理温度(150—400C)对薄膜光学特性的影响.通过分光光度计、X射线衍射仪、显微拉曼光谱仪对热处理前后薄膜样品的光学特性和微观结构进行了表征,并根据Swanepoel方法以及Tauc公式分别计算了薄膜折射率色散曲线和光学带隙等参数.结果表明当退火温度(Ta)小于薄膜的玻璃转化温度(Tg)时,薄膜的光学带隙(Eoptg)随着退火温度的增加由1.845eV上升至1.932eV,而折射率由2.61降至2.54;当退火温度大于薄膜的玻璃转化温度时,薄膜的光学带隙随退火温度的增加由1.932eV降至1.822eV,折射率则由2.54增至2.71.最后利用Mott和Davis提出的非晶材料由非晶到晶态的结构转变模型对结果进行了解释,并通过薄膜XRD和Raman光谱进一步验证了结构变化是薄膜热致变化的重要原因.

  17. Chemical mechanical planarization of Ge2Sb2Te5 using IC1010 and Politex reg pads in acidic slurry

    Science.gov (United States)

    He, Ao-Dong; Liu, Bo; Song, Zhi-Tang; Wang, Liang-Yong; Liu, Wei-Li; Feng, Gao-Ming; Feng, Song-Lin

    2014-08-01

    In the paper, chemical mechanical planarization (CMP) of Ge2Sb2Te5 (GST) is investigated using IC1010 and Politex reg pads in acidic slurry. For the CMP with blank wafer, it is found that the removal rate (RR) of GST increases with the increase of pressure for both pads, but the RR of GST polished using IC1010 is far more than that of Politex reg. To check the surface defects, GST film is observed with an optical microscope (OM) and scanning electron microscope (SEM). For the CMP with Politex reg, many spots are observed on the surface of the blank wafer with OM, but no obvious spots are observed with SEM. With regard to the patterned wafer, a few stains are observed on the GST cell, but many residues are found on other area with OM. However, from SEM results, a few residues are observed on the GST cell, more dielectric loss is revealed about the trench structure. For the CMP with IC1010, the surface of the polished blank wafer suffers serious scratches found with both OM and SEM, which may result from a low hardness of GST, compared with those of IC1010 and abrasives. With regard to the patterned wafer, it can achieve a clean surface and almost no scratches are observed with OM, which may result from the high-hardness SiO2 film on the surface, not from the soft GST film across the whole wafer. From the SEM results, a clean interface and no residues are observed on the GST surface, and less dielectric loss is revealed. Compared with Politex reg, the patterned wafer can achieve a good performance after CMP using IC1010.

  18. Ge L{sub 3}-edge x-ray absorption near-edge structure study of structural changes accompanying conductivity drift in the amorphous phase of Ge{sub 2}Sb{sub 2}Te{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Mitrofanov, K. V. [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Kolobov, A. V., E-mail: a.kolobov@aist.go.jp; Fons, P. [Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562, Japan and Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan); Wang, X.; Tominaga, J. [Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Tamenori, Y.; Uruga, T. [Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan); Ciocchini, N.; Ielmini, D. [DEIB - Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy)

    2014-05-07

    A gradual uncontrollable increase in the resistivity of the amorphous phase of phase-change alloys, such as Ge{sub 2}Sb{sub 2}Te{sub 5}, known as drift, is a serious technological issue for application of phase-change memory. While it has been proposed that drift is related to structural relaxation, no direct structural results have been reported so far. Here, we report the results of Ge L{sub 3}-edge x-ray absorption measurements that suggest that the drift in electrical conductivity is associated with the gradual conversion of tetrahedrally coordinated Ge sites into pyramidal sites, while the system still remains in the amorphous phase. Based on electronic configuration arguments, we propose that during this process, which is governed by the existence of lone-pair electrons, the concentration of free carriers in the system decreases resulting in an increase in resistance despite the structural relaxation towards the crystalline phase.

  19. Coherent phonon modes of crystalline and amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} thin films: A fingerprint of structure and bonding

    Energy Technology Data Exchange (ETDEWEB)

    Shalini, A.; Liu, Y.; Srivastava, G. P.; Hicken, R. J. [Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL (United Kingdom); Katmis, F.; Braun, W. [Paul Drude Institute for Solid State Electronics, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2015-01-14

    Femtosecond optical pump-probe measurements have been made upon epitaxial, polycrystalline, and amorphous thin films of Ge{sub 2}Sb{sub 2}Te{sub 5} (GST). A dominant coherent optical phonon mode of 3.4 THz frequency is observed in time-resolved anisotropic reflectance (AR) measurements of epitaxial films, and is inferred to have 3-dimensional T{sub 2}-like character based upon the dependence of its amplitude and phase on pump and probe polarization. In contrast, the polycrystalline and amorphous phases exhibit a comparatively weak mode of about 4.5 THz frequency in both reflectivity (R) and AR measurements. Raman microscope measurements confirm the presence of the modes observed in pump-probe measurements, and reveal additional modes. While the Raman spectra are qualitatively similar for all three phases of GST, the mode frequencies are found to be different within experimental error, ranging from 3.2 to 3.6 THz and 4.3 to 4.7 THz, indicating that the detailed crystallographic structure has a significant effect upon the phonon frequency. While the lower frequency (3.6 THz) mode of amorphous GST is most likely associated with GeTe{sub 4} tetrahedra, modes in epitaxial (3.4 THz) and polycrystalline (3.2 THz) GST could be associated with either GeTe{sub 6} octahedra or Sb-Te bonds within defective octahedra. The more polarizable Sb-Te bonds are the most likely origin of the higher frequency (4.3–4.7 THz) mode, although the influence of Te-Te bonds cannot be excluded. The effect of high pump fluence, which leads to irreversible structural changes, has been explored. New modes with frequency of 3.5/3.6 THz in polycrystalline/amorphous GST may be associated with Sb{sub 2}Te{sub 3} or GeTe{sub 4} tetrahedra, while a 4.2 THz mode observed in epitaxial GST may be related to segregation of Sb.

  20. Far-infrared study of amorphous Ge{sub 0.17}Se{sub 0.83-x}Sb{sub x} chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Parikshit [Department of Physics, H.P. University, Summer Hill, Shimla 171005 (India)], E-mail: sharma_parikshit@yahoo.com; Rangra, V.S. [Department of Physics, H.P. University, Summer Hill, Shimla 171005 (India); Sharma, Pankaj [Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan, H.P. 173215 (India)], E-mail: pankaj.sharma@juit.ac.in; Katyal, S.C. [Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan, H.P. 173215 (India)

    2009-07-08

    Far-infrared transmission spectra of Ge{sub 0.17}Se{sub 0.83-x}Sb{sub x} (x = 0, 0.03, 0.09, 0.12, 0.15) glassy alloys are obtained in the spectral range 500-200 cm{sup -1} at room temperature. The results are interpreted in terms of the vibrations of the isolated molecular units, in such a way as to preserve fourfold and twofold coordination for Ge and Se atoms, respectively. In the Ge{sub 0.17}Se{sub 0.83} bulk glass the main absorption bands appear at {approx}250 cm{sup -1} and 300 cm{sup -1}. With the increase in Sb content some new bands start appearing at 228-231 cm{sup -1} and 250-260 cm{sup -1}. Theoretical calculations (bond energy, relative probability density of bond formation, force constant and wave number) were also made to justify the results.

  1. Laser ablation of (GeSe2)100-x(Sb2Se3)x chalcogenide glasses: Influence of the target composition on the plasma plume dynamics

    Science.gov (United States)

    Irimiciuc, S.; Boidin, R.; Bulai, G.; Gurlui, S.; Nemec, P.; Nazabal, V.; Focsa, C.

    2017-10-01

    The dynamics and properties of the (GeSe2)100-x(Sb2Se3)x laser-induced plasma were investigated by fast ICCD imaging and space- and time-resolved optical emission spectroscopy (OES). The experiments were performed at 10-6 Torr background pressure, using the second harmonic (532 nm) of the Nd-YAG laser (10 ns, 10 Hz). For all investigated samples, the ICCD images revealed a splitting of the plasma plume into three components with distinct dynamics. Based on OES measurements, the first and second plasma structures were found to be represented mainly by ionic and neutral species, respectively. As the Sb2Se3 content of the samples increases, the three structures present an increase in their velocities. This dynamic variation and also the compositional dependence of the excitation temperature obtained from Boltzmann plots were correlated to the changes in the structure and electrical/thermal properties of the bulk chalcogenide glasses.

  2. Optical waveguide based on amorphous Er{sup 3+}-doped Ga-Ge-Sb-S(Se) pulsed laser deposited thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nazabal, V., E-mail: virginie.nazabal@univ-rennes1.f [Sciences Chimiques de Rennes (SCR), UMR CNRS 6226, Equipe Verres et Ceramiques, Universite de Rennes 1, Rennes (France); Nemec, P. [Department of General and Inorganic Chemistry and Research Center, Faculty of Chemical Technology, University of Pardubice, Legions Sq. 565, 53210, Pardubice (Czech Republic); Jurdyc, A.M [Laboratoire de Physico-Chimie des Materiaux Luminescents (LPCML), UMR CNRS 5620, Universite Claude Bernard-Lyon 1, Villeurbanne (France); Zhang, S.; Charpentier, F. [Sciences Chimiques de Rennes (SCR), UMR CNRS 6226, Equipe Verres et Ceramiques, Universite de Rennes 1, Rennes (France); Lhermite, H. [IETR-Microelectronique, UMR CNRS 6251, Universite de Rennes 1, 35042 Rennes (France); Charrier, J. [FOTON, UMR 6082-ENSSAT, UMR CNRS 6251, Universite de Rennes 1, 35042 Rennes (France); Guin, J.P. [LARMAUR, UMR CNRS 6251, Universite de Rennes 1, 35042 Rennes (France); Moreac, A. [Institut de Physique de Rennes, UMR CNRS 6251, Universite de Rennes 1, 35042 Rennes (France); Frumar, M. [Department of General and Inorganic Chemistry and Research Center, Faculty of Chemical Technology, University of Pardubice, Legions Sq. 565, 53210, Pardubice (Czech Republic); Adam, J.-L. [Sciences Chimiques de Rennes (SCR), UMR CNRS 6226, Equipe Verres et Ceramiques, Universite de Rennes 1, Rennes (France)

    2010-06-30

    Amorphous chalcogenide films play a motivating role in the development of integrated planar optical circuits due to their potential functionality in near infrared (IR) and mid-IR spectral regions. More specifically, the photoluminescence of rare earth ions in amorphous chalcogenide films can be used in laser and amplifier devices in the IR spectral domain. The aim of the present investigation was to optimize the deposition conditions for the fabrication of undoped and Er{sup 3+} doped sulphide and selenide thin films with nominal composition Ga{sub 5}Ge{sub 20}Sb{sub 10}S(Se){sub 65} or Ga{sub 5}Ge{sub 23}Sb{sub 5}S{sub 67} by pulsed laser deposition (PLD). The study of compositional, morphological and structural characteristics of the layers was realized by scanning electron microscopy-energy dispersive spectroscopy, atomic force microscopy and Raman spectroscopy analyses, respectively. Some optical properties (transmittance, index of refraction, optical band gap, etc.) of prepared chalcogenide films and optical losses were investigated as well. The clear identification of near-IR photoluminescence of Er{sup 3+} ions was obtained for both selenide and sulphide films. The decay of the {sup 4}I{sub 13/2} {yields} {sup 4}I{sub 15/2} transition at 1.54 {mu}m in Er{sup 3+} doped Ga{sub 5}Ge{sub 20}Sb{sub 10}S{sub 65} PLD sulphide films was studied to assess the effects of film thickness, rare earth concentration and multilayer PLD deposition on their spectroscopic properties.

  3. X-ray photoelectron spectroscopy studies of Ag-doped thin amorphous Ge{sub x}Sb{sub 40-x}S{sub 60} films

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, R.K.; Fitzgerald, A.G.; Christova, K

    2002-12-30

    X-ray photoelectron spectroscopy has been used to determine the binding energies of the core electrons in Ag-doped amorphous thin Ge{sub x}Sb{sub 40-x}S{sub 60} films (x=15, 20, 25 and 27). Chemical shifts of the constituent elements have revealed that electrons are transferred from chalcogenide to metal and compounds such as Ag{sub 2}S and Ag{sub 2}O are likely to foue to photo-induced chemical modification and oxidation, respectively. Charge defects are induced in the amorphous system.

  4. Vacancy or not: An insight on the intrinsic vacancies in rocksalt-structured GeSbTe alloys from ab initio calculations

    Science.gov (United States)

    Zhou, J.; Sun, Z.; Pan, Y.; Song, Z.; Ahuja, R.

    2011-07-01

    Rocksalt-structured GeSbTe (GST) phase-change materials contain significant amounts of intrinsic vacancies at one sublattice. On the basis of ab initio total energy calculations, we have shown that the so-called intrinsic vacancies result from geometrical voids that originate from packing spaces for lone pairs of electrons tightly bound to specific Te layers where a weak bonding exists. The existence of such geometrical voids is concomitant with a narrow band gap. The present results will shed new insights on the intrinsic vacancies in rocksalt-structured GST.

  5. Couples Magnetic and Structural Transitions in High-Purity Dy and Gd5SbxGe4-x

    Energy Technology Data Exchange (ETDEWEB)

    Chernyshov, Alexander S. [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    Magnetic materials exhibiting magnetic phase transitions simultaneously with structural rearrangements of their crystal lattices hold a promise for numerous applications including magnetic refrigeration, magnetomechanical devices and sensors. We undertook a detailed study of a single crystal of dysprosium metal, which is a classical example of a system where magnetic and crystallographic sublattices can be either coupled or decoupled from one another. Magnetocaloric effect, magnetization, ac magnetic susceptibility, and heat capacity of high purity single crystals of dysprosium have been investigated over broad temperature and magnetic field intervals with the magnetic field vector parallel to either the a- or c-axes of the crystal. Notable differences in the behavior of the physical properties when compared to Dy samples studied in the past have been observed between 110 K and 125 K, and between 178 K and ~210 K. A plausible mechanism based on the formation of antiferromagnetic clusters in the impure Dy has been suggested in order to explain the reduction of the magnetocaloric effect in the vicinity of the Neel point. Experimental and theoretical investigations of the influence of commensurability effects on the magnetic phase diagram and the value of the magnetocaloric effect have been conducted. The presence of newly found anomalies in the physical properties has been considered as evidence of previously unreported states of Dy. The refined magnetic phase diagram of dysprosium with the magnetic field vector parallel to the a-axis of a crystal has been constructed and discussed. The magnetic and crystallographic properties of Gd5SbxGe4-x pseudo-binary system were studied by x-ray diffraction (at room temperature), heat capacity, ac-magnetic susceptibility, and magnetization in the temperature interval 5-320 K in magnetic fields up to 100 kOe. The magnetic properties of three composition (x = 0.5, 1,2) were examined in detail. The

  6. The effects of Sb on the thermoelectric properties of Mg{sub 2}Si{sub 1-x}Ge{sub x} prepared by using solid-state synthesis

    Energy Technology Data Exchange (ETDEWEB)

    You, Sin-Wook; Shin, Dong-Kil; Kim, Il-Ho [Korea National University of Transportation, Chungju (Korea, Republic of)

    2014-05-15

    Sb-doped Mg{sub 2}Si{sub 1-x}Ge{sub x} solid solutions were successfully prepared by using a solid-state reaction and hot pressing. In the case of the undoped Mg{sub 2}Si{sub 1-x}Ge{sub x} specimens, the electrical conduction changed from n-type to p-type at room temperature for x ≥ 0.7 due to the intrinsic properties of Mg{sub 2}Ge. The electrical conductivity rapidly increased with increasing temperature, indicating a non-degenerate semiconducting behavior, and decreased with increasing Ge content. However, the Sb-doped Mg{sub 2}Si{sub 1-x}Ge{sub x} specimens showed n-type conduction, and the carrier concentration was increased from 4.0 x 10{sup 17} to 3.2 x 10{sup 21} cm{sup -3} by doping with Sb atoms, which acted as donors. The absolute value of the Seebeck coefficient increased with increasing temperature, and the Seebeck coefficient ranged from -131 to -259 μV/K for the Sb-doped specimens. Sb doping reduced the thermal conductivities of the Mg{sub 2}Si{sub 1-x}Ge{sub x} solid solutions at temperatures above 723 K. Mg{sub 2}Si{sub 0.5}Ge{sub 0.5}:Sb{sub 0.02} exhibited a maximum dimensionless figure-of-merit of 0.56 at 823 K.

  7. A study of reversible gamma-induced structural transformations in vitreous Ge23.5Sb11.8S64.7 by high-resolution X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Kovalskiy, Andriy; Jain, Himanshu; Miller, Alfred C; Golovchak, Roman Ya; Shpotyuk, Oleh I

    2006-11-16

    The structural origin of reversible gamma-induced effects in vitreous Ge(23.5)Sb(11.8)S(64.7) has been investigated by high-resolution X-ray photoelectron spectroscopy (XPS). The changes in valence band spectrum from gamma-irradiation suggest a decrease of sulfur lone pair electron concentration accompanied by changes in bonding states of S and Ge. The appearance of additional doublets in the core-level XPS spectra of Ge, Sb, and S atoms for gamma-irradiated sample is described by the formation of over- and under-coordinated charged defect pairs (Ge(3)(-)-S(3)(+)) as a result of radiation treatment. The results verify the switching of Ge-S covalent bonds into S-S bonds as the main microstructural mechanism for gamma-induced optical effects in this glass.

  8. Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications

    Science.gov (United States)

    Slack, J.F.; Kelley, K.D.; Anderson, V.M.; Clark, J.L.; Ayuso, R.A.

    2004-01-01

    Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqaluk display an antithetic relationship between SiO2/Al2O3 and TiO2/Zr which, together with textural information, suggest preferential silicification of carbonate-bearing sediments. Data for both drill cores also show generally high Tl, Sb, As, and Ge and uniformly positive Eu anomalies (Eu/Eu* > 1.0). Similar high Tl, Sb, As, Ge, and Eu/Eu* values are present in the footwall and shallow hanging wall of Zn-Pb-Ag sulfide intervals at Anarraaq but are not as widely dispersed. Net chemical changes for altered wall rocks in the district, on the basis of average Al-normalized data relative to unaltered black shales of the host Kuna Formation, include large enrichments (>50%) of Fe, Ba, Eu, V, S, Co, Zn, Pb, Tl, As, Sb, and Ge at both Red Dog and Anarraaq, Si at Red Dog, and Sr, U, and Se at Anarraaq. Large depletions (>50%) are evident for Ca at both Red Dog and Anarraaq, for Mg, P, and Y at Red Dog, and for Na at Anarraaq. At both Red Dog and Anarraaq, wall-rock alteration removed calcite and minor dolomite during hydrothermal decarbonation reactions and introduced Si, Eu, and Ge during silicification. Sulfidation reactions deposited Fe, S, Co, Zn, Pb, Tl, As, and Sb; barite mineralization introduced Ba, S, and Sr. Light REE and U were mobilized locally. This alteration and mineralization occurred during Mississippi an hydrothermal events that predated the Middle Jurassic-Cretaceous Brookian orogeny. Early hydrothermal silicification at Red Dog took place prior to or during massive sulfide mineralization, on the basis of the dominantly planar nature of Zn-Pb veins, which suggests

  9. Direct evidence of reactive ion etching induced damages in Ge{sub 2}Sb{sub 2}Te{sub 5} based on different halogen plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juntao [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Microsystem Technology Laboratory, Microsystem & Terahertz Research Center, Sichuan Province 610200 (China); Xia, Yangyang [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100080 (China); Liu, Bo, E-mail: liubo@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Feng, Gaoming [United Lab, Semiconductor Manufacturing International Corporation, Shanghai 201203 (China); Song, Zhitang [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Gao, Dan; Xu, Zhen; Wang, Weiwei [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100080 (China); Chan, Yipeng [United Lab, Semiconductor Manufacturing International Corporation, Shanghai 201203 (China); Feng, Songlin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2016-08-15

    Highlights: • The results of SEM and AFM directly showed that the surface of Cl2 etched samples were roughest with a Ge deficient damaged layer. • The XPS of Te 3d revealed the electrons were transferred from chalcogenide to halogen and the highest halogenation was observed on CF4 etching GST films. • The sidewall of HBr etching GST is nearly vertical compared with others. • HBr is promising gas for GST etching in the fabrication of high-density memory devices. - Abstract: Chalcogenide glasses based on Ge-Te-Sb are processed using reactive ion etching (RIE) in the fabrication of phase change memory (PCM). These materials are known to be halogenated easily and apt to be damaged when exposed to halogen gas based plasmas which can cause severe halogenation-induced degradation. In this paper, we investigate the RIE induced damage of popular phase change material Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) in different halogen based plasmas (CF{sub 4}, Cl{sub 2} and HBr) highly diluted by argon. After blanket etching, results of scanning electron microscopy and atomic force microscopy directly showed that the surface of Cl{sub 2} etched samples were roughest with a Ge deficient damaged layer. X-ray photoelectron spectroscopy was performed to investigate the chemical shift of constituent elements. Selected scans over the valence band peaks of Te 3d revealed that electrons were transferred from chalcogenide to halogen and the highest halogenation was observed on the GST etched by CF{sub 4}. The GST films masked with patterned TiN were also etched. High-resolution transmission electron microscopy and surface scan directly showed the line profile and the damaged layer. Almost vertical and smooth sidewall without damaged layer makes HBr a promising gas for GST etch in the fabrication of high-density memory devices.

  10. Stimulated crystallization of melt-quenched Ge{sub 2}Sb{sub 2}Te{sub 5} films employing femtosecond laser double pulses

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, Rebecca L.; Siegel, Jan [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, E-28006 Madrid (Spain)

    2012-12-15

    The phase transformation of Ge{sub 2}Sb{sub 2}Te{sub 5} films from the melt-quenched amorphous phase into the crystalline phase induced by 800 nm, 100 fs laser pulses has been studied. For partly amorphized films, progressive crystallization could be induced by single pulses, which can be explained by growth of already existing crystalline embryos. For completely amorphized films, it was not possible to induce crystallization with one or two consecutive pulses; three pulses being the threshold for the onset of crystallization. By employing a fs laser double pulse with an adjustable inter-pulse delay, partial crystallization could be triggered for a delay range of 200 fs-100 ps, while for longer delays no crystallization was possible. The time window for stimulated crystallization can be related to the relaxation dynamics of free electrons excited by the first pulse, which are further excited by the second pulse still remaining in the excited state. Our results indicate that the lifetime of excited electrons in melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} is Almost-Equal-To 100 ps.

  11. Far-Infrared and Raman Spectroscopy Investigation of Phonon Modes in Amorphous and Crystalline Epitaxial GeTe-Sb2Te3 Alloys

    Science.gov (United States)

    Bragaglia, V.; Holldack, K.; Boschker, J. E.; Arciprete, F.; Zallo, E.; Flissikowski, T.; Calarco, R.

    2016-06-01

    A combination of far-infrared and Raman spectroscopy is employed to investigate vibrational modes and the carrier behavior in amorphous and crystalline ordered GeTe-Sb2Te3 alloys (GST) epitaxially grown on Si(111). The infrared active GST mode is not observed in the Raman spectra and vice versa, indication of the fact that inversion symmetry is preserved in the metastable cubic phase in accordance with the Fm3 space group. For the trigonal phase, instead, a partial symmetry break due to Ge/Sb mixed anion layers is observed. By studying the crystallization process upon annealing with both the techniques, we identify temperature regions corresponding to the occurrence of different phases as well as the transition from one phase to the next. Activation energies of 0.43 eV and 0.08 eV for the electron conduction are obtained for both cubic and trigonal phases, respectively. In addition a metal-insulator transition is clearly identified to occur at the onset of the transition between the disordered and the ordered cubic phase.

  12. Surface etching mechanism of carbon-doped Ge{sub 2}Sb{sub 2}Te{sub 5} phase change material in fluorocarbon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Lanlan [Chinese Academy of Sciences, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Shanghai (China); Graduate School of the Chinese Academy of Sciences, Beijing (China); Song, Sannian; Song, Zhitang; Li, Le; Guo, Tianqi; Cheng, Yan; Lv, Shilong; Wu, Liangcai; Liu, Bo; Feng, Songlin [Chinese Academy of Sciences, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Shanghai (China)

    2016-09-15

    Recently, carbon-doped Ge2Sb2Te5 (CGST) phase change material has been widely researched for being highly promising material for future phase change memory application. In this paper, the reactive-ion etching of CGST film in CF{sub 4}/Ar plasma is studied. Compared with GST, the etch rate of CGST is relatively lower due to the existence of carbon which reduce the concentration of F or CF{sub x} reactive radicals. It was found that Argon plays an important role in defining the sidewall edge acuity. Compared with GST, more physical bombardment is required to obtain vertical sidewall of CGST. The effect of fluorocarbon gas on the damage of the etched CGST film was also investigated. A Ge- and Sb-deficient layer with tens of nanometers was observed by TEM combining with XPS analysis. The reaction between fluorocarbon plasma and CGST is mainly dominated by the diffusion and consumption of reactive fluorine radicals through the fluorocarbon layer into the CGST substrate material. The formation of damage layer is mainly caused by strong chemical reactivity, low volatility of reaction compounds and weak ion bombardment. (orig.)

  13. The thermodynamic, electronic and magnetic properties of Ni{sub 2}MnX (X=Ge, Sn, Sb) Heusler alloys: a quasi-hormonic Debye model and first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Li Jia, E-mail: jiali@hebut.edu.cn [School of Science, Hebei University of Technology, Tianjin 300130 (China); Zhang Zhidong; Sun Yubao; Zhang Jian; Zhou Guoxiang [School of Science, Hebei University of Technology, Tianjin 300130 (China); Luo Hongzhi; Liu Guodong [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2013-01-15

    The thermodynamic, electronic and magnetic properties of Ni{sub 2}MnX (X=Ge, Sn, Sb) Heusler alloys are investigated using the quasi-hormonic Debye model and the first principles calculation based on the density-functional-theory. The calculated results of the temperature dependent bulk modulus, coefficient of thermal expansion and the P-V relation for Ni{sub 2}MnX (X=Ge, Sn, Sb) indicate that the bonding strength becomes stronger along the sequence of Ni{sub 2}MnSb{yields}Ni{sub 2}MnSn{yields}Ni{sub 2}MnGe. The slower change trend of temperature dependent heat capacity of Ni{sub 2}MnGe than that of Ni{sub 2}MnSn and Ni{sub 2}MnSb stems from the larger contribution of electronic heat capacity and smaller contribution of lattice heat capacity compared to the other two alloys. The ferromagnetic coupling order between the Ni and Mn is confirmed by our first principles calculations. The total moments in one primitive cell for the three alloys are all about 4.0 {mu}{sub B} which are mainly carried by Mn atom with about 3.5 {mu}{sub B} as can be seen from the magnetization density distribution.

  14. Radiochemical neutron activation analysis for 36 elements in geological material: Au, Ag, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn as well as Sc, Y, and REE

    Energy Technology Data Exchange (ETDEWEB)

    Anders, E; Wolf, R; Morgan, J W; Ebihara, M; Woodrow, A B; Janssens, M J; Hertogen, J

    1988-01-01

    In lunar and terrestrial rocks and in meteorites, the radiochemical neutron activation method decribed here enables determination of the 21 trace and ultratrace elements Ag, Au, Bi, Br, Cd, Cs, Ga, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, Zn, as well as 13 rare earth elements (REE), Sc and Y. Materials, techniques and procedures are discussed. 81 refs.

  15. Ge2Sb2Te5材料与非挥发相转变存储器单元器件特性%The performance of Ge2Sb2Te5 material and nonvolatile phase-change-memory device

    Institute of Scientific and Technical Information of China (English)

    凌云; 林殷茵; 赖连章; 乔保卫; 赖云锋; 冯洁; 汤庭鳌; 蔡炳初; Bomy. Chen

    2005-01-01

    Ge2Sb2Te5材料的结构、形貌和电学特性进行了表征,将材料应用于不挥发存储单元器件中并研究了器件性能.研究了退火温度对薄膜电阻率的影响,发现在从高阻向低阻状态转变的过程中,电阻率下降的趋势发生变化,形成拐点,分析表明这是由于在拐点处结构由面心立方向密排六方结构转变所致;对不同厚度Ge2Sb2Te5薄膜的电阻率进行了分析,结果表明当厚度薄于70nm时,电阻率随厚度显著上升而迁移率下降,材料晶态电学性能的测量显示,材料有正电阻温度系数并以空穴导电;测量了Ge2Sb2Te5非挥发相转变存储器单元的I-V曲线,发现有阈值特性,在晶态时电学特性呈欧姆特性,非晶态时I-V低场为线性关系,电场较高时呈指数关系.

  16. 基于Sn掺杂Ge2Sb2Te5的相变存储器器件单元存储性能%Storage characteristics of phase change memory cells based on Sn- doped Ge2Sb2Te5

    Institute of Scientific and Technical Information of China (English)

    徐成; 刘波; 冯高明; 吴良才; 宋志棠; 封松林; Bomy Chen

    2008-01-01

    采用0.18μm标准工艺制备出基于Sn掺杂Ge2Sb2Te5相变材料的相变存储器器件单元,利用自行设计搭建的电学测试系统研究了其存储性能.结果表明:Sn的掺杂没有改变Ge2Sb2Te5的相变特性,其相变阚值电压和阈值电流分别为1.6V和25μA;实现了器件单元的非晶态(高阻)与晶态(低阻)之间的可逆相变过程;器件单元中相变材料结晶所需电流最低为1.78mA(电流宽度固定为100ns)、结晶时间大于80ns(电流高度固定为3mA);相变材料非晶化脉冲电流宽度为30ns时,所需电流大于3.3mA;与Ge2Sb2Te5相比,Sn的掺杂降低了SET操作的脉冲电流宽度,提高了结晶速度,有利于提高相变存储器的存储速度.

  17. Experimental study of the structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se by means of NQR and EPR spectroscopy

    Science.gov (United States)

    Bolebrukh, Olga; Sinyavsky, Nikolay; Korneva, Irina; Dobosz, Bernadeta; Ostafin, Michal; Nogaj, Boleslaw; Krzyminiewski, Ryszard

    2013-12-01

    The structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se has been studied by means of both NQR (nuclear quadrupole resonance) and EPR (electron paramagnetic resonance) spectroscopy. It is investigated that in the glasses of both systems the value of the electric field gradient at the resonating nuclei grows with increasing concentration of the clusters As2Se3 and Sb2Se3, thereby increasing the NQR resonance frequencies. It appears that for the Ge-As-Se system the structural transition from a two-dimensional to three-dimensional structure occurs at average coordination number bar r = 2.45. The EPR spectral parameters of glasses depend on the composition, the average coordination number and the temperature, and these are discussed. The effect of "ageing" for CGS (chalcogenide glassy semiconductors) of As-Sb-Se system due to partial crystallization of the sample is observed from the EPR spectra.

  18. Electronic structures and magnetism of Rh{sub 3}Z (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb) with DO{sub 3} structures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.T. [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Dai, X.F.; Wang, L.Y. [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, X.F. [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Wang, W.H.; Wu, G.H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Tang, C.C. [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, G.D., E-mail: gdliu1978@126.com [School of Material Sciences and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2015-03-15

    We investigate the electronic structures and magnetism of Rh{sub 3}Z (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb) with a DO{sub 3} structure using the first-principle calculations. The Rh{sub 3}Z (Z=Si, Ge, Sn, Pb) alloys have been predicted to be half-metallic ferromagnets at their equilibrium lattice parameters. The half-metallicity of Rh{sub 3}Z (Z=Si, Ge, Sn, Pb) alloys can be kept in a quite large hydrostatic strain and tetragonal distortion. The magnetic properties are discussed. The Rh{sub 3}Z (Z=Si, Ge, Sn, Pb) alloys do not follow the M{sub t}=Z{sub t}-24 rule but instead of following the M{sub t}=Z{sub t}-28 rule (M{sub t} is the total magnetic moment per unit cell and Z{sub t} is the valence concentration). Moreover, all the alloys investigated in this paper have a negative formation energy, which implies that they are possible to be synthesized in reality. - Highlights: • We studied the electronic structures and magnetism of the Rh{sub 3}Z alloys. • Rh{sub 3}Z alloys are half-metallic ferromagnets at their equilibrium lattice constants. • Rh{sub 3}Z alloys retain a high spin polarization in a wide range of lattice distortions. • Rh{sub 3}Z alloys with DO{sub 3} structure follow the Slater–Pauling rule M{sub t}=Z{sub t}-28.

  19. The role of specific features of the electronic structure in electrical resistivity of band ferromagnets Co2Fe Z ( Z = Al, Si, Ga, Ge, In, Sn, Sb)

    Science.gov (United States)

    Kourov, N. I.; Marchenkov, V. V.; Perevozchikova, Yu. A.; Weber, H. W.

    2017-05-01

    The electrical resistivity ρ( T) of the band ferromagnets Co2FeZ (where Z = Al, Si, Ga, Ge, In, Sn, and Sb are s- and p-elements of Mendeleev's Periodic Table) has been investigated in the temperature range 4.2 K < T < 1100 K. It has been shown that the dependences ρ( T) of these alloys in a magnetically ordered state at temperatures T < T C are predominantly determined by the specific features of the electronic spectrum in the vicinity of the Fermi level. The processes of charge carrier scattering affect the behavior of the electrical resistivity ρ( T) only in the vicinity of the Curie temperature T C and above, as well as in the low-temperature range (at T ≪ T C).

  20. Nitrogen and Silicon Co-Doping of Ge2Sb2Te5 Thin Films for Improving Phase Change Memory Performance

    Institute of Scientific and Technical Information of China (English)

    CAI Yan-Fei; CAI Bing-Chu; CHEN Bomy; ZHOU Peng; LIN Yin-Yin; TANG Ting-Ao; CHEN Liang-Yao; LI Jing; QIAO Bao-Wei; LAI Yun-Feng; FENG Jie

    2007-01-01

    Electrical properties and phase structures of (Si+N)-codoped Ge2Sb2Te5 (GST) for phase change memory are investigated to improve the memory performance. Compared to the films with N or Si dopants only in previous reports, the (Si+N)-doped GST has a remarkable improvement of crystalline resistivity of about 104mΩcm. The Fourier-transform infrared spectroscopy spectrum reveals the Si-N bonds formation in the film. X-ray diffraction patterns show that the grain size is reduced due to the crystallization inhibition of the amorphous GST by SiNx,which results in higher crystalline resistivity. This is very useful to reduce writing current for phase change memory applications.

  1. Effect of Silicon on Activity Coefficients of Siderophile Elements (P, Au, Pd, As, Ge, Sb, and In) in Liquid Fe, with Application to Core Formation

    Science.gov (United States)

    Righter, K.; Pando, K.; Danielson, L. R.; Humayun, M.; Righter, M.; Lapen, T.; Boujibar, A.

    2016-01-01

    Earth's core contains approximately 10 percent light elements that are likely a combination of S, C, Si, and O, with Si possibly being the most abundant. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE) in Fe liquids, and thus the partitioning behavior of those elements between core and mantle. The effect of Si can be small such as for Ni and Co, or large such as for Mo, Ge, Sb, As. The effect of Si on many siderophile elements is unknown yet could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of P, Au, Pd, and many other SE between metal and silicate melt. The results will be applied to Earth, for which we have excellent constraints on the mantle siderophile element concentrations.

  2. Negative P-T slopes characterize phase change processes: Case of the Ge1Sb2Te4 phase change alloy

    Science.gov (United States)

    Kalkan, B.; Sen, S.; Aitken, B. G.; Raju, S. V.; Clark, S. M.

    2011-07-01

    The crystalline, liquid and amorphous phase stabilities and transformations of the Ge1Sb2Te4 (GST124) alloy are investigated as a function of pressure and temperature using synchrotron diffraction experiments in a diamond anvil cell. The results indicate that the solid-state amorphization of the cubic GST124 phase under high pressure may correspond to a metastable extension of the stability field of the GST124 liquid along a hexagonal crystal-liquid phase boundary with a negative P-T slope. The internal pressures generated during phase change are shown to be too small to affect phase stability. However, they may be important in understanding reliability issues related to thermomechanical stress development in phase change random access memory structures.

  3. Visible up-conversion and near-infrared luminescence of Er3+/Yb3+ co-doped SbPO4-GeO2 glasses

    Science.gov (United States)

    Manzani, D.; Montesso, M.; Mathias, C. F.; Krishanaiah, K. Venkata; Ribeiro, S. J. L.; Nalin, M.

    2016-07-01

    Recent advances in glass chemistry have led to new multifunctional optical glasses of great technological importance. Glasses containing high amounts of antimony have been studied for use in nonlinear optics, near-infrared transmission, and as hosts for rare-earth ions in photonic devices. This work describes a luminescence study of Er3+ and Er3+/Yb3+ co-doping in a new SbPO4-GeO2 binary glass system. Near-infrared and visible up-conversion emissions were observed in the green and red regions, which are enhanced when the samples are co-doped with Yb3+. Near-infrared emissions have good quantum efficiency and full width half maximum of 61 nm. Visible up-conversion emissions are governed by two photons and described by excited state absorption, energy transfer and cross-relaxation processes.

