WorldWideScience

Sample records for sapphire

  1. Sapphire and Ti:sapphire buried waveguide structures

    NARCIS (Netherlands)

    Pollnau, Markus

    Due to its excellent thermal, mechanical, and optical properties, sapphire is one of the most suitable material for integrated optical devices. Although this hard crystalline material is particularly difficult to process, fabrication of Ti3+-doped sapphire surface channel waveguides by surface

  2. Neutron Transmission through Sapphire Crystals

    DEFF Research Database (Denmark)

    Sapphire crystals are excellent filters of fast neutrons, while at the same time exhibit moderate to very little absorption at smaller energies. We have performed an extensive series of measurements in order to quantify the above effect. Alongside our experiments, we have performed a series...... of simulations, in order to reproduce the transmission of cold neutrons through sapphire crystals. Those simulations were part of the effort of validating and improving the newly developed interface between the Monte-Carlo neutron transport code MCNP and the Monte Carlo ray-tracing code McStas....

  3. Ti:Sapphire waveguide lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Pashinin, P.P.; Grivas, C.; Laversenne, L.; Wilkinson, J.S.; Eason, R.W.; Shepherd, D.P.

    2007-01-01

    Titanium-doped sapphire is one of the most prominent laser materials and is appreciated for its excellent heat conductivity and broadband gain spectrum, allowing for a wide wavelength tunability and generation of ultrashort pulses. As one of the hardest materials, it can also serve as a model system

  4. Germanium Nanocrystals Embedded in Sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Q.; Sharp, I.D.; Liao, C.Y.; Yi, D.O.; Ager III, J.W.; Beeman, J.W.; Yu, K.M.; Chrzan, D.C.; Haller, E.E.

    2005-04-15

    {sup 74}Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by damage. Embedded nanocrystals experience large compressive stress relative to bulk, as embedded in sapphire melt very close to the bulk melting point (Tm = 936 C) whereas experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and measured by Raman spectroscopy of the zone center optical phonon. In contrast, reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding thermal annealing. Transmission electron microscopy (TEM) of as-grown samples those embedded in silica exhibit a significant melting point hysteresis around T{sub m}.

  5. Surface-mount sapphire interferometric temperature sensor

    Science.gov (United States)

    Zhu, Yizheng; Wang, Anbo

    2006-08-01

    A fiber-optic high-temperature sensor is demonstrated by bonding a 45°-polished single-crystal sapphire fiber on the surface of a sapphire wafer, whose optical thickness is temperature dependent and measured by white-light interferometry. A novel adhesive-free coupling between the silica and sapphire fibers is achieved by fusion splicing, and its performance is characterized. The sensor's interference signal is investigated for its dependence on angular alignment between the fiber and the wafer. A prototype sensor is tested to 1170 °C with a resolution of 0.4 °C, demonstrating excellent potential for high-temperature measurement.

  6. Sapphire Viewports for a Venus Probe Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase 1 program will demonstrate that sapphire viewports are feasible for use in Venus probes. TvU's commercial viewport products have demonstrated that...

  7. Sapphire Energy - Integrated Algal Biorefinery

    Energy Technology Data Exchange (ETDEWEB)

    White, Rebecca L. [Sapphire Energy, Inc., Columbus, NM (United States). Columbus Algal Biomass Farm; Tyler, Mike [Sapphire Energy, Inc., San Diego, CA (United States)

    2015-07-22

    Sapphire Energy, Inc. (SEI) is a leader in large-scale photosynthetic algal biomass production, with a strongly cohesive research, development, and operations program. SEI takes a multidiscipline approach to integrate lab-based strain selection, cultivation and harvest and production scale, and extraction for the production of Green Crude oil, a drop in replacement for traditional crude oil.. SEI’s technical accomplishments since 2007 have produced a multifunctional platform that can address needs for fuel, feed, and other higher value products. Figure 1 outlines SEI’s commercialization process, including Green Crude production and refinement to drop in fuel replacements. The large scale algal biomass production facility, the SEI Integrated Algal Biorefinery (IABR), was built in Luna County near Columbus, New Mexico (see fig 2). The extraction unit was located at the existing SEI facility in Las Cruces, New Mexico, approximately 95 miles from the IABR. The IABR facility was constructed on time and on budget, and the extraction unit expansion to accommodate the biomass output from the IABR was completed in October 2012. The IABR facility uses open pond cultivation with a proprietary harvesting method to produce algal biomass; this biomass is then shipped to the extraction facility for conversion to Green Crude. The operation of the IABR and the extraction facilities has demonstrated the critical integration of traditional agricultural techniques with algae cultivation knowledge for algal biomass production, and the successful conversion of the biomass to Green Crude. All primary unit operations are de-risked, and at a scale suitable for process demonstration. The results are stable, reliable, and long-term cultivation of strains for year round algal biomass production. From June 2012 to November 2014, the IABR and extraction facilities produced 524 metric tons (MT) of biomass (on a dry weight basis), and 2,587 gallons of Green Crude. Additionally, the IABR

  8. Oxygen interstitial trapping in electron irradiated sapphire

    CERN Document Server

    Morono, A

    2002-01-01

    An existing model for first stage anion vacancy stabilization in irradiated alkali halides has been applied to sapphire. To monitor the F centre concentration growth during irradiation, radioluminescence instead of optical absorption measurements has been employed. The results indicate that the model is valid for sapphire and suggest that the F centre stabilization process depends on oxygen interstitial trapping. This implies that the resistance to radiation damage at low doses should depend on the impurity and dislocation content of the material. One presumes the model may be extended to other oxides.

  9. Sapphire and other dielectric waveguide devices

    NARCIS (Netherlands)

    Pollnau, Markus

    2008-01-01

    Different fabrication methods have been explored successfully and surface and buried channel waveguide lasers have been demonstrated in Ti:sapphire for the first time. Since the propagation losses of these first-generation waveguides are still rather high, substantial improvement is required in

  10. Advanced thin dicing blade for sapphire substrate

    Directory of Open Access Journals (Sweden)

    Koji Matsumaru, Atsushi Takata and Kozo Ishizaki

    2005-01-01

    Full Text Available Advanced thin dicing blades for cutting sapphire were fabricated and evaluated for cutting performance with respect to dicing blade wear and meandering of cutting lines. Three kinds of different commercial blades were used to compare the cutting performance. These blades had the same thickness and the same diamond grain size. The matrix material of one dicing blade was nickel–phosphorus alloy and two other were a vitric material. Newly developed dicing blades consisted of a vitric material with pore. A dicing machine was used for cutting sapphire. Turning velocity, cutting depth and feeding rate were 20,000 min−1, 200 μm and 1 mm s−1, respectivity. Cutting directions were 110 and 010. All blades could cut 1000 mm and more in the 110 direction. On the other hand, commercial dicing blades generated meandering lines and were broken only by 50 mm of cutting length in 010 direction. Fabricated blade can cut 1000 mm and more in 010 direction. The wear of fabricated dicing blade was the largest in the dicing blades. Although cutting performance of commercial dicing blades depended on the sapphire orientation, that of fabricated blade was independent of the sapphire orientation. It has been confirmed that the fabricated dicing blade was kept a cutting ability by flash diamonds on the dicing blade surface, which were created by wear of blade during cutting sapphire. Low cutting ability of commercial blades increased cutting force between with increase of cutting length. The increased cutting force produced to bend a blade and cutting lines, and finally a fracture of blade.

  11. Sapphire Viewports for a Venus Probe

    Science.gov (United States)

    Bates, Stephen

    2012-01-01

    A document discusses the creation of a viewport suitable for use on the surface of Venus. These viewports are rated for 500 C and 100 atm pressure with appropriate safety factors and reliability required for incorporation into a Venus Lander. Sapphire windows should easily withstand the chemical, pressure, and temperatures of the Venus surface. Novel fixture designs and seals appropriate to the environment are incorporated, as are materials compatible with exploration vessels. A test cell was fabricated, tested, and leak rate measured. The window features polish specification of the sides and corners, soft metal padding of the sapphire, and a metal C-ring seal. The system safety factor is greater than 2, and standard mechanical design theory was used to size the window, flange, and attachment bolts using available material property data. Maintenance involves simple cleaning of the window aperture surfaces. The only weakness of the system is its moderate rather than low leak rate for vacuum applications.

  12. Luminescence efficiency during ion implantation of sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Alghamdi, A.; Townsend, P.D. (Sussex Univ., Brighton (UK). School of Mathematical and Physical Sciences)

    1990-01-01

    Luminescence signals produced during ion implantation of sapphire are related to the F,F{sup +} and F{sub 2} defect centres. However, the efficiency of light production changes with ion beam dose, the rate of energy deposition and radiation damage, hence the signals are not proportional to the defect concentrations. Data are presented which suggest that the light is primarily produced by electronic excitation. Luminescence efficiency within the region of nuclear collisions is very low. It is not possible to determine the energy dependence of the luminescence intensity, as a function of ion energy, by energy variations within a single target crystal. (author).

  13. Zro2 Thin-Film-Based Sapphire Fiber Temperature Sensor

    OpenAIRE

    Wang, Jiajun; Lally, Evan M; Wang, Xiaoping; Gong, Jianmin; Pickrell, Gary R.; Wang, Anbo

    2012-01-01

    A submicrometer-thick zirconium dioxide film was deposited on the tip of a polished C-plane sapphire fiber to fabricate a temperature sensor that can work to an extended temperature range. Zirconium dioxide was selected as the thin film material to fabricate the temperature sensor because it has relatively close thermal expansion to that of sapphire, but more importantly it does not react appreciably with sapphire up to 1800 degrees C. In order to study the properties of the deposited thin fi...

  14. Oleophobic properties of the step-and-terrace sapphire surface

    Science.gov (United States)

    Muslimov, A. E.; Butashin, A. V.; Kanevsky, V. M.

    2017-03-01

    Sapphire is widely used in production of optical windows for various devices due to its mechanical and optical properties. However, during operation the surface can be affected by fats, oils, and other organic contaminations. Therefore, it is important to improve the oleophobic properties of sapphire windows. In this study, we investigate the interaction of a supersmooth sapphire surface with oleic acid droplets, which imitate human finger printing. It is established that chemical-mechanical polishing with additional annealing in air, which leads to the formation of an atomically smooth sapphire surface, makes it possible to significantly improve the oleophobic properties of the surface. The results are analyzed using the Ventsel-Deryagin homogeneous wetting model.

  15. Nanostructured sapphire optical fiber for sensing in harsh environments

    Science.gov (United States)

    Chen, Hui; Liu, Kai; Ma, Yiwei; Tian, Fei; Du, Henry

    2017-05-01

    We describe an innovative and scalable strategy of transforming a commercial unclad sapphire optical fiber to an allalumina nanostructured sapphire optical fiber (NSOF) that overcomes decades-long challenges faced in the field of sapphire fiber optics. The strategy entails fiber coating with metal Al followed by subsequent anodization to form anodized alumina oxide (AAO) cladding of highly organized pore channel structure. We show that Ag nanoparticles entrapped in AAO show excellent structural and morphological stability and less susceptibility to oxidation for potential high-temperature surface-enhanced Raman Scattering (SERS). We reveal, with aid of numerical simulations, that the AAO cladding greatly increases the evanescent-field overlap both in power and extent and that lower porosity of AAO results in higher evanescent-field overlap. This work has opened the door to new sapphire fiber-based sensor design and sensor architecture.

  16. Oleophobic properties of the step-and-terrace sapphire surface

    Energy Technology Data Exchange (ETDEWEB)

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kanevsky, V. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Center “Crystallography and Photonics” (Russian Federation)

    2017-03-15

    Sapphire is widely used in production of optical windows for various devices due to its mechanical and optical properties. However, during operation the surface can be affected by fats, oils, and other organic contaminations. Therefore, it is important to improve the oleophobic properties of sapphire windows. In this study, we investigate the interaction of a supersmooth sapphire surface with oleic acid droplets, which imitate human finger printing. It is established that chemical–mechanical polishing with additional annealing in air, which leads to the formation of an atomically smooth sapphire surface, makes it possible to significantly improve the oleophobic properties of the surface. The results are analyzed using the Ventsel–Deryagin homogeneous wetting model.

  17. Numerical Study of Damage Propagation and Dynamic Fracture in Sapphire

    Science.gov (United States)

    2016-08-30

    impacting the large surface of the plate [basal plane (1000) of the single sapphire crystal. However, cracking pattern of the impact of the r-plane (101...sapphire of different crystal orientation with respect to the line of impact . 15. SUBJECT TERMS low impact velocity, modeling, simulation, drop ...performance. Overall, the report showed that the presence of surface flaws and defect location relative to impact site were more detrimental to

  18. Structure of the Dislocation in Sapphire

    DEFF Research Database (Denmark)

    Bilde-Sørensen, Jørgen; Thölen, A. R.; Gooch, D. J.

    1976-01-01

    Experimental evidence of the existence of 01 0 dislocations in the {2 0} prism planes in sapphire has been obtained by transmission electron microscopy. By the weak-beam technique it has been shown that the 01 0 dislocations may dissociate into three partials. The partials all have a Burgers vector...... of ⅓ 01 0 and are separated by two identical faults. The distance between two partials is in the range 75-135 Å, corresponding to a fault energy of 320±60 mJ/m2. Perfect 01 0 dislocations have also been observed. These dislocations exhibited either one or two peaks when imaged in the (03 0) reflection...... by the weak-beam technique. The interpretation of the electron micrographs has been supported by computer simulation of the dislocation images. A faulted dipole has been observed, indicating that some of the prismatic loops often seen to lie in rows along [0001] are faulted with a ⅓ 01 0 Burgers vector...

  19. Development of a sapphire fiber thermometer using two wavelength bands

    Science.gov (United States)

    Ye, Linhua; Shen, Yonghang

    1996-09-01

    This paper reports the development of a sapphire ((alpha) - Al2O3) single crystal optical fiber thermometer using two wavelength bands. A thin film of precious metal or ceramic deposited onto one end of the sapphire fiber forms a mini-radiation cavity. The other end of the sapphire fiber is coupled to a low-loss silica fiber. Radiation from the small cavity is transmitted along the silica fiber into a photodetection system which consists of a lens, beam splitter, two interference filters (820 nm and 940 nm center wavelength, 30 nm bandwidth) and two silicon photocells. The temperature measurement is based on the detection of radiation from the small cavity. The sapphire fiber (0.25 - 1.0 mm diameter, 100 - 450 mm length) was grown by the laser heated pedestal growth (LHPG) methods. Transmission loss in the sapphire fiber was experimentally measured. Theoretical analysis shows the apparent emittance of the small cavity with a length to diameter (L/D) ratio greater than eight is a constant value near to one, so the small cavity can be considered as a small black-body cavity. Using the developed sapphire fiber temperature sensor, we have built a sapphire fiber thermometer based on a 8098 single-chip microcomputer system. It was calibrated at some known stable temperature point and uses the fundamental radiation law to extrapolate to other temperatures. By taking the ratio of the optical power at two wavelengths, errors due to changes in the system, such as emissivity and transmission losses, can be canceled out. The thermometer has an operating temperature range of 800 to 1900 degrees Celsius, and an accuracy of 0.2% at 1000 degrees Celsius. There are a number of applications of the thermometer both in science and industry.

  20. Sapphire-fiber-based distributed high-temperature sensing system.

    Science.gov (United States)

    Liu, Bo; Yu, Zhihao; Hill, Cary; Cheng, Yujie; Homa, Daniel; Pickrell, Gary; Wang, Anbo

    2016-09-15

    We present, for the first time to our knowledge, a sapphire-fiber-based distributed high-temperature sensing system based on a Raman distributed sensing technique. High peak power laser pulses at 532 nm were coupled into the sapphire fiber to generate the Raman signal. The returned Raman Stokes and anti-Stokes signals were measured in the time domain to determine the temperature distribution along the fiber. The sensor was demonstrated from room temperature up to 1200°C in which the average standard deviation is about 3.7°C and a spatial resolution of about 14 cm was achieved.

  1. Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire. II. Electron energy loss spectroscopic study

    Directory of Open Access Journals (Sweden)

    Sung Bo Lee

    2015-07-01

    Full Text Available In Part I, we have shown that the addition of Si into sapphire by ion implantationmakes the sapphire substrate elastically softer than for the undoped sapphire. The more compliant layer of the Si-implanted sapphire substrate can absorb the misfit stress at the GaN/sapphire interface, which produces a lower threading-dislocation density in the GaN overlayer. Here in Part II, based on experimental results by electron energy loss spectroscopy and a first-principle molecular orbital calculation in the literature, we suggest that the softening effect of Si results from a reduction of ionic bonding strength in sapphire (α-Al2O3 with the substitution of Si for Al.

  2. Single-transverse-mode Ti:sapphire rib waveguide laser

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus

    2005-01-01

    Laser operation of Ti:sapphire rib waveguides fabricated using photolithography and ion beam etching in pulsed laser deposited layers is reported. Polarized laser emission was observed at 792.5 nm with an absorbed pump power threshold of 265 mW, which is more than a factor of 2 lower in comparison

  3. High power continuous-wave titanium:sapphire laser

    Science.gov (United States)

    Erbert, Gaylen V.; Bass, Isaac L.; Hackel, Richard P.; Jenkins, Sherman L.; Kanz, Vernon K.; Paisner, Jeffrey A.

    1993-01-01

    A high-power continuous-wave laser resonator (10) is provided, wherein first, second, third, fourth, fifth and sixth mirrors (11-16) form a double-Z optical cavity. A first Ti:Sapphire rod (17) is disposed between the second and third mirrors (12,13) and at the mid-point of the length of the optical cavity, and a second Ti:Sapphire rod (18) is disposed between the fourth and fifth mirrors (14,15) at a quarter-length point in the optical cavity. Each Ti:Sapphire rod (17,18) is pumped by two counter-propagating pump beams from a pair of argon-ion lasers (21-22, 23-24). For narrow band operation, a 3-plate birefringent filter (36) and an etalon (37) are disposed in the optical cavity so that the spectral output of the laser consists of 5 adjacent cavity modes. For increased power, seventy and eighth mirrors (101, 192) are disposed between the first and second mirrors (11, 12) to form a triple-Z optical cavity. A third Ti:Sapphire rod (103) is disposed between the seventh and eighth mirrors (101, 102) at the other quarter-length point in the optical cavity, and is pumped by two counter-propagating pump beams from a third pair of argon-ion lasers (104, 105).

  4. Single-Crystal Sapphire Optical Fiber Sensor Instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Pickrell, Gary [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Scott, Brian [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Wang, Anbo [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Yu, Zhihao [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States)

    2013-12-31

    This report summarizes technical progress on the program “Single-Crystal Sapphire Optical Fiber Sensor Instrumentation,” funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. This project was completed in three phases, each with a separate focus. Phase I of the program, from October 1999 to April 2002, was devoted to development of sensing schema for use in high temperature, harsh environments. Different sensing designs were proposed and tested in the laboratory. Phase II of the program, from April 2002 to April 2009, focused on bringing the sensor technologies, which had already been successfully demonstrated in the laboratory, to a level where the sensors could be deployed in harsh industrial environments and eventually become commercially viable through a series of field tests. Also, a new sensing scheme was developed and tested with numerous advantages over all previous ones in Phase II. Phase III of the program, September 2009 to December 2013, focused on development of the new sensing scheme for field testing in conjunction with materials engineering of the improved sensor packaging lifetimes. In Phase I, three different sensing principles were studied: sapphire air-gap extrinsic Fabry-Perot sensors; intensity-based polarimetric sensors; and broadband polarimetric sensors. Black body radiation tests and corrosion tests were also performed in this phase. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. At the beginning of Phase II, in June 2004, the BPDI sensor was tested at the Wabash River coal gasifier

  5. Time dependent temperature distribution in pulsed Ti:sapphire lasers

    Science.gov (United States)

    Buoncristiani, A. Martin; Byvik, Charles E.; Farrukh, Usamah O.

    1988-01-01

    An expression is derived for the time dependent temperature distribution in a finite solid state laser rod for an end-pumped beam of arbitrary shape. The specific case of end pumping by circular (constant) or Gaussian beam is described. The temperature profile for a single pump pulse and for repetitive pulse operation is discussed. The particular case of the temperature distribution in a pulsed titanium:sapphire rod is considered.

  6. Heteroepitaxial Writing of Silicon-on-Sapphire Nanowires.

    Science.gov (United States)

    Xu, Mingkun; Xue, Zhaoguo; Wang, Jimmy; Zhao, Yaolong; Duan, Yao; Zhu, Guangyao; Yu, Linwei; Xu, Jun; Wang, Junzhuan; Shi, Yi; Chen, Kunji; Roca I Cabarrocas, Pere

    2016-12-14

    The heteroepitaxial growth of crystal silicon thin films on sapphire, usually referred to as SoS, has been a key technology for high-speed mixed-signal integrated circuits and processors. Here, we report a novel nanoscale SoS heteroepitaxial growth that resembles the in-plane writing of self-aligned silicon nanowires (SiNWs) on R-plane sapphire. During a low-temperature growth at 900 °C, the bottom heterointerface cultivates crystalline Si pyramid seeds within the catalyst droplet, while the vertical SiNW/catalyst interface subsequently threads the seeds into continuous nanowires, producing self-oriented in-plane SiNWs that follow a set of crystallographic directions of the sapphire substrate. Despite the low-temperature fabrication process, the field effect transistors built on the SoS-SiNWs demonstrate a high on/off ratio of >5 × 104 and a peak hole mobility of >50 cm2/V·s. These results indicate the novel potential of deploying in-plane SoS nanowire channels in places that require high-performance nanoelectronics and optoelectronics with a drastically reduced thermal budget and a simplified manufacturing procedure.

  7. SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    A. Wang; G. Pickrell; R. May

    2002-09-10

    Accurate measurement of temperature is essential for the safe and efficient operation and control of a wide range of industrial processes. Appropriate techniques and instrumentation are needed depending on the temperature measurement requirements in different industrial processes and working environments. Harsh environments are common in many industrial applications. These harsh environments may involve extreme physical conditions, such as high-temperature, high-pressure, corrosive agents, toxicity, strong electromagnetic interference, and high-energy radiation exposure. Due to these severe environmental conditions, conventional temperature sensors are often difficult to apply. This situation has opened a new but challenging opportunity for the sensor society to provide robust, high-performance, and cost-effective temperature sensors capable of operating in those harsh environments. The focus of this research program has been to develop a temperature measurement system for temperature measurements in the primary and secondary stages of slagging gasifiers. For this application the temperature measurement system must be able to withstand the extremely harsh environment posed by the high temperatures and corrosive agents present in these systems. Real-time, accurate and reliable monitoring of temperature for the coal gasification process is important to realize the full economic potential of these gasification systems. Long life and stability of operation in the high temperature environment is essential for the temperature measurement system to ensure the continuous running of the coal gasification system over the long term. In this high temperature and chemically corrosive environment, rather limited high temperature measurement techniques such as high temperature thermocouples and optical/acoustic pyrometers are available, each with their own limitations. In this research program, five different temperature sensing schemes based on the single crystal sapphire

  8. Spectroscopic properties for identifying sapphire samples from Ban Bo Kaew, Phrae Province, Thailand

    Science.gov (United States)

    Mogmued, J.; Monarumit, N.; Won-in, K.; Satitkune, S.

    2017-09-01

    Gemstone commercial is a high revenue for Thailand especially ruby and sapphire. Moreover, Phrae is a potential gem field located in the northern part of Thailand. The studies of spectroscopic properties are mainly to identify gemstone using advanced techniques (e.g. UV-Vis-NIR spectrophotometry, FTIR spectrometry and Raman spectroscopy). Typically, UV-Vis-NIR spectrophotometry is a technique to study the cause of color in gemstones. FTIR spectrometry is a technique to study the functional groups in gem-materials. Raman pattern can be applied to identify the mineral inclusions in gemstones. In this study, the natural sapphires from Ban Bo Kaew were divided into two groups based on colors including blue and green. The samples were analyzed by UV-Vis-NIR spectrophotometer, FTIR spectrometer and Raman spectroscope for studying spectroscopic properties. According to UV-Vis-NIR spectra, the blue sapphires show higher Fe3+/Ti4+ and Fe2+/Fe3+ absorption peaks than those of green sapphires. Otherwise, green sapphires display higher Fe3+/Fe3+ absorption peaks than blue sapphires. The FTIR spectra of both blue and green sapphire samples show the absorption peaks of -OH,-CH and CO2. The mineral inclusions such as ferrocolumbite and rutile in sapphires from this area were observed by Raman spectroscope. The spectroscopic properties of sapphire samples from Ban Bo Kaew, Phrae Province, Thailand are applied to be the specific evidence for gemstone identification.

  9. Leveraging Python Interoperability Tools to Improve Sapphire's Usability

    Energy Technology Data Exchange (ETDEWEB)

    Gezahegne, A; Love, N S

    2007-12-10

    The Sapphire project at the Center for Applied Scientific Computing (CASC) develops and applies an extensive set of data mining algorithms for the analysis of large data sets. Sapphire's algorithms are currently available as a set of C++ libraries. However many users prefer higher level scripting languages such as Python for their ease of use and flexibility. In this report, we evaluate four interoperability tools for the purpose of wrapping Sapphire's core functionality with Python. Exposing Sapphire's functionality through a Python interface would increase its usability and connect its algorithms to existing Python tools.

  10. Thermal resistance of indium coated sapphire-copper contacts below 0.1 K

    Science.gov (United States)

    Eisel, T.; Bremer, J.; Koettig, T.

    2014-11-01

    High thermal resistances exist at ultra-low temperatures for solid-solid interfaces. This is especially true for pressed metal-sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1 K. Consequently, it is difficult to predict the thermal resistance of pressed metal-sapphire joints at temperatures below 1 K. In this paper the thermal resistances across four different copper-sapphire-copper sandwiches are presented in a temperature range between 30 mK and 100 mK. The investigated sandwiches feature either rough or polished sapphire discs (Ø 20 mm × 1.5 mm) to investigate the phonon scattering at the boundaries. All sandwiches apply indium foils as intermediate layers on both sides of the sapphire. Additionally to the indium foils, thin indium films are vapour deposited onto both sides of one rough and one polished sapphire in order to improve the contact to the sapphire. Significantly different thermal resistances have been found amongst the investigated sandwiches. The lowest total thermal resistivity (roughly 26 cm2 K4/W at 30 mK helium temperature) is achieved across a sandwich consisting of a polished sapphire with indium vapour deposition. The thermal boundary resistance between indium and sapphire is estimated from the total thermal resistivity by assuming the scattering at only one boundary, which is the warm sapphire boundary where phonons impinge, and taking the scattering in the sapphire bulk into account. The so derived thermal boundary resistance agrees at low temperatures very well with the acoustic mismatch theory.

  11. Response of sapphire thermocurrent dosimeters to fast neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, D.W.; Moran, P.R.

    1975-01-01

    The response of sapphire (Al/sub 2/O/sub 3/) thermocurrent (TC) dosimeters to 14 MeV neutrons is about 10% of the response to cesium gamma rays on an equivalent tissue rad basis. The addition of proton radiator covers of methyl methacrylate increases this response to about 15%. The magnitude of the thermocurrent peak at 260/sup 0/ (peak 3) allows measurement of gamma ray exposures of 10 mR with a signal to noise ratio of about unity.

  12. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    Science.gov (United States)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  13. Ultrafast, ultrahigh-peak power Ti:sapphire laser system

    Energy Technology Data Exchange (ETDEWEB)

    Yamakawa, Koichi; Aoyama, Makoto; Matsuoka, Shinichi; Akahane, Yutaka; Kase, Teiji; Nakano, Fumihiko; Sagisaka, Akito [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan)

    2001-01-01

    We review progress in the generation of multiterawatt optical pulses in the 10-fs range. We describe a design, performance and characterization of a Ti:sapphire laser system based on chirped-pulse amplification, which has produced a peak power in excess of 100-TW with sub-20-fs pulse durations and an average power of 19-W at a 10-Hz repetition rate. We also discuss extension of this system to the petawatt power level and potential applications in the relativistic, ultrahigh intensity regimes. (author)

  14. A 10-Hz terawatt class Ti:sapphire laser system: Development and ...

    Indian Academy of Sciences (India)

    875–881. A 10-Hz terawatt class Ti:sapphire laser system: Development and applications ... petawatt class CPA laser systems using different gain media have been realized. In particular, Ti:sapphire CPA laser .... video cameras to monitor the input and amplified output beams at different loca- tions and to correct their spatial ...

  15. Flashlamp pumped Ti-sapphire laser for ytterbium glass chirped pulse amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Akihiko; Ohzu, Akira; Sugiyama, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others

    1998-03-01

    A flashlamp pumped Ti:sapphire laser is designed for ytterbium glass chirped pulse amplification. A high quality Ti:sapphire rod and a high energy long pulse discharging power supply are key components. The primary step is to produce the output power of 10 J per pulse at 920 nm. (author)

  16. Role of ilmenite micro-inclusion on Fe oxidation states of natural sapphires

    Science.gov (United States)

    Monarumit, N.; Satitkune, S.; Wongkokua, W.

    2017-09-01

    The blue color of blue sapphire is caused by the Fe-Ti pairs. Recently, the oxidation states of Fe and Ti on high-quality blue sapphire were found as mixed acceptor states of Fe3+ and Ti4+. However, the oxidation states of Fe on natural sapphire with some inclusions were reported as mixing of Fe2+ and Fe3+ using the x-ray absorption near edge structure spectroscopy (XANES). Generally, there are mineral inclusions on natural sapphire related to Fe such as hematite (Fe2O3) and ilmenite (FeTiO3). In this study, we investigated the micro-inclusions on natural sapphires by the electron probe micro analyzer (EPMA). The oxidation states of Fe and Fe-O bond length were analyzed by x-ray absorption spectroscopy (XAS). The Fe K-edge extended x-ray absorption fine structure (EXAFS) fitting results focused on the first shell of Fe atoms on high-quality natural sapphires were shown that the Fe-O bond length on α-Al2O3 was fitted well with the Fe-O bond length of Fe2O3 presenting Fe3+. However, the Fe-O bond length on natural sapphires with ilmenite micro-inclusion was fitted with the Fe-O bond length of Fe3O4 showing Fe2+ and Fe3+. As the result, the Fe2+ on natural sapphires was contributed by the ilmenite micro-inclusion.

  17. Simulation and optimization of silicon-on-sapphire pressure sensor

    Science.gov (United States)

    Kulesh, N. A.; Kudyukov, E. V.; Balymov, K. G.; Beloyshov, A. A.

    2017-09-01

    In this paper, finite element analysis software COMSOL Multiphysics was used to simulate the performance of silicon-on-sapphire piezoresistive pressure sensor, aiming to elaborate a flexible model suitable for further optimization and customization of the currently produced pressure sensors. The base model was built around the cylindrical pressure cell made of titanium alloy having a circular diaphragm with monocrystalline sapphire layer attached. The monocrystalline piezoresistive elements were placed on top of the double-layer diaphragm and electrically connected to form the Wheatstone bridge. Verification of the model and parametric study included three main areas: geometrical parameters of the cell, position of the elements on the diaphragm, and operation at elevated temperature. Optimization of the cell geometry included variation of bossed titanium diaphragm parameters as well as rounding-off radiuses near the edges of the diaphragm. Influence of the temperature was considered separately for thermal expansion of the mechanical components and for the changes of electrical and piezoresistive properties of the piezoresistive elements. In conclusion, the simulation results were compared to the experimental data obtained for three different constructions of the commercial pressure sensors produced by SPA of Automatics named after Academician N.A. Semikhatov.

  18. High-temperature sapphire optical sensor fiber coatings

    Science.gov (United States)

    Desu, Seshu B.; Claus, Richard O.; Raheem, Ruby; Murphy, Kent A.

    1990-10-01

    the filter. These modes may be attributed to a number of material degradation mechanisms, such as thermal shock, oxidation corrosion of the material, mechanical loads, or phase changes in the filter material. Development of high temperature optical fiber (sapphire) sensors embedded in the CXF filters would be very valuable for both monitoring the integrity of the filter during its use and understanding the mechanisms of degradation such that durable filter development will be facilitated. Since the filter operating environment is very harsh, the high temperature sapphire optical fibers need to be protected and for some sensing techniques the fiber must also be coated with low refractive index film (cladding). The objective of the present study is to identify materials and develop process technologies for the application of claddings and protective coatings that are stable and compatible with sapphire fibers at both high temperatures and pressures.

  19. Dislocation Velocities and Dislocation Structure in Cubic Zirconia and Sapphire

    Science.gov (United States)

    Farber, Boris Yarovlevick

    The dislocation structure around elevated temperature indentations in 9.4 and 21 mol% rm Y_2O _3 fully-stabilized cubic ZrO_2 (c-ZrO_2) was investigated using selective etching and transmission electron microscopy (TEM). Cracking arising from interaction between slip bands was observed in the 21 mol% rm Y_2O _3 material, and direct evidence of the formation of Lomer type dislocation pile-ups leading to crack nucleation was obtained by TEM. Stress and temperature dependencies of the edge and screw dislocation velocities in c-ZrO_2 were measured. The activation energy for motion of the edge dislocations (5.0 +/- 0.4 eV) is slightly lower than that for screw dislocations (5.6 +/- 0.6 eV). The stress exponent (m) is close to 1 at low temperatures (stress relaxation in the vicinity of room temperature Knoop indents in c-ZrO_2 was investigated using photoelasticity method. A rapid low temperature stress relaxation was observed, and a mechanism was proposed. The temperature dependence of the Vickers hardness was measured on the basal (0001} and pyramidal {11|23} planes of single crystal alpha -Al_2O_3 (sapphire) from room temperature to 1273 K. The plastic zone surrounding the indents was investigated using selective etching and TEM. Indentation was accompanied by three competitive damage processes: fracture, twinning and dislocation plasticity. At room temperature, cracking predominated. At intermediate temperatures, extensive rhombohedral twinning was observed, while at higher temperatures, prismatic slip bands on {11|20} dominated the microstructure. The dislocation substructure at the vicinity of the indents consists of fairly straight dislocations lying on basal and/or prism planes and aligned along crystallographic directions. The details of the glide dissociation of perfect screw dislocations into three collinear partials, the mechanism of the microplasticity of sapphire single crystals, and details of the Peierls potential are discussed. An anomalously high low

  20. Surface study of irradiated sapphires from Phrae Province, Thailand using AFM

    Science.gov (United States)

    Monarumit, N.; Jivanantaka, P.; Mogmued, J.; Lhuaamporn, T.; Satitkune, S.

    2017-09-01

    The irradiation is one of the gemstone enhancements for improving the gem quality. Typically, there are many varieties of irradiated gemstones in the gem market such as diamond, topaz, and sapphire. However, it is hard to identify the gemstones before and after irradiation. The aim of this study is to analyze the surface morphology for classifying the pristine and irradiated sapphires using atomic force microscope (AFM). In this study, the sapphire samples were collected from Phrae Province, Thailand. The samples were irradiated by high energy electron beam for a dose of ionizing radiation at 40,000 kGy. As the results, the surface morphology of pristine sapphires shows regular atomic arrangement, whereas, the surface morphology of irradiated sapphires shows the nano-channel observed by the 2D and 3D AFM images. The atomic step height and root mean square roughness have changed after irradiation due to the micro-structural defect on the sapphire surface. Therefore, this study is a frontier application for sapphire identification before and after irradiation.

  1. CMOS Silicon-on-Sapphire RF Tunable Matching Networks

    Directory of Open Access Journals (Sweden)

    Chamseddine Ahmad

    2006-01-01

    Full Text Available This paper describes the design and optimization of an RF tunable network capable of matching highly mismatched loads to 50 at 1.9 GHz. Tuning was achieved using switched capacitors with low-loss, single-transistor switches. Simulations show that the performance of the matching network depends strongly on the switch performances and on the inductor losses. A 0.5 m silicon-on-sapphire (SOS CMOS technology was chosen for network implementation because of the relatively high-quality monolithic inductors achievable in the process. The matching network provides very good matching for inductive loads, and acceptable matching for highly capacitive loads. A 1 dB compression point greater than dBm was obtained for a wide range of load impedances.

  2. Final EDP Ti: sapphire amplifiers for ELI project

    Science.gov (United States)

    Chvykov, Vladimir; Kalashnikov, Mikhail; Osvay, Károly

    2015-05-01

    Recently several ultrahigh intensity Chirped Pulse Amplification (CPA) laser systems have reached petawatt output powers [1, 2] setting the next milestone at tens or even hundreds petawatts for the next three to ten years [3, 4]. These remarkable results were reached when laser amplifiers (opposite to Optical Parametric Amplification (OPA) [5]) were used as final ones and from them Ti:Sapphire crystals supposed to be the working horses as well in the future design of these laser systems. Nevertheless, the main limitation that arises on the path toward ultrahigh output power and intensity is the restriction on the pumping and extraction energy imposed by Transverse Amplified Spontaneous Emission (TASE) [6] and/or transverse parasitic generation (TPG) [7] within the large aperture of the disc-shape amplifier volume.

  3. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bootkul, D., E-mail: mo_duangkhae@hotmail.com [Department of General Science - Gems & Jewelry, Faculty of Science, Srinakharinwirot University, Bangkok 10110 (Thailand); Chaiwai, C.; Tippawan, U. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wanthanachaisaeng, B. [Gems Enhancement Research Unit, Faculty of Gems, Burapha University, Chanthaburi Campus, Chanthaburi 22170 (Thailand); Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-12-15

    Highlights: • Ion beam analysis is an effective method for detecting trace elements. • Ion beam treatment is able to improve optical and color appearances of the blue sapphire from Rwanda. • These alternative methods can be extended to jewelry industry for large scale application. - Abstract: Blue sapphire is categorised in a corundum (Al{sub 2}O{sub 3}) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV–Vis–NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  4. An ultra-thin compliant sapphire membrane for the growth of less strained, less defective GaN

    Science.gov (United States)

    Moon, Daeyoung; Jang, Jeonghwan; Choi, Daehan; Shin, In-Su; Lee, Donghyun; Bae, Dukkyu; Park, Yongjo; Yoon, Euijoon

    2016-05-01

    An ultra-thin (26 nm) sapphire (Al2O3) membrane was used as a compliant substrate for the growth of high quality GaN. The density of misfit dislocations per unit length at the interface between the GaN layer and the sapphire membrane was reduced by 28% compared to GaN on the conventional sapphire substrate. Threading dislocation density in GaN on the sapphire membrane was measured to be 2.4×108/cm2, which is lower than that for GaN on the conventional sapphire substrate (3.2×108/cm2). XRD and micro-Raman results verifed that the residual stress in GaN on the sapphire membrane was as low as 0.02 GPa due to stress absorption by the ultra-thin compliant sapphire membrane.

  5. Frequency-doubled diode laser for direct pumping of Ti:sapphire lasers

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2012-01-01

    A single-pass frequency doubled high-power tapered diode laser emitting nearly 1.3 W of green light suitable for direct pumping of Ti:sapphire lasers generating ultrashort pulses is demonstrated. The pump efficiencies reached 75 % of the values achieved with a commercial solid-state pump laser....... However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20...... fs are measured. These results open the opportunity of establishing diode laser pumped Ti:sapphire lasers for e.g. biophotonic applications like retinal optical coherence tomography or pumping of photonic crystal fibers for CARS microscopy....

  6. Sapphire decomposition and inversion domains in N-polar aluminum nitride

    Energy Technology Data Exchange (ETDEWEB)

    Hussey, Lindsay, E-mail: lkhussey@ncsu.edu; White, Ryan M.; Kirste, Ronny; Bryan, Isaac; Guo, Wei; Osterman, Katherine; Haidet, Brian; Bryan, Zachary; Bobea, Milena; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Mita, Seiji [HexaTech, Inc., 991 Aviation Pkwy, Suite 800, Morrisville, North Carolina 27560 (United States)

    2014-01-20

    Transmission electron microscopy (TEM) techniques and potassium hydroxide (KOH) etching confirmed that inversion domains in the N-polar AlN grown on c-plane sapphire were due to the decomposition of sapphire in the presence of hydrogen. The inversion domains were found to correspond to voids at the AlN and sapphire interface, and transmission electron microscopy results showed a V-shaped, columnar inversion domain with staggered domain boundary sidewalls. Voids were also observed in the simultaneously grown Al-polar AlN, however no inversion domains were present. The polarity of AlN grown above the decomposed regions of the sapphire substrate was confirmed to be Al-polar by KOH etching and TEM.

  7. Controlling the frequency-temperature sensitivity of a cryogenic sapphire maser frequency standard by manipulating Fe3+ spins in the sapphire lattice

    Science.gov (United States)

    Benmessai, K.; Creedon, D. L.; Le Floch, J.-M.; Tobar, M. E.; Mrad, M.; Bourgeois, P.-Y.; Kersalé, Y.; Giordano, V.

    2012-02-01

    To create a stable signal from a cryogenic sapphire maser frequency standard, the frequency-temperature dependence of the supporting whispering gallery mode must be annulled. We report the ability to control this dependence by manipulating the paramagnetic susceptibility of Fe3+ ions in the sapphire lattice. We show that the maser signal depends on other whispering gallery modes tuned to the pump signal near 31 GHz, and the annulment point can be controlled to exist between 5 and 10 K, depending on the Fe3+ ion concentration and the frequency of the pump. This level of control has not been achieved previously and will allow improvements in the stability of such devices.

  8. High temperature sensing using higher-order-mode rejected sapphire-crystal fiber gratings

    Science.gov (United States)

    Zhan, Chun; Kim, Jae Hun; Lee, Jon; Yin, Stuart; Ruffin, Paul; Luo, Claire

    2007-09-01

    In this paper, we report the fabrication of higher-order-mode rejected fiber Bragg gratings (FBGs) in sapphire crystal fiber using infrared (IR) femtosecond laser illumination. The grating is tested in high temperature furnace up to 1600 degree Celsius. As sapphire fiber is only available as highly multimode fiber, a scheme to filter out higher order modes in favor for the fundamental mode is theoretically evaluated and experimentally demonstrated. The approach is to use an ultra thin sapphire crystal fiber (60 micron in diameter) to decrease the number of modes. The small diameter fiber also enables bending the fiber to certain radius which is carefully chosen to provide low loss for the fundamental mode LP01 and high loss for the other high-order modes. After bending, less-than-2-nm resonant peak bandwidth is achieved. The grating spectrum is improved, and higher resolution sensing measurement can be achieved. This mode filtering method is very easy to implement. Furthermore, the sapphire fiber is sealed with hi-purity alumina ceramic cement inside a flexible high temperature titanium tube, and the highly flexible titanium tube offers a robust packaging to sapphire fiber. Our high temperature sapphire grating sensor is very promising in extremely high temperature sensing application.

  9. Supersmooth and modified surface of sapphire crystals: Formation, characterization, and applications in nanotechnologies

    Science.gov (United States)

    Muslimov, A. E.; Asadchikov, V. E.; Butashin, A. V.; Vlasov, V. P.; Deryabin, A. N.; Roshchin, B. S.; Sulyanov, S. N.; Kanevsky, V. M.

    2016-09-01

    The results of studying the state of the surface of sapphire crystals by a complex of methods in different stages of crystal treatment are considered by an example of preparing sapphire substrates with a supersmooth surface. The possibility of purposefully forming regular micro- and nanoreliefs and thin transition layers using thermal and thermochemical impacts are considered. The advantages of sapphire substrates with a modified surface for forming heteroepitaxial CdTe and ZnO semiconductor films and ordered ensembles of gold nanoparticles are described. The results of the experiments on the application of crystalline sapphire as a material for X-ray optical elements are reported. These elements include total external reflection mirrors and substrates for multilayer mirrors, output windows for synchrotron radiation, and monochromators working in the reflection geometry in X-ray spectrometers. In the latter case, the problems of the defect structure of bulk crystals sapphire and the choice of a method for growing sapphire crystals of the highest structural quality are considered.

  10. Review and perspective: Sapphire optical fiber cladding development for harsh environment sensing

    Science.gov (United States)

    Chen, Hui; Buric, Michael; Ohodnicki, Paul R.; Nakano, Jinichiro; Liu, Bo; Chorpening, Benjamin T.

    2018-03-01

    The potential to use single-crystal sapphire optical fiber as an alternative to silica optical fibers for sensing in high-temperature, high-pressure, and chemically aggressive harsh environments has been recognized for several decades. A key technological barrier to the widespread deployment of harsh environment sensors constructed with sapphire optical fibers has been the lack of an optical cladding that is durable under these conditions. However, researchers have not yet succeeded in incorporating a high-temperature cladding process into the typical fabrication process for single-crystal sapphire fibers, which generally involves seed-initiated fiber growth from the molten oxide state. While a number of advances in fabrication of a cladding after fiber-growth have been made over the last four decades, none have successfully transitioned to a commercial manufacturing process. This paper reviews the various strategies and techniques for fabricating an optically clad sapphire fiber which have been proposed and explored in published research. The limitations of current approaches and future prospects for sapphire fiber cladding are discussed, including fabrication methods and materials. The aim is to provide an understanding of the past research into optical cladding of sapphire fibers and to assess possible material systems for future research on this challenging problem for harsh environment sensors.

  11. Structural and electronic characterization of graphene grown by chemical vapor deposition and transferred onto sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Joucken, Frédéric, E-mail: frederic.joucken@unamur.be; Colomer, Jean-François; Sporken, Robert; Reckinger, Nicolas

    2016-08-15

    Highlights: • CVD graphene is transferred onto sapphire. • Transport measurements reveal relatively low charge carriers mobility. • Scanning probe microscopy experiments reveal the presence of robust contaminant layers between the graphene and the sapphire, responsible for the low carriers mobility. - Abstract: We present a combination of magnetotransport and local probe measurements on graphene grown by chemical vapor deposition on copper foil and subsequently transferred onto a sapphire substrate. A rather strong p-doping is observed (∼9 × 10{sup 12} cm{sup −2}) together with quite low carrier mobility (∼1350 cm{sup 2}/V s). Atomic force and tunneling imaging performed on the transport devices reveals the presence of contaminants between sapphire and graphene, explaining the limited performance of our devices. The transferred graphene displays ridges similar to those observed whilst graphene is still on the copper foil. We show that, on sapphire, these ridges are made of different thicknesses of the contamination layer and that, contrary to what was reported for hBN or certain transition metal dichalcogenides, no self-cleansing process of the sapphire substrate is observed.

  12. Impurity effects on the adhesion of aluminum films on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, J.A.; Guthrie, S.E.; Clift, W.M.; Moody, N.R. [Sandia National Labs., Livermore, CA (United States); Kriese, M.D. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science

    1998-05-01

    The adhesion of aluminum (Al) films onto sapphire substrates in the presence of controlled contaminants is being investigated. In this study, adhesion strength is evaluated by continuous scratch and nanoindentation tests to induce delamination of the Al film from the sapphire substrate. If delamination blisters or spallations can be induced, then fracture mechanics based models can be used to calculate the fracture energy or work of adhesion based on the radius of the blister. Initial specimens of 178 nm thick Al films were vapor deposited onto (0001) oriented sapphire substrates with a 5--19 nm layer of carbon sputter deposited onto the sapphire surface of selected samples. Continuous scratch tests promoted blistering of the film in specimens with carbon on the sapphire surface. Delamination blisters could not be induced by continuous indentation testing in samples with or without carbon at the interface. An overlayer of sputtered tantalum (Ta) was then used on a second set of 500 nm thick Al films with and without 10--20 nm of sputtered carbon on the sapphire surface to promote delaminations. With Ta overlayers, continuous nanoindentation techniques induced larger diameter delamination blisters in the specimens with carbon, than in the specimens without carbon. Resistance to blistering, or smaller induced blisters, indicates a higher interfacial strength.

  13. Self-assembly of gold nanoparticles on a single crystalline sapphire substrate

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Hiroyuki [Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Shirahata, Naoto [International Center for Materials Nanoartchitecgonics (MANA), National Institute of Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Narushima, Takashi [Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Yonezawa, Tetsu, E-mail: tetsu@eng.hokudai.ac.jp [Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer Functionalization of the surface of single crystalline sapphire substrate. Black-Right-Pointing-Pointer Hot hydrogen peroxide makes the surface contact angle of the sapphire substrate smaller according to OH groups on the surface. Black-Right-Pointing-Pointer Silan coupling reagent can be attached to the hydrophilic sapphire substrate surface. Black-Right-Pointing-Pointer Negatively charged gold nanoparticles could be immobilized on the cationic sapphire substrate surface. - Abstract: Single crystalline sapphire is an atomically flat substrate with a high transparency in a wide wavelength region. However, its surface is chemically stable so that the modification by a self-assembled monolayer is somewhat difficult. We have used a H{sub 2}O{sub 2} treatment at 70 Degree-Sign C to activate the surface and modified with a silan coupling reagent. The modification of the surface is discussed with the water contact angle. Immobilization of citrate-stabilized anionic gold nanoparticles on a cationically modified sapphire surface was carried out.

  14. CW STED nanoscopy with a Ti:Sapphire oscillator

    Science.gov (United States)

    Liu, Yujia; Xie, Hao; Alonas, Eric; Santangelo, Philip J.; Jin, Dayong; Xi, Peng

    2012-12-01

    Fluorescence microscopy has become an essential tool to study biological molecules, pathways and events in living cells, tissues and animals. Meanwhile, the conventional optical microscopy is limited by the wavelength of the light. Even the most advanced confocal microscopy or multiphoton microscopy can only yield optical resolution approaching the diffraction limit of ~200 nm. This is still larger than many subcellular structures, which are too small to be resolved in detail. These limitations have driven the development of super-resolution optical imaging methodologies over the past decade. The stimulated emission depletion (STED) microscopy was the first and most direct approach to overcoming the diffraction limit for far-field nanoscopy. Typically, the excitation focus is overlapped by an intense doughnut-shaped spot to instantly de-excite markers from their fluorescent state to the ground state by stimulated emission. This effectively eliminates the periphery of the Point Spread Function (PSF), resulting in a narrower focal region, or super-resolution. Scanning a sharpened spot through the specimen renders images with sub-diffraction resolution. Multi-color STED imaging can present important structural and functional information for protein-protein interaction. In this work, we presented a dual color, synchronization-free STED stimulated emission depletion (STED) microscopy with a Ti:Sapphire oscillator. The excitation wavelengths were 532nm and 635nm, respectively. With pump power of 4.6 W and sample irradiance of 310 mW, we achieved super-resolution as high as 71 nm. We also imaged 200 nm nanospheres as well as all three cytoskeletal elements (microtubules, intermediate filaments, and actin filaments), clearly demonstrating the super-resolution resolving power over conventional diffraction limited imaging. It also allowed us to discover that, Dylight 650, exhibits improved performance over ATTO647N, a fluorophore frequently used in STED. Furthermore, we

  15. SAPPHiRE: a Small Gamma-Gamma Higgs Factory

    CERN Document Server

    Bogacz, S A; Lusito, L; Schulte, D; Takahashi, T; Velasco, M; Zanetti, M; Zimmermann, F

    2012-01-01

    A new particle with mass ~ 125 GeV that resembles the Higgs boson has recently been discovered by ATLAS and CMS. We propose a low-energy gamma-gamma collider as a cost- and time-efficient option for a Higgs factory capable of studying this particle in detail. In the past, this option has been suggested as a possible application of the CLIC two-beam accelerator technology (the CLIC Higgs Experiment, CLICHE) or as an option for the ILC. Here we propose a design based on a pair of \\sim 10 GeV recirculating Linacs (Small Accelerator for Photon-Photon Higgs production using Recirculating Electrons, SAPPHiRE) similar in design to those proposed for the LHeC. We present parameters for the e- beams and sketch a laser backscattering system capable of producing a gamma-gamma peak luminosity of 0.36 \\times 10^34/cm2/s with E_CM (gamma-gamma) \\sim 125 GeV. A gamma-gamma collider with such a luminosity could be used to measure accurately the mass, bbar, WW\\ast, and gamma-gamma decays of the Higgs boson. We also comment on...

  16. BBO sapphire compound for high-power frequency conversion

    Science.gov (United States)

    Rothhardt, Carolin; Rothhardt, Jan; Klenke, Arno; Peschel, Thomas; Eberhardt, Ramona; Limpert, Jens; Tünnermann, Andreas

    2015-02-01

    Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for future high power lasers.

  17. Laser surface and subsurface modification of sapphire using femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Eberle, G., E-mail: eberle@iwf.mavt.ethz.ch [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Schmidt, M. [Chair of Photonic Technologies, University of Erlangen-Nuremberg, Konrad-Zuse-Strasse 3-5, 91052 Erlangen (Germany); Pude, F. [Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland); Wegener, K. [Institute of Machine Tools and Manufacturing, ETH Zurich, Leonhardstrasse 21, 8092 Zurich (Switzerland); Inspire AG, Technoparkstrasse 1, 8005 Zurich (Switzerland)

    2016-08-15

    Highlights: • Single and multipulse ablation threshold of aluminium oxide is determined. • Laser ablation, and in-volume modification followed by wet etching are demonstrated. • Quality following laser processing and laser-material interactions are studied. - Abstract: Two methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.

  18. Overview of the Sapphire payload for space surveillance

    Science.gov (United States)

    Hackett, J.; Brisby, R.; Smith, K.

    2012-06-01

    This paper provides an overview of the satellite based Sapphire Payload developed by COM DEV to be used for observing Resident Space Objects (RSOs) from low earth orbit by the Canadian Department of National Defence. The data from this operational mission will be provided to the US Space Surveillance Network as an international contribution to assist with RSO precision positional determination. The payload consists of two modules; an all reflective visible-band telescope housed with a low noise preamplifier/focal plane, and an electronics module that contains primary and redundant electronics. The telescope forms a low distortion image on two CCDs adjacent to each other in the focal plane, creating a primary image and a redundant image that are offset spatially. This combination of high-efficiency low-noise CCDs with well-proven high-throughput optics provides a very sensitive system with low risk and cost. Stray light is well controlled to allow for observations of very faint objects within the vicinity of the bright Earth limb. Thermally induced aberrations are minimized through the use of an all aluminum construction and the strategic use of thermal coatings. The payload will acquire a series of images for each target and perform onboard image pre-processing to minimize the downlink requirements. Internal calibration sources will be used periodically to check for health of the payload and to identify, and possibly correct, any pixels with an aberrant response. This paper also provides a summary of the testing that was performed and the results achieved.

  19. ZrO2 thin-film-based sapphire fiber temperature sensor.

    Science.gov (United States)

    Wang, Jiajun; Lally, Evan M; Wang, Xiaoping; Gong, Jianmin; Pickrell, Gary; Wang, Anbo

    2012-04-20

    A submicrometer-thick zirconium dioxide film was deposited on the tip of a polished C-plane sapphire fiber to fabricate a temperature sensor that can work to an extended temperature range. Zirconium dioxide was selected as the thin film material to fabricate the temperature sensor because it has relatively close thermal expansion to that of sapphire, but more importantly it does not react appreciably with sapphire up to 1800 °C. In order to study the properties of the deposited thin film, ZrO2 was also deposited on C-plane sapphire substrates and characterized by x-ray diffraction for phase analysis as well as by atomic force microscopy for analysis of surface morphology. Using low-coherence optical interferometry, the fabricated thin-film-based sapphire fiber sensor was tested in the lab up to 1200 °C and calibrated from 200° to 1000 °C. The temperature resolution is determined to be 5.8 °C when using an Ocean Optics USB4000 spectrometer to detect the reflection spectra from the ZrO2 thin-film temperature sensor.

  20. Short-and long-term neural biocompatibility of heparin coated sapphire implants

    Energy Technology Data Exchange (ETDEWEB)

    Wang Anfeng [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); McAllister, James P. [Department of Neurological Surgery, Wayne State University, 4201 Antoine Street, UHC-6E, Detroit, MI 48201 (United States); Finlayson, Paul [Department of Otolaryngology, Wayne State University, 550 E Canfield, Lande Room 327, Detroit, MI 48201 (United States); Li, Jie [Department of Neurological Surgery, Wayne State University, 4201 Antoine Street, UHC-6E, Detroit, MI 48201 (United States); Brabant, Kelley [Department of Neurological Surgery, Wayne State University, 4201 Antoine Street, UHC-6E, Detroit, MI 48201 (United States); Tang Haiying [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Black, Carolyn [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Department of Neurological Surgery, Wayne State University, 4201 Antoine Street, UHC-6E, Detroit, MI 48201 (United States); Cao Ting [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Liang Xuemei [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Salley, Steven O. [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Auner, Gregory W. [Department of Electrical and Computer Engineering, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States); Ng, K.Y. Simon [Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202 (United States)]. E-mail: sng@wayne.edu

    2007-03-15

    Sapphire is one of the most promising materials for the development of implantable biomedical devices due to its exceptional chemical, mechanical, electrical, thermal and optical properties. Silicon has also been widely used to manufacture neuroprosthetic devices in the past. However, both of these materials have been found to cause the most severe tissue reactions while implanted in vivo in the rat brain, compared with other biomaterials. In order to enhance the biocompatibility of sapphire and silicon, their surfaces were modified by depositing a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS), followed by the photo-immobilization of heparin. To comprehensively evaluate the short- and long-term neural biocompatibility, sapphire and silicon wafers (2.5 mm dia x 0.25 mm thick) with and without heparin coating were implanted on the surface of adult rat's cortex for 10, 28 and 90 days. Specific evaluations of the cell types that contribute to an inflammatory response were performed. The histological results indicate that the biocompatibility of sapphire is dramatically improved by heparin immobilization, while this dramatic improvement is not observed on heparin coated silicon. The failure to improve the biocompatibility of silicon by heparin immobilization can be attributed to the corrosion of the silicon surface in vivo, which was confirmed by atomic force microscopy (AFM). Meanwhile, no corrosion was observed on heparin coated sapphire surfaces and a very thin layer of proteins or extracellular matrix was deposited on the surfaces.

  1. Growth and Crystal Orientation of ZnTe on m-Plane Sapphire with Nanofaceted Structure

    Science.gov (United States)

    Nakasu, Taizo; Sun, Wei-Che; Kobayashi, Masakazu; Asahi, Toshiaki

    2017-04-01

    ZnTe thin films on sapphire substrate with nanofaceted structure have been studied. The nanofaceted structure of the m-plane (10-10) sapphire was obtained by heating the substrate at above 1100°C in air, and the r-plane (10-12) and S-plane (1-101) were confirmed. ZnTe layers were prepared on the nanofaceted m-plane sapphire substrates by molecular beam epitaxy (MBE). The effect of the nanofaceted structure on the orientation of the thin films was examined based on x-ray diffraction (XRD) pole figures. Transmission electron microscopy (TEM) was also employed to characterize the interface structures. The ZnTe layer on the nanofaceted m-plane sapphire substrate exhibited (331)-plane orientation, compared with (211)-plane without the nanofaceted structure. After thermal treatment, the m-plane surface vanished and (211) layer could not be formed because of the lack of surface lattice matching. On the other hand, (331)-plane thin film was formed on the nanofaceted m-plane sapphire substrate, since the (111) ZnTe domains were oriented on the S-facet. The orientation of the ZnTe epilayer depended on the atomic ordering on the surface and the influence of the S-plane.

  2. Spectroscopic study of a diffusion-bonded sapphire cell for hot metal vapors.

    Science.gov (United States)

    Sekiguchi, Naota; Sato, Takumi; Ishikawa, Kiyoshi; Hatakeyama, Atsushi

    2018-01-01

    Characteristics of a diffusion-bonded sapphire cell for optical experiments with hot metal vapors were investigated. The sapphire cell consisted of sapphire-crystal plates and a borosilicate-glass tube, which were bonded to each other by diffusion bonding without any binders or glues. The glass tube was attached to a vacuum manifold using the standard method applied in glass processing, filled with a small amount of Rb metal by chasing with a torch, and then sealed. The cell was baked at high temperatures, and optical experiments were then performed using rubidium atoms at room temperature. The sapphire cell was found to be vacuum tight, at least up to 350°C, and the sapphire walls remained clear over all temperatures. From the optical experiments, the generation of a background gas was indicated after baking at 200°C. The background gas pressure was low enough to avoid pressure broadening of absorption lines but high enough to cause velocity-changing collisions of Rb atoms. The generated gas pressure decreased at higher temperatures, probably due to chemical reactions.

  3. Sapphire scintillation tests for cryogenic detectors in the Edelweiss dark matter search

    Energy Technology Data Exchange (ETDEWEB)

    Luca, M

    2007-07-15

    Identifying the matter in the universe is one of the main challenges of modern cosmology and astrophysics. An important part of this matter seems to be made of non-baryonic particles. Edelweiss is a direct dark matter search using cryogenic germanium bolometers in order to look for particles that interact very weakly with the ordinary matter, generically known as WIMPs (weakly interacting massive particles). An important challenge for Edelweiss is the radioactive background and one of the ways to identify it is to use a larger variety of target crystals. Sapphire is a light target which can be complementary to the germanium crystals already in use. Spectroscopic characterization studies have been performed using different sapphire samples in order to find the optimum doping concentration for good low temperature scintillation. Ti doped crystals with weak Ti concentrations have been used for systematic X ray excitation tests both at room temperature and down to 30 K. The tests have shown that the best Ti concentration for optimum room temperature scintillation is 100 ppm and 50 ppm at T = 45 K. All concentrations have been checked by optical absorption and fluorescence. After having shown that sapphire had interesting characteristics for building heat-scintillation detectors, we have tested if using a sapphire detector was feasible within a dark matter search. During the first commissioning tests of Edelweiss-II, we have proved the compatibility between a sapphire heat scintillation detector and the experimental setup. (author)

  4. Nanoscratch Characterization of GaN Epilayers on c- and a-Axis Sapphire Substrates

    Directory of Open Access Journals (Sweden)

    Wen Hua-Chiang

    2010-01-01

    Full Text Available Abstract In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN epilayers on c- and a-axis sapphire substrates and then used the nanoscratch technique and atomic force microscopy (AFM to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies revealed that pile-up phenomena occurred on both sides of the scratches formed on the GaN epilayers. It is suggested that cracking dominates in the case of GaN epilayers while ploughing during the process of scratching; the appearances of the scratched surfaces were significantly different for the GaN epilayers on the c- and a-axis sapphire substrates. In addition, compared to the c-axis substrate, we obtained higher values of the coefficient of friction (μ and deeper penetration of the scratches on the GaN a-axis sapphire sample when we set the ramped force at 4,000 μN. This discrepancy suggests that GaN epilayers grown on c-axis sapphire have higher shear resistances than those formed on a-axis sapphire. The occurrence of pile-up events indicates that the generation and motion of individual dislocation, which we measured under the sites of critical brittle transitions of the scratch track, resulted in ductile and/or brittle properties as a result of the deformed and strain-hardened lattice structure.

  5. Nanoscratch Characterization of GaN Epilayers on c- and a-Axis Sapphire Substrates.

    Science.gov (United States)

    Lin, Meng-Hung; Wen, Hua-Chiang; Jeng, Yeau-Ren; Chou, Chang-Pin

    2010-08-07

    In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN) epilayers on c- and a-axis sapphire substrates and then used the nanoscratch technique and atomic force microscopy (AFM) to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies revealed that pile-up phenomena occurred on both sides of the scratches formed on the GaN epilayers. It is suggested that cracking dominates in the case of GaN epilayers while ploughing during the process of scratching; the appearances of the scratched surfaces were significantly different for the GaN epilayers on the c- and a-axis sapphire substrates. In addition, compared to the c-axis substrate, we obtained higher values of the coefficient of friction (μ) and deeper penetration of the scratches on the GaN a-axis sapphire sample when we set the ramped force at 4,000 μN. This discrepancy suggests that GaN epilayers grown on c-axis sapphire have higher shear resistances than those formed on a-axis sapphire. The occurrence of pile-up events indicates that the generation and motion of individual dislocation, which we measured under the sites of critical brittle transitions of the scratch track, resulted in ductile and/or brittle properties as a result of the deformed and strain-hardened lattice structure.

  6. Temperature and thermal stress evolutions in sapphire crystal during the cooling process by heat exchanger method

    Science.gov (United States)

    Ma, Wencheng; Zhao, Wenhan; Wu, Ming; Ding, Guoqiang; Liu, Lijun

    2017-09-01

    Transient numerical calculations were carried out to predict the evolutions of temperature and thermal stress in sapphire single crystal during the cooling process by heat exchanger method (HEM). Internal radiation in the semitransparent sapphire crystal was taken into account using the finite volume method (FVM) in the global heat transfer model. The numerical results seem to indicate that the narrow bottom region of the sapphire crystal is subjected to high thermal stress during the cooling process, which could be responsible for the seed cracking of the as-grown crystal, while the thermal stress is relatively small in the central main body of the crystal, and is less than 10 MPa during the whole cooling process. The fast decrease of the thermal stress in the bottom region of the crystal during the initial stage of cooling process is dominated by the reduction of the cooling helium gas in the heat exchanger shaft, and is not significantly affected by the heating power reduction rate.

  7. Direct pumping of ultrashort Ti:sapphire lasers by a frequency doubled diode laser

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2011-01-01

    A simple and robust diode laser system emitting 1.28 W of green light suitable for pumping an ultrafast Ti:sapphire laser is presented. To classify our results, the diode laser is compared to a standard, commercially available diode pumped solid-state (DPSS) laser system pumping the same oscillator....... When using our diode laser system, the optical conversion efficiencies from green to near-infrared light reduces to 75 % of the values achieved with the commercial pump laser. Despite this reduction the overall efficiency of the Ti: sapphire laser is still increased by a factor > 2 due to the superior...... electro-optical efficiency of the diode laser. Autocorrelation measurements show that pulse widths of less than 20 fs can be expected with an average power of 52 mW when using our laser. These results indicate the high potential of direct diode laser pumped Ti: sapphire lasers to be used in applications...

  8. Single-crystal sapphire tubes as economical probes for optical pyrometry in harsh environments.

    Science.gov (United States)

    Růžička, Jakub; Houžvička, Jindřich; Bok, Jiří; Praus, Petr; Mojzeš, Peter

    2011-12-20

    One-end-sealed single-crystal sapphire tubes are presented as a simple, robust, and economical alternative for bulky lightpipe probes. Thermal radiation from a blackbody cavity created at the inner surface of the sealed end is gathered by a simple lens-based collecting system and transmitted via optical fiber to the remote detection unit. Simplicity and applicability of the concept are demonstrated by the combination of commercially available sapphire tubes with a common optical pyrometer. Radiation thermometers with sapphire tubes as invasive probes can be useful for applications requiring immunity to electromagnetic interference, resistance to harsh environments, simple replacement in the case of failure, and enhanced mechanical firmness, enabling wider range probe positioning inside the medium of interest.

  9. Single-crystal sapphire tubes as economical probes for optical pyrometry in harsh environments

    Energy Technology Data Exchange (ETDEWEB)

    Ruzicka, Jakub; Houzvicka, Jindrich; Bok, Jiri; Praus, Petr; Mojzes, Peter

    2011-12-20

    One-end-sealed single-crystal sapphire tubes are presented as a simple, robust, and economical alternative for bulky lightpipe probes. Thermal radiation from a blackbody cavity created at the inner surface of the sealed end is gathered by a simple lens-based collecting system and transmitted via optical fiber to the remote detection unit. Simplicity and applicability of the concept are demonstrated by the combination of commercially available sapphire tubes with a common optical pyrometer. Radiation thermometers with sapphire tubes as invasive probes can be useful for applications requiring immunity to electromagnetic interference, resistance to harsh environments, simple replacement in the case of failure, and enhanced mechanical firmness, enabling wider range probe positioning inside the medium of interest.

  10. (211) oriented ZnTe growth on m-plane sapphire by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Nakasu, Taizo [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Tokyo 169-0051 (Japan); Togo, Hiroyoshi [NTT Microsystem Integration Laboratories, Atugi-shi 243-0198 (Japan); Asahi, Toshiaki [Technology Development Center, JX Nippon Mining and Metals Corporation, Hitachi-shi 317-0056 (Japan)

    2013-11-15

    Single-crystalline and single domain ZnTe thin films are sought for high-performance terahertz wave detectors, and ZnTe/sapphire heterostructures were considered since the Electro-Optical (EO) effect could be obtained only from epilayers. ZnTe epilayers were grown on m-plane sapphire substrates by molecular beam epitaxy, and the potential of single domain epilayers was explored. Through the X-ray diffraction pole figure measurement it was confirmed that one (100) oriented ZnTe domain along with two kinds of (211) oriented domains were formed on the m-plane sapphire when the layer was grown at 340 C. When the layer was grown at 350 C, the (211) oriented domain dominated the film. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. 78 FR 56691 - Sapphire Power Marketing LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2013-09-13

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Sapphire Power Marketing LLC; Supplemental Notice That Initial Market-Based... above-referenced proceeding, of Sapphire Power Marketing LLC's application for market-based rate...

  12. High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

    Energy Technology Data Exchange (ETDEWEB)

    Hori, M., E-mail: Masaki.Hori@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik (Germany); Dax, A. [University of Tokyo, Department of Physics (Japan); Soter, A. [Max-Planck-Institut fuer Quantenoptik (Germany)

    2012-12-15

    The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth {Gamma}{sub pl} {approx} 6 MHz, pulse energy 50-100 mJ, and output wavelength {lambda} = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth {Gamma}{sub pl} {approx} 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

  13. High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

    Science.gov (United States)

    Hori, M.; Dax, A.; Soter, A.

    The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth Γpl ˜ 6 MHz, pulse energy 50-100 mJ, and output wavelength λ = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γpl ˜ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

  14. Multiphoton imaging with a novel compact diode-pumped Ti:sapphire oscillator

    DEFF Research Database (Denmark)

    König, Karsten; Andersen, Peter E.; Le, Tuan

    2015-01-01

    Multiphoton laser scanning microscopy commonly relies on bulky and expensive femtosecond lasers. We integrated a novel minimal-footprint Ti:sapphire oscillator, pumped by a frequency-doubled distributed Bragg reflector tapered diode laser, into a clinical multiphoton tomograph and evaluated its...... imaging capability using different biological samples, i.e. cell monolayers, corneal tissue, and human skin. With the novel laser, the realization of very compact Ti:sapphire-based systems for high-quality multiphoton imaging at a significantly size and weight compared to current systems will become...

  15. Shock-induced optical emission and high-pressure phase transformation of sapphire

    Science.gov (United States)

    Zhang, Ning-Chao; Liu, Fu-Sheng; Wang, Wen-Peng; Sun, Yan-Yun; Liu, Qi-Jun; Peng, Xiao-Juan; Chen, Jun-Xiang

    2013-11-01

    Emission from sapphire window material was measured by spontaneous spectroscopic and multi-wavelength pyrometer techniques. The spectral distribution as a function of wavelength fit well to the grey-body spectrum. We analyzed the emissions and discovered that they arise from shear banding, which is a typical thermal radiation. It was found that the color temperature of shocked sapphire changes linearly and regularly with stress increases from 40 GPa to 59 GPa but becomes monotonic for stresses from 87 GPa to 120 GPa. The change in behavior indicates that a shock-induced phase transformation occurs between 59 GPa and 87 GPa.

  16. Shock-induced optical emission and high-pressure phase transformation of sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning-Chao [Laboratory of High Temperature and High Pressure Physics, Southwest Jiaotong University, Chengdu 610031 (China); Liu, Fu-Sheng, E-mail: fusheng_l@sohu.com [Laboratory of High Temperature and High Pressure Physics, Southwest Jiaotong University, Chengdu 610031 (China); Wang, Wen-Peng; Sun, Yan-Yun; Liu, Qi-Jun [Laboratory of High Temperature and High Pressure Physics, Southwest Jiaotong University, Chengdu 610031 (China); Peng, Xiao-Juan; Chen, Jun-Xiang [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621900 (China)

    2013-11-15

    Emission from sapphire window material was measured by spontaneous spectroscopic and multi-wavelength pyrometer techniques. The spectral distribution as a function of wavelength fit well to the grey-body spectrum. We analyzed the emissions and discovered that they arise from shear banding, which is a typical thermal radiation. It was found that the color temperature of shocked sapphire changes linearly and regularly with stress increases from 40 GPa to 59 GPa but becomes monotonic for stresses from 87 GPa to 120 GPa. The change in behavior indicates that a shock-induced phase transformation occurs between 59 GPa and 87 GPa.

  17. Fabrication of three-dimensional autocloned photonic crystal on sapphire substrate.

    Science.gov (United States)

    Ku, Hao Ming; Huang, Chen Yang; Chao, Shiuh

    2011-03-20

    We applied the laser interference lithography method to form a patterned sapphire substrate (PSS). A three-dimensional photonic crystal was formed by autocloning the PSS with alternate Ta2O5/SiO2 coatings. A high total integrated reflectance (TIR) band was obtained around the 410 to 470 nm wavelength range that matched the emission spectrum of the gallium nitride (GaN) light-emitting diode (LED) for application in manipulating the light extraction of the sapphire-based GaN LED.

  18. Design and analysis of large-core single-mode windmill single crystal sapphire optical fiber

    Science.gov (United States)

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2016-06-01

    We present a large-core single-mode "windmill" single crystal sapphire optical fiber (SCSF) design, which exhibits single-mode operation by stripping off the higher-order modes (HOMs) while maintaining the fundamental mode. The "windmill" SCSF design was analyzed using the finite element analysis method, in which all the HOMs are leaky. The numerical simulation results show single-mode operation in the spectral range from 0.4 to 2 μm in the windmill SCSF, with an effective core diameter as large as 14 μm. Such fiber is expected to improve the performance of many of the current sapphire fiber optic sensor structures.

  19. Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar: implications for gem color and genesis

    Science.gov (United States)

    Zaw, Khin; Sutherland, Lin; Yui, Tzen-Fu; Meffre, Sebastien; Thu, Kyaw

    2015-01-01

    Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr3+ yields red in ruby and Fe2+, Fe3+, and Ti4+ ionic interactions color sapphires. A minor ion, V3+ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.

  20. Femtosecond Ti:sapphire cryogenic amplifier with high gain and MHz repetition rate

    DEFF Research Database (Denmark)

    Dantan, Aurelien Romain; Laurat, Julien; Ourjoumtsev, Alexei

    2007-01-01

    We demonstrate high gain amplification of 160-femtosecond pulses in a compact double-pass cryogenic Ti:sapphire amplifier. The setup involves a negative GVD mirrors recompression stage, and operates with a repetition rate between 0.2 and 4 MHz with a continuous pump laser. Amplification factors...

  1. Deep-ultraviolet frequency metrology with a narrowband titanium:sapphire laser

    NARCIS (Netherlands)

    Hannemann, S.

    2007-01-01

    Within the framework of this thesis resaerch project a narrow band titanium:sapphire laser was built. It provides nanosecond pulses that are subsequently upconverted to the deep ultraviolet frequency range. Absolute frequency calibration is achieved by linking the injection seeding light to a

  2. Intensity Noise Transfer Through a Diode-pumped Titanium Sapphire Laser System

    DEFF Research Database (Denmark)

    Tawfieq, Mahmoud; Hansen, Anders Kragh; Jensen, Ole Bjarlin

    2017-01-01

    In this paper, we investigate the noise performance and transfer in a titanium sapphire (Ti:S) laser system. This system consists of a DBR tapered diode laser, which is frequency doubled in two cascaded nonlinear crystals and used to pump the Ti:S laser oscillator. This investigation includes...

  3. Line beam processing for laser lift-off of GaN from sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Delmdahl, Ralph; Paetzel, Rainer; Brune, Jan; Senczuk, Rolf [Coherent GmbH, Hans-Boeckler-Str. 12, 37079 Goettingen (Germany); Gossler, Christian; Moser, Ruediger; Kunzer, Michael; Schwarz, Ulrich T. [Fraunhofer Institute for Applied Solid State Physics IAF, Tullastr. 72, 79108 Freiburg (Germany)

    2012-12-15

    Gallium nitride (GaN) layers grown on sapphire substrate wafers have been successfully separated using a novel line beam laser lift-off (LLO) approach. The absorption of the 248 nm excimer laser radiation by the GaN through the sapphire wafer results in the formation of metallic gallium and nitrogen gas. The sapphire wafer was easily removable by heating above the gallium melting point. The metallic gallium phase has been inspected via diverse microscopic surface analysis techniques after line beam LLO processing. The measurements indicate that the sapphire separation process using line beam laser scanning has only a marginal impact on the structural quality of the GaN layer. Line beam LLO processing has inherent upscaling advantages over conventional square field LLO. Processing results are evaluated in view of aptness for mass production of high brightness light emitting diodes (HB-LEDs). Differential interference contrast image of GaN film after 248-nm LLO with line beam (A) and square beam (B). (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Theoretical studies on lattice-oriented growth of single-walled carbon nanotubes on sapphire

    Science.gov (United States)

    Li, Zhengwei; Meng, Xianhong; Xiao, Jianliang

    2017-09-01

    Due to their excellent mechanical and electrical properties, single-walled carbon nanotubes (SWNTs) can find broad applications in many areas, such as field-effect transistors, logic circuits, sensors and flexible electronics. High-density, horizontally aligned arrays of SWNTs are essential for high performance electronics. Many experimental studies have demonstrated that chemical vapor deposition growth of nanotubes on crystalline substrates such as sapphire offers a promising route to achieve such dense, perfectly aligned arrays. In this work, a theoretical study is performed to quantitatively understand the van der Waals interactions between SWNTs and sapphire substrates. The energetically preferred alignment directions of SWNTs on A-, R- and M-planes and the random alignment on the C-plane predicted by this study are all in good agreement with experiments. It is also shown that smaller SWNTs have better alignment than larger SWNTs due to their stronger interaction with sapphire substrate. The strong vdW interactions along preferred alignment directions can be intuitively explained by the nanoscale ‘grooves’ formed by atomic lattice structures on the surface of sapphire. This study provides important insights to the controlled growth of nanotubes and potentially other nanomaterials.

  5. Laser-assisted microstructuring for Ti:sapphire channel-waveguide fabrication

    NARCIS (Netherlands)

    Crunteanu, A.; Pollnau, Markus; Jänchen, G.; Hibert, C.; Hoffmann, P.; Salathé, R.P.; Eason, R.W.; Shepherd, D.P.

    2003-01-01

    We report on the fabrication of Ti:sapphire channel waveguides. Such channel waveguides are of interest, e.g., as low-threshold tunable lasers. We investigated several structuring methods including ion beam implantation followed by wet chemical etching strip loading by polyimide spin coating and

  6. Characteristics of nucleation layer and epitaxy in GaN/sapphire heterostructures

    Science.gov (United States)

    Narayan, J.; Pant, Punam; Chugh, A.; Choi, H.; Fan, J. C. C.

    2006-03-01

    We present the details of GaN nucleation layer grown on (0001) sapphire substrates below 600 °C by metal organic chemical vapor deposition. These films have cubic (c-GaN) zinc blende structure which starts to transform into a hexagonal (h-GaN) wurtzite structure upon annealing around 650 °C and above. The films deposited above 700 °C by pulsed laser deposition directly on sapphire substrate showed the wurtzite structure. Both c-GaN and h-GaN films grow epitaxially on (0001) sapphire substrates via domain matching epitaxy, where integral multiples of planes match across the film-substrate interface. The c-GaN has the following epitaxial relationship: c-GaN∥sap, c-GaN∥sap, and c-GaN∥sap. In terms of planar matching, (220) planes of c-GaN match with (30-30) planes of sapphire, and 1/3(422) planes of c-GaN match with (-2110) planes of sapphire in the perpendicular direction. The transformation from c-GaN into h-GaN involves the transformation of (220) planes of c-GaN into (-2110) planes of h-GaN and 1/3(422) planes of c-GaN into (30-30) planes of h-GaN, and the epitaxial relationship changes to h-GaN∥sap and h-GaN∥sap. In terms of planar matching epitaxy, (-2110) planes of h-GaN match with (30-30) planes of sapphire, and, in the perpendicular direction, (30-30) planes of h-GaN match with (-2110) planes of sapphire. This epitaxial relationship is known as 30° or 90° rotation. It is interesting to note that relative spacing for c-GaN as well as h-GaN planes remains the same during this transformation because of a(c-GaN)=√2a(h-GaN)=√3c(h-GaN)/2 equivalence between lattice constants of cubic and hexagonal structures. The transformation from cubic to hexagonal structure can occur via insertion or removal of stacking faults in {111} planes of c-GaN and {0001} planes of h-GaN. The hexagonal structure is preferred as a template for higher-temperature growth, however, the cubic structure, which is a defective hexagonal with stacking faults in alternate layers

  7. Testing of Sapphire Optical Fiber and Sensors in Intense Radiation Fields When Subjected to Very High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Blue, Thomas [The Ohio State Univ., Columbus, OH (United States); Windl, Wolfgang [The Ohio State Univ., Columbus, OH (United States)

    2017-12-15

    The primary objective of this project was to determine the optical attenuation and signal degradation of sapphire optical fibers & sensors (temperature & strain), in-situ, operating at temperatures up to 1500°C during reactor irradiation through experiments and modeling. The results will determine the feasibility of extending sapphire optical fiber-based instrumentation to extremely high temperature radiation environments. This research will pave the way for future testing of sapphire optical fibers and fiber-based sensors under conditions expected in advanced high temperature reactors.

  8. Promising new wavelengths for multi-photon microscopy: thinking outside the Ti:Sapphire box

    Science.gov (United States)

    Norris, Greg; Amor, Rumelo; Dempster, John; Amos, William B.; McConnell, Gail

    2013-02-01

    Multi-photon excitation (MPE) imaging is dominated by the Ti:Sapphire laser as the source for excitation. However, it is limited when considering 3PE of common fluorophores and efficient 2PE of UV dyes which require wavelengths beyond the range of the Ti:Sapphire. Two ultra-short pulsed sources are presented as alternatives: a novel optical parametric oscillator (OPO) geometry (1400-1600nm) and the sum-frequency mixing of an OPO and Yb-doped fibre laser, providing a tunable output (626-635nm). For long wavelengths, we report three-photon laser scanning microscopy (3PLSM) using a bi-directional pumped optical parametric oscillator (OPO) with signal wavelength output at 1500 nm. This novel laser was used to overcome the high optical loss in the infrared spectral region observed in laser scanning microscopes and objective lenses that renders them otherwise difficult to use for imaging. To test our system, we performed 3PLSM auto-fluorescence imaging of live plant cells at 1500 nm, specifically Spirogyra, and compared performance with two-photon excitation (2PLSM) imaging using a femtosecond pulsed Ti:Sapphire laser at 780 nm. Analysis of cell viability based on cytoplasmic organelle streaming and structural changes of cells revealed that at similar peak powers, 2PLSM caused gross cell damage after 5 minutes but 3PLSM showed little or no interference with cell function after 15 minutes. The 1500 nm OPO was thus shown to be a practical laser source for live cell imaging. For short wavelengths, we report the use of an all-solid-state ultra-short pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involved sumfrequency mixing of the output from the long-wavelength OPO described above with residual pump radiation to generate fs-pulsed output in the red spectral region. We demonstrated the performance of our ultra-short pulsed system using fluorescently labelled and autofluorescent tissue

  9. Effect of nitridation on the MOVPE growth of InN on c-, r- and a-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Solopow, Sergej; Dinh, Duc; Pristovsek, Markus; Kneissl, Michael [TU Berlin, Institute of Solid State Physics, Hardenbergstr. 36, 10623 Berlin (Germany)

    2011-07-01

    Growth of high quality InN is still challenging because of a narrow growth window and lack of suitable substrates. We report on the growth of InN on different oriented sapphire substrates, i.e. a-plane (11 anti 20), c-plane (0001), m-plane (10 anti 10) and r-plane (10 anti 12) using metalorganic vapor phase epitaxy (MOVPE). To grow InN directly on the sapphire substrate, a nitridation process is used to improve crystallinity and optical properties. We have grown InN layers after nitridation for 2min at different temperatures from 500 C to 1050 C. We found that the nitridation temperature strongly affects the morphology as well as the orientation of InN layers. Atomic force microscopic (AFM) measurements on the grown samples showed smoother surfaces at higher nitridation temperatures. c-oriented InN was grown on c-plane sapphire with in-plane relationship of [10 anti 10] parallel [11 anti 20]{sub Sapphire}. On the a-plane sapphire we obtained c-oriented InN with in-plane relationship of [1 anti 100]{sub InN} parallel [0001]{sub Sapphire} and [11 anti 20]{sub InN} parallel [1 anti 100]{sub Sapphire} at nitridation temperature higher than 900 C and additional in-plane relationship by temperatures below 900 C. We have grown also a-oriented InN on r-plane sapphire at nitridation temperature higher than 800 {sup circle} C. At nitridation temperatures below 800 C this orientation disappears.

  10. Oscillatory Mass Transport in Vapor-Liquid-Solid Growth of Sapphire Nanowires

    Science.gov (United States)

    Oh, Sang Ho; Chisholm, Matthew F.; Kauffmann, Yaron; Kaplan, Wayne D.; Luo, Weidong; Rühle, Manfred; Scheu, Christina

    2010-10-01

    In vapor-liquid-solid (VLS) growth, the liquid phase plays a pivotal role in mediating mass transport from the vapor source to the growth front of a nanowire. Such transport often takes place through the liquid phase. However, we observed by in situ transmission electron microscopy a different behavior for self-catalytic VLS growth of sapphire nanowires. The growth occurs in a layer-by-layer fashion and is accomplished by interfacial diffusion of oxygen through the ordered liquid aluminum atoms. Oscillatory growth and dissolution reactions at the top rim of the nanowires occur and supply the oxygen required to grow a new (0006) sapphire layer. A periodic modulation of the VLS triple-junction configuration accompanies these oscillatory reactions.

  11. Structural, transport and microwave properties of 123/sapphire films: Thickness effect

    Energy Technology Data Exchange (ETDEWEB)

    Predtechensky, MR.; Smal, A.N.; Varlamov, Y.D. [Institute of Thermophysics, Novosibirsk (Russian Federation)] [and others

    1994-12-31

    The effect of thickness and growth conditions on the structure and microwave properties has been investigated for the 123/sapphire films. It has been shown that in the conditions of epitaxial growth and Al atoms do not diffuse from substrate into the film and the films with thickness up to 100nm exhibit the excellent DC properties. The increase of thickness of GdBaCuO films causes the formation of extended line-mesh defects and the increase of the surface resistance (R{sub S}). The low value of surface resistance R{sub S}(75GHz,77K)=20 mOhm has been obtained for the two layer YBaCuO/CdBaCuO/sapphire films.

  12. GaN layer growth by HVPE on m-plane sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Usikov, Alexander; Shapovalov, Lisa; Ivantsov, Vladimir; Kovalenkov, Oleg; Syrkin, Alexander [Technologies and Devices International an Oxford Instruments Company, 12214 Plum Orchard Dr., Silver Spring, MD 20904 (United States); Spiberg, Philippe; Brown, Robert [Ostendo Technologies, Inc., 6185 Paseo del Norte, Suite 200, Carlsbad, CA 92011 (United States)

    2009-06-15

    Semipolar GaN layers were grown on m-plane sapphire substrates by HVPE. Insertion of Al{sub x}Ga{sub 1-x}N (x{proportional_to}0.1-0.6) layer in-between m-plane sapphire substrate and GaN layer promoted to improve crystalline quality and to grow of semipolar (11-22) plane GaN layers. X-ray diffraction (11-22){omega}-scan rocking curve FWHM of 298 arcsec was measured for a 30 {mu}m thick (11-22)GaN layer. Depending on growth conditions, m-plane GaN layer having micro-crystallites of other orientations (mainly of (11-24) plane GaN layer) was also grown. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Two dimensional imaging by series-connected STJs with sapphire absorber

    CERN Document Server

    Kushino, A; Yamasaki, N Y; Ohashi, T; Kurakado, M

    2002-01-01

    The position determination capability of the series-connected superconducting tunnel junctions (STJs) with Nb/Al/AlO sub x /Al/Nb junctions as a radiation detector is reported. Four groups of series-connected STJs are fabricated on a single crystal of sapphire substrate surrounding 3.5x3.5 mm sup 2 detection area. The signals detected by two STJs with 1.5 mm separation give a time delay caused by the propagation of phonons, and this enables us to measure the irradiated position. Using alpha-particles of 5.5 MeV, we clearly distinguished the incident positions with a potential resolution of 0.16+-0.07 mm (FWHM). Directional dependence in the phonon propagation in the sapphire substrate is not detected.

  14. Development of Cr,Nd:GSGG laser as a pumping source of Ti:sapphire laser

    Energy Technology Data Exchange (ETDEWEB)

    Tamura, Koji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Arisawa, Takashi

    1999-08-01

    Since efficiency of Cr,Nd doped gadolinium scandium gallium garnet (GSGG) laser is in principle higher than that of Nd:YAG laser, it can be a highly efficient pumping source for Ti:sapphire laser. We have made GSGG laser, and measured its oscillation properties. It was two times more efficient than Nd:YAG laser at free running mode operation. At Q-switched mode operation, fundamental output of 50 mJ and second harmonics output of 8 mJ were obtained. The developed laser had appropriate spatial profile, temporal duration, long time stability for solid laser pumping. Ti:sapphire laser oscillation was achieved by the second harmonics of GSGG laser. (author)

  15. Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Prokhorov, I. A.; Zakharov, B. G., E-mail: zakharov@kaluga.rosmail.com [Russian Academy of Sciences, Research Center Space Materials Science, Shubnikov Institute of Crystallography (Kaluga Branch) (Russian Federation); Asadchikov, V. E.; Butashin, A. V.; Roshchin, B. S.; Tolstikhina, A. L. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Zanaveskin, M. L.; Grishchenko, Yu. V.; Muslimov, A. E. [Russian Research Center Kurchatov Institute (Russian Federation); Yakimchuk, I. V.; Volkov, Yu. O.; Kanevskii, V. M.; Tikhonov, E. O. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2011-05-15

    The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.

  16. Multi-microjoule, MHz repetition rate Ti:sapphire ultrafast regenerative amplifier system.

    Science.gov (United States)

    Zhang, Xiaoshi; Schneider, Eric; Taft, Greg; Kaptyen, Henry; Murnane, Margaret; Backus, Sterling

    2012-03-26

    We demonstrate a cryogenically cooled Ti:sapphire ultrafast regenerative amplifier laser system producing >20 μJ energies at 50 kHz, >12 μJ at 200 kHz and >3.5 μJ at 1MHz with repetition rates continuously tunable from 50 kHz up to 1.7 MHz in a footprint of only 60x180 cm². This laser uses down-chirped pulse amplification employing a grism stretcher and a glass-block compressor, achieving sub-60-fs pulse duration. This laser represents a several-times improvement in repetition-rate and average power over past Ti:sapphire-based ultrafast lasers in this class. We discuss the unique challenges and solutions for this laser system. This laser system has wide applications especially in ultrafast photoemission, nonlinear imaging and spectroscopy, as well as for micro/nano-machining and ultrafast laser therapy and surgery.

  17. Microstructures of GaN islands on a stepped sapphire surface

    Science.gov (United States)

    Kim, C. C.; Je, J. H.; Ruterana, P.; Degave, F.; Nouet, G.; Yi, M. S.; Noh, D. Y.; Hwu, Y.

    2002-04-01

    We investigated the structural evolution of GaN nucleation layers in the initial growth stages on commercial c-plane sapphires with atomic steps at the surface, using field-emission scanning electron microscopy, synchrotron x-ray scattering, and high-resolution electron microscopy. GaN nucleates into islands preferentially on the atomic steps. The initial small islands of 25 Å high have well-ordered cubic sequences and nearly coherent interfacial structures with a large compressive strain of ˜10%. As the islands grow to 50 Å high, the strain is drastically reduced, to less than 1%, by generating misfit dislocations at the interface and forming the six-to-seven matched interfacial structure. Interestingly, stacking faults are developed from the GaN/sapphire interface, which induces a cubic-hexagonal transformation. The changes in the stacking order during the initial growth are investigated quantitatively.

  18. Structural, transport and microwave properties of 123/sapphire films: Thickness effect

    Science.gov (United States)

    Predtechensky, M. R.; Smal, A. N.; Varlamov, Yu. D.; Vatnik, S. M.; Tukhto, O. M.; Vasileva, I. G.

    1995-01-01

    The effect of thickness and growth conditions on the structure and microwave properties has been investigated for the 123/sapphire films. It has been shown that in the conditions of epitaxial growth the Al atoms do not diffuse from substrate into the film and the films with thickness up to 100 nm exhibit the excellent direct current (DC) properties. The increase of thickness of GdBaCuO films causes the formation of extended line-mesh defects and the increase of the surface resistance (R(sub S)). The low value of surface resistance R(sub S)(75 GHz, 77K) = 20 mOhm has been obtained for the two layer YBaCuO/CdBaCuO/sapphire films.

  19. Synthesis and Transfer of Large-Area Monolayer WS2 Crystals: Moving Toward the Recyclable Use of Sapphire Substrates.

    Science.gov (United States)

    Xu, Zai-Quan; Zhang, Yupeng; Lin, Shenghuang; Zheng, Changxi; Zhong, Yu Lin; Xia, Xue; Li, Zhipeng; Sophia, Ponraj Joice; Fuhrer, Michael S; Cheng, Yi-Bing; Bao, Qiaoliang

    2015-06-23

    Two-dimensional layered transition metal dichalcogenides (TMDs) show intriguing potential for optoelectronic devices due to their exotic electronic and optical properties. Only a few efforts have been dedicated to large-area growth of TMDs. Practical applications will require improving the efficiency and reducing the cost of production, through (1) new growth methods to produce large size TMD monolayer with less-stringent conditions, and (2) nondestructive transfer techniques that enable multiple reuse of growth substrate. In this work, we report to employ atmospheric pressure chemical vapor deposition (APCVD) for the synthesis of large size (>100 μm) single crystals of atomically thin tungsten disulfide (WS2), a member of TMD family, on sapphire substrate. More importantly, we demonstrate a polystyrene (PS) mediated delamination process via capillary force in water which reduces the etching time in base solution and imposes only minor damage to the sapphire substrate. The transferred WS2 flakes are of excellent continuity and exhibit comparable electron mobility after several growth cycles on the reused sapphire substrate. Interestingly, the photoluminescence emission from WS2 grown on the recycled sapphire is much higher than that on fresh sapphire, possibly due to p-type doping of monolayer WS2 flakes by a thin layer of water intercalated at the atomic steps of the recycled sapphire substrate. The growth and transfer techniques described here are expected to be applicable to other atomically thin TMD materials.

  20. Advances in Trace Element “Fingerprinting” of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar

    OpenAIRE

    Sutherland, F.; Zaw, Khin; Meffre, Sebastien; Yui, Tzen-Fui; Thu, Kyaw

    2014-01-01

    Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method) and oxygen isotope values (δ18O, by laser fluorination). The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and ...

  1. Vortex Ti:Sapphire laser by using an intracavity spot-defect spatial filter

    Science.gov (United States)

    Tan, Shiwen; Zhou, Changhe; Shirakakwa, Akira; Ueda, Ken-ichi; Li, Jianlang

    2017-11-01

    We demonstrated an LG01-mode vortex Ti:Sapphire laser by utilizing an intracavity spot defect for spatial filtering. At the 140-μm diameter of spot defect, the power of vortex laser output reached 135 mW, and the slope efficiency of laser was 17.7%. The effects of the sizes of spot defects on the transverse laser modes and laser powers were also discussed.

  2. Influence of annealing on polymeric precursor derived ZnO thin films on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Choppali, Uma, E-mail: umachoppali@gmail.com [Department of Mathematics and Science, Collin College, Frisco, TX 75035 (United States); Kougianos, Elias; Mohanty, Saraju P. [NanoSystem Design Laboratory (NSDL), University of North Texas, Denton, TX 76203 (United States); Gorman, Brian P. [Colorado Center for Advanced Ceramics, Dept. of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401 (United States)

    2013-10-31

    Zinc oxide (ZnO) thin films on c-sapphire substrates were synthesized by spin-coating aqueous polymeric precursors. The effects of annealing at 1000 °C on crystallinity, surface morphology, and optical properties of ZnO thin films, with varying thicknesses, were studied. Single-layered ZnO thin films are polycrystalline with wurtzite structure and preferentially oriented along the (002) plane. X-ray diffraction pattern also reveals the presence of spinel zinc aluminate (ZnAl{sub 2}O{sub 4}) peaks. ZnO films have highly faceted granular morphology. Multilayered ZnO films, annealed twice at 1000 °C, do not exhibit any ZnO peaks but only ZnAl{sub 2}O{sub 4} peaks. Moreover, the surface morphology was smooth with ridges. These films do not exhibit the band gap or ultra-violet emission photoluminescence characteristics of ZnO. On annealing, there is an interfacial reaction between ZnO and sapphire resulting in ZnAl{sub 2}O{sub 4}. - Highlights: • Multilayer polymeric precursor derived ZnO film is annealed at 1000 °C on c-sapphire. • X-Ray diffraction (XRD) pattern of ZnO film annealed at 1000 °C shows ZnO peaks. • XRD pattern of ZnO films twice-annealed at 1000 °C shows only ZnAl{sub 2}O{sub 4} peaks. • Optical characterization of the multilayered films does not show ZnAl{sub 2}O{sub 4} peaks. • On annealing twice at 1000 °C, ZnO reacts with the c-sapphire to form ZnAl{sub 2}O{sub 4}.

  3. Bi-wavelength operation of a short-pulse Ti:sapphire laser

    Energy Technology Data Exchange (ETDEWEB)

    Barros, M.R.X. de; Becker, P.C. [AT and T Bell Labs., Murray Hill, NJ (United States)

    1994-12-31

    The authors have demonstrated a femtosecond mode locked Ti:sapphire laser that simultaneously generates synchronous and colinear near transform limited two color pulses. The two color operating was obtained from a single laser cavity and the separation between the two wavelengths can be tuned from 55 to 90 nm. This laser is ideally suited for the generation of femtosecond mid-infrared pulses by difference frequency mixing.

  4. Influence of TMAl preflow on AlN epitaxy on sapphire

    KAUST Repository

    Sun, Haiding

    2017-05-12

    The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon\\'s significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.

  5. Metalorganic vapor phase epitaxy of AlN on sapphire with low etch pit density

    Science.gov (United States)

    Koleske, D. D.; Figiel, J. J.; Alliman, D. L.; Gunning, B. P.; Kempisty, J. M.; Creighton, J. R.; Mishima, A.; Ikenaga, K.

    2017-06-01

    Using metalorganic vapor phase epitaxy, methods were developed to achieve AlN films on sapphire with low etch pit density (EPD). Key to this achievement was using the same AlN growth recipe and only varying the pre-growth conditioning of the quartz-ware. After AlN growth, the quartz-ware was removed from the growth chamber and either exposed to room air or moved into the N2 purged glove box and exposed to H2O vapor. After the quartz-ware was exposed to room air or H2O, the AlN film growth was found to be more reproducible, resulting in films with (0002) and (10-12) x-ray diffraction (XRD) rocking curve linewidths of 200 and 500 arc sec, respectively, and EPDs NH3 on the quartz-ware surfaces generated AlN films with higher EPDs. The presence of these residual TMAl/NH3-derived coatings in metalorganic vapor phase epitaxy (MOVPE) systems and their impact on the sapphire surface during heating might explain why reproducible growth of AlN on sapphire is difficult.

  6. Layered MoS{sub 2} grown on c-sapphire by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Yen-Teng; Ma, Chun-Hao; Luong, Tien-Tung; Wei, Lin-Lung; Yen, Tzu-Chun; Chu, Yung-Ching; Tu, Yung-Yi [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu (China); Hsu, Wei-Ting; Chang, Wen-Hao [Department of Electrophysics, National Chiao Tung University, Hsinchu (China); Pande, Krishna Prasad [Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu (China); Chang, Edward Yi [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu (China); Department of Electronics Engineering, National Chiao Tung University, Hsinchu (China)

    2015-03-01

    Layered growth of molybdenum disulphide (MoS{sub 2}) was successfully achieved by pulsed laser deposition (PLD) method on c -plane sapphire substrate. Growth of monolayer to a few monolayer MoS{sub 2}, dependent on the pulsed number of excimer laser in PLD is demonstrated, indicating the promising controllability of layer growth. Among the samples with various pulse number deposition, the frequency difference (A{sub 1g}-E{sup 1}{sub 2g}) in Raman analysis of the 70 pulse sample is estimated as 20.11 cm{sup -1}, suggesting a monolayer MoS{sub 2} was obtained. Two-dimensional (2D) layer growth of MoS{sub 2} is confirmed by the streaky reflection high energy electron diffraction (RHEED) patterns during growth and the cross-sectional view of transmission electron microscopy (TEM). The in-plane relationship, (0006) sapphire//(0002)MoS{sub 2} and [2 anti 1 anti 10] sapphire//[0 anti 1 anti 10]MoS{sub 2} is determined. The results imply that PLD is suitable for layered MoS{sub 2} growth. Additionally, the oxide states of Mo 3d core level spectra of PLD grown MoS{sub 2}, analysed by X-ray photoelectron spectroscopy (XPS), can be effectively reduced by adopting a post sulfurization process. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. High-quality AlN grown on a thermally decomposed sapphire surface

    Science.gov (United States)

    Hagedorn, S.; Knauer, A.; Brunner, F.; Mogilatenko, A.; Zeimer, U.; Weyers, M.

    2017-12-01

    In this study we show how to realize a self-assembled nano-patterned sapphire surface on 2 inch diameter epi-ready wafer and the subsequent AlN overgrowth both in the same metal-organic vapor phase epitaxial process. For this purpose in-situ annealing in H2 environment was applied prior to AlN growth to thermally decompose the c-plane oriented sapphire surface. By proper AlN overgrowth management misoriented grains that start to grow on non c-plane oriented facets of the roughened sapphire surface could be overcome. We achieved crack-free, atomically flat AlN layers of 3.5 μm thickness. The layers show excellent material quality homogeneously over the whole wafer as proved by the full width at half maximum of X-ray measured ω-rocking curves of 120 arcsec to 160 arcsec for the 002 reflection and 440 arcsec to 550 arcsec for the 302 reflection. The threading dislocation density is 2 ∗ 109 cm-2 which shows that the annealing and overgrowth process investigated in this work leads to cost-efficient AlN templates for UV LED devices.

  8. High-temperature sensor instrumentation with a thin-film-based sapphire fiber.

    Science.gov (United States)

    Guo, Yuqing; Xia, Wei; Hu, Zhangzhong; Wang, Ming

    2017-03-10

    A novel sapphire fiber-optic high-temperature sensor has been designed and fabricated based on blackbody radiation theory. Metallic molybdenum has been used as the film material to develop the blackbody cavity, owing to its relatively high melting point compared to that of sapphire. More importantly, the fabrication process for the blackbody cavity is simple, efficient, and economical. Thermal radiation emitted from such a blackbody cavity is transmitted via optical fiber to a remote place for detection. The operating principle, the sensor structure, and the fabrication process are described here in detail. The developed high-temperature sensor was calibrated through a calibration blackbody furnace at temperatures from 900°C to 1200°C and tested by a sapphire crystal growth furnace up to 1880°C. The experimental results of our system agree well with those from a commercial Rayteck MR1SCCF infrared pyrometer, and the maximum residual is approximately 5°C, paving the way for high-accuracy temperature measurement especially for extremely harsh environments.

  9. Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate

    Science.gov (United States)

    Shin, Hui-Youn; Kwon, S. K.; Chang, Y. I.; Cho, M. J.; Park, K. H.

    2009-08-01

    The threading dislocation (TD) density in GaN films grown directly on flat sapphire substrates is typically >10 10/cm 2, which can deteriorate the properties of GaN-based LEDs significantly. This paper reports an approach to reducing the TD density in a GaN layer using a variety of patterned sapphire substrates (PSS). A cone-shaped PSS produced by metal organic chemical vapor deposition (MOVCD) was used for GaN deposition. Three types of GaN specimens were prepared at the initial nucleation stage, middle growth stage and final growth stage. The TDs generated on the cone-shaped PSS were analyzed by transmission electron microscopy (TEM) and a strain mapping simulation using HRTEM images, which evaluated the residual strain distribution. A large number of TDs were generated and the residual strain by the lattice distortions remained above the top of the cone-shaped regions. However, no TDs and residual strain were observed at the slope of the cone-shaped regions. This might be due to the formation of a GaN layer by lateral overgrowth at the slope of the cone-shaped regions, resulting in less lattice mismatch and incoherency between the GaN and sapphire. In conclusion, the TD density in the GaN layer could be reduced significantly, approximately 10 7/cm 2, using the cone-shaped PSS.

  10. Sapphire: a better material for atomization and in situ collection of silver volatile species for atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Musil, Stanislav, E-mail: stanomusil@biomed.cas.cz; Matoušek, Tomáš; Dědina, Jiří

    2015-06-01

    Sapphire is presented as a high temperature and corrosion resistant material of an optical tube of an atomizer for volatile species of Ag generated by the reaction with NaBH{sub 4}. The modular atomizer design was employed which allowed to carry out the measurements in two modes: (i) on-line atomization and (ii) in situ collection (directly in the optical tube) by means of excess of O{sub 2} over H{sub 2} in the carrier gas during the trapping step and vice versa in the volatilization step. In comparison with quartz atomizers, the sapphire tube atomizer provides a significantly increased atomizer lifetime as well as substantially improved repeatability of the Ag in situ collection signals shapes. In situ collection of Ag in the sapphire tube atomizer was highly efficient (> 90%). Limit of detection in the on-line atomization mode and in situ collection mode, respectively, was 1.2 ng ml{sup −1} and 0.15 ng ml{sup −1}. - Highlights: • Sapphire was tested as a new material of an atomizer tube for Ag volatile species. • Two measurement modes were investigated: on-line atomization and in situ collection. • In situ collection of Ag was highly efficient (> 90%) with LOD of 0.15 ng ml{sup −1}. • No devitrification of the sapphire tube observed in the course of several months.

  11. Characteristics of surface acoustic waves in (11\\bar 2 0)ZnO film/ R-sapphire substrate structures

    Science.gov (United States)

    Wang, Yan; Zhang, ShuYi; Xu, Jing; Xie, YingCai; Lan, XiaoDong

    2018-02-01

    (11\\bar 2 0)ZnO film/ R-sapphire substrate structure is promising for high frequency acoustic wave devices. The propagation characteristics of SAWs, including the Rayleigh waves along [0001] direction and Love waves along [1ī00] direction, are investigated by using 3 dimensional finite element method (3D-FEM). The phase velocity ( v p), electromechanical coupling coefficient ( k 2), temperature coefficient of frequency ( TCF) and reflection coefficient ( r) of Rayleigh wave and Love wave devices are theoretically analyzed. Furthermore, the influences of ZnO films with different crystal orientation on SAW properties are also investigated. The results show that the 1st Rayleigh wave has an exceedingly large k 2 of 4.95% in (90°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate associated with a phase velocity of 5300 m/s; and the 0th Love wave in (0°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate has a maximum k 2 of 3.86% associated with a phase velocity of 3400 m/s. And (11\\bar 2 0)ZnO film/ R-sapphire substrate structures can be used to design temperature-compensated and wide-band SAW devices. All of the results indicate that the performances of SAW devices can be optimized by suitably selecting ZnO films with different thickness and crystal orientations deposited on R-sapphire substrates.