  4. Mid-infrared supercontinuum generation in a three-hole Ge20Sb15Se65 chalcogenide suspended-core fiber

    Science.gov (United States)

    Han, Xin; You, Chenyang; Dai, Shixun; Zhang, Peiqing; Wang, Yingying; Guo, Fangxia; Xu, Dong; Luo, Baohua; Xu, Peipeng; Wang, Xunsi

    2017-03-01

    This work experimentally demonstrates the supercontinuum (SC) generation in a three-hole arsenic free Ge20Sb15Se65 chalcogenide suspended-core fiber. Mechanical drilling was used to prepare the chalcogenide glass preform, which was drawn into suspended-core fibers. The zero-dispersion wavelength of the fiber is moved toward the shorter wavelength of about 3.2 μm through changing the fiber core diameter by controlling the pressure of inert gas during fiber drawing. When a 15 cm-long fiber with a core diameter of 6 μm is pumped using 150 fs pulses at 3.3 μm, SC spanning from ∼3 μm to ∼8 μm was generated.

  5. Cr-doped Ge{sub 2}Sb{sub 2}Te{sub 5} for ultra-long data retention phase change memory

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qing; Xia, Yangyang; Zheng, Yonghui; Zhang, Qi [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); University of the Chinese Academy of Sciences, Beijing 100049 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Liu, Bo, E-mail: liubo@mail.sim.ac.cn; Song, Sannian; Cheng, Yan; Song, Zhitang; Feng, Songlin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Huo, Ruru [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); ShanghaiTech University, Shanghai 200031 (China)

    2015-11-30

    Phase change memory is regarded as one of the most promising candidates for the next-generation non-volatile memory. Its storage medium, phase change material, has attracted continuous exploration. Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) is the most popular phase change material, but its thermal stability needs to be improved when used in some fields at high temperature (more than 120 °C). In this paper, we doped Cr atoms into GST and obtained Cr{sub 10}(Ge{sub 2}Sb{sub 2}Te{sub 5}){sub 90} (labeled as Cr-GST) with high thermal stability. For Cr-GST film, the sheet resistance ratio between amorphous and crystalline states is high up to 3 orders of magnitude. The crystalline Cr-GST film inherits the phase structure of GST, with metastable face-centered cubic phase and/or stable hexagonal phase. The doped Cr atoms not only bond with other atoms but also help to improve the anti-oxidation property of Cr-GST. As for the amorphous thermal stability, the calculated temperature for 10-year-data-retention of Cr-GST film, based on the Arrhenius equation, is about 180 °C. The threshold current and threshold voltage of a cell based on Cr-GST are about 6 μA and 2.7 V. The cell could be operated by suitable voltages for more than 40 000 cycles. Thus, Cr-GST is proved to be a promising phase change material with ultra-long data retention.

  6. Investigation of high spin-polarization, magnetic, electronic and half-metallic properties in RuMn{sub 2}Ge and RuMn{sub 2}Sb Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Dinesh C.; Bhat, Idris Hamid, E-mail: idu.idris@gmail.com

    2015-03-15

    Highlights: • The present materials show magnetism and are ferromagnetic. • The materials show high spin-polarization and follow Slater–Pauling rule. • The materials are half-metallic and can be used as spintronic materials. - Abstract: Half-metallic ferromagnets RuMn{sub 2}Ge and RuMn{sub 2}Sb have been studied in stable F-43m phase. The optimized equilibrium lattice constants in F-43m phase were found to be 5.90 Å and 6.10 Å for RuMn{sub 2}Ge and RuMn{sub 2}Sb, respectively. The materials exhibit half-metallic city with an energy gap in the spin-down channel of 0.38 eV for RuMn{sub 2}Ge and 0.4 eV for RuMn{sub 2}Sb. The calculated total magnetic moments of 2.0 μ{sub B} per unit cell for RuMn{sub 2}Ge and 3.0 μ{sub B} per unit cell for RuMn{sub 2}Sb are in good agreement with Slater–Pauling rule. The magnetic moments of Mn-I and Mn-II mainly contribute to the total magnetic moment of the materials and are antiparallel to each other, hence predicting the signature of ferrimagnetism in RuMn{sub 2}Z alloys. The shifting of bands towards lower energies in spin-down channel for RuMn{sub 2}Sb may be due to the strong covalent character of bonding than RuMn{sub 2}Ge.

  7. Structure and second-order nonlinearity of GeS2-Ga2S3-X2S3 (X=P,As,Sb) chalcogenide glasses

    Institute of Scientific and Technical Information of China (English)

    GONG Yue-qiu; GUO Hai-tao; ZHAO Xiu-jian

    2006-01-01

    To find new chalcogenide glass possessing larger second-order non-linearity,glasses with compositions Ge-Ga-X-S (X=P,As,Sb) were prepared via melt quenching technique. The amorphous nature of all the compositions of the as-quenched glasses was confirmed by X-ray diffraction(XRD). The glassy thermal properties of the as-quenched glasses were established by differential thermal analyses(DTA). The glass structure was studied by RAMAN spectra and the second order nonlinearity was studied by the Maker Fringe method after the electron beam poling(EBP) and electric/temperature field poling(ETFP) respectively. Additions of various pnicogen atoms into the Ge-Ga-S glasses lead to the difference in the second order nonlinearity of the glass. It's found that glasses with different structures result in different SHG intensities,and even more,a large second order nonlinear susceptibility c(2) of about 9 pm/V was obtained for all the glasses and the reasons for such a large susceptibility were analyzed.

  8. The thermodynamic, electronic and magnetic properties of Ni2MnX (X=Ge, Sn, Sb) Heusler alloys: a quasi-hormonic Debye model and first principles study

    Science.gov (United States)

    Li, Jia; Zhang, Zhidong; Sun, Yubao; Zhang, Jian; Zhou, Guoxiang; Luo, Hongzhi; Liu, Guodong

    2013-01-01

    The thermodynamic, electronic and magnetic properties of Ni2MnX (X=Ge, Sn, Sb) Heusler alloys are investigated using the quasi-hormonic Debye model and the first principles calculation based on the density-functional-theory. The calculated results of the temperature dependent bulk modulus, coefficient of thermal expansion and the P-V relation for Ni2MnX (X=Ge, Sn, Sb) indicate that the bonding strength becomes stronger along the sequence of Ni2MnSb→Ni2MnSn→Ni2MnGe. The slower change trend of temperature dependent heat capacity of Ni2MnGe than that of Ni2MnSn and Ni2MnSb stems from the larger contribution of electronic heat capacity and smaller contribution of lattice heat capacity compared to the other two alloys. The ferromagnetic coupling order between the Ni and Mn is confirmed by our first principles calculations. The total moments in one primitive cell for the three alloys are all about 4.0 μB which are mainly carried by Mn atom with about 3.5 μB as can be seen from the magnetization density distribution.

  9. 溅射功率和退火温度对GeSbTe相变薄膜内应力的影响%Influence of sputtering power and annealing temperature on internal stress of GeSbTe phase-change films

    Institute of Scientific and Technical Information of China (English)

    付永忠; 程广贵; 王权

    2012-01-01

    GeSbTe films were prepared by RF magnetron sputtering.Based on the analysis about surface topography and crystal structure of the films,the effect of sputtering power and annealing temperature on internal stress was investigated by atomic force microscopy,X-ray diffraction and stress analyzer.Results show that,the internal stress increases with the sputtering power at certain power range,until reaches a maximum stress with the power of 50W,and then decreases with the increasing of sputtering power.Because the Te atoms segregation to the grain boundaries of GeSbTe,an abrupt tensile stress change takes place at the phase transformation from amorphous state to crystalline(fcc) state under thermal anneal treatments at 160℃,the stress reaches a maximum of 100 MPa and then releases to its original value.But there is very little stress change observed at the fcc to hcp transition.%通过磁控溅射方法制备了GeSbTe薄膜.借助原子力显微镜,X射线衍射仪和应力测试仪等仪器,并结合对薄膜表面形貌和晶体结构的分析,研究了溅射功率和退火温度对薄膜内应力的影响.结果表明:当溅射功率较小时,内应力随着溅射功率的增大而增大,在50W左右时达到最大值,随后又随着溅射功率的增大而减小.退火温度为160℃时,薄膜发生非晶态向fcc晶态结构的相变,由于Te原子析出到晶粒边界,导致薄膜的内应力急剧增大到最大值为100MPa左右,而后随着退火温度的升高而下降,fcc结构向hex结构转变时,内应力变化并不明显.

  10. Towards mid-infrared supercontinuum generation: Ge-Sb-Se mid-infrared step-index small-core optical fiber

    Science.gov (United States)

    Butterworth, J. H.; Jayasuriya, D.; Li, Q. Q.; Furniss, D.; Moneim, N. A.; Barney, E.; Sujecki, S.; Benson, T. M.; Sanghera, J. S.; Seddon, A. B.

    2014-02-01

    In the 21st century, cancer has become a common and feared illness. Early detection is crucial for delivering the most effective treatment of patients, yet current diagnostic tests depend upon the skill of a consultant clinician and histologist for recognition of the cancerous cells. Therefore it is necessary to develop a medical diagnostic system which can analyze and image tissue instantly, removing the margin of human error and with the additional benefit of being minimally invasive. The molecular fingerprint of biological tissue lies within the mid-infrared (IR) region of the electromagnetic spectrum, 3-25μm wavelength. This can be used to determine a tissue spectral map and provide information about the absence or existence of disease, potentially in real-time and in vivo. However, current mid-IR broadband sources are not bright enough to achieve this. One alternative is to develop broadband, mid-IR, supercontinuum generation (SCG). Chalcogenide glass optical fibers have the potential to provide such mid-IR SC light. A popular chalcogenide glass fiber type is based on Ge-As-Se. For biomedical applications it is prudent to avoid the use of arsenic, on account of its toxicity. This paper investigates replacing arsenic with antimony, towards Ge-Sb-Se smallcore optical fibers for SCG. Physical properties of candidate glass pairs are investigated for glass stability via differential thermal analysis etc. and fiber optical loss measurements of associated fibers are assessed. These results are compared to analogous arsenic-containing chalcogenide glasses and optical fibers, and conclusions are drawn focusing on whether there is potential for antimony chalcogenide glass to be used for SCG for mid-infrared medical diagnostics.

  11. 物理截断与电子局域函数结合法研究Ge2Sb2Te5非晶态原子成键

    Institute of Scientific and Technical Information of China (English)

    王鑫洋; 陈念科; 王雪鹏; 张斌; 陈志红; 李贤斌; 刘显强

    2016-01-01

    The method of combining cutoff distance with electron localization function (ELF) can improve the accuracy of the analysis for the amorphous structure, and has been applied to analyse the amorphous structure of the phase change material Ge2Sb2Te5, determining the reasonable value of cutoff distance is 3.20 and the value of ELF Threshold is 0.63. On this basis, the Ge and Sb atomic coordination number and bond angle distribution of structural information are discussed. The results show that Ge atoms are in 3, 4 coordination, which the local structure correspond to the defect octahedral forms and tetrahedron forms; the Sb atoms are also in 3, 4 coordinaion, and the corresponding local structures are mainly the defect octahedral forms.%采用物理截断与电子局域函数相结合的方法,可以提高非晶态结构分析的准确性,并已在GeTe二元非晶结构分析中得到应用。本文将该方法应用于三元系Ge2Sb2Te5合金非晶结构的分析中,确定了分析Ge2Sb2Te5非晶结构合理的物理截断长度为3.20,电子局域函数阈值为0.63。在此基础上对Ge和Sb原子的配位数和键角分布等结构信息进行分析。结果显示:Ge原子以3、4配位为主,对应的局域结构分别为缺陷八面体和四面体;Sb原子同样以3、4配位为主,对应的局域结构主要为缺陷八面体。

  12. Electrical performance of phase change memory cells with Ge{sub 3}Sb{sub 2}Te{sub 6} deposited by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Boschker, Jos E.; Riechert, Henning; Calarco, Raffaella [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Boniardi, Mattia; Redaelli, Andrea [Micron Semiconductor Italia S.r.l., Via C. Olivetti, 2, 20864, Agrate Brianza, MB (Italy)

    2015-01-12

    Here, we report on the electrical characterization of phase change memory cells containing a Ge{sub 3}Sb{sub 2}Te{sub 6} (GST) alloy grown in its crystalline form by Molecular Beam Epitaxy (MBE). It is found that the high temperature growth on the amorphous substrate results in a polycrystalline film exhibiting a rough surface with a grain size of approximately 80–150 nm. A detailed electrical characterization has been performed, including I-V characteristic curves, programming curves, set operation performance, crystallization activation at low temperature, and resistance drift, in order to determine the material related parameters. The results indicate very good alignment of the electrical parameters with the current state-of-the-art GST, deposited by physical vapor deposition. Such alignment enables a possible employment of the MBE deposition technique for chalcogenide materials in the phase change memory technology, thus leading to future studies of as-deposited crystalline chalcogenides as integrated in electrical vehicles.

  13. Mechanism of amorphous Ge2Sb2Te5 removal during chemical mechanical planarization in acidic H2O2 slurry

    Science.gov (United States)

    He, Ao-Dong; Song, Zhi-Tang; Liu, Bo; Zhong, Min; Wang, Liang-Yong; Lü, Ye-Gang; Feng, Song-Lin

    2013-01-01

    In this paper, chemical mechanical planarization (CMP) of amorphous Ge2Sb2Te5 (a-GST) in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2. Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described.

  14. Elastic and optical properties of Ge$_x$Se$_2$Sb$_{1−x}$ ($0.0\\le x \\le 1.0$) glasses

    Indian Academy of Sciences (India)

    K A ALY; N AFIFY; Y B SADDEEK; A M ABOUSEHLY

    2016-04-01

    The present study deals with the effect of composition on the elastic and optical properties of Ge$_x$Se$_2$Sb$_{1−x}$ ($0.0 \\le x \\le 1.0$) glasses. The various elastic moduli of these glasses such as Young’s modulus ($Y$) andthe bulk modulus ($B$) along with the micro-hardness ($H$), Poisson’s ratio ($\\rho$) and Debye temperature ($T_D$) were obtained from the values of the longitudinal ($v_l$) and shear ($v_s$) ultrasonic velocities. On the basis of measurementsof the transmittance and reflectance spectra in the wavelength range of 0.4–2.5 $\\mu$m the optical constants such as the film thickness ($t$), the refractive index ($n$) and the optical band gap ($E_g$) were investigated with high accuracy. The optically determined bulk modulus of these glasses was in good agreement with that elastically investigated. The obtained results were discussed in terms of the changes in the glass density, electronegativity and electronic polarizability with the variation in antimony content.

  15. Atomic Migration Induced Crystal Structure Transformation and Core-Centered Phase Transition in Single Crystal Ge2Sb2Te5 Nanowires.

    Science.gov (United States)

    Lee, Jun-Young; Kim, Jeong-Hyeon; Jeon, Deok-Jin; Han, Jaehyun; Yeo, Jong-Souk

    2016-10-12

    A phase change nanowire holds a promise for nonvolatile memory applications, but its transition mechanism has remained unclear due to the analytical difficulties at atomic resolution. Here we obtain a deeper understanding on the phase transition of a single crystalline Ge2Sb2Te5 nanowire (GST NW) using atomic scale imaging, diffraction, and chemical analysis. Our cross-sectional analysis has shown that the as-grown hexagonal close-packed structure of the single crystal GST NW transforms to a metastable face-centered cubic structure due to the atomic migration to the pre-existing vacancy layers in the hcp structure going through iterative electrical switching. We call this crystal structure transformation "metastabilization", which is also confirmed by the increase of set-resistance during the switching operation. For the set to reset transition between crystalline and amorphous phases, high-resolution imaging indicates that the longitudinal center of the nanowire mainly undergoes phase transition. According to the atomic scale analysis of the GST NW after repeated electrical switching, partial crystallites are distributed around the core-centered amorphous region of the nanowire where atomic migration is mainly induced, thus potentially leading to low power electrical switching. These results provide a novel understanding of phase change nanowires, and can be applied to enhance the design of nanowire phase change memory devices for improved electrical performance.

  16. Mirror-symmetric Magneto-optical Kerr Rotation using Visible Light in [(GeTe)2(Sb2Te3)1]n Topological Superlattices

    Science.gov (United States)

    Bang, Do; Awano, Hiroyuki; Tominaga, Junji; Kolobov, Alexander V.; Fons, Paul; Saito, Yuta; Makino, Kotaro; Nakano, Takashi; Hase, Muneaki; Takagaki, Yukihiko; Giussani, Alessandro; Calarco, Raffaella; Murakami, Shuichi

    2014-07-01

    Interfacial phase change memory (iPCM), that has a structure of a superlattice made of alternating atomically thin GeTe and Sb2Te3 layers, has recently attracted attention not only due to its superior performance compared to the alloy of the same average composition in terms of energy consumption but also due to its strong response to an external magnetic field (giant magnetoresistance) that has been speculated to arise from switching between topological insulator (RESET) and normal insulator (SET) phases. Here we report magneto-optical Kerr rotation loops in the visible range, that have mirror symmetric resonances with respect to the magnetic field polarity at temperatures above 380 K when the material is in the SET phase that has Kramers-pairs in spin-split bands. We further found that this threshold temperature may be controlled if the sample was cooled in a magnetic field. The observed results open new possibilities for use of iPCM beyond phase-change memory applications.

  17. Effect of Film Thickness on the Optical Parameters and Electrical Conductivity of Te10Ge10Se77Sb3 Chalcogenide Glass

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Several thin films of Te10Ge10Se77Sb3 chalcogenide glass of different thicknesses (250 nm to 400 nm) were prepared by thermalevaporation under vacuum of 133×10-6 Pa (10-6torr). X- ray diffraction analysis showed the amorphicity of the preparedfilms which become partially crystalline by annealing. Transmittance and reflectance measurements in the spectral range of200 nm to 2500 nm have been carried out at normal incidence. The analysis of the absorption coefficient data showed theexistence of indirect transition for the photon energy E in the range 1~3 eV and direct transition for E>3 eV. From thedetermination of the optical constants (n, k), the dispersion of the refractive index has anomalous behaviour in the region ofthe fundamental absorption edge, and followed by the single- effective oscillator approach. The investigated optical parameterssuch as the optical energy gap Eopt, the high frequency dielectric constant εoo, the oscillator position λo, and the oscillatorstrength So, were significantly affected by the film thickness. The characteristic energy gap obtained from the conductivitymeasurements is nearly half the value of that obtained from the optical data as in the case of thickness 400 nm. The activationenergy is 0.65 eV and the indirect optical gap is 1.32 eV.

  18. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    Science.gov (United States)

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-01-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state. PMID:28205643

  19. Influence of heat treatment on magnetocaloric effect of the Mn5Ge2.8Sb0.2 alloy powder prepared by ball miller%热处理对Mn5Ge2.8Sb0.2合金粉末磁热效应的影响

    Institute of Scientific and Technical Information of China (English)

    洪波; 金培育; 任慧平; 刘金荣; 徐来自; 王正德

    2004-01-01

    用高频真空悬浮炉冶炼Mn5Ge2.8Sb0.2合金,经20 h高能球磨制粉,制得粉末样品经600 ℃保温2 h热处理.对比该合金粉样品热处理前后的X射线衍射(XRD)图及其磁热效应T-ΔTad曲线(合金块状样品的XRD图及其磁热效应T-ΔTad曲线作为参照).试验结果表明,适当的热处理可以使该合金粉畸变的晶格得到恢复,同时改善其磁热效应ΔTad.

  20. Ablation of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} glass with an ultra-violet nano-second laser

    Energy Technology Data Exchange (ETDEWEB)

    Knotek, P., E-mail: petr.knotek@upce.cz [University of Pardubice, Faculty of Chemical Technology, Joint Laboratory of Solid State Chemistry of IMC and University of Pardubice, Studentska 573, 532 10 Pardubice (Czech Republic); University of Pardubice, Faculty of Chemical Technology, Department of General and Inorganic Chemistry, Studentska 573, 532 10 Pardubice (Czech Republic); Navesnik, J.; Cernohorsky, T. [University of Pardubice, Faculty of Chemical Technology, Institute of Environmental and Chemical Engineering, Studentska 573, 532 10 Pardubice (Czech Republic); Kincl, M.; Vlcek, M.; Tichy, L. [Institute of Macromolecular Chemistry, AS CR, Heyrovskeho sq. 2, 162 06 Prague (Czech Republic)

    2015-04-15

    Highlights: • The interaction of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} bulk glass and film with UV nanosecond laser. • Ablation process, topography of crater and structure of the material were studied. • Ablation threshold fluencies changed with the spot diameter and number of pulses. • The photo-thermal expansion of the material occurred for low laser fluency. • Laser direct writing process applicable for fabrication of passive optical elements. - Abstract: The results of an experimental study of the laser ablation of bulk and thin films of a GeSbS chalcogenide glass using UV nanosecond pulses are reported. The response of the samples to illumination conditions was studied through the use of atomic force spectroscopy, digital holographic microscopy, Raman scattering and scanning electron microscopy. The multi-pulse ablation thresholds were determined for both the bulk and thin film samples for varying number of pulses and illuminated spot diameter. The possible application of direct laser writing into the bulk and thin films of this material is presented.

  1. Ab initio quantum chemical studies of fullerene molecules with substitutes C59X [XSi, Ge, Sn], C59X- [XB, Al, Ga, In], and C59X [XN, P, As, Sb

    Science.gov (United States)

    Simeon, Tomekia M.; Yanov, Ilya; Leszczynski, Jerzy

    This article presents the results of systematic ab initio quantum chemical study of charged and neutral analogues of fullerene molecules: C59X[XSi, Ge, Sn], C59X- [XB, Al, Ga, In], and C59X+ [XN, P, As, Sb]. Hartree-Fock (HF) and density functional theory (DFT) levels of theory with Stuttgart-Dresden basis set were used to investigate the structure and properties of substituted fullerene molecules. A replacement of fullerene carbon atom with a heteroatom results in a unique chemical site on the fullerene surface, which may be used as a reactive center or to modify the electronic properties. We show the possibility of utilization of substituted fullerenes as atom-like building units. Heteroatom substitution allows the tuning of the physical and chemical properties of original molecule for different material science and nanotechnology applications.

  2. Intrinsic evolutions of dielectric function and electronic transition in tungsten doping Ge{sub 2}Sb{sub 2}Te{sub 5} phase change films discovered by ellipsometry at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Guo, S.; Ding, X. J.; Zhang, J. Z.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Ji, X. L.; Wu, L. C.; Song, Z. T. [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-02-02

    Tungsten (W) doping effects on Ge{sub 2}Sb{sub 2}Te{sub 5} (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and Drude dispersion models. The analysis of Tauc gap energy (E{sub g}) and partial spectral weight integral reveal the correlation between optical properties and local structural change. The order degree increment and chemical bond change from covalent to resonant should be responsible for band gap narrowing and electronic transition enhancement during the phase change process. It is found that the elevated crystalline temperature for GSTW can be related to improved disorder degree. Furthermore, the shrinkage of E{sub g} for GSTW should be attributed to the enhanced metallicity compared with undoped GST.

  3. Pulsed laser deposition of thin films of various full Heusler alloys Co{sub 2}MnX (X = Si, Ga, Ge, Sn, SbSn) at moderate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Valerio, E. [Universite de la Mediterranee (Aix-Marseille II), IMFT/IM2/UNIMECA, Technopole de Chateau-Gombert, 60 rue Joliot Curie, 13453 Marseille Cedex 13 (France)]. E-mail: valerio@unimeca.univ-mrs.fr; Grigorescu, C. [National Institute of R and D Optoelectronics-INOE 2000, P.O. Box MG5, Atomistilor 1, Comuna Magurele, Judet Ilfov, 77125 (Romania); Manea, S.A. [National Institute R and D Materials Physics, P.O. Box MG7, Atomistilor 105bis, Comuna Magurele, Judet Ilfov, 77125 (Romania); Guinneton, F. [MADIREL, Centre de St-Jerome, Avenue Escadrille-Normandie-Niemen, 13397 Marseille Cedex 20 (France); Branford, W.R. [Blackett Laboratory, Imperial College, Prince Consort Rd., London, SW7 2BZ (United Kingdom); Autric, M. [Universite de la Mediterranee (Aix-Marseille II), IMFT/IM2/UNIMECA, Technopole de Chateau-Gombert, 60 rue Joliot Curie, 13453 Marseille Cedex 13 (France)

    2005-07-15

    This work presents pulsed laser deposition of cobalt-based Heusler thin films Co{sub 2}MnX (X = Si, Ga, Ge, Sn, SbSn) on different substrates (Si, GaAs, InAs). The deposition processes developed in vacuum (about 10{sup -5} Pa) to avoid oxidation of the films and targets. The temperature of the substrates during the depositions was kept below 500 K to minimise interface interdiffusion. From X-ray diffraction, we found that the films are crystalline and slightly oriented. The stoichiometric composition of the films was further checked by EDS, while the size and density of droplets were determined by SEM. The magnetic properties of the films are consistent with those of the bulk material used as target.

  4. Ge30Sb8Se62硫系玻璃的制备及其10.6μm低损耗空芯光子带隙光纤的设计%Preparation of Ge30Sb8Se62 Chalcogenide Glass and Designing for a Low-Loss Hollow-Core Photonic Crystal Fiber at 10.6 μm

    Institute of Scientific and Technical Information of China (English)

    刘永兴; 张培晴; 许银生; 王训四; 戴世勋; 聂秋华; 徐铁峰

    2012-01-01

    Chalcogenide glass photonic crystal fiber is expected to have important applications in the field of mid-infrared laser transmission. The Ge30Sb8Se62 chalcogenide glass with excellent transparency in mid-infrared region is prepared. Based on this chalcogenide glass,a band-gap photonic crystal fiber is designed,which suits high power laser transmission. With plane wave expansion method and finite element method,photonic band gap,mode-field area and confinement loss of the designed photonic crystal fiber are systematically studied. By optimizing the structural parameters of fiber,photonic crystal fiber with confinement loss less than 0. 1 dB/m and effective mode-field area larger than 100 μm2 at 10. 6μm is obtained.%硫系玻璃光子晶体光纤在中远红外激光传输领域具有广阔的应用前景.制备了红外波段具有优良透过特性的Ge30Sb8Se62硫系玻璃,并以此为基质材料设计了一种适合于高功率中红外激光传输的带隙型光子晶体光纤.利用平面波展开法和有限元法分析了不同结构下该光纤的光子带隙、模场面积和限制损耗特性.通过优化光纤的结构参数,获得了在10.6 μm处限制损耗小于0.1 dB/m的大模场(模场面积大于100 μm2)光子晶体光纤.

  5. Effect of Annealing Temperature on the Optical Properties of a-Se0.70 Geo.15 Sb0.15 Thin Films%退火温度对a-Se0.70Ge0.15Sb0.15薄膜的结构和光学性质的影响

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Thin films of amorphous bulk Se0.70 Ge0.15 Sb0.15 system are deposited on a quartz and glass substrates at 300K by the thermal evaporation technique. The amorphous films were annealed at 370 and 470K in vacuum ~ 10-4Pa for 1h. The as-deposited and annealed films were checked by X-ray diffraction. On annealing at 470K(in the same time and vacuum), the films revealed crystalline nature. The optical constants such as refractive index( n ), absorption coefficient (α) and extinction coefficient (k) were determined from the measured transmittance and reflectance at normal incidence of light in the wavelength range 300~2 500nm. It was found that both( n ) and (k) depend markedly on the temperature of heat treatment. The analysis of the optical data gave non-direct band gaps(Enong)of 1.715 + 0.021, 1,643 + 0.021 and 1.572 + 0.021eV for as-deposited, 370K and 470K annealed samples respectively. The annealing temperatures are decreased the band gap(Enong)and increasing the band-tail(Ee). This effect is interpreted in terms of the density of state model in amorphous solids proposed by Mott and Davis. The Wemple-DiD omenico single oscillator model parameterizes for as-deposited and annealed films are determined.%研究了退火温度对Se0.70Ge0.15Sb0.15薄膜的影响.通过热蒸发技术,在300K温度下将大块无定形Se0.70Ge0.15Sb0.1s沉积在石英和玻璃衬底上.研究发现,未经过退火处理的薄膜结构和在300K,1.33×10-5Pa下退火1小时后的薄膜结构都是无定形结构,而在同样气压470K温度下退火1小时的薄膜有结晶现象.通过在300 2 500nm范围内垂直入射光方向上透射率和反射率的测试,研究了薄膜的一些光学参数,如消光系数(k),折射系数(n)和吸收系数(a).研究发现,n和k同热处理温度有关.通过光学数据的分析,得到了不同条件下薄膜的间接带隙宽度(Enong),未经过热处理薄膜的Enong是1.715±0.021eV,300K下退火薄膜的Enong是1.643±0.021eV,470K

  6. Characterization of defects introduced in Sb doped Ge by 3 keV Ar sputtering using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS)

    Science.gov (United States)

    Nyamhere, C.; Das, A. G. M.; Auret, F. D.; Chawanda, A.; Mtangi, W.; Odendaal, Q.; Carr, A.

    2009-12-01

    We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3 keV Ar ions. Hole traps at EV+0.09 eV and EV+0.31 eV and an electron trap at EC-0.38 eV ( E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at EV+0.26 eV. Above room temperature annealing studies revealed new hole traps at EV+0.27 eV, EV+0.30 eV and EV+0.40 eV.

  7. Characterization of defects introduced in Sb doped Ge by 3 keV Ar sputtering using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS)

    Energy Technology Data Exchange (ETDEWEB)

    Nyamhere, C., E-mail: cloud.nyamhere@up.ac.z [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Das, A.G.M. [School of Information Technology, Monash South Africa, Roodepoort 1725 (South Africa); Auret, F.D.; Chawanda, A.; Mtangi, W.; Odendaal, Q.; Carr, A. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa)

    2009-12-01

    We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3 keV Ar ions. Hole traps at E{sub V}+0.09 eV and E{sub V}+0.31 eV and an electron trap at E{sub C}-0.38 eV (E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at E{sub V}+0.26 eV. Above room temperature annealing studies revealed new hole traps at E{sub V}+0.27 eV, E{sub V}+0.30 eV and E{sub V}+0.40 eV.

  8. 121Sb and 125Te nuclear inelastic scattering in Sb2Te3 under high pressure

    Science.gov (United States)

    Simon, R. E.; Sergueev, I.; Kantor, I.; Kantor, A.; Perßon, J.; Hermann, R. P.

    2014-12-01

    We investigated the lattice dynamics of Sb2Te3 under high pressure using 121Sb and 125Te nuclear inelastic scattering of synchrotron radiation. We measured the room temperature 121Sb and 125Te inelastic spectra at 15(1) GPa and 77(3) GPa and extracted the Te and Sb element specific density of phonon states of δ-Sb2Te3 at 77(3) GPa. X-ray diffraction confirms the sample to be in the cubic δ-Sb2Te3 phase with space group Im\\bar{3}m and lattice constant a=3.268(4) \\overset{\\circ}{A} . The total density of phonon states of δ-Sb2Te3 strongly resembles the one of amorphous GeSb2Te4, suggesting the presence of covalent bonding in contrast to the resonance bonding in α-Sb2Te3. From the density of phonon states of δ-Sb2Te3 a mean speed of sound of 2.61(6) km {{s}-1} and Debye temperatures of 278(10) K for Te and 296(10) K for Sb were determined.

  9. Search for half-metallic magnets with large half-metallic gaps in the quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb)

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Lun [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Laboratory of Optical Information Technology and School of Science, Wuhan Institute of Technology, Wuhan 430073 (China); Yi, Lin [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Gao, G.Y., E-mail: guoying_gao@mail.hust.edu.cn [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-06-01

    We investigate the electronic structure and magnetic properties of the twelve quaternary Heusler alloys CoFeTiZ and CoFeVZ (Z=Al, Ga, Si, Ge, As, Sb) by using the first-principles calculations. It is shown that only CoFeTiSi, CoFeTiAs and CoFeVSb are half-metallic ferromagnets with considerable half-metallic gaps of 0.31, 0.18 and 0.17 eV, respectively. CoFeTiAl and CoFeTiGa are conventional semiconductors, and other alloys exhibit nearly half-metallicity or their half-metallic gaps are almost zero eV. We also find that the half-metallicities of CoFeTiSi, CoFeTiAs and CoFeVSb can be preserved under appropriate uniform and in-plane strains. The considerable half-metallic gaps and the robust half-metallicities under uniform and in-plane strains make CoFeTiSi, CoFeTiAs and CoFeVSb promising candidates for spintronic applications. - Highlights: • CoFeTiSi, CoFeTiAs and CoFeVSb have considerable half-metallic gaps. • Total magnetic moments obey the Slater–Pauling behavior of quaternary Heusler half-metals. • CoFeTiSi, CoFeTiAs and CoFeVSb retain half-metallicity under uniform and in-plane strains.

  10. Crystal Chemistry of the New Families of Interstitial Compounds R6Mg23C (R = La, Ce, Pr, Nd, Sm, or Gd) and Ce6Mg23Z (Z = C, Si, Ge, Sn, Pb, P, As, or Sb).

    Science.gov (United States)

    Wrubl, Federico; Manfrinetti, Pietro; Pani, Marcella; Solokha, Pavlo; Saccone, Adriana

    2016-01-01

    The crystal chemical features of the new series of compounds R6Mg23C with R = La-Sm or Gd and Ce6Mg23Z with Z = C, Si, Ge, Sn, Pb, P, As, or Sb have been studied by means of single-crystal and powder X-ray diffraction techniques. All phases crystallize with the cubic Zr6Zn23Si prototype (cF120, space group Fm3̅m, Z = 4), a filled variant of the Th6Mn23 structure. While no Th6Mn23-type binary rare earth-magnesium compound is known to exist, the addition of a third element Z (only 3 atom %), located into the octahedral cavity of the Th6Mn23 cell (Wyckoff site 4a), stabilizes this structural arrangement and makes possible the formation of the ternary R6Mg23Z compounds. The results of both structural and topological analyses as well as of LMTO electronic structure calculations show that the interstitial element plays a crucial role in the stability of these phases, forming a strongly bonded [R6Z] octahedral moiety spaced by zeolite cage-like [Mg45] clusters. Considering these two building units, the crystal structure of these apparently complex intermetallics can be simplified to the NaCl-type topology. Moreover, a structural relationship between RMg3 and R6Mg23C compounds has been unveiled; the latter can be described as substitutional derivatives of the former. The geometrical distortions and the consequent symmetry reduction that accompany this transformation are explicitly described by means of the Bärnighausen formalism within group theory.

  11. Improved structural and electrical properties in native Sb2Te3/GexSb2Te3+x van der Waals superlattices due to intermixing mitigation

    Directory of Open Access Journals (Sweden)

    Stefano Cecchi

    2017-02-01

    Full Text Available Superlattices made of Sb2Te3/GeTe phase change materials have demonstrated outstanding performance with respect to GeSbTe alloys in memory applications. Recently, epitaxial Sb2Te3/GeTe superlattices were found to feature GexSb2Te3+x blocks as a result of intermixing between constituting layers. Here we present the epitaxy and characterization of Sb2Te3/GexSb2Te3+x van der Waals superlattices, where GexSb2Te3+x was intentionally fabricated. X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy, and lateral electrical transport data are reported. The intrinsic 2D nature of both sublayers is found to mitigate the intermixing in the structures, significantly improving the interface sharpness and ultimately the superlattice structural and electrical properties.

  12. Information on real-structure phenomena in metastable GeTe-rich germanium antimony tellurides (GeTe){sub n}Sb{sub 2}Te{sub 3} (n ≥ 3) by semi-quantitative analysis of diffuse X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Urban, Philipp; Oeckler, Oliver [Leipzig Univ. (Germany). Faculty of Chemistry and Mineralogy; Schneider, Matthias N.; Seemann, Marten [Munich Univ. (Germany). Dept. of Chemistry; Wright, Jonathan P. [ESRF - The European Synchrotron, Grenoble (France)

    2015-07-01

    Quenching cubic high-temperature polymorphs of (GeTe){sub n}Sb{sub 2}Te{sub 3} (n ≥ 3) yields metastable phases whose average structures can be approximated by the rocksalt type with 1/(n + 3) cation vacancies per anion. Corresponding diffraction patterns are a superposition of intensities from individual twin domains with trigonal average structure but pseudo-cubic metrics. Their four orientations are mirrored in structured diffuse streaks that interconnect Bragg reflections along the [001] directions of individual disordered trigonal domains. These streaks exhibit a ''comet-like'' shape with a maximum located at the low-angle side of Bragg positions (''comet head'') accompanied by a diffuse ''comet tail''. 2D extended cation defect ordering leads to parallel but not equidistantly spaced planar faults. Based on a stacking fault approach, the diffuse scattering was simulated with parameters that describe the overall metrics, the concentration and distribution of cation defect layers, atom displacements in their vicinity and the stacking sequence of Te atom layers around the planar defects. These parameters were varied in order to derive simple rules for the interpretation of the diffuse scattering. The distance between Bragg positions and ''comet heads'' increases with the frequency of planar faults. A sharp distance distribution of the planar faults leads to an intensity modulation along the ''comet tail'' which for low values of n approximates superstructure reflections. The displacement of atom layers towards the planar defects yields ''comets'' on the low-angle side of Bragg positions. A rocksalt-type average structure is only present if the planar defects correspond to missing cation layers in the ''cubic'' ABC stacking sequence of the Te atom layers. An increasing amount of hexagonal ABA transitions around the defect

  13. Nature of defects and gap states in GeTe model phase change materials

    Science.gov (United States)

    Huang, B.; Robertson, J.

    2012-03-01

    The electrical storage mechanism in GeSbTe phase change materials is discussed in terms of their gap states using GeTe as a model system. The lowest energy defect in crystalline rhombohedral GeTe phase is the Ge vacancy, because it reconstructs along the resonant bonding directions. The lowest energy in amorphous GeTe is the divalent Te atom, which creates overlapping band-tail states that pin Fermi level EF near midgap. In contrast, the lowest cost defect in disordered phase in GeSbTe superlattices is the Te interstitial whose negative correlation energy pins EF near midgap.

  14. Thermoelectric properties of Co(x)Ni(4-x)Sb(12-y)Sn(y) ternary skutterudites

    Science.gov (United States)

    Mackey, Jon A.; Dynys, Frederick W.; Sehirlioglu, Alp

    2014-01-01

    Thermoelectric materials based on the skutterudite crystal structure have demonstrated enhanced performance (ZT greater than 1), along with good thermal stability and favorable mechanical properties. Binary skutterudites, with single and multiple fillers, have been intensively studied in recent years. Compared to binary skutterudites, the ternary systems have received less attention, e.g. Ni4Sb8Sn4. Ternary skutterudites are isoelectronic variants of binary skutterudites; cation substitutions appear to be isostructural to their binary analogues. In general, ternary skutterudites exhibit lower thermal conductivity. Ternary systems of Ni4Bi8Ge4, Ni4Sb8Ge4, and Ni4Sb8Sn4 were investigated using combined solidification and sintering steps. Skutterudite formation was not achieved in the Ni4Bi8Ge4 and Ni4Sb8Ge4 systems; skutterudite formation occurred in Ni4Sb8Sn4 system. P-type material was achieved by Co substitution for Ni. Thermoelectric properties were measured from 298 K to 673 K for Ni4Sb8Sn4, Ni4 Sb7Sn5 and Co2Ni2Sb7Sn5. N-type Ni4Sb8Sn4 exhibit the highest figure of merit of 0.1 at 523 K.

  15. GaInP semiconductor compounds doped with the Sb isovalent impurity

    Energy Technology Data Exchange (ETDEWEB)

    Skachkov, A. F., E-mail: afskachkov@mail.ru [OAO Saturn (Russian Federation)

    2015-05-15

    GaInP{sub 1−x}Sb{sub x} layers containing different Sb fractions are produced by metal-organic vaporphase epitaxy on GaAs and Ge substrates. The charge-carrier mobilities in the GaInP{sub 1−x}Sb{sub x} layers are measured at room temperature and 77 K. The room-temperature charge-carrier mobilities in the GaInP{sub 1−x}Sb{sub x} layers additionally doped with donor and acceptor impurities are measured. The photoluminescence peaks of GaInP{sub 1−x}Sb{sub x} are detected. The influence of the Sb impurity on the band gap and charge-carrier mobility in GaInP is determined.

  16. GaSbBi/GaSb quantum well laser diodes

    Science.gov (United States)

    Delorme, O.; Cerutti, L.; Luna, E.; Narcy, G.; Trampert, A.; Tournié, E.; Rodriguez, J.-B.

    2017-05-01

    We report on the structural and optical properties of GaSbBi single layers and GaSbBi/GaSb quantum well heterostructures grown by molecular beam epitaxy on GaSb substrates. Excellent crystal quality and room-temperature photoluminescence are achieved in both cases. We demonstrate laser operation from laser diodes with an active zone composed of three GaSb0.885Bi0.115/GaSb quantum wells. These devices exhibit continuous-wave lasing at 2.5 μm at 80 K, and lasing under pulsed operation at room-temperature near 2.7 μm.

  17. Interface formation of two- and three-dimensionally bonded materials in the case of GeTe-Sb₂Te₃ superlattices.

    Science.gov (United States)

    Momand, Jamo; Wang, Ruining; Boschker, Jos E; Verheijen, Marcel A; Calarco, Raffaella; Kooi, Bart J

    2015-12-07

    GeTe-Sb2Te3 superlattices are nanostructured phase-change materials which are under intense investigation for non-volatile memory applications. They show superior properties compared to their bulk counterparts and significant efforts exist to explain the atomistic nature of their functionality. The present work sheds new light on the interface formation between GeTe and Sb2Te3, contradicting previously proposed models in the literature. For this purpose [GeTe(1 nm)-Sb2Te3(3 nm)]15 superlattices were grown on passivated Si(111) at 230 °C using molecular beam epitaxy and they have been characterized particularly with cross-sectional HAADF scanning transmission electron microscopy. Contrary to the previously proposed models, it is found that the ground state of the film actually consists of van der Waals bonded layers (i.e. a van der Waals heterostructure) of Sb2Te3 and rhombohedral GeSbTe. Moreover, it is shown by annealing the film at 400 °C, which reconfigures the superlattice into bulk rhombohedral GeSbTe, that this van der Waals layer is thermodynamically favored. These results are explained in terms of the bonding dimensionality of GeTe and Sb2Te3 and the strong tendency of these materials to intermix. The findings debate the previously proposed switching mechanisms of superlattice phase-change materials and give new insights in their possible memory application.

  18. Au-Ge based Candidate Alloys for High-Temperature Lead-Free Solder Alternatives

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2009-01-01

    Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The influence of the low melting point metals namely In, Sb and Sn to the Au-Ge eutectic with respect to the microstructure and microhard...

  19. Understanding the glass transition in GeSbTe materials

    Science.gov (United States)

    Martyna, Glenn

    2010-03-01

    Moore's law demands the continual reduction in size of the components of computers. One future direction for memory technology involves the use of phase change materials which can be switched by pulsed electrically heating from a conducting crystalline phase to an insulating amorphous phase. These materials are typically alloys of Germanium, Antimony and Tellurium (GST). In order to form multi-state bits, it is necessary to arrest the glass transition via varying annealing time such that differences in resistivity can be measured based. As might be expected, this process is hinder by ``creep'' of the glass towards higher resistance states after the quench is halted. In this lecture, simulation studies are employed to study the glass transition from the crystalline state and discern the mechanism for the gap opening. The nature of mid gaps states found from the simulated quenches gives insight into the mechanism of the creep and suggests ways in which the phenomena can be arrested.

  20. Sn-Sb-Se based binary and ternary alloys for phase change memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Kyung-Min

    2008-10-28

    In this work, the effect of replacing Ge by Sn and Te by Se was studied for a systematic understanding and prediction of new potential candidates for phase change random access memories applications. The temperature dependence of the electrical/structural properties and crystallization kinetics of the Sn-Se based binary and Sn-Sb-Se based ternary alloys were determined and compared with those of the GeTe and Ge-Sb-Te system. The temperature dependence of electrical and structural properties were investigated by van der Pauw measurements, X-ray diffraction, X-ray reflectometry. By varying the heating rate, the Kissinger analysis has been used to determine the combined activation barrier for crystallization. To screen the kinetics of crystallization, a static laser tester was employed. In case of binary alloys of the type Sn{sub x}Se{sub 1-x}, the most interesting candidate is SnSe{sub 2} since it crystallizes into a single crystalline phase and has high electrical contrast and reasonably high activation energy for crystallization. In addition, the SnSe{sub 2}-Sb{sub 2}Se{sub 3} pseudobinary alloy system also might be sufficient for data retention due to their higher transition temperature and activation energy for crystallization in comparison to GeTe-Sb{sub 2}Te{sub 3} system. Furthermore, SnSe{sub 2}-Sb{sub 2}Se{sub 3} pseudobinary alloys have a higher crystalline resistivity. The desired rapid crystallization speed can be obtained for Sn{sub 1}Sb{sub 2}Se{sub 5} and Sn{sub 2}Sb{sub 2}Se{sub 7} alloys. (orig.)

  1. Structural transformation of Ge dimers on Ge(001) surfaces induced by bias voltage

    Institute of Scientific and Technical Information of China (English)

    Qin Zhi-Hui; Shi Dong-Xia; Gao Hong-Jun

    2008-01-01

    Scanning tunnelling microscopy is utilized to investigate the local bias voltage tunnelling dependent transformation between (2×1) and c(4×2) structures on Ge(001) surfaces, which is reversibly observed at room temperature and a critical bias voltage of -0.80 V. Similar transformation is also found on an epitaxial Ge islands but at a slightly different critical bias voltage of -1.00V. It is found that the interaction between the topmost atoms on the STM tip and the atoms of the dimers, and the pinning effect induced by Sb atoms, the vacancies or the epitaxial clusters, can drive the structural transformation at the critical bias voltage.

  2. Bi surfactant mediated growth for fabrication of Si/Ge nanostructures and investigation of Si/Ge intermixing by STM

    Energy Technology Data Exchange (ETDEWEB)

    Paul, N.

    2007-10-26

    In the thesis work presented here, we show that Bi is more promising surfactant material than Sb. We demonstrate that by using Bi as a terminating layer on Ge/Si surface, it is possible to distinguish between Si and Ge in Scanning tunnelling microscope (STM). Any attempt to utilize surfactant mediated growth must be preceded by a thorough study of its effect on the the system being investigated. Thus, the third chapter of this thesis deals with an extensive study of the Bi surfactant mediated growth of Ge on Si(111) surface as a function of Ge coverage. The growth is investigated from the single bilayer Ge coverage till the Ge coverage of about 15 BL when the further Ge deposition leads to two-dimensional growth. In the fourth chapter, the unique property of Bi terminating layer on Ge/Si surface to result in an STM height contrast between Si and Ge is explained with possible explanations given for the reason of this apparent height contrast. The controlled fabrication of Ge/Si nanostructures such as nanowires and nanorings is demonstrated. A study on Ge-Si diffusion in the surface layers by a direct method such as STM was impossible previously because of the similar electronic structure of Ge and Si. Since with the Bi terminating surface layer, one is able to distinguish between Ge and Si, the study of intermixing between them is also possible using STM. This method to distinguish between Si and Ge allows one to study intermixing on the nanoscale and to identify the fundamental diffusion processes giving rise to the intermixing. In Chapter 5 we discuss how this could prove useful especially as one could get a local probe over a very narrow Ge-Si interface. A new model is proposed to estimate change in the Ge concentration in the surface layer with time. The values of the activation energies of Ge/Si exchange and Si/Ge exchange are estimated by fitting the experimental data with the model. The Ge/Si intermixing has been studied on a surface having 1 ML Bi ({radical

  3. Sb-Te-Se composite film with high-thermal stability for phase-change memory application

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liangliang; Zheng, Qianqian; Zhang, Xin; Zhu, Xiuwei; Lu, Luyao; Shao, Hehong [Department of Biomedical Engineering, School of Information and Engineering, Wenzhou Medical University, Wenzhou, 325000 (China); Song, Sannian; Song, Zhitang; Li, Le; Zhang, Zhonghua [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai, 200032 (China)

    2016-01-15

    The Sb-Te-Se ternary system with suitable composition material Sb{sub 44}Te{sub 11}Se{sub 45} is proposed for its brilliant thermal stability, which was fabricated by doping with Sb{sub 2}Se{sub 3} to Sb{sub 2}Te. Compared to the traditional Ge{sub 2}Sb{sub 2}Te{sub 5}, Sb{sub 44}Te{sub 11}Se{sub 45} film exhibits a higher crystallization temperature of 220 C, a larger active energy of 4.25 eV, along with ultra-long data retention of 133.8 C for 10 years, which means a brilliant thermal stability. It was found that Sb{sub 2}Se{sub 3} doping could decrease the grain size, which makes Sb{sub 44}Te{sub 11}Se{sub 45} material a more stable material for phase-change memory (PCM) application. For the PCM cell based on Sb{sub 44}Te{sub 11}Se{sub 45}, the resistance ratio between amorphous and crystalline state is up to two orders of magnitude, sufficient for data resolution. From the view-point of thermal stability, Sb{sub 44}Te{sub 11}Se{sub 45} composite film will be a potential phase-change material for high-temperature storage application. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Development of Au-Ge based candidate alloys as an alternative to high-lead content solders

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2010-01-01

    , 150°C for up to 3 weeks and compared with aging at 200°C. After being subjected to high-temperature aging, the microstructure varied a lot in morphology in the case of both Au-Ge-Sb and Au-Ge-Sn candidate alloys while the microstructure remained relatively stable even after long-term thermal aging......-Ge-In and Au-Ge-Sn combinations was determined to be the classic solid solution strengthening. The Au-Ge-Sb combination was primarily strengthened by the refined (Ge) dispersed phase. The aging temperature had a significant influence on the microhardness in the case of the Au-Ge-Sn candidate alloy...

  5. Raman scattering and X-ray photo electron sp ectra of GexSb20Se80-x Glasses%GexSb20Se80-x玻璃的拉曼光谱和X射线光电子能谱∗

    Institute of Scientific and Technical Information of China (English)

    许思维; 王丽; 沈祥

    2015-01-01

    In this paper, we prepare several GexSb20Se80−x glasses (x=5 mol%, 10 mol%, 15 mol%, 17.5 mol%, 20 mol%, and 25 mol%), and measure their Raman and X-ray photoelectron spectra (Ge 3d, Sb 4d, and Se 3d) in order to understand the evolution of the glass structure with chemical composition. We further decompose the spectra into different structural units according to the assignments of these structural units in the previous literature. It is found that the structural units of Se—Se—Se trimers exist in the Se-rich glasses, but the number of the structural units of trimers decreases rapidly with the increase of Ge concentration and finally becomes zero in Ge15Sb20Se65 glass. With the increase of Ge concentration, the quantity of GeSe4/2 tetrahedral structures increases, but the number of SbSe3/2 pyramidal structures remains almost unchanged in the Se-rich glasses. On the other hand, the numbers of Ge—Ge and Sb—Sb homopolar bonds increase with the increase of Ge concentration, but those of the GeSe4/2 tetrahedral and SbSe3/2 pyramidal structures decrease in the Se-poor glasses. Moreover, the Se—Se homopolar bonds exist in all the glasses, and they cannot be completely suppressed. When the composition is close to stochiometric value, the glass is dominated by heteropolar Ge—Se and Sb—Se bonds, but has negligible quantities of Ge—Ge, Sb—Sb and Se—Se homopolar bonds. The transition threshold, rather than the transition predicted by the topological constraint model, occurs at the chemically stoichiometric glasses. This suggests that chemical order, rather than topological order, is a main factor in determining structures and physical properties of Ge—Sb—Se glasses.

  6. Single crystal growth and physical properties of SrCu2As2, SrCu2Sb2 and BaCu2Sb2

    Science.gov (United States)

    Anand, V. K.; Perera, P. K.; Pandey, A.; Goetsch, R. J.; Kreyssig, A.; Johnston, D. C.

    2012-02-01

    We present the physical properties of self-flux-grown single crystals of SrCu2As2, SrCu2Sb2, SrCu2(As0.84Sb0.16)2 and BaCu2Sb2 investigated by magnetic susceptibility χ, specific heat Cp and electrical resistivity ρ vs. temperature T measurements. Contrasting structures occur for SrCu2As2 (ThCr2Si2-type), SrCu2Sb2 (CaBe2Ge2-type) and BaCu2Sb2 (a distorted intergrowth of ThCr2Si2-type and CaBe2Ge2-type unit cells). The χ(T) data for all these compounds exhibit weakly anisotropic diamagnetic behaviors. For 1.8 Debye lattice contributions. From the low-T Cp(T) data, we infer Sommerfeld coefficients γ = 2.2--3.9 mJ/mol,^2 and Debye temperatures θD = 204--246 K@. The electronic properties indicate that these compounds are sp metals containing Cu in a nonmagnetic 3d^10 electronic configuration.ootnotetextD. J. Singh, Phys. Rev. B 79, 153102 (2009).

  7. Pseudomorphic GeSn/Ge (001) heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tonkikh, A. A., E-mail: tonkikh@mpi-halle.de [Max Planck Institute of Microstructure Physics (Germany); Talalaev, V. G. [Martin Luther University Halle-Wittenberg, ZIK SiLi-nano (Germany); Werner, P. [Max Planck Institute of Microstructure Physics (Germany)

    2013-11-15

    The synthesis of pseudomorphic GeSn heterostructures on a Ge (001) substrate by molecular-beam epitaxy is described. Investigations by transmission electron microscopy show that the GeSn layers are defect free and possess cubic diamondlike structure. Photoluminescence spectroscopy reveals interband radiative recombination in the GeSn quantum wells, which is identified as indirect transitions between the subbands of heavy electrons and heavy holes. On the basis of experimental data and modeling of the band structure of pseudomorphic GeSn compounds, the lower boundary of the bowing parameter for the indirect band gap is estimated as b{sub L} {>=} 1.47 eV.

  8. Si1Sb2Te3 phase change material for chalcogenide random access memory

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Song Zhi-Tang; Liu Bo; Liu Wei-Li; Feng Song-Lin; Chen Bomy

    2007-01-01

    This paper investigated phase change Si1Sb2Te3 material for application of chalcogenide random access memory.Current-voltage performance was conducted to determine threshold current of phase change from amorphous phase to polycrystalline phase.The film holds a threshold current about 0.155 mA,which is smaller than the value 0.31 mA of Ge2Sb2Te5 film.Amorphous Si1Sb2Te3 changes to face-centred-cubic structure at~180°C and changes to hexagonal structure at~270°C.Annealing temperature dependent electric resistivity of Si1Sb2Te3 film was studied by four-point probe method.Data retention of the films was characterized as well.

  9. Anyon Superconductivity of Sb

    Science.gov (United States)

    Maksoed, Wh-; Parengkuan, August

    2016-10-01

    In any permutatives to Pedro P. Kuczhynski from Peru, for anyon superconductivity sought EZ Kuchinskii et al.: ``Anion height dependence of Tc & d.o.s of Fe-based Superconductors'', 2010 as well as ``on the basis of electron microscopy & AFM measurements, these phenomena are quantified with focus on fractal dimension, particle perimeter & size of the side branch(tip width) in bert Stegemann et al.:Crystallization of Sb nanoparticles-Pattern Formation & Fractal Growth'', J.PhysChem B., 2004. For dendritic & dendrimer fractal characters shown further: ``antimony denrites were found to be composed of well-crystallized nanoflakes with size 20-4 nm''- Bou Zhau, et al., MaterialLetters, 59 (2005). The alkyl triisopropyl attached in TIPSb those includes in DNA, haemoglobin membrane/fixed-bed reactor for instance quotes in Dragony Fu, Nature Review Cancer, 12 (Feb 2012). Heartfelt Gratitudes to HE. Mr. Prof. Ir. Handojo.

  10. As multifaces de "Através do Brasil"

    Directory of Open Access Journals (Sweden)

    Claudefranklin Monteiro Santos

    2004-01-01

    Full Text Available Este artigo enfoca diferentes aspectos de Através do Brasil, livro de leitura que sintetizou um ideal da pedagogia do início do século XX, comprometida com a implementação de uma conduta cívica para assegurar o fortalecimento da identidade nacional. O livro formou gerações de brasileiros transmitindo uma imagem otimista do país, sem cair no ufanismo exagerado que se verifica em obras contemporâneas do gênero.This article is about different aspects of Através do Brasil, an educational book, which synthesized an ideal pedagogy from the beginning of 20th century, commited with civic behavior to assure national identity. The book taught different generations of Brazilians showing an optimistic image of their Country, avoiding the exaggerated patriotism that appears on similar contemporary books.

  11. Main: SB3NPABC1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available SB3NPABC1 S000434 27-Jan-2004 (last modified) kehi Sclareol box3 (SB3) found at -21...6 of a plasma membrane ATP binding cassette (ABC) transporter gene (NpABC1) in N. plumbaginifolia; Mutation ...in SB3 completely abolished sclareolide-mediated expression; See S ; sclareol; ABC; transporter; SB3; Nicotiana plumbaginifolia (tobacco); TTATGAACAGTAATT ...

  12. Aluminum-centered tetrahedron-octahedron transition in advancing Al-Sb-Te phase change properties.

    Science.gov (United States)

    Xia, Mengjiao; Ding, Keyuan; Rao, Feng; Li, Xianbin; Wu, Liangcai; Song, Zhitang

    2015-02-24

    Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology.

  13. Investigation of (SiC)0.85-Sb3Te alloy for high-reliability PCM applications

    Science.gov (United States)

    Guo, Tianqi; Song, Sannian; Li, Le; Shen, Lanlan; Liu, Bo; Song, Zhitang; Qi, Ming; Feng, Songlin

    2016-10-01

    The reliability and operation speed have long been two great obstacles in phase change memory technology. Thus (SiC)0.85-Sb3Te alloy was proposed to be a new-type phase change material due to its high crystallization temperature (199.7°C) and good data retention ability (118.9°C for 10-year archival life) in this work. The stress accompanying the phase transition in (SiC)0.85-Sb3Te is smaller than those in pure Sb3Te and the traditional material, Ge2Sb2Te5. This is attributed to the fine crystal grain size due to SiC doping, which contributes to the ultrafast reversible operation (5 ns) and good endurance (2.3 × 104 cycles) of (SiC)0.85-Sb3Te based phase change memory cells.

  14. Phase equilibria and crystal structures of the compounds in the Pr-Ni-Sb system at 870 K

    Energy Technology Data Exchange (ETDEWEB)

    Chykhrij, S.I. [Department of Analytical Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya Str. 6, L' viv 79005 (Ukraine)]. E-mail: chykhrij@yahoo.com; Smetana, V.B. [Department of Analytical Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya Str. 6, L' viv 79005 (Ukraine)

    2005-09-01

    The isothermal section of the Pr-Ni-Sb system at 870 K over the whole concentration region has been built using X-ray analysis. At the temperature of the investigation three already known ternary antimonides PrNiSb, {approx}PrNiSb{sub 2} and {approx}PrNi{sub 2}Sb{sub 2} have been confirmed and three compounds {approx}Pr{sub 5}NiSb{sub 2}, PrNiSb{sub 3}, and PrNi{sub 2+x}Sb{sub 2-y} have been synthesized for the first time. The crystal structures of the obtained compounds belong to the following structure types: PrNiSb-ZrBeSi type, space group P6{sub 3}/mmc, a = 0.43838(2) nm, c = 0.81068(6) nm; PrNiSb{sub 3}-CeNiSb{sub 3} type, space group Pbcm, a = 1.2579(2) nm, b = 0.62051(8) nm, c = 1.8371(2) nm; {approx}Pr{sub 5}NiSb{sub 2}-structure related to Y{sub 5}Ni {sub x}Sb{sub 3-x}-type, space group Pnma, a = 1.2457(1) nm, b = 0.9159(1) nm, c = 0.8118(1) nm. The PrNi{sub 2}Sb{sub 2} compound crystallizes with an orthorhombic or monoclinic unit cell and a structure related to the tetragonal CaBe{sub 2}Ge{sub 2} type. The PrNi{sub 2+x}Sb{sub 2-y} antimonide has a small homogeneity region and crystallizes with a tetragonal unit cell (space group P4/nmm) and lattice parameters a = 0.431256(9) - 0.4319(1) nm, c = 0.99830(2) - 1.0092(3) nm. The existence of a considerable homogeneity region of the PrNi{sub 0.62-1.35}Sb{sub 2} compound is caused by a deficiency of Ni atoms or their excess compared to the initial structure of stoichiometric composition and a corresponding transition from the HfCuSi{sub 2} type to the CaBe{sub 2}Ge{sub 2} type with preservation of the unit cell symmetry (a 0.43539(4) - 0.44130(2) nm, c = 0.9653(1) - 0.97643(5) nm)

  15. Study of strain in partially relaxed Ge epilayers on Si(100) substrate

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ge epilayers of different thicknesses are grown by molecular-beam epitaxy with Sb as a surfactant on SI(100) substrates,X-ray diffraction illustrates that these Ge thin films are partially strained.and the strains decrease gradually with increasing epilayer thickness,Raman spectra reveal a downward shift of the Ge-Ge mode peak as the epilayer thickness increases.In the regions of high strain,the relationship between the Raman shift of this mode and the strain in the partially relaxed samples is considerably different from the linear relationship reported before,which is mainly attributed to the spatial confinement effect of phonons in a nanocrystal.

  16. N-doped Sb{sub 2}Te phase change materials for higher data retention

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Min, E-mail: minzhu@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Graduate School of the Chinese Academy of Sciences, 100080 Beijing (China); Wu Liangcai; Rao Feng; Song Zhitang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Li Xuelai [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Graduate School of the Chinese Academy of Sciences, 100080 Beijing (China); Peng Cheng [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Zhou Xilin; Ren Kun [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Graduate School of the Chinese Academy of Sciences, 100080 Beijing (China); Yao Dongning; Feng Songlin [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China)

    2011-10-13

    Highlights: > Crystallization temperatures of the N-doped Sb{sub 2}Te films increase remarkably. > The E{sub a} of N-doped Sb{sub 2}Te films increase first, and then decrease. > The best 10-years lifetime at temperature up to 141 deg. C is found in Sb{sub 2}TeN1 films. > The power consumption of PCRAM test cell based on Sb{sub 2}TeN1 film is low. - Abstract: Crystallization temperatures of the Sb{sub 2}Te films increase remarkably from 139.4 deg. C to 223.0 deg. C as the N{sub 2} flow rates increasing from 0 sccm to 1.5 sccm. Electrical conduction activation energies for amorphous and crystalline states increase by doping nitrogen. A small amount of nitrogen atoms can locate at interstitial sites in the hexagonal structure, generating a strain field, and improving the thermal stability of amorphous state. The best 10-years lifetime at temperature up to 141 deg. C is found in Sb{sub 2}TeN{sub 1} films. Doping excessively high nitrogen in Sb{sub 2}Te film will form nitride and make Te separate out. As a result, the activation energy for crystallization decreases instead, accompanying with the deterioration of thermal stability. The power consumption of PCRAM test cell based on Sb{sub 2}TeN{sub 1} film is ten times lower than that of PCRAM device using Ge{sub 2}Sb{sub 2}Te{sub 5} films.

  17. Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds

    Science.gov (United States)

    Gabardi, Silvia; Caravati, Sebastiano; Los, Jan H.; Kühne, Thomas D.; Bernasconi, Marco

    2016-05-01

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In3SbTe2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the use of the Becke-Lee-Yang-Parr functional provides models with a much larger fraction of In atoms in a tetrahedral bonding geometry with respect to previous results obtained with the most commonly used Perdew-Becke-Ernzerhof functional. This outcome is at odd with the properties of Ge2Sb2Te5 phase change compound for which the two exchange-correlation functionals yield very similar results on the structure of the amorphous phase.

  18. Improved thermoelectric performance of (Fe,Co)Sb{sub 3}-type skutterudites from first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Izaak [Department of Materials Science and Engineering, Boise State University, Idaho 83725 (United States); Her, Logan Ju-Yee [Department of Science, Math and Engineering, Cosumnes River College, Sacramento, California 95823 (United States); Su, Xianli; Yan, Yonggao [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Wong-Ng, Winnie [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Li, Lan [Department of Materials Science and Engineering, Boise State University, Idaho 83725 (United States); Center for Advanced Energy Studies, Idaho Falls, Idaho 83401 (United States)

    2016-02-07

    Skutterudite materials have been considered as promising thermoelectric candidates due to intrinsically good electrical conductivity and tailorable thermal conductivity. Options for improving thermal-to-electrical conversion efficiency include identifying novel materials, adding filler atoms, and substitutional dopants. Incorporating filler or substitutional dopant atoms in the skutterudite compounds can enhance phonon scattering, resulting in reduction of thermal conductivity, as well as improving electrical conductivity. The structures, electronic properties, and thermal properties of double-filled Ca{sub 0.5}Ce{sub 0.5}Fe{sub 4}Sb{sub 12} and Co{sub 4}Sb{sub 12−2x}Te{sub x}Ge{sub x} compounds (x = 0, 0.5, 1, 2, 3, and 6) have been studied using density functional theory-based calculations. Both Ca/Ce filler atoms in FeSb{sub 3} and Te/Ge substitution in CoSb{sub 3} cause a decrease in lattice constant for the compounds. As Te/Ge substitution concentration increases, lattice constant decreases and structural distortion of pnictogen rings in the compounds occurs. This indicates a break in cubic symmetry of the structure. The presence of fillers and substitutions cause an increase in electrical conductivity and a gradual decrease in electronic band gap. A transition from direct to indirect band-gap semiconducting behavior is found at x = 3. Phonon density of states for both compounds indicate phonon band broadening by the incorporation of fillers and substitutional atoms. Both systems are also assumed to have acoustic-mode-dominated lattice thermal conductivity. For the Co{sub 4}Sb{sub 12−2x}Te{sub x}Ge{sub x} compounds, x = 3 has the lowest phonon dispersion gradient and lattice thermal conductivity, agreeing well with experimental measurements. Our results exhibit the improvement of thermoelectric properties of skutterudite compounds through fillers and substitutional doping.

  19. Si-Ge-metal ternary phase diagram calculations

    Science.gov (United States)

    Fleurial, J. P.; Borshchevsky, A.

    1990-01-01

    Solution crystal growth and doping conditions of Si-Ge alloys used for high-temperature thermoelectric generation are determined here. Liquid-phase epitaxy (LPE) has been successfully employed recently to obtain single-crystalline homogeneous layers of Si-Ge solid solutions from a liquid metal solvent. Knowledge of Si-Ge-metallic solvent ternary phase diagrams is essential for further single-crystal growth development. Consequently, a thermodynamic equilibrium model was used to calculate the phase diagrams of the Si-Ge-M systems, including solid solubilities, where M is Al, Ga, In, Sn, Pb, Sb, or Bi. Good agreement between calculated liquidus and solidus data and experimental DTA and microprobe results was obtained. The results are used to compare the suitability of the different systems for crystal growth (by LPE-type process).

  20. Strained monolayer germanene with 1 × 1 lattice on Sb(111)

    Science.gov (United States)

    Gou, Jian; Zhong, Qing; Sheng, Shaoxiang; Li, Wenbin; Cheng, Peng; Li, Hui; Chen, Lan; Wu, Kehui

    2016-12-01

    Monolayer germanene, the germanium analog of graphene, has been successfully synthesized on Sb(111) surface via molecular beam epitaxy. Scanning tunneling microscopy revealed a dendrite structure at low Ge coverage and mosaic patterns at high coverage, both with local 1 × 1 lattice. First-principle calculations confirmed the 1 × 1 low-buckled structure of germanene. The dendrite and mosaic patterns stem from strain modulation induced by large lattice mismatch between germanene and Sb substrate. This work provide a new system to explore the physical properties and applications of germanene.

  1. Surfactant-mediated epitaxy of thin germanium films on SiGe(001) virtual substrates

    Science.gov (United States)

    Schmidt, J.; Tetzlaff, D.; Bugiel, E.; Wietler, T. F.

    2017-01-01

    We report on the impact of a surfactant on the growth mode and strain relaxation of thin Ge films on Si0.21Ge0.79 virtual substrates grown by surfactant mediated epitaxy on Si(001) wafers. Ge epitaxy without surfactant results in island formation after deposition of only 5 nm Ge. A certain part of the strain in the Ge islands is relaxed via interfacial misfit dislocations, which are located within the core part of the islands. We discuss the possibilities for the occurrence of three-dimensional growth at low Ge layer thickness. The use of Sb as a surfactant suppresses three-dimensional islanding and enables the growth of smooth pseudomorphically strained Ge films on Si0.21Ge0.79(001) virtual substrates up to a thickness of 10 nm. At thicknesses higher than 20 nm, the films relax via the formation of a misfit dislocation network at the Ge/ Si1-xGex interface. The surface roughness of up to 30 nm thick layers is below 1.6 nm. Our experimental results corroborate the calculated thickness for plastic relaxation of Ge on Si1-xGex. The effect of the surfactant on the growth of the virtual substrate and on the subsequent growth of Ge on Si0.21Ge0.79 is discussed.

  2. [Sb4Au4Sb4]2-: A designer all-metal aromatic sandwich

    Science.gov (United States)

    Tian, Wen-Juan; Guo, Jin-Chang; Li, Da-Zhi; You, Xue-Rui; Wang, Ying-Jin; Sun, Zhong-Ming; Zhai, Hua-Jin

    2016-07-01

    We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4]2-. The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4]+[Au4]4-[Sb4]+, showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4]+ ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ˜1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.

  3. Main: SB1NPABC1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available SB1NPABC1 S000435 27-Jan-2004 (last modified) kehi Sclareol box1 (SB1) found at -82...7 of a plasma membrane ATP binding cassette (ABC) transporter gene (NpABC1) in N. plumbaginifolia; Mutation ...in SB3 completely abolished sclareolide-mediated expression; See S ; scalareol; diterpene; ABC; transporter; Nicotiana plumbaginifolia (tobacco); CACTAACACAAAGTAA ...

  4. Conducting state of GeTe by defect-induced topological insulating order

    Science.gov (United States)

    Kim, Jinwoong; Jhi, Seung-Hoon

    2012-02-01

    Topological insulating order protected by time-reversal symmetry is robust under structural disorder. Interestingly, recent studies on phase change materials like GeSbTe showed that their topological insulating order is sensitive to atomic stacking sequences. It was also shown that their structural phase transition is correlated with topological insulating order. GeTe, a well-known phase change material, is trivial insulator in its equilibrium structure. In this study, we discuss how atomic defects such as Ge tetrahedral defect observed in amorphous GeTe can change its topological insulating order based on first-principles calculations and model Hamiltonian. We also investigated the critical density of such tetrahedral defects to induce topological insulating order in GeTe. Our study will help explore hidden orders in GeTe.

  5. Controllable crystallization and enhanced amorphous stability of Sb-Te films modified by Ag-doping

    Science.gov (United States)

    Zhong, Juechen; Luo, Yang; Gu, Ting; Wang, Zhenglai; Jiang, Kefeng; Wang, Guoxiang; Lu, Yegang

    2016-10-01

    Ag-doped Sb-Te films were deposited by magnetron co-sputtering and the structure, electrical, optical and thermal properties were analyzed. The results show that Ag-doping restrains crystal grain size, and changes a preferred orientation of the crystalline phase. The crystallization temperature is increased due to the Ag addition. Both amorphous resistance and crystalline resistance are enhanced and the resistance ratio reaches ˜104. Compared with Ge2Sb2Te5, Ag26.82(Sb3Te)73.18 film exhibits a better amorphous thermal stability, a higher crystallization temperature (˜166 °C), a wider optical band gap (0.515 eV), a larger crystallization activation energy (3.17 eV) as well as a better 10 years data retention at 92 °C.

  6. Bonding in ZnSb

    DEFF Research Database (Denmark)

    Bjerg, Lasse; Madsen, Georg K. H.; Iversen, Bo Brummerstedt

    Thermoelectric materials are capable of converting waste heat into usable electric energy. The conversion efficiency depends critically on the electronic band structure. Theoretical calculations predict the semiconducting ZnSb to have a promising efficiency if it is n-doped. The details...

  7. Si2Sb2Te5 phase change material studied by an atomic force microscope nano-tip

    Institute of Scientific and Technical Information of China (English)

    Liu Yanbo; Zhang Ting; Niu Xiaoming; Song Zhitang; Min Guoquan; Zhang Jing; Zhou Weimin; Wan Yongzhong; Zhang Jianping; Li Xiaoli; Feng Songlin

    2009-01-01

    The Si2Sb2Te5 phase change material has been studied by applying a nano-tip (30 nm in diameter) on an atomic force microscopy system. Memory switching from a high resistance state to a low resistance state has been achieved, with a resistance change of about 1000 times. In a typical Ⅰ-Ⅴ curve, the current increases significantly after the voltage exceeds~4.3 V. The phase transformation of a Si2Sb2Te5 film was studied in situ by means of in situ X-ray diffraction and temperature dependent resistance measurements. The thermal stability of Si2Sb2Te5 and Ge2Sb2Te5 was characterized and compared as well.

  8. Incorporation of Sb and As in MBE grown GaAsxSb1-x layers

    Science.gov (United States)

    Zederbauer, Tobias; Andrews, Aaron Maxwell; MacFarland, Don; Detz, Hermann; Schrenk, Werner; Strasser, Gottfried

    2017-03-01

    With the increasing interest in low effective mass materials for intersubband devices, mixed As-Sb compounds, like GaAsxSb1-x or AlxIn1-xAsySb1-y, gain more and more attention. The growth of these materials, however, still provides significant challenges due to the complex interaction between As and Sb. In this work, we provide an in-depth study on the incorporation of Sb into the GaAsxSb1-x layers and compare our findings to the present literature on this topic. It is found that both the composition and the crystal quality of GaAsxSb1-x layers are strongly influenced by the growth rate due to the As-for-Sb exchange reaction which takes place at the growing surface, and that high crystal quality can be achieved when the growth is performed under Sb limited conditions.