  12. Dependence of adhesion strength between GaN LEDs and sapphire substrate on power density of UV laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junsu [Department of Nano-Manufacturing Technology, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of); Sin, Young-Gwan [Department of Nano-Mechatronics, Korea University of Science and Technology (UST), 217 Gajeong-Ro, Yuseong-Gu, Daejeon 34113 (Korea, Republic of); Kim, Jae-Hyun [Department of Nano-Mechanics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of); Kim, Jaegu, E-mail: gugu99@kimm.re.kr [Department of Nano-Manufacturing Technology, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of)

    2016-10-30

    Highlights: • Fundamental relationship between laser irradiation and adhesion strength, between gallium-nitride light emitted diode and sapphire substrate, is proposed during selective laser lift-off. • Two competing mechanisms affect adhesion at the irradiated interface between the GaN LED and sapphire substrate. • Ga precipitation caused by thermal decomposition and roughened interface caused by thermal damage lead to the considerable difference of adhesion strength at the interface. - Abstract: Selective laser lift-off (SLLO) is an innovative technology used to manufacture and repair micro-light-emitting diode (LED) displays. In SLLO, laser is irradiated to selectively separate micro-LED devices from a transparent sapphire substrate. The light source used is an ultraviolet (UV) laser with a wavelength of 266 nm, pulse duration of 20 ns, and repetition rate of 30 kHz. Controlled adhesion between a LED and the substrate is key for a SLLO process with high yield and reliability. This study examined the fundamental relationship between adhesion and laser irradiation. Two competing mechanisms affect adhesion at the irradiated interface between the GaN LED and sapphire substrate: Ga precipitation caused by the thermal decomposition of GaN and roughened interface caused by thermal damage on the sapphire. The competition between these two mechanisms leads to a non-trivial SLLO condition that needs optimization. This study helps understand the SLLO process, and accelerate the development of a process for manufacturing micro-LED displays via SLLO for future applications.

  13. Investigation of a direction sensitive sapphire detector stack at the 5 GeV electron beam at DESY-II

    CERN Document Server

    Karacheban, O; Hempel, M; Henschel, H; Lange, W; Leonard, J L; Levy, I; Lohmann, W; Schuwalow, S

    2015-01-01

    Extremely radiation hard sensors are needed in particle physics experiments to instrument the region near the beam pipe. Examples are beam halo and beam loss monitoring systems at the Large Hadron Collider, FLASH or XFEL. Artificial diamond sensors are currently widely used as sensors in these systems. In this paper single crystal sapphire sensors are considered as a promising alternative. Industrially grown sapphire wafers are available in large sizes, are of low cost and, like diamond sensors, can be operated without cooling. Here we present results of an irradiation study done with sapphire sensors in a high intensity low energy electron beam. Then, a multichannel direction-sensitive sapphire detector stack is described. It comprises 8 sapphire plates of 1 cm^2 size and 525 micrometer thickness, metallized on both sides, and apposed to form a stack. Each second metal layer is supplied with a bias voltage, and the layers in between are connected to charge-sensitive preamplifiers. The performance of the dete...

  14. High-Electron-Mobility SiGe on Sapphire Substrate for Fast Chipsets

    Directory of Open Access Journals (Sweden)

    Hyun Jung Kim

    2015-01-01

    Full Text Available High-quality strain-relaxed SiGe films with a low twin defect density, high electron mobility, and smooth surface are critical for device fabrication to achieve designed performance. The mobilities of SiGe can be a few times higher than those of silicon due to the content of high carrier mobilities of germanium (p-type Si: 430 cm2/V·s, p-type Ge: 2200 cm2/V·s, n-type Si: 1300 cm2/V·s, and n-type Ge: 3000 cm2/V·s at 1016 per cm3 doping density. Therefore, radio frequency devices which are made with rhombohedral SiGe on c-plane sapphire can potentially run a few times faster than RF devices on SOS wafers. NASA Langley has successfully grown highly ordered single crystal rhombohedral epitaxy using an atomic alignment of the [111] direction of cubic SiGe on top of the [0001] direction of the sapphire basal plane. Several samples of rhombohedrally grown SiGe on c-plane sapphire show high percentage of a single crystalline over 95% to 99.5%. The electron mobilities of the tested samples are between those of single crystals Si and Ge. The measured electron mobility of 95% single crystal SiGe was 1538 cm2/V·s which is between 350 cm2/V·s (Si and 1550 cm2/V·s (Ge at 6 × 1017/cm3 doping concentration.

  15. Measurement and thermal modeling of sapphire substrate temperature at III-Nitride MOVPE conditions

    Science.gov (United States)

    Creighton, J. Randall; Coltrin, Michael E.; Figiel, Jeffrey J.

    2017-04-01

    Growth rates and alloy composition of AlGaN grown by MOVPE is often very temperature dependent due to the presence of gas-phase parasitic chemical processes. These processes make wafer temperature measurement highly important, but in fact such measurements are very difficult because of substrate transparency in the near-IR ( 900 nm) where conventional pyrometers detect radiation. The transparency problem can be solved by using a mid-IR pyrometer operating at a wavelength ( 7500 nm) where sapphire is opaque. We employ a mid-IR pyrometer to measure the sapphire wafer temperature and simultaneously a near-IR pyrometer to measure wafer pocket temperature, while varying reactor pressure in both a N2 and H2 ambient. Near 1300 °C, as the reactor pressure is lowered from 300 Torr to 10 Torr the wafer temperature drops dramatically, and the ∆T between the pocket and wafer increases from 20 °C to 250 °C. Without the mid-IR pyrometer the large wafer temperature change with pressure would not have been noted. In order to explain this behavior we have developed a quasi-2D thermal model that includes a proper accounting of the pressure-dependent thermal contact resistance, and also accounts for sapphire optical transmission. The model and experimental results demonstrate that at most growth conditions the majority of the heat is transported from the wafer pocket to the wafer via gas conduction, in the free molecular flow limit. In this limit gas conductivity is independent of gap size but first order in pressure, and can quantitatively explain results from 20 to 300 Torr. Further analysis yields a measure of the thermal accommodation coefficients; α(H2) =0.23, α(N2) =0.50, which are in the range typically measured.

  16. Neurosurgical sapphire handheld probe for intraoperative optical diagnostics, laser coagulation and aspiration of malignant brain tissue

    Science.gov (United States)

    Shikunova, Irina A.; Zaytsev, Kirill I.; Stryukov, Dmitrii O.; Dubyanskaya, Evgenia N.; Kurlov, Vladimir N.

    2017-07-01

    In this paper, a handheld contact probe based on sapphire shaped crystal was developed for the intraoperative optical diagnosis and aspiration of malignant brain tissue combined with the laser hemostasis. Such a favorable combination of several functions in a single instrument significantly increases its clinical relevance. It makes possible highly-accurate real-time detection and removal of either large-scale malignancies or even separate invasive cancer cells. The proposed neuroprobe was integrated into the clinical neurosurgical workflow for the intraoperative fluorescence identification and removal of malignant tissues of the brain.

  17. Optimization of contrast ratio and focusable intensity in 700TW femtosecond Ti:sapphire laser facility

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhaohua; Wei Zhiyi; Liu Cheng; Liu Feng; Ma Jinglong; Teng Hao; Zhang Jie, E-mail: zywei@aphy.iphy.ac.c [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2010-08-01

    In this presentation, we report an improvement technique in our 700TW Ti:sapphire laser facility. In order to improve the contrast ratio, we designed a long cavity ring preamplifier. With careful alignment in each dimension of grating, we got a good focal spot after compressor. The size of focal spot was about 25{mu}m with an f/10 off-axis-parabolic mirror (OAP). Using an f/3 OAP to focus the laser beam in experiment, we expect the laser intensity of 10{sup 21}W/cm{sup 2} could be realized on the target.

  18. Synchrotron X-ray diffraction imaging studies of dislocations in Kyropoulos grown Ti doped sapphire crystal

    Science.gov (United States)

    Sen, Gourav; Tran Caliste, Thu Nhi; Stelian, Carmen; Baruchel, José; Barthalay, Nicolas; Duffar, Thierry

    2017-06-01

    In this study, X-ray diffraction and X-ray topography, using synchrotron radiation source, were used to analyse the nature of defects in a sapphire single crystal sample grown by Kyropoulos method. Qualitative and quantitative analysis were carried out on the results of the topography experiments. The dislocation density was found to be around 103-104 dislocations/cm2 indicating a crystal of good crystalline quality. Also, the variation of dislocation density with respect to the position on the sample was observed and discussed.

  19. Liquid-cooled Ti:Sapphire thin disk amplifiers for high average power 100-TW systems.

    Science.gov (United States)

    Nagymihaly, R S; Cao, H; Papp, D; Hajas, G; Kalashnikov, M; Osvay, K; Chvykov, V

    2017-03-20

    In this work, numerical heat transfer simulations of direct water-cooled gain modules for thin disk (TD) Ti:Sapphire (Ti:Sa) power amplifiers are presented. By using the TD technique in combination with the extraction during pumping (EDP) method 100-TW class amplifiers operating around 300 W average power could be reached in the future. Single and double-sided cooling arrangements were investigated for several coolant flow velocities. Simulations which upscale the gain module for multiple kilowatts of average power were also performed for large aperture Ti:Sa disks and for multiple disks with several coolant channels.

  20. Direct diode-pumped Kerr-lens mode-locked Ti:sapphire laser

    Science.gov (United States)

    Durfee, Charles G.; Storz, Tristan; Garlick, Jonathan; Hill, Steven; Squier, Jeff A.; Kirchner, Matthew; Taft, Greg; Shea, Kevin; Kapteyn, Henry; Murnane, Margaret; Backus, Sterling

    2012-01-01

    We describe a Ti:sapphire laser pumped directly with a pair of 1.2W 445nm laser diodes. With over 30mW average power at 800 nm and a measured pulsewidth of 15fs, Kerr-lens-modelocked pulses are available with dramatically decreased pump cost. We propose a simple model to explain the observed highly stable Kerr-lens modelocking in spite of the fact that both the mode-locked and continuous-wave modes are smaller than the pump mode in the crystal. PMID:22714433

  1. Hidden instabilities in the Ti:sapphire Kerr lens mode-locked laser.

    Science.gov (United States)

    Kovalsky, M G; Hnilo, A A; González Inchauspe, C M

    1999-11-15

    It is experimentally shown that pulse-to-pulse instabilities in the output of Kerr lens mode-locked Ti:sapphire lasers are usual and that they can affect some of the pulse variables (e.g., the spot size) and not others (e.g., pulse duration and energy). These instabilities are not detectable in the averaged signals (such as the autocorrelation of the pulse) that are customarily used for controlling the laser. But, if they are present but are disregarded, these instabilities have undesirable consequences in almost any application. A simple way to detect and eliminate the instabilities is described.

  2. High Temperature Characteristics of Coplanar Waveguide on R-Plane Sapphire and Alumina

    Science.gov (United States)

    Ponchak, George E.; Jordan, Jennifer L.; Scardelletti, Maximilian C.

    2007-01-01

    This paper presents the characteristics of coplanar waveguide transmission lines on R-plane sapphire and alumina over the temperature range of 25 to 400 C and the frequency range of 45 MHz to 50 GHz. A Thru-Reflect-Line calibration technique and open circuited terminated stubs are used to extract the attenuation and effective permittivity. It is shown that the effective permittivity of the transmission lines and, therefore, the relative dielectric constant of the two substrates increase linearly with temperature. The attenuation of the coplanar waveguide varies linearly with temperature through 200 C, and increases at a greater rate above 200 C.

  3. Crystal front shape control by use of an additional heater in a Czochralski sapphire single crystal growth system

    Science.gov (United States)

    Hur, Min-Jae; Han, Xue-Feng; Choi, Ho-Gil; Yi, Kyung-Woo

    2017-09-01

    The quality of sapphire single crystals used as substrates for LED production is largely influenced by two defects: dislocation density and bubbles trapped in the crystal. In particular, the dislocation density has a higher value in sapphire grown by the Czochralski (CZ) method than by other methods. In the present study, we predict a decreased value for the convexity and thermal gradient at the crystal front (CF) through the use of an additional heater in an induction-heated CZ system. In addition, we develop a solute concentration model by which the location of bubble formation in CZ growth is calculated, and the results are compared with experimental results. We further calculate the location of bubble entrapment corresponding with the use of an additional heater. We find that sapphire crystal growth with an additional heater yields a decreased thermal gradient at the CF, together with decreased CF convexity, improved energy efficiency, and improvements in terms of bubble formation location.

  4. Characteristics of InGaN-Based Light-Emitting Diodes on Patterned Sapphire Substrates with Various Pattern Heights

    Directory of Open Access Journals (Sweden)

    Sheng-Fu Yu

    2012-01-01

    Full Text Available The optical and electrical characteristics of InGaN-based blue light-emitting diodes (LEDs grown on patterned sapphire substrates (PSSs with different pattern heights and on planar sapphire by atmospheric-pressure metal-organic chemical vapor deposition were investigated. Compared with planar sapphire, it was found that the LED electroluminescence intensity is significantly enhanced on PSSs with pattern heights of 0.5 (21%, 1.1 (57%, 1.5 (81%, and 1.9 (91% μm at an injected current of 20 mA. The increased light intensity exhibits the same trend in a TracePro simulation. In addition, it was also found that the level of leakage current depends on the density of V-shape defects, which were measured by scanning electron microscopy.

  5. The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates.

    Science.gov (United States)

    Cholula-Díaz, Jorge L; Barzola-Quiquia, José; Videa, Marcelo; Yin, Chunhai; Esquinazi, Pablo

    2017-09-13

    Zinc oxide (ZnO) thin films were grown by pulsed layer deposition under an N 2 atmosphere at low pressures on a- and r-plane sapphire substrates. Structural studies using X-ray diffraction confirmed that all films had a wurtzite phase. ZnO thin films on a- and r-plane sapphire have grown with orientations along the [0002] and [112[combining macron]0] directions, respectively. Room temperature photoluminescence measurements indicate that the presence of native point defects (interstitial zinc, oxygen vacancies, oxygen antisites and zinc vacancies) is more preponderant for ZnO thin films grown on the r-plane sapphire substrate than the sample grown on the a-plane sapphire substrate. Room temperature impedance spectroscopy measurements were performed in an alternating current frequency range from 40 to 10 5 Hz in the dark and under normal light. An unusual positive photoresistance effect is observed at frequencies above 100 kHz, which we suggest to be due to intrinsic defects present in the ZnO thin films. Furthermore, an analysis of the optical time response revealed that the film grown on the r-plane sapphire substrate responds faster (characteristic relaxation times for τ 1 , τ 2 and τ 3 of 0.05, 0.26 and 6.00 min, respectively) than the film grown on the a-plane sapphire substrate (characteristic relaxation times for τ 1 , τ 2 and τ 3 of 0.10, 0.73 and 4.02 min, respectively).

  6. Surface phonon polariton responses of hexagonal sapphire crystals with non-polar and semi-polar crystallographic planes.

    Science.gov (United States)

    Lee, Sai Cheong; Ng, Sha Shiong; Hassan, Haslan Abu; Hassan, Zainuriah; Dumelow, Thomas

    2014-09-15

    The surface phonon polariton (SPhP) characteristics of hexagonal sapphire crystals with non-polar and semi-polar crystallographic planes are investigated. A formulation that considers the effects of crystal orientation is employed to calculate the SPhP dispersion curves of the samples. The SPhP dispersion curves indicate that the SPhP responses of sapphire crystals in non-polar and semi-polar orientations are directionally sensitive. Resonance frequencies and spectral strengths of the SPhP modes can be modulated simply by tuning the angular positions of the samples. The validity of the theoretical results is confirmed by the polarized infrared attenuated total reflection measurements.

  7. Wavelength-multiplexed pumping with 478- and 520-nm indium gallium nitride laser diodes for Ti:sapphire laser.

    Science.gov (United States)

    Sawada, Ryota; Tanaka, Hiroki; Sugiyama, Naoto; Kannari, Fumihiko

    2017-02-20

    We experimentally reveal the pump-induced loss in a Ti:sapphire laser crystal with 451-nm indium gallium nitride (InGaN) laser diode pumping and show that 478-nm pumping can reduce such loss. The influence of the pump-induced loss at 451-nm pumping is significant even for a crystal that exhibits higher effective figure-of-merit and excellent laser performance at 520-nm pumping. We demonstrate the power scaling of a Ti:sapphire laser by combining 478- and 520-nm InGaN laser diodes and obtain CW output power of 593 mW.

  8. Use of contact Nd:YAG sapphire-laser system for performing partial hepatectomy and splenectomy in dogs

    Science.gov (United States)

    Yu, Chibing; Jing, Shujuan; Cai, Huimin; Shao, Lanxing; Zou, Hegui

    1993-03-01

    An Nd:YAG Sapphire laser blade was used for performing hepatectomy and splenectomy in dogs. The results suggest that a laser blade provides a new way to reduce intraoperative bleeding and to minimize tissue damage. In recent years, there have been some reports on performing surgical procedures using a contact Nd:YAG Sapphire laser system. The current animal study was conducted in order to explore the capability of incision and excision of the laser tip, the damage to the tissue, and the recovery course.

  9. Broadly tunable high-power operation of an all-solid-state titanium-doped sapphire laser system

    Science.gov (United States)

    Steele, T. R.; Gerstenberger, D. C.; Drobshoff, A.; Wallace, R. W.

    1991-01-01

    Broadly tunable and high-power operation of a Ti-doped sapphire laser is obtained with a diode-laser-pumped frequency-doubled Nd:YAG laser as the pump source. A maximum broadband (FWHM = 25 nm) output pulse energy of 720 microJ at 795 nm in a TEM00 mode is obtained for 1850 microJ of energy of 532-nm pump light. A minimum pulse duration of 7 nsec is obtained from a 40-mm-long cavity. With the use of an intracavity prism, the Ti:sapphire laser is tunable continuously over the 696-1000-nm spectral range (with three different mirror sets).

  10. Atomic fountain clock with very high frequency stability employing a pulse-tube-cryocooled sapphire oscillator.

    Science.gov (United States)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Tanabe, Takehiko; Hagimoto, Ken; Hirano, Iku; Watabe, Ken-ichi; Ikegami, Takeshi; Hartnett, John G

    2014-09-01

    The frequency stability of an atomic fountain clock was significantly improved by employing an ultra-stable local oscillator and increasing the number of atoms detected after the Ramsey interrogation, resulting in a measured Allan deviation of 8.3 × 10(-14)τ(-1/2)). A cryogenic sapphire oscillator using an ultra-low-vibration pulse-tube cryocooler and cryostat, without the need for refilling with liquid helium, was applied as a local oscillator and a frequency reference. High atom number was achieved by the high power of the cooling laser beams and optical pumping to the Zeeman sublevel m(F) = 0 employed for a frequency measurement, although vapor-loaded optical molasses with the simple (001) configuration was used for the atomic fountain clock. The resulting stability is not limited by the Dick effect as it is when a BVA quartz oscillator is used as the local oscillator. The stability reached the quantum projection noise limit to within 11%. Using a combination of a cryocooled sapphire oscillator and techniques to enhance the atom number, the frequency stability of any atomic fountain clock, already established as primary frequency standard, may be improved without opening its vacuum chamber.

  11. Characteristics and kinetics of laser-pumped Ti:Sapphire oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Eggleston, J.M.; De Shazer, L.G.; Kangas, K.W.

    1988-06-01

    The experimental performance of a gain-switched Ti:Sapphire laser oscillator pumped by a frequency-doubled Q-switched Nd:YAG laser system is presented for a variety of operating conditions. A theoretical model developed for this oscillator predicts well its performance. In particular, the observed curved input-output energy plots for the oscillator result from the kinetics of gain switching and fluorescence decay during the gain buildup period. Fluorescence decay also produces observed oscillator thresholds higher than those normally predicted by the standard gain-equals-loss condition. Gain-switched parasitic modes, with a higher threshold but shorter roundtrip time than the resonator mode, cause the resonator mode to oscillate only over a finite range of pump energies. Also, spectroscopic investigations show that the Ti:Sapphire cross-section spectrum is well fit by a Poisson distribution, giving a peak cross section of 3 x 10/sup -19/ cm/sup 2/ for the ..pi.. polarization.

  12. High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams.

    Science.gov (United States)

    Rapp, L; Meyer, R; Giust, R; Furfaro, L; Jacquot, M; Lacourt, P A; Dudley, J M; Courvoisier, F

    2016-09-27

    Femtosecond pulses provide an extreme degree of confinement of light matter-interactions in high-bandgap materials because of the nonlinear nature of ionization. It was recognized very early on that a highly focused single pulse of only nanojoule energy could generate spherical voids in fused silica and sapphire crystal as the nanometric scale plasma generated has energy sufficient to compress the material around it and to generate new material phases. But the volumes of the nanometric void and of the compressed material are extremely small. Here we use single femtosecond pulses shaped into high-angle Bessel beams at microjoule energy, allowing for the creation of very high 100:1 aspect ratio voids in sapphire crystal, which is one of the hardest materials, twice as dense as glass. The void volume is 2 orders of magnitude higher than those created with Gaussian beams. Femtosecond and picosecond illumination regimes yield qualitatively different damage morphologies. These results open novel perspectives for laser processing and new materials synthesis by laser-induced compression.

  13. Influence of defects and displacements in sapphire doped with Ag{sup +} ions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hua-jian [Hubei Province Key Laboratory of Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081 (China); Wang, Yu-hua, E-mail: wangyuhua@wust.edu.cn [Hubei Province Key Laboratory of Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081 (China); Zhang, Xiao-jian [Hubei Province Key Laboratory of Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081 (China); Zheng, Li-rong [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-12-01

    Highlights: • Silver nanoparticles were formed by Ag{sup +} ion implantation in sapphire. • UV–Vis and VUV spectra have been used to investigate the transition among energy level. • The defects, especially F-type centers, are responsible for transition among energy level phenomena. - Abstract: The Ag:Al{sub 2}O{sub 3} composites are prepared by Ag{sup +} ions implantation with the acceleration voltage of 35 kV. The formation of silver nanoparticle and the surface plasma resonance (SPR) effect are studied. The appearance of absorption bands demonstrates the formation of silver nanoparticles in Al{sub 2}O{sub 3}. Long-time sputtering due to the high fluency removes the surface layer, and the embedded Ag NPs appear on the surface though the majorities are in the deeper area. The fluorescence spectrum of Ag:Al{sub 2}O{sub 3} evaluated by Gaussian fitting consists of three peaks: 365 nm, 403 nm and 471 nm. These bands should be attributed to defects produced by the matrix and embedded Ag{sup +} ions. In addition, a strong peak at 693 nm is supposed to be R line for Al{sub 2}O{sub 3} in the emission spectrum (VUV spectrum). The crystal structure and optical properties of ion implanted sapphire have been changed after ion implantation and it is analyzed by defects and displacements. Eventually, the SRIM program is used to simulate the growth of nanoparticles with four stages.

  14. The defect character of GaN growth on r-plane sapphire

    Science.gov (United States)

    Smalc-Koziorowska, J.; Tsiakatouras, G.; Lotsari, A.; Georgakilas, A.; Dimitrakopulos, G. P.

    2010-04-01

    We study the influence of the heteroepitaxial interface on the defect content of nonpolar a-plane GaN grown on r-plane sapphire, using transmission electron microscopy techniques and the topological theory of interfacial defects. The structural mismatch is accommodated in different ways along distinct in-plane directions. For the misfit along the [0001] direction of GaN, the I1 basal stacking faults constitute the principal relaxation mechanism, through their delimiting partial dislocations. The misfit along [11¯00] is relaxed by misfit dislocations that have out-of-plane Burgers vectors causing rotational misorientations of the epilayer about [0001]. These misorientations lead to the introduction of low-angle tilt grain boundaries which are defect sources through their associated primary lattice dislocations. Furthermore, semipolar nanocrystals can nucleate on sapphire p-plane nanofacets, causing the introduction of threading dislocations (TDs) and stacking faults, when these nanocrystals are overgrown by the nonpolar epilayer. The semipolar nanocrystals bear a high-symmetry 90° [1¯21¯0] orientation relative to the nonpolar epilayer. The interfacial dislocations at the nonpolar/semipolar boundaries have suitable Burgers vectors to become TDs. These grain boundaries also promote the introduction of stacking faults and pockets of cubic GaN. The coexistence of semipolar orientation variants leads to twin boundaries and associated dislocations.

  15. Surface Texture and Crystallinity Variation of ZnTe Epilayers Grown on the Step-Terrace Structure of the Sapphire Substrate

    Science.gov (United States)

    Nakasu, Taizo; Kizu, Takeru; Yamashita, Sotaro; Aiba, Takayuki; Hattori, Shota; Sun, Wei-Che; Taguri, Kosuke; Kazami, Fukino; Hashimoto, Yuki; Ozaki, Shun; Kobayashi, Masakazu; Asahi, Toshiaki

    2016-04-01

    ZnTe/sapphire heterostructures were focused, and ZnTe thin films were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. A sapphire substrate possessing an atomically-smooth step-terrace structure was used to improve the crystallinity and morphology of the produced ZnTe film. The growth mode of the ZnTe thin film on a sapphire substrate with an atomically-smooth step-terrace structure was found to shift to a two-dimensional growth mode, and a ZnTe thin film possessing a flat surface was obtained. The crystallographic properties of the ZnTe film suggested that the resulting layer consisted of a single (111)-oriented domain. The photoluminescence property was also improved, and the interface lattice alignment between the ZnTe and sapphire was also affected by the atomically-smooth step-terrace structure.

  16. Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire—I. Microstructural characterization

    Directory of Open Access Journals (Sweden)

    Sung Bo Lee

    2015-07-01

    Full Text Available Much research has been done to reduce dislocation densities for the growth of GaN on sapphire, but has paid little attention to the elastic behavior at the GaN/sapphire interface. In this study, we have examined effects of the addition of Si to a sapphire substrate on its elastic property and on the growth of GaN deposit. Si atoms are added to a c-plane sapphire substrate by ion implantation. The ion implantation results in scratches on the surface, and concomitantly, inhomogeneous distribution of Si. The scratch regions contain a higher concentration of Si than other regions of the sapphire substrate surface, high-temperature GaN being poorly grown there. However, high-temperature GaN is normally grown in the other regions. The GaN overlayer in the normally-grown regions is observed to have a lower TD density than the deposit on the bare sapphire substrate (with no Si accommodated. As compared with the film on an untreated, bare sapphire, the cathodoluminescence defect density decreases by 60 % for the GaN layer normally deposited on the Si-ion implanted sapphire. As confirmed by a strain mapping technique by transmission electron microscopy (geometric phase analysis, the addition of Si in the normally deposited regions forms a surface layer in the sapphire elastically more compliant than the GaN overlayer. The results suggest that the layer can largely absorb the misfit strain at the interface, which produces the overlayer with a lower defect density. Our results highlight a direct correlation between threading-dislocation density in GaN deposits and the elastic behavior at the GaN/sapphire interface, opening up a new pathway to reduce threading-dislocation density in GaN deposits.

  17. Study on planarization machining of sapphire wafer with soft-hard mixed abrasive through mechanical chemical polishing

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yongchao [Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021 (China); MOE Engineering Research Center for Brittle Materials Machining, Huaqiao University, Xiamen 361021 (China); Lu, Jing, E-mail: lujing26@hqu.edu.cn [Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021 (China); MOE Engineering Research Center for Brittle Materials Machining, Huaqiao University, Xiamen 361021 (China); Xu, Xipeng [Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021 (China); MOE Engineering Research Center for Brittle Materials Machining, Huaqiao University, Xiamen 361021 (China)

    2016-12-15

    Highlights: • Nano-silica abrasive with higher reactivity are prepared by hydrolysis-precipitation. • Polishing performance of soft-hard mixed abrasives during MCP is investigated. • Products of solid state reaction have been further confirmed by a new approach. • Material removal mechanism of sapphire with mixed abrasives is discussed. - Abstract: This study investigated the material removal mechanism of sapphire wafer with soft-hard mixed abrasives through mechanical chemical polishing (MCP). The polishing film, which contains diamond as hard abrasives and high reactivity silica as soft abrasives, is prepared through sol-gel technology. Silica abrasives with regular spherical shape and high reactivity are prepared through hydrolysis-precipitation. Diamond grits with three different particle sizes are used as abrasives. Results show that the rate of material removal of mixed abrasives during MCP is more than 52.6% of that of single hard abrasives and the decrease in surface roughness is more than 21.6% of that of single hard abrasives. These results demonstrate that the ideal planarization of sapphire wafer with high removal rate and good surface quality can be achieved when the effect of mechanical removal of hard abrasives and the chemical corrosion effect of soft abrasives are in dynamic equilibrium. A model that describes the material removal mechanism of sapphire with mixed abrasives during MCP is proposed. The results of thermodynamic calculation and polishing residue analysis are used to demonstrate the rationality of the model.

  18. Epitaxial growth of HfS2 on sapphire by chemical vapor deposition and application for photodetectors

    Science.gov (United States)

    Wang, Denggui; Zhang, Xingwang; Liu, Heng; Meng, Junhua; Xia, Jing; Yin, Zhigang; Wang, Ye; You, Jingbi; Meng, Xiang-Min

    2017-09-01

    Group IVB transition metal (Zr and Hf) dichalcogenides (TMDs) have been attracting intensive attention as promising candidates in the modern electronic and/or optoelectronic fields. However, the controllable growth of HfS2 monolayers or few layers still remains a great challenge, thus hindering their further applications so far. Here, for the first time we demonstrate the epitaxial growth of high-quality HfS2 with a controlled number of layers on c-plane sapphire substrates by chemical vapor deposition (CVD). The HfS2 layers exhibit an atomically sharp interface with the sapphire substrate, followed by flat, 2D layers with octahedral coordination. The epitaxial relationship between HfS2 and substrate was determined by x-ray diffraction and transmission electron microscopy measurements to be: HfS2 (0 0 0 1) [10-10]||sapphire (0 0 0 1)[1-100]. Moreover, a high-performance photodetector with a high on/off ratio of more than 103 and an ultrafast response rate of 130 µs for the rise and 155 µs for the decay times were fabricated based on the CVD-grown HfS2 layers on sapphire substrates. This simple and controllable approach opens up a new way to produce highly crystalline HfS2 atomic layers, which are promising materials for nanoelectronics.

  19. Performance of Ar+-milled Ti:Sapphire rib waveguides as single transverse-mode broadband fluorescence sources

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus; Crunteanu, A.; Jelinek, M.

    2003-01-01

    Rib waveguides have been fabricated in pulsed-laser-deposited Ti:sapphire layers using photolithographic patterning and subsequent Ar+-beam milling. Fluorescence output powers up to 300 W have been observed from the ribs following excitation by a 3-W multiline argon laser. Mode intensity profiles

  20. Broadband single-transverse-mode fluorescence sources based on ribs fabricated in pulsed laser deposited Ti: sapphire waveguides

    NARCIS (Netherlands)

    Grivas, C.; May-Smith, T.C.; Shepherd, D.P.; Eason, R.W.; Pollnau, Markus; Jelinek, M.

    2004-01-01

    Active rib waveguides with depths and widths varying from 3 to 5 μm and from 9 to 24 μm, respectively, have been structured by $Ar^{+}$-beam etching in pulsed laser deposited Ti:sapphire layers. Losses in the channel structures were essentially at the same levels as the unstructured planar waveguide

  1. Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

    KAUST Repository

    Sun, Haiding

    2017-08-08

    The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

  2. The study on the nanomachining property and cutting model of single-crystal sapphire by atomic force microscopy.

    Science.gov (United States)

    Huang, Jen-Ching; Weng, Yung-Jin

    2014-01-01

    This study focused on the nanomachining property and cutting model of single-crystal sapphire during nanomachining. The coated diamond probe is used to as a tool, and the atomic force microscopy (AFM) is as an experimental platform for nanomachining. To understand the effect of normal force on single-crystal sapphire machining, this study tested nano-line machining and nano-rectangular pattern machining at different normal force. In nano-line machining test, the experimental results showed that the normal force increased, the groove depth from nano-line machining also increased. And the trend is logarithmic type. In nano-rectangular pattern machining test, it is found when the normal force increases, the groove depth also increased, but rather the accumulation of small chips. This paper combined the blew by air blower, the cleaning by ultrasonic cleaning machine and using contact mode probe to scan the surface topology after nanomaching, and proposed the "criterion of nanomachining cutting model," in order to determine the cutting model of single-crystal sapphire in the nanomachining is ductile regime cutting model or brittle regime cutting model. After analysis, the single-crystal sapphire substrate is processed in small normal force during nano-linear machining; its cutting modes are ductile regime cutting model. In the nano-rectangular pattern machining, due to the impact of machined zones overlap, the cutting mode is converted into a brittle regime cutting model. © 2014 Wiley Periodicals, Inc.

  3. Intracavity doubling of CW Ti:sapphire laser to 392.5 nm using BiBO-crystal

    DEFF Research Database (Denmark)

    Mortensen, Jesper Liltorp; Thorhauge, Morten; Tidemand-Lichtenberg, Peter

    2005-01-01

    In this work we present results obtained for intra-cavity frequency-doubling of a 785 nm CW Ti:sapphire laser utilising BiBO as the non-linear crystal. Intracavity doubling offers several advantages compared to extra-cavity doubling, such as no need to couple to an external resonance cavity, and ...

  4. Frictional interactions in forming processes: New studies with transparent sapphire strip-drawing dies

    Science.gov (United States)

    Rao, R. S.; Lu, C. Y.; Wright, P. K.; Devenpeck, M. L.; Richmond, O.; Appleby, E. J.

    1982-05-01

    This research is concerned with the frictional interactions at the toolwork interfaces in the machining and strip-drawing processes. A novel feature is that transparent sapphire (single crystal Al2O3) is being used as the tool and die material. This allows the tribological features of the interface to be directly observed and recorded on movie-film. These qualitative studies provide information on the role of lubricants. In addition, techniques are being developed to quantify the velocity gradient along the interface. For example, in the drawing work it has been found that tracer markings (e.g. dye-spots), applied to the undrawn strip, remain intact during drawing and can be tracked along the sapphire/strip interface. Such data will be used as input to a finite-element, elasto-plastic-workhardening model of the deformation process. The latter can compute strip deformation characteristics, drawing forces and local coefficients of friction at the interface. Introductory results will be presented in this paper, obtained from drawing tin-plated mild steel with sapphire and cemented carbide dies. Drawing loads and die-separating forces will be presented and movie-films of the action of tracer markings at the interface shown. In order to demonstrate how this data can be used in an analysis of a large strain deformation process with friction, initial results from running the FIPDEF elasto-plastic code will be discussed. From a commercial viewpoint research on strip-drawing is of special interest to the can-making industry. From a physical viewpoint stripdrawing is of particular interest because it is a symmetrical, plane strain deformation and, in comparison with other metal processing operations, it is more readily modeled. However, until now the elasto-plastic codes that have been developed to predictively model drawing have had limitations: the most notable being that of quantifying the friction conditions at the die-work interface. Hence the specification of the

  5. Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study.

    Science.gov (United States)

    Mohamed, Jauhar P; Kommi, Pradeep Babu; Kumar, M Senthil; Hanumanth; Venkatesan; Aniruddh; Arvinth; Kumar, Arani Nanda

    2016-08-01

    Most of the patients seek orthodontic treatment to improve the smile, which improves the facial profile by means of fixed appliances i.e., brackets and wires. The brackets are of different types like stainless steel and ceramic. Ceramic brackets were considered as aesthetic appliance which was divided into mono-crystalline, polycrystalline and sapphire brackets. The light transmittance might influence the degree of curing adhesive material in mono crystalline, polycrystalline and sapphire brackets. The aim of the present study was to evaluate the translucency and intensity of three different aesthetic brackets (mono crystalline, poly crystalline and sapphire ceramic brackets) and to determine their influence on shear bond strength of the brackets. The adhesive remnant index was also measured after debonding of the brackets from the tooth surface. Twenty six samples each of monocrystalline, polycrystalline and sapphire brackets (total 78 ceramic brackets) were used for the study. The bracket samples were subjected to optical fluorescence test using spectrofluorometer to measure the intensity of the brackets. Seventy eight extracted premolar teeth were procured and divided into 3 groups. The brackets were then bonded to the tooth using Transbond XT (3M Unitek) light cure composite material and cured with new light cure unit (Light Emitting Diode) of wood pecker company (400-450nm) for 30 seconds, and these samples were subjected to shear bond strength test with Instron Universal Testing Machine (UNITEK-94100) with a load range between 0 to 100 KN with a maximum cross head speed of 0.5mm/min. ARI (Adhesive Remnant Index) scores were evaluated according to Artun and Bergland scoring system using stereomicroscope at 20x magnification. The light absorption values obtained from spectrofluorometeric study were 3300000-3500000 cps for group 1 (monocrystalline ceramic brackets), 6000000-6500000 cps for Group 2 (polycrystalline ceramic brackets) and 2700000 -3000000 cps for

  6. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  7. Preparation of Ce-doped colloidal SiO{sub 2} composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Hong, E-mail: hong_lei2005@aliyun.com [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Tong, Kaiyu; Wang, Zhanyong [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China)

    2016-04-01

    Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of key elements during CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel Ce-doped colloidal SiO{sub 2} composite abrasives were prepared by chemical co-precipitation method. The CMP performances of the Ce-doped colloidal SiO{sub 2} composite abrasives on sapphire substrate were investigated by using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the Ce-doped colloidal SiO{sub 2} composite abrasives exhibit lower surface roughness, higher material removal rate than that of pure colloidal SiO{sub 2} abrasive under the same testing conditions. Furthermore, the acting mechanism of the Ce-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between Ce-doped silica abrasives and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removing rate. - Highlights: • Novel Ce-doped colloidal SiO{sub 2} composite abrasives were prepared. • The chemical mechanical polishing (CMP) performances of the composite abrasives on sapphire substrate were investigated. • Novel composite abrasives show excellent polishing characteristics comparison with pure colloidal SiO{sub 2} abrasive. • We explore and report the acting mechanism of composite abrasives to sapphire CMP.

  8. Crystal tilting in GaN grown by pendoepitaxy method on sapphire substrate

    Science.gov (United States)

    Kim, Ig-Hyeon; Sone, C.; Nam, Ok-Hyun; Park, Yong-Jo; Kim, Taeil

    1999-12-01

    Pendeoepitaxy of GaN on sapphire substrate with SiO2 mask is demonstrated and characterized by transmission electron microscopy and double crystal x-ray diffraction. A continuous layer of GaN with low dislocation density was achieved by this method. Parts of the GaN layer are tilted symmetrically toward [11-20] direction and have two kinds of coalesce and tilt boundaries. Each boundary was formed by a vertical array of piled up dislocations with the Burger's vector of [11-20]. The tilting mechanism in pendeo-epitaxy is discussed in terms of surface interaction between the SiO2 mask and ELO-GaN.

  9. Narrow linewidth operation of the RILIS titanium: Sapphire laser at ISOLDE/CERN

    CERN Document Server

    Rothe, S; Wendt, K D A; Fedosseev, V N; Kron, T; Marsh, B A

    2013-01-01

    A narrow linewidth operating mode for the Ti:sapphire laser of the CERN ISOLDE Resonance Ionization Laser Ion Source (RILIS) has been developed. This satisfies the laser requirements for the programme of in-source resonance ionization spectroscopy measurements and improves the selectivity for isomer separation using RILIS. A linewidth reduction from typically 10 GHz down to 1 GHz was achieved by the intra-cavity insertion of a second (thick) Fabry-Perot etalon. Reliable operation during a laser scan was achieved through motorized control of the tilt angle of each etalon. A scanning, stabilization and mode cleaning procedure was developed and implemented in LabVIEW. The narrow linewidth operation was confirmed in a high resolution spectroscopy study of francium isotopes by the Collinear Resonance Ionization Spectroscopy experiment. The resulting laser scans demonstrate the suitability of the laser, in terms of linewidth, spectral purity and stability for high resolution in-source spectroscopy and isomer select...

  10. Cryo-Cooled Sapphire Oscillator for the Cassini Ka-Band Experiment

    Science.gov (United States)

    Wang, Rabi T.; Dick, G. John

    1997-01-01

    We present features for an ultra-stable sapphire cryogenic oscillator which has been designed to support the Cassini Ka-band Radio Science experiment. The design of this standard is new in several respects. It is cooled by a commercial cryocooler instead of liquid cryogens to increase operating time, and it uses a technology to adjust the temperature turn-over point to extend the upper operating temperature limit and to enable construction of multiple units with uniform operating characteristics. Objectives are 3 x 10(exp -15) stability for measuring times 1 second less than or equal to (tau) less than or equal to 100 seconds, phase noise of -85 dBc/Hz from offset frequencies of 1 Hz to 1000 Hz at 10 GHz carrier frequency, and a one year continuous operating period.

  11. Quantum cascade lasers transfer-printed on silicon-on-sapphire

    Science.gov (United States)

    Jung, Seungyong; Kirch, Jeremy; Kim, Jae Hyun; Mawst, Luke J.; Botez, Dan; Belkin, Mikhail A.

    2017-11-01

    We demonstrate coupling of the laser mode into a passive waveguide by transfer-printing fully processed mid-infrared quantum cascade lasers onto a silicon-on-sapphire platform. The laser waveguide mode is coupled into a silicon waveguide via an adiabatic taper. The experimentally achieved coupling efficiency of the taper is estimated to be ˜10%, and theoretical calculations show that coupling efficiency over 75% is achievable by reducing the adhesive layer thickness to below 100 nm. Light coupling to silicon waveguides is confirmed by images taken at the output facet of a 3-mm-long passive Si waveguide with a mid-infrared camera. Our technique enables the development of heterogeneous photonic systems integrated with a wide range of fully processed semiconductor laser devices, including buried-heterostructure lasers, which was not previously possible.

  12. Octave-spanning, dual-output 2.166 GHz Ti:sapphire laser.

    Science.gov (United States)

    Chen, Li-Jin; Benedick, Andrew J; Birge, Jonathan R; Sander, Michelle Y; Kärtner, Franz

    2008-12-08

    A self-referenced octave-spanning Ti:sapphire laser with 2.166 GHz repetition rate is demonstrated. The laser features both direct generation of octave-spanning spectra and a dual-output design for non-intrusive carrier-envelope (CE) phase-stabilization. Only a few percent of total power containing 1f and 2f spectral components is coupled out through a specially designed laser mirror and generates a >50 dB CE beat note in 100 kHz resolution bandwidth without perturbing the main output that still delivers octave-spanning spectra and 750 mW of output power. (c) 2008 Optical Society of America

  13. Nonlinear Phase Distortion in a Ti:Sapphire Optical Amplifier for Optical Stochastic Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Andorf, Matthew [NICADD, DeKalb; Lebedev, Valeri [Fermilab; Piot, Philippe [NICADD, DeKalb; Ruan, Jinhao [Fermilab

    2016-06-01

    Optical Stochastic Cooling (OSC) has been considered for future high-luminosity colliders as it offers much faster cooling time in comparison to the micro-wave stochastic cooling. The OSC technique relies on collecting and amplifying a broadband optical signal from a pickup undulator and feeding the amplified signal back to the beam. It creates a corrective kick in a kicker undulator. Owing to its superb gain qualities and broadband amplification features, Titanium:Sapphire medium has been considered as a gain medium for the optical amplifier (OA) needed in the OSC*. A limiting factor for any OA used in OSC is the possibility of nonlinear phase distortions. In this paper we experimentally measure phase distortions by inserting a single-pass OA into one leg of a Mach-Zehnder interferometer. The measurement results are used to estimate the reduction of the corrective kick a particle would receive due to these phase distortions in the kicker undulator.

  14. Starting dynamics of a cw passively mode-locked picosecond Ti:sapphire/DDI laser.

    Science.gov (United States)

    Pu, N W; Shieh, J M; Lai, Y; Pan, C L

    1995-01-15

    We show that, for a cw passively mode-locked picosecond Ti:sapphire/DDI laser, the first autocorrelation trace with negligible cw background occurs at a delay time of 20 mu;s, or 1600 round trips from the first relaxationoscillation peak. The trace suggests that the pulse consists of a primary pulse as short as 4.4 ps and of small secondary pulses that form a much wider pedestal of the trace, each containing approximately 50% of the photon energy. Nearly transform-limited approximately 5-ps-wide Gaussian pulses were observed at a delay time of 40 mu;s. After 45 mu;s, the optical spectrum broadened considerably, and the time-bandwidth product increased to 4 in the steady state (after 60 micros).

  15. Multiphoton Ionization of Magnesium in a Ti-Sapphire laser field

    CERN Document Server

    Nikolopoulos, L A A; Lambropoulos, P; 10.1140/epjd/e2003-00265-7

    2013-01-01

    In this paper we report the theoretical results obtained for partial ionization yields and the above-threshold ionization (ATI) spectra of Magnesium in a Ti:sapphire laser field (804 nm) in the range of short pulse duration (20-120 fs). Ionization yield, with linearly polarized light for a 120 fs laser pulse, is obtained as a function of the peak intensity motivated by recent experimental data \\cite{gillen:2001}. For this, we have solved the time-dependent Schr\\"{o}dinger equation nonperturbatively on a basis of discretized states obtained with two different methods; one with the two-electron wavefunction relaxed at the boundaries, giving a quadratic discretized basis and the other with the two-electron wavefunction expanded in terms of Mg$^+$-orbitals plus one free electron allowing the handling of multiple continua (open channels). Results, obtained with the two methods, are compared and advantages and disadvantages of the open-channel method are discussed.

  16. Visible lasing from GaN:Eu optical cavities on sapphire substrates

    Science.gov (United States)

    Park, J. H.; Steckl, A. J.

    2006-05-01

    We report visible (red) lasing emission from Eu-doped GaN thin films grown on sapphire substrates. The edge emission fulfills the requirements of stimulated emission properties: super-linear characteristic, spectrum line narrowing, polarization effect, lifetime reduction, and longitudinal modes in a Fabry-Perot cavity. The GaN:Eu active layer has low threshold (˜10 kW/cm 2) for the onset of lasing. The optical gain and loss are of the order of 50 and 20 cm -1, respectively. Growth conditions are investigated for gain enhancement and loss reduction. To obtain the high gain and low loss active layer, N-rich growth conditions are required. Channel waveguide cavities result in 5× increase in gain value compared to planar waveguides.

  17. Improving InGaN-LED performance by optimizing the patterned sapphire substrate shape

    Institute of Scientific and Technical Information of China (English)

    Huang Xiao-Hui; Liu Jian-Ping; Fan Ya-Ming; Kong Jun-Jie; Yang Hui; Wang Huai-Bing

    2012-01-01

    The epitaxial growths of GaN films and GaN-based LEDs on various patterned sapphire substrates (PSSes) with different values of fill factor (f) and slanted angle (θ) are investigated in detail.The threading dislocation (TD) density is lower in the film grown on the PSS with a smaller fill factor,resulting in a higher internal quantum efficiency (IQE).Also the ability of the LED to withstand the electrostatic discharge (ESD) increases as the fill factor decreases.The illumination output power of the LED is affected by both θ and f.It is found that the illumination output power of the LED grown on the PSS with a lower production of tan θ and f is higher than that with a higher production of tan θ and f.

  18. Self-catalytic growth of AlN microrods on sapphire substrate

    Science.gov (United States)

    Kuppulingam, B.; Singh, Shubra; Baskar, K.

    2017-06-01

    One-dimensional AlN microrods have been grown on sapphire substrate by oxide-assisted vapor utilizing chemical vapor deposition method via vapor-solid mechanism. The structure and morphology of as-grown samples were analyzed by HRXRD, Raman, FT-IR, SEM and TEM. AlN microrods possess single crystalline hexagonal structure with average diameter 0.7 μm and length 5 μm. Chemical compositions have been estimated from EDX analysis. X-ray photoelectron peaks of Al, N, O and C were observed on the surface of AlN microstructures. Photoluminescence spectrum reveals broad ultraviolet, blue emission bands corresponding to deep-level defects. From the optical absorption spectrum direct bandgap was found to be 5.66 eV.

  19. 17-fs pulses from a self-mode-locked Ti:sapphire laser.

    Science.gov (United States)

    Huang, C P; Asaki, M T; Backus, S; Murnane, M M; Kapteyn, H C; Nathel, H

    1992-09-15

    We have generated sub-17-fs-duration pulses directly from a self-mode-locked Ti:sapphire laser. These pulses are near transform limited, with a wavelength centered at 817 nm, a pulse repetition rate of 80 MHz, and an average power of 500 mW. By minimizing the amount of material inside the laser cavity and choosing the correct glass for the intracavity prism pair, third-order dispersion in the laser can be significantly reduced compared with that in previous designs. Extracavity compensation for group-velocity dispersion in the output coupler and autocorrelator optics is necessary to measure this pulse width. To our knowledge this laser generates pulses substantially shorter than any other laser to date.

  20. A 10-Hz Terawatt Class Ti:Sapphire Laser System: Development and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, A.K.; Smedley, J.; Tsang, T.; Rao, T.

    2010-01-12

    We developed a two stage Ti:Sapphire laser system to generate 16 mJ/80fs laser pulses at the pulse repetition rate of 10 Hz. The key deriver for the present design is implementing a highly efficient symmetric confocal pre-amplifier and employing a simple, inexpensive synchronization scheme relying only on a commercial digital delay-generator. We characterized the amplified pulses in spatial-, spectral-, and temporal-domains. The laser system was used to investigate various nonlinear optical processes, and to modify the optical properties of metal- and semiconductor-surfaces. We are currently building a third amplifier to boost the laser power to the multi-terawatt range.

  1. Nanostructured sapphire vicinal surfaces as templates for the growth of self-organized oxide nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Thune, E., E-mail: elsa.thune@unilim.fr [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Boulle, A. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Babonneau, D.; Pailloux, F. [Laboratoire de Physique des Materiaux (PHYMAT), UMR CNRS 6630, Universite de Poitiers, Boulevard Marie et Pierre Curie - Teleport 2, BP 30179, F-86962 Futuroscope - Chasseneuil Cedex (France); Hamd, W.; Guinebretiere, R. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France)

    2009-11-15

    Vicinal substrates of sapphire with miscut angle of 10 deg. from the (0 0 1) planes towards the [1 1 0] direction have been annealed in air in the range from 1000 to 1500 deg. C. The behaviour of these surfaces has been characterized as a function of the temperature and the thermal treatment time by Atomic Force Microscopy observations. A thermal treatment at 1250 deg. C allows to stabilize a surface made of periodically spaced nanosized step-bunches. Such stepped surfaces were used as template to grow self-patterned epitaxial oxide nanoparticles by thermal annealing of yttria-stabilized zirconia thin films produced by sol-gel dip-coating. Grazing Incidence Small Angle X-ray Scattering and High-Resolution Transmission Electron Microscopy were used to study the morphology of the nanoparticles and their epitaxial relationships with the substrate.

  2. Defects and nucleation of GaN layers on (0001) sapphire

    Science.gov (United States)

    Degave, F.; Ruterana, P.; Nouet, G.; Je, J. H.; Kim, C. C.

    2002-12-01

    The morphology and microstructural evolution of a nucleation layer are analysed using high-resolution transmission electron microscopy. Low-temperature nucleation of GaN on (0001) sapphire is investigated. Depositions were made for 20, 40, 60, 120 and 180 s at 560°C by metal-organic chemical vapour deposition. It is shown that the shortest deposition times give rise to the formation of cubic islands. Subsequently, the density and the size of the nucleated islands increase and they start to transform into wurtzite from the interface with the substrate. From the start, the nuclei contain misfit dislocations. At these early growth stages, the relaxation state changes from one island to another; this probably underlies the subsequent mosaïc growth of the high-temperature-active GaN layers.

  3. Advances in Trace Element “Fingerprinting” of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar

    Directory of Open Access Journals (Sweden)

    F. Lin Sutherland

    2014-12-01

    Full Text Available Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method and oxygen isotope values (δ18O, by laser fluorination. The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents. Oxygen isotope values (δ18O for the ruby and high Si-Ca-Ga corundum (20‰–25‰ and for sapphire (10‰–20‰ indicate typical crustal values, with values >20‰ being typical of carbonate genesis. The high Si-Ca-Ga ruby has high chromium (up to 3.2 wt % Cr and gallium (up to 0. 08 wt % Ga compared to most Mogok ruby (<2 wt % Cr; <0.02 wt % Ga. In trace element ratio plots the Si-Ca-Ga-rich corundum falls into separate fields from the typical Mogok metamorphic fields. The high Ga/Mg ratios (46–521 lie well within the magmatic range (>6, and with other features suggest a potential skarn-like, carbonate-related genesis with a high degree of magmatic fluid input The overall trace element results widen the range of different signatures identified within Mogok gem corundum suites and indicate complex genesis. The expanded geochemical platform, related to a variety of metamorphic, metasomatic and magmatic sources, now provides a wider base for geographic typing of Mogok gem corundum suites. It allows more detailed comparisons with suites from other deposits and will assist identification of Mogok gem corundum sources used in jewelry.

  4. Two Wavelength Ti:sapphire Laser for Ozone DIAL Measurements from Aircraft

    Science.gov (United States)

    Situ, Wen; DeYoung, Russel J.