  9. Low-Energy Amorphization of Ti1Sb2Te5 Phase Change Alloy Induced by TiTe2 Nano-Lamellae

    Science.gov (United States)

    Ding, Keyuan; Rao, Feng; Lv, Shilong; Cheng, Yan; Wu, Liangcai; Song, Zhitang

    2016-07-01

    Increasing SET operation speed and reducing RESET operation energy have always been the innovation direction of phase change memory (PCM) technology. Here, we demonstrate that ∼87% and ∼42% reductions of RESET operation energy can be achieved on PCM cell based on stoichiometric Ti1Sb2Te5 alloy, compared with Ge2Sb2Te5 and non-stoichiometric Ti0.4Sb2Te3 based PCM cells at the same size, respectively. The Ti1Sb2Te5 based PCM cell also shows one order of magnitude faster SET operation speed compared to that of the Ge2Sb2Te5 based one. The enhancements may be caused by substantially increased concentration of TiTe2 nano-lamellae in crystalline Ti1Sb2Te5 phase. The highly electrical conduction and lowly thermal dissipation of the TiTe2 nano-lamellae play a major role in enhancing the thermal efficiency of the amorphization, prompting the low-energy RESET operation. Our work may inspire the interests to more thorough understanding and tailoring of the nature of the (TiTe2)n(Sb2Te3)m pseudobinary system which will be advantageous to realize high-speed and low-energy PCM applications.

  10. The fire ant social chromosome supergene variant Sb shows low diversity but high divergence from SB.

    Science.gov (United States)

    Pracana, Rodrigo; Priyam, Anurag; Levantis, Ilya; Nichols, Richard A; Wurm, Yannick

    2017-02-21

    Variation in social behavior is common yet little is known about the genetic architectures underpinning its evolution. A rare exception is in the fire ant Solenopsis invicta: Alternative variants of a supergene region determine whether a colony will have exactly one or up to dozens of queens. The two variants of this region are carried by a pair of "social chromosomes", SB and Sb, which resemble a pair of sex chromosomes. Recombination is suppressed between the two chromosomes in the supergene region. While the X-like SB can recombine with itself in SB/SB queens, recombination is effectively absent in the Y-like Sb because Sb/Sb queens die before reproducing. Here, we analyze whole genome sequences of eight haploid SB males and eight haploid Sb males. We find extensive SB-Sb di↵erentiation throughout the >19Mb long supergene region. We find no evidence of "evolutionary strata" with different levels of divergence comparable to those reported in several sex chromosomes. A high proportion of substitutions between the SB and Sb haplotypes are nonsynonymous, suggesting inefficacy of purifying selection in Sb sequences, similar to that for Y-linked sequences in XY systems. Finally, we show that the Sb haplotype of the supergene region has 635-fold less nucleotide diversity than the rest of the genome. We discuss how this reduction could be due to a recent selective sweep affecting Sb specifically or associated with a population bottleneck during the invasion of North America by the sampled population. This article is protected by copyright. All rights reserved.

  11. Stoichiometry dependence of resistance drift phenomena in amorphous GeSnTe phase-change alloys

    Science.gov (United States)

    Luckas, J.; Piarristeguy, A.; Bruns, G.; Jost, P.; Grothe, S.; Schmidt, R. M.; Longeaud, C.; Wuttig, M.

    2013-01-01

    In phase-change materials, the amorphous state resistivity increases with time following a power law ρ ∝ (t/t0)αRD. This drift in resistivity seriously hampers the potential of multilevel-storage to achieve an increased capacity in phase-change memories. This paper presents the stoichiometric dependence of drift phenomena in amorphous GeSnTe systems (a-GeSnTe) and other known phase-change alloys with the objective to identify low drift materials. The substitution of Ge by Sn results in a systematic decrease of the drift parameter from a-GeTe (αRD = 0.129) to a-Ge2Sn2Te4 (αRD = 0.053). Furthermore, with increasing Sn content a decrease in crystallization temperature, trap state density, optical band gap, and activation energy for electronic conduction is observed. In a-GeSnTe, a-GeSbTe, and a-AgInSbTe alloys as well, the drift parameter αRD correlates to the activation energy for electronic conduction. This study indicates that low drift materials are characterized by low activation energies of electronic conduction. The correlation found between drift and activation energy of electronic conduction manifests a useful criterion for material optimization.

  12. GeSn/Ge multiquantum well photodetectors on Si substrates.

    Science.gov (United States)

    Oehme, M; Widmann, D; Kostecki, K; Zaumseil, P; Schwartz, B; Gollhofer, M; Koerner, R; Bechler, S; Kittler, M; Kasper, E; Schulze, J

    2014-08-15

    Vertical incidence GeSn/Ge multiquantum well (MQW) pin photodetectors on Si substrates were fabricated with a Sn concentration of 7%. The epitaxial structure was grown with a special low temperature molecular beam epitaxy process. The Ge barrier in the GeSn/Ge MQW was kept constant at 10 nm. The well width was varied between 6 and 12 nm. The GeSn/Ge MQW structures were grown pseudomorphically with the in-plane lattice constant of the Ge virtual substrate. The absorption edge shifts to longer wavelengths with thicker QWs in agreement with expectations from smaller quantization energies for the thicker QWs.

  13. Sequential and simultaneous adsorption of Sb(III) and Sb(V) on ferrihydrite: Implications for oxidation and competition.

    Science.gov (United States)

    Qi, Pengfei; Pichler, Thomas

    2016-02-01

    Antimony (Sb) is a naturally occurring element of growing environmental concern whose toxicity, adsorption behavior and other chemical properties are similar to that of arsenic (As). However, less is known about Sb compared to As. Individual and simultaneous adsorption experiments with Sb(III) and Sb(V) were conducted in batch mode with focus on the Sb speciation of the remaining liquid phase during individual Sb(III) adsorption experiments. The simultaneous adsorption and oxidation of Sb(III) was confirmed by the appearance of Sb(V) in the solution at varying Fe/Sb ratios (500, 100 and 8) and varying pH values (3.8, 7 and 9). This newly formed Sb(V) was subsequently removed from solution at a Fe/Sb ratio of 500 or at a pH of 3.8. However, more or less only Sb(V) was observed in the liquid phase at the end of the experiments at lower Fe/Sb ratios and higher pH, indicating that competition took place between the newly formed Sb(V) and Sb(III), and that Sb(III) outcompeted Sb(V). This was independently confirmed by simultaneous adsorption experiments of Sb(III) and Sb(V) in binary systems. Under such conditions, the presence of Sb(V) had no influence on the adsorption of Sb(III) while Sb(V) adsorption was significantly inhibited by Sb(III) over a wide pH range (4-10). Thus, in the presence of ferrihydrite and under redox conditions, which allow the presence of both Sb species, Sb(V) should be the dominant species in aquatic environments, since Sb(III) is adsorbed preferentially and at the same time oxidized to Sb(V).

  14. Room temperature direct band gap emission characteristics of surfactant mediated grown compressively strained Ge films

    Science.gov (United States)

    Katiyar, Ajit K.; Grimm, Andreas; Bar, R.; Schmidt, Jan; Wietler, Tobias; Joerg Osten, H.; Ray, Samit K.

    2016-10-01

    Compressively strained Ge films have been grown on relaxed Si0.45Ge0.55 virtual substrates using molecular beam epitaxy in the presence of Sb as a surfactant. Structural characterization has shown that films grown in the presence of surfactant exhibit very smooth surfaces with a relatively higher strain value in comparison to those grown without any surfactant. The variation of strain with increasing Ge layer thickness was analyzed using Raman spectroscopy. The strain is found to be reduced with increasing film thickness due to the onset of island nucleation following Stranski-Krastanov growth mechanism. No phonon assisted direct band gap photoluminescence from compressively strained Ge films grown on relaxed Si0.45Ge0.55 has been achieved up to room temperature. Excitation power and temperature dependent photoluminescence have been studied in details to investigate the origin of different emission sub-bands.

  15. Doppler-shift attenuation method lifetime measurements in {sup 115}Sb and {sup 117}Sb

    Energy Technology Data Exchange (ETDEWEB)

    Bucurescu, D.; Cata-Danil, I.; Ilas, G.; Ivascu, M.; Stroe, L.; Ur, C.A. [Institute of Atomic Physics, P.O. Box MG-6, Bucharest 76900 (Romania)

    1995-08-01

    The lifetimes of several low-lying excited levels in {sup 115}Sb and {sup 117}Sb have been measured by using the DSA method in the {sup 115,117}Sn({ital p},{ital n}{gamma}){sup 115,117}Sb reactions, respectively. The structure of these nuclei is discussed in the frame of the interacting boson-fermion model.

  16. GaSb film growth by liquid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cruz, M.L.; Martinez-Juarez, J.; Lopez-Salazar, P. [CIDS-ICUAP, BUAP, Av. 14 Sur y San Claudio, C.U. Edif.103C, Col. Sn Manuel, C.P. 72570, Puebla, Pue. (Mexico); Diaz, G.J. [Centro de Investigacion y Estudios Avanzados, IPN, Av. IPN 2508, Col. Sn. Pedro Zacatenco, C.P. 07360, D.F. (Mexico)

    2010-04-15

    Doped GaSb (Gallium Antimonide) films on p-GaSb substrates have been obtained by means of a low-cost and fast-growth method: the liquid phase epitaxy (LPE) technique. The growth temperature was 400 C, and the growth time was varied between1 and 5 min. Characterization of the films was performed by means of high resolution X-ray Diffraction, low temperature-photoluminescence and current-voltage curve measurements. The X-ray diffraction pattern confirms a zincblende-type crystal structure with a high-thin peak centred at 30.36 . The PL spectra at 27 K allowed to confirm the band-gap energy to be 0.8 eV and the I-V curves presented a PN junction behavior which corresponds to the obtained structured. Metal contacts of Au-Zn and Au-Ge were placed to perform electrical characterization (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. InAlAsSb/InGaSb Double Heterojunction Bipolar Transistor

    Science.gov (United States)

    2005-03-01

    Papanicolaou An npn double heterojunction bipolar transistor has been made using In0.27Ga0.73Sb for the base and two different InxAl1-xAsySb1-y alloys...zSb base constitute a new group of semiconductors for making an npn double heterojunction bipolar transistor (DHBT). The group of alloys reported here...MAR 2005 2. REPORT TYPE 3. DATES COVERED 00-00-2005 to 00-00-2005 4. TITLE AND SUBTITLE InAlAsSb/InGaSb double heterojunction bipolar transistor

  18. Dissimilatory Sb(V) reduction by microorganisms isolated from Sb-contaminated sediment

    Science.gov (United States)

    Dovick, M. A.; Kulp, T. R.

    2013-12-01

    Mining and smelting are major sources of trace metal contamination in freshwater systems. Arsenic (As) is a common contaminant derived from certain mining operations and is a known toxic metalloid and carcinogen. Antimony (Sb) is listed as a pollutant of priority interest by the EPA and is presumed to share similar geochemical and toxicological properties with arsenic. Both elements can occur in four different oxidation states (V, III, 0, and -III) under naturally occurring conditions. In aqueous solutions As(V) and Sb(V) predominate in oxygenated surface waters whereas As(III) and Sb(III) are stable in anoxic settings. Numerous studies have examined microbiological redox pathways that utilize As(V) as a terminal electron acceptor for anaerobic respiration, however there have been few studies on microbial mechanisms that may affect the biogeochemical cycling of Sb in the environment. Here we report bacterial reduction of Sb(V) to Sb(III) in anoxic enrichment cultures and bacterial isolates grown from sediment collected from an Sb contaminated pond at a mine tailings site in Idaho (total pond water Sb concentration = 235.2 +/- 136.3 ug/L). Anaerobic sediment microcosms (40 mL) were established in artificial freshwater mineral salt medium, amended with millimolar concentrations of Sb(V), acetate or lactate, and incubated at 27°C for several days. Antimony(V), lactate, and acetate concentrations were monitored during incubation by High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC). Live sediment microcosms reduced millimolar amendments of Sb(V) to Sb(III) coupled to the oxidation of acetate and lactate, while no activity occurred in killed controls. Enrichment cultures were established by serially diluting Sb(V)-reducing microcosms in mineral salt medium with Sb(V) and acetate, and a Sb(V)-reducing bacterial strain was isolated by plating on anaerobic agar plates amended with millimolar Sb(V) and acetate. Direct cell counting demonstrated that

  19. Research on anti-contact fatigue performance of grease containing nano SbSbS4 particles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Feng; SONG Bao-yu; QU Jian-jun; LIU Wei-min

    2005-01-01

    Effects of nano SbSbS4particles on contact fatigue life of a steel ball were evaluated on a self-made ball-rod contact fatigue tester. The anti-fatigue mechanisms of SbSbS4 additive were analyzed by means of SEM and EDAX. It was shown that, when the grease contained SbSbS4, contact fatigue life was improved compared with that of base grease. Nanoparticle absorption action, nanoparticle infiltration action, and extreme pressure and anti-friction performance, explained why SbSbS4 increased the contact fatigue life of the steel ball tested.

  20. Thermoelectric properties of Mg2X (X = Si, Ge) based bulk and quantum well systems

    Science.gov (United States)

    Yelgel, Övgü Ceyda

    2017-01-01

    Mg2X (X = Si, Ge) compounds are promising thermoelectric materials for middle temperature applications due to good thermoelectric properties, nontoxicity, and abundantly available constituent elements. So far, these materials used in applications have all been in bulk form. Herein we report a full theory of thermoelectric transport properties of 3D bulk and 2D quantum well systems. The main aim of this present work is to show the effect of quantum confinement on the enhancement of the thermoelectric figure of merit theoretically. Results are given for n-type Mg2 Si0.5 Ge0.5 solid solutions and n-type Mg2Si/Mg2Ge/Mg2Si quantum well systems where the values of well widths are taken as 10 nm, 15 nm, and 20 nm, respectively. The n-type doping is made by using Sb- and La-elements as dopants. Experimental results for solid solutions are included to provide demonstration of proof of principle for the theoretical model applied for 3D bulk structures. The maximum thermoelectric figure of merits of Lax Mg2 -x Si0.49 Ge0.5 Sb0.01 solid solutions are obtained to be 0.64 and 0.56 at 800 K for x = 0 and x = 0.01 sample, respectively. While, at the same temperature, due to the relatively low phonon thermal conductivity the state-of-the-art ZT values of 2.41 and 2.26 have been attained in the Mg2Si/Mg2Ge/Mg2Si quantum well samples with 0.01 wt. % Sb-doped and 0.01 wt. % Sb- and 0.01 wt. % La-doped, respectively.

  1. Determination of the laterally homogeneous barrier height of palladium Schottky barrier diodes on n-Ge (111)

    CSIR Research Space (South Africa)

    Chawanda, A

    2011-05-01

    Full Text Available The authors have studied the experimental linear relationship between barrier heights and ideality factors for palladium (Pd) on bulk-grown (1 1 1) Sb-doped n-type germanium (Ge) metal-semiconductor structures with a doping density of about 2...

  2. Determination of As, Se and Sb in different trades and blends of tobacco by neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Francisconi, Lucilaine S.; Damatto, Sandra R.; Silva, Paulo S.C. da, E-mail: pscsilva@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    The concentrations of As, Se and Sb were determined in two different cigarette trades (M and F). For each trade, four blends were selected for analysis: red, blue, silver and gold for M and red, blue, silver and fresh for F. The As, Se and Sb concentrations were determined by neutron activation analysis. For the analysis the samples were dried to eliminate moisture and the results were given in dry weight. Samples were irradiated together reference standards materials in the IEA-R1 IPEN reactor and counted in Ge-hiperpure detector. It was observed that As and Sb showed higher concentrations in M than in F and no significant differences were observed between the blends. (author)

  3. Te-free environmental materials of TixSb2.19Se applied in phase change memory

    Science.gov (United States)

    Zhu, Yueqin; Song, Sannian; Li, Le; Xie, Huaqing; Song, Zhitang; Liu, Bo; Wu, Junxing

    2016-10-01

    Environmental friendly Te-free phase change material of TixSb2.19Se was investigated for PCM application. As the important thermal properties, the crystallization temperature (Tc) and data retention for ten years for the best selected composition Ti0.34Sb2.19Se (TSS) are 234°C and 160‡C, respectively. Detection of the crystal structure of TSS by means of XRD, TEM and XPS reveals that the grains are more uniform compared with Ge2Sb2Te5 (GST). The Set and Reset operation voltages for TSS-based phase change memory devices are much lower than those of conventional GST-based ones. Remarkably, the TSS device exhibits an extremely high phase change speed of 10 ns.

  4. Vertical gradient solution growth of N-type Si0.73Ge0.27 bulk crystals with homogeneous composition and its thermoelectric properties

    Science.gov (United States)

    Omprakash, M.; Arivanandhan, M.; Sabarinathan, M.; Koyama, T.; Momose, Y.; Ikeda, H.; Tatsuoka, H.; Aswal, D. K.; Bhattacharya, S.; Inatomi, Y.; Hayakawa, Y.

    2016-05-01

    Compositionally homogeneous Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 bulk crystals were grown by a vertical gradient solution growth method. The sandwich sample Si (seed)/Sb-doped Ge/ Si(feed) was set up inside a furnace under a mild temperature gradient 0.57 °C/mm for homogeneous growth. The Si composition was analyzed by electron probe micro- analysis (EPMA). It revealed that the Si composition was homogeneous and the lengths of the Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 bulk crystals were 18.3 and 15.1 mm, respectively. Grain distribution was investigated by electron backscattered diffraction spectrum (EBSD). The Seebeck coefficients (-440 and -426 μV/K) of Sb-doped (5×1018 and 1×1019 cm-3) Si0.73Ge0.27 were higher than the reported value (-211 μV/K) of P-doped (5×1019 cm-3) Si0.8Ge0.2 at room temperature. Thermal conductivity of Ga and Sb-doped SiGe was decreased with temperature due to scattering of phonon at the temperature range between 313 and 913 K. The maximum ZT values of Ga and Sb-doped SiGe were 0.34 and 0.44 at 820 K, respectively. The ZT values of Ga and Sb-doped SiGe were higher (0.07 and 0.13) than the reported value of Ga-doped Si0.81Ge0.19 (0.05) and P-doped (5×1019 cm-3) Si0.8Ge0.2 bulk crystals at room temperature. The improvement in ZT value was caused by a decrease of thermal conductivity which related to a composition of the alloy and doping concentration in the crystal.

  5. Optical Properties of GaSb Nanofibers

    Directory of Open Access Journals (Sweden)

    Perez-Bergquist Alejandro

    2011-01-01

    Full Text Available Abstract Amorphous GaSb nanofibers were obtained by ion beam irradiation of bulk GaSb single-crystal wafers, resulting in fibers with diameters of ~20 nm. The Raman spectra and photoluminescence (PL of the ion irradiation-induced nanofibers before and after annealing were studied. Results show that the Raman intensity of the GaSb LO phonon mode decreased after ion beam irradiation as a result of the formation of the amorphous nanofibers. A new mode is observed at ~155 cm-1 both from the unannealed and annealed GaSb nanofiber samples related to the A1g mode of Sb–Sb bond vibration. Room temperature PL measurements of the annealed nanofibers present a wide feature band at ~1.4–1.6 eV. The room temperature PL properties of the irradiated samples presents a large blue shift compared to bulk GaSb. Annealed nanofibers and annealed nanofibers with Au nanodots present two different PL peaks (400 and 540 nm, both of which may originate from Ga or O vacancies in GaO. The enhanced PL and new band characteristics in nanostructured GaSb suggest that the nanostructured fibers may have unique applications in optoelectronic devices.

  6. Sb-Te Phase-change Materials under Nanoscale Confinement

    Science.gov (United States)

    Ihalawela, Chandrasiri A.

    Size, speed and efficiency are the major challenges of next generation nonvolatile memory (NVM), and phase-change memory (PCM) has captured a great attention due to its promising features. The key for PCM is rapid and reversible switching between amorphous and crystalline phases with optical or electrical excitation. The structural transition is associated with significant contrast in material properties which can be utilized in optical (CD, DVD, BD) and electronic (PCRAM) memory applications. Importantly, both the functionality and the success of PCM technology significantly depend on the core material and its properties. So investigating PC materials is crucial for the development of PCM technology to realized enhanced solutions. In regards to PC materials, Sb-Te binary plays a significant role as a basis to the well-known Ge-Sb-Te system. Unlike the conventional deposition methods (sputtering, evaporation), electrochemical deposition method is used due to its multiple advantages, such as conformality, via filling capability, etc. First, the controllable synthesis of Sb-Te thin films was studied for a wide range of compositions using this novel deposition method. Secondly, the solid electrolytic nature of stoichiometric Sb2Te3 was studied with respect to precious metals. With the understanding of 2D thin film synthesis, Sb-Te 1D nanowires (18 - 220 nm) were synthesized using templated electrodeposition, where nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. In order to gain the controllability over the deposition in high aspect ratio structures, growth mechanisms of both the thin films and nanowires were investigated. Systematic understanding gained thorough previous studies helped to formulate the ultimate goal of this dissertation. In this dissertation, the main objective is to understand the size effect of PC materials on their phase transition properties. The reduction of effective memory cell size in conjunction with

  7. Compact analytical model for single gate AlInSb/InSb high electron mobility transistors

    Institute of Scientific and Technical Information of China (English)

    S.Theodore Chandra; N.B.Balamurugan; G.Subalakshmi; T.Shalini; G.Lakshmi Priya

    2014-01-01

    We have developed a 2D analytical model for the single gate AlInSb/InSb HEMT device by solving the Poisson equation using the parabolic approximation method.The developed model analyses the device performance by calculating the parameters such as surface potential,electric field distribution and drain current.The high mobility of the AlInSb/InSb quantum makes this HEMT ideal for high frequency,high power applications.The working of the single gate AlInSb/InSb HEMT device is studied by considering the variation of gate source voltage,drain source voltage,and channel length under the gate region and temperature.The carrier transport efficiency is improved by uniform electric field along the channel and the peak values near the source and drain regions.The results from the analytical model are compared with that of numerical simulations (TCAD) and a good agreement between them is achieved.

  8. Photoluminescence and electroluminescence from Ge/strained GeSn/Ge quantum wells

    Science.gov (United States)

    Lin, Chung-Yi; Huang, Chih-Hsiung; Huang, Shih-Hsien; Chang, Chih-Chiang; Liu, C. W.; Huang, Yi-Chiau; Chung, Hua; Chang, Chorng-Ping

    2016-08-01

    Ge/strained GeSn/Ge quantum wells are grown on a 300 mm Si substrate by chemical vapor deposition. The direct bandgap emission from strained GeSn is observed in the photoluminescence spectra and is enhanced by Al2O3/SiO2 passivation due to the field effect. The electroluminescence of the direct bandgap emission of strained GeSn is also observed from the Ni/Al2O3/GeSn metal-insulator-semiconductor tunneling diodes. Electroluminescence is a good indicator of GeSn material quality, since defects in GeSn layers degrade the electroluminescence intensity significantly. At the accumulation bias, the holes in the Ni gate electrode tunnel to the strained n-type GeSn layer through the ultrathin Al2O3 and recombine radiatively with electrons. The emission wavelength of photoluminescence and electroluminescence can be tuned by the Sn content.

  9. Interaction of As and Sb in the hyperaccumulator Pteris vittata L.: changes in As and Sb speciation by XANES.

    Science.gov (United States)

    Wan, Xiaoming; Lei, Mei; Chen, Tongbin

    2016-10-01

    Arsenic (As) and antimony (Sb) are chemical analogs that display similar characteristics in the environment. The As hyperaccumulator Pteris vittata L. is a potential As-Sb co-accumulating species. However, when this plant is exposed to different As and Sb speciation, the associated accumulating mechanisms and subsequent assimilation processes of As and Sb remain unclear. A 2-week hydroponic experiment was conducted by exposing P. vittata to single AsIII, AsV, SbIII, and SbV or the co-existence of AsIII and SbIII and AsV and SbV. P. vittata could co-accumulate As and Sb in the pinna (>1000 mg kg(-1)) with high translocation (>1) of As and Sb from the root to the pinna. P. vittata displayed apparent preference to the trivalent speciation of As and Sb than to the pentavalent speciation. Under the single exposure of AsIII or SbIII, the pinna concentration of As and Sb was 84 and 765 % higher than that under the single exposure of AsV or SbV, respectively. Despite the provided As speciation, the main speciation of As in the root was AsV, whereas the main speciation of As in the pinna was AsIII. The Sb in the roots comprised SbV and SbIII when exposed to SbV but was exclusively SbIII when exposed to SbIII. The Sb in the pinna was a mixture of SbV and SbIII regardless of the provided Sb speciation. Compared with the single exposure of As, the co-existence of As and Sb increased the As concentration in the pinna of P. vittata by 50-66 %, accompanied by a significant increase in the AsIII percentage in the root. Compared with the single exposure of Sb, the co-existence of Sb and As also increased the Sb concentration in the pinna by 51-100 %, but no significant change in Sb speciation was found in P. vittata.

  10. Metastable Ge nanocrystalline in SiGe matrix for photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, Yao-Tsung; Su, Chien-Hao [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China); Chang, Jenq-Yang [Department of Optics and Photonics, National Central University, Taoyuan City 320, Taiwan (China); Cheng, Shao-Liang; Lin, Po-Chen [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China); Wu, Albert T., E-mail: atwu@ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China)

    2015-09-15

    Highlights: • Amorphous Si{sub 1−x}Ge{sub x} films were prepared by co-sputtering by using rapid thermal annealing to form nanocrystal films. • Si–Ge alloy does not form total solid solution that is shown in phase diagram. • HRTEM images indicated that Ge atoms segregated and formed Ge clusters that are embedded in the amorphous Si–Ge matrix. • Ge segregation permitted high mobility; the grain size increased and the resistivity decreased with higher Ge content. • The rectifying property became stronger with the Ge fraction in the Si{sub 1−x}Ge{sub x} diodes. Si{sub 1−x}Ge{sub x} diodes are used as photodetectors, which provide a greater output current under illumination. - Abstract: Amorphous Si{sub 1−x}Ge{sub x} films were prepared by co-sputtering on an oxidized Si wafer, followed by rapid thermal annealing to form nanocrystal films. The formation of Ge nanocrystals was not at thermodynamic equilibrium formed in the amorphous Si{sub 1−x}Ge{sub x} matrix. High-resolution transmission electron microscopy was used to characterize the increase in the size of the grains in the Ge nanocrystals as the Ge content increased. The Ge nanocrystals have a greater absorption in the near-infrared region and higher carrier mobility than SiGe crystals, and the variation in their grain sizes can be used to tune the bandgap. This characteristic was exploited herein to fabricate n-Si{sub 1−x}Ge{sub x}/p-Si{sub 1−x}Ge{sub x} p–n diodes on insulating substrates, which were then examined by analyzing their current–voltage characteristics. The rectifying property became stronger as the fraction of Ge in the Si{sub 1−x}Ge{sub x} films increased. The Si{sub 1−x}Ge{sub x} diodes are utilized as photodetectors that have a large output current under illumination. This paper elucidates the correlations between the structural, optical and electrical properties and the p–n junction performance of the film.

  11. Thermodynamic assessment of the La-Sb and the Ho-Sb systems using the associate model

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinsan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Li, Changrong, E-mail: crli@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Cuiping; Du, Zhenmin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, Xushan; Shen, Jianyun [General Research Institute for Nonferrous Metals, Beijing 100088 (China)

    2013-01-10

    Highlights: Black-Right-Pointing-Pointer The liquid phase was described by the associate model. Black-Right-Pointing-Pointer The first-principles method was used to calculate formation enthalpies of compounds. Black-Right-Pointing-Pointer A self-consistent set of thermodynamic parameters was obtained. Black-Right-Pointing-Pointer The experimental and calculated data were well reproduced by the optimized results. - Abstract: The La-Sb and the Ho-Sb systems were thermodynamically assessed by CALPHAD (CALculation of PHAse Diagram) approach based on the available experimental data including thermodynamic properties and phase equilibria. The formation enthalpies (at 0 K) of the compounds of the La-Sb and the Ho-Sb systems were calculated by the first-principles method and used in the present thermodynamic optimization. The liquid phases of both systems were modeled as the associate model, with the constituent species La, Sb and La{sub 3}Sb{sub 2} for the La-Sb liquid and Ho, Sb and HoSb for the Ho-Sb liquid. The excess Gibbs energy was formulated with the Redlich-Kister polynomial. The intermetallics, La{sub 2}Sb, La{sub 3}Sb{sub 2}, LaSb, LaSb{sub 2}, Ho{sub 5}Sb{sub 3}, {alpha}-Ho{sub 4}Sb{sub 3}, {beta}-Ho{sub 4}Sb{sub 3}, {alpha}-HoSb, {beta}-HoSb and HoSb{sub 2}, were treated as stoichiometric compounds. The calculated results showed the good agreement with the experimental data. The inconsistency of the calculated formation enthalpy of the compound HoSb{sub 2} with the reported experimental value was analyzed.

  12. Germanene termination of Ge2Pt crystals on Ge(110)

    NARCIS (Netherlands)

    Bampoulis, Pantelis; Zhang, Lijie; Safaei, A.; van Gastel, Raoul; Poelsema, Bene; Zandvliet, Henricus J.W.

    2014-01-01

    We have investigated the growth of Pt on Ge(1 1 0) using scanning tunneling microscopy and spectroscopy. The deposition of several monolayers of Pt on Ge(1 1 0) followed by annealing at 1100 K results in the formation of 3D metallic Pt-Ge nanocrystals. The outermost layer of these crystals exhibits

  13. Magnetic properties of CeSb and DySb from [mu][sup +]SR

    Energy Technology Data Exchange (ETDEWEB)

    Klauss, H.H. (Inst. fuer Metallphysik und Nukleare Festkoerperphysik, Technische Univ. Braunschweig (Germany)); Melo, M.A.C. de (Inst. fuer Metallphysik und Nukleare Festkoerperphysik, Technische Univ. Braunschweig (Germany)); Litterst, F.J. (Inst. fuer Metallphysik und Nukleare Festkoerperphysik, Technische Univ. Braunschweig (Germany)); Asch, L. (Physik Dept., Technische Univ. Muenchen, Garching (Germany)); Kratzer, A. (Physik Dept., Technische Univ. Muenchen, Garching (Germany)); Henneberger, S. (Physik Dept., Technische Univ. Muenchen, Garching (Germany)); Kalvius, G.M. (Physik Dept., Technische Univ. Muenchen, Garching (Germany)); Mattenberger, K. (Lab. fuer Festkoerperphysik, ETH Zuerich (Switzerland)); Hulliger, F. (Lab. fuer Festkoerperphysik, ETH Zuerich (Switzerland))

    1994-07-01

    ZF [mu]SR experiments on CeSb and DySb reveal fast spin dynamics even in their magnetically ordered states below 16.2 and 9.5 K, respectively. Above these first order transitions both pnictides exhibit strong frequency shifts in TF pointing to some magnetic precursors. The signals below T[sub N] show spontaneous rotating contributions. For CeSb several commensurately modulated antiferromagnetic phases containing paramagnetic sheets are confirmed. For DySb our data favor a CoO type structure in contrast to the MnO structure proposed from neutron diffraction. (orig.)

  14. Tetrahedral 1B4Sb nanoclusters in GaP:(B, Sb)

    Energy Technology Data Exchange (ETDEWEB)

    Elyukhin, V A, E-mail: elyukhin@cinvestav.m [Departamento de Ingenieria Electrica-SEES, CINVESTAV-IPN, Avenida IPN 2508, Col. San Pedro Zacatenco, C. P. 07360, Mexico, D. F. (Mexico)

    2009-05-01

    Self-assembling conditions of 1B4Sb tetrahedral nanoclusters in GaP doped with boron and Sb isoelectronic impurities are represented in the ultradilute and dilute limits of the boron and Sb contents, respectively. The fulfilled estimates demonstrated the preferential complete or almost complete allocation of boron atoms in 1B4Sb nanoclusters at temperatures of 500 {sup 0}C and 900 {sup 0}C, respectively. The significant decrease of the sum of the free energies of the constituent compounds is the main origin of self-assembling. The reduction of the strain energy is the additional cause of this phenomenon.

  15. Sb-induced phase control of InAsSb nanowires grown by molecular beam epitaxy.

    Science.gov (United States)

    Zhuang, Q D; Anyebe, Ezekiel A; Chen, R; Liu, H; Sanchez, Ana M; Rajpalke, Mohana K; Veal, Tim D; Wang, Z M; Huang, Y Z; Sun, H D

    2015-02-11

    For the first time, we report a complete control of crystal structure in InAs(1-x)Sb(x) NWs by tuning the antimony (Sb) composition. This claim is substantiated by high-resolution transmission electron microscopy combined with photoluminescence spectroscopy. The pure InAs nanowires generally show a mixture of wurtzite (WZ) and zinc-blende (ZB) phases, where addition of a small amount of Sb (∼2-4%) led to quasi-pure WZ InAsSb NWs, while further increase of Sb (∼10%) resulted in quasi-pure ZB InAsSb NWs. This phase transition is further evidenced by photoluminescence (PL) studies, where a dominant emission associated with the coexistence of WZ and ZB phases is present in the pure InAs NWs but absent in the PL spectrum of InAs0.96Sb0.04 NWs that instead shows a band-to-band emission. We also demonstrate that the Sb addition significantly reduces the stacking fault density in the NWs. This study provides new insights on the role of Sb addition for effective control of nanowire crystal structure.

  16. CONTACT MATERIALS FOR GaSb AND InSb: A PHASE DIAGRAM APPROACH

    Institute of Scientific and Technical Information of China (English)

    K.W. Richter; H. Ipser

    2002-01-01

    The development of well defined and thermally stable ohmic contacts for Ⅲ- Ⅴ semi-conductors like InSb and GaSb is still a challenging problem in semiconductor devicetechnology. As device processing usually includes the exposure to elevated tempera-tures, interface reactions often occur during metallization and further heat treatment.It is thus important to understand the respective phase equilibria of the involved el-ements. From the thermodynamic point of view, binary and ternary compounds inequilibrium with the respective compound semiconductor would be the best choice forcontact materials as these contacts will be stable even after long exposure to elevatedtemperatures. These possible candidates for contact materials may be directly obtainedfrom the phase diagrams.During the last years we investigated several phase diagrams of transition metals withGaSb and InSb. Experimental results in the systems Ga-Ni-Sb, Ga-Pd-Sb, Ga-Pt-Sb,In-Ni-Sb and In-Pd-Sb are summarized and are discussed in the context of contactchemistry.

  17. Continental hydrothermal sedimentary siliceous rock and genesis of superlarge germanium (Ge) deposit hosted in coal:A study from the Lincang Ge deposit, Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    QI Huawen; HU Ruizhong; SU Wenchao; QI Liang; FENG Jiayi

    2004-01-01

    There are abundant hydrothermal sedimentary structures and plant fragment fossils in the siliceous rocks from the Lincang Ge deposit. The major element compositions of these siliceous rocks are characterized by high content SiO2, low TiO2 and Al2O3 concentrations, and low Al/(Al+Fe+Mn) ratios (0.010 on average). The siliceous rocks are distinctly enriched in Ge,Sb, As, W, and secondly enriched in Cs, U, Mo and TI. Their total REE content are generally less than 1μg/g, LREE relatively concentrated, and the values of Eu anomaly and Ce anomaly vary from 0.452 to 5.141 and 0.997 to 1.174, respectively. Their NAS-normalized REE patterns are plain or left-inclined. The Oxygen isotope compositions of these siliceous rocks are similar to those of the hydrothermal siliceous sinter. The above characteristics, as well as the geological setting of the deposit, indicate these siliceous rocks formed in continental hydrothermal environment. As the interlayer or cliff of the Ge-rich coal seams, siliceous rocks tightly contacted with ore-body, and the contents of Ge in siliceous rocks vary from 5.6 to 360 μg/g (78 μg/g on aver-age). The Ge content increased in coal which close to the siliceous rocks. With the increase of Ge content, the typical trace element ratios (i.e., Ge/Ga, Nb/Ta and U/Th) and REE patterns of Ge-rich coal are more close to those of the siliceous rocks. The Ge concentrated in coal seams of the Lincang Ge deposit might be transported by the hydrothermal water, which demonstrated by the siliceous rocks, during the coal-forming processes.