    1998-01-01

    Laser remote sensing of ozone from aircraft has proven to be a valuable technique for understanding the distribution and dynamics of ozone in the atmosphere. Presently the differential absorption lidar (DIAL) technique, using dual ND:YAG lasers that are doubled to pump dye lasers which in turn are doubled into the UV for the "on" and "off' line lasers, is used on either the NASA DC-8 or P-3 aircraft. Typically, the laser output for each line is 40-mJ and this is split into two beams, one looking up and the other downward, each beam having about 20-mJ. The residual ND:YAG (1.06 micron) and dye laser energies are also transmitted to obtain information on the atmospheric aerosols. While this system has operated well, there are several system characteristics that make the system less than ideal for aircraft operations. The system, which uses separate "on" and "off" line lasers, is quite large and massive requiring valuable aircraft volume and weight. The dye slowly degrades with time requiring replacement. The laser complexity requires a number of technical people to maintain the system performance. There is also the future interest in deploying an ozone DIAL system in an Unpiloted Atmospheric Vehicle (UAV) which would require a total payload mass of less than 150 kg and power requirement of less than 1500 W. A laser technology has emerged that could potentially provide significant enhancements over the present ozone DIAL system. The flashlamp pumped Ti:sapphire laser system is an emerging technology that could reduce the mass and volume over the present system and also provide a system with fewer conversion steps, reducing system complexity. This paper will discuss preliminary results from a flashlamp-pumped Ti:sapphire laser constructed as a radiation source for a UV DIAL system to measure ozone.

  5. Thin film epitaxy, defects and interfaces in gallium nitride/sapphire and zinc oxide/sapphire heterostructures (polar and non-polar) for light emitting diodes

    Science.gov (United States)

    Pant, Punam

    There are three sources of strain in heteroepitaxial growth, lattice misfit; thermal misfit; and growth related defects. The primary aim of the present work was to do a fundamental study of strain and mechanisms for strain relaxation in epitaxial growth of polar-GaN and polar and nonpolar-ZnO thin films grown on sapphire substrates. We have shown that through the paradigm of domain matching epitaxy (DME) these large lattice misfit systems can be grown in a fully relaxed state at the growth temperature. As a result we need to deal with thermal and defect strains only. Growth of GaN and ZnO films on sapphire is characterized by structural inhomogeneities which are caused by impurities, variation in composition or strain. Depending on crystal structure and growth orientation of epitaxial layers, the presence of strain in epilayers can induce various phenomena which can affect device properties. The inhomogeneities due to strain have been favorably used to increase efficiency of solid state light devices based on GaN and ZnO. An understanding of the epitaxial growth mode and strain generation and relaxation processes in these systems is imperative to constructively exploit strain inhomogeneities. Working towards this end, my research work focused on a fundamental study of epitaxial growth and strain relaxation mechanisms in heteroepitaxy of GaN and ZnO and was conducted in the following three parts. Epitaxial Nucleation Layer (NL) for GaN based LEDs. This work addressed the formation of nanostructured GaN NL which is necessary to obtain smooth surface morphology and reduce defects in h-GaN layers for LEDs and lasers. From detailed X-ray and HR-TEM studies, it was determined that NL consists of nanostructured grains which were found to be faulted cubic GaN (c-GaN) with a small fraction of unfaulted c-GaN. From X-ray scans and modeling, we determined c-GaN fraction to be over 63% and rest h-GaN. From HRXRD and Raman spectroscopy it was determined that the NL contained in

  6. Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses.

    Science.gov (United States)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika; Le, Tuan; Stingl, Andreas; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael

    2011-06-20

    For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected.

  7. Characteristics of a Ti:sapphire laser pumped by a Nd:YAG laser and its analysis. Nd:YAG laser reiki Ti:sapphire laser no dosa tokusei to sono kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T.; Masumoto, J.; Mizunami, T.; Maeda, M.; Muraoka, K. (Kyushu Univ., Fukuoka (Japan). Faculty of Engineering)

    1991-06-29

    Although Ti: Sapphire expects of a possibility of being a light source much superior to a dye laser having been used as a wavelength variable laser for spectral analyses, it has a limitation that it does not oscillate directly in the visible and ultraviolet regions. In order to develop a light source that is synchronizable over ultraviolet-near infrared regions, by means of combining a Ti: Sapphire laser of a high peak power, comprising an oscillator and a multistage amplifier, with a non-linear frequency conversion method for harmonic generation and Raman conversion, a prototype Ti:Sapphire laser that is excited by YAG laser second harmonic, and that synchronizes with a prism was fabricated, and its operational characteristics were investigated. As a result, an output energy of 35.6 mJ at a maximum was obtained at a wavelength of 773 nm against an excitation energy of 129 mJ, a conversion efficiency of 38.2% was obtained against the absorption energy of the crystals, and a continuous synchronism was achieved over 750 to 900 nm. 4 refs., 9 figs., 1 tab.

  8. Fabrication of volcano-shaped nano-patterned sapphire substrates using colloidal self-assembly and wet chemical etching.

    Science.gov (United States)

    Geng, Chong; Zheng, Lu; Fang, Huajing; Yan, Qingfeng; Wei, Tongbo; Hao, Zhibiao; Wang, Xiaoqing; Shen, Dezhong

    2013-08-23

    Patterned sapphire substrates (PSS) have been widely used to enhance the light output power in GaN-based light emitting diodes. The shape and feature size of the pattern in a PSS affect its enhancement efficiency to a great degree. In this work we demonstrate the nanoscale fabrication of volcano-shaped PSS using a wet chemical etching approach in combination with a colloidal monolayer templating strategy. Detailed analysis by scanning electron microscopy reveals that the unique pattern shape is a result of the different corrosion-resistant abilities of silica masks of different effective heights during wet chemical etching. The formation of silica etching masks of different effective heights has been ascribed to the silica precursor solution in the interstice of the colloidal monolayer template being distributed unevenly after infiltration. In the subsequent wet chemical etching process, the active reaction sites altered as etching duration was prolonged, resulting in the formation of volcano-shaped nano-patterned sapphire substrates.

  9. Self-forming graphene/Ni patterns on sapphire utilizing the pattern-controlled catalyst metal agglomeration technique

    Science.gov (United States)

    Miyoshi, Makoto; Arima, Yukinori; Kubo, Toshiharu; Egawa, Takashi

    2017-01-01

    We fabricated graphene/Ni patterns directly on sapphire substrates through a self-forming process utilizing the pattern-controlled catalyst metal agglomeration technique, which was accomplished via a thermal annealing process of rectangular Ni patterns preformed on thin amorphous carbon films on sapphire. It was confirmed that graphene films were synthesized along with the preformed Ni patterns as a result of the progress of Ni agglomeration. Notably, a few-layer graphene film was observed in specific areas along the periphery of the preformed Ni patterns. The self-forming graphene/Ni patterns showed ohmic conductivity with a contact resistance ranging from 4 × 104 to 7 × 104 Ω μm.

  10. Scalable MoS2/graphene hetero-structures grown epitaxially on sapphire substrates for phototransistor applications

    Science.gov (United States)

    Chen, Hsuan-An; Chen, Wei-Chan; Sun, Hsu; Lin, Chien-Chung; Lin, Shih-Yen

    2018-02-01

    Bi-layer graphene is grown directly on sapphire substrates by using ethane as the precursor without the assistance of a metal catalyst. A growth model of graphene flake formation in the furnace, followed by a complete film growth is also proposed. Using the graphene/sapphire sample as the new substrate, scalable MoS2 films with good layer number controllability can be grown directly on the substrate. After fabricating the MoS2/graphene hetero-structures into bottom-gate photo-transistors, a Dirac point shift is observed for the device under the light irradiation condition, which is attributed to the extraction of photo-excited electrons in the MoS2 layer to the graphene channel. The photo-voltaic response observed for the photo-transistors may provide a potential application of the 2D material hetero-structure in thin-film solar cells.

  11. High pulse energy, high beam quality microsecond-pulse Ti:sapphire laser at 819.7 nm

    Science.gov (United States)

    Xu, Chang; Guo, Chuan; Yu, Hai-Bo; Wang, Zhi-Min; Zuo, Jun-Wei; Xia, Yuan-Qin; Bian, Qi; Bo, Yong; Gao, Hong-Wei; Guo, Ya-Ding; Zhang, Sheng; Cui, Da-Fu; Peng, Qin-Jun; Xu, Zu-Yan

    2017-03-01

    In this letter, a high pulse energy and high beam quality 819.7 nm Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. At incident pump energy of 774 mJ, the maximum output energy of 89 mJ at 819.7 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, this is the highest pulse energy at 819.7 nm with pulse width of hundred microseconds for a Ti:sapphire laser. The beam quality factor M 2 is measured to be 1.18. This specific wavelength with the high pulse energy and high beam quality at 819.7 nm is a promising light source to create a polychromatic laser guide star together with a home-made 589 nm laser via exciting the sodium atoms in the mesospheric atmosphere.

  12. Fabrication and characterization of nitride-based blue light-emitting diodes on moth-eye patterned sapphire substrate (MPSS)

    Science.gov (United States)

    Tsuchiya, T.; Umeda, S.; Sowa, Mihoko; Kondo, T.; Kitano, T.; Mori, M.; Suzuki, A.; Naniwae, K.; Sekine, H.; Iwaya, M.; Takeuchi, T.; Kamiyama, S.; Akasaki, I.

    2013-03-01

    The fabrication procedure of a moth-eye patterned sapphire substrate (MPSS), which can enhance the light extraction efficiency of nitride-based light emitting diodes (LEDs) has been examined. The optimization of surface morphology after the etching of the MPSS for high-quality GaN growth was also performed. Then, we fabricated MPSS samples with a fixed pitch of 460nm, and corn height ranging from 50 to 350nm. The light extraction efficiency of blue-LEDs grown on a series of MPSS was enhanced about 1.4 times compared with the devices grown on a flat sapphire substrate. We found that if corn height exceeds 150nm, the MPSS effect is sufficiently observed.

  13. Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2011-01-01

    For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W of p....... The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected.......For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W...... of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2...

  14. Analysis of CD4+ and CD8+ T-lymphocytes : A comparison between EPICS XL and Celldyn Sapphire

    OpenAIRE

    Yazdan Panah, Haleh

    2006-01-01

    Flowcytometric technology has been widely used for measurement of the absolute numbers of T-lymphocytes subsets in Human Immunodeficiency virus (HIV), defining the disease state, monitoring antiviral treatment, and identifying any risk for opportunistic infections. A manual preparing of the samples is required. More recently an automated and enclosed blood cell counting, Celldyn Sapphire has been introduced. In this study the performance of the Flow cytometer EPICS XL as a reference method fo...

  15. Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High-T and Dynamic Gas Pressure in Harsh Environments

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hai [Clemson Univ., SC (United States); Tsai, Hai-Lung [Missouri Univ. of Science and Technology, Rolla, MO (United States); Dong, Junhang [Univ. of Cincinnati, OH (United States)

    2014-09-30

    This is the final report for the program “Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High Temperature and Dynamic Gas Pressure in Harsh Environments”, funded by NETL, and performed by Missouri University of Science and Technology, Clemson University and University of Cincinnati from October 1, 2009 to September 30, 2014. Securing a sustainable energy economy by developing affordable and clean energy from coal and other fossil fuels is a central element to the mission of The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). To further this mission, NETL funds research and development of novel sensor technologies that can function under the extreme operating conditions often found in advanced power systems. The main objective of this research program is to conduct fundamental and applied research that will lead to successful development and demonstration of robust, multiplexed, microstructured silica and single-crystal sapphire fiber sensors to be deployed into the hot zones of advanced power and fuel systems for simultaneous measurements of high temperature and gas pressure. The specific objectives of this research program include: 1) Design, fabrication and demonstration of multiplexed, robust silica and sapphire fiber temperature and dynamic gas pressure sensors that can survive and maintain fully operational in high-temperature harsh environments. 2) Development and demonstration of a novel method to demodulate the multiplexed interferograms for simultaneous measurements of temperature and gas pressure in harsh environments. 3) Development and demonstration of novel sapphire fiber cladding and low numerical aperture (NA) excitation techniques to assure high signal integrity and sensor robustness.

  16. Broadband frequency-domain near-infrared spectral tomography using a mode-locked Ti:sapphire laser

    OpenAIRE

    Wang, Jia; Jiang, Shudong; Paulsen, Keith D.; Pogue, Brian W.

    2009-01-01

    Frequency-domain near-infrared (NIR) diffuse spectral tomography with a mode-locked Ti:sapphire laser is presented, providing tunable multiwavelength quantitative spectroscopy with maximal power for thick tissue imaging. The system was developed to show that intrinsically high stability can be achieved with many wavelengths in the NIR range, using a mode-locked signal of 80 MHz with heterodyned lock-in detection. The effect of cumulative noise from multiple wavelengths of data on the reconstr...

  17. Unusual ruby-sapphire transition in alluvial megacrysts, Cenozoic basaltic gem field, New England, New South Wales, Australia

    Science.gov (United States)

    Sutherland, Frederick L.; Graham, Ian T.; Harris, Stephen J.; Coldham, Terry; Powell, William; Belousova, Elena A.; Martin, Laure

    2017-05-01

    Rare ruby crystals appear among prevailing sapphire crystals mined from placers within basaltic areas in the New England gem-field, New South Wales, Australia. New England ruby (NER) has distinctive trace element features compared to those from ruby elsewhere in Australia and indeed most ruby from across the world. The NER suite includes ruby (up to 3370 ppm Cr), pink sapphire (up to 1520 ppm Cr), white sapphire (up to 910 ppm) and violet, mauve, purple, or bluish sapphire (up to 1410 ppm Cr). Some crystals show outward growth banding in this respective colour sequence. All four colour zones are notably high in Ga (up to 310 ppm) and Si (up to 1820 ppm). High Ga and Ga/Mg values are unusual in ruby and its trace element plots (laser ablation-inductively coupled plasma-mass spectrometry) and suggests that magmatic-metasomatic inputs were involved in the NER suite genesis. In situ oxygen isotope analyses (secondary ion mass spectrometry) across the NER suite colour range showed little variation (n = 22; δ18O = 4.4 ± 0.4, 2σ error), and are values typical for corundum associated with ultramafic/mafic rocks. The isolated NER xenocryst suite, corroded by basalt transport and with few internal inclusions, presents a challenge in deciphering its exact origin. Detailed consideration of its high Ga chemistry in relation to the known geology of the surrounding region was used to narrow down potential sources. These include Late Palaeozoic-Triassic fractionated I-type granitoid magmas or Mesozoic-Cenozoic felsic fractionates from basaltic magmas that interacted with early Palaeozoic Cr-bearing ophiolite bodies in the New England Orogen. Other potential sources may lie deeper within lower crust-mantle metamorphic assemblages, but need to match the anomalous high-Ga geochemistry of the New England ruby suite.

  18. High refractive index immersion liquid for super-resolution 3D imaging using sapphire-based aNAIL optics

    CERN Document Server

    Laskar, Junaid M; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

    2015-01-01

    Optically-transparent immersion liquids with refractive index (n ~ 1.77) to match sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr$_{3}$) salt dissolved in liquid diiodomethane (CH$_{2}$I$_{2}$) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n = 1.74 (pure) to n = 1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially-available immersion liquids. This refractive index matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA = 1.17) and long working distance (WD = 12 mm). This opens up new possibilities ...

  19. Study on effect of the surface variation of colloidal silica abrasive during chemical mechanical polishing of sapphire

    Science.gov (United States)

    Bun-Athuek, Natthaphon; Yoshimoto, Yutaka; Sakai, Koya; Khajornrungruang, Panart; Suzuki, Keisuke

    2017-07-01

    The surface and diameter size variations of colloidal silica particles during the chemical mechanical polishing (CMP) of sapphire substrates were investigated using different particle diameters of 20 and 55 nm. Dynamic light scattering (DLS) results show that the silica particles became larger after CMP under both conditions. The increase in particle size in the slurry was proportional to the material removal amount (MRA) as a function of the removed volume of sapphire substrates by CMP and affected the material removal rate (MRR). Transmission electron microscopy (TEM) images revealed an increase in the size of the fine particles and a change in their surface shape in the slurry. The colloidal silica was coated with the material removed from the substrate during CMP. In this case, the increase in the size of 55 nm diameter particles is larger than that of 20 nm diameter particles. X-ray fluorescence spectrometry (XRF) results indicate that the aluminum element from polished sapphire substrates adhered to the surfaces of silica particles. Therefore, MRR decreases with increasing of polishing time owing to the degradation of particles in the slurry.

  20. Te Monolayer-Driven Spontaneous van der Waals Epitaxy of Two-dimensional Pnictogen Chalcogenide Film on Sapphire.

    Science.gov (United States)

    Hwang, Jae-Yeol; Kim, Young-Min; Lee, Kyu Hyoung; Ohta, Hiromichi; Kim, Sung Wng

    2017-10-11

    Demands on high-quality layer structured two-dimensional (2D) thin films such as pnictogen chalcogenides and transition metal dichalcogenides are growing due to the findings of exotic physical properties and potentials for device applications. However, the difficulties in controlling epitaxial growth and the unclear understanding of van der Waals epitaxy (vdWE) for a 2D chalcogenide film on a three-dimensional (3D) substrate have been major obstacles for the further advances of 2D materials. Here, we exploit the spontaneous vdWE of a high-quality 2D chalcogenide (Bi 0.5 Sb 1.5 Te 3 ) film by the chalcogen-driven surface reconstruction of a conventional 3D sapphire substrate. It is verified that the in situ formation of a pseudomorphic Te atomic monolayer on the surface of sapphire, which results in a dangling bond-free surface, allows the spontaneous vdWE of 2D chalcogenide film. Since this route uses the natural surface reconstruction of sapphire with chalcogen under vacuum condition, it can be scalable and easily utilized for the developments of various 2D chalcogenide vdWE films through conventional thin-film fabrication technologies.

  1. Ultrasensitive label-free detection of DNA hybridization by sapphire-based graphene field-effect transistor biosensor

    Science.gov (United States)

    Xu, Shicai; Jiang, Shouzhen; Zhang, Chao; Yue, Weiwei; Zou, Yan; Wang, Guiying; Liu, Huilan; Zhang, Xiumei; Li, Mingzhen; Zhu, Zhanshou; Wang, Jihua

    2018-01-01

    Graphene has attracted much attention in biosensing applications for its unique properties. Because of one-atom layer structure, every atom of graphene is exposed to the environment, making the electronic properties of graphene are very sensitive to charged analytes. Therefore, graphene is an ideal material for transistors in high-performance sensors. Chemical vapor deposition (CVD) method has been demonstrated the most successful method for fabricating large area graphene. However, the conventional CVD methods can only grow graphene on metallic substrate and the graphene has to be transferred to the insulating substrate for further device fabrication. The transfer process creates wrinkles, cracks, or tears on the graphene, which severely degrade electrical properties of graphene. These factors severely degrade the sensing performance of graphene. Here, we directly fabricated graphene on sapphire substrate by high temperature CVD without the use of metal catalysts. The sapphire-based graphene was patterned and make into a DNA biosensor in the configuration of field-effect transistor. The sensors show high performance and achieve the DNA detection sensitivity as low as 100 fM (10-13 M), which is at least 10 times lower than prior transferred CVD G-FET DNA sensors. The use of the sapphire-based G-FETs suggests a promising future for biosensing applications.

  2. c-plane ZnO on a-plane sapphire: Inclusion of (1 1 bar 01) domains

    Science.gov (United States)

    Madel, M.; Neusser, G.; Simon, U.; Mizaikoff, B.; Thonke, K.

    2015-06-01

    The influence of metal-free ZnO nanoseed-layers on the growth of ZnO films on a-plane sapphire substrates by chemical vapor deposition (CVD) is investigated. For epitaxial films with a high density of (1 1 bar 01) inclusions we find a twofold orientation of these inclusions with the epitaxial relationships (11 2 bar 0) Al2O3 ∥(1 1 bar 01) ZnO and (10 1 bar 4) Al2O3 ∥(0001)ZnO. HRXRD measurements show that these inclusions are tilted by approx. 1.45° towards the sapphire substrate as a result of strain relaxation during heteroepitaxial growth. Numerical simulations with ANSYS confirm this as the energetically favorable situation. Detailed HRXRD and EBSD studies show that the occurrence of (1 1 bar 01) oriented nanocrystallites during nucleation is responsible for the formation of dislocations, and that the nucleation process has a pronounced influence on the crystal quality of c-plane ZnO films grown on a-plane sapphire.

  3. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Science.gov (United States)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio

    2017-02-01

    Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO2 probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  4. GaN-based Schottky barrier ultraviolet photodetectors with graded doping on patterned sapphire substrates

    Science.gov (United States)

    Mou, Wenjie; Zhao, Linna; Chen, Leilei; Yan, Dawei; Ma, Huarong; Yang, Guofeng; Gu, Xiaofeng

    2017-07-01

    In this paper, we demonstrate high performance GaN-based Schottky-barrier ultraviolet (UV) photodetectors with graded doping prepared on patterned sapphire substrates. The fabricated devices exhibit an extremely low dark current density of ∼1.3 × 10-8 A/cm2 under -5 V bias, a large UV-to-visible light rejection ratio of ∼4.2 × 103, and a peak external quantum efficiency of ∼50.7% at zero bias. Even in the deeper 250-360 nm range, the average external quantum efficiency still remains ∼40%. From the transient response characteristics, the average rising and falling time constants are estimated ∼115 μs and 120 μs, respectively, showing a good electrical and thermal reliability. The specific detectivities D∗, limited by the thermal equilibrium noise and the low-frequency 1/f noise, are derived ∼5.5 × 1013 cm Hz1/2/W (at 0 V) and ∼2.68 × 1010 cm Hz1/2 W-1 (at -5 V), respectively.

  5. Effect of dual buffer layer structure on the epitaxial growth of AlN on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, D.G., E-mail: dgzhao@red.semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Jiang, D.S.; Wu, L.L.; Le, L.C.; Li, L.; Chen, P.; Liu, Z.S. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Zhu, J.J.; Wang, H.; Zhang, S.M. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Yang, H. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer A dual AlN buffer layer structure is proposed to grow AlN films. Black-Right-Pointing-Pointer AlN films could be improved obviously by using the dual AlN buffer layer. Black-Right-Pointing-Pointer The physical mechanism are discussed. - Abstract: A dual AlN buffer layer structure, including an isolated layer and a nucleation layer, is proposed to improve the growth of AlN films on sapphire substrate by metal organic chemical vapor deposition. This method is aimed to weaken the negative nitridation effect and improve lateral growth condition in the initial growth stage. It is found that suitably increasing the thickness of the nucleation layer is in favor of a better structural quality of the AlN film. An examination of surface morphology by atomic force microscopy suggests that the thicker the dual AlN buffer layer, the rougher the surface, and a higher quality of AlN epilayer is resulted.

  6. Sapphire capillaries for laser-driven wakefield acceleration in plasma. Fs-laser micromachining and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Schwinkendorf, Jan-Patrick

    2012-08-15

    Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. However, several detrimental effects such as laser diffraction, electron-wake dephasing and laser depletion may terminate the acceleration process. Two of these phenomena can be mitigated or avoided by the application of capillary waveguides, e.g. fabricated out of sapphire for longevity. Capillaries may compensate for laser diffraction like a fiber and allow for the creation of tapered gas-density profiles working against the dephasing between the accelerating wave and the particles. Additionally, they offer the possibility of controlled particle injection. This thesis is reporting on the set up of a laser for fs-micromachining of capillaries of almost arbitrary shapes and a test stand for density-profile characterization. These devices will permit the creation of tailored gas-density profiles for controlled electron injection and acceleration inside plasma.

  7. Continuous-Wave Alkali Vapor Laser Pumped by a Ti-sapphire Laser with Narrow Linewidth

    Science.gov (United States)

    Cai, H.; An, G. F.; Dai, K.; Wang, Y.; Zhang, W.; Han, J. H.; Rong, K. P.; Yu, H.; Wang, S. Y.; Wang, H. Y.; Xue, L. P.; Zhou, J.

    2017-06-01

    We have experimentally demonstrated the continuous wave rubidium and cesium lasers pumped by a Ti-sapphire laser with the linewidth of about 5 MHz. The pump and laser beams were orthogonally polarized and they can be separated by a polarized beam splitter (PBS). Two 4-cm-long cells were respectively filled with metallic rubidium and cesium as well as 300 Torr ethane as a buffer gas. A series of output couplers at different cell temperatures have been used and the optimal parameters have been found for earning the highest output. As a result, we have achieved a maximum output power of 111 mW with the optical to optical efficiency of 18.4% for a rubidium laser and a maximum output power of 136 mW with the optical to optical efficiency of 30% for a cesium laser, respectively. By considering there are no anti-reflection coatings on the surfaces of two cell end-windows, the output should be improved if the transmission attenuation is effectively decreased in the future.

  8. Dash line glass- and sapphire-cutting with high power USP laser

    Science.gov (United States)

    Mishchik, Konstantin; Chassagne, Bruno; Javaux-Léger, Clémentine; Hönninger, Clemens; Mottay, Eric; Kling, Rainer; Lopez, John

    2016-03-01

    Glass cutting is a subject of high interest for flat panel display and consumer electronics industries. Among laser-based, water jet-based and diamond tool-based existing solutions, ultra-short pulses (USP) appear as a promising technology since this laser technology has the unique capacity to produce highly localized bulk modification owing to non-linear absorption. The cutting using USP lasers could be performed either by full ablation which is slow and generates a lot of dust, by controlled fracture propagation which is slow as well and may lead to path deviation, by stealth dicing which produces rough sidewalls, or by self-breaking induced by in-volume laser irradiation. The laser treatment is often continuous which is not necessary to perform glass cutting and may lead to over-exposure. In this paper we report on single pass glass and sapphire cutting using an USP laser (20W @200kHz or 8W@2MHz) using dash line laser treatment along the cutting trajectory. In-volume energy deposition was done along the glass thickness owing to a Bessel beam. The results will be discussed in terms of sidewall profile and roughness, path deviation, rim sharpness, energy dose and feed rate. Dash line treatment enables to tune the energy deposition and to produce the cutting effect but with a narrower heat affected zone, a better sidewall quality and a more accurate trajectory control of the cutting path.

  9. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  10. Modeling of dopant segregation in sapphire single crystal fibre growth by Micro-Pulling-Down method

    Science.gov (United States)

    Wenjia, Su; Duffar, Thierry; Nehari, Abdeljelil; Kononets, Valerii; Lebbou, Kheirreddine

    2017-09-01

    Experiments and numerical simulations are conducted in order to study the causes and solutions for the Ti inhomogeneity problem in Ti doped sapphire Micro-Pulling-Down (μ-PD) growth. The measurement and modeling of the thermal and flow fields, electromagnetic field, Ti concentration in the molten zone and along the fibre axis are compared. For the mean Ti concentration along the fibre and temperature along the iridium crucible, the modeling results are consistent with experiments. Results showed that for high pulling rate, the mass transfer in the capillary is dominated by convection. Marangoni convection is strong in the meniscus due to the large temperature gradient, which has great impact on the Ti distribution for different fibre radii. For high pulling rate, Ti concentration increases quickly from the seed along the fibre axis, and reaches a constant value after about 0.5-2 mm. Radial segregation is high for large diameter fibres. The constant Ti concentration along the fibre axis is increasing when increasing the fibre radius from 0.2 to 0.6 mm. For 0.8 mm, it decreases due to the change of the vortex. At low growth rate, the transport in the capillary is diffusive, back to the crucible, which leads to a Scheil-like Ti distribution, in full agreement with the experimental results.

  11. Control of melt-crystal interface shape during sapphire crystal growth by heat exchanger method

    Science.gov (United States)

    Wu, Ming; Liu, Lijun; Ma, Wencheng

    2017-09-01

    We numerically investigate the melt-crystal interface shape during the early stage of the solidification process when the crystal diameter increases. The contact angle between the melt-crystal interface and the crucible bottom wall is found obtuse during this stage, which is unfavorable for the crystal quality. We found that the obtuse contact angle is caused by the thermal resistance difference between the sapphire crystal and melt as well as the insufficient cooling effect of the crucible bottom. Two approaches are proposed to suppress the obtuse contact angle. The first approach is to increase the emissivity of the outer surface of crucible bottom. The second approach is to install a heat shield near the crucible bottom. The reduction of the emissivity of the heat shield is also favorable for the suppression of the obtuse contact angle. Compared with the increase of the emissivity of the crucible bottom, the installation of a heat shield is a more effective approach to prevent the appearance of an obtuse contact angle for the sake of reliability since a molybdenum heat shield can be reused and will not induce other impurities.

  12. High efficiency resonance ionization of palladium with Ti:sapphire lasers

    Science.gov (United States)

    Kron, T.; Liu, Y.; Richter, S.; Schneider, F.; Wendt, K.

    2016-09-01

    This work presents the development and testing of highly efficient excitation schemes for resonance ionization of palladium. To achieve the highest ionization efficiencies, a high-power, high repetition rate Ti:sapphire laser system was used and 2-step, 3-step and 4-step schemes were investigated and compared. Starting from different excited steps, the frequencies of the final ionization steps were tuned across the full accessible spectral range of the laser system, revealing several autoionizing Rydberg series, which converge towards the energetically higher lying state 4{{{d}}}9{}2{{{D}}}3/2 of the Pd+ ion ground state configuration. Through proper choice of these excitation steps, we developed a highly efficient, fully resonant 3-step excitation scheme, which lead to overall efficiencies of 54.3(1.4) % and 59.7(2.1) %, measured at two independent mass separator setups. To our knowledge, these are presently the highest efficiency values ever achieved with a resonance ionization laser ion source.

  13. Narrow linewidth operation of the RILIS titanium: Sapphire laser at ISOLDE/CERN

    Energy Technology Data Exchange (ETDEWEB)

    Rothe, S., E-mail: sebastian.rothe@cern.ch [CERN, Geneva (Switzerland); Institut für Physik, Johannes Gutenberg-Universität, Mainz (Germany); Fedosseev, V.N. [CERN, Geneva (Switzerland); Kron, T. [Institut für Physik, Johannes Gutenberg-Universität, Mainz (Germany); Marsh, B.A. [CERN, Geneva (Switzerland); Rossel, R.E. [CERN, Geneva (Switzerland); Institut für Physik, Johannes Gutenberg-Universität, Mainz (Germany); Wendt, K.D.A. [Institut für Physik, Johannes Gutenberg-Universität, Mainz (Germany)

    2013-12-15

    Highlights: • The narrow linewidth operation has been demonstrated for the CERN Ti:Sa laser system. • The optical spectrum emitted by the laser was characterized by different techniques (interferometry, laser spectroscopy of a known isotope). • The suitability (narrow linewidth) of this laser for in-source laser spectroscopy was demonstrated. -- Abstract: A narrow linewidth operating mode for the Ti:sapphire laser of the CERN ISOLDE Resonance Ionization Laser Ion Source (RILIS) has been developed. This satisfies the laser requirements for the programme of in-source resonance ionization spectroscopy measurements and improves the selectivity for isomer separation using RILIS. A linewidth reduction from typically 10 GHz down to 1 GHz was achieved by the intra-cavity insertion of a second (thick) Fabry-Pérot etalon. Reliable operation during a laser scan was achieved through motorized control of the tilt angle of each etalon. A scanning, stabilization and mode cleaning procedure was developed and implemented in LabVIEW. The narrow linewidth operation was confirmed in a high resolution spectroscopy study of francium isotopes by the Collinear Resonance Ionization Spectroscopy experiment. The resulting laser scans demonstrate the suitability of the laser, in terms of linewidth, spectral purity and stability for high resolution in-source spectroscopy and isomer selective ionization using the RILIS.

  14. Narrow linewidth operation of the RILIS titanium: Sapphire laser at ISOLDE/CERN

    Science.gov (United States)

    Rothe, S.; Fedosseev, V. N.; Kron, T.; Marsh, B. A.; Rossel, R. E.; Wendt, K. D. A.

    2013-12-01

    A narrow linewidth operating mode for the Ti:sapphire laser of the CERN ISOLDE Resonance Ionization Laser Ion Source (RILIS) has been developed. This satisfies the laser requirements for the programme of in-source resonance ionization spectroscopy measurements and improves the selectivity for isomer separation using RILIS. A linewidth reduction from typically 10 GHz down to 1 GHz was achieved by the intra-cavity insertion of a second (thick) Fabry-Pérot etalon. Reliable operation during a laser scan was achieved through motorized control of the tilt angle of each etalon. A scanning, stabilization and mode cleaning procedure was developed and implemented in LabVIEW. The narrow linewidth operation was confirmed in a high resolution spectroscopy study of francium isotopes by the Collinear Resonance Ionization Spectroscopy experiment. The resulting laser scans demonstrate the suitability of the laser, in terms of linewidth, spectral purity and stability for high resolution in-source spectroscopy and isomer selective ionization using the RILIS.

  15. Photoreflectance study of GaN grown on SiN treated sapphire substrate by MOVPE

    Science.gov (United States)

    Bouzidi, M.; Benzarti, Z.; Halidou, I.; Chine, Z.; Bchetnia, A.; El Jani, B.

    2015-08-01

    GaN films were grown on silicon nitride (SiN) treated c-plane sapphire substrates in a home-made vertical reactor by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). In order to obtain different thickness layers, the growth procedure was interrupted at diverse stages using in-situ laser reflectometry. The structural and optical properties of obtained samples were investigated by high resolution X-ray diffraction (HRXRD) and photoreflectance (PR). In the 0.7-2 μm epilayer thickness range, the dislocation density decreases and remains roughly constant above this range. For fully coalesced layers, PR measurements at 11 K reveal the presence of well resolved excitonic transitions related to A, B and C excitons. A strong correlation between dislocation density and exciton linewidths is observed. Based on theoretical approaches and experimental results, the electronic band structure modification of GaN films due to isotropic biaxial strain was investigated. The valence band deformation potentials D3 and D4, interband hydrostatic deformation potentials a1 and a2, spin-orbit Δso and crystal field Δcr parameters were re-examined and found to be 8.2 eV, -4.1 eV, -3.8 eV, -12 eV, 15.6 meV and 16.5 meV, respectively.

  16. Ultrathin Films of VO2 on r-Cut Sapphire Achieved by Postdeposition Etching.

    Science.gov (United States)

    Yamin, Tony; Wissberg, Shai; Cohen, Hagai; Cohen-Taguri, Gili; Sharoni, Amos

    2016-06-15

    The metal-insulator transition (MIT) properties of correlated oxides thin films, such as VO2, are dramatically affected by strain induced at the interface with the substrate, which usually changes with deposition thickness. For VO2 grown on r-cut sapphire, there is a minimum deposition thickness required for a significant MIT to appear, around 60 nm. We show that in these thicker films an interface layer develops, which accompanies the relaxation of film strain and enhanced electronic transition. If these interface dislocations are stable at room temperature, we conjectured, a new route opens to control thickness of VO2 films by postdeposition thinning of relaxed films, overcoming the need for thickness-dependent strain-engineered substrates. This is possible only if thinning does not alter the films' electronic properties. We find that wet etching in a dilute NaOH solution can effectively thin the VO2 films, which continue to show a significant MIT, even when etched to 10 nm, for which directly deposited films show nearly no transition. The structural and chemical composition were not modified by the etching, but the grain size and film roughness were, which modified the hysteresis width and magnitude of the MIT resistance change.

  17. A sapphire fibre thermal probe based on fast Fourier transform and phase-lock loop

    Science.gov (United States)

    Wang, Yu-Tian; Wang, Dong-Sheng; Ge, Wen-Qian; Cui, Li-Chao

    2006-05-01

    A sapphire fibre thermal probe with Cr3+ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and ability to withstand high temperature in a detection range from room temperature to 450°C. Based on the fast Fourier transform (FFT), the fluorescence lifetime is obtained from the tangent function of phase angle of the non-zeroth terms in the FFT result. This method has advantages such as quick calculation, high accuracy and immunity to the background noise. This FFT method is compared with other traditional fitting methods, indicating that the standard deviation of the FFT method is about half of that of the Prony method and about 1/6 of that of the log-fit method. And the FFT method is immune to the background noise involved in a signal. So, the FFT method is an excellent way of processing signals. In addition, a phase-lock amplifier can effectively suppress the noise.

  18. Investigation of High Precision Marine Pressure Sensor Based on Silicon-on-Sapphire

    Directory of Open Access Journals (Sweden)

    LI Hong-Zhi

    2016-07-01

    Full Text Available As one of parameter in marine hydrographic survey, seawater pressure plays an important role in marine research, tsunami forecast, and marine engineering equipment. In practical application, many marine parameters are also relative to pressure value, and its value is helpful to provide a complete data model. Therefore, it makes a demand for high performance of pressure sensor. In order to realize a long-term and high precision measurement, a marine pressure sensor based on silicon stain resistance is presented. This sensor applies the sapphire as substrate material to reduce the error caused by inconsistent deformation between sensitive component and substrate. A stress cup structure is designed to improve its sensitivity. By using a series of processing technology and packaging method, the structure of marine pressure sensor has a good mechanical strength and corrosion resistance. Considered that the output signal is affected by temperature drift, a new algorithm compensation is introduced. From experimental results, the output voltage of sensor is almost independent of temperature and the maximum error is controlled within 0.05 %. This high performance pressure sensor could bring a large application in marine detection.

  19. Laser-induced microexplosion confined in the bulk of a sapphire crystal: evidence of multimegabar pressures.

    Science.gov (United States)

    Juodkazis, S; Nishimura, K; Tanaka, S; Misawa, H; Gamaly, E G; Luther-Davies, B; Hallo, L; Nicolai, P; Tikhonchuk, V T

    2006-04-28

    Extremely high pressures (approximately 10 TPa) and temperatures (5 x 10(5) K) have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside a sapphire crystal. The laser pulse creates an intensity over 10(14) W/cm2 converting material within the absorbing volume of approximately 0.2 microm3 into plasma in a few fs. A pressure of approximately 10 TPa, far exceeding the strength of any material, is created generating strong shock and rarefaction waves. This results in the formation of a nanovoid surrounded by a shell of shock-affected material inside undamaged crystal. Analysis of the size of the void and the shock-affected zone versus the deposited energy shows that the experimental results can be understood on the basis of conservation laws and be modeled by plasma hydrodynamics. Matter subjected to record heating and cooling rates of 10(18) K/s can, thus, be studied in a well-controlled laboratory environment.

  20. Grain boundary structure and solute segregation in titanium-doped sapphire bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Seth Thomas [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Solute segregation to ceramic grain boundaries governs material processing and microstructure evolution, and can strongly influence material properties critical to engineering performance. Understanding the evolution and implications of grain boundary chemistry is a vital component in the greater effort to engineer ceramics with controlled microstructures. This study examines solute segregation to engineered grain boundaries in titanium-doped sapphire (Al2O3) bicrystals, and explores relationships between grain boundary structure and chemistry at the nanometer scale using spectroscopic and imaging techniques in the transmission electron microscope (TEM). Results demonstrate dramatic changes in solute segregation stemming from small fluctuations in grain boundary plane and structure. Titanium and silicon solute species exhibit strong tendencies to segregate to non-basal and basal grain boundary planes, respectively. Evidence suggests that grain boundary faceting occurs in low-angle twis t boundaries to accommodate nonequilibrium solute segregation related to slow specimen cooling rates, while faceting of tilt grain boundaries often occurs to expose special planes of the coincidence site lattice (CSL). Moreover, quantitative analysis of grain boundary chemistry indicates preferential segregation of charged defects to grain boundary dislocations. These results offer direct proof that static dislocations in ionic materials can assume a net charge, and emphasize the importance of interactions between charged point, line, and planar defects in ionic materials. Efforts to understand grain boundary chemistry in terms of space charge theory, elastic misfit and nonequilibrium segregation are discussed for the Al2O3 system.

  1. Formation of graphitic carbon nitride and boron carbon nitride film on sapphire substrate

    Science.gov (United States)

    Kosaka, Maito; Urakami, Noriyuki; Hashimoto, Yoshio

    2018-02-01

    As a novel production method of boron carbon nitride (BCN) films, in this paper, we present the incorporation of B into graphitic carbon nitride (g-C3N4). First, we investigated the formation of g-C3N4 films via chemical vapor deposition (CVD) using melamine powder as the precursor. The formation of g-C3N4 films on a c-plane sapphire substrate was confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy measurements. The deposition temperature of g-C3N4 films was found to be suitable between 550 and 600 °C since the degradation and desorption of hexagonal C–N bonds should be suppressed. As for BCN films, we prepared BCN films via two-zone extended CVD using ammonia borane as the B precursor. Several XPS signals from B, C, and N core levels were detected from B-incorporated g-C3N4 films. While the N composition was almost constant, the marked tendencies for increasing B composition and decreasing C composition were achieved with the increase in the B incorporation, indicating the incorporation of B atoms by the substitution for C atoms. Optical absorptions were shifted to the high-energy side by B incorporation, which indicates the successful formation of BCN films using melamine and ammonia borane powders as precursors.

  2. Surface-Energy-Anisotropy-Induced Orientation Effects on RayleighInstabilities in Sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Santala, Melissa; Glaeser, Andreas M.

    2006-01-01

    Arrays of controlled-geometry, semi-infinite pore channels of systematically varied crystallographic orientation were introduced into undoped m-plane (10{bar 1}0) sapphire substrates using microfabrication techniques and ion-beam etching and subsequently internalized by solid-state diffusion bonding. A series of anneals at 1700 C caused the breakup of these channels into discrete pores via Rayleigh instabilities. In all cases, channels broke up with a characteristic wavelength larger than that expected for a material with isotropic surface energy, reflecting stabilization effects due to surface-energy anisotropy. The breakup wavelength and the time required for complete breakup varied significantly with channel orientation. For most orientations, the instability wavelength for channels of radius R was in the range of 13.2R-25R, and complete breakup occurred within 2-10 h. To first order, the anneal times for complete breakup scale with the square of the breakup wavelength. Channels oriented along a <11{bar 2}0> direction had a wavelength of {approx} 139R, and required 468 h for complete breakup. Cross-sectional analysis of channels oriented along a <11{bar 2}0> direction showed the channel to be completely bounded by stable c(0001), r{l_brace}{bar 1}012{r_brace}, and s{l_brace}10{bar 1}1{r_brace} facets.

  3. Infrared Reflectance Analysis of Epitaxial n-Type Doped GaN Layers Grown on Sapphire

    Science.gov (United States)

    Tsykaniuk, Bogdan I.; Nikolenko, Andrii S.; Strelchuk, Viktor V.; Naseka, Viktor M.; Mazur, Yuriy I.; Ware, Morgan E.; DeCuir, Eric A.; Sadovyi, Bogdan; Weyher, Jan L.; Jakiela, Rafal; Salamo, Gregory J.; Belyaev, Alexander E.

    2017-06-01

    Infrared (IR) reflectance spectroscopy is applied to study Si-doped multilayer n+/n0/n+-GaN structure grown on GaN buffer with GaN-template/sapphire substrate. Analysis of the investigated structure by photo-etching, SEM, and SIMS methods showed the existence of the additional layer with the drastic difference in Si and O doping levels and located between the epitaxial GaN buffer and template. Simulation of the experimental reflectivity spectra was performed in a wide frequency range. It is shown that the modeling of IR reflectance spectrum using 2 × 2 transfer matrix method and including into analysis the additional layer make it possible to obtain the best fitting of the experimental spectrum, which follows in the evaluation of GaN layer thicknesses which are in good agreement with the SEM and SIMS data. Spectral dependence of plasmon-LO-phonon coupled modes for each GaN layer is obtained from the spectral dependence of dielectric of Si doping impurity, which is attributed to compensation effects by the acceptor states.

  4. Mosaic Structure Characterization of the AlInN Layer Grown on Sapphire Substrate

    Directory of Open Access Journals (Sweden)

    Engin Arslan

    2014-01-01

    Full Text Available The 150 nm thick, (0001 orientated wurtzite-phase Al1−xInxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 µm template/(0001 sapphire substrate. The indium (x concentration of the Al1−xInxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x, lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002 and asymmetric (10–15 reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles.

  5. Weight of Production of Emeralds, Rubies, Sapphires, and Tanzanite from 1995 Through 2005

    Science.gov (United States)

    Yager, Thomas R.; Menzie, W. David; Olson, Donald W.

    2008-01-01

    U.S. Geological Survey (USGS) historically has not attempted to report comprehensive world production of gemstones on a country basis. This was because estimation of gemstone production is inherently difficult due to the fragmentary nature of the industry, the lack of governmental oversight or reporting in many countries where colored gemstones are mined, and the wide variation in quality between individual gemstones. Unlike diamonds, which, with the exception of the alluvial stones of West Africa, are mainly produced by large international mining companies and evaluated, cut, and marketed through a highly developed pricing structure and complex commercial arrangements, colored gemstones are mainly mined by individuals or small companies and have less developed evaluation and marketing arrangements. The trading centers for colored gems are smaller and less well known than the diamond centers. Colored gemstones, like alluvial diamonds, have the potential to be used to fund civil conflicts and other illegal activities, and because trade in colored gemstones is less organized than that of diamonds, they offer less opportunity for effective regulation of their trade. And, like diamond, until the recent advent of the Kimberley Process no generally accepted estimates of colored gemstone production globally or by producing country have existed. The present paper is a first attempt to develop production statistics for the three precious gems -emeralds, rubies, and sapphires - and tanzanite tanzanite, a semi-precious gem. The data consist of the weight of production of each of the gemstones from 1995 through 2005. Preliminary data on the weights of gemstone production were presented as a poster session at the Gemological Institute of America's Gemological Research Conference in San Diego, CA, in 2006, and as a published abstract (Yager, 2006) in an attempt to gather response to the estimates. The USGS continues to welcome information and suggestions that would improve the

  6. Transfer-free graphene synthesis on sapphire by catalyst metal agglomeration technique and demonstration of top-gate field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Miyoshi, Makoto, E-mail: miyoshi.makoto@nitech.ac.jp; Arima, Yukinori; Kubo, Toshiharu; Egawa, Takashi [Research Center for Nano Device and Advanced Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Mizuno, Masaya [Research Center for Nano Device and Advanced Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Soga, Tetsuo [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

    2015-08-17

    Transfer-free graphene synthesis was performed on sapphire substrates by using the catalyst metal agglomeration technique, and the graphene film quality was compared to that synthesized on sputtered SiO{sub 2}/Si substrates. Raman scattering measurements indicated that the graphene film on sapphire has better structural qualities than that on sputtered SiO{sub 2}/Si substrates. The cross-sectional transmission microscopic study also revealed that the film flatness was drastically improved by using sapphire substrates instead of sputtered SiO{sub 2}/Si substrates. These quality improvements seemed to be due the chemical and thermal stabilities of sapphire. Top-gate field-effect transistors were fabricated using the graphene films on sapphire, and it was confirmed that their drain current can be modulated with applied gate voltages. The maximum field-effect mobilities were estimated to be 720 cm{sup 2}/V s for electrons and 880 cm{sup 2}/V s for holes, respectively.

  7. A simple digital system for tuning and long-term frequency stabilisation of a CW Ti:Sapphire laser

    OpenAIRE

    Beterov, I. I.; Markovski, A.; Kobtsev, S. M.; Yakshina, E. A.; Entin, V. M.; Tretyakov, D. B.; Baraulya, V. I.; Ryabtsev, I. I.

    2014-01-01

    We have implemented a simple and cost-effective digital system for long-term frequency stabilisation and locking to an arbitrary wavelength of the single-frequency ring CW Ti:Sapphire laser. This system is built around two confocal Fabry-Perot cavities, one of which is used to narrow short-term line width of the laser and the other to improve long-term stability of the laser frequency. The second interferometer is also in the path of the radiation from an external-cavity diode laser stabilize...

  8. Occurrence of cubic GaN and strain relaxation in GaN buffer layers grown by low-pressure metalorganic vapor phase epitaxy on (0001) sapphire substrates

    Science.gov (United States)

    Cheng, Lisen; Zhou, Kuan; Zhang, Ze; Zhang, Guoyi; Yang, Zhijian; Tong, Yuzhen

    1999-02-01

    Investigations on GaN buffer layers grown by low-pressure metalorganic vapor phase epitaxy on (0001) sapphire substrates indicated that the mechanisms by way of which GaN buffer layers relax stresses introduced by the lattice mismatch and thermal expansion coefficient difference between GaN epilayer and sapphire substrate are related to both the crystallographic structure of GaN and thickness of the buffer layers. Beside forming misfit dislocations, mismatch-induced stresses can also be relaxed by forming stacking faults and microtwin boundaries parallel to (11-1) of GaN near the interface between GaN and sapphire substrate in cubic GaN buffer layers. It was found that, in cubic GaN buffer layers, there exists a critical thickness within which the stacking faults and/or microtwin boundaries parallel to (11-1) of GaN can be formed. This critical value is determined to be 50 nm.

  9. Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Adikimenakis, A.; Aretouli, K. E.; Tsagaraki, K.; Androulidaki, M.; Georgakilas, A. [Microelectronics Research Group (MRG), IESL, FORTH, P.O. Box 1385, GR 711 10 Heraklion Crete, Greece and Physics Department, University of Crete, GR 710 03 Heraklion Crete (Greece); Lotsari, A.; Dimitrakopulos, G. P., E-mail: gdim@auth.gr; Kehagias, Th.; Komninou, Ph. [Physics Department, Aristotle University of Thessaloniki, GR 541 24, Thessaloniki (Greece)

    2015-06-28

    The spontaneous growth of GaN nanopillars (NPs) by direct plasma-assisted molecular beam epitaxy on nitridated r-plane sapphire substrates has been studied. The emanation of metal-polarity NPs from inside an a-plane nonpolar GaN film was found to depend on both the substrate nitridation and the growth conditions. The density of NPs increased with increasing the duration of the nitridation process and the power applied on the radio-frequency plasma source, as well as the III/V flux ratio, while variation of the first two parameters enhanced the roughness of the substrate's surface. Transmission electron microscopy (TEM) techniques were employed to reveal the structural characteristics of the NPs and their nucleation mechanism from steps on the sapphire surface and/or interfacial semipolar GaN nanocrystals. Lattice strain measurements showed a possible Al enrichment of the first 5–6 monolayers of the NPs. By combining cross-sectional and plan-view TEM observations, the three-dimensional model of the NPs was constructed. The orientation relationship and interfacial accommodation between the NPs and the nonpolar a-plane GaN film were also elucidated. The NPs exhibited strong and narrow excitonic emission, suggesting an excellent structural quality.

  10. Air-void embedded GaN-based light-emitting diodes grown on laser drilling patterned sapphire substrates

    Science.gov (United States)

    Liu, Hao; Li, Yufeng; Wang, Shuai; Feng, Lungang; Xiong, Han; Su, Xilin; Yun, Feng

    2016-07-01

    Air-void structure was introduced in GaN-based blue light-emitting diodes (LED) with one-step growth on periodic laser drilling patterned sapphire substrate, which free of any photolithography or wet/dry etching process. The influence of filling factors (FF) of air-void on crystal quality and optical performance were investigate. Transmission electron microscopy images and micro-Raman spectroscopy indicated that the dislocation was bended and the partially compressed strain was released. When FF was 55.43%, compared with the LED structure grown on flat sapphire substrate, the incorporation of air-void was observed to reduce the compressed stress of ˜20% and the luminance intensity has improved by 128%. Together with the simulated reflection intensity enhancement by finite difference time-domain (FDTD) method, we attribute the enhanced optical performance to the combined contribution of strong back-side light reflection of air-void and better GaN epitaxial quality. This approach provides a simple replacement to the conventional air-void embedded LED process.

  11. Study of defect management in the growth of semipolar (11-22) GaN on patterned sapphire

    Science.gov (United States)

    Vennéguès, P.; Tendille, F.; De Mierry, P.

    2015-08-01

    This work describes, using mainly transmission electron microscopy as an investigation tool, the nature and behaviour of the crystalline defects which are present in (11-22) semipolar GaN films grown epitaxially on patterned r-sapphire substrates using a 3 step growth process. The microstructure at these different growth stages is described. The independent 3D-crystallites nucleated on the substrate surface contain threading dislocations resulting from the epitaxy on c-sapphire facets and basal stacking faults (BSFs), mainly in the  -c-wings. These defects are concentrated in a few hundred nanometre wide stripe-like regions emerging on the top facet of the islands. By a careful choice of the growth conditions, these defective regions may be overgrown by defect-free material, blocking their propagation towards the coalesced surface. However, when the 3D crystals coalesce, new dislocations together with very few BSFs are created at the coalescence boundaries. These coalescence defects propagate to the surface of the films in (0001) planes. In summary, the control of the nucleation and propagation of the crystalline defects allows obtaining large area semipolar films with very low defect densities: 7   ×   107 cm-2 for TDs and 70 cm-1 for BSFs.

  12. Development and Industrialization of InGaN/GaN LEDs on Patterned Sapphire Substrates for Low Cost Emitter Architecture

    Energy Technology Data Exchange (ETDEWEB)

    Flemish, Joseph [Lumileds LLC., San Jose, CA (United States); Soer, Wouter [Lumileds LLC., San Jose, CA (United States)

    2015-11-30

    Patterned sapphire substrate (PSS) technology has proven to be an effective approach to improve efficacy and reduce cost of light-emitting diodes (LEDs). The volume emission from the transparent substrate leads to high package efficiency, while the simple and robust architecture of PSS-based LEDs enables low cost. PSS substrates have gained wide use in mid-power LEDs over the past years. In this project, Lumileds has developed and industrialized PSS and epitaxy technology for high- power flip-chip LEDs to bring these benefits to a broader range of applications and accelerate the adoption of energy-efficient solid-state lighting (SSL). PSS geometries were designed for highly efficient light extraction in a flip-chip architecture and high-volume manufacturability, and corresponding sapphire patterning and epitaxy manufacturing processes were integrally developed. Concurrently, device and package architectures were developed to take advantage of the PSS flip-chip die in different types of products that meet application needs. The developed PSS and epitaxy technology has been fully implemented in manufacturing at Lumileds’ San Jose, CA location, and incorporated in illumination-grade LED products that have been successfully introduced to the market, including LUXEON Q and LUXEON FlipChip White.