  18. Continental hydrothermal sedimentary siliceous rock and genesis of superlarge germanium (Ge) deposit hosted in coal: A study from the Lincang Ge deposit, Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    QI; Huawen; HU; Ruizhong; SU; Wenchao; QI; Liang; FENG; Jia

    2004-01-01

    There are abundant hydrothermal sedimentary structures and plant fragment fossils in the siliceous rocks from the Lincang Ge deposit. The major element compositions of these siliceous rocks are characterized by high content SiO2, low TiO2 and Al2O3 concentrations, and low Al/(Al+Fe+Mn) ratios (0.010 on average). The siliceous rocks are distinctly enriched in Ge,Sb, As, W, and secondly enriched in Cs, U, Mo and TI. Their total REE content are generally less than 1μg/g, LREE relatively concentrated, and the values of Eu anomaly and Ce anomaly vary from 0.452 to 5.141 and 0.997 to 1.174, respectively. Their NAS-normalized REE patterns are plain or left-inclined. The Oxygen isotope compositions of these siliceous rocks are similar to those of the hydrothermal siliceous sinter. The above characteristics, as well as the geological setting of the deposit, indicate these siliceous rocks formed in continental hydrothermal environment. As the interlayer or cliff of the Ge-rich coal seams, siliceous rocks tightly contacted with ore-body, and the contents of Ge in siliceous rocks vary from 5.6 to 360 μg/g (78 μg/g on aver-age). The Ge content increased in coal which close to the siliceous rocks. With the increase of Ge content, the typical trace element ratios (i.e., Ge/Ga, Nb/Ta and U/Th) and REE patterns of Ge-rich coal are more close to those of the siliceous rocks. The Ge concentrated in coal seams of the Lincang Ge deposit might be transported by the hydrothermal water, which demonstrated by the siliceous rocks, during the coal-forming processes.

  19. Reassessment of the carrier concentration in GeTe-based thermoelectric materials by ^125Te NMR

    Science.gov (United States)

    Levin, E. M.; Acton, J. D.; Schmidt-Rohr, K.

    2012-02-01

    Ge1-xAgx/2Sbx/2Te p-type thermoelectric materials (``TAGS-n'') were studied extensively in the 1970s and then again recently. They exhibit an unusual combination of large thermopower, S, and high hole concentration, p, reported based on the Hall effect data, which has not been explained. To solve this puzzle, we have synthesized GeTe, GeTe:Bi, and TAGS-n with n = 97, 94, 90, and 85 and studied XRD, thermopower, electrical resistivity, thermal conductivity, and ^125Te NMR. Most importantly, we have determined the carrier concentrations using ^125Te NMR spin-lattice relaxation and Knight shift. In GeTe and GeTe:Bi, we found that carrier concentrations generally agree with the values reported from Hall effect. In TAGS-n, they are much lower but agree better with the values expected from S vs. p for GeTe-based materials, solving the puzzle partially. The NMR vs. Hall effect discrepancy in TAGS-n can be due to the presence not only of holes but also electrons generated by Sb atoms, which results in artificially high hole concentration from Hall effect. Even though the true hole concentration is lower than reported, the thermopower of TAGS-n is still significantly larger than that of GeTe and GeTe:Bi at similar carrier concentration. This can be explained by energy filtering enhanced by potential barriers formed due to Ag-Sb pairs in the TAGS-n lattice.

  20. Interstitial-related defect reactions in electron-irradiated oxygen-rich Ge crystals: A DLTS study

    Energy Technology Data Exchange (ETDEWEB)

    Markevich, V.P., E-mail: V.Markevich@manchester.ac.u [School of Electrical and Electronic Engineering, University of Manchester, Sackville Str. Building, Manchester, M60 1QD (United Kingdom); Peaker, A.R. [School of Electrical and Electronic Engineering, University of Manchester, Sackville Str. Building, Manchester, M60 1QD (United Kingdom); Lastovskii, S.B.; Murin, L.I. [Scientific-Practical Materials Research Center of NAS of Belarus, Minsk 220072 (Belarus); Litvinov, V.V. [Belarusian State University, Minsk 220050 (Belarus); Emtsev, V.V. [Ioffe Physico-Technical Institute, St. Petersburg 194021 (Russian Federation); Dobaczewski, L. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)

    2009-12-15

    Electrically active defects induced in oxygen-rich Ge:Sb crystals by irradiation with MeV electrons at 80 or 300 K have been studied by means of capacitance transient techniques. Transformations of the defects upon post-irradiation isochronal anneals have also been investigated. It is argued that a radiation-induced electron trap with an energy level at about 110 meV below the conduction band edge (E{sub 110}) can be associated with electron emission from an energy level of the Ge self-interstitial (I{sub Ge}). The E{sub 110} trap is eliminated in the temperature range 150-200 K upon 15 min isochronal annealing. No other traps in the upper half of the gap emerge simultaneously with the disappearance of the E{sub 110} trap. It is argued that Ge self-interstitials become mobile at temperatures higher than 150 K and in oxygen-rich Ge interact with interstitial oxygen atoms (O{sub i}). The resulting I{sub Ge}O{sub i} complexes do not have energy levels in the upper half of the Ge gap. Diffusion and interaction of the I{sub Ge}O{sub i} defects with interstitial oxygen atoms at T>50 deg. C result in the formation of I{sub Ge}O{sub 2i} complexes. In the most stable configuration the I{sub Ge}O{sub 2i} complex has orthorhombic (C{sub 2v}) symmetry.

  1. Sb2Se3 under pressure

    Science.gov (United States)

    Efthimiopoulos, Ilias; Zhang, Jiaming; Kucway, Melvin; Park, Changyong; Ewing, Rodney C.; Wang, Yuejian

    2013-01-01

    Selected members of the A2B3 (A = Sb, Bi; B = Se, Te) family are topological insulators. The Sb2Se3 compound does not exhibit any topological properties at ambient conditions; a recent high-pressure study, however, indicated that pressure transforms Sb2Se3 from a band insulator into a topological insulator above ~2 GPa; in addition, three structural transitions were proposed to occur up to 25 GPa. Partly motivated by these results, we have performed x-ray diffraction and Raman spectroscopy investigations on Sb2Se3 under pressure up to 65 GPa. We have identified only one reversible structural transition: the initial Pnma structure transforms into a disordered cubic bcc alloy above 51 GPa. On the other hand, our high-pressure Raman study did not reproduce the previous results; we attribute the discrepancies to the effects of the different pressure transmitting media used in the high-pressure experiments. We discuss the structural behavior of Sb2Se3 within the A2B3 (A = Sb, Bi; B = Se, Te) series. PMID:24045363

  2. In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

    Science.gov (United States)

    Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

    2012-01-01

    The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

  3. InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors. Growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Lien

    2011-04-13

    This dissertation describes investigations of the growth by molecular beam epitaxy and the characterization of the semiconductor InSb as well as the diluted magnetic semiconductor (DMS) In{sub 1-x}Mn{sub x}Sb. The InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4 toward (110) substrate up to a thickness of about 2 {mu}m, in spite of a large lattice mismatch between the epi-layer and substrate (14.6% between InSb and GaAs, and 19.3% between InSb and Si). After optimizing the growth conditions, the best InSb films grown directly on GaAs without any special technique results in a high crystal quality, low noise, and an electron mobility of 41100 cm{sup 2}/V s Vs with associated electron concentration of 2.9.10{sup 6} cm{sup -3} at 300 K. Such structures could be used, for example, for infrared detector structures. The growth of InSb on Si, however, is a challenge. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used, which helps to reduce the lattice mismatch as well as the formation of defects, and hence to improve the crystal quality. An electron mobility of 24000 cm{sup 2}/V s measured at 300 K, with an associated carrier concentration of 2.6.10{sup 1}6 cm{sup -3} is found for the best sample that was grown at 340 C with a 0.06 {mu}m-thick GaSb/AlSb superlattice buffer layer. The smaller value of electron mobility (compared to the best GaAsbased sample) is related to a higher density of microtwins and stacking faults as well as threading dislocations in the near-interface region as shown by transmission electron microscopy. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The samples grown on Si exhibit the lowest Hooge factor at 300 K, lower than the samples grown on GaAs. Taking the optimized growth conditions of InSb/GaAs, the diluted magnetic semiconductor In{sub 1-x}Mn{sub x}Sb/GaAs (001) is prepared by adding a few percent of Mn into the

  4. Ler o mundo: um olhar através da simiótica social

    OpenAIRE

    Maria Alice Andrade de Souza Descardeci

    2002-01-01

    O presente artigo questiona os pressupostos com os quais a escola brasileira trabalha o conceito de leitura, que impõe ao aluno a modalidade escrita como sendo a única, ou mais relevante, forma de representação para composição de mensagens impressas. A leitura do mundo, na concepção da escola atual, faz-se através da leitura do código escrito. Tal questionamento é feito através da teoria da semiótica social (Kress e van Leeuwen, 1996). De acordo com essa teoria, textos são construtos multi-mo...

  5. Synthesis of Epitaxial Films Based on Ge-Si-Sn Materials with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn Heterojunctions

    Science.gov (United States)

    Timofeev, V. A.; Kokhanenko, A. P.; Nikiforov, A. I.; Mashanov, V. I.; Tuktamyshev, A. R.; Loshkarev, I. D.

    2015-11-01

    Results of investigations into the synthesis of heterostructures based on Ge-Si-Sn materials by the method of low-temperature molecular beam epitaxy are presented. The formation of epitaxial films during structure growth has been controlled by the reflection high-energy electron diffraction method. Films with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions are grown with Sn content changing from 2 to 10 % at temperatures in the interval 150-350°C. The stressed state, the composition, and the lattice parameter are studied by the x-ray diffraction method using Omega-scan curves and reciprocal space maps. A tensile strain in the Ge film during Ge/Ge0.9Sn0.1/Si structure growth has reached 0.86%.

  6. Sb@Ni12@Sb20(-/+) and Sb@Pd12@Sb20(n) Cluster Anions, Where n = +1, -1, -3, -4: Multi-Oxidation-State Clusters of Interpenetrating Platonic Solids.

    Science.gov (United States)

    Wang, Yi; Moses-DeBusk, Melanie; Stevens, Lauren; Hu, Junkai; Zavalij, Peter; Bowen, Kit; Dunlap, Brett I; Glaser, Evan R; Eichhorn, Bryan

    2017-01-18

    K5Sb4 and K3Sb7 Zintl ion precursors react with Pd(PPh3)4 in ethylenediamine/toluene/PBu4(+) solutions to give crystals of Sb@Pd12@Sb20(n-)/PBu4(+) salts, where n = 3, 4. The clusters are structurally identical in the two charge states, with nearly perfect Ih point symmetry, and can be viewed as an Sb@Pd12 icosahedron centered inside of an Sb20 dodecahedron. The metric parameters suggest very weak Sb-Sb and Pd-Pd interactions with strong radial Sb-Pd bonds between the Sb20 and Pd12 shells. All-electron DFT analysis shows the 3- ion to be diamagnetic with Ih symmetry and a 1.33 eV HOMO-LUMO gap, whereas the 4- ion undergoes a Jahn-Teller distortion to an S = 1/2 D3d structure with a small 0.1 eV gap. The distortion is predicted to be small and is not discernible by crystallography. Laser desorption-ionization time-of-flight mass spectrometry (LDI-TOF MS) studies of the crystalline samples show intense parent Sb@Pd12@Sb20(-) ions (negative ion mode) and Sb@Pd12@Sb20(+) (positive ion mode) along with series of Sb@Pd12-y@Sb20-x(-/+) ions. Ni(cyclooctadiene)2 reacts with K3Sb7 in en/tol/Bu4PBr solvent mixtures to give black precipitates of Sb@Ni12@Sb20(n-) salts that give similar Sb@Ni12@Sb20(-/+) parent ions and Sb@Ni12-y@Sb20-x(-/+) degradation series in the respective LDI-TOF MS studies. The solid-state and gas-phase studies of the icosahedral Sb@M12@Sb20(n-/n+) ions show that the clusters can exist in the -4, -3, -1, +1 (M = Pd) and +1, -1 (M = Ni) oxidation states. These multiple-charge-state clusters are reminiscent of redox-active fullerenes (e.g., C60(n), where n = +1, 0, -1, -2, -3, -4, -5, -6).

  7. Sb complexes and Zn interstitials in Sb-implanted ZnO epitaxial films

    Institute of Scientific and Technical Information of China (English)

    Liu Yao-Ping; Ying Min-Ju; Mei Zeng-Xia; Li Jun-Qianng; Du Xiao-Long; A.Yu.Kuznetsovc

    2011-01-01

    In the present work, post-annealing is adopted to investigate the formation and the correlation of Sb complexes and Zn interstitials in Sb-ion implanted ZnO films, by using Raman scattering technique and electrical characterizations.The damage of Zn sublattice, produced by ion bombardment process is discerned from the unrecovered E2 (L) peak in annealed high Sb+ dose implanted samples. It is suggested that the Zn sublattice may be strongly affected by the introduction of Sb dopant because of the formation of SbZn-2VZn complex acceptor. The appearance of a new peak at 510 cm-1 in the annealed high dose Sb+ implanted samples is speculated to result from (Zn interstitials-O interstitials)Zni-Oi complex, which is in a good accordance with the electrical measurement. The p-type ZnO is difficult to obtain from the Sb+ implantation, however, which can be realized by in-situ Sb doping with proper growth conditions instead.

  8. Removal of antimony (Sb(V)) from Sb mine drainage: biological sulfate reduction and sulfide oxidation-precipitation.

    Science.gov (United States)

    Wang, Huawei; Chen, Fulong; Mu, Shuyong; Zhang, Daoyong; Pan, Xiangliang; Lee, Duu-Jong; Chang, Jo-Shu

    2013-10-01

    Antimony (Sb(V)) in Sb mine drainage has adverse effects on the receiving water environments. This study for the first time demonstrated the feasibility of using sulfate-reducing bacteria (SRB) to convert sulfate ions in SMD into sulfides that reduce Sb(V) to Sb(III) and to form complex with Sb(III) as precipitate. The principal compound in the precipitate was stibnite (Sb2S3) at pH 7 and pH 9. The Sb(V) removal mechanism is sulfate-reduction and sulfide oxidization-precipitation, different from the conventional SRB-precipitation processes for heavy metals. The Sb(V)/sulfate ratio is noted an essential parameter affecting the Sb removal efficiency from SMD.

  9. DWPF simulant CPC studies for SB8

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D. C.; Zamecnik, J. R.

    2013-06-25

    The Savannah River National Laboratory (SRNL) accepted a technical task request (TTR) from Waste Solidification Engineering to perform simulant tests to support the qualification of Sludge Batch 8 (SB8) and to develop the flowsheet for SB8 in the Defense Waste Processing Facility (DWPF). These efforts pertained to the DWPF Chemical Process Cell (CPC). Separate studies were conducted for frit development and glass properties (including REDOX). The SRNL CPC effort had two primary phases divided by the decision to drop Tank 12 from the SB8 constituents. This report focuses on the second phase with SB8 compositions that do not contain the Tank 12 piece. A separate report will document the initial phase of SB8 testing that included Tank 12. The second phase of SB8 studies consisted of two sets of CPC studies. The first study involved CPC testing of an SB8 simulant for Tank 51 to support the CPC demonstration of the washed Tank 51 qualification sample in the SRNL Shielded Cells facility. SB8-Tank 51 was a high iron-low aluminum waste with fairly high mercury and moderate noble metal concentrations. Tank 51 was ultimately washed to about 1.5 M sodium which is the highest wash endpoint since SB3-Tank 51. This study included three simulations of the DWPF Sludge Receipt and Adjustment Tank (SRAT) cycle and Slurry Mix Evaporator (SME) cycle with the sludge-only flowsheet at nominal DWPF processing conditions and three different acid stoichiometries. These runs produced a set of recommendations that were used to guide the successful SRNL qualification SRAT/SME demonstration with actual Tank 51 washed waste. The second study involved five SRAT/SME runs with SB8-Tank 40 simulant. Four of the runs were designed to define the acid requirements for sludge-only processing in DWPF with respect to nitrite destruction and hydrogen generation. The fifth run was an intermediate acid stoichiometry demonstration of the coupled flowsheet for SB8. These runs produced a set of processing

  10. Effect of n-type doping level on direct band gap electroluminescence intensity for asymmetric metal/Ge/metal diodes

    Science.gov (United States)

    Maekura, T.; Tanaka, K.; Motoyama, C.; Yoneda, R.; Yamamoto, K.; Nakashima, H.; Wang, D.

    2017-10-01

    The direct band gap electroluminescence (EL) intensity was investigated for asymmetric metal/Ge/metal diodes fabricated on n-type Ge with doping levels in the range of 4.0 × 1013-3.1 × 1018 cm-3. Up to a doping level of 1016 cm-3 order, commercially available (100) n-Ge substrates were used. To obtain a doping level higher than 1017 cm-3 order, which is commercially unavailable, n+-Ge/p-Ge structures were fabricated by Sb doping on p-type (100) Ge substrates with an in-diffusion at 600 °C followed by a push-diffusion at 700 °C-850 °C. The EL intensity was increased with increasing doping level up to 1.0 × 1018 cm-3. After that, it was decreased with a further increase in n-type doping level. This EL intensity decrease is explained by the decreased number of holes in the active region. One reason is the difficulty in hole injection through the PtGe/n-Ge contact due to the occurring of tunneling electron current. Another reason is the loss of holes caused by both the small thickness of n+-Ge layer and the existence of n+p junction.

  11. Characteristics of Sn segregation in Ge/GeSn heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Chang, C.; Chen, T. P.; Cheng, H. H., E-mail: hhcheng@ntu.edu.tw [Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Shi, Z. W.; Chen, H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-10-13

    We report an investigation of Sn segregation in Ge/GeSn heterostructures occurred during the growth by molecular beam epitaxy. The measured Sn profile in the Ge layer shows that: (a) the Sn concentration decreases rapidly near the Ge/GeSn interface, and (b) when moving away from the interface, the Sn concentration reduced with a much slower rate. The 1/e decay lengths of the present system are much longer than those of the conventional group IV system of Ge segregation in the Si overlayer because of the smaller kinetic potential as modeled by a self-limited two-state exchange scheme. The demonstration of the Sn segregation shows the material characteristics of the heterostructure, which are needed for the investigation of its optical properties.

  12. Phonons in Ge/Si superlattices with Ge quantum dots

    CERN Document Server

    Milekhin, A G; Pchelyakov, O P; Schulze, S; Zahn, D R T

    2001-01-01

    Ge/Si superlattices with Ge quantum dots obtained by means of molecular-beam epitaxy were investigated by means of light Raman scattering under resonance conditions. These structures are shown to have oscillation properties of both two-dimensional and zero-dimensional objects. Within spectrum low-frequency range one observes twisted acoustic phonons (up to 15 order) typical for planar superlattices. Lines of acoustic phonons are overlapped with a wide band of continuous emission. Analysis of frequencies of Ge and Ge-Si optical phonons shows that Ge quantum dots are pseudoamorphous ones and mixing of Ge and Si atoms is a negligible one. One detected low-frequency shift of longitudinal optical phonons at laser excitation energy increase (2.54-2.71 eV)

  13. Sb(V) reactivity with human blood components: redox effects.

    Science.gov (United States)

    López, Silvana; Aguilar, Luis; Mercado, Luis; Bravo, Manuel; Quiroz, Waldo

    2015-01-01

    We assessed the reactivity of Sb(V) in human blood. Sb(V) reactivity was determined using an HPLC-HG-AFS hyphenated system. Sb(V) was partially reduced to Sb(III) in blood incubation experiments; however, Sb(III) was a highly unstable species. The addition of 0.1 mol L(-1) EDTA prevented Sb(III) oxidation, thus enabling the detection of the reduction of Sb(V) to Sb(III). The transformation of Sb(V) to Sb(III) in human whole blood was assessed because the reduction of Sb(V) in human blood may likely generate redox side effects. Our results indicate that glutathione was the reducing agent in this reaction and that Sb(V) significantly decreased the GSH/GSSG ratio from 0.32 ± 0.09 to 0.07 ± 0.03. Moreover, the presence of 200 ng mL(-1) of Sb(V) increased the activity of superoxide dismutase from 4.4 ± 0.1 to 7.0 ± 0.4 U mL(-1) and decreased the activity of glutathione peroxidase from 62 ± 1 to 34 ± 2 nmol min(-1) mL(-1).

  14. Sb(V reactivity with human blood components: redox effects.

    Directory of Open Access Journals (Sweden)

    Silvana López

    Full Text Available We assessed the reactivity of Sb(V in human blood. Sb(V reactivity was determined using an HPLC-HG-AFS hyphenated system. Sb(V was partially reduced to Sb(III in blood incubation experiments; however, Sb(III was a highly unstable species. The addition of 0.1 mol L(-1 EDTA prevented Sb(III oxidation, thus enabling the detection of the reduction of Sb(V to Sb(III. The transformation of Sb(V to Sb(III in human whole blood was assessed because the reduction of Sb(V in human blood may likely generate redox side effects. Our results indicate that glutathione was the reducing agent in this reaction and that Sb(V significantly decreased the GSH/GSSG ratio from 0.32 ± 0.09 to 0.07 ± 0.03. Moreover, the presence of 200 ng mL(-1 of Sb(V increased the activity of superoxide dismutase from 4.4 ± 0.1 to 7.0 ± 0.4 U mL(-1 and decreased the activity of glutathione peroxidase from 62 ± 1 to 34 ± 2 nmol min(-1 mL(-1.

  15. Reduction in thermal conductivity of BiSbTe lump

    Science.gov (United States)

    Ahmad, Kaleem; Wan, C.; Al-Eshaikh, M. A.; Kadachi, A. N.

    2017-03-01

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 µm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 µm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 µm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 µm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 µm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes.

  16. Reduction in thermal conductivity of BiSbTe lump

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Kaleem [King Saud University, Sustainable Energy Technologies Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia); Wan, C. [Tsinghua University, State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Beijing (China); Al-Eshaikh, M.A.; Kadachi, A.N. [King Saud University, Research Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia)

    2017-03-15

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 μm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 μm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 μm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 μm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 μm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes. (orig.)

  17. Peculiarities of thermoelectric half-Heusler phase formation in Gd-Ni-Sb and Lu-Ni-Sb ternary systems

    Energy Technology Data Exchange (ETDEWEB)

    Romaka, V.V., E-mail: romakav@lp.edu.ua [Department of Applied Material Science and Materials Engineering, Lviv Polytechnic National University, Ustyyanovycha Str. 5, 79013 Lviv (Ukraine); Romaka, L.; Horyn, A. [Inorganic Chemistry Department, Ivan Franko Lviv National University, Kyryla and Mefodiya str. 6, 79005 Lviv (Ukraine); Rogl, P. [Institute of Materials Chemistry and Research, University of Vienna, Währingerstrasse 42, A-1090 Wien (Austria); Stadnyk, Yu; Melnychenko, N. [Inorganic Chemistry Department, Ivan Franko Lviv National University, Kyryla and Mefodiya str. 6, 79005 Lviv (Ukraine); Orlovskyy, M.; Krayovskyy, V. [Department of Applied Material Science and Materials Engineering, Lviv Polytechnic National University, Ustyyanovycha Str. 5, 79013 Lviv (Ukraine)

    2016-07-15

    The phase equilibria in the Gd–Ni–Sb and Lu-Ni-Sb ternary systems were studied at 873 K by X-ray and metallographic analyses in the whole concentration range. The interaction of the elements in the Gd–Ni–Sb system results the formation of five ternary compounds at investigated temperature: Gd{sub 5}Ni{sub 2}Sb (Mo{sub 5}SiB{sub 2}-type), Gd{sub 5}NiSb{sub 2} (Yb{sub 5}Sb{sub 3}-type), GdNiSb (MgAgAs-type), Gd{sub 3}Ni{sub 6}Sb{sub 5} (Y{sub 3}Ni{sub 6}Sb{sub 5}-type), and GdNi{sub 0.72}Sb{sub 2} (HfCuSi{sub 2}-type). At investigated temperature the Lu-Ni-Sb system is characterized by formation of the LuNiSb (MgAgAs-type), Lu{sub 5}Ni{sub 2}Sb (Mo{sub 5}SiB{sub 2}-type), and Lu{sub 5}Ni{sub 0.56}Sb{sub 2.44} (Yb{sub 5}Sb{sub 3}-type) compounds. The disordering in the crystal structure of half-Heusler GdNiSb and LuNiSb was revealed by EPMA and studied by means of Rietveld refinement and DFT modeling. The performed electronic structure calculations are in good agreement with electrical transport property studies. - Graphical abstract: Crystal structure model and electron localization function of Lu{sub 5}Ni{sub 2}Sb. Display Omitted - Highlights: • Gd-Ni-Sb and Lu-Ni-Sb phase diagrams were constructed at 873 K. • GdNiSb and LuNiSb are characterized by disordered crystal structure. • Crystal structure optimization with DFT calculations confirmed crystal structure disorder in GdNiSb and LuNiSb.

  18. Adsorption of Sb(III) and Sb(V) on Freshly Prepared Ferric Hydroxide (FeOxHy).

    Science.gov (United States)

    He, Zan; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2015-02-01

    This study prepared fresh ferric hydroxide (in-situ FeOxHy) by the enhanced hydrolysis of Fe(3+) ions, and investigates its adsorptive behaviors toward Sb(III) and Sb(V) through laboratory and pilot-scale studies. A contact time of 120-min was enough to achieve adsorption equilibrium for Sb(III) and Sb(V) on the in-situ FeOxHy, and the Elovich model was best to describe the adsorption kinetics of Sb(III) and Sb(V). The Freundlich model was better than Langmuir model to describe the adsorption of Sb(III) and Sb(V) on the in-situ FeOxHy, and the maximum adsorption capacity of Sb(III) and Sb(V) was determined to be 12.77 and 10.21 mmol/g the in-situ FeOxHy as Fe, respectively. Adsorption of Sb(V) decreased whereas that of Sb(III) increased with elevated pH over pH 3-10, owing to the different electrical properties of Sb(III) and Sb(V). Adsorption of Sb(III) and Sb(V) was slightly affected by ionic strength, and thus indicated the formation of inner sphere complexes between Sb and the adsorbent. Sulfate and carbonate showed little effect on the adsorption of Sb(III) and Sb(V). Phosphate significantly inhibited the adsorption of Sb(V), whereas slightly effected that of Sb(III) due to its similar chemical structure to Sb(V). Pilot-scale continuous experiment indicated the feasibility of using in-situ FeOxHy to remove Sb(V), and equilibrium adsorption capacity at the equilibrium Sb(V) concentration of 10 μg/L was determined to be 0.11, 0.07, 0.07, 0.11, and 0.12 mg/g the in-situ FeOxHy as Fe at equilibrium pH of 7.5-7.7, 6.9-7.0, 6.3-6.6, 5.9-6.4, and 5.2-5.9, respectively.

  19. Reactive ion etching of Si(x)Sb2Te in CF4/Ar plasma for nonvolatile phase-change memory device.

    Science.gov (United States)

    Gu, Yifeng; Song, Sannian; Song, Zhitang; Cheng, Yan; Liu, Xuyan; Du, Xiaofeng; Liu, Bo; Feng, Songlin

    2013-02-01

    Si(x)Sb2Te material system is novel for phase-change random access memory applications. Its properties are more outstanding than the widely used material Ge2Sb2Te5. Etching process is one of the critical steps in the device fabrication. The etching characteristics of phase-change material Si(x)Sb2Te were studied with CF4/Ar gas mixture by a reactive ion etching system. The changes of etching rate, etching profile and surface root-mean-square roughness resulted from variation of the gas-mixing ratio were investigated under constant pressure (50 mTorr) and applying power (200 W). Si0.34Sb2Te is with the highest phase-change speed and the lowest power consumption in the PCRAM memory among these compositions, which means it is the most promising candidate for the PCRAM applications. So the most optimized CF4/Ar gas ratio for Si0.34Sb2Te was studied, the value is 25/25. The etching rate is 155 nm/min, and the selectivity of Si0.34Sb2Te to SiO2 is as high as 3.4 times. Furthermore, the smooth surface was achieved with this optimized gas ratio.

  20. Phase change properties of Ti-Sb-Te thin films deposited by thermal atomic layer deposition

    Science.gov (United States)

    Song, Sannian; Shen, Lanlan; Song, Zhitang; Yao, Dongning; Guo, Tianqi; Li, Le; Liu, Bo; Wu, Liangcai; Cheng, Yan; Ding, Yuqiang; Feng, Songlin

    2016-10-01

    Phase change random access memory (PCM) appears to be the strongest candidate for next-generation high density nonvolatile memory. The fabrication of ultrahigh density PCM depends heavily on the thin film growth technique for the phase changing chalcogenide material. In this study, TiSb2Te4 (TST) thin films were deposited by thermal atomic layer deposition (ALD) method using TiCl4, SbCl3, (Et3Si)2Te as precursors. The threshold voltage for the cell based on thermal ALD-deposited TST is about 2.0 V, which is much lower than that (3.5 V) of the device based on PVD-deposited Ge2Sb2Te5 (GST) with the identical cell architecture. Tests of TST-based PCM cells have demonstrated a fast switching rate of 100 ns. Furthermore, because of the lower melting point and thermal conductivities of TST materials, TST-based PCM cells exhibit 19% reduction of pulse voltages for Reset operation compared with GST-based PCM cells. These results show that thermal ALD is an attractive method for the preparation of phase change materials.

  1. XPS Studies of Yb14MnSb11 and Yb14ZnSb11

    Energy Technology Data Exchange (ETDEWEB)

    Holm, A P; Ozawa, T C; Kauzlarich, S M; Morton, S A; Waddill, G D; Pickett, W E; Tobin, J G

    2003-10-02

    Measurements of core and valence electronic states of single crystals of the rare earth transition metal Zintl phases Yb{sub 14}MnSb{sub 11} and Yb{sub 14}ZnSb{sub 11} were performed using the X-ray photoelectron spectroscopy station of Beamline 7 at the Advanced Light Source. Sample surfaces of Yb{sub 14}MnSb{sub 11} and Yb{sub 14}ZnSb{sub 11} were measured as received, after Ar{sup +} ion bombardment, and after cleaving in situ. Detailed analysis of the clean Mn and Zn analog sample surfaces reveal a significant contribution of both Yb{sup 3+} and Yb{sup 2+} 4f states in the valence band region for the Zn analog and no contribution of Yb{sup 3+} states to the valence band for the Mn analog. This result is predicted for the Zn analog by Zintl counting rules, and single crystal X-ray diffraction studies presented here also support the mixed valency of Yb for Yb{sub 14}ZnSb{sub 11}. Further detailed analysis of the core and valence band structure of both Yb{sub 14}MnSb{sub 11} and Yb{sub 14}ZnSb{sub 11} will be presented.

  2. Viscosity of liquid Ag-In-Sb-Te: Evidence of a fragile-to-strong crossover

    Science.gov (United States)

    Orava, J.; Weber, H.; Kaban, I.; Greer, A. L.

    2016-05-01

    The temperature-dependent viscosity η(T) is measured for the equilibrium liquid of the chalcogenide Ag-In-Sb-Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829-1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η(T) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η(T) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge-Sb-Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te85Ge15. The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η(T) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance.

  3. Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining.

    Science.gov (United States)

    Cidu, Rosa; Biddau, Riccardo; Dore, Elisabetta

    2015-01-07

    Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1-20 μg L(-1) working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1-100μgL(-1) working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100-10,000 μg L(-1) working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO3. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO3, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L(-1)), with Sb(III) Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).

  4. Thermodynamic assessment of the Ni-Sb binary system

    Institute of Scientific and Technical Information of China (English)

    CAO Zhanmin; TAKADU Yoshikazu; OHNUMA Ikuo; KAINUMA Ryosuke; ZHU Hongmin; ISHIDA Kiyohito

    2008-01-01

    The Ni-Sb binary alloy system was thermodynamically assessed using CALPHAD approach in this article.Excess Gibbs energies of solution phases,liquid and fcc phases,were formulated using the Redlich-Kister expression.The intermediate phases were modeled by the sublattice model with (Ni,Va)0.5(Ni,Sb)0.25(Ni)0.25 for Ni3Sb_HT phase and (Ni,Va)0.3333(Sb)0.3333(Ni,Va)0.3333 for NiSb phase.The other phases including Ni3Sb,Ni7Sb3,and NiSb2 were treated as stoichiometric compound owing to their narrow composition ranges.Based on the reported thermodynamic properties and phase diagram data,the thermodynamic parameters of these phases were optimized,and the obtained values can reproduce the available experimental data well.

  5. Electrical performance of InAs/AlSb/GaSb superlattice photodetectors

    Science.gov (United States)

    Tansel, T.; Hostut, M.; Elagoz, S.; Kilic, A.; Ergun, Y.; Aydinli, A.

    2016-03-01

    Temperature dependence of dark current measurements is an efficient way to verify the quality of an infrared detector. Low dark current density values are needed for high performance detector applications. Identification of dominant current mechanisms in each operating temperature can be used to extract minority carrier lifetimes which are highly important for understanding carrier transport and improving the detector performance. InAs/AlSb/GaSb based T2SL N-structures with AlSb unipolar barriers are designed for low dark current with high resistance and detectivity. Here we present electrical and optical performance of such N-structure photodetectors.

  6. A global Ge isotope budget

    Science.gov (United States)

    Baronas, J. Jotautas; Hammond, Douglas E.; McManus, James; Wheat, C. Geoffrey; Siebert, Christopher

    2017-04-01

    We present measurements of Ge isotope composition and ancillary data for samples of river water, low- and high-temperature hydrothermal fluids, and seawater. The dissolved δ74Ge composition of analyzed rivers ranges from 2.0 to 5.6‰, which is significantly heavier than previously determined values for silicate rocks (δ74Ge = 0.4-0.7‰, Escoube et al., Geostand. Geoanal. Res., 36(2), 2012) from which dissolved Ge is primarily derived. An observed negative correlation between riverine Ge/Si and δ74Ge signatures suggests that the primary δ74Ge fractionation mechanism during rock weathering is the preferential incorporation of light isotopes into secondary weathering products. High temperature (>150 °C) hydrothermal fluids analyzed in this study have δ74Ge of 0.7-1.6‰, most likely fractionated during fluid equilibration with quartz in the reaction zone. Low temperature (25-63 °C) hydrothermal fluids are heavier (δ74Ge between 2.9‰ and 4.1‰) and most likely fractionated during Ge precipitation with hydrothermal clays. Seawater from the open ocean has a δ74Gesw value of 3.2 ± 0.4‰, and is indistinguishable among the different ocean basins at the current level of precision. This value should be regulated over time by the isotopic balance of Ge sources and sinks, and a new compilation of these fluxes is presented, along with their estimated isotopic compositions. Assuming steady-state, non-opal Ge sequestration during sediment authigenesis likely involves isotopic fractionation Δ74Gesolid-solution that is -0.6 ± 1.8‰.

  7. Donors in Ge as qubits —Establishing physical attributes

    Science.gov (United States)

    Baena, A.; Saraiva, A. L.; Menezes, Marcos G.; Koiller, Belita

    2016-10-01

    Quantum electronic devices at the single-impurity level demand the understanding of the physical attributes of dopants with an unprecedented accuracy. Germanium-based technologies have been developed recently, creating the necessity to adapt the latest theoretical tools to the unique electronic structure of this material. We investigate basic properties of donors in Ge which are not known experimentally, but are indispensable for qubit implementations. Our approach provides a description of the wave function at multiscale, associating microscopic information from density functional theory and envelope functions from state-of-the-art multivalley effective mass calculations, including a central-cell correction designed to reproduce the energetics of all group-V donor species (P, As, Sb and Bi). With this formalism, we predict the binding energies of negatively ionized donors (D- state). Furthermore, we investigate the signatures of buried donors to be expected from scanning tunneling microscopy (STM). The naive assumption that attributes of donor electrons in other semiconductors may be extrapolated to Ge is shown to fail, similarly to earlier attempts to recreate in Si qubits designed for GaAs. Our results suggest that the mature techniques available for qubit realizations may be adapted to germanium to some extent, but the peculiarities of the Ge band structure will demand new ideas for fabrication and control.

  8. Role of Sb Compositions on the Properties of InAs/GaAsSb Quantum Dots (QDs)

    Energy Technology Data Exchange (ETDEWEB)

    Ban, K. Y.; Bremner, S. P.; Kuciauskas, D.; Dahal, S. N.; Honsberg, C. B.

    2012-01-01

    QD size, uniformity and density in InAs/GaAsSb material system for increasing Sb content are studied using Atomic Force Microscopy (AFM). AFM results show that QD density and uniformity improve with Sb content increase. The improvement of QD uniformity is ensured by the narrowing of the analysis of AFM scans. To obtain minimum VBO, InAs/GaAsSb with various Sb compositions is investigated by PL and TRPL measurements. PL data shows a blue-shift as excitation power increases as evidence of a type II band structure. Since the PL peak of 8 and 13 % Sb samples did not shift while that of 15 % Sb sample is blue-shifted with increasing the excitation power it is concluded that InAs QDs/GaAs0.86Sb0.14 would have minimum valence band offset. This tendency is supported by the change of a carrier lifetime estimated from TRPL data.