  13. ON-LINE SELF-CALIBRATING SINGLE CRYSTAL SAPPHIRE OPTICAL SENSOR INSTRUMENTATION FOR ACCURATE AND RELIABLE COAL GASIFIER TEMPERATURE MEASUREMENT

    Energy Technology Data Exchange (ETDEWEB)

    Kristie Cooper; Gary Pickrell; Anbo Wang; Zhengyu Huang; Yizheng Zhu

    2005-04-01

    This report summarizes technical progress October 2004-March 2005 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the BPDI sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Due to the difficulties described on the last report, field testing of the BPDI system has not continued to date. However, we have developed an alternative high temperature sensing solution, which is described in this report.

  14. Structural, optical and electrical study of undoped GaN layers obtained by metalorganic chemical vapor deposition on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Kuoppa, Victor-Tapio, E-mail: tapio.rangel@gmail.co [Institute of Semiconductor and Solid State Physics, Johannes Kepler Universitaet, A-4040 Linz (Austria); Aguilar, Cesia Guarneros [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico); Sanchez-Resendiz, Victor, E-mail: victors@sees.cinvestav.m [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico)

    2011-01-31

    We investigate optical, structural and electrical properties of undoped GaN grown on sapphire. The layers were prepared in a horizontal reactor by low pressure metal organic chemical vapor deposition at temperatures of 900 {sup o}C and 950 {sup o}C on a low temperature grown (520 {sup o}C) GaN buffer layer on (0001) sapphire substrate. The growth pressure was kept at 10,132 Pa. The photoluminescence study of such layers revealed a band-to-band emission around 366 nm and a yellow band around 550 nm. The yellow band intensity decreases with increasing deposition temperature. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies show the formation of hexagonal GaN layers with a thickness of around 1 {mu}m. The electrical study was performed using temperature dependent Hall measurements between 35 and 373 K. Two activation energies are obtained from the temperature dependent conductivity, one smaller than 1 meV and the other one around 20 meV. For the samples grown at 900 {sup o}C the mobilities are constant around 10 and 20 cm{sup 2} V{sup -1} s{sup -1}, while for the sample grown at 950 {sup o}C the mobility shows a thermally activated behavior with an activation energy of 2.15 meV.

  15. Interface structure of GaN on sapphire (0 0 0 1) studied by transmission electron microscope

    Science.gov (United States)

    Onitsuka, Tsuyoshi; Maruyama, Takahiro; Akimoto, Katsuhiro; Bando, Yoshio

    1998-06-01

    Structural defects of GaN grown by plasma-assisted molecular beam epitaxy on sapphire (0 0 0 1) substrates have been studied by transmission electron microscope (TEM). Cubic GaN (c-GaN) islands, surrounded by hexagonal GaN (h-GaN), with the typical height and width of 6 and 50 nm, respectively, were observed in the vicinity of the substrate by selected area diffraction pattern and high-resolution image. The epitaxial relationship between c-GaN and h-GaN was determined as h-GaN (0 0 0 1)‖c-GaN (1 1 1), h-GaN(1 0-1 1)‖c-GaN (1 0 0) and h-GaN[1 1-2 0]‖c-GaN [1 1 0]. Because the boundary between c-GaN and h-GaN has high density of dislocations, the mixed cubic-hexagonal character near the substrate may play an important role in the relaxation of large misfit stress created by lattice mismatching between GaN and sapphire substrate.

  16. Low temperature sapphire nitridation: A clue to optimize GaN layers grown by molecular beam epitaxy

    Science.gov (United States)

    Widmann, F.; Feuillet, G.; Daudin, B.; Rouvière, J. L.

    1999-02-01

    The sapphire nitridation temperature is investigated as a possible parameter to improve the properties of GaN epilayers grown by molecular beam epitaxy using a radio frequency plasma source. It is found out that lowering the nitridation temperature to values as low as 200 °C allows us to drastically improve the GaN structural and optical properties. Careful examination of the interface by transmission electron microscopy reveals that, in this case, the interface between the nitridated sapphire and the AlN buffer consists of an ordered array of pure edge dislocations. In contrast, high nitridation temperatures result in a perturbed interface with the occurrence of cubic crystallites in the AlN buffer. These results, complemented by a thorough reflection high-energy electron diffraction analysis of the nitridation procedure and a secondary ion mass spectrometry investigation, are interpreted in the framework of a model whereby a higher oxygen concentration is extracted from the substrate at high nitridation temperature, leading to the formation of cubic grains with a smaller lattice parameter than the surrounding matrix and to the concomitant occurrence of defects within the buffer.

  17. Demonstration of frequency control and CW diode laser injection control of a titanium-doped sapphire ring laser with no internal optical elements

    Science.gov (United States)

    Bair, Clayton H.; Brockman, Philip; Hess, Robert V.; Modlin, Edward A.

    1988-01-01

    Theoretical and experimental frequency narrowing studies of a Ti:sapphire ring laser with no intracavity optical elements are reported. Frequency narrowing has been achieved using a birefringent filter between a partially reflecting reverse wave suppressor mirror and the ring cavity output mirror. Results of CW diode laser injection seeding are reported.

  18. Influence of the nucleation layer morphology and epilayer structure on the resistivity of GaN films grown on c-plane sapphire by MOCVD

    NARCIS (Netherlands)

    Grzegorczyk, A.P.; Macht, L.J.; Hageman, P.R.; Weyher, J.L.; Larsen, P.K.

    2005-01-01

    The influence of hydrogen and nitrogen carrier gases used during the preparation of the nucleation layer on the structural and electrical properties of GaN layers has been investigated. The GaN were grown on sapphire substrates using metal organic chemical vapor deposition. The nucleation layer

  19. Mechanical loss of a multilayer tantala/silica coating on a sapphire disk at cryogenic temperatures: Toward the KAGRA gravitational wave detector

    Science.gov (United States)

    Hirose, Eiichi; Craig, Kieran; Ishitsuka, Hideki; Martin, Iain W.; Mio, Norikatsu; Moriwaki, Shigenori; Murray, Peter G.; Ohashi, Masatake; Rowan, Sheila; Sakakibara, Yusuke; Suzuki, Toshikazu; Waseda, Kouichi; Watanabe, Kyohei; Yamamoto, Kazuhiro

    2014-11-01

    We report the results of a new experimental setup to measure the mechanical loss of coating layers on a thin sapphire disk at cryogenic temperatures. Some of the authors previously reported that there was no temperature dependence of the mechanical loss from a multilayer tantala/silica coating on a sapphire disk, both before and after heat treatment, although some reports indicate that Ta2O5 and SiO2 layers annealed at 600 °C have loss peaks near 20 K. Since KAGRA—the Japanese gravitational-wave detector, currently under construction—will be operated at 20 K and have coated sapphire mirrors, it is very important to clarify the mechanical loss behavior of tantala/silica coatings around this temperature. We carefully investigate a tantala/silica-coated sapphire disk with the new setup, anneal the disk, and then investigate the annealed disk. We find that there is no distinct loss peak both before and after annealing under particular conditions. The mechanical loss for the unannealed disk at 20 K is about 5 ×10-4 , as previously reported, while that for the annealed disk is approximately 6.4 ×10-4 .

  20. A comparative structure and morphology study of Zn (1- x ) Cd x O solid solution grown on ZnO and different sapphire orientations

    Science.gov (United States)

    Fouzri, A.; Sallet, V.; Oumezzine, M.

    2011-09-01

    Zn (1- x) Cd xO solid solutions with a constant Cadmium flow 10 cc have been grown on ZnO, c-, a- and r-plane sapphire substrates using metal organic chemical vapor deposition (MO-CVD). The optical transmission spectra and energy band-gap equation established by Mikano et al. were used to estimate cadmium mole fraction of alloy. Lattice parameters and morphology of these films were examined using high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) as Cd incorporation and employed substrate. By comparison, we observe significant differences between Cd incorporation and morphologies depending on nature and substrate orientation but the hexagonal wurtzite structure is maintained. Higher Cd incorporation (11.2 at%) is obtained on Zn (1- x) Cd xO grown on r-plane sapphire, which is confirmed by the greatest energy shift (340 meV) to lower energy measured by room temperature photoluminescence. However, the lattice parameter c remains unchanged while parameter a is identical for films deposited on ZnO and r-plane sapphire substrates and for those deposited on c- and a-plane sapphire substrates.

  1. Structural characterization of thick (11 anti 22) GaN layers grown by HVPE on m-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Usikov, Alexander; Soukhoveev, Vitali; Shapovalov, Lisa; Syrkin, Alexander; Ivantsov, Vladimir; Scanlan, Bernard [Technologies and Devices International, Oxford Instruments Company, 12214 Plum Orchard Dr., Silver Spring, MD 20852 (United States); Nikiforov, Alexey [Department of Electrical and Computer Engineering, Boston University, 8 Saint Mary' s Street, Boston, MA 02215 (United States); Strittmatter, Andre; Johnson, Noble [Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304 (United States); Zheng, Jian-Guo [Materials Characterization Center, LEXI/Calit2, University of California, Irvine, CA 92697 (United States); Spiberg, Philippe; El-Ghoroury, Hussein [Ostendo Technologies, Inc., 6185 Paseo del Norte, Ste. 200, Carlsbad, CA 92011 (United States)

    2010-06-15

    This paper reports structural characterization of thick (11 anti 22)-oriented GaN layers by means of XRD, TEM, and micro- CL. The semi-polar (11 anti 22) GaN layers were grown on m-plane sapphire substrates by HVPE. Their structural quality improved with thickness. Threading dislocation density of 3 x 10{sup 8} cm{sup -2} and stacking faults density of 4 x 10{sup 4} cm{sup -1} were measured at the surface of 20 {mu}m thick (11 anti 22) GaN layers. The semi-polar GaN layers were used as template substrates to grow InGaN/GaN MQW heterostructures by MOCVD that demonstrated optically pumped lasing at 500 nm wavelength. The results demonstrate the longest wavelength yet reported for a photo-pumped laser on template substrates. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  2. Electroluminescence from nonpolar n-ZnO/p-AlGaN heterojunction light-emitting diode on r-sapphire

    Science.gov (United States)

    Chen, Jingwen; Zhang, Jun; Dai, Jiangnan; Wu, Feng; Wang, Shuai; Chen, Cheng; Long, Hanling; Liang, Renli; Zhao, Chong; Chen, Changqing; Tang, Zhiwu; Cheng, Hailing; He, Yunbin; Li, Mingkai

    2017-03-01

    Nonpolar a-plane n-ZnO/p-AlGaN heterojunction light-emitting diodes (LEDs) have been prepared on r-sapphire substrate using metal organic chemical vapor deposition and a pulsed laser deposition method. The dominant electroluminescence emission at 390 nm from the interband transition in n-ZnO layer under a forward bias was observed. Interestingly, electroluminescence with emission at 385 nm based on an avalanche mechanism was also achieved under reverse bias. The mechanisms of both the electroluminescence and I-V characteristics are discussed in detail by considering the avalanche effect. It is demonstrated that the crystalline quality of n-ZnO, not the p-AlGaN, is what affects the performance of the nonpolar ZnO based avalanche LED.

  3. Chip design for thin-film deep ultraviolet LEDs fabricated by laser lift-off of the sapphire substrate

    Science.gov (United States)

    Cho, H. K.; Krüger, O.; Külberg, A.; Rass, J.; Zeimer, U.; Kolbe, T.; Knauer, A.; Einfeldt, S.; Weyers, M.; Kneissl, M.

    2017-12-01

    We report on a chip design which allows the laser lift-off (LLO) of the sapphire substrate sustaining the epitaxial film of flip-chip mounted deep ultraviolet light emitting diodes. A nanosecond pulsed excimer laser with a wavelength of 248 nm was used for the LLO. A mechanically stable chip design was found to be the key to prevent crack formation in the epitaxial layers and material chipping during the LLO process. Stabilization was achieved by introducing a Ti/Au leveling layer that mechanically supports the fragile epitaxial film. The electrical and optical characterization of devices before and after the LLO process shows that the device performance did not degrade by the LLO.

  4. Mode-locking dynamics of a two-color cross-mode-locked femtosecond Ti:sapphire laser

    Energy Technology Data Exchange (ETDEWEB)

    Dykaar, D.R.; Lopez, A.S.; Darack, S.B. [AT and T Bell Labs., Murray Hill, NJ (United States); Knox, W.H. [AT and T Bell Labs., Holmdel, NJ (United States)

    1994-12-31

    The authors demonstrate mode-locked two-wavelength synchronized operation of a single, cw pumped Ti:Sapphire laser. There is no active feedback or external cavity. The measured cross correlation is 105 fs. Wavelengths as much as 57 nm apart can be simultaneously cross-mode-locked. They then investigate the nonlinear interactions between the pulses. They show the nonlinear interaction caused by self focusing scan correct for a difference in cavity lengths of up to {+-}3{micro}m corresponding to 20% of the pulse width on each round trip. Further, they show that the concept of mean group delay can be extended to a pair of pulses with disparate spectra and spatial distribution in a nonlinear regenerative system.

  5. Raman mapping of hexagonal hillocks in N-polar GaN grown on c-plane sapphire

    Science.gov (United States)

    Jiang, Teng; Lin, Zhiyu; Zhang, Jincheng; Xu, Shengrui; Huang, Jun; Niu, Mutong; Gao, Xiaodong; Guo, Lixin; Hao, Yue

    2017-04-01

    A large amount of huge hexagonal hillocks were observed on the surface of N-polar GaN film grown on c-plane sapphire substrate by MOCVD. The distribution of residual stress and dislocation density in a typical hexagonal hillock was investigated by the mapping measurement of Micro-Raman and Cathodoluminescence (CL) spectroscopy. It is found that the residual stress at the top region of the hillock is much smaller than that of the sidewall region and the region around the hillock. Meanwhile, the CL images confirmed that the dislocation density around the hexagonal hillock is higher than the top region of the hillock. The bending and annihilation of the dislocations during the growth of the hexagonal hillock result in the relaxation of residual stress which should be responsible for the spatial variation of dislocation density and residual stress.

  6. High Mobility SiGe/Si n-Type Structures and Field Effect Transistors on Sapphire Substrates

    Science.gov (United States)

    Alterovitz, Samuel A.; Ponchak, George E.; Mueller, Carl H.; Croke, Edward T.

    2004-01-01

    SiGe/Si n-type modulation doped field effect transistors (MODFETs) fabricated on sapphire substrates have been characterized at microwave frequencies for the first time. The highest measured room temperature electron mobility is 1380 sq cm/V-sec at a carrier density of 1.8 x 10(exp 12)/sq cm for a MODFET structure, and 900 sq cm/V-sec at a carrier density of 1.3 x 10/sq cm for a phosphorus ion implanted sample. A two finger, 2 x 200 micron gate n-MODFET has a peak transconductance of 37 mS/mm at a drain to source voltage of 2.5 V and a transducer gain of 6.4 dB at 1 GHz.

  7. On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Kristie Cooper; Gary Pickrell; Anbo Wang

    2005-11-01

    This report summarizes technical progress April-September 2005 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Due to the difficulties described on the last report, field testing of the BPDI system has not continued to date. However, we have developed an alternative high temperature sensing solution, which is described in this report. The sensing system will be installed and tested at TECO's Polk Power Station. Following a site visit in June 2005, our efforts have been focused on preparing for that field test, including he design of the sensor mechanical packaging, sensor electronics, the data transfer module, and the necessary software codes to accommodate this application.. We are currently ready to start sensor fabrication.

  8. Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tingting; Lei, Hong, E-mail: hong_lei2005@aliyun.com

    2017-08-15

    Highlights: • The novel Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives were synthesized by seed-introduced method. • The Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives exhibited lower Ra and higher MRR on sapphire during CMP. • The cores SiO{sub 2} were coated by the shells (SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds. • XPS analysis revealed the solid-state chemical reaction between Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives and sapphire during CMP. - Abstract: Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the silica cores were coated by shells (which contains SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds in the Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives, which made the composite abrasives’ core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives exhibited lower surface roughness and

  9. Direct comparison of optical characteristics of InGaN-based laser diode structures grown on pendeo epitaxial GaN and sapphire substrates

    Science.gov (United States)

    Hwang, J. S.; Gokarna, A.; Cho, Yong-Hoon; Son, J. K.; Lee, S. N.; Sakong, T.; Paek, H. S.; Nam, O. H.; Park, Y.

    2007-03-01

    Direct comparison of optical properties and carrier dynamics of InGaN multiple quantum well (MQW) laser diode structures grown on pendeo epitaxial (PE)-GaN and sapphire substrates is reported. A strong increase in quantum efficiency and a dramatic reduction in stimulated emission threshold are observed for InGaN MQWs on PE-GaN substrates as compared to MQWs on sapphire substrates. Based on temperature-dependent time-resolved optical analysis, the authors find that a significant increase in nonradiative lifetime due to suppressed dislocation density plays an important role in enhancing optical properties of InGaN MQWs grown on PE-GaN substrates, resulting in radiative-process dominant emission even at room temperature.

  10. Development of laser diode-pumped high average power solid-state laser for the pumping of Ti:sapphire CPA system

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, Yoichiro; Tei, Kazuyoku; Kato, Masaaki; Niwa, Yoshito; Harayama, Sayaka; Oba, Masaki; Matoba, Tohru; Arisawa, Takashi; Takuma, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Laser diode pumped all solid state, high repetition frequency (PRF) and high energy Nd:YAG laser using zigzag slab crystals has been developed for the pumping source of Ti:sapphire CPA system. The pumping laser installs two main amplifiers which compose ring type amplifier configuration. The maximum amplification gain of the amplifier system is 140 and the condition of saturated amplification is achieved with this high gain. The average power of fundamental laser radiation is 250 W at the PRF of 200 Hz and the pulse duration is around 20 ns. The average power of second harmonic is 105 W at the PRF of 170 Hz and the pulse duration is about 16 ns. The beam profile of the second harmonic is near top hat and will be suitable for the pumping of Ti:sapphire laser crystal. The wall plug efficiency of the laser is 2.0 %. (author)

  11. Semiconductor saturable-absorber mirror assisted Kerr-lens mode-locked Ti:sapphire laser producing pulses in the two-cycle regime.

    Science.gov (United States)

    Sutter, D H; Steinmeyer, G; Gallmann, L; Matuschek, N; Morier-Genoud, F; Keller, U; Scheuer, V; Angelow, G; Tschudi, T

    1999-05-01

    Pulses of sub-6-fs duration have been obtained from a Kerr-lens mode-locked Ti:sapphire laser at a repetition rate of 100 MHz and an average power of 300 mW. Fitting an ideal sech(2) to the autocorrelation data yields a 4.8-fs pulse duration, whereas reconstruction of the pulse amplitude profile gives 5.8 fs. The pulse spectrum covers wavelengths from above 950 nm to below 630 nm, extending into the yellow beyond the gain bandwidth of Ti:sapphire. This improvement in bandwidth has been made possible by three key ingredients: carefully designed spectral shaping of the output coupling, better suppression of the dispersion oscillation of the double-chirped mirrors, and a novel broadband semiconductor saturable-absorber mirror.

  12. Structural and electronic properties of InN epitaxial layer grown on c-plane sapphire by chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Barick, Barun Kumar, E-mail: bkbarick@gmail.com; Prasad, Nivedita; Saroj, Rajendra Kumar; Dhar, Subhabrata [Department of Physics, Indian Institute of Technology, Bombay, Mumbai 400076 (India)

    2016-09-15

    Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein–Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates.

  13. Fine structures in refractive index of sapphire at the L(II,III) absorption edge of aluminum determined by soft x-ray resonant reflectivity.

    Science.gov (United States)

    Das, Arijeet; Gupta, Rajkumar K; Modi, Mohammed H; Mukherjee, Chandrachur; Rai, Sanjay K; Bose, Aniruddha; Ganguli, Tapas; Joshi, Satish C; Lodha, Gyan S; Deb, Sudip K

    2012-10-20

    The optical constants of sapphire crystal (α-Al(2)O(3)) and amorphous Al(2)O(3) in the soft x-ray region (67-85 eV) around the aluminum LII,III absorption edge (73.1 eV) are determined by angle-dependent x-ray reflectivity. The differences between the optical constant values of both the samples are discussed. The fine structures obtained in the absorption of crystalline sapphire are explained. An absorption feature at 70.2 eV is observed for the first time for crystalline alumina. Both datasets are compared to the tabulated values of Henke et al. [At. Data Nucl. Data Tables 54, 181 (1993)], Weaver et al. [Physik Daten, Physics Data: Optical Properties of Metals (Fach-information zentrum, 1981), Vols. 18-1 and 18-2], and [Handbook of Optical Constants of Solids II (Academic, 1991)].

  14. Growth of ruby and sapphire crystals by the flux method; Crescimento de cristais de rubi e safira pelo metodo do fluxo

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Gislene da Silva [Universidade Federal de Mato Grosso (DRM/UFMT), Cuiaba, MT (Brazil). Dept. de Recuros Minerais; Prado, Rogerio Junqueira, E-mail: rjprado@ufmt.b [Universidade Federal de Mato Grosso (IF/UFMT), Cuiaba, MT (Brazil). Inst. de Fisica

    2010-07-01

    This work reports the growth of corundum crystals by the flux method. The main objective was the evaluation of versatility, effectiveness and real possibilities of the flux method to the synthesis and doping of monocrystals with impurities of particular interest. In this work the chosen impurities were 1) Cr and 2) Fe and Ti, aiming the synthesis of rubies and sapphires, respectively. The crystals were grown by heating a mixture of Al{sub 2}O{sub 3}:Cr or Al{sub 2}O{sub 3}:Fe:Ti and flux (MoO{sub 3}). The maximum crystal size obtained was 1.0 mm, all transparent, presenting well developed faces, bipyramidal hexagonal shape, and showing a typical red (ruby) and/or light blue (sapphire) color. EDX and XPD experiments were performed in order to characterize some of the synthesized crystals. All crystallized specimens presented the a-alumina atomic structure. (author)

  15. Nd3+-doped colloidal SiO2 composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

    Science.gov (United States)

    Liu, Tingting; Lei, Hong

    2017-08-01

    Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd3+-doped colloidal SiO2 composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd3+-doped colloidal SiO2 composite abrasives and the silica cores were coated by shells (which contains SiO2, Nd2Si2O7 and Nd(OH)3) via chemical bonds and hydrogen bonds in the Nd3+-doped colloidal SiO2 composite abrasives, which made the composite abrasives' core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd3+-doped colloidal SiO2 composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd3+-doped colloidal SiO2 composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO2, Nd2Si2O7 and Nd(OH)3) of Nd3+-doped colloidal SiO2 composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd3+-doped colloidal SiO2 composite abrasives exhibited lower surface roughness and higher material removal rate (MRR) than the pure colloidal SiO2 abrasives in the same polishing conditions, which was attributed to the solid-state chemical reactions between shells of Nd3+-doped colloidal SiO2 composite abrasives and sapphire.

  16. Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

    Directory of Open Access Journals (Sweden)

    Keisuke Iwano

    2016-10-01

    Full Text Available We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV to near-infrared (NIR window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H, deuterium (D, and helium (He ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

  17. Inclined angle-controlled growth of GaN nanorods on m-sapphire by metal organic chemical vapor deposition without a catalyst.

    Science.gov (United States)

    Lee, Kyuseung; Chae, Sooryong; Jang, Jongjin; Min, Daehong; Kim, Jaehwan; Eom, Daeyong; Yoo, Yang-Seok; Cho, Yong-Hoon; Nam, Okhyun

    2015-08-21

    In this study, we have intentionally grown novel types of (11-22)- and (1-10-3)-oriented(3) and self-assembled inclined GaN nanorods (NRs) on (10-10) m-sapphire substrates using metal organic chemical vapor deposition without catalysts and ex situ patterning. Nitridation of the m-sapphire surface was observed to be crucial to the inclined angle as well as the growth direction of the GaN NRs. Polarity-selective KOH etching confirmed that both (11-22) and (1-10-3) GaN NRs are nitrogen-polar. Using pole figure measurements and selective area electron diffraction patterns, the epitaxial relationship between the inclined (11-22) and (1-10-3) GaN NRs and m-sapphire substrates was systematically demonstrated. Furthermore, it was verified that the GaN NRs were single-crystalline wurtzite structures. We observed that stacking fault-related defects were generated during the initial growth stage using high-resolution transmission electron microscopy. The blue-shift of the near band edge (NBE) peak in the inclined angle-controlled GaN NRs can be explained by a band filling effect through carrier saturation of the conduction band, resulting from a high Si-doping concentration; in addition, the decay time of NBE emission in (11-22)- and (1-10-3)-oriented NRs was much shorter than that of stacking fault-related emission. These results suggest that defect-free inclined GaN NRs can be grown on m-sapphire without ex situ treatment.

  18. Self-assembled growth and structural analysis of inclined GaN nanorods on nanoimprinted m-sapphire using catalyst-free metal-organic chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Kyuseung Lee

    2016-04-01

    Full Text Available In this study, self-assembled inclined (1-10-3-oriented GaN nanorods (NRs were grown on nanoimprinted (10-10 m-sapphire substrates using catalyst-free metal-organic chemical vapor deposition. According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ∼57.5° to the [10-10]sapp direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]sapp. Uni-directionally inclined NRs were formed through the one-sided (10-11-faceted growth of the interfacial a-GaN plane layer. It was confirmed that a thin layer of a-GaN was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation. The interfacial a-GaN nucleation affected both the inclined angle and the growth direction of the inclined GaN NRs. Using X-ray diffraction and selective area electron diffraction, the epitaxial relationship between the inclined (1-10-3 GaN NRs and interfacial a-GaN layer on m-sapphire substrates was systematically investigated. Moreover, the inclined GaN NRs were observed to be mostly free of stacking fault-related defects using high-resolution transmission electron microscopy.

  19. A comparative study of efficiency droop and internal electric field for InGaN blue lighting-emitting diodes on silicon and sapphire substrates

    Science.gov (United States)

    Ryu, H. Y.; Jeon, K. S.; Kang, M. G.; Yuh, H. K.; Choi, Y. H.; Lee, J. S.

    2017-04-01

    We investigated the efficiency droop and polarization-induced internal electric field of InGaN blue light-emitting diodes (LEDs) grown on silicon(111) and c-plane sapphire substrates. The efficiency droop of the LED sample grown on silicon substrates was considerably lower than that of the identically fabricated LED sample grown on sapphire substrates. Consequently, the LED on silicon showed higher efficiency at a sufficiently high injection current despite the lower peak efficiency caused by the poorer crystal quality. The reduced efficiency droop for the LED on silicon was attributed to its lower internal electric field, which was confirmed by reverse-bias electro-reflectance measurements and numerical simulations. The internal electric field of the multiple quantum wells (MQWs) on silicon was found to be reduced by more than 40% compared to that of the MQWs on sapphire, which resulted in a more homogenous carrier distribution in InGaN MQWs, lower Auger recombination rates, and consequently reduced efficiency droop for the LEDs grown on the silicon substrates. Owing to its greatly reduced efficiency droop, the InGaN blue LED on silicon substrates is expected to be a good cost effective solution for future lighting technology.

  20. Optogenetic activation of neocortical neurons in vivo with a sapphire-based micro-scale LED probe

    Directory of Open Access Journals (Sweden)

    Niall eMcAlinden

    2015-05-01

    Full Text Available Optogenetics has proven to be a revolutionary technology in neuroscience and has advanced continuously over the past decade. However, optical stimulation technologies for in vivo need to be developed to match the advances in genetics and biochemistry that have driven this field. In particular, conventional approaches for in vivo optical illumination have a limitation on the achievable spatio-temporal resolution. Here we utilize a sapphire-based microscale gallium nitride light-emitting diode (µLED probe to activate neocortical neurons in vivo. The probes were designed to contain independently controllable multiple µLEDs, emitting at 450 nm wavelength with an irradiance of up to 2 W/mm2. Monte-Carlo stimulations predicted that optical stimulation using a µLED can modulate neural activity within a localized region. To validate this prediction, we tested this probe in the mouse neocortex that expressed channelrhodopsin-2 (ChR2 and compared the results with optical stimulation through a fiber at the cortical surface. We confirmed that both approaches reliably induced action potentials in cortical neurons and that the µLED probe evoked strong responses in deep neurons. Due to the possibility to integrate many optical stimulation sites onto a single shank, the µLED probe is thus a promising approach to control neurons locally in vivo.

  1. Channel Temperature Determination for AlGaN/GaN HEMTs on SiC and Sapphire

    Science.gov (United States)

    Freeman, Jon C.; Mueller, Wolfgang

    2008-01-01

    Numerical simulation results (with emphasis on channel temperature) for a single gate AlGaN/GaN High Electron Mobility Transistor (HEMT) with either a sapphire or SiC substrate are presented. The static I-V characteristics, with concomitant channel temperatures (T(sub ch)) are calculated using the software package ATLAS, from Silvaco, Inc. An in-depth study of analytical (and previous numerical) methods for the determination of T(sub ch) in both single and multiple gate devices is also included. We develop a method for calculating T(sub ch) for the single gate device with the temperature dependence of the thermal conductivity of all material layers included. We also present a new method for determining the temperature on each gate in a multi-gate array. These models are compared with experimental results, and show good agreement. We demonstrate that one may obtain the channel temperature within an accuracy of +/-10 C in some cases. Comparisons between different approaches are given to show the limits, sensitivities, and needed approximations, for reasonable agreement with measurements.

  2. Development of Auto-Seeding System Using Image Processing Technology in the Sapphire Crystal Growth Process via the Kyropoulos Method

    Directory of Open Access Journals (Sweden)

    Churl Min Kim

    2017-04-01

    Full Text Available The Kyropoulos (Ky and Czochralski (Cz methods of crystal growth are used for large-diameter single crystals. The seeding process in these methods must induce initial crystallization by initiating contact between the seed crystals and the surface of the melted material. In the Ky and Cz methods, the seeding process lays the foundation for ingot growth during the entire growth process. When any defect occurs in this process, it is likely to spread to the entire ingot. In this paper, a vision system was constructed for auto seeding and for observing the surface of the melt in the Ky method. An algorithm was developed to detect the time when the internal convection of the melt is stabilized by observing the shape of the spoke pattern on the melt material surface. Then, the vision system and algorithm were applied to the growth furnace, and the possibility of process automation was examined for sapphire growth. To confirm that the convection of the melt was stabilized, the position of the island (i.e., the center of a spoke pattern was detected using the vision system and image processing. When the observed coordinates for the center of the island were compared with the coordinates detected from the image processing algorithm, there was an average error of 1.87 mm (based on an image with 1024 × 768 pixels.

  3. Effect of power history on the shape and the thermal stress of a large sapphire crystal during the Kyropoulos process

    Science.gov (United States)

    Nguyen, Tran Phu; Chuang, Hsiao-Tsun; Chen, Jyh-Chen; Hu, Chieh

    2018-02-01

    In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

  4. Indentation-Induced Mechanical Deformation Behaviors of AlN Thin Films Deposited on c-Plane Sapphire

    Directory of Open Access Journals (Sweden)

    Sheng-Rui Jian

    2012-01-01

    Full Text Available The mechanical properties and deformation behaviors of AlN thin films deposited on c-plane sapphire substrates by helicon sputtering method were determined using the Berkovich nanoindentation and cross-sectional transmission electron microscopy (XTEM. The load-displacement curves show the “pop-ins” phenomena during nanoindentation loading, indicative of the formation of slip bands caused by the propagation of dislocations. No evidence of nanoindentation-induced phase transformation or cracking patterns was observed up to the maximum load of 80 mN, from either XTEM or atomic force microscopy (AFM of the mechanically deformed regions. Instead, XTEM revealed that the primary deformation mechanism in AlN thin films is via propagation of dislocations on both basal and pyramidal planes. Furthermore, the hardness and Young’s modulus of AlN thin films estimated using the continuous contact stiffness measurements (CSMs mode provided with the nanoindenter are 16.2 GPa and 243.5 GPa, respectively.

  5. Growth mechanism and electronic properties of epitaxial In{sub 2}O{sub 3} films on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ch. Y.; Kirste, L.; Roehlig, C. C.; Koehler, K.; Cimalla, V.; Ambacher, O. [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany); Morales, F. M.; Manuel, J. M.; Garcia, R. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Puerto Real, Cadiz 11510 (Spain)

    2011-11-01

    In this work, we report on the epitaxial growth of high-quality cubic indium oxide thick films on c-plane sapphire substrates using a two-step growth process. The epitaxial relationship of In{sub 2}O{sub 3} on (0001) Al{sub 2}O{sub 3} has been investigated. The (222) plane spacing and lattice parameter of a most strain-relaxed high-quality In{sub 2}O{sub 3} film have been determined to be 292.58 pm and 1013.53 pm, respectively. The electronic properties in dependence of the film thickness are interpreted using a three-region model. The density at the surface and interface totals (3.3{+-}1.5)x10{sup 13}cm{sup -2}, while the background electron density in the bulk was determined to be (2.4{+-}0.5)x10{sup 18}cm{sup -3}. Furthermore, post treatments such as irradiation via ultraviolet light and ozone oxidation have been found to influence only the surface layer, while the bulk electronic properties remain unchanged.

  6. Investigation of diamond wheel topography in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire using fractal analysis method.

    Science.gov (United States)

    Wang, Qiuyan; Zhao, Wenxiang; Liang, Zhiqiang; Wang, Xibin; Zhou, Tianfeng; Wu, Yongbo; Jiao, Li

    2018-03-01

    The wear behaviors of grinding wheel have significant influence on the work-surface topography. However, a comprehensive and quantitative method is lacking for evaluating the wear conditions of grinding wheel. In this paper, a fractal analysis method is used to investigate the wear behavior of resin-bonded diamond wheel in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire, and a series of experiments on EUAG and conventional grinding (CG) are performed. The results show that the fractal dimension of grinding wheel topography is highly correlated to the wear behavior, i.e., grain fracture, grain pullout, and wheel loading. An increase in cutting edge density on the wheel surface results in an increase of the fractal dimension, but an increase in the grain pullout and wheel loading results in a decrease in the fractal dimension. The wheel topography in EUAG has a higher fractal dimension than that in CG before 60 passes due to better self-sharpening behavior, and then has a smaller fractal dimension because of more serious wheel loadings after 60 passes. By angle-dependent distribution analysis of profile fractal dimensions, the wheel surface topography is transformed from isotropic to anisotropic. These indicated that the fractal analysis method could be further used in monitoring of a grinding wheel performance in EUAG. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates

    Science.gov (United States)

    Elgammal, Karim; Hugosson, Håkan W.; Smith, Anderson D.; Råsander, Mikael; Bergqvist, Lars; Delin, Anna

    2017-09-01

    We present dispersion-corrected density functional calculations of water and carbon dioxide molecules adsorption on graphene residing on silica and sapphire substrates. The equilibrium positions and bonding distances for the molecules are determined. Water is found to prefer the hollow site in the center of the graphene hexagon, whereas carbon dioxide prefers sites bridging carbon-carbon bonds as well as sites directly on top of carbon atoms. The energy differences between different sites are however minute - typically just a few tenths of a millielectronvolt. Overall, the molecule-graphene bonding distances are found to be in the range 3.1-3.3 Å. The carbon dioxide binding energy to graphene is found to be almost twice that of the water binding energy (around 0.17 eV compared to around 0.09 eV). The present results compare well with previous calculations, where available. Using charge density differences, we also qualitatively illustrate the effect of the different substrates and molecules on the electronic structure of the graphene sheet.

  8. The determining factor of a preferred orientation of GaN domains grown on m-plane sapphire substrates.

    Science.gov (United States)

    Jue, Miyeon; Kim, Cheol-Woon; Kang, Seoung-Hun; Yoon, Hansub; Jang, Dongsoo; Kwon, Young-Kyun; Kim, Chinkyo

    2015-11-09

    Epitaxial lateral overgrowth in tandem with the first-principles calculation was employed to investigate the determining factor of a preferred orientation of GaN on SiO2-patterned m-plane sapphire substrates. We found that the (1100)-orientation is favored over the (1103)-orientation in the region with a small filling factor of SiO2, while the latter orientation becomes preferred in the region with a large filling factor. This result suggests that the effective concentration determines the preferred orientation of GaN: the (1100)- and (1103)-orientations preferred at their low and high concentrations, respectively. Our computational study revealed that at a low coverage of Ga and N atoms, the local atomic arrangement resembles that on the (1103) surface, although the (1100) surface is more stable at their full coverage. Such a (1103)-like atomic configuration crosses over to the local structure resembling that on the (1100) surface as the coverage increases. Based on results, we determined that high effective concentration of Ga and N sources expedites the growth of the (1103)-orientation while keeping from transition to the (1100)-orientation. At low effective concentration, on the other hand, there is a sufficient time for the added Ga and N sources to rearrange the initial (1103)-like orientation to form the (1100)-orientation.

  9. Stabilization and phase control of femtosecond Ti:sapphire laser with a repetition rate of 90MHz

    Science.gov (United States)

    Zhang, Wei; Han, Hainian; Wang, Peng; Wei, Zhiyi

    2007-01-01

    Carrier-enveloped phase controlled femtosecond laser has an important application in the absolute frequency measurement, which lead to a revolutionary progress in the frequency metrology. In this paper we will report a high stable optical frequency comb based on a 90MHz repetition rate Ti:sapphire laser, by using a photonic crystal fiber to broaden octave spanning spectrum and a self-reference technology to measure the offset frequency f ceo, both the repetition rate f rep and f ceo are locked simultaneously to a cesium clock with phase lock loop (PLL) technology. For simultaneous stabilization of f rep and f ceo, two sets of phase-locked loop electronics are introduced to control separately the laser cavity length for f rep with a PZT and the pump laser for f ceo with an acoustic optics modulation (AOM) respectively. As the result, we stabilized the f rep at a fluctuation within the order of μHz, and f ceo is in the order of mHz, which support a frequency comb with an uncertainty of 10 -14.

  10. Generating multiple wavelengths, simultaneously, in a Ti:sapphire ring laser with a ramp-hold-fire seeding technique

    Science.gov (United States)

    Moore, Thomas Z.; Anderson, F. Scott

    2012-03-01

    The ability to simultaneously produce pulsed laser output over multiple discrete wavelengths can mitigate many of the timing and jitter issues associated with the use of multiple laser systems. In addition, Fourier-transform limited laser output on every pulse is required for many applications such as with pump-probe detection, non-linear frequency mixing, differential absorption lidar (DIAL), and resonance ionization. As a matter of practice, such lasers need to be capable of operating within uncontrolled or noisy environments. We report on a novel Ti:sapphire ring laser that has been developed to produce Fourier-transform limited 20-ns laser pulses at multiple discrete wavelengths, simultaneously, utilizing a Ramp-Hold-Fire (RHF) seeding technique. Resonance of the seed light is achieved by using a KD*P crystal to modify the phase of the light circulating within the slave oscillator cavity where the fast response of the crystal results in a seeding technique that is immune to noise throughout the acoustic regime.

  11. Reduction of threading dislocations in ZnO/(0001) sapphire film heterostructure by epitaxial lateral overgrowth of nanorods

    Science.gov (United States)

    Sun, Yuekui; Cherns, David; Doherty, Rachel P.; Warren, James L.; Heard, Peter J.

    2008-07-01

    Transmission electron microscopy was used to study threading dislocations (TDs) in epitaxial ZnO films on (0001) sapphire substrates produced by a two-step method. First, ZnO was deposited by pulsed laser deposition. It was found that the sample consisted of a continuous buffer layer with a high density, 7×1010/cm2, of TDs, with c-aligned nanorods on its top. The nanorods revealed few, if any, TDs. A further layer of ZnO was then grown under conditions favoring nanorod growth, using either chemical vapor deposition (CVD) or a hydrothermal method. In both cases the nanorods grew laterally and eventually coalesced to form a continuous overgrowth. The nanorods remained mostly free of dislocations until coalescence. New grain boundary dislocations were generated where nanorods coalesced, but many of these dislocations migrated laterally and interacted with other dislocations to form closed loops. The TD density at the top of the continuous film was thereby reduced to 1×109/cm2 and 7×109/cm2 in the cases of hydrothermal and CVD treatments, respectively. The mechanism of growth and the means by which TDs are reduced are explained.

  12. Study of surface morphology control and investigation of hexagonal indium nitride nanorods grown on GaN/sapphire substrate.

    Science.gov (United States)

    Kuo, Shou-Yi; Chen, Wei-Chun; Lai, Fang-I; Lin, Woei-Tyng; Wang, Han-Yang; Hsiao, Chien-Nan

    2012-02-01

    Heteroepitaxial growth of metal-catalyst-free indium nitride (InN) nanorods on GaN/sapphire substrates by radio-frequency metal-organic molecular beam epitaxy (RF-MOMBE) system was investigated. We found that different N/In flow ratios together with the growth temperatures greatly influenced the surface morphology of InN nanorods and their structural properties. The InN nanorods have been characterized in detail using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM). Optical property was evaluated by photoluminescence (PL) measurements. At lower growth temperatures, InN nanorods were successfully grown. A pronounced two-dimensional growth mode was observed at higher growth temperature of 500 degrees C, and these films showed preferred orientation along the c-axis. XRD patterns and SEM images reveal that InN nanorods has high quality wurtzite structure with FWHM approaching 900 arcsec, and they have uniform diameters of about 150 nm and length of about 800 nm. Meanwhile, no metallic droplet was observed at the end of the nanostructured InN, and this is strong evidence that the nanorods are grown via the self-catalyst process. The PL peak at 0.8 eV is attributed to the quantum confinement and Moss-Burstein effects. These observations provide some valuable insights into the physical-chemical process for manufacturing InN nanorods devices.

  13. Microstructure of GaN epitaxial films at different stages of the growth process on sapphire (0 0 0 1)

    Science.gov (United States)

    Vennegues, P.; Beaumont, B.; Vaille, M.; Gibart, P.

    1997-04-01

    The microstructure of GaN films at different stages of a classical two steps growth process is studied using TEM. The buffer layer grown at low temperature (600°C) exhibits a mixed cubic-hexagonal columnar microstructure. Numerous defects are present to accomodate the misorientations between micrograins. During the following annealing step up to 1050°C, the microstructure drastically changes: cubic islands remain on the top of a film with hexagonal structure. The buffer layer at this stage is still highly polycrystalline. The microstructure of micrometer thick films grown at 1050°C could be separated in two zones. Close to the interface with sapphire, misfit dislocations, basal stacking faults and nanocavities are observed. We propose a mechanism of relaxation of the strain due to the difference of thermal expansion coefficients which could explain the presence of stacking faults. The existence of nanocavities is supposed to be related to a contamination by oxygen. After a thickness of 0.5 μm, two types of threading defects remain: edge dislocations with {1}/{3} Burgers vector which accommodate slight misorientations between grains, and nanopipes. These nanopipes are identified as open core dislocations with (0 0 0 1) Burgers vector. They have an alternating behaviour: close core, open core. The microstructure of this bulk zone duplicates the microstructure of the buffer layer at a higher scale, pointing out the crucial importance of the first steps of the growth.

  14. Mechanism of ductile rupture in the Al/sapphire system elucidated using x-ray tomographic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    King, W.E.; Campbell, G.H.; Haupt, D.L.; Kinney, J.H.; Riddle, R.A.; Wien, W.L.

    1995-12-18

    The fracture of a thin metal foil constrained between alumina or sapphire blocks has been studied by a number of investigators. The systems that have been investigated include Al, Au, Nb, and Cu. Except for Al/Al{sub 2}O{sub 3} interfaces, these systems exhibit a common fracture mechanism: pores form at the metal/ceramic interface several foil thicknesses ahead of the crack which, under increasing load, grow and link with the initial crack. This mechanism leaves metal o none side of the fracture surface and clean ceramic on the other. This has not been the observation in Al/Al{sub 2}O{sub 3} bonds where at appropriate thicknesses of Al, the fracture appears to proceed as a ductile rupture through the metal. This paper addresses the question of why the fracture of the Al/Al{sub 2}O{sub 3} system appears to be different from other systems by probing the fracture mechanism using X-ray tomographic microscopy (XTM). The authors have experimentally duplicated the simplified geometry of the micromechanics models and subjected the specimens to a well defined stress state in bending. The bend tests were interrupted and XTM was performed to reveal the mechanism of crack extension.

  15. Few-cycle, broadband, mid-infrared optical parametric oscillator pumped by a 20-fs Ti:sapphire laser

    Science.gov (United States)

    Chaitanya Kumar, Suddapalli; Esteban-Martin, Adolfo; Ideguchi, Takuro; Yan, Ming; Holzner, Simon; Hänsch, Theodor W; Picqué, Nathalie; Ebrahim-Zadeh, Majid

    2014-01-01

    A few-cycle, broadband, singly-resonant optical parametric oscillator (OPO) for the mid-infrared based on MgO-doped periodically-poled LiNbO3 (MgO:PPLN), synchronously pumped by a 20-fs Ti:sapphire laser is reported. By using crystal interaction lengths as short as 250 µm, and careful dispersion management of input pump pulses and the OPO resonator, near-transform-limited, few-cycle idler pulses tunable across the mid-infrared have been generated, with as few as 3.7 optical cycles at 2682 nm. The OPO can be continuously tuned over 2179-3732 nm (4589-2680 cm-1) by cavity delay tuning, providing up to 33 mW of output power at 3723 nm. The idler spectra exhibit stable broadband profiles with bandwidths spanning over 422 nm (FWHM) recorded at 3732 nm. The effect of crystal length on spectral bandwidth and pulse duration is investigated at a fixed wavelength, confirming near-transform-limited idler pulses for all grating interaction lengths. By locking the repetition frequency of the pump laser to a radio-frequency reference, and without active stabilization of the OPO cavity length, an idler power stability better than 1.6% rms over >2.75 hours is obtained when operating at maximum output power, in excellent spatial beam quality with TEM00 mode profile. Photograph shows a multigrating MgO:PPLN crystal used as a nonlinear gain medium in the few-cycle femtosecond mid-IR OPO. The visible light is the result of non-phase-matched sum-frequency mixing between the interacting beams. PMID:25793016

  16. Evaluation of the Beckman Coulter UniCel DxH 800 and Abbott Diagnostics Cell-Dyn Sapphire hematology analyzers on pediatric and neonatal specimens in a tertiary care hospital.

    Science.gov (United States)

    Tan, Brent T; Nava, Armando J; George, Tracy I

    2011-06-01

    We evaluated the new UniCel DxH 800 hematology analyzer (Beckman Coulter, Miami, FL) vs the Cell-Dyn Sapphire (Abbott Diagnostics, Santa Clara, CA) using 156 pediatric specimens in Microtainer tubes (Becton Dickinson, Franklin Lakes, NJ). The CBC and differential showed good interinstrument correlation, including WBCs (r = 0.995), RBCs (r = 0.992), hemoglobin (r = 0.998), mean corpuscular volume (r = 0.988), platelets (r = 0.997), neutrophils (r = 0.988), lymphocytes (r = 0.984), monocytes (r = 0.815), eosinophils (r = 0.840), basophils (r = 0.049), and nucleated RBCs (NRBCs; r = 0.906). In the instrument vs 400-cell manual differential comparison, the DxH 800 and Sapphire showed comparable performance for nearly all parameters except for NRBCs, for which the DxH 800 correlated better (r = 0.989) than the Sapphire (r = 0.906). We also compared clinical efficiency by determining whether flagged specimens showed abnormalities on a peripheral blood smear as defined by International Council for Standardization in Haematology criteria. The efficiency of the DxH 800 was 78.0% vs the Sapphire at 68.1%. Both instruments showed identical sensitivity (91.1%), but the specificity for the DxH 800 (71.9%) was higher than that of the Sapphire (57.3%).

  17. In vitro Evaluation of Effect of Dental Bleaching on the Shear Bond Strength of Sapphire Orthodontics Brackets Bonded with Resin Modified Glass Ionomer Cement

    Directory of Open Access Journals (Sweden)

    Zainab M Kadhom

    2017-11-01

    Full Text Available Aim: This study aimed to assess the effect of various types of bleaching agents on the shear bond strength of sapphire brackets bonded to human maxillary premolar teeth using resin modified glass ionomer cement (RMGIC and to determine the site of bond failure. Materials and Methods: Thirty freshly extracted maxillary human premolars were selected and assigned into three equal groups, ten teeth in each. The first group was the control (unbleached group; the second group comprised teeth bleached with hydrogen peroxide group (HP 37.5% (in-office bleaching while the third group included teeth bleached with carbamide peroxide group (CP 16% (at-home bleaching. The teeth in the experimental groups were bleached and stored in water one day then bonded with sapphire brackets using RMGIC with the control group and left another day. De-bonding was performed using Instron universal testing machine. To determine the site of bond failure, both the enamel surface and bracket base of each tooth were examined under magnifying lens (20X of a stereomicroscope. Results: Results showed statistically highly significant difference in the shear bond strengths between control group and both of bleaching groups being low in the control group. Score III was the predominant site of bond failure in all groups. Conclusions: RMGIC provides adequate bond strength when bonding the sapphire brackets to bleached enamel; this bonding was strong enough to resist both the mechanical and masticatory forces. Most of the adhesive remained on the brackets, so it reduced the time required for removal of the bonding material’s remnants during enamel finishing and polishing.

  18. Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips.

    Science.gov (United States)

    Wastl, Daniel S; Judmann, Michael; Weymouth, Alfred J; Giessibl, Franz J

    2015-01-01

    Characterization and imaging at the atomic scale with atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomically resolved imaging of the calcite (101̅4) surface plane using stiff quartz cantilevers ("qPlus sensors", stiffness k = 1280 N/m) equipped with sapphire tips in ambient conditions without any surface preparation. With 10 atoms in one surface unit cell, calcite has a highly complex surface structure comprising three different chemical elements (Ca, C, and O). We obtain true atomic resolution of calcite in air at relative humidity ranging from 20% to 40%, imaging atomic steps and single atomic defects. We observe a great durability of sapphire tips with their Mohs hardness of 9, only one step below diamond. Depending on the state of the sapphire tip, we resolve either the calcium or the oxygen sublattice. We determine the tip termination by comparing the experimental images with simulations and discuss the possibility of chemical tip identification in air. The main challenges for imaging arise from the presence of water layers, which form on almost all surfaces and have the potential to dissolve the crystal surface. Frequency shift versus distance spectra show the presence of at least three ordered hydration layers. The measured height of the first hydration layer corresponds well to X-ray diffraction data and molecular dynamic simulations, namely, ∼220 pm. For the following hydration layers we measure ∼380 pm for the second and third layer, ending up in a total hydration layer thickness of at least 1 nm. Understanding the influence of water layers and their structure is important for surface segregation, surface reactions including reconstructions, healing of defects, and corrosion.

  19. Influence of vicinal sapphire substrate on the properties of N-polar GaN films grown by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Zhiyu; Zhang, Jincheng, E-mail: jchzhang@xidian.edu.cn; Xu, Shengrui; Chen, Zhibin; Yang, Shuangyong; Tian, Kun; Hao, Yue [Key Lab of Wide Band-Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an, Shaanxi 710071 (China); Su, Xujun [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 (China); Shi, Xuefang [School of Advanced Materials and Nanotechnology, Xidian University, Xi' an, Shaanxi 710071 (China)

    2014-08-25

    The influence of vicinal sapphire substrates on the growth of N-polar GaN films by metal-organic chemical vapor deposition is investigated. Smooth GaN films without hexagonal surface feature are obtained on vicinal substrate. Transmission electron microscope results reveal that basal-plane stacking faults are formed in GaN on vicinal substrate, leading to a reduction in threading dislocation density. Furthermore, it has been found that there is a weaker yellow luminescence in GaN on vicinal substrate than that on (0001) substrate, which might be explained by the different trends of the carbon impurity incorporation.

  20. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    OpenAIRE

    Yu-An Chen; Cheng-Huang Kuo; Li-Chuan Chang; Ji-Pu Wu

    2014-01-01

    GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2) and (1 0 2) peaks decreased from 485 ar...

  1. High electron mobility and low carrier concentration of hydrothermally grown ZnO thin films on seeded a-plane sapphire at low temperature

    OpenAIRE

    Jayah, Nurul Azzyaty; Yahaya, Hafizal; Mahmood, Mohamad Rusop; TERASAKO, Tomoaki; YASUI, KANJI; Hashim, Abdul Manaf

    2015-01-01

    Hydrothermal zinc oxide (ZnO) thick films were successfully grown on the chemical vapor deposition (CVD)-grown thick ZnO seed layers on a-plane sapphire substrates using the aqueous solution of zinc nitrate dehydrate (Zn(NO3)2). The use of the CVD ZnO seed layers with the flat surfaces seems to be a key technique for obtaining thick films instead of vertically aligned nanostructures as reported in many literatures. All the hydrothermal ZnO layers showed the large grains with hexagonal end fac...

  2. A visualization of threading dislocations formation and dynamics in mosaic growth of GaN-based light emitting diode epitaxial layers on (0001) sapphire

    Science.gov (United States)

    Ravadgar, P.; Horng, R. H.; Ou, S. L.

    2012-12-01

    A clear visualization of the origin and characteristics of threading dislocations (TDs) of GaN-based light emitting diode epitaxial layers on (0001) sapphire substrates have been carried out. Special experimental set up and chemical etchant along with field emission scanning electron microscopy are employed to study the dynamics of GaN TDs at different growth stages. Cross-sectional transmission electron microscopy analysis visualized the formation of edge TDs is arising from extension of coalescences at boundaries of different tilting-twining nucleation grains "mosaic growth." Etch pits as representatives of edge TDs are in agreement with previous theoretical models and analyses of TDs core position and characteristics.