  9. Characterization of Cr-doped Sb{sub 2}Te{sub 3} films and their application to phase-change memory

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qing; Xia, Yangyang; Zheng, Yonghui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); University of the Chinese Academy of Sciences, Beijing, 100049 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); Liu, Bo; Zhu, Min; Song, Sannian; Lv, Shilong; Cheng, Yan; Song, Zhitang; Feng, Songlin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); Huo, Ruru [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); Shanghai Key Laboratory of Nanofabrication Technology for Memory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 (China); Shanghaitech University, Shanghai, 200031 (China)

    2015-08-15

    Phase-change memory (PCM) is regarded as one of the most promising candidates for the next-generation nonvolatile memory. Its storage medium, phase-change material, has attracted continuous exploration. Along the traditional GeTe-Sb{sub 2}Te{sub 3} tie line, the binary compound Sb{sub 2}Te{sub 3} is a high-speed phase-change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb{sub 2}Te{sub 3}, called Cr-Sb{sub 2}Te{sub 3} (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb{sub 2}Te{sub 3} without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST{sub 1}0.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10-year data retention is 120.8 C, which indicates better thermal stability than GST and pure Sb{sub 2}Te{sub 3}. PCM cells based on CST{sub 1}0.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr-Sb{sub 2}Te{sub 3} with suitable composition is a promising novel phase-change material used for PCM with high speed and good thermal stability performances. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Ge/SiGe superlattices for nanostructured thermoelectric modules

    Energy Technology Data Exchange (ETDEWEB)

    Chrastina, D., E-mail: daniel@chrastina.net [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Cecchi, S. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Hague, J.P. [Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); Frigerio, J. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Samarelli, A.; Ferre–Llin, L.; Paul, D.J. [School of Engineering, University of Glasgow, Oakfield Avenue, Glasgow, G12 8LT (United Kingdom); Müller, E. [Electron Microscopy ETH Zurich (EMEZ), ETH-Zürich, CH-8093 (Switzerland); Etzelstorfer, T.; Stangl, J. [Institut für Halbleiter und Festkörperphysik, Universität Linz, A-4040 Linz (Austria); Isella, G. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy)

    2013-09-30

    Thermoelectrics are presently used in a number of applications for both turning heat into electricity and also for using electricity to produce cooling. Mature Si/SiGe and Ge/SiGe heteroepitaxial growth technology would allow highly efficient thermoelectric materials to be engineered, which would be compatible and integrable with complementary metal oxide silicon micropower circuits used in autonomous systems. A high thermoelectric figure of merit requires that electrical conductivity be maintained while thermal conductivity is reduced; thermoelectric figures of merit can be improved with respect to bulk thermoelectric materials by fabricating low-dimensional structures which enhance the density of states near the Fermi level and through phonon scattering at heterointerfaces. We have grown and characterized Ge-rich Ge/SiGe/Si superlattices for nanofabricated thermoelectric generators. Low-energy plasma-enhanced chemical vapor deposition has been used to obtain nanoscale-heterostructured material which is several microns thick. Crystal quality and strain control have been investigated by means of high resolution X-ray diffraction. High-resolution transmission electron microscopy images confirm the material and interface quality. Electrical conductivity has been characterized by the mobility spectrum technique. - Highlights: ► High-quality Ge/SiGe multiple quantum wells for thermoelectric applications ► Mobility spectra of systems featuring a large number of parallel conduction channels ► Competitive thermoelectric properties measured in single devices.

  11. Reference: SB3NPABC1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available SB3NPABC1 Grec S, Vanham D, de Ribaucourt J, Purnelle B, Boutry P. Identification o...f regulatory sequence elements within the transcription promoter region of NpABC1, a gene encoding a plant ABC

  12. Reference: SB1NPABC1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available SB1NPABC1 Grec S, Vanham D, de Ribaucourt J, Purnelle B, Boutry P. Identification o...f regulatory sequence elements within the transcription promoter region of NpABC1, a gene encoding a plant ABC

  13. Antimony (Sb) contaminated shooting range soil: Sb mobility and immobilization by soil amendments.

    Science.gov (United States)

    Okkenhaug, Gudny; Amstätter, Katja; Lassen Bue, Helga; Cornelissen, Gerard; Breedveld, Gijs D; Henriksen, Thomas; Mulder, Jan

    2013-06-18

    Antimony (Sb) in lead bullets poses a major environmental risk in shooting range soils. Here we studied the effect of iron (Fe)-based amendments on the mobility of Sb in contaminated soil from shooting ranges in Norway. Untreated soil showed high Sb concentrations in water extracts from batch tests (0.22-1.59 mg L(-1)) and soil leachate from column tests (0.3-0.7 mg L(-1)), occurring exclusively as Sb(V). Sorption of Sb to different iron-based sorbents was well described by the Freundlich equation (Fe2(SO4)3, log KF = 6.35, n = 1.51; CFH-12 (Fe oxyhydroxide), log KF = 4.16-4.32, n = 0.75-0.76); Fe(0) grit, log KF = 3.26, n = 0.47). These sorbents mixed with soil (0.5 and 2% w/w), showed significant sorption of Sb in batch tests (46-92%). However, for Fe2(SO4)3 and CFH-12 liming was also necessary to prevent mobilization of lead, copper, and zinc. Column tests showed significant retention of Sb (89-98%) in soil amended with CFH-12 (2%) mixed with limestone (1%) compared to unamended soil. The sorption capacity of soils amended with Fe(0) (2%) increased steadily up to 72% over the duration period of the column test (64 days), most likely due to the gradual oxidation of Fe(0) to Fe oxyhydroxides. Based on the experimental results, CFH-12 and oxidized Fe(0) are effective amendments for the stabilization of Sb in shooting range soils.

  14. Spectrophotometric determination of Sb(III) and Sb(V) in biological samples after micelle-mediated extraction.

    Science.gov (United States)

    Madrakian, Tayyebeh; Bozorgzadeh, Elaheh

    2009-10-30

    This work presents a micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and bromopyrogallol red (BPR) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 6.4. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and improvement factors) were obtained. Linearity for Sb(III) and Sb(V) were obeyed in the range of 0.2-20.0 ng mL(-1) and 0.4-25.0 ng mL(-1), respectively. The detection limit for the determination of Sb(III) and Sb(V) were 0.05 ng mL(-1) and 0.08 ng mL(-1), respectively. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma and urine samples.

  15. Effects of Sb Substitution by Sn on the Thermoelectric Properties of ZrCoSb

    Science.gov (United States)

    Yuan, Bo; Wang, Bo; Huang, Lihong; Lei, Xiaobo; Zhao, Lidong; Wang, Chao; Zhang, Qinyong

    2016-12-01

    ZrCoSb1-x Sn x (x = 0, 0.1, 0.2, 0.3, 0.35) half-Heusler (HH) samples were prepared by arc melting, ball milling and then hot-pressing. X-ray diffraction analysis results showed that all samples were crystallized in a HH phase. Thermoelectric (TE) properties of ZrCoSb1-x Sn x were measured from room temperature (RT) to 973 K. The Seebeck coefficient changed from negative to positive after substituting Sb with Sn, indicating the occurrence of conduction type transformation in ZrCoSb-based HH compounds. At the same time, the Seebeck coefficient decreased with increasing Sn substitution, and the electrical conductivity increased obviously with Sn addition when x ≤ 0.3. The lattice thermal conductivity of Sn-substituted samples was reduced dramatically because of the stronger phonon scattering by the strain field fluctuation induced by Sn replacement of Sb. Finally, as a result of the Sn substitution, a peak ZT of 0.52 was reached at 973 K in the ZrCoSb0.7Sn0.3 sample.

  16. Quantum dots formed in InSb/AlAs and AlSb/AlAs heterostructures

    Science.gov (United States)

    Abramkin, D. S.; Rumynin, K. M.; Bakarov, A. K.; Kolotovkina, D. A.; Gutakovskii, A. K.; Shamirzaev, T. S.

    2016-06-01

    The crystal structure of new self-assembled InSb/AlAs and AlSb/AlAs quantum dots grown by molecularbeam epitaxy has been investigated by transmission electron microscopy. The theoretical calculations of the energy spectrum of the quantum dots have been supplemented by the experimental data on the steady-state and time-resolved photoluminescence spectroscopy. Deposition of 1.5 ML of InSb or AlSb on the AlAs surface carried out in the regime of atomic-layer epitaxy leads to the formation of pseudomorphically strained quantum dots composed of InAlSbAs and AlSbAs alloys, respectively. The quantum dots can have the type-I and type-II energy spectra depending on the composition of the alloy. The ground hole state in the quantum dot belongs to the heavy-hole band and the localization energy of holes is much higher than that of electrons. The ground electron state in the type-I quantum dots belongs to the indirect X XY valley of the conduction band of the alloy. The ground electron state in the type-II quantum dots belongs to the indirect X valley of the conduction band of the AlAs matrix.

  17. Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining

    Energy Technology Data Exchange (ETDEWEB)

    Cidu, Rosa, E-mail: cidur@unica.it; Biddau, Riccardo; Dore, Elisabetta

    2015-01-07

    Highlights: • Antimony speciation affects the toxicity of this element. • A simple method for Sb(III) analyses in Sb-rich waters was developed. • Sb(III) was determined by ASV in water stabilized with tartaric and nitric acids. • Pre-concentration and/or separation of Sb(III) prior to analysis are not required. - Abstract: Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1–20 μg L{sup −1} working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1–100 μg L{sup −1} working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100–10,000 μg L{sup −1} working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO{sub 3}. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO{sub 3}, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L{sup −1}), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO{sub 3} appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main

  18. Isospin structure in 68Ge

    Institute of Scientific and Technical Information of China (English)

    BAI Hong-Bo; DONG Hong-Fei; ZHANG Jin-Fu; LU Li-Jun; CAO Wan-Cang; LI Xiao-Wei; WANg Yin

    2009-01-01

    The interacting boson model-3(IBM-3) has been used to study the low-energy level structure and electromagnetic transitions of 68Ge nucleus. The main components of the wave function for some states are also analyzed respectively. The theoretical calculations are in agreement with experimental data, and the 68Ge is in transition from U(5) to SU(3).

  19. 12 GeV Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    None

    2017-01-01

    To expand the opportunity for discovery, Jefferson Lab is upgrading its facility by doubling the maximum energy of CEBAF's electron beam from 6 billion electron volts (GeV) to 12 billion electron volts (GeV), constructing a new experimental hall and upgrading its three existing experimental halls.

  20. Sorghum phytochrome B inhibits flowering in long days by activating expression of SbPRR37 and SbGHD7, repressors of SbEHD1, SbCN8 and SbCN12.

    Directory of Open Access Journals (Sweden)

    Shanshan Yang

    Full Text Available Light signaling by phytochrome B in long days inhibits flowering in sorghum by increasing expression of the long day floral repressors PSEUDORESPONSE REGULATOR PROTEIN (SbPRR37, Ma1 and GRAIN NUMBER, PLANT HEIGHT AND HEADING DATE 7 (SbGHD7, Ma6. SbPRR37 and SbGHD7 RNA abundance peaks in the morning and in the evening of long days through coordinate regulation by light and output from the circadian clock. 58 M, a phytochrome B deficient (phyB-1, ma3R genotype, flowered ∼60 days earlier than 100 M (PHYB, Ma3 in long days and ∼11 days earlier in short days. Populations derived from 58 M (Ma1, ma3R, Ma5, ma6 and R.07007 (Ma1, Ma3, ma5, Ma6 varied in flowering time due to QTL aligned to PHYB/phyB-1 (Ma3, Ma5, and GHD7/ghd7-1 (Ma6. PHYC was proposed as a candidate gene for Ma5 based on alignment and allelic variation. PHYB and Ma5 (PHYC were epistatic to Ma1 and Ma6 and progeny recessive for either gene flowered early in long days. Light signaling mediated by PhyB was required for high expression of the floral repressors SbPRR37 and SbGHD7 during the evening of long days. In 100 M (PHYB the floral activators SbEHD1, SbCN8 and SbCN12 were repressed in long days and de-repressed in short days. In 58 M (phyB-1 these genes were highly expressed in long and short days. Furthermore, SbCN15, the ortholog of rice Hd3a (FT, is expressed at low levels in 100 M but at high levels in 58 M (phyB-1 regardless of day length, indicating that PhyB regulation of SbCN15 expression may modify flowering time in a photoperiod-insensitive manner.

  1. 尼康SB-600闪光灯

    Institute of Scientific and Technical Information of China (English)

    王三丁

    2005-01-01

    2004年1月,尼康公司在发布尼康D70的同时,推出了一款与之配套的闪光灯——SB-600。产品定位在SB-800之下,与之前的SB-50DX、SB-27属同一等级。由于继承了SB-800的一系列新功能,SB-600在支持数码相机方面较以前的闪光灯更为优秀,在用于传统相机时也毫不逊色。下面仅就个人的使用感受谈谈SB-600闪光灯的一些特点。

  2. Glassy Transformation and Structural Change in Ge2Sb2Te5 Studied by Impedance Measurements

    Science.gov (United States)

    2001-06-01

    IMPEDANCE MEASUREMENTS E. Morales-Sinchezab, J. Gonzailez-Hermnndeza, E. Prokhorova "Centro de Investigaci6n y de Estudios Avanzados del IPN, Unidad...Quer6taro, Ap. Postal 1- 798, 76001, Quer6taro, Qro., Mexico. bDivisi6n de Estudios de Posgrado, Facultad de Ingenieria, UAQ, Querdtaro, Mexico. The

  3. New metal atom laser transitions in As, Bi, Ga, Ge, Hg, In, Pb, Sb, and Tl

    Science.gov (United States)

    Chou, M. S.; Cool, T. A.

    1976-01-01

    A double discharge technique was used in the investigation. An initial discharge established between parallel arrays of tungsten pin electrodes was followed, after a variable time delay, by a high voltage (180 kV), short duration (50 nsec) secondary discharge between two aluminum main electrodes. Metal compounds, including metal alkyls, hydrides, and halides, were used to obtain the required metal atom concentrations. Twenty-four new laser transitions involving 9 different metal atoms were observed. The observed relations are shown in a number of partial energy-level diagrams.

  4. Size-dependent and tunable crystallization of GeSbTe phasechange nanoparticles

    NARCIS (Netherlands)

    Chen, Bin; ten Brink, Gerrit; Palasantzas, Georgios; Kooi, Bart

    2016-01-01

    Chalcogenide-based nanostructured phase-change materials (PCMs) are considered promising building blocks for non-volatile memory due to their high write and read speeds, high data-storage density, and low power consumption. Top-down fabrication of PCM nanoparticles (NPs), however, often results in d

  5. Crystallization Kinetics of GeSbTe Phase-Change Nanoparticles Resolved by Ultrafast Calorimetry

    NARCIS (Netherlands)

    Chen, Bin; Brink, ten Gert; Palasantzas, Georgios; Kooi, Bart J.

    2017-01-01

    Although nanostructured phase-change materials (PCMs) are considered as the building blocks of next-generation phase-change memory and other emerging optoelectronic applications, the kinetics of the crystallization, the central property in switching, remains ambiguous in the high-temperature regime.

  6. Desempenho de misturas betuminosas com betume modificado com borracha através do processo húmido

    OpenAIRE

    2007-01-01

    Este trabalho apresenta os resultados da avaliação de desempenho mecânico de misturas betuminosas produzidas com betume modificado com borracha de pneus usados através do processo húmido, utilizando o sistema terminal blend e o sistema continuous blend. Os betumes modificados com borracha através dos dois sistemas foram caracterizados através dos seguintes ensaios: (i) penetração; (ii) ponto de amolecimento (método anel e bola); (iii) resiliência; (iv) viscosidade Brookfield. A avaliação do c...

  7. Effect of InSb/In0.9Al0.1Sb superlattice buffer layer on the structural and electronic properties of InSb films

    Science.gov (United States)

    Zhao, Xiaomeng; Zhang, Yang; Guan, Min; Cui, Lijie; Wang, Baoqiang; Zhu, Zhanping; Zeng, Yiping

    2017-07-01

    The effect of InSb/In0.9Al0.1Sb buffer layers on InSb thin films grown on GaAs (0 0 1) substrate by molecular beam epitaxy (MBE) is investigated. The crystal quality and the surface morphology of InSb are characterized by XRD and AFM. The carrier transport property is researched through variable temperature hall test. The sharp interface between InSb/In0.9Al0.1Sb is demonstrated important for the high quality InSb thin film. We try different superlattice buffer layers by changing ratios, 2-0.5, thickness, 300-450 nm, and periods, 20-50. According to the function of the dislocation density to the absolute temperature below 150 K with different periods of SL buffers, we can find that the number of periods of superlattice is a major factor to decrease the density of threading dislocations. With the 50 periods SL buffer layer, the electron mobility of InSb at the room temperature and liquid nitrogen cooling temperature is ∼63,000 and ∼4600 cm2/V s, respectively. We deduce that the interface in the SL structure works as a filter layer to prevent the dislocation propagating to the upper InSb thin films.

  8. Recent progress in InGaAsSb/GaSb TPV devices

    Energy Technology Data Exchange (ETDEWEB)

    Shellenbarger, Z.A.; Mauk, M.G.; DiNetta, L.C. [AstroPower, Inc., Newark, DE (United States); Charache, G.W. [Lockheed Martin Corp., Schenectady, NY (United States)

    1996-05-01

    AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In{sub 1{minus}x}Ga{sub x}As{sub 1{minus}y}Sb{sub y} alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y); and is closely lattice-matched to the GaSb substrate. The use of the quaternary alloy, as opposed to a ternary alloy--such as, for example InGaAs/InP--permits low bandgap devices optimized for 1,000 to 1,500 C thermal sources with, at the same time, near-exact lattice matching to the GaSb substrate. Lattice matching is important since even a small degree of lattice mismatch degrades device performance and reliability and increases processing complexity. Internal quantum efficiencies as high as 95% have been measured at a wavelength of 2 microns. At 1 micron wavelengths, internal quantum efficiencies of 55% have been observed. The open-circuit voltage at currents of 0.3 A/cm{sup 2} is 0.220 volts and 0.280 V for current densities of 2 A/cm{sup 2}. Fill factors of 56% have been measured at 60 mA/cm{sup 2}. However, as current density increases there is some decrease in fill factor. The results to date show that the GaSb-based quaternary compounds provide a viable and high performance energy conversion solution for thermophotovoltaic systems operating with 1,000 to 1,500 C source temperatures.

  9. Standardizing large format 5" GaSb and InSb substrate production

    Science.gov (United States)

    Martinez, Becky; Flint, J. Patrick; Dallas, G.; Smith, B.; Tybjerg, M.; Aravazhi, Shanmugam; Furlong, Mark J.

    2017-02-01

    In this paper we report on the maturation of large diameter GaSb and InSb substrate production and the key aspects of product quality and process control that have enabled a level of standardization to be achieved that is on par with mass produced compound semiconductor materials such as GaAs and InP. The evolution of commercial production processes for the crystal growth, wafering and epitaxy-ready polishing of antimonide substrates will be discussed together with specific reference to the process tool sets and production methodologies that have transformed a niche material in to one that has set new standards for wafer level product quality, conformity and control. Results will be presented on the production of single crystal >/=6" ingots grown by a modified version of the Czochralski (LEC) technique. Crystal defect mapping will demonstrate that industry standard InSb (211) growth processes have been refined to consistently deliver ultralow dislocation density substrates. Statistical process control data will be presented for large format 5" epitaxy ready finishing processes and compared alongside in-house data for GaAs and InP. Various surface analytical tools are used to characterize 5" InSb and GaSb substrates and our method of providing a unique characterization `finger print' with each substrate discussed. We conclude that improvements in InSb and GaSb product quality and consistency have been driven by the industry's persistent need to improve device performance and yield. Whilst substrate size requirements in antimonide wafer production may have peaked, we will discuss how to moving to the next step in substrate diameters, 6", is very attainable and within relatively short timescales too.

  10. Monolithically integrated Ge CMOS laser

    Science.gov (United States)

    Camacho-Aguilera, Rodolfo

    2014-02-01

    Ge-on-Si devices are explored for photonic integration. Through the development of better growth techniques, monolithic integration, laser design and prototypes, it was possible to probe Ge light emitters with emphasis on lasers. Preliminary worked shows thermal photonic behavior capable of enhancing lamination at high temperatures. Increase luminescence is observed up to 120°C from L-band contribution. Higher temperatures show contribution from Δ -band. The increase carrier thermal contribution suggests high temperature applications for Ge light emitters. A Ge electrically pumped laser was probed under 0.2% biaxial strain and doping concentration ~4.5×1019cm-3 n-type. Ge pnn lasers exhibit a gain >1000cm-1 with 8mW power output, presenting a spectrum range of over 200nm, making Ge the ideal candidate for Si photonics. Large temperatures fluctuations and process limit the present device. Theoretically a gain of >4000cm- gain is possible with a threshold of as low as 1kA/cm2. Improvements in Ge work

  11. Ge-on-Si optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jifeng, E-mail: Jifeng.Liu@Dartmouth.edu [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Camacho-Aguilera, Rodolfo; Bessette, Jonathan T.; Sun, Xiaochen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wang Xiaoxin [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Cai Yan; Kimerling, Lionel C.; Michel, Jurgen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2012-02-01

    Electronic-photonic synergy has become an increasingly clear solution to enhance the bandwidth and improve the energy efficiency of information systems. Monolithic integration of optoelectronic devices is the ideal solution for large-scale electronic-photonic synergy. Due to its pseudo-direct gap behavior in optoelectronic properties and compatibility with Si electronics, epitaxial Ge-on-Si has become an attractive solution for monolithic optoelectronics. In this paper we will review recent progress in Ge-on-Si optoelectronics, including photodetectors, electroabsorption modulators, and lasers. The performance of these devices has been enhanced by band-engineering such as tensile strain and n-type doping, which transforms Ge towards a direct gap material. Selective growth reduces defect density and facilitates monolithic integration at the same time. Ge-on-Si photodetectors have approached or exceeded the performance of their III-V counterparts, with bandwidth-efficiency product > 30 GHz for p-i-n photodiodes and bandwidth-gain product > 340 GHz for avalanche photodiodes. Enhanced Franz-Keldysh effect in tensile-strained Ge offers ultralow energy photonic modulation with < 30 fJ/bit energy consumption and > 100 GHz intrinsic bandwidth. Room temperature optically-pumped lasing as well as electroluminescence has also been achieved from the direct gap transition of band-engineered Ge-on-Si waveguides. These results indicate that band-engineered Ge-on-Si is promising to achieve monolithic active optoelectronic devices on a Si platform.

  12. Design and development of SiGe based near-infrared photodetectors

    Science.gov (United States)

    Zeller, John W.; Puri, Yash R.; Sood, Ashok K.; McMahon, Shane; Efsthadiatis, Harry; Haldar, Pradeep; Dhar, Nibir K.

    2014-10-01

    Near-infrared (NIR) sensors operating at room temperatures are critical for a variety of commercial and military applications including detecting mortar fire and muzzle flashes. SiGe technology offers a low-cost alternative to conventional IR sensor technologies such as InGaAs, InSb, and HgCdTe for developing NIR micro-sensors that will not require any cooling and can operate with high bandwidths and comparatively low dark currents. Since Ge has a larger thermal expansion coefficient than Si, tensile strain may be incorporated into detector devices during the growth process, enabling an extended operating wavelength range above 1600 nm. SiGe based pin photodetectors have advantages of high stability, low noise, and high responsivity compared to metal-semiconductor-metal (MSM) devices. We have developed a process flow and are fabricating SiGe detector devices on 12" (300 mm) silicon wafers in order to take advantage of high throughput, large-area leading-edge silicon based CMOS technology that provides small feature sizes with associated device cost/density scaling advantages. The fabrication of the detector devices is facilitated by a two-step growth process incorporating initial low temperature growth of Ge/SiGe to form a thin strain-relaxed layer, followed by high temperature growth to deposit a thicker absorbing film, and subsequent high temperature anneal. This growth process is designed to effectively reduce dark current and enhance detector performance by reducing the number of defects and threading dislocations which form recombination centers during the growth process. Various characterization techniques have been employed to determine the properties of the epitaxially deposited Ge/SiGe layers, and the corresponding results are discussed.

  13. Insights into the all-metal [Sb3Au3Sb3]3- sandwich complex from a QTAIM and stress tensor analysis

    Science.gov (United States)

    Wang, Lingling; Ping, Yang; Momen, Roya; Azizi, Alireza; Xu, Tianlv; Rodríguez, Juan I.; Anderson, James S. M.; Kirk, Steven R.; Jenkins, Samantha

    2017-10-01

    A QTAIM investigation of the [Sb3Au3Sb3]3- sandwich complex is consistent with a previous investigation and reveals all of the bond critical points (BCPs) to be closed-shell BCPs with a degree of covalent character. All of the Sb-Au BCPs and Sb-Sb BCPs are found to possess metallicity. From the stress tensor analysis a topological instability in the Sb-Au BCPs and Sb-Sb BCPs is revealed highlighting the need for an improved charge density. The topological instability is removed by using the SR-ZORA method to describe relativistic effects.

  14. Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2

    Science.gov (United States)

    Liu, Jinyu; Hu, Jin; Cao, Huibo; Zhu, Yanglin; Chuang, Alyssa; Graf, D.; Adams, D. J.; Radmanesh, S. M. A.; Spinu, L.; Chiorescu, I.; Mao, Zhiqiang

    2016-01-01

    Layered compounds AMnBi2 (A = Ca, Sr, Ba, or rare earth element) have been established as Dirac materials. Dirac electrons generated by the two-dimensional (2D) Bi square net in these materials are normally massive due to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes. Here we report that the Sb square net in an isostructural compound BaMnSb2 can host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH) oscillations in this material. From the analyses of the SdH oscillations, we find key signatures of Dirac fermions, including light effective mass (~0.052m0; m0, mass of free electron), high quantum mobility (1280 cm2V−1S−1) and a π Berry phase accumulated along cyclotron orbit. Compared with AMnBi2, BaMnSb2 also exhibits much more significant quasi two-dimensional (2D) electronic structure, with the out-of-plane transport showing nonmetallic conduction below 120 K and the ratio of the out-of-plane and in-plane resistivity reaching ~670. Additionally, BaMnSb2 also exhibits a G-type antiferromagnetic order below 283 K. The combination of nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless Dirac electrons. PMID:27466151

  15. <300> GeV team

    CERN Multimedia

    1971-01-01

    The 300 GeV team had been assembled. In the photograph are Hans Horisberger, Clemens Zettler, Roy Billinge, Norman Blackburne, John Adams, Hans-Otto Wuster, Lars Persson, Bas de Raad, Hans Goebel, Simon Van der Meer.

  16. Synthesis of B–Sb by rapid thermal annealing of B/Sb multilayer films

    Indian Academy of Sciences (India)

    S N Das; A K Pal

    2006-11-01

    Group III–V compound B–Sb films were synthesized from B/Sb/…/B multilayer films deposited by electron gun evaporation onto silicon substrate and subjecting the above multilayer to rapid thermal annealing at 773 K for 3 min. The films were characterized by XRD, TEM, XPS and optical studies. XPS studies indicated the ratio of B : Sb ∼1. XRD and electron diffraction patterns indicated the reflections from (100), (111), (102) and (112) planes of zinc blende BSb. Band gap evaluated from optical studies was ∼ 0.51 eV. Refractive index of the films varied between 1.65 and 2.18 with increasing energy of incident photon and plasma frequency (p) was estimated to be ∼ 2.378 × 10-14 s-1. The effective mass was computed to be ∼ 0.0845 m.

  17. GaInSb and GaInAsSb thermophotovoltaic device fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hitchcock, C.; Gutmann, R.; Borrego, J.; Ehsani, H.; Bhat, I. [Rensselaer Polytechnic Inst., Troy, NY (United States); Freeman, M.; Charache, G. [Lockheed Martin, Inc., Schenectady, NY (United States)

    1997-05-01

    Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. The GaInSb layers were grown by organometallic vapor phase epitaxy (OMVPE) and the InGaAsSb lattice-matched layers were grown by liquid phase epitaxy (LPE). Device fabrication steps include unannealed p-type ohmic contacts, annealed Sn/Au n-type ohmic contacts, and a thick Ag top-surface contact using a lift-off process. Devices are characterized primarily by dark I-V, photo I-V, and quantum efficiency measurements, which are correlated to microscopic and macroscopic material properties. Particular emphasis has been on material enhancements to increase quantum efficiency and decrease dark saturation current density. TPV device performance is presently limited by the base diffusion length, typically 1 to 2 microns.

  18. v.+sb.+of+sth.与v.+sth.+of+sb.结构辨析

    Institute of Scientific and Technical Information of China (English)

    张思永

    2006-01-01

    v.+sb.+of+sth.与v.+sth.+of+sb..这两个结构在英语学习中很容易混淆,两者的共同点是动词v.都与介词0f有搭配关系,不同之处是两个结构中的sb.与sth.跟动词v.与介词of的相对位置不同。下面我们来看看哪些动词常用在前一结构中,哪些动词常用在后一结构中。

  19. Optical and structural properties of MOVPE-grown GaInSb/GaSb quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, Viera, E-mail: viera.wagener@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Olivier, E.J.; Botha, J.R. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2009-12-15

    This paper reports on the optical and structural properties of strained type-I Ga{sub 1-x}In{sub x}Sb quantum wells embedded in GaSb from a metal-organic vapour phase epitaxial growth perspective. Photoluminescence measurements and transmission electron microscopy were used to evaluate the effect of the growth temperature on the quality of Ga{sub 1-x}In{sub x}Sb strained layers with varied alloy compositions and thicknesses. Although the various factors contributing to the overall quality of the strained layers are difficult to separate, the quantum well characteristics are significantly altered by the growth temperature. Despite the high growth rates (approx2 nm/s), quantum wells grown at 607 deg. C display photoluminescence emissions with full-width at half-maximum of 3.5-5.0 meV for an indium solid content (x) up to 0.15.

  20. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Science.gov (United States)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U.

    2016-12-01

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between S b 2 S 3 and I n and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40-60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 1017 cm-3 and 1000 cm2 V-1 s-1, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  1. DWPF Simulant CPC Studies For SB8

    Energy Technology Data Exchange (ETDEWEB)

    Newell, J. D.

    2013-09-25

    Prior to processing a Sludge Batch (SB) in the Defense Waste Processing Facility (DWPF), flowsheet studies using simulants are performed. Typically, the flowsheet studies are conducted based on projected composition(s). The results from the flowsheet testing are used to 1) guide decisions during sludge batch preparation, 2) serve as a preliminary evaluation of potential processing issues, and 3) provide a basis to support the Shielded Cells qualification runs performed at the Savannah River National Laboratory (SRNL). SB8 was initially projected to be a combination of the Tank 40 heel (Sludge Batch 7b), Tank 13, Tank 12, and the Tank 51 heel. In order to accelerate preparation of SB8, the decision was made to delay the oxalate-rich material from Tank 12 to a future sludge batch. SB8 simulant studies without Tank 12 were reported in a separate report.1 The data presented in this report will be useful when processing future sludge batches containing Tank 12. The wash endpoint target for SB8 was set at a significantly higher sodium concentration to allow acceptable glass compositions at the targeted waste loading. Four non-coupled tests were conducted using simulant representing Tank 40 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry (146% acid) SRAT testing up to 31% of the DWPF hydrogen limit. SME hydrogen generation reached 48% of of the DWPF limit for the high acid run. Two non-coupled tests were conducted using simulant representing Tank 51 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry SRAT testing up to 16% of the DWPF limit. SME hydrogen generation reached 49% of the DWPF limit for hydrogen in the SME for the high acid run. Simulant processing was successful using previously established antifoam addition strategy. Foaming during formic acid addition was not observed in any of the runs. Nitrite was destroyed in all runs and no N2O was detected

  2. Microstructure evolution of directionally solidified Sn-16%Sb hyperperitectic alloy

    Institute of Scientific and Technical Information of China (English)

    Hu Xiaowu; Li Shuangming; Liu Lin; Fu Hengzhi

    2008-01-01

    The directionally solidified microstructure of Sn-16%Sb hyperperitectic alloy has been investigated at various solidification rates using a high-thermal gradient directional solidification apparatus. The results indicate that the solidification microstructure consists of hard primary intermetallic SnSb phase embedded in a matrix of soft peritectic β-Sn phase. The primary SnSb phase exhibits faceted growth with tetragonal or trigonal shapes. At the same time, the primary SnSb phase is refined with an increase in the solidification rate and dispersed more uniformly in the matrix of β-Sn phase. The volume fraction of the SnSb phase firstly decreases and then increases when the solidification rate increases in directional solidification of Sn-16%Sb hyperperitectic alloy.

  3. Estudo dos ruidos articulares atraves da tecnica artrosonografica dos joelhos normais de individuos jovens

    OpenAIRE

    Roberto Natalino Ricarte

    1987-01-01

    Resumo: Os ruídos articulares do joelho esquerdo normal de 43 indivíduos jovens de ambos os sexos, sendo 20 do sexo masculino e 23 do sexo feminino, foram analisados através da técnica artrosonográfica. As gravações destes ruídos obtidas em uma sala acústica, onde buscamos diminuir e foram evitar os possiveis ruidos extrinsecos as gravaçoes. Estes ruidos foram transportados posteriormente para um gravador de rolo acoplado a um eletromiógrafo, de onde obtivemos a análise dos ruídos articulares...

  4. Espectroscopia de alta sensibilidade através do uso de cavidades ópticas

    OpenAIRE

    Marvyn William Inga Caqui

    2016-01-01

    Neste trabalho desenvolvemos uma montagem óptica para realizar espectroscopia de alta sensibilidade através de medidas do tempo de decaimento da luz em uma cavidade óptica contendo uma amostra transparente (ring-down time spectroscopy). Usando um laser contínuo de comprimento de onda único em S32nm e uma cavidade de finesse moderada (16500), optamos por explorar o uso deste sistema para análise de amostras líquidas ou sólidas, ao invés do uso tradicional em espectroscopia de gases. Para isto ...

  5. Thermal instability of GaSb surface oxide

    Science.gov (United States)

    Tsunoda, K.; Matsukura, Y.; Suzuki, R.; Aoki, M.

    2016-05-01

    In the development of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, the surface leakage current at the mesa sidewall must be suppressed. To achieve this requirement, both the surface treatment and the passivation layer are key technologies. As a starting point to design these processes, we investigated the GaSb oxide in terms of its growth and thermal stability. We found that the formation of GaSb oxide was very different from those of GaAs. Both Ga and Sb are oxidized at the surface of GaSb. In contrast, only Ga is oxidized and As is barely oxidized in the case of GaAs. Interestingly, the GaSb oxide can be formed even in DI water, which results in a very thick oxide film over 40 nm after 120 minutes. To examine the thermal stability, the GaSb native oxide was annealed in a vacuum and analyzed by XPS and Raman spectroscopy. These analyses suggest that SbOx in the GaSb native oxide will be reduced to metallic Sb above 300°C. To directly evaluate the effect of oxide instability on the device performance, a T2SL p-i-n photodetector was fabricated that has a cutoff wavelength of about 4 μm at 80 K. As a result, the surface leakage component was increased by the post annealing at 325°C. On the basis of these results, it is possible to speculate that a part of GaSb oxide on the sidewall surface will be reduced to metallic Sb, which acts as an origin of additional leakage current path.

  6. High operating temperature InAlSb infrared detectors

    Science.gov (United States)

    Li, Mo; Chen, Gang; Li, Hao; Zhang, Zhaofan; Peng, Pan; Lv, Yanqiu

    2016-10-01

    The recent progresses of our research in InxAl1-xSb infrared detector based on molecular beam epitaxy are presented. Al composition with 0-0.3 is used for adjusting energy gaps of InSb and a p-i-n structure is utilized to decrease dark current. InxAl1-xSb ternary alloys are grown by molecular beam epitaxy on InSb substrates, and the material quality is characterized using high resolution x-ray diffraction. In order to exploit this epitaxial material we have developed new mesa and passivation technology based on matured InSb fabrication process. The InAlSb diodes has a cut-off wavelength of around 4.8μm. The reverse bias dark current of InAlSb diodes have been measured. The dark current of the pin InAlSb diode is seen to smaller that of the bulk p+n InSb diodes by 4-5 times in 77K.

  7. Viscosity of In and In-Sb alloys

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The dynamic viscosity of pure In, In-1%Sb (mass fraction, so as the follows) alloy, In-55%Sb hypoeutectic alloyand In-69.5%Sb eutectic alloy was measured by using a torsional oscillation viscometer at different temperatures above liq-uidus. The experimental results show that the viscosity of these melts decreases with increasing temperature. The anomalouschange of viscosity occurs at about 430 and 470℃ in pure In melt. The variation of viscosity with temperature well meetsexponential correlation and no anomalous change occurs in measured temperature range in the In-1%Sb alloy melt. A tran-sition occurs at about 800℃ in both of In-55%Sb and In-69.5%Sb alloy melts. The sudden change of viscosity suggests thestructure change of melts. DSC (differential scanning calorimetry) curves of In-1%Sb alloy during heating and cooling weremeasured, and the results show that no structural variation in In-1%Sb alloy melt was testified further. In addition, the vis-cosity of In melt decreases with the addition of 1%Sb.

  8. Temperature dependence of thermal properties of Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} phase-change memory materials

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Xinbing; Gan, Fuxi [Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences, Shanghai (China); Wei, Jingsong [Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences, Shanghai (China); Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Ensenada, Baja California (Mexico); Xiao, Mufei [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Ensenada, Baja California (Mexico)

    2009-03-15

    The dependence of thermal properties of Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} phase-change memory materials in crystalline and amorphous states on temperature was measured and analyzed. The results show that in the crystalline state, the thermal properties monotonically decrease with the temperature and present obvious crystalline semiconductor characteristics. The heat capacity, thermal diffusivity, and thermal conductivity decrease from 0.35 J/gK, 1.85 mm{sup 2}/s, and 4.0 W/mK at 300 K to 0.025 J/gK, 1.475 mm{sup 2}/s, and 0.25 W/mK at 600 K, respectively. In the amorphous state, while the dependence of thermal properties on temperature does not present significant changes, the materials retain the glass-like thermal characteristics. Within the temperature range from 320 K to 440 K, the heat capacity fluctuates between 0.27 J/gK and 0.075 J/gK, the thermal diffusivity basically maintains at 0.525 mm{sup 2}/s, and the thermal conductivity decreases from 1.02 W/mK at 320 K to 0.2 W/mK at 440 K. Whether in the crystalline or amorphous state, Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} are more thermally active than Ge{sub 2}Sb{sub 2}Te{sub 5}, that is, the Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} composites bear stronger thermal conduction and diffusion than the Ge{sub 2}Sb{sub 2}Te{sub 5} phase-change memory materials. (orig.)

  9. O louco de rua visto através da literatura

    Directory of Open Access Journals (Sweden)

    Ferraz Flávio Carvalho

    2000-01-01

    Full Text Available O artigo procura formular uma teoria acerca do papel do chamado "louco de rua" no imaginário popular, através da apreensão do lugar por ele ocupado em sua comunidade. A compreensão de "loucura" aqui levada em conta baseou-se no pensamento de Foucault, que a vê como fenômeno determinado historicamente e divide as formas de sua concepção no decorrer da história entre as modalidades trágica e crítica, a primeira antecedendo o advento da psiquiatria. O material foi obtido na narrativa literária (em poesia e prosa de uma série de escritores brasileiros e, através de sua análise, buscou-se apreender as características das relações que se travam entre o louco de rua e a comunidade no espaço do teatro do mundo e detectar-se a maneira como o convívio com o louco toca o imaginário popular e produz efeitos.

  10. Epi-cleaning of Ge/GeSn heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Di Gaspare, L.; Sabbagh, D.; De Seta, M.; Sodo, A. [Dipartimento di Scienze, Università Roma Tre, Viale Marconi 446, 00146 Rome (Italy); Wirths, S.; Buca, D. [Peter Grünberg Institute 9 and JARA-Fundamentals of Future Information Technologies, Forschungszentrum Juelich, Juelich 52425 (Germany); Zaumseil, P. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); BTU Cottbus, Konrad-Zuse Str. 1, 03046 Cottbus (Germany); Capellini, G., E-mail: capellini@ihp-microelectronics.com [Dipartimento di Scienze, Università Roma Tre, Viale Marconi 446, 00146 Rome (Italy); IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany)

    2015-01-28

    We demonstrate a very-low temperature cleaning technique based on atomic hydrogen irradiation for highly (1%) tensile strained Ge epilayers grown on metastable, partially strain relaxed GeSn buffer layers. Atomic hydrogen is obtained by catalytic cracking of hydrogen gas on a hot tungsten filament in an ultra-high vacuum chamber. X-ray photoemission spectroscopy, reflection high energy electron spectroscopy, atomic force microscopy, secondary ion mass spectroscopy, and micro-Raman showed that an O- and C-free Ge surface was achieved, while maintaining the same roughness and strain condition of the as-deposited sample and without any Sn segregation, at a process temperature in the 100–300 °C range.

  11. Microstructure and electrical properties of Sb2Te phase-change material

    Science.gov (United States)

    Liu, Guangyu; Wu, Liangcai; Li, Tao; Rao, Feng; Song, Sannian; Liu, Bo; Song, Zhitang

    2016-10-01

    Phase Change Memory (PCM) has great potential for commercial applications of next generation non-volatile memory (NVM) due to its high operation speed, high endurance and low power consumption. Sb2Te (ST) is a common phase-change material and has fast crystallization speed, while thermal stability is relatively poor and its crystallization temperature is about 142°C. According to the Arrhenius law, the extrapolated failure temperature is about 55°C for ten years. When heated above the crystallization temperature while below the melting point, its structure can be transformed from amorphous phase to hexagonal phase. Due to the growth-dominated crystallization mechanism, the grain size of ST film is large and the diameter of about 300 nm is too large compared with Ge2Sb2Te5 (GST), which may deteriorate the device performance. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to study the microstructures and the results indicate that the crystal plane is {110}. In addition, device cells were manufactured and their current-voltage (I-V) and resistance-voltage characteristics were tested, and the results reveal that the threshold voltage (Vth) of ST film is 0.87 V. By researching the basic properties of ST, we can understand its disadvantages and manage to improve its performance by doping or other proper methods. Finally, the improved ST can be a candidate for optical discs and PCM.

  12. Growth of single-crystal metastable semiconducting (GaSb)1-xGex films

    Science.gov (United States)

    Cadien, K. C.; Eltoukhy, A. H.; Greene, J. E.

    1981-05-01

    Epitaxial metastable (GaSb)1-xGex alloys with compostions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. An essential feature allowing the growth of these metastable materials was low-energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second-phase precipitates. Annealing experiments indicated that the metastable films exhibit good high-temperature stability and that they transform through a continuous series of GaSb-rich and Ge-rich phases in which the solute concentrations decrease until the equilibrium two-phase alloy is obtained. While the calculated free-energy difference between the single-phase metastable and equilibrium states is ˜18 meV, the measured activation barrier for the transformation is ˜3 eV. All films were p-type with room-temperature hole concentrations varying from 1016 to 1019 cm-3 and mobilities between 10 and 720 cm2/ V s, depending on film composition.

  13. Magneto-transport studies of GaSb/InAs/GaSb double heterostructures Semiconductors

    CERN Document Server

    Takashina, K

    2002-01-01

    The electrical transport properties of GaSb/lnAs/GaSb double-heterostructures are examined experimentally. The structures are studied at low temperatures and high magnetic field. InAs/GaSb is a crossed-gap system where the conduction band minimum of InAs lies lower in energy than the valence band maximum of GaSb. The samples examined exploit this property to contain two-dimensional layers of electrons and holes. A description of the general electrical magneto-transport properties is given. Effects due to anticrossing behaviour between the electron and hole dispersion relations are demonstrated and discussed. It is shown that the anticrossing can lead to a non-monotonic temperature dependence of the resistivity. Under quantum Hall conditions, the system displays two types of behaviour. An insulating behaviour where both Hall and diagonal conductivities become vanishingly small, and a more conventional metallic behaviour where the Hall resistance is quantized and the diagonal resistivity disappears. It is found...

  14. Optical response of confined excitons in GaInAsSb/GaSb Quantum Dots heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Cano, R [Departamento de Fisica, Universidad Autonoma de Occidente, A.A. 2790, Cali (Colombia); Tirado-Mejia, L; Fonthal, G; Ariza-Calderon, H [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 4603 Armenia (Colombia); Porras-Montenegro, N, E-mail: rsanchez40@gmail.co [Departamento de Fisica, Universidad del Valle, A.A. 25360, Cali (Colombia)

    2009-05-01

    The narrow-gap Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y} compounds are suitable materials for heterostructure devices operating in the infrared wavelength range. In these compounds grown by liquid phase epitaxy over GaSb single crystals, for x and y values in the range of 0.10 to 0.14 for both variables, the photoluminescence optical response at 12K is blue-shifted by 20 meV related to the photoreflectance response. We believe this behavior is due to possible higher electronic confinement in some places of the heterostructure, possibly formed in the interface during the growth process. In order to explain this behavior, in this work we study the exciton recombination energy in spherical Quantum Dots (QDs) on Ga{sub 1-x}In{sub x}As{sub y}Sb{sub 1-y}/GaSb, using the variational procedure within the effective-mass approximation and considering an electron in a Type I band alignment formed by two semiconductors with similar parabolic conduction bands. Our results are in good agreement with recent experimental results.

  15. Sb-based IR photodetector epiwafers on 100 mm GaSb substrates manufactured by MBE

    Science.gov (United States)

    Fastenau, Joel M.; Lubyshev, Dmitri; Qiu, Yueming; Liu, Amy W. K.; Koerperick, Edwin J.; Olesberg, Jon T.; Norton, Dennis

    2013-07-01

    Antimony-based materials continue to provide great interest for infrared photodetector and focal plane array imaging applications. Detector architectures include InAs/Ga(In)Sb strained-layer superlattices, which create a type-II band alignment that can be tailored to cover a wide range of the mid- and long-wavelength bands by varying the thickness and composition of the constituent materials, and bulk InAsSb-based XBn barrier designs. These materials can provide desirable detector features such as wider wavelength range, suppression of tunneling currents, improved quantum efficiency, and higher operating temperatures. In order to bring these advantages to market, a reliable manufacturing process must be established on large diameter substrates. We report our latest work on the molecular beam epitaxy growth of Sb-detector epiwafers on 100 mm diameter GaSb substrates in a multi-wafer production format. The growth process has been established to address the challenges of these demanding structures, including the large numbers of alternating thin layers and mixed group-V elements. Various characterization techniques demonstrate excellent surface morphology, crystalline structure quality, and optical properties of the epiwafers. The measured wafer-to-wafer consistency and cross-wafer uniformity demonstrate the potential for volume manufacturing.

  16. V-Ge-Cu system

    Energy Technology Data Exchange (ETDEWEB)

    Savitskij, E.M.; Efimov, Yu.V.; Bodak, O.I.; Kharchenko, O.I.; Shomova, N.A.; Frolova, T.M.

    By the methods of microscopic, X-ray phase analyses, X-ray spectral microanalysis as well as by measurement of Tsub(C) and phase lattice parameters the structure of the vanadium-region of the V-Ge ternary system (up to 40 at.%) - Cu(up to 90 at.%) is studied and isothermal cross section at 800 deg C is plotted. In the studied region solid solutions on the base of vanadium, copper and V/sub 3/Ge and V/sub 5/Ge/sub 3/ compounds are in phase equilibria. The solid solution on the vanadium base in ternary alloys practically does not possess superconductivity at the temperature over 4.2 K. Tsub(C) of V/sub 3/Ge saturated with copper decreases up to 5.3-5.6 K depending on treatment conditions and alloys composition. The superspeed quenching from molten state and the consequent low-temperature tempering of ternary alloys can increase V/sub 3/Ge Tsub(C) up to 6-6.7 K.

  17. Investigation of Cr{sub 0.06}(Sb{sub 4}Te){sub 0.94} alloy for high-speed and high-data-retention phase change random access memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Li, Le [Chinese Academy of Sciences, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Shanghai (China); Graduate School of the Chinese Academy of Sciences, Beijing (China); Song, Sannian; Zhang, Zhonghua; Song, Zhitang; Cheng, Yan; Lv, Shilong; Wu, Liangcai; Liu, Bo; Feng, Songlin [Chinese Academy of Sciences, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Shanghai (China)

    2015-08-15

    The effects of Cr doping on the structural and electrical properties of Cr{sub x} (Sb{sub 4}Te){sub 1-x} materials have been investigated in order to solve the contradiction between thermal stability and fast crystallization speed of Sb{sub 4}Te alloys. Cr{sub 0.06}(Sb{sub 4}Te){sub 0.94} alloy is considered to be a potential candidate for phase change random access memory (PCM), as evidenced by a higher crystallization temperature (204 C), a better data retention ability (137.6 C for 10 years), a lower melting point (558 C), a lower energy consumption, and a faster switching speed in comparison with those of Ge{sub 2}Sb{sub 2}Te{sub 5}. A reversible switching between set and reset states can be realized by an electric pulse as short as 5 ns for Cr{sub 0.06}(Sb{sub 4}Te){sub 0.94}-based PCM cell. In addition, Cr{sub 0.06}(Sb{sub 4}Te){sub 0.94} shows good endurance up to 1.1 x 10 {sup 4} cycles with a resistance ratio of about two orders of magnitude. (orig.)

  18. Electrical Set-Reset Phenomenon in Thallium Doped Ge-Te Glasses Suitable for Phase Change Memory Applications

    Directory of Open Access Journals (Sweden)

    M.M. Rahman

    2011-01-01

    Full Text Available Ge17Te83-xTlx (x = 2, 3, 6, 8, 10 glasses have been prepared by melt quenching method and their amorphous nature was confirmed by XRD spectra. I-V characteristics and repeatability of electrical switching were investigated for all the glasses in order to find out their suitability for phase change memory applications. A comparison has been given with Ge2Sb2Te5 the most commonly used material for phase change memory application. The entire series of glasses exhibited memory type of electrical switching but only the composition Ge17Te81Tl2 was able to withstand SET-RESET pulses for more than 10 cycles. The other samples show repeatability for only a few cycles with the degradation of threshold voltage.

  19. Crystallographic study of the intermediate compounds SbZn, Sb{sub 3}Zn{sub 4} and Sb{sub 2}Zn{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Adjadj, Fouzia [Laboratoire des etudes Physico-chimiques des Materiaux, Departement de Physique, Faculte des Sciences, Universite de Batna, 05000 Batna (Algeria); Belbacha, El-djemai [Laboratoire des etudes Physico-chimiques des Materiaux, Departement de Physique, Faculte des Sciences, Universite de Batna, 05000 Batna (Algeria)]. E-mail: Beldjem@caramail.com; Bouharkat, Malek [Laboratoire des etudes Physico-chimiques des Materiaux, Departement de Physique, Faculte des Sciences, Universite de Batna, 05000 Batna (Algeria); Kerboub, Abdellah [Laboratoire des etudes Physico-chimiques des Materiaux, Departement de Physique, Faculte des Sciences, Universite de Batna, 05000 Batna (Algeria)

    2006-08-10

    The processes of development of semiconductor ceramics made up of bismuth, antimony and zinc often require during their preparation to know the nature of the involved phases. For that, it is always essential to refer to the diagrams of balance between phases of the binary systems or ternary. We presented in this work the study by X-rays diffraction relating to the intermediate compounds SbZn, Sb{sub 3}Zn{sub 4} and Sb{sub 2}Zn{sub 3}. The analysis by X-rays is often useful to give supplement the results of the other experimental methods.

  20. Filled Co (sub X) Ni (sub 4-x) Sb (sub 12-y) Sn (sub Y) Skutterudites: Processing and Thermoelectric Properties

    Science.gov (United States)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2015-01-01

    Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3 or CoAs3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Co (sub X) Ni (sub 4-x) Sb (sub 12-y) Sn (sub Y) system has been investigated as both a p- and n-type thermoelectric material, and is stable up to 200 degrees Centigrade. Yb, Ce, and Dy fillers have been introduced into the skutterudite to study the influence of both the type and the quantity of fillers on processing conditions and thermoelectric properties. The system was processed through a multi-step technique that includes solidification, mechano-chemical alloying, and hot pressing which will be discussed along with thermoelectric transport properties.

  1. Phase equilibria in the La–Mg–Ge system at 500 °C and crystal structure of the new ternary compounds La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    De Negri, S., E-mail: serena.denegri@unige.it [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy); Solokha, P.; Skrobańska, M. [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy); Proserpio, D.M. [Università degli Studi di Milano, Dipartimento di Chimica, Via Golgi 19, 20133 Milano (Italy); Samara Center for Theoretical Materials Science (SCTMS), Samara State University, Samara 443011 (Russian Federation); Saccone, A. [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy)

    2014-10-15

    The whole 500 °C isothermal section of the La–Mg–Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La{sub 2+x}Mg{sub 1−x}Ge{sub 2} (τ{sub 2}, P4/mbm, tP10–Mo{sub 2}FeB{sub 2}, 0≤x≤0.25), La{sub 4}Mg{sub 5}Ge{sub 6} (τ{sub 3}, Cmc2{sub 1}, oS60–Gd{sub 4}Zn{sub 5}Ge{sub 6}) and La{sub 4}Mg{sub 7}Ge{sub 6} (τ{sub 4}, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La{sub 11}Mg{sub 2}Ge{sub 7} (τ{sub 1}, P4{sub 2}/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg{sub 3−x}Ge{sub 2} (τ{sub 5}, P3{sup ¯}1c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La{sub 6}Mg{sub 23}Ge (τ{sub 6}, Fm3{sup ¯}m, cF120–Zr{sub 6}Zn{sub 23}Si, a=1.46694(6) nm), La{sub 4}MgGe{sub 10−x} (τ{sub 7}, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, β=97.16°(1) and La{sub 2}MgGe{sub 6} (τ{sub 8}, Cmce, oS72–Ce{sub 2}(Ga{sub 0.1}Ge{sub 0.9}){sub 7}, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La–Mg–Ge phases in terms of partially occupied sites. The crystal structures of La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2} are discussed in details. The latter is a √3a×√3a×2c superstructure of the LaLi{sub 3}Sb{sub 2} structure type; the symmetry reduction scheme is shown in the Bärnighausen formalism terms. - Graphical abstract: La–Mg–Ge isothermal section at 500 °C and group–subgroup relation between the LaLi{sub 3}Sb{sub 2} (parent type) and LaMg{sub 3−x}Ge{sub 2} (derivative) structures. - Highlights: • Novel La−Mg−Ge compounds structure determination from X-ray single crystal data. • Disordering phenomena as common features of the studied germanides. • Bärnighausen formalism as a useful tool for accurate structure determination. • Full isothermal section of the La–Mg–Ge

  2. Band calculation of lonsdaleite Ge

    Science.gov (United States)

    Chen, Pin-Shiang; Fan, Sheng-Ting; Lan, Huang-Siang; Liu, Chee Wee

    2017-01-01

    The band structure of Ge in the lonsdaleite phase is calculated using first principles. Lonsdaleite Ge has a direct band gap at the Γ point. For the conduction band, the Γ valley is anisotropic with the low transverse effective mass on the hexagonal plane and the large longitudinal effective mass along the c axis. For the valence band, both heavy-hole and light-hole effective masses are anisotropic at the Γ point. The in-plane electron effective mass also becomes anisotropic under uniaxial tensile strain. The strain response of the heavy-hole mass is opposite to the light hole.

  3. Thermodynamic modeling of the Au-Sb-Si ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J., E-mail: jiang.wang@empa.ch [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining and Interface Technology, Uberlandstrasse 129, Duebendorf, Zuerich CH-8600 (Switzerland); Liu, Y.J. [Western Transportation Institute, Montana State University, Bozeman, MT 59715 (United States); Liu, L.B. [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Zhou, H.Y. [School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin, Guangxi 541004 (China); Jin, Z.P. [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China)

    2011-02-10

    Research highlights: > Thermodynamic optimization of the Au-Sb binary system was updated. > The Si-Sb binary system was assessed from critical review of experimental information. > Thermodynamic modeling of the Au-Sb-Si ternary system was performed. > The phase relations of this ternary system are useful to design Au-based solders. - Abstract: Thermodynamic optimization of the Au-Sb binary system was updated as well as the Si-Sb binary system was assessed thermodynamically using the CALPHAD method based on the critical review of the available experimental information from the published literature. The solution phases including liquid, fcc{sub A}1(Au), diamond{sub A}4(Si) and rhombohedral{sub A}7(Sb), are modeled as substitutional solutions and their excess Gibbs energies are expressed by a Redlich-Kister polynomial. The solubility of Si in the intermetallic compound AuSb{sub 2} is not taken into account because of the lack of experimental information. Combined with previous assessment of the Au-Si binary system, thermodynamic modeling of the Au-Sb-Si ternary system was performed to reproduce well the measured phase equilibria. The liquidus projection and several vertical sections of this ternary system were calculated, which are in reasonable agreement with the reported experimental data.

  4. Memristive Switching in Bi(1-x)Sb(x) Nanowires.

    Science.gov (United States)

    Han, Nalae; Park, Myung Uk; Yoo, Kyung-Hwa

    2016-04-13

    We investigated the memristive switching behavior in bismuth-antimony alloy (Bi(1-x)Sb(x)) single nanowire devices at 0.1 ≤ x ≤ 0.42. At 0.15 ≤ x ≤ 0.42, most Bi(1-x)Sb(x) single nanowire devices exhibited bipolar resistive switching (RS) behavior with on/off ratios of approximately 10(4) and narrow variations in switching parameters. Moreover, the resistance values in the low-resistance state (LRS) were insensitive to x. On the other hand, at 0.1 ≤ x ≤ 0.15, some Bi(1-x)Sb(x) single nanowire devices showed complementary RS-like behavior, which was ascribed to asymmetric contact properties. Transmission electron microscopy and elemental mapping images of Bi, Sb, and O obtained from the cross sections of the Bi(1-x)Sb(x) single nanowire devices, which were cut before and after RS, revealed that the mobile species was Sb ions, and the migration of the Sb ions to the nanowire surface brought the switch to LRS. In addition, we demonstrated that two types of synaptic plasticity, namely, short-term plasticity and long-term potentiation, could be implemented in Bi(1-x)Sb(x) nanowires by applying a sequence of voltage pulses with different repetition intervals.

  5. Reduction of [Cp*Sb]4 with Subvalent Main-Group Metal Reductants: Syntheses and Structures of [(L(1) Mg)4 (Sb4 )] and [(L(2) Ga)2 (Sb4 )] Containing Edge-Missing Sb4 Units.

    Science.gov (United States)

    Ganesamoorthy, Chelladurai; Krüger, Julia; Wölper, Christoph; Nizovtsev, Anton S; Schulz, Stephan

    2017-02-16

    [Cp*Sb]4 (Cp*=C5 Me5 ) reacts with [L(1) Mg]2 and L(2) Ga with formation of [(L(1) Mg)4 (μ4 ,η(1:2:2:2) -Sb4 )] (L(1) =iPr2 NC[N(2,6-iPr2 C6 H3 )]2 , 1) and [(L(2) Ga)2 (μ,η(2:2) -Sb4 )] (L(2) =HC[C(Me)N(2,6-iPr2 C6 H3 )]2 , 2). The cleavage of the Sb-Sb and Sb-C bonds in [Cp*Sb]4 are the crucial steps in both reactions. The formation of 1 occurred by elimination of the Cp* anion and formation of Cp*MgL(1) , while 2 was formed by reductive elimination of Cp*2 and oxidative addition of L(2) Ga to the Sb4 unit. 1 and 2 were characterized by heteronuclear NMR spectroscopy and single-crystal X-ray diffraction, and their bonding situation was studied by quantum chemical calculations.

  6. GaAs/GaSb nanowire heterostructures grown by MOVPE

    DEFF Research Database (Denmark)

    Jeppsson, Mattias; Dick, Kimberly A.; Wagner, Jakob Birkedal

    2008-01-01

    We report Au-assisted growth of GaAs/GaSb nanowire heterostructures on GaAs(1 1 1)B-substrates by metal-organic vapor phase epitaxy. The growth is studied at various precursor molar fractions and temperatures, in order to optimize the growth conditions for the GaSb nanowire segment. In contrast t...

  7. Demonstration of a Ge/GeSn/Ge quantum-well microdisk resonator on silicon: enabling high-quality Ge(Sn) materials for micro- and nanophotonics.

    Science.gov (United States)

    Chen, Robert; Gupta, Suyog; Huang, Yi-Chiau; Huo, Yijie; Rudy, Charles W; Sanchez, Errol; Kim, Yihwan; Kamins, Theodore I; Saraswat, Krishna C; Harris, James S

    2014-01-08

    We theoretically study and experimentally demonstrate a pseudomorphic Ge/Ge0.92Sn0.08/Ge quantum-well microdisk resonator on Ge/Si (001) as a route toward a compact GeSn-based laser on silicon. The structure theoretically exhibits many electronic and optical advantages in laser design, and microdisk resonators using these structures can be precisely fabricated away from highly defective regions in the Ge buffer using a novel etch-stop process. Photoluminescence measurements on 2.7 μm diameter microdisks reveal sharp whispering-gallery-mode resonances (Q > 340) with strong luminescence.

  8. Thermally induced native defect transform in annealed GaSb

    Science.gov (United States)

    Jie, Su; Tong, Liu; Jing-Ming, Liu; Jun, Yang; Yong-Biao, Bai; Gui-Ying, Shen; Zhi-Yuan, Dong; Fang-Fang, Wang; You-Wen, Zhao

    2016-07-01

    Undoped p-type GaSb single crystals were annealed at 550-600 °C for 100 h in ambient antimony. The annealed GaSb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy (GDMS), infrared (IR) optical transmission and photoluminescence (PL) spectroscopy. Compared with the as-grown GaSb single crystal, the annealed GaSb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the GaSb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 61474104 and 61504131).

  9. In vitro effects of SB202190 on Echinococcus granulosus.

    Science.gov (United States)

    Lv, Hailong; Li, Siyuan; Zhang, Jing; Liang, Weihua; Mu, Xiaoling; Jiang, Yufeng

    2013-04-01

    Spillage of cyst contents during surgical operation is the major cause of recurrence after hydatid cyst surgery. Instillation of a scolicidal agent into a hepatic hydatid cyst is the most commonly employed measure to prevent this complication. SB202190 is a pyridinyl imidazole derivative and is known to be a specific inhibitor of p38 MAPK. In the present study, the scolicidal effect of SB202190 was investigated. Freshly isolated Echinococcus granulosus protoscolices were subjected to SB202190 treatment (10, 20, 40, and 80 µM), and the effects on parasite viability were monitored by trypan blue staining. Corresponding effects were visualized by scanning and transmission electron microscopy. Dose-dependent protoscolex death within a few days of SB202190 treatment was observed. Although the in vitro scolicidal effect of SB202190 was satisfactory, the in vivo efficacy of this drug and also possible side effects remain to be further investigated.

  10. Ferromagnetism in Mn-doped Sb(2)Te.

    Science.gov (United States)

    Luo, H; Gibson, Q; Krizan, J; Cava, R J

    2014-05-21

    We report that Sb2Te, a natural superlattice phase consisting of two elemental Sb2 layers interleaved with single Sb2Te3 layers, becomes ferromagnetic at low temperatures on doping with small percentages of Mn. Ferromagnetism appears for Mn concentrations as low as Sb1.98Mn0.02Te, where a ferromagnetic Tc of ~8.6 K is observed. Tc decreases with increasing Mn content in the stoichiometric materials but increases with increasing Te excess in materials of the type Sb1.93-yMn0.07Te1+y, starting at ~3 K at y = 0 and reaching a Tc of ~8.9 K at y = 0.06.

  11. Phenotypic stability via ammi model with bootstrap re-sampling Estabilidade fenotípica através da reamostragem “bootstrap” no modelo AMMI

    Directory of Open Access Journals (Sweden)

    Osmir José Lavoranti

    2010-06-01

    se quantificar os escores como baixos, considerando estável os genótipos e/ou ambientes, além de não apresentar o padrão de resposta do genótipo, o que caracteriza os padrões de adaptabilidade, mostram-se como os principais pontos negativos. Visando minimizar esses problemas desenvolveu-se uma metodologia via reamostragem "bootstrap", no modelo AMMI. Foram analisadas 20 progênies de Eucalyptus grandis, procedentes da Austrália, e implantadas em sete testes de progênies nas regiões Sul e Sudeste do Brasil, sendo a interação GE significativa (valor p<0,001. A metodologia "bootstrap" AMMI eliminou as dúvidas relacionadas e mostrou-se precisa e confiável. O coeficiente "bootstrap" de estabilidade (CBE, baseado na distância quadrada de Mahalanobis, obtidos através da região de predição para o vetor nulo, mostrou-se adequado para predições das estabilidades fenotípicas.

  12. Thermodynamic Assessments of Ternary Ga-As-P,Ga-P-Sb,In-As-P and In-P-Sb Systems

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The experimental phase diagram data of the Ga-As-P,Ga-P-Sb,In-As-P and In-P-Sb ternary systems were critically assessed. A set of self-consistent thermodynamic model parameters were obtained and used to describe the phase equilibria of these systems. In most cases, the calculated values agree very well with the experimental data.

  13. Aprendizagem Infantil através do Construtivismo: ensinar e aprender

    Directory of Open Access Journals (Sweden)

    Nathalia Cunha Polese

    2012-05-01

    Full Text Available A partir da temática, “a aprendizagem infantil através do construtivismo”, objetiva-se compreender as formas que as crianças aprendem e como os professores constroem essa aprendizagem. Também, tem como meta desmistificar o que se entende como construtivismo e esclarecer o que realmente é essa forma de ensinar e aprender como o professor deve trabalhar a partir desse referencial teórico. Será abordada as fases de desenvolvimento motor, verbal e mental; a aquisição da base alfabética. Que conteúdos o professor deve contemplar na Educação Infantil e o papel que ele tem na aprendizagem das crianças. Tendo como principais aparatos teóricos: Teberosky, Ferreiro, Bassedas, Piaget, as escolas de Reggio Emilia e o documento Referencial Curricular para a Educação Infantil.

  14. Fisiologia do transporte de fluidos e solutos atraves da membrana peritoneal

    Directory of Open Access Journals (Sweden)

    Anna Rita Aguirre

    2014-03-01

    Full Text Available Nesta revisão, são explicados os fenômenos envolvidos nas trocas de fluidos e solutos através da membrana peritoneal, tanto na situação fisiológica quanto no contexto da diálise peritoneal. Para tanto, são utilizados os modelos matemáticos desenvolvidos para estudo do transporte pela membrana, tais como o "Modelo de Poros" e o "Modelo Distributivo". Os ganhos científicos com as pesquisas nesse campo são contemplados e as áreas que merecem pesquisas adicionais também são citadas. Assim, o estado atual do conhecimento fisiológico a respeito dessa modalidade de terapia renal substitutiva, no que se refere aos eventos relacionados à membrana peritoneal, encontra-se sintetizado nesse manuscrito.

  15. Ler o mundo: um olhar através da simiótica social

    Directory of Open Access Journals (Sweden)

    Maria Alice Andrade de Souza Descardeci

    2002-01-01

    Full Text Available O presente artigo questiona os pressupostos com os quais a escola brasileira trabalha o conceito de leitura, que impõe ao aluno a modalidade escrita como sendo a única, ou mais relevante, forma de representação para composição de mensagens impressas. A leitura do mundo, na concepção da escola atual, faz-se através da leitura do código escrito. Tal questionamento é feito através da teoria da semiótica social (Kress e van Leeuwen, 1996. De acordo com essa teoria, textos são construtos multi-modais; dos quais a escrita é apenas um dos modos de representação da mensagem. Estes, por sua vez, são culturalmente determinados e constantemente redefinidos dentro dos grupos sociais nos quais significam. Uma análise de impressos coletados em um ambiente de trabalho é apresentada para demonstrar a multimodalidade das formas de representação, que deve ser considerada quando do ensino da leitura da palavra, para uma leitura mais significativa do mundo. This paper questions today’s Brazilian schools’ theoretical approach to reading, which imposes to pupils reading the written code as the only relevant form of representation in texts. Reading the world, according to the schools’ conception, happens as reading the written code does. The social semiotics theory (Kress and van Leeuwen, 1996 is used in the article to argue against it. According to this theory, texts are multi-modal constructs; and forms of representation are culturally determined and constantly re-defined within the social groups where they have meaning. An analysis of printed materials collected inside a workplace is presented to show the multimodality of forms of representation defended by the theory in case. Multimodality has to be considered when teaching reading the words that leads to reading the world.

  16. Neutron transmutation doped Ge bolometers

    Science.gov (United States)

    Haller, E. E.; Kreysa, E.; Palaio, N. P.; Richards, P. L.; Rodder, M.

    1983-01-01

    Some conclusions reached are as follow. Neutron Transmutation Doping (NTD) of high quality Ge single crystals provides perfect control of doping concentration and uniformity. The resistivity can be tailored to any given bolometer operating temperature down to 0.1 K and probably lower. The excellent uniformity is advantaged for detector array development.

  17. Controle de velocidade de motor de indução trifasico alimentado por inversor PWM atraves de microcomputador

    OpenAIRE

    Ivo Reis Fontes

    1993-01-01

    Resumo: Encontra-se em desenvolvimento no Laboratório de Engenharia de Computação e Automação Industrial (LCA) um protótipo de veículo elétrico autoguiado (AGV) com controle através de computador. Os AGVs encontram diversas aplicações dentro do ambiente industrial automatizado, pela possibilidade que os mesmos oferecem em receber controle de um computador supervisor, através de sistemas de comunicações, a fun de realizar a várias tarefas envolvidas no processo produtivo. Sua aplicação também ...

  18. Investigation of the superconducting and normal state properties of the filled-skutterudite system PrPt4Ge12 via chemical substitution

    Science.gov (United States)

    Jeon, Inho; Huang, Kevin; Yazici, Duygu; Kanchanavatee, Noravee; White, Benjamin D.; Jang, Sooyoung; Pouse, Naveen; Maple, M. Brian; Ho, Pei-Chun

    We report a systematic chemical substitution study on the unconventional superconductor system PrPt4Ge12, which Sb ions are substituted for Ge. Polycrystalline samples of PrPt4Ge12-x Sbx up to x = 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitutions and evidence for a weak ``rattling'' mode associated with the Pr ions, characterized by a value of ΘE ~ 60 K. As part of a systematic study of the effect of various elemental substitutions on the properties of PrPt4Ge12, measurements of the superconducting and normal state properties of the Pr1-xEuxPt4Ge12 system are currently being performed. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-04-ER46105 (characterization and physical properties measurements), and the National Science Foundation under Grant No. DMR 1206553 (low-temperature measurements).

  19. Synthesis, crystal structure, and transport properties of Fe substituted rhombohedral skutterudite derivatives Co4−xFexGe6Se6

    KAUST Repository

    Wei, Kaya

    2014-11-01

    We report on the synthesis and low temperature transport properties of rhombohedral derivatives of the cubic skutterudite CoSb3, namely Co4-xFexGe6Se6 with x = 0, 1, 1.5. Rietveld refinement and elemental analyses were used to identify the structure and stoichiometry of the compositions. The thermal conductivity was investigated by employing the Debye model with different phonon-scattering parameters. This investigation demonstrates that Fe substitution is feasible in these skutterudite derivatives and can significantly affect the transport properties as compared with Co4Ge6Se6. © 2014 Elsevier B.V. All rights reserved.

  20. Optical transitions in strained InAsSb/GaInSb interband QC lasers

    Institute of Scientific and Technical Information of China (English)

    Ligong Yang(杨立功); Peifu Gu(顾培夫); Xiaoyun Qin(秦小芸)

    2004-01-01

    @@ In this paper a detailed simulation and theoretical analysis based on model-solid theory and the(→κ)·(→ρ)methodare presented to investigate the dependence of the band structure on the strain deformation in a noveltype-Ⅱ quantum well(QW)heterostructure InAs1_ySby/GaxIn1-xSb under the uniaxial approximation,and subsequently the optical transition and the gain in the interband cascade lasers containing it havebeen evaluated with unchanged injection current densities.The simulation results show that the straineffect on the transition in this heterostructure will not behave as a simple monotonic trend with the latticemismatch of InAs1_ySby/GaxIn1_xSb interface,but as a function of the complex strain chain includingthe whole active region.It is important to the subsequent device design and optimization.

  1. InSb thin films grown by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: joginderchauhan82@gmail.com; Rajaram, P., E-mail: joginderchauhan82@gmail.com [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2014-04-24

    We have grown InSb thin films on Cu substrates using the electrodeposition technique. The electrochemical bath from which the InSb thin films were grown was made up of a mixture of aqueous solutions of 0.05 M InCl{sub 3} and 0.03M SbCl{sub 3}, 0 .20M citric acid and 0.30M sodium citrate. Citric acid and sodium citrate were used as complexing agents to bring the reduction potential of In and Sb closer to maintain binary growth. The electrodeposited films were characterized by structural, morphological and optical studies. X-ray diffraction studies show that the films are polycrystalline InSb having the zinc blende structure. Scanning electron microscopy (SEM) studies reveal that the surface of the films is uniformly covered with submicron sized spherical particles. FTIR spectra of InSb thin films show a sharp absorption peak at wave number 1022 cm{sup −1} corresponding to the band gap. Hot probe analysis shows that the InSb thin films have p type conductivity.

  2. Superconductivity in novel Ge-based skutterudites: {Sr,Ba}pt4Ge12.

    Science.gov (United States)

    Bauer, E; Grytsiv, A; Chen, Xing-Qiu; Melnychenko-Koblyuk, N; Hilscher, G; Kaldarar, H; Michor, H; Royanian, E; Giester, G; Rotter, M; Podloucky, R; Rogl, P

    2007-11-23

    Combining experiments and ab initio models we report on SrPt4Ge12 and BaPt4Ge12 as members of a novel class of superconducting skutterudites, where Sr or Ba atoms stabilize a framework entirely formed by Ge atoms. Below T(c)=5.35 and 5.10 K for BaPt4Ge12 and SrPt4Ge12, respectively, electron-phonon coupled superconductivity emerges, ascribed to intrinsic features of the Pt-Ge framework, where Ge-p states dominate the electronic structure at the Fermi energy.