  3. 100 mW of blue light at 405 nm from intracavity doubling of CW Ti:Sapphire laser utilising BiBO-crystal

    DEFF Research Database (Denmark)

    Thorhauge, Morten; Mortensen, Jesper Liltorp; Tidemand-Lichtenberg, Peter

    2006-01-01

    100 mW of coherent blue light with a wavelength of 405 nm was generated utilising a BiB3O6 (BiBO) nonlinear crystal to frequency double a Ti:Sapphire laser. Phase match curves as well as sensitivity to angular misalignment was calculated. The BiBO crystal was found to be excellent...... for this application. Temperature dependance was uncritical for this crystal, while power stability was good. The pump-to-blue optical conversion efficiency was approximately 2%. Unfortunately catastrophic coating damage was observed...

  4. SnO2 epitaxial films with varying thickness on c-sapphire: Structure evolution and optical band gap modulation

    Science.gov (United States)

    Zhang, Mi; Xu, Maji; Li, Mingkai; Zhang, Qingfeng; Lu, Yinmei; Chen, Jingwen; Li, Ming; Dai, Jiangnan; Chen, Changqing; He, Yunbin

    2017-11-01

    A series of a-plane SnO2 films with thickness between 2.5 nm and 1436 nm were grown epitaxially on c-sapphire by pulsed laser deposition (PLD), to allow a detailed probe into the structure evolution and optical band gap modulation of SnO2 with growing thickness. All films exhibit excellent out-of-plane ordering (lowest (200) rocking-curve half width ∼0.01°) with an orientation of SnO2(100) || Al2O3(0001), while three equivalent domains that are rotated by 120° with one another coexist in-plane with SnO2[010] || Al2O3 [11-20]. Initially the SnO2(100) film assumes a two-dimensional (2D) layer-by-layer growth mode with atomically smooth surface (minimum root-mean-square roughness of 0.183 nm), and endures compressive strain along both c and a axes as well as mild tensile strain along the b-axis. With increasing thickness, transition from the 2D to 3D island growth mode takes place, leading to formation of various defects to allow relief of the stress and thus relaxation of the film towards bulk SnO2. More interestingly, with increasing thickness from nm to μm, the SnO2 films present a non-monotonic V-shaped variation in the optical band gap energy. While the band gap of SnO2 films thinner than 6.1 nm increases rapidly with decreasing film thickness due to the quantum size effect, the band gap of thicker SnO2 films broadens almost linearly with increasing film thickness up to 374 nm, as a result of the strain effect. The present work sheds light on future design of SnO2 films with desired band gap for particular applications by thickness control and strain engineering.

  5. The search for a molecule to measure an autocorrelation trace of the second/third harmonic emission of a Ti:sapphire laser based on two-photon resonant excitation and subsequent one-photon ionization

    Science.gov (United States)

    Imasaka, Tomoko; Okuno, Tomoya; Imasaka, Totaro

    2013-12-01

    The temporal profile of the second and third harmonic emissions of a Ti:sapphire laser was measured using an autocorrelator consisting of a mass spectrometer as a two-photon-response detector. A number of organic compounds that are potentially applicable for two-photon excitation and subsequent one-photon ionization were investigated using density functional theory calculations. N, N'-dimethylaniline and acetonitrile were used for the measurement of the pulse width for the second and third harmonic emissions of the Ti:sapphire laser. This approach has the potential for use in measuring pulse widths as short as 1-3 fs in the ultraviolet region.

  6. High efficiency angular non-critical phase matching for Ti:sapphire laser realized on LaCa4O(BO3)3 single crystals

    Science.gov (United States)

    Liu, Y. Q.; Yu, F. P.; Qi, H. W.; Han, S.; Zhang, F.; Wang, Z. P.; Yu, X. Q.; Zhao, X.; Xu, X. G.

    2014-09-01

    Angular non-critical phase-matching (A-NCPM) second harmonic generation (SHG) for a Ti:sapphire laser was realized on LaCa4O(BO3)3 (LaCOB) single crystals, grown by the Czochralski pulling method. Properties including the wavelength, bandwidth, effective nonlinear optical (NLO) coefficient (deff), and acceptance angle were evaluated. At ambient temperature of 20 °C, the type-I NCPM (808 nm wavelength) was obtained along the y axis of LaCOB crystals, where the effective nonlinear optical coefficient (deff), PM waveband, and angular acceptance were found to be of the order of 0.59 pm/V, 803~818 nm and 50.6 mrad cm1/2 (ΔϕL), respectively. Moreover, high single-pass SHG conversion efficiency (44.6%) was achieved for 24.8 mm long Y-cut samples at 808 nm, using a mode-locked Ti:sapphire fundamental laser.

  7. Analysis of the AlGaN/GaN vertical bulk current on Si, sapphire, and free-standing GaN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Tomas, A.; Fontsere, A.; Llobet, J. [IMB-CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, CAT (Spain); Placidi, M. [IREC, Jardins Dones de Negre 1, 08930 Sant Adria de Besos, Barcelona (Spain); Rennesson, S.; Chenot, S.; Moreno, J. C.; Cordier, Y. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Baron, N. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); PICOGIGA International, Pl M. Rebuffat, Courtaboeuf 7, 91140 Villejust (France)

    2013-05-07

    The vertical bulk (drain-bulk) current (I{sub db}) properties of analogous AlGaN/GaN hetero-structures molecular beam epitaxially grown on silicon, sapphire, and free-standing GaN (FS-GaN) have been evaluated in this paper. The experimental I{sub db} (25-300 Degree-Sign C) have been well reproduced with physical models based on a combination of Poole-Frenkel (trap assisted) and hopping (resistive) conduction mechanisms. The thermal activation energies (E{sub a}), the (soft or destructive) vertical breakdown voltage (V{sub B}), and the effect of inverting the drain-bulk polarity have also been comparatively investigated. GaN-on-FS-GaN appears to adhere to the resistive mechanism (E{sub a} = 0.35 eV at T = 25-300 Degree-Sign C; V{sub B} = 840 V), GaN-on-sapphire follows the trap assisted mechanism (E{sub a} = 2.5 eV at T > 265 Degree-Sign C; V{sub B} > 1100 V), and the GaN-on-Si is well reproduced with a combination of the two mechanisms (E{sub a} = 0.35 eV at T > 150 Degree-Sign C; V{sub B} = 420 V). Finally, the relationship between the vertical bulk current and the lateral AlGaN/GaN transistor leakage current is explored.

  8. Anisotropic structural and optical properties of semi-polar (11-22) GaN grown on m-plane sapphire using double AlN buffer layers

    Science.gov (United States)

    Zhao, Guijuan; Wang, Lianshan; Yang, Shaoyan; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Wang, Zhanguo

    2016-02-01

    We report the anisotropic structural and optical properties of semi-polar (11-22) GaN grown on m-plane sapphire using a three-step growth method which consisted of a low temperature AlN buffer layer, followed by a high temperature AlN buffer layer and GaN growth. By introducing double AlN buffer layers, we substantially improve the crystal and optical qualities of semi-polar (11-22) GaN, and significantly reduce the density of stacking faults and dislocations. The high resolution x-ray diffraction measurement revealed that the in-plane anisotropic structural characteristics of GaN layer are azimuthal dependent. Transmission electron microscopy analysis showed that the majority of dislocations in the GaN epitaxial layer grown on m-sapphire are the mixed-type and the orientation of GaN layer was rotated 58.4° against the substrate. The room temperature photoluminescence (PL) spectra showed the PL intensity and wavelength have polarization dependence along parallel and perpendicular to the [1-100] axis (polarization degrees ~ 0.63). The realization of a high polarization semi-polar GaN would be useful to achieve III-nitride based lighting emission device for displays and backlighting.

  9. Anisotropic structural and optical properties of semi-polar (11–22) GaN grown on m-plane sapphire using double AlN buffer layers

    Science.gov (United States)

    Zhao, Guijuan; Wang, Lianshan; Yang, Shaoyan; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Wang, Zhanguo

    2016-01-01

    We report the anisotropic structural and optical properties of semi-polar (11–22) GaN grown on m-plane sapphire using a three-step growth method which consisted of a low temperature AlN buffer layer, followed by a high temperature AlN buffer layer and GaN growth. By introducing double AlN buffer layers, we substantially improve the crystal and optical qualities of semi-polar (11–22) GaN, and significantly reduce the density of stacking faults and dislocations. The high resolution x-ray diffraction measurement revealed that the in-plane anisotropic structural characteristics of GaN layer are azimuthal dependent. Transmission electron microscopy analysis showed that the majority of dislocations in the GaN epitaxial layer grown on m-sapphire are the mixed-type and the orientation of GaN layer was rotated 58.4° against the substrate. The room temperature photoluminescence (PL) spectra showed the PL intensity and wavelength have polarization dependence along parallel and perpendicular to the [1–100] axis (polarization degrees ~ 0.63). The realization of a high polarization semi-polar GaN would be useful to achieve III-nitride based lighting emission device for displays and backlighting. PMID:26861595

  10. Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Gillinger, M., E-mail: manuel.gillinger@tuwien.ac.at; Knobloch, T.; Schneider, M.; Schmid, U. [Institute of Sensor and Actuator Systems, TU Wien, 1040 Vienna (Austria); Shaposhnikov, K.; Kaltenbacher, M. [Institute of Mechanics and Mechatronics, TU Wien, 1040 Vienna (Austria)

    2016-06-06

    This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (Sc{sub x}Al{sub 1-x}N) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device properties, samples with thickness ranging from 500 nm up to 3000 nm are fabricated. S{sub 21} measurements and simulations demonstrate that the phase velocity is predominantly influenced by the mass density of the electrode material rather than by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by rotating the interdigital transducer structures with respect to the crystal orientation of the substrate. The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate, which is in excellent agreement with the difference in the anisotropic Young's modulus of the substrate corresponding to these directions.

  11. Performance of InGaN Light-Emitting Diodes Fabricated on Patterned Sapphire Substrates with Modified Top-Tip Cone Shapes

    Directory of Open Access Journals (Sweden)

    Hsu-Hung Hsueh

    2014-01-01

    Full Text Available InGaN light-emitting diodes (LEDs were fabricated on cone-shaped patterned sapphire substrates (PSSs by using low-pressure metalorganic chemical vapor deposition. To enhance the crystal quality of the GaN epilayer and the optoelectronic performance of the LED device, the top-tip cone shapes of the PSSs were further modified using wet etching. Through the wet etching treatment, some dry-etched induced damage on the substrate surface formed in the PSS fabrication process can be removed to achieve a high epilayer quality. In comparison to the LEDs prepared on the conventional sapphire substrate (CSS and cone-shaped PSS without wet etching, the LED grown on the cone-shaped PSS by performing wet etching for 3 min exhibited 55% and 10% improvements in the light output power (at 350 mA, respectively. This implies that the modification of cone-shaped PSSs possesses high potential for LED applications.

  12. Epitactical FeAl films on sapphire and their magnetic properties; Epitaktische FeAl-Filme auf Saphir und ihre magnetischen Eigenschaften

    Energy Technology Data Exchange (ETDEWEB)

    Trautvetter, Moritz

    2011-05-05

    In the presented thesis epitaxial FeAl thin films on sapphire have been prepared by pulse laser deposition (PLD). The thin films deposited at room temperature exhibits ferromagnetism and subsequent annealing is necessary to transform the thin films to paramagnetic B2-phase, where the transition temperature depends on the crystalline orientation of the sapphire substrate. Alternatively, by deposition at higher substrate temperature the B2-phase is obtained directly. However, morphology of the FeAl film is influenced by different growth modes resulting from different substrate temperatures. The paramagnetic FeAl films can then be transformed to ferromagnetic phase by successive ion irradiation. Independent of the ion species used for irradiation, the same universal relation between thin films' coercive fields and irradiation damage is identified. The ion irradiation ferromagnetism can be transformed back to paramagnetism by subsequent annealing. The mutual transition between ferromagnetic and paramagnetic phases has been performed several times and shows full reversibility. The ferromagnetic phase induced by Kr{sup +} irradiation exhibits structural relaxation, where the saturate magnetization of FeAl thin film gradually decreases in several days. Later, ion irradiation has been performed selectively on defined areas of the thin film with the help of an unconventional lithography technique. The subsequent thin film is composed of ordered hexagonal array of ferromagnetic nano-cylinders separated by a paramagnetic matrix, suggesting a promising system for magnetic data storage. (orig.)

  13. Structural and magnetic properties of cobalt-doped ZnO thin films on sapphire (0 0 0 1) substrate deposited by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shanying, E-mail: yshy_150@163.com [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Lv, Rongqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Wang, Changzheng [School of Physics Science and Information Engineering, Liaocheng University, Liaocheng, Shandong Province, 252059 (China); Liu, Yunyan [School of Science, Shandong University of Technology, Zibo, Shandong Province, 255049 (China); Song, Zeqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China)

    2013-12-05

    Highlights: •Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited. •ZnLMM Auger spectrum indicated that Zn interstitials existed in thin films. •The lattice constant increasing was ascribed to the stress and interstitial atoms. •The average moment per Co atom related to the distribution of Co{sup 2+} ions and defects. -- Abstract: Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited by PLD at various substrate temperatures in a one Pa oxygen ambient condition. The structural and magnetic properties of as-grown thin films were characterized by using XRD, UV–Visible absorption spectrophotometer, XPS and AGM. All samples possessed wurtzite hexagonal structure of ZnO. Co atoms incorporated into ZnO matrix and substituted for Zn in ZnO lattice, and Zn interstitials existed in as-grown thin films. The c-axis lattice constants of as-deposited thin films were larger than the standard data. Crystallization of as-prepared thin films increased and then decreased with substrate temperatures enhancing. All samples exhibited room-temperature ferromagnetism. The average moment per Co atom was much smaller than that of Co{sup 2+} (3d{sup 7}), due to the different distribution of Co{sup 2+} ions and defects, as well as the different defect concentrations in thin films.

  14. Comparative analysis of nano-scale structural and electrical properties in AlGaN/GaN high electron mobility transistors on SiC and sapphire substrates.

    Science.gov (United States)

    Wang, Cong; Cho, Sung-Jin; Kim, Nam-Young

    2013-10-01

    A comparison of AIGaN/GaN HEMTs fabricated on both 4-in SiC and sapphire substrates was performed. Due to the high crystalline quality with one order lower dislocation density of GaN on a SiC substrate, a better two-dimensional electron gas (2DEG) mobility with high values of drain current density (780 mA/mm) and a better extrinsic transconductance (240 mS/mm) were observed. We demonstrate GaN-on-SiC HEMTs with a periphery gate width of 200 microm, exhibiting a unity-gain cut-off frequency (f(T)) = 29.6 GHz, a maximum frequency of oscillation (f(MAX)) = 63.2 GHz, and an output power density of 6.4 W/mm with a 55% power added efficiency (PAE) at 10 GHz. A surface roughness of 0.828 nm and 1.025 nm and an X-ray diffraction (XRD) GaN (0002) full-width at half-maximum (FWHM) of 120 s and 919 s were measured for the SiC and sapphire-based AIGaN/GaN HEMTs, respectively. The SiC substrate has been shown to be an optimal solution for fabricating HEMTs for X-band high-power applications, which require excellent performances.

  15. Red cell cytogram in CELL-DYN® Sapphire: a ready-to-use function for recognizing thalassemia trait

    Directory of Open Access Journals (Sweden)

    Eloísa Urrechaga

    2016-04-01

    Full Text Available Single-cell optical analysis of red blood cells provides information on the cellular hemoglobin concentration and volume of red cells. We evaluated the reliability of the typical profiles of the cytogram hemoglobin concentration/ volume (Mie Map, produced by the CELL-DYN® Sapphire analyzer (Abbott Diagnostics, Santa Clara, CA, USA in the discrimination of iron deficiency anemia (IDA and thalassemia trait. A total of 380 patients with microcytic anemia were studied: 220 with IDA, 101 β-thalassemia trait, 30 β-thalassemia trait with concomitant iron deficiency, 29 α-thalassemia trait. Three professionals reviewed the Mie maps, with no information regarding the disease of the patient. The observers made a presumptive diagnosis (genetic or acquired anemia and the percentages of correct classifications were recorded. IDA showed broad shaped shift of the cytogram while carriers presented narrow clustering in the lower microcytic area: 100 % IDA were correctly classified and 96-82% of carriers were recognized. Visual inspection of the Mie map reveals different profiles in IDA and thalassemia trait; those patterns are in concordance with the numerical data Mie map helps in the evaluation of large amounts of data. 红细胞单细胞光学分析提供了关于细胞血红蛋白浓度及红细胞体积的信息。 我们评价了典型的细胞图血红蛋白浓度/体积分布(Mie Map)在缺铁性贫血(IDA)和地中海贫血特征的识别方面的可靠性,分布曲线由CELL-DYN® Sapphire分析仪(Abbott Diagnostics, Santa Clara, CA, USA)生成。 一共对380例小细胞性贫血进行了研究:220例患有IDA,101例β有地中海贫血特征,30例β有地中海贫血特征合并缺铁性,29 α例地中海贫血特征。 由三名专业人员在没有任何患者病情信息的情况下进行Mie map读图。 读图者作出初步诊断(遗传性或获得性贫血),记录正确分类的百分比。 IDA表现出细胞

  16. Epitaxial AlN layers on sapphire and diamond; Epitaktische AlN-Schichten auf Saphir und Diamant

    Energy Technology Data Exchange (ETDEWEB)

    Hermann, Martin

    2009-04-27

    In this work, epitaxial AlN layers deposited by molecular beam epitaxy on sapphire and diamond substrates were investigated. Starting from this AlN, the dopant silicon was added. The influence of the silicon doping on the structural properties of the host AlN crystal was investigated using high resolution X-ray diffraction. Once the silicon concentration exceeds 1 x 10{sup 19} cm{sup -3}, a significant change of the AlN:Si crystal can be observed: increasing the silicon concentration up to 5 x 10{sup 20} cm{sup -3} results in a decrease of the a lattice parameter by approximately 1.2 pm and an increase of the c lattice parameter by about 1.0 pm. The crystal is stressed additionally by adding silicon resulting in a increase of the biaxial compressive stress of up to 2.0 GPa. Further increase of the silicon concentration leads to lattice relaxation. This result from X-ray diffraction was independently confirmed by Raman spectroscopy investigations. Further increase of the silicon concentration leads to the generation of polycrystalline phases within the epitaxial layer. XTEM measurements detected these polycrystalline phases. In addition, XTEM investigations confirmed also the increase of the lateral crystal size with increasing silicon concentration, as well as a great reduction of the screw dislocation density by more than one order of magnitude as found by X-ray diffraction: in undoped, nitrogen rich grown AlN layers the screw dislocation density is about 3 x 10{sup 8} cm{sup -2}, while AlN layers with a silicon concentration of 5 x 10{sup 20} cm{sup -3} show a screw dislocation density of only 1 x 10{sup 7} cm{sup -2}. In low-doped AlN:Si ([Si]{approx}2 x 10{sup 19} cm{sup -3}) the activation energy of the electronic conductivity is about 250 meV. Increasing the silicon concentration to about 1 x 10{sup 21} cm{sup -3} leads to an increase of the activation energy up to more than 500 meV in the now much more stressed AlN:Si epilayer. Studies of the absorption

  17. Effect of the laser sputtering parameters on the orientation of a cerium oxide buffer layer on sapphire and the properties of a YBa2Cu3Ox superconducting film

    DEFF Research Database (Denmark)

    Mozhaev, P. B.; Ovsyannikov, G. A.; Skov, Johannes

    1999-01-01

    The effect of the laser sputtering parameters on the crystal properties of CeO2 buffer layers grown on a (1 (1) under bar 02) sapphire substrate and on the properties of superconducting YBa2Cu3Ox thin films are investigated. It is shown that (100) and (111) CeO2 growth is observed, depending...

  18. Evaluation of the Beckman Coulter UniCel DxH 800, Beckman Coulter LH 780, and Abbott Diagnostics Cell-Dyn Sapphire hematology analyzers on adult specimens in a tertiary care hospital.

    Science.gov (United States)

    Tan, Brent T; Nava, Armando J; George, Tracy I

    2011-06-01

    We evaluated the new Beckman Coulter DxH 800 hematology analyzer (Beckman Coulter, Miami, FL) vs the Abbott Diagnostics Cell-Dyn Sapphire (Abbott Diagnostics, Santa Clara, CA) and Beckman Coulter LH 780 hematology analyzers using 430 adult specimens. The DxH 800 provided a CBC and differential that correlated well with those of the Sapphire and LH 780, with most parameters showing correlation coefficients (r) of more than 0.97. In the instrument vs 400-cell manual differential comparison, all 3 instruments showed similar and acceptable accuracy to the reference method except for nucleated RBC (NRBC) enumeration, in which the DxH 800 and Sapphire outperformed the LH 780. We also compared clinical efficiency by determining whether flagged specimens showed abnormalities on a peripheral blood smear as defined by International Council for Standardization in Haematology criteria. The efficiency, sensitivity, and specificity of the DxH 800 were 77.0%, 87.1%, and 73.0%, respectively, compared with the Sapphire at 75.8%, 93.5%, and 68.8%, respectively, and LH 780 at 66.1%, 93.5%, and 55.3%, respectively.

  19. Comprehensive thermal characterization using ruby R fluorescence lines of sapphire and GaNE{sub 2}-high Raman mode from Raman spectra in high-power flip-chip InGaN/GaN LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Cui, M; Zhou, T F; Wang, M R; Huang, J; Huang, H J; Zhang, J P; Xu, K; Yang, H, E-mail: kxu2006@sinano.ac.cn, E-mail: tfzhou2007@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China)

    2011-09-07

    A comprehensive temperature characterization method based on the GaNE{sub 2}-high Raman mode and sapphire ruby R fluorescence lines from Raman spectra was developed to analyse the thermal distribution and heat transfer process of high-power flip-chip InGaN/GaN LEDs (FC LEDs). Our analysis demonstrated that in addition to the known problem that the edges of mesa were always the hottest point of FC LEDs, which was due to the current crowding effect, a noteworthy temperature difference was first observed between the sapphire substrate and n-GaN when the injection current was above 300 mA. A 'heat reservoir' was suggested to occur at the interface between the sapphire and n-GaN due to poor thermal conductivity of sapphire when a large amount of heat from the hottest spot cannot be effectively transferred to the Si mount via the active region under high injection currents.

  20. The influence of oxygen flow rate on properties of SnO{sub 2} thin films grown epitaxially on c-sapphire by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Y.M. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University (China); Key Laboratory of Green Preparation and Application for Functional Materials, Ministry of Education, Hubei University (China); Faculty of Materials Science & Engineering, Hubei University (China); Jiang, J. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); Xia, C. [Physical Chemistry Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen (Germany); Kramm, B.; Polity, A. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); He, Y.B., E-mail: ybhe@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University (China); Key Laboratory of Green Preparation and Application for Functional Materials, Ministry of Education, Hubei University (China); Faculty of Materials Science & Engineering, Hubei University (China); Klar, P.J.; Meyer, B.K. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany)

    2015-11-02

    Tin dioxide (SnO{sub 2}) thin films were grown on c-plane sapphire substrates by chemical vapor deposition using SnI{sub 2} and O{sub 2} as reactants. The growth experiments were carried out at a fixed substrate temperature of 510 °C and different O{sub 2} flow rates. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–Vis–IR spectrophotometry and Hall-effect measurement were used to characterize the films. All films consisted of pure-phase SnO{sub 2} with a rutile structure and showed an epitaxial relationship with the substrate of SnO{sub 2}(100)||Al{sub 2}O{sub 3}(0001) and SnO{sub 2}[010]||Al{sub 2}O{sub 3}< 11–20 >. The crystalline quality and properties of the films were found to be sensitively dependent on the O{sub 2} flow rate during the film growth. The absolute average transmittance of the SnO{sub 2} films exceeded 85% in the visible and infrared spectral region. The films had optical band-gaps (3.72–3.89 eV) that are in line with the band gap of single-crystal SnO{sub 2}. The carrier concentration and Hall mobility of the films decreased from 3.3 × 10{sup 19} to 9 × 10{sup 17} cm{sup −3} and from 19 to 2 cm{sup 2} V{sup −1} s{sup −1}, respectively, while the resistivity increased from 0.01 to 3 Ω cm with increasing of the O{sub 2} flow rate from 5 to 60 sccm. - Highlights: • SnI{sub 2} (Sn{sup 2+}) was used as tin precursor to prepare tin oxide films by CVD. • Epitaxial SnO{sub 2} (100) films were obtained on c-sapphire with thickness more than 1 μm. • The epitaxial relationship is SnO{sub 2}(100)||Al{sub 2}O{sub 3}(0001) and SnO{sub 2}[010]||Al{sub 2}O{sub 3}< 11–20 >. • B{sub 2g} Raman mode was found to be absent in (100)-orientated SnO{sub 2} films on c-sapphire. • The crystal quality and properties of SnO{sub 2} films depended sensitively on the O{sub 2} flow rate.

  1. Characterization of nonpolar a-plane GaN epi-layers grown on high-density patterned r-plane sapphire substrates

    Science.gov (United States)

    Jinno, Daiki; Otsuki, Shunya; Sugimori, Shogo; Daicho, Hisayoshi; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

    2018-02-01

    To reduce the number of threading dislocations (TDs) in nonpolar a-plane GaN (a-GaN) epi-layers grown on flat r-plane sapphire substrates (r-FSS), we investigated the effects on the crystalline quality of the a-GaN epi-layers of high-density patterned r-plane sapphire substrates (r-HPSS), the patterns of which were placed at intervals of several hundred nanometers. Two types of r-HPSS, the patterns of which had diameters and heights on the order of several hundred nanometers (r-NHPSS) or several micrometers (r-MHPSS), were prepared with conventional r-FSS. The effect of these r-HPSS on the a-GaN epi-layers was demonstrated by evaluating the surface morphology and the crystalline quality of the epi-layers. The surfaces of the a-GaN epi-layer grown on r-FSS and r-NHPSS were pit-free and mirror-like, whereas the surface of the a-GaN epi-layer grown on r-MHPSS was very rough due to the large, irregular GaN islands that grew on the patterns, mainly at the initial growth stage. The crystalline quality of the a-GaN epi-layer grown on r-NHPSS was better than that of the a-GaN epi-layer grown on r-FSS. We confirmed that there were fewer TDs in the a-GaN epi-layer grown on r-NHPSS than there were in the a-GaN epi-layer grown on r-FSS. The TDs propagating to the surface in a-GaN epi-layer grown on r-NHPSS were mainly generated on the flat sapphire regions between the patterns. Interestingly, it was also found that the TDs that propagated to the surface concentrated with a periodic pitch along the c-axis direction. The TD densities of a-GaN epi-layers grown on r-FSS and r-NHPSS were estimated to be approximately 5.0 × 1010 and 1.5 × 109 cm-2, respectively. This knowledge will contribute to the further development of a-GaN epi-layers for high-performance devices.

  2. Compensation of Incomplete Round Trip in an Herriott Multipass-Based Kerr-Lens Mode-Locked Ti:Sapphire Oscillator via an Output Coupler Position

    Science.gov (United States)

    Song, Dong Hoon; In Hwang, Sung; Ko, Do-Kyeong

    2011-03-01

    We examined the soft-aperture Kerr-lens mode-locked femtosecond Ti:sapphire oscillator derived from an Herriott multi-pass cavity (HMPC). Additionally, a novel and simple configuration was provided to extend the cavity length, the HMPC consisting of notched, flat and curved (R = 4 m) mirrors by which beams were injected and extracted. To compensate for beams which failed to complete round trips, the configuration was designed and analyzed as a function of the output coupler position. Such an oscillator generated 21.5 nJ, 34 fs pulses at a repetition rate of approximately 13.5 MHz; the spectral bandwidth represented 20 nm, corresponding to a time-bandwidth product of 0.33, assuming a sech2 fit.

  3. Stress relaxation in thick-film GaN grown by hydride vapor phase epitaxy on sapphire and spinel substrates as studied by photoluminescence and raman spectroscopy

    CERN Document Server

    Kim, S T; Lee, C; Kim, J E; Park, H Y

    1999-01-01

    The residual strains in thick-film GaN grown on both sapphire and spinel substrates has been evaluated by photoluminescence (PL) and raman spectroscopy . The strain-free shallow donor bound exciton recombination energy (I sub 2) is 3.468 eV at 10 K. The raman mode frequency shift with residual strain with estimated as DELTA w = 3.93 cm sup - sup 1 per one GPa for GaN layers on both substrates . The linear relationship between the PL I sub 2 line and the raman E sub 2 mode frequency is DELTA E/DELTA w = 5.12 meV/cm sup - sup 1 , which leads to a stress-induced PL line shift of DELTA E = 20 meV/GPa.

  4. Phase locking of a mode-locked titanium-sapphire laser-based optical frequency comb to a reference laser using a fast piezoelectric actuator.

    Science.gov (United States)

    Hatanaka, Shuhei; Sugiyama, Kazuhiko; Mitaki, Masatoshi; Misono, Masatoshi; Slyusarev, Sergey N; Kitano, Masao

    2017-04-20

    We phase lock an octave-spanning optical frequency comb, generated using a mode-locked titanium-sapphire laser and a photonic-crystal fiber, to a continuous-wave laser line-narrowed to a reference cavity. To phase lock the pulse-repetition frequency, the cavity length of the mode-locked laser is controlled by using a fast piezoelectric-actuated mirror of a servo bandwidth up to 80 kHz. The residual phase noise is 0.35 rad, and 89% of the power is concentrated to the carrier. To apply the system to optical frequency-ratio measurements and to evaluate the phase locking, a simultaneous frequency measurement of the beat between the other mode of the comb and another laser line-narrowed to a different resonance of the common reference cavity is demonstrated.

  5. 444 nm InGaN light emitting diodes on low-defect-density (11\\bar{2}2) GaN templates on patterned sapphire

    Science.gov (United States)

    Khoury, Michel; Li, Hongjian; Kuritzky, Leah Y.; Mughal, Asad J.; DeMierry, Philippe; Nakamura, Shuji; Speck, James S.; DenBaars, Steven P.

    2017-10-01

    Efficient InGaN-based 444 nm blue light-emitting diodes (LEDs) were fabricated on low-defect-density (11\\bar{2}2) semipolar GaN templates grown on patterned r-sapphire. At 20 A/cm2, the packaged (11\\bar{2}2) LEDs exhibited a light output power of 2.9 mW (17.8 mW at 100 A/cm2) and a record peak external quantum efficiency of 6.4% showing a negligible efficiency droop and blue shift with drive currents up to 100 A/cm2. In addition, we demonstrated light extraction simulations for the (11\\bar{2}2) template, which showed that the structured pattern is not only beneficial for limiting the defect propagation but also increases the light extraction by 29% compared with GaN layers grown on planar substrates.

  6. Enhanced c-axis orientation of aluminum nitride thin films by plasma-based pre-conditioning of sapphire substrates for SAW applications

    Science.gov (United States)

    Gillinger, M.; Shaposhnikov, K.; Knobloch, T.; Stöger-Pollach, M.; Artner, W.; Hradil, K.; Schneider, M.; Kaltenbacher, M.; Schmid, U.

    2018-03-01

    Aluminum nitride (AlN) on sapphire has been investigated with two different pretreatments prior to sputter deposition of the AlN layer to improve the orientation and homogeneity of the thin film. An inverse sputter etching of the substrate in argon atmosphere results in an improvement of the uniformity of the alignment of the AlN grains and hence, in enhanced electro-mechanical AlN film properties. This effect is demonstrated in the raw measurements of SAW test devices. Additionally, the impulse response of several devices shows that a poor AlN thin film layer quality leads to a higher signal damping during the transduction of energy in the inter-digital transducers. As a result, the triple-transit signal cannot be detected at the receiver.

  7. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    Directory of Open Access Journals (Sweden)

    Yu-An Chen

    2014-01-01

    Full Text Available GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2 and (1 0 2 peaks decreased from 485 arcsec to 376 arcsec and from 600 arcsec to 322 arcsec, respectively. Transmission electron microscopy results showed that the coalesced GaN growth led to bending threading dislocation. We also proposed a growth model based on results of scanning electron microscopy.

  8. Neutrophil CD64 expression - comparison of two different flow cytometry protocols on EPICs MCL and the Leuko64(™) assay on a Celldyn Sapphire haematology analyser.

    Science.gov (United States)

    Eriksson, Oskar; Douhan Håkansson, Lena; Karawajczyk, Malgorzata; Garwicz, Daniel

    2015-09-01

    To evaluate the Trillium Diagnostics Leuko64(™) assay on Abbott Celldyn Sapphire haematology analyser compared to two flow cytometry protocols on Beckman Coulter EPICS MCL flow cytometer. CD64 expression on neutrophils was determined by two flow cytometry protocols and by a commercial assay on an automatic haematology analyser. The inclusion of study subjects was based on elevated procalcitonin (PCT) values, identifying patients where a systemic infection was suspected. Healthy blood donors were used as a reference group. Statistically significant correlations between the Trillium Diagnostics Leuko64(™) assay and the flow cytometry methods were found when measuring neutrophil CD64 expression. The good correlation between a reference method and an automated haematology analyser method for CD64 expression on neutrophils supports introduction of the latter assay for routine use as an independent biomarker of bacterial infection and inflammation.

  9. Selective-area growth of periodic nanopyramid light-emitting diode arrays on GaN/sapphire templates patterned by multiple-exposure colloidal lithography.

    Science.gov (United States)

    Xiong, Zhuo; Wei, Tongbo; Zhang, Yonghui; Zhang, Xiang; Yang, Chao; Liu, Zhiqiang; Yuan, Guodong; Li, Jinmin; Wang, Junxi

    2017-03-17

    Gallium nitride-based nanopyramid light-emitting diodes are a promising technology to achieve highly efficient solid-state lighting and beyond. Here, periodic nanopyramid light-emitting diode arrays on gallium nitride/sapphire templates were fabricated by selective-area metalorganic chemical vapor deposition and multiple-exposure colloidal lithography. The electric field intensity distribution of incident light going through polystyrene microspheres and photoresist are simulated using finite-different time-domain method. Nitrogen as the carrier gas and a low V/III ratio (ratio of molar flow rate of group-V to group-III sources) are found to be important in order to form gallium nitride nanopyramid. In addition, a broad yellow emission in photoluminescence and cathodoluminescence spectra were observed. This phenomena showed the potential of nanopyramid light-emitting diodes to realize long wavelength visible emissions.

  10. Programming of the Wavelength Stabilization for a Titanium:Sapphire Laser using LabVIEW and Implementation into the CERN ISOLDE RILIS Measurement System

    CERN Document Server

    Rossel, Ralf Erik; Wendt, K; Rothe, S

    In the context of this work the foundation for the commissioning of a comprehensive environmental and operational data acquisition system was established. This development was performed for the Resonance Ionization Laser Ion Source (RILIS) at the ISOLDE radioactive ion beam facility within the European Organization for Nuclear Research CERN. As an essential step towards long-term automated operation, a remote control and wavelength stabilization system for the RILIS titanium:sapphire lasers was put into operation. This required the installation of a data recording infrastructure to work with a distributed sensor network. After operational data within the CERN technical computing network was collected and analyzed, the required wavelength adjustment was automatically performed by a stepper motor-driven correction system. The configuration of the hardware for acquisition and control and the integration of the dedicated system modules was performed using the graphical and data flow oriented programming language ...

  11. Structural, morphology and optical properties of Zn(1-x)CdxO solid solution grown on c-plane sapphire substrate

    Science.gov (United States)

    Fouzri, A.; Boukadhaba, M. A.; Oumezzine, M.; Bchetnia, A.; Sallet, V.

    2012-06-01

    Zn(1-x)CdxO solid solutions with a composition ranging from pure ZnO up to x=0.046 have been grown on cplane sapphire substrates by using metal organic chemical vapor deposition (MO-CVD). The lattice deformation, morphology and optical properties of these films were examined in detail using high resolution X-ray diffraction, atomic force microscopy (AFM) and photoluminescence (PL) as Cd incorporation. Our study reveals significant microstructure modification of Zn(1-x)CdxO from x≥0.7% but single phase of wurtzite structure is maintained for all films. The Pl spectra and the band gap of the Zn(1-x)CdxO film show red shift to visible light range which is interpreted in terms of band gap modulation due to Cd incorporation. Increase of Cd content leads to the emission broadening with growing lower energy peak (at 10K) and degraded crystallinity.

  12. Epitaxial ZnO Thin Films on a-Plane Sapphire Substrates Grown by Ultrasonic Spray-Assisted Mist Chemical Vapor Deposition

    Science.gov (United States)

    Nishinaka, Hiroyuki; Kamada, Yudai; Kameyama, Naoki; Fujita, Shizuo

    2009-12-01

    High-quality epitaxial ZnO thin films were grown by an ultrasonic spray-assisted mist chemical vapor deposition (CVD) on a-plane sapphire substrates with ZnO buffer layers. The ZnO thin films were grown with c-axis orientation without notable rotational domains. Surface morphologies and electrical properties were markedly improved as an effect of the ZnO buffer layers. The mobility in the ZnO epitaxial (main) layer was estimated to be 90 cm2/(V·s), which is reasonably high compared with those in ZnO layers grown by CVD processes. Photoluminescence at a low temperature (4.5 K) revealed a free A-exiton peak, and that at room temperature showed a strong band-edge peak with little deep-level luminescence.

  13. Structural, morphology and optical properties of Zn(1-xCdxO solid solution grown on c-plane sapphire substrate

    Directory of Open Access Journals (Sweden)

    Bchetnia A.

    2012-06-01

    Full Text Available Zn(1-xCdxO solid solutions with a composition ranging from pure ZnO up to x=0.046 have been grown on cplane sapphire substrates by using metal organic chemical vapor deposition (MO-CVD. The lattice deformation, morphology and optical properties of these films were examined in detail using high resolution X-ray diffraction, atomic force microscopy (AFM and photoluminescence (PL as Cd incorporation. Our study reveals significant microstructure modification of Zn(1-xCdxO from x≥0.7% but single phase of wurtzite structure is maintained for all films. The Pl spectra and the band gap of the Zn(1-xCdxO film show red shift to visible light range which is interpreted in terms of band gap modulation due to Cd incorporation. Increase of Cd content leads to the emission broadening with growing lower energy peak (at 10K and degraded crystallinity.

  14. Epitaxial growth of znO nanowires over the ZnO thin films deposited on the Si and sapphire substrates.

    Science.gov (United States)

    Park, No-Kuk; Lee, You Jin; Jung, Ji Young; Lee, Won Guen; Bae, Young Je; Yoon, Suk Hoon; Han, Gi Bo; Ryu, Si Ok; Lee, Tae Jin

    2008-09-01

    Epitaxial growth of ZnO nanowires was carried out using a modified thermal evaporation method with inexpensive experimental setup. ZnO nanowires were synthesized using ZnO thin films. The ZnO thin films were deposited as a buffer layer on silicon and sapphire using an impinging flow reactor (IFR). The IFR system is a modified version of a chemical bath deposition (CBD). Films can be created at low temperature, without any metallic catalysts. The properties of Zinc Oxide films are dependant upon the type of substrate used. The same deposition process with a different substrates yields two films with different properties. The most critical effect on growth of ZnO nanowires were dependent the properties of the buffer layer deposited on the substrate. It was not the type of substrate used. A cost-efficient method for epitaxial growth of single crystal ZnO nanowires is proposed in this work.

  15. Effects of deposition conditions on the structural and acoustic characteristics of (1120) ZnO thin films on R-sapphire substrates.

    Science.gov (United States)

    Wang, Yan; Wasa, Kiyotaka; Zhang, Shu-yi

    2012-08-01

    (1120) ZnO films with the c-axis lying in the plane deposited on R-sapphire substrates by RF magnetron sputtering are studied. The focusing investigation is the effect of substrate positions in the sputtering on structural and acoustic characteristics of the ZnO films. The crystallographic characteristics of the films are characterized by X-ray diffraction analysis. It is found that the crystalline orientation of ZnO films varies with the variation of substrate position deviated from the normal direction of the anode center and there is an optimized deviation position. To investigate the variations of acoustic characteristics of these piezoelectric ZnO films, multilayered structures are prepared to fabricate shear-mode highovertone bulk acoustic resonators (HBARs). The results show that the electromechanical coupling coefficient k(15) of the (1120) ZnO films obtained at the optimized position approaches a maximum.

  16. Morphological dependent Indium incorporation in InGaN/GaN multiple quantum wells structure grown on 4° misoriented sapphire substrate

    Directory of Open Access Journals (Sweden)

    Teng Jiang

    2016-03-01

    Full Text Available The epitaxial layers of InGaN/GaN MQWs structure were grown on both planar and vicinal sapphire substrates by metal organic chemical vapor deposition. By comparing the epitaxial layers grown on planar substrate, the sample grown on 4° misoriented from c-plane toward m-plane substrate exhibited many variations both on surface morphology and optical properties according to the scanning electronic microscopy and cathodoluminescence (CL spectroscopy results. Many huge steps were observed in the misoriented sample and a large amount of V-shape defects located around the boundary of the steps. Atoms force microscopy images show that the steps were inclined and deep grooves were formed at the boundary of the adjacent steps. Phase separation was observed in the CL spectra. CL mapping results also indicated that the deep grooves could effectively influence the localization of Indium atoms and form an In-rich region.

  17. Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH3 interrupted etching.

    Science.gov (United States)

    Son, Ji-Su; Honda, Yoshio; Amano, Hiroshi

    2014-02-10

    Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching. Subsequently, a 2-µm-thick Si-doped a-GaN layer was regrown on the etched a-GaN layer. A fully coalescent n-type a-GaN layer with a low threading dislocation density (~7.5 × 10(8) cm(-2)) and a low basal stacking fault density (~1.8 × 10(5) cm(-1)) was obtained. Compared with a planar sample, the full width at half maximum of the (11-20) X-ray rocking curve was significantly decreased to 518 arcsec along the c-axis direction and 562 arcsec along the m-axis direction.

  18. The impact of purging on the quality of AlGaN/GaN multiple quantum wells grown on AlN/sapphire template

    Science.gov (United States)

    Wang, Shuchang; Zhang, Xiong; Wu, Zili; Zhao, Jianguo; Dai, Qian; Cui, Yiping

    2017-06-01

    The ultraviolet (UV) emitting AlGaN/GaN multiple quantum wells (MQWs) were grown on low dislocation density AlN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). The impact of the purg time on the interface quality of the AlGaN/GaN quantum well was studied. The high resolution x-ray diffraction (XRD) measurement results demonstrate that the density of dislocations was reduced significantly with the purge time after growth of AlGaN barrier layer and GaN well layer was determined to be 4 min and 2 min, respectively. The mechanism of defect formation in quantum wells was investigated by scanning electron microscope (SEM) measurement.

  19. Hydrogen maser clocks in space for solid-Earth research and time-transfer applications: Experiment overview and evaluation of Russian miniature sapphire loaded cavity

    Science.gov (United States)

    Busca, G.; Bernier, L. G.; Silvestrin, P.; Feltham, S.; Gaygerov, B. A.; Tatarenkov, V. M.

    1994-05-01

    The Observatoire Cantonal de Neuchatel (ON) is developing for ESTEC a compact H-maser for space use based upon a miniature sapphire loaded microwave cavity, a technique pioneered at VNIIFTRI. Various contacts between West-European parties, headed by ESA, and the Russian parties, headed by ESA, led to the proposal for flying two H-masers on Meteor 3M, a Russian meteorology satellite in low polar orbit. The experiment will include two masers, one provided by ON and the other by VNIIFTRI. T/F transfer and precise positioning will be performed by both a microwave link, using PRARE equipment, and an optical link, using LASSO-like equipment. The main objectives of the experiment are precise orbit determination and point positioning for geodetic/geophysical research, ultra-accurate time comparison and dissemination as well as in-orbit demonstration of operation and performance of H-masers. Within the scope of a preliminary space H-maser development phase performed for ESTEC at ON in preparation to the joint experiment, a Russian miniature sapphire loaded microwave cavity, on loan from VNIIFTRI, was evaluated in a full-size EFOS hydrogen maser built by ON. The experimental evaluation confirmed the theoretical expectation that with a hydrogen storage volume of only 0.65 liter an atomic quality factor of 1.5 x 10(exp 9) can be obtained for a -105 dBm output power. This represents a theoretical Allan deviation of 1.7 x 10(exp -15) averaged on a 1000 s time interval. From a full-size design to a compact one, therefore, the sacrifice in performance due to the reduction of the storage volume is very small.

  20. Effects of neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment on ovarian development of the sapphire devil, Chrysiptera cyanea.

    Science.gov (United States)

    Badruzzaman, Muhammad; Imamura, Satoshi; Takeuchi, Yuki; Ikegami, Taro; Takemura, Akihiro

    2015-02-01

    In the neuroendocrine system controlling fish reproduction, dopamine (DA) acts as a gonadotropin inhibitory factor and plays a role in regulating gonadal development of certain species. The present study examined the effects of chemical destruction of dopaminergic neurons in the brain on DA production and ovarian development in the sapphire devil Chrysiptera cyanea, a reef-associated damselfish. The avidin-biotin-peroxidase complex method using an antibody against tyrosine hydroxylase (TH), a critical enzyme in the DA synthesis pathway, identified a population of dopaminergic neurons with somata in the anteroventral preoptic nucleus of the diencephalon and fibers terminating in the proximal pars distalis of the pituitary. Maintaining fish in seawater containing 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at 0.02 and 0.2 µg/mL for 2 days resulted in decreases in DA, 3,4-dihydroxyphenylacetic acid (DOPAC; DA metabolite), and DA metabolic rate in the whole brain. The number of TH-positive neurons in the diencephalon decreased after 0.02 µg/mL MPTP treatment for 2 days. These results suggest that MPTP treatment destroys TH-positive neurons in the diencephalon, thereby decreasing the synthesis and release of DA from the brain. This treatment rescued ovarian development in fish with artificially retracted ovaries during the spawning season. The gonadosomatic index of MPTP-treated fish 5 and 7 days after treatment was significantly higher than that of control fish. Oocytes in the vitellogenic stages were observed in the ovaries of MPTP-treated fish, but not in control fish. These results suggest that DA in the brain drives ovarian development in the sapphire devil.

  1. Study of YBaCo{sub 4}O{sub 7+{delta}} thin films grown by sputtering technique on (1012)-oriented sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, J.F.; Izquierdo, J.L. [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia); Gomez, A. [Laboratorio de Caracterizacion de Materiales, Facultad de Minas, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia); Arnache, O.; Osorio, J. [Grupo de Estado Solido, Departamento de Fisica, Universidad de Antioquia, A.A. 1226 Medellin (Colombia); Marin, J.; Paucar, C. [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia); Moran, O., E-mail: omoranc@unal.edu.c [Laboratorio de Materiales Ceramicos y Vitreos, Departamento de Fisica, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia)

    2011-03-01

    We report the growth of thin films of the cobaltite YBaCo{sub 4}O{sub 7+{delta}} by means of the dc magnetron sputtering technique at high oxygen pressure onto r (1012) sapphire substrates. The films were characterized according to their structural, morphological, electrical, magnetic, and optical properties. An analysis of the X-ray diffraction pattern indicates that the films grown on r-sapphire substrates are single phase polycrystalline. Despite the high growth temperature (850 {sup o}C), no indication of interface reaction (formation of BaAlO{sub 4} or Y{sub 2}O{sub 3}) is detected. Measurements of resistivity as a function of temperature reveal a semiconductor-like character of the grown films. No indication of possible transitions is observed in the temperature range 50-300 K. The electronic transport mechanism seems to be dominated by Mott variable range hopping (VRH) conduction. Fitting the VRH model to the experimental data allows one to estimate the density of states of the material at the Fermi level N(E{sub F}). The resistivity measured in magnetic fields as strong as 5 T increases notably, and positive magnetoresistance values as high as {approx} 60% at 100 K are obtained. Magnetization measurements show well defined hysteresis loops at 300 K and 5 K. Nevertheless, calculated values of the magnetization have ended up being too small for the ferro- or ferrimagnetic states. Raman spectra, in turn, allow one to identify bands associated with vibrating modes of CoO{sub 4} and YO{sub 6} in tetrahedral and octahedral configurations, respectively. Additional bands which seem to stem from Co ions in octahedral configuration are also clearly identified. Measurements of transmittance and reflectance show two well defined energy gaps at 3.7 and 2.2 eV.

  2. Polycrystalline Ba0.6Sr0.4TiO3 thin films on r-plane sapphire: Effect of film thickness on strain and dielectric properties

    Science.gov (United States)

    Fardin, E. A.; Holland, A. S.; Ghorbani, K.; Akdogan, E. K.; Simon, W. K.; Safari, A.; Wang, J. Y.

    2006-10-01

    Polycrystalline Ba0.6Sr0.4TiO3 (BST) films grown on r-plane sapphire exhibit strong variation of in-plane strain over the thickness range of 25-400nm. At a critical thickness of ˜200nm, the films are strain relieved; in thinner films, the strain is tensile, while compressive strain was observed in the 400nm film. Microwave properties of the films were measured from 1to20GHz by the interdigital capacitor method. A capacitance tunability of 64% was observed in the 200nm film, while thinner films showed improved Q factor. These results demonstrate the possibility of incorporating frequency agile BST-based devices into the silicon on sapphire process.

  3. Laser welding of fused silica glass with sapphire using a non- stoichiometric, fresnoitic Ba2TiSi2O8·3 SiO2 thin film as an absorber

    Science.gov (United States)

    de Pablos-Martín, A.; Lorenz, M.; Grundmann, M.; Höche, Th.

    2017-07-01

    Laser welding of dissimilar materials is challenging, due to their difference in coefficients of thermal expansion (CTE). In this work, fused silica-to-sapphire joints were achieved by employment of a ns laser focused in the intermediate Si-enriched fresnoitic glass thin film sealant. The microstructure of the bonded interphase was analyzed down to the nanometer scale and related to the laser parameters used. The crystallization of fresnoite in the glass sealant upon laser process leads to an intense blue emission intensity under UV excitation. This crystallization is favored in the interphase with the silica glass substrate, rather than in the border with the sapphire. The formation of SiO2 particles was confirmed, as well. The bond quality was evaluated by scanning acoustic microscopy (SAM). The substrates remain bonded even after heat treatment at 100 °C for 30 min, despite the large CTE difference between both substrates.

  4. Electrical properties of ZnO thin films grown on a-plane sapphire substrates using catalytically generated high-energy H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, N.; Takeuchi, T.; Nagatomi, E.; Kato, T.; Umemoto, H.; Yasui, K., E-mail: kyasui@vos.nagaokaut.ac.jp

    2013-12-31

    The electrical properties of zinc oxide (ZnO) epitaxial films grown by chemical vapor deposition (CVD) using high-energy H{sub 2}O generated by H{sub 2}–O{sub 2} reactions on Pt nanoparticles were evaluated. High-energy ZnO precursors formed by the reaction between dimethylzinc gas molecules and H{sub 2}O molecules were supplied to the substrate surface. The ZnO epitaxial films were grown directly on a-plane sapphire (a-Al{sub 2}O{sub 3}) substrates at 773 K without any buffer layer. The electron mobility (μ{sub H}) at room temperature increased from 30 to 190 cm{sup 2}V{sup −1} s{sup −1} with increasing film thickness from 100 nm to 2800 nm. The μ{sub H} increased significantly with decreasing temperature to approximately 100–150 K, but it decreased at temperatures less than 100 K for films thicker than 500 nm. The μ{sub H} of the ZnO film (189 cm{sup 2}V{sup −1} s{sup −1}) at 290 K increased to 660 cm{sup 2}V{sup −1} s{sup −1} at 100 K. In contrast, μ{sub H} hardly changed with temperature for films thinner than 500 nm. According to a two-layer Hall-effect model, the μ{sub H} and electron concentration of the upper layer were corrected based on the above results, assuming that the degenerate layer had a thickness of 100 nm. - Highlights: • ZnO films were grown by CVD using reaction of high-energy H{sub 2}O and dimethylzinc gas. • Films were grown on a-plane sapphire substrates at 773 K. • ZnO film at 2.8 µm thick exhibited a large electron mobility of 189 cm{sup 2}/Vs at room temperature. • From the crystallinity and the electrical properties for various film thicknesses, the structure of the ZnO films was estimated. • The electron mobility and electron concentration of the upper layer were corrected according to a two-layer Hall-effect model.

  5. Selective area growth of AlN/GaN nanocolumns on (0001) and (11-22) GaN/sapphire for semi-polar and non-polar AlN pseudo-templates.

    Science.gov (United States)

    Bengoechea-Encabo, A; Albert, S; Müller, M; Xie, M-Y; Veit, P; Bertram, F; Sanchez-Garcia, M A; Zúñiga-Pérez, J; de Mierry, P; Christen, J; Calleja, E

    2017-09-08

    Despite the strong interest in optoelectronic devices working in the deep ultraviolet range, no suitable low cost, large-area, high-quality AlN substrates have been available up to now. The aim of this work is the selective area growth of AlN nanocolumns by plasma assisted molecular beam epitaxy on polar (0001) and semi-polar (11-22) GaN/sapphire templates. The resulting AlN nanocolumns are vertically oriented with semi-polar {1-103} top facets when grown on (0001) GaN/sapphire, or oriented at 58° from the template normal and exposing {1-100} non-polar top facets when growing on (11-22) GaN/sapphire, in both cases reaching filling factors ≥80%. In these kinds of arrays each nanostructure could function as a building block for an individual nano-device or, due to the large filling factor values, the overall array top surfaces could be seen as a quasi (semi-polar or non-polar) AlN pseudo-template.

  6. Comprehensive strain and band gap analysis of PA-MBE grown AlGaN/GaN heterostructures on sapphire with ultra thin buffer

    Energy Technology Data Exchange (ETDEWEB)

    Mahata, Mihir Kumar; Ghosh, Saptarsi; Jana, Sanjay Kumar; Bag, Ankush; Kumar, Rahul [Advanced Technology Development Center, Indian Institute of Technology, Kharagpur, 721302 (India); Chakraborty, Apurba; Biswas, Dhrubes [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, 721302 (India); Mukhopadhyay, Partha [Rajendra Mishra School of Engineering Entrepreneurship, Indian Institute of Technology, Kharagpur, 721302 (India)

    2014-11-15

    In this work, cluster tool (CT) Plasma Assisted Molecular Beam Epitaxy (PA-MBE) grown AlGaN/GaN heterostructure on c-plane (0 0 0 1) sapphire (Al{sub 2}O{sub 3}) were investigated by High Resolution X-ray Diffraction (HRXRD), Room Temperature Raman Spectroscopy (RTRS), and Room Temperature Photoluminescence (RTPL). The effects of strain and doping on GaN and AlGaN layers were investigated thoroughly. The out-of-plane (‘c’) and in-plane (‘a’) lattice parameters were measured from RTRS analysis and as well as reciprocal space mapping (RSM) from HRXRD scan of (002) and (105) plane. The in-plane (out-of plane) strain of the samples were found to be −2.5 × 10{sup −3}(1 × 10{sup −3}), and −1.7 × 10{sup −3}(2 × 10{sup −3}) in GaN layer and 5.1 × 10{sup −3} (−3.3 × 10{sup −3}), and 8.8 × 10{sup −3}(−1.3 × 10{sup −3}) in AlGaN layer, respectively. In addition, the band structures of AlGaN/GaN interface were estimated by both theoretical (based on elastic theory) and experimental observations of the RTPL spectrum.

  7. Impact of sapphire nitridation on formation of Al-polar inversion domains in N-polar AlN epitaxial layers

    Science.gov (United States)

    Stolyarchuk, N.; Markurt, T.; Courville, A.; March, K.; Tottereau, O.; Vennéguès, P.; Albrecht, M.

    2017-10-01

    In this work, we study the basic processes during the initial stages of growth which control polarity in N-polar AlN films grown on c-plane sapphire substrates by metalorganic chemical vapor deposition. More specifically, we study the morphology and atomic structure of the films as dependent on nitridation conditions, i.e., duration and temperature, by atomic force microscopy, high resolution transmission electron microscopy ,and high resolution high-angle annular dark field scanning transmission electron microscopy. Our experimental results show that beyond a critical temperature of 1000 °C in addition to an omnipresent two-dimensional aluminum-oxynitride layer, three-dimensional Al-polar AlN islands form. While the aluminum-oxynitride layer is unstable under high temperature growth conditions and results in N-polar films, Al-polar islands are stable and induce Al-polar columnar inversion domains in the N-polar AlN films. Appropriate nitridation conditions (approximately 10 minutes at T = 850 °C-950 °C) and adjustment of growth parameters (reactor pressure, NH3 flux, etc.) prevent the formation of Al-polar islands, which is essential for achieving N-polar films free of inversion domains.

  8. Time-resolved photoluminescence and photoreflectance spectroscopy of GaN layers grown on SiN-treated sapphire substrate: Optical properties evolution at different growth stages

    Science.gov (United States)

    Bouzidi, M.; Soltani, S.; Chine, Z.; Rebey, A.; Shakfa, M. K.

    2017-11-01

    In this paper, we present a systematic study of the optical properties evolution of GaN films during the complete growth process on SiN-treated sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy. The growth process was monitored using in-situ laser reflectometry and was interrupted at different stages to obtain the studied samples. The obtained samples were ex-situ characterized by means of photoluminescence (PL), photoreflectance (PR) and time-resolved PL (TRPL) spectroscopies. The PL emission from the samples of the initial growth stages originates from nano-crystallite and defect states due to the 3D growth mode. However, with increasing layer thickness, the 2D growth mode is established, and the PL spectrum is dominated by free-exciton emission. The electric field extracted by applying the Franz-Keldysh oscillation (FKO) theory on the PR spectra shows a trend to decrease as the GaN layer thickness is increased. For fully coalesced layers, the FKO totally disappears, and the PR spectrum is dominated by free-exciton transitions. TRPL measurements demonstrate the contribution of two processes to the PL decay, i.e., fast and slow components. While the slow decay time reveals the same sensitivity to different types of dislocations (twist and tilt mosaics), the fast decay time is more affected by the twist mosaic than by the tilt one.

  9. Effects of annealing temperature and duration on the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire.

    Directory of Open Access Journals (Sweden)

    Mao Sui

    Full Text Available Metallic nanostructures (NSs have been widely adapted in various applications and their physical, chemical, optical and catalytic properties are strongly dependent on their surface morphologies. In this work, the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire (0001 is demonstrated by the control of annealing temperature and dwelling duration with the distinct thickness of Pt films. The formation of Pt NSs is led by the surface diffusion, agglomeration and surface and interface energy minimization of Pt thin films, which relies on the growth parameters such as system temperature, film thickness and annealing duration. The Pt layer of 10 nm shows the formation of overlaying NPs below 650°C and isolated Pt nanoparticles above 700°C based on the enhanced surface diffusion and Volmer-Weber growth model whereas larger wiggly nanostructures are formed with 20 nm thick Pt layers based on the coalescence growth model. The morphologies of Pt nanostructures demonstrate a sharp distinction depending on the growth parameters applied. By the control of dwelling duration, the gradual transition from dense Pt nanoparticles to networks-like and large clusters is observed as correlated to the Rayleigh instability and Ostwald ripening. The various Pt NSs show a significant distinction in the reflectance spectra depending on the morphology evolution: i.e. the enhancement in UV-visible and NIR regions and the related optical properties are discussed in conjunction with the Pt NSs morphology and the surface coverage.

  10. Defect structure of high temperature hydride vapor phase epitaxy-grown epitaxial (0 0 0 1) AlN/sapphire using growth mode modification process

    Science.gov (United States)

    Su, Xujun; Zhang, Jicai; Huang, Jun; Zhang, Jinping; Wang, Jianfeng; Xu, Ke

    2017-06-01

    Defect structures were investigated by transmission electron microscopy for AlN/sapphire (0 0 0 1) epilayers grown by high temperature hydride vapor phase epitaxy using a growth mode modification process. The defect structures, including threading dislocations, inversion domains, and voids, were analyzed by diffraction contrast, high-resolution imaging, and convergent beam diffraction. AlN film growth was initiated at 1450 °C with high V/III ratio for 8 min. This was followed by low V/III ratio growth for 12 min. The near-interfacial region shows a high density of threading dislocations and inversion domains. Most of these dislocations have Burgers vector b = 1/3〈1 1 2 0〉 and were reduced with the formation of dislocation loops. In the middle range 400 nm < h < 2 μm, dislocations gradually aggregated and reduced to ∼109 cm-2. The inversion domains have a shuttle-like shape with staggered boundaries that deviate by ∼ ±5° from the c axis. Above 2 μm thickness, the film consists of isolated threading dislocations with a total density of 8 × 108 cm-2. Most of threading dislocations are either pure edge or mixed dislocations. The threading dislocation reduction in these films is associated with dislocation loops formation and dislocation aggregation-interaction during island growth with high V/III ratio.

  11. Characterization of a pulsed injection-locked Ti:sapphire laser and its application to high resolution resonance ionization spectroscopy of copper

    Science.gov (United States)

    Sonnenschein, V.; Moore, I. D.; Raeder, S.; Reponen, M.; Tomita, H.; Wendt, K.

    2017-08-01

    A high repetition rate pulsed Ti:sapphire laser injection-locked to a continuous wave seed source is presented. A spectral linewidth of 20 MHz at an average output power of 4 W is demonstrated. An enhanced tuning range from 710-920 nm with a single broadband mirror set is realized by the inclusion of a single thin birefringent quartz plate for suppression of unseeded emission. The spectral properties have been analyzed using both a scanning Fabry-Pérot interferometer as well as crossed beam resonance ionization spectroscopy of the hyperfine levels of natural copper. Delayed ionization of the long-lived excited state is demonstrated for increased resolution. For the excited state hyperfine coupling constant of the 244 nm 4s 2S1/2→ 4s4p4P°1/2 ground-state transition in {\\hspace{0pt}}63 Cu, a factor of ten reduction in error compared to previous literature was achieved. The described laser system has been in operation at several radioactive ion beam facilities.

  12. Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, A., E-mail: ali.soltani@iemn.univ-lille1.fr; Stolz, A.; Gerbedoen, J.-C.; Rousseau, M.; Bourzgui, N.; De Jaeger, J.-C. [Institut d' Électronique, Microélectronique et Nanotechnologie, UMR-CNRS 8520, PRES Université Lille Nord de France, Cité Scientifique, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cedex (France); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON, UMR-CNRS 6082, ENSSAT 6, rue de Kerampont, CS 80518, 22305 Lannion Cedex (France); Mattalah, M. [Laboratoire de Microélectronique, Université Djilali Liabes, 22000 Sidi Bel Abbes (Algeria); Barkad, H. A. [Institut Universitaire Technologique Industriel, Université de Djibouti, Avenue Georges Clémenceau, BP 1904 Djibouti (Djibouti); Mortet, V. [Institute of Physics of Academy of Sciences of Czech Republic, Fyzikální ústav AV CR, v.v.i., Na Slovance 1999/2 (Czech Republic); BenMoussa, A. [Solar Terrestrial Center of Excellence, Royal Observatory of Belgium, Circular 3, B-1180 Brussels (Belgium)

    2014-04-28

    Optical waveguiding properties of a thick wurtzite aluminum nitride highly [002]-textured hetero-epitaxial film on (001) basal plane of sapphire substrate are studied. The physical properties of the film are determined by X-ray diffraction, atomic force microscopy, microRaman, and photocurrent spectroscopy. The refractive index and the thermo-optic coefficients are determined by m-lines spectroscopy using the classical prism coupling technique. The optical losses of this planar waveguide are also measured in the spectral range of 450–1553 nm. The lower value of optical losses is equal to 0.7 dB/cm at 1553 nm. The optical losses due to the surface scattering are simulated showing that the contribution is the most significant at near infrared wavelength range, whereas the optical losses are due to volume scattering and material absorption in the visible range. The good physical properties and the low optical losses obtained from this planar waveguide are encouraging to achieve a wide bandgap optical guiding platform from these aluminum nitride thin films.

  13. High-quality AlN film grown on a nanosized concave-convex surface sapphire substrate by metalorganic vapor phase epitaxy

    Science.gov (United States)

    Yoshikawa, Akira; Nagatomi, Takaharu; Morishita, Tomohiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

    2017-10-01

    We developed a method for fabricating high-crystal-quality AlN films by combining a randomly distributed nanosized concavo-convex sapphire substrate (NCC-SS) and a three-step growth method optimized for NCC-SS, i.e., a 3-nm-thick nucleation layer (870 °C), a 150-nm-thick high-temperature layer (1250 °C), and a 3.2-μm-thick medium-temperature layer (1110 °C). The NCC-SS is easily fabricated using a conventional metalorganic vapor phase epitaxy reactor equipped with a showerhead plate. The resultant AlN film has a crack-free and single-step surface with a root-mean-square roughness of 0.5 nm. The full-widths at half-maxima of the X-ray rocking curve were 50/250 arcsec for the (0002)/(10-12) planes, revealing that the NCC surface is critical for achieving such a high-quality film. Hexagonal-pyramid-shaped voids at the AlN/NCC-SS interface and confinement of dislocations within the 150-nm-thick high-temperature layer were confirmed. The NCC surface feature and resultant faceted voids play an important role in the growth of high-crystal-quality AlN films, likely via localized and/or disordered growth of AlN at the initial stage, contributing to the alignment of high-crystal-quality nuclei and dislocations.

  14. Correlation of growth temperature with stress, defect states and electronic structure in an epitaxial GaN film grown on c-sapphire via plasma MBE.

    Science.gov (United States)

    Krishna, Shibin; Aggarwal, Neha; Mishra, Monu; Maurya, K K; Singh, Sandeep; Dilawar, Nita; Nagarajan, Subramaniyam; Gupta, Govind

    2016-03-21

    The relationship of the growth temperature with stress, defect states, and electronic structure of molecular beam epitaxy grown GaN films on c-plane (0001) sapphire substrates is demonstrated. A minimum compressively stressed GaN film is grown by tuning the growth temperature. The correlation of dislocations/defects with the stress relaxation is scrutinized by high-resolution X-ray diffraction and photoluminescence measurements which show a high crystalline quality with significant reduction in the threading dislocation density and defect related bands. A substantial reduction in yellow band related defect states is correlated with the stress relaxation in the grown film. Temperature dependent Raman analysis shows the thermal stability of the stress relaxed GaN film which further reveals a downshift in the E2 (high) phonon frequency owing to the thermal expansion of the lattice at elevated temperatures. Electronic structure analysis reveals that the Fermi level of the films is pinned at the respective defect states; however, for the stress relaxed film it is located at the charge neutrality level possessing the lowest electron affinity. The analysis demonstrates that the generated stress not only affects the defect states, but also the crystal quality, surface morphology and electronic structure/properties.

  15. Super-aligned carbon nanotubes patterned sapphire substrate to improve quantum efficiency of InGaN/GaN light-emitting diodes.

    Science.gov (United States)

    Shan, Liang; Wei, Tongbo; Sun, Yuanping; Zhang, Yonghui; Zhen, Aigong; Xiong, Zhuo; Wei, Yang; Yuan, Guodong; Wang, Junxi; Li, Jinmin

    2015-07-27

    In this paper, the high performance GaN-based light-emitting diodes (LEDs) on carbon-nanotube-patterned sapphire substrate (CNPSS) by metal-organic chemical vapor deposition (MOCVD) are demonstrated. By studying the mechanism of nucleation, we analyze the reasons of the crystal quality improvement induced by carbon nanotubes (CNTs) in different growth process. Combining with low temperatures photoluminescence (PL) measurements and two-dimensional (2D) finite difference time-domain (FDTD) simulation results, we conclude that the improvement of optical properties and electrical properties of CNPSS mainly originates from the improvement of the internal quantum efficiency (IQE) due to decreased dislocation density during nano-epitaxial growth on CNPSS. Additionally, in order to reduce the light absorption characteristics of CNTs, different time annealing under the oxygen environment is carried out to remove part of CNTs. Under 350 mA current injections, the light output power (LOP) of CNPSS-LED annealed 2 h and 10 h exhibit 11% and 6% enhancement, respectively, compared to that of the CNPSS-LED without annealing. Therefore, high temperature annealing can effectively remove parts of CNTs and further increase the LOP, while overlong annealing time has caused degradation of the quantum well resulting in the attenuation of optical power.

  16. Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate.

    Science.gov (United States)

    Lee, Chia-Yu; Tzou, An-Jye; Lin, Bing-Cheng; Lan, Yu-Pin; Chiu, Ching-Hsueh; Chi, Gou-Chung; Chen, Chi-Hsiang; Kuo, Hao-Chung; Lin, Ray-Ming; Chang, Chun-Yen

    2014-01-01

    The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 × 10(7) cm(-2) to 2.6 × 10(7) cm(-2). Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.

  17. Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range

    Science.gov (United States)

    Soltani, A.; Stolz, A.; Charrier, J.; Mattalah, M.; Gerbedoen, J.-C.; Barkad, H. A.; Mortet, V.; Rousseau, M.; Bourzgui, N.; BenMoussa, A.; De Jaeger, J.-C.

    2014-04-01

    Optical waveguiding properties of a thick wurtzite aluminum nitride highly [002]-textured hetero-epitaxial film on (001) basal plane of sapphire substrate are studied. The physical properties of the film are determined by X-ray diffraction, atomic force microscopy, microRaman, and photocurrent spectroscopy. The refractive index and the thermo-optic coefficients are determined by m-lines spectroscopy using the classical prism coupling technique. The optical losses of this planar waveguide are also measured in the spectral range of 450-1553 nm. The lower value of optical losses is equal to 0.7 dB/cm at 1553 nm. The optical losses due to the surface scattering are simulated showing that the contribution is the most significant at near infrared wavelength range, whereas the optical losses are due to volume scattering and material absorption in the visible range. The good physical properties and the low optical losses obtained from this planar waveguide are encouraging to achieve a wide bandgap optical guiding platform from these aluminum nitride thin films.

  18. Complementary Molecular Dynamics and X-ray Reflectivity Study of an Imidazolium-Based Ionic Liquid at a Neutral Sapphire Interface.

    Science.gov (United States)

    Brkljača, Zlatko; Klimczak, Michael; Miličević, Zoran; Weisser, Matthias; Taccardi, Nicola; Wasserscheid, Peter; Smith, David M; Magerl, Andreas; Smith, Ana-Sunčana

    2015-02-05

    Understanding the molecular-level behavior of ionic liquids (ILs) at IL-solid interfaces is of fundamental importance with respect to their application in, for example, electrochemical systems and electronic devices. Using a model system, consisting of an imidazolium-based IL ([C2Mim][NTf2]) in contact with a sapphire substrate, we have approached this problem using a complementary combination of high-resolution X-ray reflectivity measurements and atomistic molecular dynamics (MD) simulations. Our strategy enabled us to compare experimental and theoretically calculated reflectivities in a direct manner, thereby critically assessing the applicability of several force-field variants. On the other hand, using the best-matching MD description, we are able to describe the nature of the model IL-solid interface in appreciable detail. More specifically, we find that characteristic interactions between the surface hydroxyl groups and donor and acceptor sites on the IL constituents have a dominant role in inducing a multidimensional layering profile of the cations and anions.

  19. Origin of the 2.45 eV luminescence band observed in ZnO epitaxial layers grown on c-plane sapphire by chemical vapour deposition

    Science.gov (United States)

    Saroj, R. K.; Dhar, S.

    2014-12-01

    Zinc oxide epitaxial layers have been grown on c-plane sapphire substrates by the chemical vapour deposition (CVD) technique. A structural study shows (0001)-oriented films with good crystalline quality. The temperature and excitation power dependence of the photoluminescence (PL) characteristics of these layers is studied as a function of various growth parameters, such as the growth temperature, oxygen flow rate and Zn flux, which suggest that the origin of the broad visible luminescence (VL), which peaks at 2.45 eV, is the transition between the conduction band and the Zn vacancy acceptor states. A bound excitonic transition observed at 3.32 eV in low temperature PL has been identified as an exciton bound to the neutral Zn vacancy. Our study also reveals the involvement of two activation processes in the dynamics of VL, which has been explained in terms of the fluctuation of the capture barrier height for the holes trapped in Zn vacancy acceptors. The fluctuation, which might be a result of the inhomogeneous distribution of Zn vacancies, is found to be associated with an average height of 7 and 90 meV, respectively, for the local and global maxima.

  20. Effect of Zn and Te beam intensity upon the film quality of ZnTe layers on severely lattice mismatched sapphire substrates by molecular beam epitaxy

    Science.gov (United States)

    Nakasu, Taizo; Sun, W.; Kobayashi, M.; Asahi, T.

    2017-06-01

    Zinc telluride layers were grown on highly-lattice-mismatched sapphire substrates by molecular beam epitaxy, and their crystallographic properties were studied by means of X-ray diffraction pole figures. The crystal quality of the ZnTe thin film was further studied by scanning electron microscopy, X-ray rocking curves and low-temperature photoluminescence measurements. These methods show that high-crystallinity (111)-oriented single domain ZnTe layers with the flat surface and good optical properties are realized when the beam intensity ratio of Zn and Te beams is adjusted. The migration of Zn and Te was inhibited by excess surface material and cracks were appeared. In particular, excess Te inhibited the formation of a high-crystallinity ZnTe film. The optical properties of the ZnTe layer revealed that the exciton-related features were dominant, and therefore the film quality was reasonably high even though the lattice constants and the crystal structures were severely mismatched.

  1. Three dimensional characterization of GaN-based light emitting diode grown on patterned sapphire substrate by confocal Raman and photoluminescence spectromicroscopy

    Science.gov (United States)

    Li, Heng; Cheng, Hui-Yu; Chen, Wei-Liang; Huang, Yi-Hsin; Li, Chi-Kang; Chang, Chiao-Yun; Wu, Yuh-Renn; Lu, Tien-Chang; Chang, Yu-Ming

    2017-03-01

    We performed depth-resolved PL and Raman spectral mappings of a GaN-based LED structure grown on a patterned sapphire substrate (PSS). Our results showed that the Raman mapping in the PSS-GaN heterointerface and the PL mapping in the InxGa1-xN/GaN MQWs active layer are spatially correlated. Based on the 3D construction of E2(high) Raman peak intensity and frequency shift, V-shaped pits in the MQWs can be traced down to the dislocations originated in the cone tip area of PSS. Detail analysis of the PL peak distribution further revealed that the indium composition in the MQWs is related to the residual strain propagating from the PSS-GaN heterointerface toward the LED surface. Numerical simulation based on the indium composition distribution also led to a radiative recombination rate distribution that shows agreement with the experimental PL intensity distribution in the InxGa1-xN/GaN MQWs active layer.

  2. Study on the dimensional, configurational and optical evolution of palladium nanostructures on c-plane sapphire by the control of annealing temperature and duration

    Science.gov (United States)

    Sui, Mao; Zhang, Quanzhen; Kunwar, Sundar; Pandey, Puran; Li, Ming-Yu; Lee, Jihoon

    2017-09-01

    Metallic nanostructures can find various applications such as in optoelectronic devices, nanostructure synthesis and catalytic applications and their applicability vary depending on their size, density and configuration dependent properties. In this paper, the dimensional and configurational evolution of self-assembled palladium (Pd) nanostructures is systematically studied on c-plane sapphire with the control of annealing temperature (AT) and annealing duration with the initial Pd layers of various thicknesses. Depending on the AT, two distinct growth regimes are observed based on the concurrent effect of surface diffusion, surface energy minimization and Pd sublimation: i.e. (i) agglomeration of Pd nano-clusters from voids (500 < AT ≤ 650 °C) and (ii) round nanoparticle (NP) fabrication (650 °C < AT ≤ 900 °C). At 950 °C, due to the sublimation of Pd atoms, substantial decrease in the NP dimension is witnessed and results in the ring patterns around the NPs. Additional investigation is performed at 950 °C to reveal the annealing duration effect on the NP evolution. Due to the dual effect of the Oswald ripening and atom sublimation, initially the dimension of NPs is grown and then gradually decays along with the duration, resulting in an inverted 'V' pattern evolution in diameter and height. Moreover, the evolution of optical properties such as absorption band and average reflectance are studied with the corresponding reflectance spectra as a function of wavelength over UV, visible and NIR region. The Raman spectra analysis depicts the variation of lattice vibration peak intensity and position based on the surface morphology of the Pd nanostructures.

  3. Evolution of morphological and optical properties of self-assembled Ag nanostructures on c-plane sapphire (0001) by the precise control of deposition amount

    Science.gov (United States)

    Kunwar, Sundar; Li, Ming-Yu; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Lee, Jihoon

    2016-12-01

    Silver (Ag) nanoparticles (NPs) have been widely adapted in various optoelectronic and sensing applications due to the size, shape and density dependent tunable properties. In this work, the systematic control of the size, configuration and density of self-assembled Ag nanostructures on c-plane sapphire (0001) is demonstrated through the solid state dewetting process by the variation of deposition amount (DA) at two distinctive temperature of 400 °C and 650 °C. The corresponding morphological evolution of Ag nanostructures is systematically discussed based on the diffusion, Volmer-Weber and coalescence growth model. In specific, at the relatively lower temperature of 400 °C, the Ag nanostructures evolve in three distinctive regimes based on the DA control: i.e. the dome-shaped Ag NPs between 2 and 14 nm (regime I), the irregular nano-mounds (NMs) between 20 and 40 nm (regime II), and the coalescence of Ag NMs into a layer between 60 and 200 nm (regime III). Meanwhile, at the relatively higher temperature of 650 °C, due to growth regime shift induced by the enhanced surface diffusion based on the increased thermal energy, the connected Ag NMs are resulted even at higher DAs and evolve along with the gradually increased DAs. The evolution of optical properties such as average reflectivity, plasmonic absorption band and the reflectance maxima (peaks) very sensitively respond to the evolution of size, shape and spacing of Ag nanostructures and discussed based on the surface plasmon, reflection and scattering. Specifically, the dome-shaped configuration exhibits strong absorption in the NIR region and weak absorption in visible region while the elongated NMs show the enhanced absorption in visible region. Furthermore, the Raman spectra (A 1g vibrational mode) of the Ag nanostructures demonstrate the strong correlation with the evolution of size, density and surface coverage of the nanostructures.

  4. P-type nitrogen- and phosphorus-doped ZnO thin films grown by pulsed laser deposition on sapphire substrates

    Science.gov (United States)

    Mosnier, J.-P.; Chakrabarti, S.; Doggett, B.; McGlynn, E.; Henry, M. O.; Meaney, A.

    2007-02-01

    Nitrogen- and phosphorus-doped ZnO thin films were grown by pulsed laser deposition using an electron cyclotron resonance (ECR) nitrogen plasma ion source or a ZnO:P IIO 5 doped target, as the dopant source, respectively. Both types of films were grown on sapphire substrates first coated at low temperature with a ZnO buffer layer. For the N-doped ZnO thin films, temperature-dependent Van der Pauw measurements showed consistent p-type behavior over the measured temperature range of 200-450 K, with typical room temperature acceptor concentrations and mobilities of 5 x 10 15 cm -3 and 5.61 cm2/Vs, respectively. The room-temperature photoluminescence spectrum of a N-doped ZnO thin film featured a broad near band-edge emission at about 3.1 eV photon energy with a width of 0.5 eV. XPS studies confirmed the incorporation of nitrogen in the samples. The ZnO:P layers (with phosphorus concentrations of between 0.01 and 1 wt %) typically showed weak n-type conduction in the dark, with a resistivity of 70 Ω.cm, a Hall mobility of μ n ~ 0.5 cm2V -1s -1 and a carrier concentration of n ~ 3 x 10 17 cm -3 at room temperature. After exposure to an incandescent light source, the samples underwent a change from n- to p-type conduction, with an increase in mobility and a decrease in concentration for temperatures below 300K. Electrical measurements showed noticeable differences for both types of doped films when carried out in air or in vacuum. The results are discussed in terms of both the presence of surface conducting channels and the influence of photoconductive effects.

  5. Implementation of a Coherent Anti-Stokes Raman Scattering (CARS) System on a Ti:Sapphire and OPO Laser Based Standard Laser Scanning Microscope.

    Science.gov (United States)

    Mytskaniuk, Vasyl; Bardin, Fabrice; Boukhaddaoui, Hassan; Rigneault, Herve; Tricaud, Nicolas

    2016-07-17

    Laser scanning microscopes combining a femtosecond Ti:sapphire laser and an optical parametric oscillator (OPO) to duplicate the laser line have become available for biologists. These systems are primarily designed for multi-channel two-photon fluorescence microscopy. However, without any modification, complementary non-linear optical microscopy such as second-harmonic generation (SHG) or third harmonic generation (THG) can also be performed with this set-up, allowing label-free imaging of structured molecules or aqueous medium-lipid interfaces. These techniques are well suited for in-vivo observation, but are limited in chemical specificity. Chemically selective imaging can be obtained from inherent vibration signals based on Raman scattering. Confocal Raman microscopy provides 3D spatial resolution, but it requires high average power and long acquisition time. To overcome these difficulties, recent advances in laser technology have permitted the development of nonlinear optical vibrational microscopy, in particular coherent anti-Stokes Raman scattering (CARS). CARS microscopy has therefore emerged as a powerful tool for biological and live cell imaging, by chemically mapping lipids (via C-H stretch vibration), water (via O-H stretch vibrations), proteins or DNA. In this work, we describe the implementation of the CARS technique on a standard OPO-coupled multiphoton laser scanning microscope. It is based on the in-time synchronization of the two laser lines by adjusting the length of one of the laser beam path. We present a step-by-step implementation of this technique on an existing multiphoton system. A basic background in experimental optics is helpful and the presented system does not require expensive supplementary equipment. We also illustrate CARS imaging obtained on myelin sheaths of sciatic nerve of rodent, and we show that this imaging can be performed simultaneously with other nonlinear optical imaging, such as standard two-photon fluorescence technique

  6. High-sensitivity β-Ga_2O_3 solar-blind photodetector on high-temperature pretreated c-plane sapphire substrate

    KAUST Repository

    Qian, Ling-Xuan

    2017-09-20

    Recently, monoclinic Ga2O3 (beta-Ga2O3) photodetectors (PDs) have been extensively studied for various commercial and military applications due to the merits of intrinsic solar rejection, high gain, and great compactness. In this work, c-plane sapphire substrates were annealed under different temperatures in a vacuum furnace prior to the molecular beam epitaxy (MBE) of beta-Ga2O3 thin film, which yielded a smoother surface and even a terraceand- step-like morphology on the substrate, resulting in improved crystallinity of the epitaxial film. Accordingly, both the dark and photo currents of beta-Ga2O3 metal-semiconductor-metal (MSM) PDs were increased by the enhanced carrier mobility (mu) of the more crystalline film. However, the substrate-annealing temperature must be sufficiently high to offset the rise of the dark current and thus achieve a remarkable improvement in the photodetection properties. As a result, the PD fabricated on the 1050 degrees C-annealed substrate exhibited extremely high sensitivity, for example, high responsivity (R) of 54.9 A/ W and large specific detectivity (D*) of 3.71 x 10(14) Jones. Both parameters were increased by one order of magnitude because of the combined effects of the dramatic increase in mu and the effective reduction in defect-related recombination centers. Nevertheless, the latter also prolonged the recovery time of the PD. These findings suggest another way to develop beta-Ga2O3 PD with extremely high sensitivity. (C) 2017 Optical Society of America

  7. High electron mobility and low carrier concentration of hydrothermally grown ZnO thin films on seeded a-plane sapphire at low temperature

    Science.gov (United States)

    Jayah, Nurul Azzyaty; Yahaya, Hafizal; Mahmood, Mohamad Rusop; Terasako, Tomoaki; Yasui, Kanji; Hashim, Abdul Manaf

    2015-01-01

    Hydrothermal zinc oxide (ZnO) thick films were successfully grown on the chemical vapor deposition (CVD)-grown thick ZnO seed layers on a-plane sapphire substrates using the aqueous solution of zinc nitrate dehydrate (Zn(NO3)2). The use of the CVD ZnO seed layers with the flat surfaces seems to be a key technique for obtaining thick films instead of vertically aligned nanostructures as reported in many literatures. All the hydrothermal ZnO layers showed the large grains with hexagonal end facets and were highly oriented towards the c-axis direction. Photoluminescence (PL) spectra of the hydrothermal layers were composed of the ultraviolet (UV) emission (370 to 380 nm) and the visible emission (481 to 491 nm), and the intensity ratio of the former emission ( I UV) to the latter emission ( I VIS) changed, depending on both the molarity of the solution and temperature. It is surprising that all the Hall mobilities for the hydrothermal ZnO layers were significantly larger than those for their corresponding CVD seed films. It was also found that, for the hydrothermal films grown at 70°C to 90°C, the molarity dependences of I UV/ I VIS resembled those of mobilities, implying that the mobility in the film is affected by the structural defects. The highest mobility of 166 cm2/Vs was achieved on the hydrothermal film with the carrier concentration of 1.65 × 1017 cm-3 grown from the aqueous solution of 40 mM at 70°C.

  8. Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001 by the systematic control of composition, annealing temperature and time.

    Directory of Open Access Journals (Sweden)

    Puran Pandey

    Full Text Available Multi-metallic alloy nanoparticles (NPs can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25 hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

  9. Comparative study of GaN-based ultraviolet LEDs grown on different-sized patterned sapphire substrates with sputtered AlN nucleation layer

    Science.gov (United States)

    Zhou, Shengjun; Hu, Hongpo; Liu, Xingtong; Liu, Mengling; Ding, Xinghuo; Gui, Chengqun; Liu, Sheng; Guo, L. Jay

    2017-11-01

    GaN-based ultraviolet-light-emitting diodes (UV LEDs) with 375 nm emission were grown on different-sized patterned sapphire substrates (PSSs) with ex situ 15-nm-thick sputtered AlN nucleation layers by metal-organic chemical vapor deposition (MOCVD). It was observed through in situ optical reflectance monitoring that the transition time from a three-dimensional (3D) island to a two-dimensional (2D) coalescence was prolonged when GaN was grown on a larger PSS, owing to a much longer lateral growth time of GaN. The full widths at half-maximum (FWHMs) of symmetric GaN(002) and asymmetric GaN(102) X-ray diffraction (XRD) rocking curves decreased as the PSS size increased. By cross-sectional transmission electron microscopy (TEM) analysis, it was found that the threading dislocation (TD) density in UV LEDs decreased with increasing pattern size and fill factor of the PSS, thereby resulting in a marked improvement in internal quantum efficiency (IQE). Finite-difference time-domain (FDTD) simulations quantitatively demonstrated a progressive decrease in light extraction efficiency (LEE) as the PSS size increased. However, owing to the significantly reduced TD density in InGaN/AlInGaN multiple quantum wells (MQWs) and thus improved IQE, the light output power of the UV LED grown on a large PSS with a fill factor of 0.71 was 131.8% higher than that of the UV LED grown on a small PSS with a fill factor of 0.4, albeit the UV LED grown on a large PSS exhibited a much lower LEE.

  10. Metamorphic Al0.5Ga0.5N:Si on AlN/sapphire for the growth of UVB LEDs

    Science.gov (United States)

    Enslin, Johannes; Mehnke, Frank; Mogilatenko, Anna; Bellmann, Konrad; Guttmann, Martin; Kuhn, Christian; Rass, Jens; Lobo-Ploch, Neysha; Wernicke, Tim; Weyers, Markus; Kneissl, Michael

    2017-04-01

    In this paper we investigate the growth of metamorphic Al0.5Ga0.5 N :Si on c-plane AlN/sapphire. The structural properties of the AlGaN:Si pseudo substrates and the electro-optical characteristics of subsequently grown UVB LEDs are being examined. We demonstrate, that superlattices allow the controlled strain relaxation of Al0.5Ga0.5 N by rearrangement of threading dislocations, thus preventing the formation of cracks. This study investigates AlN/GaN superlattices with a nominal GaN layer thickness between 1.0 nm and 2.5 nm at a fixed AlN layer thickness of 2.5 nm. The number of superlattice-periods was also varied between 20 and 120. It was found that beyond a GaN layer thickness of 1.5 nm three-dimensional structures are formed. Additionally, these three-dimensional structures reduce the local defect density of the subsequently grown Al0.5Ga0.5 N layer. Although the Al0.5Ga0.5 N layer appears to be almost fully relaxed, the relaxation state of this pseudo substrate, was found to be dependent on the GaN layer thickness in the superlattice. After optimizing the superlattice structure we were able to grow crack free 4 μm thick Si-doped Al0.5Ga0.5 N layers and on top UVB LEDs with a fully strained active region emitting at 310 nm with output powers of more than 18 mW at 500 mA.

  11. Scale-up of the chemical lift-off of (In)GaN-based p-i-n junctions from sapphire substrates using sacrificial ZnO template layers

    Science.gov (United States)

    Rogers, D. J.; Sundaram, S.; El Gmili, Y.; Teherani, F. Hosseini; Bove, P.; Sandana, V.; Voss, P. L.; Ougazzaden, A.; Rajan, A.; Prior, K. A.; McClintock, R.; Razeghi, M.

    2014-03-01

    (In)GaN p-i-n structures were grown by MOVPE on both GaN- and ZnO-coated c-sapphire substrates. XRD studies of the as-grown layers revealed that a strongly c-axis oriented wurtzite crystal structure was obtained on both templates and that there was a slight compressive strain in the ZnO underlayer which increased after GaN overgrowth. The InGaN peak position gave an estimate of 13.6at% for the indium content in the active layer. SEM and AFM revealed that the top surface morphologies were similar for both substrates, with an RMS roughness (5 μm x 5 μm) of about 10 nm. Granularity appeared slightly coarser (40nm for the device grown on ZnO vs 30nm for the device grown on the GaN template) however. CL revealed a weaker GaN near band edge UV emission peak and a stronger broad defect-related visible emission band for the structure grown on the GaN template. Only a strong ZnO NBE UV emission was observed for the sample grown on the ZnO template. Quarter-wafer chemical lift-off (CLO) of the InGaN-based p-i-n structures from the sapphire substrate was achieved by temporary-bonding the GaN surface to rigid glass support with wax and then selectively dissolving the ZnO in 0.1M HCl. XRD studies revealed that the epitaxial nature and strong preferential c-axis orientation of the layers had been maintained after lift-off. This demonstration of CLO scale-up, without compromising the crystallographic integrity of the (In)GaN p-i-n structure opens up the perspective of transferring GaN based devices off of sapphire substrates industrially.

  12. Lattice dynamics and dielectric functions of multiferroic BiFeO{sub 3}/c-sapphire films determined by infrared reflectance spectra and temperature-dependent Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Zhihua; Yu, Qian [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Wu, Jiada; Sun, Jian [Key Laboratory for Advanced Photonic Materials and Devices, Ministry of Education, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Hu, Zhigao, E-mail: zghu@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Chu, Junhao [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)

    2012-12-15

    Multiferroic BiFeO{sub 3} (BFO) films have been grown on c-sapphire substrates by pulsed laser deposition under different laser energies (E{sub L}). The X-ray diffraction and Raman spectra indicate that the films are polycrystalline and exhibit the single rhombohedral (R) phase. The crystal distortion becomes weaker with decreasing the E{sub L}, which is described by the ratio of c/a. It was found that different E{sub L} values also lead to the variation of the Bi/Fe ratio. Temperature-dependent Raman spectra were carried out to study the phonon mode evolution behaviors. The three A{sub 1} transverse optical (TO) phonon modes located at 219, 172, and 142 cm{sup -1} shift towards a lower energy side with the temperature due to thermal expansion, thermal disorder and the anharmonic effects of lattice. The E(TO) and three A{sub 1}(TO) phonon frequencies slightly increase with increasing the E{sub L} of the growth condition, which results from the Bi vacancies, the changes of the length and intensity of Bi-O bonds and the local structure distortion in the FeO{sub 6} octahedra. The dielectric functions of the BFO films in the frequency range of 50-8000 cm{sup -1} have been extracted by fitting infrared reflectance spectra with the Lorentz multi-oscillator dispersion model. The variation trend of the dielectric functions with different E{sub L} can be observed and related to the packing density, surface roughness, and defect states. It was concluded that the E{sub L} corresponding to changing the c/a ratio has an obvious influence on the lattice vibrations and intraband transitions of the BFO films. - Highlights: Black-Right-Pointing-Pointer The c/a and Bi/Fe ratios of BiFeO{sub 3} films at different laser energy (E{sub L}). Black-Right-Pointing-Pointer The temperature-dependent evolution of phonon modes. Black-Right-Pointing-Pointer The crystal distortion and Bi vacancies influence the lattice vibration. Black-Right-Pointing-Pointer The E{sub L} effect on the dielectric

  13. MOCVD growth of N-polar GaN on on-axis sapphire substrate: Impact of AlN nucleation layer on GaN surface hillock density

    Science.gov (United States)

    Marini, Jonathan; Leathersich, Jeffrey; Mahaboob, Isra; Bulmer, John; Newman, Neil; (Shadi) Shahedipour-Sandvik, F.

    2016-05-01

    We report on the impact of growth conditions on surface hillock density of N-polar GaN grown on nominally on-axis (0001) sapphire substrate by metal organic chemical vapor deposition (MOCVD). Large reduction in hillock density was achieved by implementation of an optimized high temperature AlN nucleation layer and use of indium surfactant in GaN overgrowth. A reduction by more than a factor of five in hillock density from 1000 to 170 hillocks/cm-2 was achieved as a result. Crystal quality and surface morphology of the resultant GaN films were characterized by high resolution x-ray diffraction and atomic force microscopy and found to be relatively unaffected by the buffer conditions. It is also shown that the density of smaller surface features is unaffected by AlN buffer conditions.

  14. Orientation of FePt nanoparticles on top of a-SiO2/Si(001, MgO(001 and sapphire(0001: effect of thermal treatments and influence of substrate and particle size

    Directory of Open Access Journals (Sweden)

    Martin Schilling

    2016-04-01

    Full Text Available Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001, i.e., Si(001 with an amorphous (a- native oxide layer on top, on MgO(001, and on sapphire(0001 substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: “small” NPs with diameters in the range of 2–3 nm and “large” ones in the range of 5–8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD, served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001 supports, however, FePt nanoparticles exhibit a clearly preferred (111 orientation even in the as-prepared state, which can be slightly improved by annealing at 600–650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111 orientation. On top of MgO(001 the

  15. Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Claudel, A., E-mail: arnaud.claudel@grenoble-inp.org [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Fellmann, V. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Gélard, I. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Coudurier, N. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Sauvage, D. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Balaji, M. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Crystal Growth Center, Anna University, Chennai 600025 (India); and others

    2014-12-31

    Thin (0001) epitaxial aluminum nitride (AlN) layers were grown on c-plane sapphire using high temperature hydride vapor phase epitaxy. The experimental set-up consists of a vertical cold-wall quartz reactor working at low pressure in which the reactions take place on a susceptor heated by induction. The reactants used are ammonia and aluminum chlorides in situ formed via hydrogen chloride reaction with high purity aluminum pellets. As-grown AlN layers have been characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence and Raman spectroscopies. The influence of the V/III ratio in the gas phase, from 1.5 to 15, on growth rate, surface morphology, roughness and crystalline quality is investigated in order to increase the quality of thin epitaxial AlN layers grown at high temperature. Typical growth rates of around 0.45 μm/h were obtained for such thin epitaxial AlN layers. The growth rate was unaffected by the V/III ratio. An optimum for roughness, crystalline quality and optical properties seems to exist at V/III = 7.5. As a matter of fact, for a V/III ratio of 7.5, best root mean square roughness and crystalline quality — measured on 0002 symmetric reflection — as low as 6.9 nm and 898 arcsec were obtained, respectively. - Highlights: • Growth of thin epitaxial AlN layers by high temperature hydride vapor phase epitaxy • Influence of V/III ratio on growth rate, morphology and crystalline quality • The effect of surface morphology on strain state and crystal quality is established.

  16. Comparison of platelet counts by CellDyn Sapphire (Abbot Diagnostics), LH750 (Beckman Coulter), ReaPanThrombo immunoplatelet method (ReaMetrix), and the international flow reference method, in thrombocytopenic blood samples.

    Science.gov (United States)

    Sehgal, Kunal; Badrinath, Y; Tembhare, Prashant; Subramanian, P G; Talole, Sanjay; Kumar, Ashok; Gadage, Vijaya; Mahadik, Shashikant; Ghogale, Sitaram; Gujral, Sumeet

    2010-07-01

    We compared the international flow reference method (IRM) platelet counts with those obtained from CellDyn Sapphire (impedance and optical counts), LH750 (impedance counts), and the flowcytometry based ReaPanThrombo Immunoplatelet method (ReaMetrix). We further evaluated the degree of agreement of above methods with the IRM at the transfusion thresholds of 10 x 10(9) l(-1) and 20 x 10(9) l(-1). A total of 104 thrombocytopenic blood samples with platelet count of <50 x 10(9) l(-1) were selected for the study. All samples were tested in parallel by various methods within 6 h of blood collection. For bias estimation, a Bland-Altman analysis was done by taking the IRM as the standard method. The bias for CDS-I counts was +6.505 x 10(9) l(-1) (95% LA -2.110 to +15.122), for CDS-O counts the bias was -3.779 x 10(9) l(-1) (95% LA -8.950 to +1.392), for LH750 the bias was +0.111 x 10(9) l(-1) (95% LA -5.862 to +6.084) and that for ReaMetrix was -1.602 x 10(9) l(-1) (95% LA -7.400 to +4.194). The LH750 had the least average bias and it overestimated platelet counts marginally. The ReaMetrix method showed the highest degree of agreement with the IRM, at both the threshold points with a K value of 0.960 (threshold < or = 10 x 10(9) l(-1)) and 0.923 (threshold < or = 20 x 10(9) l(-1)). Impedance platelet counts from LH750 were more accurate than optical methods in thrombocytopenic patients. ReaMetrix immunoplatelet counts show the maximum degree of agreement with the IRM at clinically relevant transfusion thresholds. We conclude that as current platelet transfusion thresholds are based on results of automated hematology analyzer methods, the true thresholds may be determined using the IRM and CD41/61 based single-platform immunoplatelet methods. (c) 2010 Clinical Cytometry Society.

  17. Sextant of Sapphires for Molar Distalization.

    Science.gov (United States)

    Ponnada, Swaroopa Rani; Palla, Yudistar Venkata; Ganugapanta, Vivek Reddy

    2016-08-01

    Space analysis quantifies the amount of crowding within the arches estimating the severity of space discrepancy. The space gaining procedures include extraction and non-extraction procedures like expansion, proximal stripping and molar distalization. To identify features seen in molar distalization cases. The sample size comprised 20 patients in whom molar distalization was decided as the treatment plan. The study models and lateral cephalograms of all the patients were taken. Occlusograms were obtained. Model analysis and cephalometric analysis were performed. Descriptive statistical analysis like mean, standard deviation, standard error and mode were done. The parameters in Question gave following results. The Bolton analysis showed anterior mandibular excess with mean value of 1.56mm±1.07. The first order discrepancy between maxillary central and lateral incisors was 5±1.95. The premolar rotation showed mean value of 16.58±5.12. The molar rotation showed the value of 7.66±2.26. The nasolabial angle showed the mean of 101.25±8.7 IMPA of 101.4±5.74. The six features studied in molar distalization cases [First order discrepancy between upper central and lateral incisors; Rotation of premolars and molars; Bolton's discrepancy in anterior dentition; Average to horizontal growth pattern; Proclined lower incisors and Obtuse nasolabial angle] can be taken as patterns seen in molar distalization cases and considered as a valid treatment plan.

  18. Sapphire Multiple Filament and Large Plate Growth Processes

    Science.gov (United States)

    1972-10-01

    the setup by focusing its objective lens onto the detector. Focusing is accomplished by the operator sighting through the eyepiece in the back of...filament. The coating can be burned off or removed with a solvent (MEK) and the original diameter of the filament measured to arrive at the coating...temperature slightly above the normal operating temperature. Considerable smoke will be produced as the impurities burn off, and the absence of smoke can be

  19. Multiphoton tomography with tunable Ti:sapphire laser (Conference Presentation)

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans G.; Li, Tuan; König, Karsten

    2016-03-01

    Femtosecond near infrared laser microscopes are widely used to perform high resolution 3D imaging of biological samples based on second harmonic generation (SHG) and non-resonant simultaneous absorption of two or more photons at GW/cm2 intensities. However, high contrast imaging of living specimens without any destructive effect is limited to certain laser and exposure parameters with respect to the optical properties of the target. We compared three different femtosecond lasers, including a novel ultra-compact ultrashort fiber laser, in the range of 15-180 fs and repetition rates of 50-300 MHz for optimal non-destructive two-photon autofluorescence imaging. In particular we determined the thresholds for the onset of photodamage effects such as impaired cell reproduction.

  20. Interface defects in GaN/sapphire studied using Rutherford ...

    Indian Academy of Sciences (India)

    (MRS, Pittsburgh, USA, 1995). [5] C Cohen, J A Davies, A V Drigo and T E Jackman, Nucl. Instrum. Methods 218,. 147 (1983). [6] M Berti, A Carnera and A Sambo, unpublished. [7] M Lomascolo, G Tretta, A Passaseo, M Longo, D Cannoletta, R Cingolani,. A Bonifiglio, F Della Sals, A Di Carlo, P Lugli, M Natali, S K Sinha, ...

  1. Hybrid Quantum Cascade Lasers on Silicon-on-Sapphire

    Science.gov (United States)

    2016-11-23

    in COMSOL Multiphysics. Figure 4. Simulated efficiency of light coupling from the QCL ridge-waveguide to the SOS ridge waveguide, based on the...Calculations are performed in COMSOL Multiphysics. Fig. 4. Simulated efficiency of light coupling from the QCL ridge-waveguide to the SOS

  2. Laser produced nanocavities in silica and sapphire: a parametric study

    Energy Technology Data Exchange (ETDEWEB)

    Hallo, L; Travaille, G; Tikhonchuk, V T; Breil, J [CELIA, Universite Bordeaux I, 351 cours de la Liberation, 33405 Talence (France); Bourgeade, A [CEA - CESTA, BP 2, 3334 Le Barp (France); Nkonga, B [MAB, Universite Bordeaux I, 351 cours de la Liberation, 33405 Talence (France)

    2008-05-15

    We present a model, that describes a sub-micron cavity formation in a transparent dielectric under a tight focusing of a ultra-short laser pulse. The model solves the full set of Maxwell's equations in the three-dimensional geometry along with non-linear propagation phenomenons. This allows us to initialize hydrodynamic simulations of the sub-micron cavity formation. Cavity characteristics, which depend on 3D energy release and non linear effects, have been investigated and compared with experimental results. For this work, we want to deeply acknowledge the numerical support provided by the CEA Centre de Calcul Recherche et Technologie, whose help guaranteed the achievement of this study.

  3. Protons and deuterons in magnesium-doped sapphire crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, R.; Gonzalez, R.; Colera, I. [Univ. Carlos III de Madrid, Leganes (Spain). Dept. de Fisica; Vila, R. [CIEMAT, Madrid (Spain). Inst. de Investigacion Basica

    1997-04-01

    Of great importance to the use of ceramics in fusion reactors are the problems associated with the presence of a high level of transmutation products induced by high-energy neutrons. For aluminum oxide, the four major products are magnesium, hydrogen, carbon, and helium. The solubility and diffusivity of hydrogen isotopes strongly depend on the concentration of specific impurities, which results in a change in the position and full-width-at-half-maximum of the OH{sup {minus}} and OD{sup {minus}} bands. The OH{sup {minus}} and OD{sup {minus}} stretching frequencies in magnesium-doped aluminum oxide crystals were determined by infrared absorption measurements. Two very broad bands centered at {approximately}3,005 and 2,228 cm{sup {minus}1} were observed for OH{sup {minus}} and OD{sup {minus}}, respectively. Polarization experiment results were compatible with OH{sup {minus}} (OD{sup {minus}}) ions lying in the basal plane, as is the case in undoped crystals. The threshold temperature for the in-diffusion of deuterons was obtained by annealing the samples in flowing D{sub 2}O vapor; the resulting value was {approximately}1,050 K. At 1223 K, the diffusion coefficient was {approximately}3 {times} 10{sup {minus}7} cm{sup 2}/s, and the activation energy was 1.6 eV.

  4. Giant secondary grain growth in Cu films on sapphire

    Directory of Open Access Journals (Sweden)

    David L. Miller

    2013-08-01

    Full Text Available Single crystal metal films on insulating substrates are attractive for microelectronics and other applications, but they are difficult to achieve on macroscopic length scales. The conventional approach to obtaining such films is epitaxial growth at high temperature using slow deposition in ultrahigh vacuum conditions. Here we describe a different approach that is both simpler to implement and produces superior results: sputter deposition at modest temperatures followed by annealing to induce secondary grain growth. We show that polycrystalline as-deposited Cu on α-Al2O3(0001 can be transformed into Cu(111 with centimeter-sized grains. Employing optical microscopy, x-ray diffraction, and electron backscatter diffraction to characterize the films before and after annealing, we find a particular as-deposited grain structure that promotes the growth of giant grains upon annealing. To demonstrate one potential application of such films, we grow graphene by chemical vapor deposition on wafers of annealed Cu and obtain epitaxial graphene grains of 0.2 mm diameter.

  5. Design for a compact tunable Ti:sapphire laser

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, C.; Vuletic, V.; Hemmerich, A.; Ricci, L.; Haensch, T.W. [Sektion Physik der Universitaet Muenchen, 80799 Muenchen (Germany)

    1995-02-01

    Tunable laser radiation with megahertz linewidth is generated with a simple, inexpensive, and compact laser system that uses two common microscope slides as the only intracavity tuning elements. The laser emits two radiation modes whose frequencies are separated by 1.2 GHz, corresponding to the free spectral range of the laser resonator. The frequencies may be rapidly varied over a range of 1.5 GHz at a rate of 2 GHz/s.

  6. Epitaxial Titanium Nitride on Sapphire: Effects of Substrate Temperature on Microstructure and Optical Properties (Preprint)

    Science.gov (United States)

    2017-12-20

    between ion energy, ion-neutral flux ratio, and average energy deposited is determined from the following figure of merit.Error! Bookmark not defined...Error! Bookmark not defined. < >= ( ) [1] 2 Distribution A. Approved for public release (PA...temperatures—despite previous thermal change—furthering reliability of TiN as a plasmonic material. Error! Bookmark not defined. (a) (b) (c) (d) (e) (f) 6

  7. Mode-coupling enhancement by pump astigmatism correction in a Ti:Sapphire femtosecond laser.

    Science.gov (United States)

    Ramírez-Guerra, Catalina; Moreno-Larios, José Agustín; Rosete-Aguilar, Martha; Garduño-Mejía, Jesús

    2016-12-01

    To pump a solid-state femtosecond laser cavity, a beam from a CW laser is focused by a single lens into the laser crystal. To increase the output power of the laser, the overlap of the laser mode with the pump mode should be maximized. This is particularly important in the so-called mode coupling and the Kerr-lens mode locking (KLM) operation, where the change in beam waist at the position of the gain medium is exploited to enhance the mode overlap with the pump laser in the crystal. In this paper, the astigmatism in the pump beam is reduced by tilting the pump lens. A Gaussian beam is propagated through the complete focusing system-pump lens, tilted spherical mirror, and crystal cut at Brewster's angle-to show the astigmatism inside the crystal as a function of the tilt of the pump lens. A genetic algorithm is presented to optimize the mode coupling between the pump and laser beam inside the crystal by tilting the pump lens. Experimental results are presented to verify the design, showing an increase in the output power of the laser cavity of about 20%.