  3. Evolution of Ge and SiGe Quantum Dots under Excimer Laser Annealing

    Institute of Scientific and Technical Information of China (English)

    HAN Gen-Quan; ZENG Yu-Gang; YU Jin-Zhong; CHENG Bu-Wen; YANG Hai-Tao

    2008-01-01

    We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing.Inyestigation of the coarsening and relaxation of the dots showS that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer,while the SiGe dots on Si0.77 Ge0.23film relax by lattice distortion to coherent dots which results from the obvious interface between the SiGe dots and the Si0.77Ge0.23 film.The results are suggested and sustained by Vanderbilt and Wickham's theory,and also demonstrate that no bulk diffusion Occurs during the excimer laser annealing.

  4. Understanding and engineering of NiGe/Ge junction formed by phosphorus ion implantation after germanidation

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Hiroshi, E-mail: oka@asf.mls.eng.osaka-u.ac.jp; Minoura, Yuya; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji [Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2014-08-11

    Modulation of the effective electron Schottky barrier height (eSBH) of NiGe/Ge contacts induced by phosphorus ion implantation after germanide formation was investigated by considering local inhomogeneity in the eSBH. Systematic studies of NiGe/Ge contact devices having various germanide thicknesses and ion implantation areas indicated the threshold dopant concentration at the NiGe/Ge interface required for eSBH modulation and negligible dopant diffusion even at NiGe/Ge interface during drive-in annealing, leading to variation in the eSBH between the bottom and sidewall portions of the NiGe regions. Consequently, this method makes it possible to design source/drain contacts with low-resistivity Ohmic and ideal rectifying characteristics for future Ge-based transistors.

  5. Sb-doped PbTe: An NMR Perspective

    Science.gov (United States)

    Levin, E. M.; Schmidt-Rohr, K.; Jaworski, C. M.; Heremans, J. P.

    2010-03-01

    In PbTe, Sb as a dopant can occupy either Pb or Te sites. To understand the effect of Sb on the local charge-carrier concentration in both cases, we have studied high-resolution ^125Te and ^207Pb NMR spectra of Pb1-xSbxTe, PbSbxTe1-x, and n- and p-type PbTe samples. The spectra of Pb0.9975Sb0.0025Te and PbSb0.0025Te0.9975 have distinctly different resonance frequencies due to Knight shifts and chemical shifts produced by Sb at Pb or Te sites. Pb0.9975Sb0.0025Te is n-type while in PbSb0.0025Te0.9975 both n- and p-type are found. NMR spectra and spin-lattice T1 relaxation of ^207Pb nuclei in PbSb0.0025Te0.9975, which are sensitive to the hyperfine interaction between charge carriers and NMR nuclei, reveal at least four components, which reflect electronic inhomogeneity of the sample. The local carrier concentrations estimated from T1 NMR varies from n<3x10^17 to p˜10^19 cm-3. These multiple components help rationalize the complex temperature dependence of the thermopower of PbSb0.0025Te0.9975. However, comparison with Hall and Seebeck effects data indicates that some NMR signals are due to localized electron states, which do not directly contribute to transport.

  6. Solid-Phase Equilibria in the Au-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries.

    Science.gov (United States)

    1986-02-28

    AD6i5 469 SOLID- PHASE EQUILIBRIA IN THE Ru-As AU-GA-SB AU-IN-AS- 1/17 AND AU-IN-SB TERNAR (U) CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND...REPORT & PERIOD COVERED SOLID- PHASE EQUILIBRIA IN THE Au-Ga-As, Au-Ga-Sb Thchnical Report Au-In-As, and Au-In-Sb TEARIEIS S. PERFORMING ORG. REPORT NUMBER...CLASSIFICATION OF THIS PAGEMI*n Does Entepd) 4./ lie- . .- - - - - -- -- Solid Phase Equilibria in the Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries C

  7. Effect of aqueous Fe(II) on Sb(V) sorption on soil and goethite.

    Science.gov (United States)

    Fan, Jian-Xin; Wang, Yu-Jun; Fan, Ting-Ting; Dang, Fei; Zhou, Dong-Mei

    2016-03-01

    The effects of Fe(II) on the sorption and precipitation of Sb(V) on soils and goethite were investigated using batch experiments and X-ray photoelectron spectroscopy (XPS) in this study. The sorption capacity of Sb(V) were much higher in anoxic soil than oxic soil. Typically, dissolved Fe(II) concentration in anoxic soils decreased significantly with increasing Sb(V), which may be suggestive of Fe-Sb precipitation. The elevated concentrations of Fe(II) (1 mM) enhanced the sorption capacity of Sb(V) on goethite significantly. However, synchrotron radiation X-ray diffraction showed no new characteristic peak, indicating that this Fe-Sb precipitate might be poor crystallinity or amorphous. Moreover, Sb(III) was detected in anoxic soil, and the reduction of Sb(V) to Sb (III) improved the sorption capacity of Sb in anoxic soil because of the low solubility and migration of Sb(III). Nevertheless, Fe-Sb co-precipitation and Sb(V) reduction to Sb(III) might contribute simultaneously to the increased sorption capacity of Sb(V) on anoxic soils. This research could improve our current understanding of soil Sb chemistry in paddy and wetland soils.

  8. Investigations on MnSb and related compounds with b8-type structures

    NARCIS (Netherlands)

    Bouwma, Jakob

    1972-01-01

    This thesis describes investigations on phases with hexagonal B8-type structures in the systems Mn-Sb-Sn, Mn-Sb-Te, Mn-Cr-Sb and Mn-V-Sb. In -chapter 1 some general remarks are made on compounds with B8-type structures. The preparation of the samples, and the X-ray crystallographic investigations

  9. Fast reversible laser-induced crystallization of Sb-rich Zn-Sb-Se phase change material with excellent stability

    Directory of Open Access Journals (Sweden)

    Yimin Chen

    2015-07-01

    Full Text Available We present a new reversible phase-change medium Sb-rich Zn-Sb-Se film, which possesses a large difference in both optical and electrical constant. The doped-ZnSb, sub-formed Zn-Se, and exhausted Sb-Se3/2 co-influence the physical properties. Typically, there is ∼105 resistance ratio and ∼14% relative reflectivity change in Zn19Sb45.7Se35.3 film when switched by electricity or laser pulses between amorphous and crystalline states. The higher Tc (∼250°C, larger Ea (∼8.57eV, better 10-yr data retention (∼200.2°C, higher crystallization resistance (∼3 × 103Ω/□ at 300°C-annealled and relative lower melting temperature (∼550.2°C are exhibited in Zn19Sb45.7Se35.3 film. Importantly, a short crystalline time (∼80ns at 70mW of the ideal Zn19Sb45.7Se35.3 film can be obtained without sacrificing room-temperature stability.

  10. Band-inverted gaps in InAs/GaSb and GaSb/InAs core-shell nanowires

    Science.gov (United States)

    Luo, Ning; Huang, Guang-Yao; Liao, Gaohua; Ye, Lin-Hui; Xu, H. Q.

    2016-12-01

    The [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires have been studied by the 8 × 8 Luttinger-Kohn Hamiltonian to search for non-vanishing fundamental gaps between inverted electron and hole bands. We focus on the variations of the band-inverted fundamental gap, the hybridization gap, and the effective gap with the core radius and shell thickness of the nanowires. The evolutions of all the energy gaps with the structural parameters are shown to be dominantly governed by the effect of quantum confinement. With a fixed core radius, a band-inverted fundamental gap exists only at intermediate shell thicknesses. The maximum band-inverted gap found is ~4.4 meV for GaSb/InAs and ~3.5 meV for InAs/GaSb core-shell nanowires, and for the GaSb/InAs core-shell nanowires the gap persists over a wider range of geometrical parameters. The intrinsic reason for these differences between the two types of nanowires is that in the shell the electron-like states of InAs is more delocalized than the hole-like state of GaSb, while in the core the hole-like state of GaSb is more delocalized than the electron-like state of InAs, and both favor a stronger electron-hole hybridization.

  11. Germanium-tin interdiffusion in strained Ge/GeSn multiple-quantum-well structure

    Science.gov (United States)

    Wang, Wei; Dong, Yuan; Zhou, Qian; Tok, Eng Soon; Yeo, Yee-Chia

    2016-06-01

    The thermal stability and germanium-tin (Ge-Sn) interdiffusion properties were studied in epitaxial Ge/GeSn multiple-quantum-well (MQW) structure. No obvious interdiffusion was observed for annealing temperatures of 300 °C or below, while observable interdiffusion occurred for annealing temperatures of 380 °C and above. High-resolution x-ray diffraction was used to obtain the interdiffusion coefficient by analyzing the decrease rate of Ge/GeSn periodic satellite peaks. The interdiffusion coefficient is much higher, and the activation enthalpy of 1.21 eV is substantially lower in Ge/GeSn MQW structure than that previously reported in silicon-germanium (Si-Ge) systems. When the annealing temperature is increased to above 500 °C, Ge-Sn interdiffusion becomes severe. Some small pits appear on the surface, which should be related to Sn out-diffusion to the Ge cap layer, followed by Sn desorption from the top surface. This work provides insights into the Ge-Sn interdiffusion and Sn segregation behaviors in Ge/GeSn MQW structure, and the thermal budget that may be used for fabrication of devices comprising Ge/GeSn heterostructures.

  12. SPEIR: A Ge Compton Camera

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, L; Vetter, K M; Burks, M T; Hull, E L; Craig, W W

    2004-02-11

    The SPEctroscopic Imager for {gamma}-Rays (SPEIR) is a new concept of a compact {gamma}-ray imaging system of high efficiency and spectroscopic resolution with a 4-{pi} field-of-view. The system behind this concept employs double-sided segmented planar Ge detectors accompanied by the use of list-mode photon reconstruction methods to create a sensitive, compact Compton scatter camera.

  13. Behavior of GaSb (100) and InSb (100) surfaces in the presence of H2O2 in acidic and basic cleaning solutions

    Science.gov (United States)

    Seo, Dongwan; Na, Jihoon; Lee, Seunghyo; Lim, Sangwoo

    2017-03-01

    Gallium antimonide (GaSb) and indium antimonide (InSb) have attracted strong attention as new channel materials for transistors due to their excellent electrical properties and lattice matches with various group III-V compound semiconductors. In this study, the surface behavior of GaSb (100) and InSb (100) was investigated and compared in hydrochloric acid/hydrogen peroxide mixture (HPM) and ammonium hydroxide/hydrogen peroxide mixture (APM) solutions. In the acidic HPM solution, surface oxidation was greater and the etching rates of the GaSb and InSb surfaces increased when the solution is concentrated, which indicates that H2O2 plays a key role in the surface oxidation of GaSb and InSb in acidic HPM solution. However, the GaSb and InSb surfaces were hardly oxidized in basic APM solution in the presence of H2O2 because gallium and indium are in the thermodynamically stable forms of H2GaO3- and InO2-, respectively. When the APM solution was diluted, however, the Ga on the GaSb surface was oxidized by H2O, increasing the etching rate. However, the effect of dilution of the APM solution on the oxidation of the InSb surface was minimal; thus, the InSb surface was less oxidized than the GaSb surface and the change in the etching rate of InSb with dilution of the APM solution was not significant. Additionally, the oxidation behavior of gallium and indium was more sensitive to the composition of the HPM and APM solutions than that of antimony. Therefore, the surface properties and etching characteristics of GaSb and InSb in HPM and APM solutions are mainly dependent on the behavior of the group III elements rather than the group V elements.

  14. Study of conformational changes and protein aggregation of bovine serum albumin in presence of Sb(III) and Sb(V).

    Science.gov (United States)

    Verdugo, Marcelo; Ruiz Encinar, Jorge; Costa-Fernández, José Manuel; Menendez-Miranda, Mario; Bouzas-Ramos, Diego; Bravo, Manuel; Quiroz, Waldo

    2017-01-01

    Antimony is a metalloid that affects biological functions in humans due to a mechanism still not understood. There is no doubt that the toxicity and physicochemical properties of Sb are strongly related with its chemical state. In this paper, the interaction between Sb(III) and Sb(V) with bovine serum albumin (BSA) was investigated in vitro by fluorescence spectroscopy, and circular dichroism (CD) under simulated physiological conditions. Moreover, the coupling of the separation technique, asymmetric flow field-flow fractionation, with elemental mass spectrometry to understand the interaction of Sb(V) and Sb(III) with the BSA was also used. Our results showed a different behaviour of Sb(III) vs. Sb(V) regarding their effects on the interaction with the BSA. The effects in terms of protein aggregates and conformational changes were higher in the presence of Sb(III) compared to Sb(V) which may explain the differences in toxicity between both Sb species in vivo. Obtained results demonstrated the protective effect of GSH that modifies the degree of interaction between the Sb species with BSA. Interestingly, in our experiments it was possible to detect an interaction between BSA and Sb species, which may be related with the presence of labile complex between the Sb and a protein for the first time.

  15. The crystal structure of ferdowsiite Ag8Sb4(As,Sb)4S16 and its relations to other ABX2 (A=Ag; B=As,Sb,Bi; X=S,Se) structures

    DEFF Research Database (Denmark)

    Makovicky, Emil; Topa, Dan

    2014-01-01

    of ferdowsiite, approximately Ag8Sb4(As,Sb)4S16, contains four distinct cation and four different anion sites in the asymmetric unit, all in general positions. Besides two Ag sites and one Sb site, the crystal structure contains one mixed As-Sb coordination polyhedron (0.63 As and 0.37 Sb in the site). The Sb1...... site has three short Sb-S bonds 2.503–2.645 Å. As and Sb in the mixed site were refined separately, with isotropic displacement coefficients. As has typical bond length values of 2.248–2.354 Å whereas Sb has 2.443–2.392 Å, i.e., the observed ligand positions are visibly influenced by the predominant...... arsenic. The crystal structure of ferdowsiite is a superstructure of a PbS like motif. The {100} planes of the PbS-like substructure are the (105̅), (301) and (010) planes in terms of the ferdowsiite lattice. The structure contains zig-zag chains of Sb1 connected via short Sb-S bonds and flanked by (Sb...

  16. Sb-Mn Alloy in-situ Composites and Magnetic Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructures and magnetic properties of two in-situ composites, directionally solidified Sb-9.5%Mn and Sb-50%Mn alloys, were investigated. The aligned ferromagnetic compound MnSb or Mn2Sb was embedded in Sb or Mn matrix with varying Mn content. The magnetization curves and thermal magnetic curves were examined along solidification direction, which reveals the magnetic behaviors of the composites.

  17. The Cu-Sb-Se phase system at temperatures between 350 and 700 degree C

    DEFF Research Database (Denmark)

    Karup-Møller, Sven

    1999-01-01

    Phase relations were determined in the Cu-Sb-Se phase system at 300o, 400o, 450o, 500o, 600o and 700oC. Five three-component phases are present at 300oC: permingeatite (Cu3SbSe4), phase A (Cu3SbSe3, the Se-equivalent to skinnerite Cu3SbS3), phase B (CuSbSe2, the Se-equivalent to chalcostibite CuS...

  18. Anomalous temperature dependence of the electrical resistivity of molten Sb

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using the d.c. four-probe method, the electrical resistivity of high-purity liquid Sb has been accurately measured as functions of temperature. It is observed that the resistivity of liquid Sb changes abnormally with increasing temperature, which is very different from that of simple liquid metals. Based on the reported structure factor at several temperatures, the results obtained in this work have been discussed and interpreted qualitatively according to Ziman theory. The analysis suggests that the existence of shortrange order structure near the melting point can account for the abnormal phenomenon observed in the resistivity of liquid Sb, in which semimetal-metal transaction takes place in the melting process. At the same time, the progress of the structure change of liquid Sb with temperature has also been pointed out.``

  19. Interstitial-related defect reactions in electron-irradiated oxygen-rich Ge crystals: A DLTS study

    Science.gov (United States)

    Markevich, V. P.; Peaker, A. R.; Lastovskii, S. B.; Murin, L. I.; Litvinov, V. V.; Emtsev, V. V.; Dobaczewski, L.

    2009-12-01

    Electrically active defects induced in oxygen-rich Ge:Sb crystals by irradiation with MeV electrons at 80 or 300 K have been studied by means of capacitance transient techniques. Transformations of the defects upon post-irradiation isochronal anneals have also been investigated. It is argued that a radiation-induced electron trap with an energy level at about 110 meV below the conduction band edge (E110) can be associated with electron emission from an energy level of the Ge self-interstitial (IGe). The E110 trap is eliminated in the temperature range 150-200 K upon 15 min isochronal annealing. No other traps in the upper half of the gap emerge simultaneously with the disappearance of the E110 trap. It is argued that Ge self-interstitials become mobile at temperatures higher than 150 K and in oxygen-rich Ge interact with interstitial oxygen atoms (Oi). The resulting IGeOi complexes do not have energy levels in the upper half of the Ge gap. Diffusion and interaction of the IGeOi defects with interstitial oxygen atoms at T>50 °C result in the formation of IGeO2i complexes. In the most stable configuration the IGeO2i complex has orthorhombic (C2v) symmetry.

  20. The effects of strain on indirect absorption in Ge/SiGe quantum wells

    Science.gov (United States)

    Lever, L.; Ikonić, Z.; Kelsall, R. W.

    2012-06-01

    We calculate the conduction band electron scattering rates from the Γ-valley into the indirect valleys in germanium, and use this to determine the strength of the indirect absorption in Ge/SiGe quantum well heterostructures. This is done as a function of the in-plane compressive strain in the Ge quantum wells, which results from pseudomorphic growth on a SiGe virtual substrate. This compressive strain results in the Δ valleys becoming available as destination states for scattering, which leads to a reduction in the Γ-valley lifetime. We calculate the indirect absorption and lifetime broadening of excitonic peaks, and show that indirect absorption decreases as the Ge fraction in the virtual substrate increases. We conclude that the Ge fraction of the SiGe virtual substrate should be approximately 95% or larger for optimum electroabsorption performance of Ge/SiGe quantum wells.

  1. Photoluminescence from narrow InAs-AlSb quantum wells

    Science.gov (United States)

    Brar, Berinder; Kroemer, Herbert; Ibbetson, James; English, John H.

    1993-01-01

    We report on photoluminescence spectra from narrow InAs-AlSb quantum wells. Strong, clearly resolved peaks for well widths from 2 to 8 monolayers were observed. Transmission electron micrographs show direct evidence for the structural quality of the quantum well structures. The transition energies of the narrowest wells suggest a strong influence of the AlSb X-barrier on the electronic states in the conduction band.

  2. Photomixotrophic growth of Rhodobacter capsulatus SB1003 on ferrous iron

    OpenAIRE

    Kopf, Sebastian H.; Newman, Dianne K.

    2011-01-01

    This study investigates the role iron oxidation plays in the purple non-sulfur bacterium Rhodobacter capsulatus SB1003. This organism is unable to grow photoautotrophically on unchelated ferrous iron [Fe(II)] despite its ability to oxidize chelated Fe(II). This apparent paradox was partly resolved by the discovery that SB1003 can grow photoheterotrophically on the photochemical breakdown products of certain ferric iron–ligand complexes, yet whether it could concomitantly benefit from the oxid...

  3. Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

    Energy Technology Data Exchange (ETDEWEB)

    Liang, J. K.; Su, H. L., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw; Wu, Y. C., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw [School of Materials Science and Engineering and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei University of Technology, Hefei 230009, Anhui (China); Chuang, P. Y.; Kuo, C. L.; Huang, S. Y. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Chan, T. S. [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Huang, J. C. A., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Advanced Optoelectronic Technology Center and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 106, Taiwan (China)

    2015-05-25

    To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (Sb{sub Zn}) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

  4. Development of InAlAsSb growth by MOVPE

    Science.gov (United States)

    Slocum, Michael; Forbes, David V.; Hillier, Glen C.; Smith, Brittany L.; Adams, Jessica G. J.; Hubbard, Seth M.

    2017-08-01

    The growth of InAlAsSb by metal-organic vapor phase epitaxy has been demonstrated, with a controllable antimony fraction exceeding 6%. Calculations have shown that InAlAsSb with Sb contents greater than 5-7% in the quaternary are within the miscibility gap, however this work demonstrates specific growth conditions that allow compositions well within the miscibility gap. From a study of the growth of AlAsSb and an evaluation of two aluminum precursors (TMAl versus TTBAl), growth temperature, and V/III ratio, a foundation is developed to optimize the growth of InAlAsSb. By tailoring V/III ratio, growth conditions were found to achieve high crystalline content of both indium and antimony. InAlAsSb was grown on InP with antimony fractions from 32% to 48%, for which indium fraction varied from 10% to 19%, which provides an expected direct bandgap ranging from 1.75 to 1.98 eV.

  5. Segregation of Ge in B and Ge codoped Czochralski-Si crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Arivanandhan, Mukannan, E-mail: rmarivu@ipc.shizuoka.ac.jp [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Gotoh, Raira; Fujiwara, Kozo; Uda, Satoshi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Hayakawa, Yasuhiro [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan)

    2015-08-05

    Highlights: • Effective segregation of Ge in B and Ge codoped Czochralski-Si crystal growth was analyzed. • The equilibrium segregation coefficient of Ge was calculated. • The experimentally results were analytically analyzed using partitioning theory. - Abstract: The segregation of Ge in B and Ge codoped Czochralski (CZ)-Si crystal growth was investigated. The concentration of Ge in heavily Ge codoped CZ-Si was measured by electron probe micro analysis (EPMA) and X-ray fluorescence spectroscopy. The effective segregation coefficient of Ge (k{sub eff}) was calculated by fitting the EPMA data to the normal freezing equation, and by taking the logarithmic ratio of the Ge concentrations at the seed and tail of the ingots (top to bottom approach). The k{sub eff} of Ge increased from 0.30 to 0.55, when the initial Ge concentration in the Si melt (C{sub L(o)}{sup Ge}) was increased from 3 × 10{sup 19} to 3 × 10{sup 21} cm{sup −3}. To avoid cellular growth, the crystal pulling rate was decreased for heavily Ge codoped crystal growth (C{sub L(o)}{sup Ge} > 3 × 10{sup 20} cm{sup −3}). The equilibrium segregation coefficient (k{sub 0}) of Ge was calculated by partitioning theory, and was smaller than the experimentally estimated k{sub eff}. The variation of k{sub eff} from k{sub 0} was discussed based on Ge clustering in the heavily Ge codoped crystal, which led to changes in the bonding and strain energies caused by the incorporation of Ge into Si.

  6. Role of interlayer coupling for the power factor of CuSbS2 and CuSbSe2

    KAUST Repository

    Alsaleh, Najebah M.

    2017-01-08

    The electronic and transport properties of bulk and monolayer CuSbS2 and CuSbSe2 are determined by using density functional theory and semiclassical Boltzmann transport theory, in order to investigate the role of interlayer coupling for the thermoelectric properties. The calculated band gaps of the bulk compounds are in agreement with experiments and significantly higher than those of the monolayers, which thus show lower Seebeck coefficients. Since also the electrical conductivity is lower, the monolayers are characterized by lower power factors. Therefore, interlayer coupling is found to be essential for the excellent thermoelectric response of CuSbS2 and CuSbSe2, even though it is weak.

  7. Crystal structure, magnetism, {sup 89}Y solid state NMR, and {sup 121}Sb Moessbauer spectroscopic investigations of YIrSb

    Energy Technology Data Exchange (ETDEWEB)

    Benndorf, Christopher [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Heletta, Lukas; Block, Theresa; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institute of Physics in Sao Carlos, University of Sao Paulo, Sao Carlos (Brazil)

    2017-02-15

    The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid-state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single-crystal X-ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR{sub 2} = 0.0455, 535 F{sup 2} values, 20 variables. {sup 89}Y solid state MAS NMR and {sup 121}Sb Moessbauer spectra show single resonance lines in agreement with single-crystal X-ray data. YIrSb is a Pauli paramagnet. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Role of interlayer coupling for the power factor ofCuSbS2andCuSbSe2

    KAUST Repository

    Alsaleh, Najebah M.

    2016-09-26

    The electronic and transport properties of bulk and monolayer CuSbS2 and CuSbSe2 are determined by using density functional theory and semiclassical Boltzmann transport theory, in order to investigate the role of interlayer coupling for the thermoelectric properties. The calculated band gaps of the bulk compounds are in agreement with experiments and significantly higher than those of the monolayers, which thus show lower Seebeck coefficients. Since also the electrical conductivity is lower, the monolayers are characterized by lower power factors. Therefore, interlayer coupling is found to be essential for the excellent thermoelectric response of CuSbS2 and CuSbSe2, even though it is weak.

  9. GeSn/Ge heterostructure short-wave infrared photodetectors on silicon.

    Science.gov (United States)

    Gassenq, A; Gencarelli, F; Van Campenhout, J; Shimura, Y; Loo, R; Narcy, G; Vincent, B; Roelkens, G

    2012-12-03

    A surface-illuminated photoconductive detector based on Ge0.91Sn0.09 quantum wells with Ge barriers grown on a silicon substrate is demonstrated. Photodetection up to 2.2µm is achieved with a responsivity of 0.1 A/W for 5V bias. The spectral absorption characteristics are analyzed as a function of the GeSn/Ge heterostructure parameters. This work demonstrates that GeSn/Ge heterostructures can be used to developed SOI waveguide integrated photodetectors for short-wave infrared applications.

  10. Lattice dynamics in Bi2Te3 and Sb2Te3: Te and Sb density of phonon states

    Science.gov (United States)

    Bessas, D.; Sergueev, I.; Wille, H.-C.; Perßon, J.; Ebling, D.; Hermann, R. P.

    2012-12-01

    The lattice dynamics in Bi2Te3 and Sb2Te3 were investigated both microscopically and macroscopically using 121Sb and 125Te nuclear inelastic scattering, x-ray diffraction, and heat capacity measurements. In combination with earlier inelastic neutron scattering data, the element-specific density of phonon states was obtained for both compounds and phonon polarization analysis was carried out for Bi2Te3. A prominent peak in the Te specific density of phonon states at 13meV, that involves mainly in-plane vibrations, is mostly unaffected upon substitution of Sb with Bi revealing vibrations with essentially Te character. A significant softening is observed for the density of vibrational states of Bi with respect to Sb, consistently with the mass homology relation in the long-wavelength limit. In order to explain the energy mismatch in the optical phonon region, a ˜20% force constant softening of the Sb-Te bond with respect to the Bi-Te bond is required. The reduced average speed of sound at 20K in Bi2Te3, 1.75(1)km/s, compared to Sb2Te3, 1.85(4)km/s, is not only related to the larger mass density but also to a larger Debye level. The observed low lattice thermal conductivity at 295K, 2.4Wm-1K-1 for Sb2Te3 and 1.6Wm-1K-1 for Bi2Te3, cannot be explained by anharmonicity alone given the rather modest Grüneisen parameters, 1.7(1) for Sb2Te3 and 1.5(1) for Bi2Te3, without accounting for the reduced speed of sound and more importantly the low acoustic cutoff energy.

  11. Gate-tunable high mobility remote-doped InSb/In1−xAlxSb quantum well

    NARCIS (Netherlands)

    Yi, W.; Kiselev, A.A.; Thorp, J.; Noah, R.; Nguyen, B.M.; Bui, S.; Rajavel, R.D.; Hussain, T.; Gyure, M.F.; Kratz, P.; Qian, Q.; Manfra, M.J.; Pribiag, V.S.; Kouwenhoven, L.P.; Marcus, C.M.; Sokolich, M.

    2015-01-01

    Gate-tunable high-mobility InSb/In1−xAlxSb quantum wells (QWs) grown on GaAs substrates are reported. The QW two-dimensional electron gas (2DEG) channel mobility in excess of 200 000 cm2/V s is measured at T = 1.8 K. In asymmetrically remote-doped samples with an HfO2 gate dielectric formed by atomi

  12. AgSbSe{sub 2} and AgSb(S,Se){sub 2} thin films for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Garza, J.G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Shaji, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Rodriguez, A.C.; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Krishnan, B., E-mail: kbindu_k@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-10-01

    Silver antimony selenide (AgSbSe{sub 2}) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb{sub 2}S{sub 3}), silver selenide (Ag{sub 2}Se), selenium (Se) and silver (Ag). Sb{sub 2}S{sub 3} thin film was prepared from a chemical bath containing SbCl{sub 3} and Na{sub 2}S{sub 2}O{sub 3}, Ag{sub 2}Se from a solution containing AgNO{sub 3} and Na{sub 2}SeSO{sub 3} and Se thin films from an acidified solution of Na{sub 2}SeSO{sub 3}, at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350 deg. C in vacuum (10{sup -3} Torr) for 1 h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe{sub 2} or AgSb(S,Se){sub 2} depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV-visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe{sub 2}/Al was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this structure showed V{sub oc} = 435 mV and J{sub sc} = 0.08 mA/cm{sup 2} under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe{sub 2} as an absorber material by a non-toxic selenization process is achieved.

  13. InAsSb Hybrid Imager Evaluation

    Science.gov (United States)

    Rode, J. P.

    1980-05-01

    Current research on infrared hybrid focal planes is directed toward devices in which detection occurs in a p-n junction formed in an intrinsic narrow energy bandgap semiconductor, and signal processing is accomplished in a Si CCD multiplexer which is electrically interfaced to the detector array. A hybrid array such as this, where the detector format is a 32 x 32 matrix, has been fabricated. The active material is backside-illuminated InAsSb which has been planar processed and fully passivated. The cutoff wavelength is 4.0 μm at the operating temperature of 77K. The CCD is four phase with a two level polysilicon gate structure. The signal input is via direct injection with an option for dc suppression. Operation of the focal plane in a staring mode that uses dc suppression is discussed. Data derived from the video output is presented; this includes responsivity and detectivity. Off focal plane non-uniformity compensation is also discussed. Displays of thermal images utilizing processed data from the hybrid focal plane array will be shown.

  14. Vertical cavity surface emitting laser emitting at 1.56 microns with AlGaAsSb/AlAsSb distributed Bragg reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Blum, O.; Klem, J.F.; Lear, K.L.; Vawter, G.A.; Kurtz, S.R.

    1998-07-01

    The authors report 77K operation of an optically pumped vertical cavity surface emitting laser with an Sb-based cavity. The structure consists of 15 and 20 pair AlGaAsSb/AlAsSb top and bottom reflectors and a bulk InGaAs active region.

  15. Selective-Area MOCVD Growth and Carrier-Transport-Type Control of InAs(Sb)/GaSb Core-Shell Nanowires.

    Science.gov (United States)

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Yang, Tao

    2016-12-14

    We report the first selective-area growth of high quality InAs(Sb)/GaSb core-shell nanowires on Si substrates using metal-organic chemical vapor deposition (MOCVD) without foreign catalysts. Transmission electron microscopy (TEM) analysis reveals that the overgrowth of the GaSb shell is highly uniform and coherent with the InAs(Sb) core without any misfit dislocations. To control the structural properties and reduce the planar defect density in the self-catalyzed InAs core nanowires, a trace amount of Sb was introduced during their growth. As the Sb content increases from 0 to 9.4%, the crystal structure of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB) structure to a perfect ZB phase. Electrical measurements reveal that both the n-type InAsSb core and p-type GaSb shell can work as active carrier transport channels, and the transport type of core-shell nanowires can be tuned by the GaSb shell thickness and back-gate voltage. This study furthers our understanding of the Sb-induced crystal-phase control of nanowires. Furthermore, the high quality InAs(Sb)/GaSb core-shell nanowire arrays obtained here pave the foundation for the fabrication of the vertical nanowire-based devices on a large scale and for the study of fundamental quantum physics.

  16. Ge nanobelts with high compressive strain fabricated by secondary oxidation of self-assembly SiGe rings

    DEFF Research Database (Denmark)

    Lu, Weifang; Li, Cheng; Lin, Guangyang

    2015-01-01

    Curled Ge nanobelts were fabricated by secondary oxidation of self-assembly SiGe rings, which were exfoliated from the SiGe stripes on the insulator. The Ge-rich SiGe stripes on insulator were formed by hololithography and modified Ge condensation processes of Si0.82Ge0.18 on SOI substrate. Ge na...... nanobelts, which extrudes to Ge nanobelts in radial and tangent directions during the cooling process. This technique is promising for application in high-mobility Ge nano-scale transistors...

  17. Effect of Ge Content on the Formation of Ge Nanoclusters in Magnetron-Sputtered GeZrOx-Based Structures.

    Science.gov (United States)

    Khomenkova, L; Lehninger, D; Kondratenko, O; Ponomaryov, S; Gudymenko, O; Tsybrii, Z; Yukhymchuk, V; Kladko, V; von Borany, J; Heitmann, J

    2017-12-01

    Ge-rich ZrO2 films, fabricated by confocal RF magnetron sputtering of pure Ge and ZrO2 targets in Ar plasma, were studied by multi-angle laser ellipsometry, Raman scattering, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction for varied deposition conditions and annealing treatments. It was found that as-deposited films are homogeneous for all Ge contents, thermal treatment stimulated a phase separation and a formation of crystalline Ge and ZrO2. The "start point" of this process is in the range of 640-700 °C depending on the Ge content. The higher the Ge content, the lower is the temperature necessary for phase separation, nucleation of Ge nanoclusters, and crystallization. Along with this, the crystallization temperature of the tetragonal ZrO2 exceeds that of the Ge phase, which results in the formation of Ge crystallites in an amorphous ZrO2 matrix. The mechanism of phase separation is discussed in detail.

  18. A study on NiGe-contacted Ge n+/p Ge shallow junction prepared by dopant segregation technique

    Science.gov (United States)

    Tsui, Bing-Yue; Shih, Jhe-Ju; Lin, Han-Chi; Lin, Chiung-Yuan

    2015-05-01

    In this work, the effect of dopant segregation on the NiGe/n-Ge contact is studied by experiments and first-principles calculations. Both Al-contacted and NiGe-contacted n+/p junctions were fabricated. Phosphorus and arsenic ions were Implanted Before Germanide (IBG) formation or Implanted After Germanide (IAG) formation. The NiGe-contacted junction always exhibit higher forward current than the Al-contacted junction due to dopant segregation. First principles calculations predict that phosphorus atoms tend to segregate on both NiGe side and Ge side while arsenic atoms tend to segregate at Ge side. Since phosphorus has higher activation level and lower diffusion coefficient than arsenic, we propose a phosphorus IBG + arsenic IAG process. Shallow n+/p junction with junction depth 90 nm below the NiGe/Ge interface is achieved. The lowest and average contact resistivity is 2 × 10-6 Ω cm2 and 6.7 × 10-6 Ω cm2, respectively. Methods which can further reduce the junction depth and contact resistivity are suggested.

  19. Observation of Sb sub 2 O sub 3 nanocrystals in SiO sub 2 after Sb ion implantation

    CERN Document Server

    Ignatova, V A; Gijbels, R; Adams, F; Lebedev, O I; Landuyt, J V; Waetjen, U

    2002-01-01

    Antimony nanocrystals were formed in thin SiO sub 2 films using low-energy ion implantation of Sb followed by annealing. Using Fourier transform laser microprobe mass spectrometry (FT LMMS), we observed for the first time the presence of antimony oxide in the intermediate phase (as-implanted layer of Sb) by means of signals referring to the intact Sb sub 2 O sub 3 molecules. Only SbO sup + fragments, but no adduct ions of Sb sub 2 O sub 3 could be detected in annealed samples. The size and the distribution of the nanocrystals formed around the initial depth of implantation were studied in the as-implanted samples by high-resolution electron microscopy (HREM). The crystalline structure of these nanocrystals was also studied and the presence of antimony trioxide Sb sub 2 O sub 3 in the form of valentinite was proven. After the annealing step, the implanted material had spread into a wider band. The method introduced here, based on combining TEM (transmission electron microscopy) and FT LMMS results, offers the ...

  20. MBE growth of Sb-based bulk nBn infrared photodetector structures on 6-inch GaSb substrates

    Science.gov (United States)

    Liu, Amy W. K.; Lubyshev, Dmitri; Qiu, Yueming; Fastenau, Joel M.; Wu, Ying; Furlong, Mark J.; Tybjerg, Marius; Martinez, Rebecca J.; Mowbray, Andrew; Smith, Brian

    2015-06-01

    The GaSb-based 6.1 Å lattice constant family of materials and heterostructures provides rich bandgap engineering possibilities and have received considerable attention for their potential and demonstrated performance in infrared (IR) detection and imaging applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications. To succeed, they must move from research laboratory settings to general semiconductor production, and high-quality GaSb-based epitaxial wafers with diameter larger than the current standard 3-inch are highly desirable. 4-inch GaSb substrates have been in production for a couple of years and are now commercially available. Recently, epi-ready GaSb substrates with diameter in excess of 6-inch were successfully produced. In this work, we report on the MBE (Molecular Beam Epitaxy) growth of generic MWIR bulk nBn photodetectors on 6-inch diameter GaSb substrates. The surface morphology, optical and structural quality of the epiwafers as evaluated by atomic force microscopy (AFM), Nomarski microscopy, low temperature photoluminescence (PL) spectroscopy, and high-resolution x-ray diffraction (XRD) will be discussed. Current density versus voltage (J-V) and photoresponsivity measurements from large-area mesa diode fabricated will also be reported. Material and device properties of these 6-inch epiwafers will be compared to similar structures grown on commercially available 4-inch diameter GaSb substrates.