  8. Manipulating the optical properties of dual implanted Au and Zn nanoparticles in sapphire

    Science.gov (United States)

    Epie, E. N.; Scott, D.; Chu, W. K.

    2017-11-01

    We have synthesized and manipulated the optical properties of metallic nanoparticles (NPs) by using a combination of low-energy high-fluence dual implantation and thermal annealing. We demonstrated that by implanting Zn before Au, the resulting absorption peak is enormously blue-shifted by 120 nm with respect to that of Au-only implanted samples. This magnitude of optical shift is not characteristic of unalloyed Au and to the best of our knowledge cannot be attributed to NP size change alone. On the other hand, the absorption peak for samples implanted with Au followed by Zn is blue-shifted about 20 nm. Additionally, by carefully annealing all implanted samples, both NP size distribution and corresponding optical properties can be further modified in a controlled manner. We attribute these behaviours to nanoalloy formation. This work provides a direct method for synthesizing and manipulating both the plasmonic and structural properties of metallic alloy NP in various transparent dielectrics for diverse applications.

  9. A scalable pathway to nanostructured sapphire optical fiber for evanescent-field sensing and beyond

    Czech Academy of Sciences Publication Activity Database

    Chen, H.; Tian, F.; Kaňka, Jiří; Du, H.

    2015-01-01

    Roč. 106, č. 11 (2015), s. 1111021-1111025 ISSN 0003-6951 R&D Projects: GA MŠk(CZ) LH11038 Institutional support: RVO:67985882 Keywords : Aluminum coating s * Nano-structured * Silver nanoparticles Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.142, year: 2015

  10. Sapphire Optical Fiber Sensors for Structural Performance Testing up to 3000 F Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development and performance evaluation of new carbon/carbon (C/C) and carbon/silicon-carbide (SiC) composite structural components has been hampered by the lack...

  11. Current developments with TRIUMF’s titanium-sapphire laser based resonance ionization laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Lassen, J., E-mail: LASSEN@triumf.ca; Li, R. [TRIUMF (Canada); Raeder, S. [GSI Helmholtzzentrum für Schwerionenforschung GmbH (Germany); Zhao, X.; Dekker, T. [TRIUMF (Canada); Heggen, H. [GSI Helmholtzzentrum für Schwerionenforschung GmbH (Germany); Kunz, P.; Levy, C. D. P.; Mostanmand, M.; Teigelhöfer, A.; Ames, F. [TRIUMF (Canada)

    2017-11-15

    Developments at TRIUMF’s isotope separator and accelerator (ISAC) resonance ionization laser ion source (RILIS) in the past years have concentrated on increased reliability for on-line beam delivery of radioactive isotopes to experiments, as well as increasing the number of elements available through resonance ionization and searching for ionization schemes with improved efficiency. The current status of these developments is given with a list of two step laser ionization schemes implemented recently.

  12. Waveguiding thin Y2O3 films grown on sapphire substrates

    NARCIS (Netherlands)

    Kuzminykh, Y.; Bär, S.; Scheife, H.; Huber, G.; Apostolopoulos, V.; Pollnau, Markus

    Thin crystalline and amorphous yttria films have been produced using pulsed laser deposition and electron beam evaporation methods. Planar waveguiding in amorphous yttria films produced by electron beam evaporation has been demonstrated.

  13. Waveguiding thin Y2O3 films grown on sapphire substrates

    OpenAIRE

    Kuzminykh, Y.; Bär, S.; Scheife, H.; Huber, G; Apostolopoulos, V.; Pollnau, Markus

    2004-01-01

    Thin crystalline and amorphous yttria films have been produced using pulsed laser deposition and electron beam evaporation methods. Planar waveguiding in amorphous yttria films produced by electron beam evaporation has been demonstrated.

  14. Reduction in thermal boundary conductance due to proton implantation in silicon and sapphire

    Science.gov (United States)

    Hopkins, Patrick E.; Hattar, Khalid; Beechem, Thomas; Ihlefeld, Jon F.; Medlin, Douglas L.; Piekos, Edward S.

    2011-06-01

    We measure the thermal boundary conductance across Al/Si and Al/Al2O3 interfaces that are subjected to varying doses of proton ion implantation with time domain thermoreflectance. The proton irradiation creates a major reduction in the thermal boundary conductance that is much greater than the corresponding decrease in the thermal conductivities of both the Si and Al2O3 substrates into which the ions were implanted. Specifically, the thermal boundary conductances decrease by over an order of magnitude, indicating that proton irradiation presents a unique method to systematically decrease the thermal boundary conductance at solid interfaces.

  15. Current developments with TRIUMF's titanium-sapphire laser based resonance ionization laser ion source. An overview

    Science.gov (United States)

    Lassen, J.; Li, R.; Raeder, S.; Zhao, X.; Dekker, T.; Heggen, H.; Kunz, P.; P. Levy, C. D.; Mostanmand, M.; Teigelhöfer, A.; Ames, F.

    2017-11-01

    Developments at TRIUMF's isotope separator and accelerator (ISAC) resonance ionization laser ion source (RILIS) in the past years have concentrated on increased reliability for on-line beam delivery of radioactive isotopes to experiments, as well as increasing the number of elements available through resonance ionization and searching for ionization schemes with improved efficiency. The current status of these developments is given with a list of two step laser ionization schemes implemented recently.

  16. On the design of GaN vertical MESFETs on commercial LED sapphire wafers

    Science.gov (United States)

    Atalla, Mahmoud R. M.; Noor Elahi, Asim M.; Mo, Chen; Jiang, Zhenyu; Liu, Jie; Ashok, S.; Xu, Jian

    2016-12-01

    Design of GaN-based vertical metal-semiconductor field-effect transistors (MESFETs) on commercial light-emitting-diode (LED) epi-wafers has been proposed and proof of principle devices have been fabricated. In order to better understand the IV curves, these devices have been simulated using the charge transport model. It was found that shrinking the drain pillar size would significantly help in reaching cut-off at much lower gate bias even at high carrier concentration of unintentionally doped GaN and considerable leakage current caused by the Schottky barrier lowering. The realization of these vertical MESFETs on LED wafers would allow their chip-level integration. This would open a way to many intelligent lighting applications like on-chip current regulator and signal regulation/communication in display technology.

  17. Hydrothermal Synthesis and Growth of Ti:Sapphire(Ti3+:Al2O3) Laser Crystals

    National Research Council Canada - National Science Library

    Bliss, David; Callahan, Michael; Wang, Buguo

    2007-01-01

    .... However, it is difficult to grow homogeneous crystals from the melt with uniform doping concentration because of the impurity segregation effect and more importantly, trivalent titanium instability...

  18. Silicon-on-Sapphire Waveguides: Mode-converting Couplers and Four-wave Mixing

    Science.gov (United States)

    2014-09-01

    and Engineering (NISE) Program at SSC Pacific funded this Basic Research project. This is a work of the United States Government and...masking step. Then they were coated with a 390-nm UV210 photoresist. The wafers were exposed in a Canon® FPA-3000 EX5 stepper at 280 J/m2. Using this... stepper at 180 J/m2. We also used PECVD to deposit SiN. The PECVD nitride deposited is not very stoichiometric (0.8 to 1.0:1 vs. 0.75:1 for thermal

  19. Analysis of an optical biosensor based on elastic light scattering from diamond-, glass-, and sapphire microspheres

    OpenAIRE

    Murib, Mohammed Sharif; Tran, Anh Quang; De Ceuninck, Ward; Schöning, J.M.; Nesladek, Milos; SERPENGÜZEL, Ali; Wagner, Patrick

    2012-01-01

    Deoxyribonucleic acid (DNA) and protein recognition are now standard tools in biology. In addition, the special optical properties of microsphere resonators expressed by the high quality factor (Q-factor) of whispering gallery modes (WGMs) or morphology dependent resonances (MDRs) have attracted the attention of the biophotonic community. Microsphere-based biosensors are considered as powerful candidates to achieve label-free recognition of single molecules due to the high sensitivity of thei...

  20. GaN grown on sapphire by MOCVD : material for HEMT structures

    NARCIS (Netherlands)

    Grzegorczyk, Andrzej Pawel

    2006-01-01

    This thesis focuses on growth and basic characterization of AlGaN/GaN based high electron mobility structures. In order to provide theoretical background for the presented research, the basic physical properties of III-V nitrides and the characteristics of the HEMT structures are discussed.

  1. Thermal Modeling of GaN HEMTs on Sapphire and Diamond

    National Research Council Canada - National Science Library

    Salm, III, Roman P

    2005-01-01

    Wide bandgap semiconductors have entered into Naval radar use and will eventually replace vacuum tube and conventional solid-state amplifiers for all modern military radar and communications applications. Gallium Nitride (GaN...

  2. White light continuum generation in sapphire using two-coloured femtosecond laser pulses

    OpenAIRE

    Čepėnas, Augustas

    2017-01-01

    A wide spectrum of laser radiation is useful for two reasons: wider spectrum allows generation of shorter laser pulses, meanwhile, in pump-probe spectroscopy it is prefered to cover the largest possible spectral range with the same source. This work explores white light continuum generation using two-colored (wavelength of 1030 nm and 515 nm) femtosecond laser pulses. Combining these two white light continuums should expand radiation spectrum. However, this research shows that white light con...

  3. Heat transfer in YBaCuO thin film/sapphire substrate system

    Energy Technology Data Exchange (ETDEWEB)

    Sergeev, A.; Semenov, A.; Trifonov, V.; Karasik, B.; Gol' tsman, G.; Gershenzon, E. (Moscow State Pedagogical Univ. (Russian Federation))

    1994-04-01

    The thermal boundary resistance at the YBaCuO thin film/Al[sub 2]O[sub 3] substrate interface was investigated. The transparency for thermal phonons incident on the interface as well as for phonons moving from the substrate was determined. We have measured a transient voltage response of current-biased films to continuously modulated radiation. The observed knee in the modulation frequency dependence of the response reflects the crossover from the diffusion regime to the contact resistance regime of the heat transfer across the interface. The values of transparency were independently deduced both from the phonon escape time and from the time of phonon return to the film which were identified with peculiarities in the frequency dependence. The results are much more consistent with the acoustic mismatch theory than the diffuse mismatch model. 11 refs., 2 figs.

  4. A Continuum Description of Nonlinear Elasticity, Slip and Twinning, With Application to Sapphire

    Science.gov (United States)

    2009-03-01

    Kalidindi 1998; Castaing et al. 2002; Wu et al. 2007). The theory is applicable over a potentially wide temperature range via dependence of initial...or confined compression (Graham & Brooks 1971; Castaing et al. 1981; Scott & Orr 1983; Lankford et al. 1998). Graham & Brooks (1971) suggested that... Castaing et al. 1981). However, in shock experiments, plastic strain rates are not constant, but ramp up from small values at the onset of yielding at

  5. High-order dispersion control of 10-petawatt Ti:sapphire laser facility.

    Science.gov (United States)

    Li, Shuai; Wang, Cheng; Liu, Yanqi; Xu, Yi; Li, Yanyan; Liu, Xingyan; Gan, Zebiao; Yu, Lianghong; Liang, Xiaoyan; Leng, Yuxin; Li, Ruxin

    2017-07-24

    A grism pair is utilized to control the high-order dispersion of the Shanghai Superintense Ultrafast Lasers Facility, which is a large-scale project aimed at delivering 10-PW laser pulses. We briefly present the characteristics of the laser system and calculate the cumulative B-integral, which determines the nonlinear phase shift influence on material dispersion. Three parameters are selected, grism separation, angle of incidence and slant distance of grating compressor, to determine their optimal values through an iterative searching procedure. Both the numerical and experimental results confirm that the spectral phase distortion is controlled, and the recompressed pulse with a duration of 24 fs is obtained in the single-shot mode. The distributions and stabilities of the pulse duration at different positions of the recompressed beam are also investigated. This approach offers a new feasible solution for the high-order dispersion compensation of femtosecond petawatt laser systems.

  6. Efficient energetic proton generation driven by ultrashort ultraintense ti:Sapphire laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Choi, I. W.; Kim, C. M.; Jeong, T. M.; Yu, T. J.; Sung, J. H.; Lee, S. K.; Hafz, N.; Pae, K. H.; Ko, D. K.; Lee, J. [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Nishiuchi, M.; Daido, H.; Yogo, A.; Orimo, S.; Ogura, K.; Ma, J.; Sagisaka, A.; Mori, M.; Pirozhkov, A. S.; Kiriyama, H.; Bulanov, S. V.; Esirkepov, T. Zh. [Japan Atomic Energy Agency, Kyoto (Japan); Oishi, Y.; Nemoto, K. [Central Research Institute of Electronic Power Industry, Kanagawa (Japan)

    2008-11-15

    Significant progress on laser driven proton generation has been made in the past few years. Proton acceleration driven by ultrashort ultraintense laser pulse has been a promising technology for realizing a compact accelerator. Laser driven protons have several unique properties, such as shot pulse duration of ∼ps, high peak current in kA range, low transverse emittance below 10{sup -}2{sup m}m mrad, and good laminarity. For practical applications, the proton beam should be optimized to obtain higher energy, narrower energy spread, larger number and conversion efficiency. Maximum proton energy of 58 MeV has been demonstrated using PW class laser pulse, and quasi monoenergetic protons were produced from microstructured target. We have performed series of experiments to generate energetic proton beam by collaborating with JAEA and CRIEPI groups. Energetic protons were produced by the interaction of ultrashort ultraintense laser pulse with thin solid targets. Laser pulse with maximum energy of 1.7 J and minimum pulse duration of 34 FS, giving maximum peak intensity 3x10{sup 1}9{sup W}/cm{sup 2,} was focused using an off axis parabolic mirror at 45 degree incident angle with p polarization. The target used was one of 5μm thick copper of 7.5, 12.5, 25μm thick polyimide foils. Fresh Surface of target was supplied by moving the target with tape target driver for every laser shot, performing repetitive laser shooting without breaking vacuum. In order to investigate optimal generation conditions, we varied the laser pulse width and changed target position with respect to a tight focus position of laser beam. Main proton diagnostic was proton time of flight spectrometer to facilitate real time optimization of the laser and target conditions. Energetic protons with maximum energy of up to 4 MeV are generated by the interaction of laser pulse with a 7.5μm thick Polyimide target. The conversion efficiency from the laser energy into the proton kinetic energies is achieved to be about 3%. Our result shows that the contrast of ASE plays one of the key issues for the efficient proton generation and that the polyimide target which is transparent to 800nm laser pulse might have some role for the efficient proton generation. Proton energy spectrum also shows a narrow band structure having a small energy spread with about 7% of its absolute value near 1.9 MeV.

  7. Second Breakdown Susceptibility of Silicon-On-Sapphire Diodes having Systematically Different Geometries.

    Science.gov (United States)

    1980-05-30

    transistor geometries (such as narrow base regions) and real doping profiles (graded junctions) and the need to treat the device as a whole became apparent...threshold using Eq. 9.10 is 2 s ,]/2 1- Esat = vs30 (9.13) Values of the constants of Eq. 9.13 for holes and for elections are given in Table 14. For fields...up to ( Esat ) for holes, the hole drift velocity, is given by Eq. 9.11a. For fields in excess of Esat for holes, the hole drift velocity is given by

  8. Reproductive behaviour and embryonic development of the Citrinis Clown Goby (Gobiodon citrinus and Blue Sapphire Damselfish (Chrysiptera springeri

    Directory of Open Access Journals (Sweden)

    João Chambel

    2014-06-01

    The development of captive breeding techniques for targeted aquaculture species requires a sound knowledge of their gamete physiology, embryology, and early larval ontogeny and this study provides for the first time technical information about breeding of G. citrinus and C. springeri and this can be a start point for the captive breeding of this species.

  9. Time-dependent analysis of a parametric lens detected with a 100-fs Ti:sapphire laser.

    Science.gov (United States)

    Toci, G; McGraw, D; Pini, R; Salimbeni, R; Vannini, M

    1995-07-15

    The second-order parametric lens effect shows a temporal limit as a saturable-absorber device for operation in the ultrafast time region. We present and discuss an extended theoretical model dealing with second-order cascaded processes in a nonstationary condition. Experimentally we report the detection of the time-averaged lens effect in the hundred-of-femtoseconds range, discussing the limits that arise in this ultrafast optical region.

  10. Pulsed laser deposition of epitaxial BeO thin films on sapphire and SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Peltier, Thomas; Takahashi, Ryota; Lippmaa, Mikk, E-mail: mlippmaa@issp.u-tokyo.ac.jp [Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 (Japan)

    2014-06-09

    Epitaxial beryllia thin films were grown by pulsed laser deposition on Al{sub 2}O{sub 3}(001) and SrTiO{sub 3}(111) substrates. Nearly relaxed epitaxial films were obtained on both substrates at growth temperatures of up to about 600 °C. Crystalline films with expanded lattice parameters were obtained even at room temperature. The maximum growth temperature was limited by a loss of beryllium from the film surface. The volatility of beryllium appeared to be caused by the slow oxidation kinetics at the film surface and the re-sputtering effect of high-energy Be and BeO species in the ablation plume. Time-of-flight plume composition analysis suggested that the target surface became Be metal rich at low oxygen pressures, reducing the growth rate of beryllia films.

  11. Appearance of large crystalline domains in VO{sub 2} films grown on sapphire (001) and their phase transition characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Azhan, Nurul Hanis; Su, Kui; Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp [Graduate School of Science and Technology, Tokai University, Hiratsuka 259-1292 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont 37200 Tours (France)

    2015-06-28

    We report the first observation of large crystalline domains of several μm-size in VO{sub 2} films deposited on Al{sub 2}O{sub 3} (001) substrates by rf-biased reactive sputtering technique. The large crystalline domains, dominated with random in-plane oriented growth of (011){sub M1}-orientation, appear only under adequate substrate biasing, such as 10 W, while most biasing conditions result in conventional nanosized grains of highly oriented (010){sub M1}-orientation. Two temperature-controlled analyses, x-ray diffraction and micro-Raman spectroscopy, have revealed that some parts of large crystalline domains undergo intermediate monoclinic (M2) phase during the thermally-induced structural phase transition from monoclinic (M1) to rutile-tetragonal (R) phase. As an effect of the appearance of large crystalline domains, the film showed in-plane tensile stress, resulting in high T{sub IMT} of 69 °C due to the elongation of the V-V distance in its low-temperature monoclinic phase.

  12. High-quality a-axis oriented EuBa 2Cu 3O 7- δ films on sapphire substrates

    Science.gov (United States)

    Wakana, Hironori; Michikami, Osamu

    2001-02-01

    The superconducting properties of a-axis oriented EuBa 2Cu 3O 7- δ (EBCO) films on Al 2O 3(1 1¯ 0 2) substrates with CeO 2 buffer layers have been improved by introducing a template layer of PrBa 2Cu 3O x (PBCO). The a-axis oriented PBCO films were grown epitaxially on 50 Å thick CeO 2(0 0 1) buffer layers using DC magnetron sputtering. The high-quality a-axis oriented PBCO films grew under sputtering conditions of a substrate temperature ( Ts) of 620°C and a deposition rate ( Rd) of 35 Å/min. The a-axis oriented EBCO films were grown on the a-axis oriented PBCO template layers above 700 Å in thickness. The high-quality a-axis oriented EBCO films were deposited on sapphire⧹CeO 2(0 0 1) with a-axis oriented 1000 Å thick PBCO template layers at Ts=650°C and exhibited Tc endpoints ( Tce) of about 86.7 K.

  13. Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

    Directory of Open Access Journals (Sweden)

    Ichiro Yonenaga

    2015-07-01

    Full Text Available The hardness of wurtzite indium nitride (α-InN films of 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation of crystalline quality by x-ray diffraction, the hardness and Young’s modulus were determined to be 8.8 ± 0.4 and 184 ± 5 GPa, respectively, for the In (0001- and N ( 000 1 ̄ -growth faces of InN films. The bulk and shear moduli were then derived to be 99 ± 3 and 77 ± 2 GPa, respectively. The Poisson’s ratio was evaluated to be 0.17 ± 0.03. The results were examined comprehensively in comparison with previously reported data of InN as well as those of other nitrides of aluminum nitride and gallium nitride. The underlying physical process determining the moduli and hardness was examined in terms of atomic bonding and dislocation energy of the nitrides and wurtzite zinc oxide.

  14. MOVPE deposition of Sb2Te3 and other phases of Sb-Te system on sapphire substrate

    Science.gov (United States)

    Kuznetsov, P. I.; Shchamkhalova, B. S.; Yapaskurt, V. O.; Shcherbakov, V. D.; Luzanov, V. A.; Yakushcheva, G. G.; Jitov, V. A.; Sizov, V. E.

    2017-08-01

    The films of Sb-Te system have been deposited by MOVPE on (0 0 0 1) Al2O3 substrates with thin ZnTe buffer layers at different temperatures and Te/Sb ratios in the vapor phase. X-ray diffractometry, SEM microscopy, Raman and EDX spectroscopy were used to study as-grown films. The surface morphology and stoichiometry of Sb-Te films strongly depend on Te/Sb ratio in vapor phase. We have deposited the phases of homologous series nSb2·mSb2Te3 with following stoichiometries: Sb2Te3, Sb4Te5, Sb8Te9, Sb10Te9, Sb4Te3, Sb2Te, Sb8Te3, Sb10Te3, Sb16Te3, Sb18Te3 and Sb. Transport properties of Sb2Te3, Sb4Te5, Sb8Te9, Sb4Te3, Sb2Te were evaluated using Van der Pauw technique at 300 K.

  15. Refraction measurements and modeling over the Chesapeake Bay during the NATO (TG-51) SAPPHIRE trials, June 2006

    NARCIS (Netherlands)

    Jong, A.N. de; Fritz, P.J.

    2007-01-01

    Optical refraction tends to occur frequently in the atmospheric boundary layer. Due to a gradient in the temperature as function of height, rays are bending down towards the earth (super-refraction), or up towards to the sky (sub-refraction). As a consequence, images of targets at long range may be

  16. Epitaxial growth of CuScO2 thin films on sapphire a-plane substrates by pulsed laser deposition

    Science.gov (United States)

    Kakehi, Yoshiharu; Satoh, Kazuo; Yotsuya, Tsutom; Nakao, Satoru; Yoshimura, Takeshi; Ashida, Atsushi; Fujimura, Norifumi

    2005-04-01

    An epitaxial film of CuScO2, a transparent oxide semiconductor with a delafossite structure, was grown on an α -Al2O3(112¯0) substrate by a pulsed laser deposition method using a single-phase Cu2Sc2Oδ target. A two-dimensional x-ray reciprocal space mapping measurement revealed that the film was single phase with a rhombohedral crystal structure. The film showed six-fold rotational symmetry in the basal plane, indicating that the film had a twinned domain structure. The epitaxial growth of CuScO2[3R](0001) thin films on α -Al2O3(112¯0) substrates is caused by the uniaxial locked epitaxy mechanism along the ⟨1¯21¯0⟩ direction of the film, and the orientation relationships of the film with respect to the substrate were CuScO2[3R](0001)//α-Al2O3(112¯0) and CuScO2[3R][1¯21¯0]//α-Al2O3[88¯01]. The optical transmittance of the film was larger than 65% in the visible/near-infrared regions, while the energy gap for direct allowed transition was estimated as 3.7 eV. The resistivity of the film, 9.3×106Ωcm at room temperature, significantly decreased to 4.0 Ωcm after both substituting Mg2+ ions for Sc3+ and intercalating excess oxygen. The Mg-doped CuScO2+X(0001) thin film showed optical transmittance of larger than 65% in the visible region, and the Seebeck coefficient was positive, indicating a p-type conductivity.

  17. UV Enhanced Oxygen Response Resistance Ratio of ZnO Prepared by Thermally Oxidized Zn on Sapphire Substrate

    Directory of Open Access Journals (Sweden)

    Cheng-Chang Yu

    2013-01-01

    Full Text Available ZnO thin film was fabricated by thermally oxidized Zn at 600°C for 1 h. A surface containing nanostructured dumbbell and lines was observed by scanning electron microscope (SEM. The ZnO resistor device was formed after the following Ti/Au metallization. The device resistance was characterized at different oxygen pressure environment in the dark and under ultraviolet (UV light illumination coming from the mercury lamp with a short pass filter. The resistance increases with the increase of oxygen pressure. The resistance decreases and response increases with the increase of light intensity. Models considering the barrier height variation caused by the adsorbed oxygen related species were used to explain these results. The UV light illumination technology shows an effective method to enhance the detection response for this ZnO resistor oxygen sensor.

  18. Thin Disk Ti:Sapphire amplifiers for Joule-class ultrashort pulses with high repetition rate (Conference Presentation)

    Science.gov (United States)

    Nagymihály, Roland S.; Cao, Huabao; Kalashnikov, Mikhail P.; Khodakovskiy, Nikita; Ehrentraut, Lutz; Osvay, Károly; Chvykov, Vladimir V.

    2017-05-01

    High peak power CPA laser systems can deliver now few petawatt pulses [1]. Reaching the high energies with broad spectral bandwidth necessary for these pulses was possible by the use of large aperture Ti:Sa crystals as final amplifier media. Wide applications for these systems will be possible if the repetition rate could be increased. Therefore, thermal deposition in Ti:Sa amplifiers is a key issue, which has to be solved in case of high average power pumping. The thin disk (TD) laser technology, which is intensively developed nowadays by using new laser materials, is able to overcome thermal distortions and damages of laser crystals [2]. TD technique also has the potential to be used in systems with both high peak and average power. For this, the commonly used laser materials with low absorption and emission cross sections, also low heat conductivity, like Yb:YAG, need to be replaced by a gain medium that supports broad enough emission spectrum and high thermal conductivity to obtain few tens of fs pulses with high repetition rates. Parasitic effects during the amplification process however seriously limit the energy that can be extracted from the gain medium and also they distort the gain profile. Nevertheless, the application of the Extraction During Pumping (EDP) technique can mitigate the depopulation losses in the gain medium with high aspect ratio [3]. We proposed to use Ti:Sa in combination with TD and EDP techniques to reach high energies at high repetition rates, and we presented numerical simulations for different amplifier geometries and parameters of the amplification [4,5]. We present the results of the proof-of-principle experiment, where a EDP-TD Ti:Sa amplifier was tested for the first time. In our experiment, the final cryogenically cooled Ti:Sa amplifier in a 100 TW/10 Hz/28 fs laser system was replaced with the EDP-TD room temperature cooled arrangement. Amplified seed pulse energy of 2.6 J was reached only for 3 passes through TD with 0.5 J of input seed and 5 J of absorbed pump energy. We verified the excellent heat extraction capabilities of our amplifier module. Results of the scaling simulations on the base of this experiment for 100s of TW peak power laser systems operating at up to 100 Hz will be also presented. References 1. Y. Chu et al, Opt. Lett. 40, 5011-5014 (2015). 2. C. R. E. Baer et al, Opt. Exp. 20, 7054-7065 (2012). 3. V. Chvykov et al, Opt. Comm. 285, 2134-2136 (2012). 4. V. Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Exp. 24, 3721 (2016). 5. V.Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Lett. 41,13, 3017 (2016).

  19. Growth, characterization, and application of well-defined separated GaN-based pyramid array on micropatterned sapphire substrate

    Science.gov (United States)

    Tian, Zhenhuan; Li, Yufeng; Su, Xilin; Feng, Lungang; Wang, Shuai; Zhang, Minyan; Ding, Wen; Li, Qiang; Zhang, Ye; Guo, Maofeng; Yun, Feng; Lee, S. W. Ricky

    2017-09-01

    We tried to obtain microstructures on a three-dimensional (3D) micropatterned substrate by laser drilling. The influences of the dimensions of the drilling holes on the morphology and the material quality of the grown structures were studied. Uniform micropyramid arrays with relatively low dislocation density can be achieved by adjusting the laser drilling parameters. The internal quantum efficiency was estimated to be improved by a factor of 3 for a pyramid structure compared with that of planar LEDs. We fabricated 5 × 7 mm2 flexible LEDs employing the pyramid structure and the devices exhibited good flexibility without performance reduction after bending.

  20. Indentation-Induced Mechanical Deformation Behaviors of AlN Thin Films Deposited on c-Plane Sapphire

    National Research Council Canada - National Science Library

    Sheng-Rui Jian; Jenh-Yih Juang

    2012-01-01

    ... and cross-sectional transmission electron microscopy (XTEM). The load-displacement curves show the "pop-ins" phenomena during nanoindentation loading, indicative of the formation of slip bands caused by the propagation of dislocations...

  1. Towards High-Mobility Heteroepitaxial -Ga2O3 on Sapphire Dependence of the Substrate off-Axis Angle (Preprint)

    Science.gov (United States)

    2017-07-06

    the Ga ion damage and to obtain electron transparency for high resolution imaging. TEM characterization of the film was performed using an...T. Oishi, Y. Koga, K. Harada, M. Kasu, Appl. Phys. Express 2015, 8, 031101. 3. T. C. Lovejoy, E. N. Yitamben, N. Shamir, J. Morales , E. G. Villora

  2. Zno Micro/Nanostructures Grown on Sapphire Substrates Using Low-Temperature Vapor-Trapped Thermal Chemical Vapor Deposition: Structural and Optical Properties

    Directory of Open Access Journals (Sweden)

    Po-Sheng Hu

    2017-12-01

    Full Text Available In this research, the Zn(C5H7O22·xH2O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N2/O2, of 500/500 Standard Cubic Centimeters per Minute (SCCM, and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD, photoluminescence (PL, and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002 and (101 as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL.

  3. Nanoscale selective area growth of thick, dense, uniform, In-rich, InGaN nanostructure arrays on GaN/sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, S. [Centre National de la Recherche Scientifique (CNRS), Metz (France); Puybaret, R. [Georgia Inst. of Technology, Metz (France); El Gmili, Y. [Centre National de la Recherche Scientifique (CNRS), Metz (France); Li, X. [Georgia Inst. of Technology, Metz (France); Bonanno, P. L. [Centre National de la Recherche Scientifique (CNRS), Metz (France); Pantzas, K. [Centre National de la Recherche Scientifique (CNRS), Marcoussis (France); Orsal, G. [Univ. of Lorraine, Metz (France); Troadec, D. [Univ. of Science and Technology, Lille (France); Cai, Z. -H. [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Patriarche, G. [Centre National de la Recherche Scientifique (CNRS), Marcoussis (France); Voss, P. L. [Georgia Inst. of Technology, Metz (France); Salvestrini, J. P. [Univ. of Lorraine, Metz (France); Ougazzaden, A. [Georgia Inst. of Technology, Metz (France)

    2014-10-28

    Uniform, dense, single-phase, 150 nm thick indium gallium nitride (InGaN) nanostructure (nanorods and nanostripes) arrays have been obtained on gallium nitride templates, by metal organic chemical vapor deposition and nanoscale selective area growth on silicon dioxide patterned masks. The 150 nm thick InGaN nanorods have a perfect hexagonal pyramid shape with relatively homogenous indium concentration up to 22%, which is almost twice as high as in planar InGaN grown in the same condition, and luminesce at 535 nm. InGaN nanostripes feature c-axis oriented InGaN in the core which is covered by InGaN grown along semi-polar facets with higher In content. Transmission electron microscope and sub micron beam X-rays diffraction investigations confirm that both InGaN nanostructures are mostly defect free and monocrystalline. The ability to grow defect-free thick InGaN nanostructures with reduced polarization and high indium incorporation offers a solution to develop high efficiency InGaN-based solar cells.

  4. Nanoscale selective area growth of thick, dense, uniform, In-rich, InGaN nanostructure arrays on GaN/sapphire template

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, S.; El Gmili, Y.; Bonanno, P. L. [CNRS, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Puybaret, R.; Li, X.; Voss, P. L.; Ougazzaden, A. [Georgia Institute of Technology, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Pantzas, K.; Patriarche, G. [CNRS, UPR LPN, Route de Nozay, 91460 Marcoussis (France); Orsal, G.; Salvestrini, J. P., E-mail: salvestr@metz.supelec.fr [Université de Lorraine, Supélec, LMOPS, EA4423, 57070 Metz (France); Troadec, D. [Université des Sciences et Technologies de Lille, CNRS, UMR 8520 IEMN, 59000 Lille (France); Cai, Z.-H. [Advanced Photon Source, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-10-28

    Uniform, dense, single-phase, 150 nm thick indium gallium nitride (InGaN) nanostructure (nanorods and nanostripes) arrays have been obtained on gallium nitride templates, by metal organic chemical vapor deposition and nanoscale selective area growth on silicon dioxide patterned masks. The 150 nm thick InGaN nanorods have a perfect hexagonal pyramid shape with relatively homogenous indium concentration up to 22%, which is almost twice as high as in planar InGaN grown in the same condition, and luminesce at 535 nm. InGaN nanostripes feature c-axis oriented InGaN in the core which is covered by InGaN grown along semi-polar facets with higher In content. Transmission electron microscope and sub micron beam X-rays diffraction investigations confirm that both InGaN nanostructures are mostly defect free and monocrystalline. The ability to grow defect-free thick InGaN nanostructures with reduced polarization and high indium incorporation offers a solution to develop high efficiency InGaN-based solar cells.

  5. Characterization of ultrathin Al{sub 2}O{sub 3} gate oxide deposited by RF-magnetron sputtering on gallium nitride epilayer on sapphire substrate

    Energy Technology Data Exchange (ETDEWEB)

    Quah, Hock Jin; Cheong, Kuan Yew, E-mail: ckuanyew@yahoo.com

    2014-12-15

    A systematic study was performed on Al{sub 2}O{sub 3} films RF-magnetron sputtered on GaN substrate and subjected to different post-deposition annealing (PDA) temperatures (200–800 °C) in oxygen ambient. The as-deposited Al{sub 2}O{sub 3} film and Al{sub 2}O{sub 3} films subjected to PDA at 200 and 400 °C were present in amorphous phase and therefore undetectable by X-ray diffraction. By further enhancing the PDA temperature (≥600 °C), a transformation from amorphous to polycrystalline phase of Al{sub 2}O{sub 3} happened. The increment of PDA temperature has contributed to an enhancement in leakage current density-electric field (J–E) characteristics of the investigated samples. A correlation between the acquired J–E characteristics with effective oxide charge, slow trap density, interface trap density, and total interface trap density were discussed. A detailed investigation on the conduction of charges through the as-deposited Al{sub 2}O{sub 3} gate and Al{sub 2}O{sub 3} gates subjected to different PDA temperatures via space-charge-limited conduction, Schottky emission, Poole–Frenkel emission, and Fowler–Nordheim tunneling were presented. - Highlights: • Post-deposition annealing (PDA) in oxygen ambient of Al{sub 2}O{sub 3} films deposited on GaN. • Formation of crystalline Al{sub 2}O{sub 3} films subjected to PDA at/beyond 600 °C. • J–E characteristics of Al{sub 2}O{sub 3}/GaN system are dependent on MOS characteristics. • Al{sub 2}O{sub 3}/GaN system was subjected to high temperature measurements. • Current conduction mechanisms governing the leakage current of Al{sub 2}O{sub 3}/GaN system.

  6. Change in organic molecule adhesion on α-alumina (Sapphire) with change in NaCl and CaCl2 solution salinity

    DEFF Research Database (Denmark)

    Juhl, Klaus; Bovet, Nicolas Emile; Hassenkam, Tue

    2014-01-01

    We investigated the adhesion of two functional groups to α-alumina as a model for the adsorption of organic molecules on clay minerals. Interactions between organic compounds and clay minerals play an important role in processes such as drinking water treatment, remediation of contaminated soil, ...... in surface properties, controlling surface tension (i.e., contact angle) and adsorption affinity on α-alumina and, by analogy, on clay minerals.......H surface at pH surface interaction with the carboxylic acid and pyridine groups. We interpret the results as evidence...... protonated surface. The results demonstrate that the alumina surface at pH 3 has a higher affinity for inorganic cations than for -COO(H) or -C5H5N(H+), in spite of the known positive surface charge of α-alumina {0001} wafers. These results demonstrate that solution salinity plays an important role...

  7. Hydrothermal epitaxial growth of ZnO films on sapphire substrates presenting epitaxial ZnAl{sub 2}O{sub 4} buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hou-Guang, E-mail: houguang@isu.edu.tw; Wang, Chi-Wei; Tu, Zhi-Fan

    2014-03-01

    This article describes our investigation of the hydrothermal epitaxial growth of c-plane ZnO films on Al{sub 2}O{sub 3} substrates presenting ZnAl{sub 2}O{sub 4} buffer layers. We obtained (111) ZnAl{sub 2}O{sub 4} epitaxial layers on a-plane Al{sub 2}O{sub 3} substrates readily through solid phase epitaxy. Although the ZnAl{sub 2}O{sub 4} buffer layers grew epitaxially with a (111) out-of-plane orientation and comprised two coexisting equivalent azimuthal variants with relative 180° in-plane rotation, the ZnO epitaxial films grown upon them exhibited a c-plane orientation with unitary in-plane epitaxial orientation of <11{sup ¯}00>{sub ZnO}∥<11{sup ¯}0>{sub ZnAl{sub 2O{sub 4}}} on the two different ZnAl{sub 2}O{sub 4} variants. Taking the coincidence of the site lattices between the (0001) plane of ZnO and the (111) plane of ZnAl{sub 2}O{sub 4} into account, a reduction in lattice misfit was achieved through a 30° rotation between the lattices of the ZnO and the ZnAl{sub 2}O{sub 4}. We used X-ray diffraction and transmission electron microscopy to obtain detailed microstructural views of the hydrothermally grown ZnO epitaxial films on the ZnAl{sub 2}O{sub 4} buffer layers. - Highlights: • The c-plane ZnO films were epitaxially grown on Al{sub 2}O{sub 3} substrates presenting ZnAl{sub 2}O{sub 4} buffer layers. • We obtained (111) ZnAl{sub 2}O{sub 4} epitaxial layers on a-plane Al{sub 2}O{sub 3} substrates through solid phase epitaxy. • The ZnAl{sub 2}O{sub 4} layers comprised two equivalent azimuthal variants with relative 180° in-plane rotation. • The c-plane ZnO epitaxial films grown on ZnAl{sub 2}O{sub 4} layers with an in-plane relationship of <11{sup ¯}00>{sub ZnO}∥<11{sup ¯}0>{sub ZnAl{sub 2O{sub 4}}}.

  8. Orientational control of CeO 2 buffer layers on A-plane sapphire substrates for REBa 2Cu 3O 7-σ thin films

    Science.gov (United States)

    Sakuma, K.; Michikami, O.

    2010-11-01

    We attempted the epitaxial growth of CeO2 on A-plane Al2O3(1 1 2 bar 0) (A-Al2O3) substrates. As a buffer layers, CeO2 layers (CeO2-I) were firstly prepared on A-Al2O3 substrates at room temperature, and crystallized by ex situ annealing. The second CeO2 layers (CeO2-II) were deposited on CeO2-I. The thickness of CeO2-I dependence of the characteristics of CeO2-II and EuBa2Cu3O7-σ (EBCO) thin films, which were deposited on CeO2-II, was investigated. The CeO2-II layer completely was oriented along the c axis, while the in-plane orientation was not perfect. The critical current density (Jc) decreased with degrading the in-plane orientation of EBCO thin films. It is found that the in-plane orientation of EBCO thin films greatly effected on Jc. The best Jc value at 77.3 K of EBCO thin films was 1.9 MA/cm2.

  9. Comparison between a supercontinuum source and a titanium sapphire laser in achieving ultrahigh resolution spectral domain optical coherence tomography (SD-OCT)

    Science.gov (United States)

    Caujolle, S.; Unterhuber, A.; Feuchter, T.; Podoleanu, A.; Werkmeister, R. M.

    2017-07-01

    Corneal B-scan images and signal-to-noise ratio measurements using ultra-high resolution Spectral Domain Optical Coherence Tomography (SD-OCT) are reported. A comparison of results is obtained using a Ti:Sa laser and a supercontinuum optical source, is performed. Beside some differences in the SNR, the images are strikingly similar.

  10. Genetic Variation in the Human SORBS1 Gene is Associated With Blood Pressure Regulation and Age at Onset of Hypertension: A SAPPHIRe Cohort Study.

    Science.gov (United States)

    Chang, Tien-Jyun; Wang, Wen-Chang; Hsiung, Chao A; He, Chih-Tsueng; Lin, Ming-Wei; Sheu, Wayne Huey-Herng; Chang, Yi-Cheng; Quertermous, Tom; Chen, Ida; Rotter, Jerome; Chuang, Lee-Ming

    2016-03-01

    Essential hypertension is a complex disease involving multiple genetic and environmental factors. A human gene containing a sorbin homology domain and 3 SH3 domains in the C-terminal region, termed SORBS1, plays a significant role in insulin signaling. We previously found a significant association between the T228A polymorphism and insulin resistance, obesity, and type 2 diabetes. It has been hypothesized that a set of genes responsible for insulin resistance may be closely linked with genes susceptible to the development of hypertension. Identification of insulin resistance-related genetic factors may, therefore, enhance our understanding of essential hypertension. This study aimed to examine whether common SORBS1 genetic variations are associated with blood pressure and age at onset of hypertension in an ethnic Chinese cohort.We genotyped 9 common tagged single nucleotide polymorphisms of the SORBS1 gene in 1136 subjects of Chinese origin from the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance family study. Blood pressure was measured upon enrolment. The associations of the SORBS1 single nucleotide polymorphisms with blood pressure and the presence of hypertension were analyzed with a generalized estimating equation model. We used the false-discovery rate measure Q value with a cutoff antihypertension medication were adjustment covariates in the Cox regression analysis.In this study, genetic variants of rs2281939 and rs2274490 were significantly associated with both systolic and diastolic blood pressure. A genetic variant of rs2274490 was also significantly associated with the presence of hypertension. Furthermore, genetic variants of rs2281939 and rs2274490 were associated with age at onset of hypertension after adjustment for gender, body mass index, and antihypertension medication.In conclusion, we provide evidence for an association between common SORBS1 genetic variations and blood pressure, presence of hypertension, and age at onset of hypertension. The biological mechanism of genetic variation associated with blood pressure regulation needs further investigation.

  11. HYBRID SILICON-ON-SAPPHIRE/SCALED CMOS INTERFERENCE MITIGATION FRONT END BASED ON SIMULTANEOUS NOISE CANCELLATION, ACTIVE-INTERFERENCE CANCELLATION AND N-PATH-MIXER FILTERING

    Science.gov (United States)

    2017-04-01

    orthogonal frequency-division multiplexing (OFDM)-like modulated TX signal. Conventional reciprocal ANT interfaces, such as surface acoustic wave (SAW...RF interconnections at board-level. A wireless imaging demo shows two of the implemented ICs tiled on board to form an eight-element MIMO receiver...Measured spatial responses show >30dB of spatial notch suppression in the broadside direction. Two ICs can be tiled on printed circuit board (PCB) to

  12. Growth and charge ordering of epitaxial YbFe2O4 films on sapphire using Fe3O4 buffer layer

    Science.gov (United States)

    Fujii, Tatsuo; Numata, Tomoya; Nakahata, Hiroki; Nakanishi, Makoto; Kano, Jun; Ikeda, Naoshi

    2018-01-01

    Well-crystallized epitaxial YbFe2O4 films were prepared on an α-Al2O3(001) substrate using an Fe3O4 buffer layer. Fe3O4 has a relatively small lattice mismatch with both YbFe2O4 and α-Al2O3. Electron diffraction analysis combined with transmission electron microscopy revealed the epitaxial relationship to be α-Al2O3[110](001) ∥ Fe3O4[\\bar{2}11](111) ∥ YbFe2O4[110](001). Moreover, superlattice spots due the Fe2+–Fe3+ charge order state of YbFe2O4 were clarified. The Fe2+/Fe3+ ratio in YbFe2O4 was nearly stoichiometric. The film exhibited a ferrimagnetic transition at ∼220 K and a nonlinear current–voltage characteristic at room temperature. These results confirmed the good crystallinity and stoichiometry of the obtained YbFe2O4 films.

  13. Improved luminescence from InGaN/GaN MQWs by reducing initial nucleation density using sputtered AlN on sapphire substrate

    Science.gov (United States)

    Wang, Hongbo; Sodabanlu, Hassanet; Daigo, Yoshiaki; Seino, Takuya; Nakagawa, Takashi; Sugiyama, Masakazu

    2017-05-01

    The edge dislocations in GaN film were reduced by lowering initial islands density and extending islands coalescence time in MOVPE, which were achieved more effectively on an ex situ sputtered AlN seed layer than on an in situ LT-GaN seed layer. GaN film with low dislocation density was achieved on an ex situ sputtered AlN seed layer by initial growth optimization as indicated by the dark spots density of 1.5 × 108 cm-2 of cathode-luminescence mapping measurement. Stress relaxation was observed for the GaN film grown from sparse initial islands on an ex situ sputtered AlN seed layer as indicated by in situ wafer curvature measurement. Temperature quenching of photoluminescence from InGaN/GaN multiple quantum wells grown on a GaN template was mitigated when an ex situ sputtered AlN seed layer was employed compared with the case with an in situ LT-GaN seed layer, confirming that the reduced nucleation density by both the use of a sputtered AlN seed and the optimization of GaN growth condition is effective for suppressing non-radiative recombination in InGaN by the reduction in edge dislocation density.

  14. Optical waveguides in hard crystalline materials

    NARCIS (Netherlands)

    Pollnau, Markus

    2005-01-01

    The recent results of our research group and collaborators in the field of fabrication, characterization, and applications of optical waveguides in hard crystalline materials, specifically in sapphire and Ti:sapphire, are reviewed.

  15. Orientational control of CeO{sub 2} buffer layers on A-plane sapphire substrates for REBa{sub 2}Cu{sub 3}O{sub 7-{sigma}}thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, K., E-mail: t3308008@iwate-u.ac.j [Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka-shi, Iwate 020-8551 (Japan); Michikami, O. [Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka-shi, Iwate 020-8551 (Japan)

    2010-11-01

    We attempted the epitaxial growth of CeO{sub 2} on A-plane Al{sub 2}O{sub 3}(112-bar0) (A-Al{sub 2}O{sub 3}) substrates. As a buffer layers, CeO{sub 2} layers (CeO{sub 2}-I) were firstly prepared on A-Al{sub 2}O{sub 3} substrates at room temperature, and crystallized by ex situ annealing. The second CeO{sub 2} layers (CeO{sub 2}-II) were deposited on CeO{sub 2}-I. The thickness of CeO{sub 2}-I dependence of the characteristics of CeO{sub 2}-II and EuBa{sub 2}Cu{sub 3}O{sub 7-{sigma}}(EBCO) thin films, which were deposited on CeO{sub 2}-II, was investigated. The CeO{sub 2}-II layer completely was oriented along the c axis, while the in-plane orientation was not perfect. The critical current density (J{sub c}) decreased with degrading the in-plane orientation of EBCO thin films. It is found that the in-plane orientation of EBCO thin films greatly effected on J{sub c}. The best J{sub c} value at 77.3 K of EBCO thin films was 1.9 MA/cm{sup 2}.

  16. Improved Semipolar (112¯2) GaN Quality Grown on m-Plane Sapphire Substrates by Metal Organic Chemical Vapor Deposition Using Self-Organized SiN x Interlayer

    Science.gov (United States)

    Sheng-Rui, Xu; Ying, Zhao; Teng, Jiang; Jin-Cheng, Zhang; Pei-Xian, Li; Yue, Hao

    2016-06-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 61204006 and 61574108, the Fundamental Research Funds for the Central Universities under Grant No JB141101, and the Foundation of Key Laboratory of Nanodevices and Applications of Suzhou Institute of Nano-Tech and Nano-Bionics of Chinese Academy of Sciences under Grant No 15CS01.

  17. Fabrication of miniature fiber-optic temperature sensors

    Science.gov (United States)

    Zhu, Yizheng; Wang, Anbo

    2010-07-27

    A method of coupling a silica fiber and a sapphire fiber includes providing a silica fiber having a doped core and a cladding layer, with the doped core having a prescribed diameter, providing a sapphire fiber having a diameter less than the doped core, placing an end of the sapphire fiber in close proximity to an end of the silica fiber, applying a heat source to the end of silica fiber and introducing the end of sapphire fiber into the heated doped core of the silica fiber to produce a coupling between the silica and sapphire fibers.

  18. Advanced Neutron Moderators for the ESS

    DEFF Research Database (Denmark)

    Schönfeldt, Troels

    signicantly to the overall quality of the ESS. Chapter 9 suggests a novel type of broad-spectrum moderator. This moderator concept is based on the idea that heavy metals, such as lead and bismuth, are inefficient moderator materials. The article investigates this idea through enriched 208Pb. The article shows...... crystal. The experiment compares single-crystal sapphire, sapphire powder and void. Sapphire was used, since no other single-crystal candidates (diamond, pyrolytic graphite and lithium uoride) could be obtained within the cost and time constraints of the experiment. Unfortunately, sapphire does...

  19. Remote Heat Flux Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    Science.gov (United States)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (k = 6 gm). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 gm) radiation transmitted through the sapphire disk. The thermal conductivity of the sapphire disk and the heat transfer coefficients h, and h2 of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  20. Remote Heat Flux Measurement Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    Science.gov (United States)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (lambda > 6 micrometers). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 micrometers) radiation transmitted through the sapphire disk. The thermal conductivity k of the sapphire disk and the heat transfer coefficients h(sub 1) and h(sub 2) of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  1. Relation between the microstructure and magnetic properties of BaFe12O19 thin films grown on various substrates

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.

    2002-01-01

    Barium ferrite films grown on sapphire and oxidized silicon substrates exhibit a granular structure with cluster-like magnetic domains. On sapphire, high perpendicular anisotropy can be achieved.The films grown on SiO2 /Si develop textures with nearly in-plane c axis, which induce a large in-plane

  2. Compact green-diode-based lasers for biophotonic bioimaging

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Hansen, Anders Kragh; Petersen, Paul Michael

    2014-01-01

    Diode lasers simultaneously offer tunability, high-power emission, and compact size at fairly low cost and are increasingly preferred for pumping titanium:sapphire lasers.......Diode lasers simultaneously offer tunability, high-power emission, and compact size at fairly low cost and are increasingly preferred for pumping titanium:sapphire lasers....

  3. Central obesity is important but not essential component of the metabolic syndrome for predicting diabetes mellitus in a hypertensive family-based cohort. Results from the Stanford Asia-pacific program for hypertension and insulin resistance (SAPPHIRe) Taiwan follow-up study.

    Science.gov (United States)

    Lee, I-Te; Chiu, Yen-Feng; Hwu, Chii-Min; He, Chih-Tsueng; Chiang, Fu-Tien; Lin, Yu-Chun; Assimes, Themistocles; Curb, J David; Sheu, Wayne H-H

    2012-04-26

    Metabolic abnormalities have a cumulative effect on development of diabetes, but only central obesity has been defined as the essential criterion of metabolic syndrome (MetS) by the International Diabetes Federation. We hypothesized that central obesity contributes to a higher risk of new-onset diabetes than other metabolic abnormalities in the hypertensive families. Non-diabetic Chinese were enrolled and MetS components were assessed to establish baseline data in a hypertensive family-based cohort study. Based on medical records and glucose tolerance test (OGTT), the cumulative incidence of diabetes was analyzed in this five-year study by Cox regression models. Contribution of central obesity to development of new-onset diabetes was assessed in subjects with the same number of positive MetS components. Among the total of 595 subjects who completed the assessment, 125 (21.0%) developed diabetes. Incidence of diabetes increased in direct proportion to the number of positive MetS components (P ≪ 0.001). Although subjects with central obesity had a higher incidence of diabetes than those without (55.7 vs. 30.0 events/1000 person-years, P ≪ 0.001), the difference became non-significant after adjusting of the number of positive MetS components (hazard ratio = 0.72, 95%CI: 0.45-1.13). Furthermore, in all participants with three positive MetS components, there was no difference in the incidence of diabetes between subjects with and without central obesity (hazard ratio = 1.04, 95%CI: 0.50-2.16). In Chinese hypertensive families, the incidence of diabetes in subjects without central obesity was similar to that in subjects with central obesity when they also had the same number of positive MetS components. We suggest that central obesity is very important, but not the essential component of the metabolic syndrome for predicting of new-onset diabetes. ( NCT00260910, ClinicalTrials.gov).

  4. Characterization of ZnO thin film grown on c-plane substrates by MO-CVD: Effect of substrate annealing temperature, vicinal-cut angle and miscut direction

    Science.gov (United States)

    Boukadhaba, M. A.; Fouzri, A.; Sallet, V.; Hassani, S. S.; Amiri, G.; Lusson, A.; Oumezzine, M.

    2015-09-01

    The annealing effects of c-plane sapphire (α-Al2O3) substrate with a nominally vicinal-cut angle α (α ZnO films grown by metal organic chemical vapor deposition (MO-CVD) were studied. The atomic steps formed on sapphire substrate surface by annealing at high temperature were analyzed by atomic force microscopy (AFM). The annealing and the miscut direction of sapphire substrate on the microstructural and optical properties for ZnO films were examined by high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). Experimental results indicate that the film quality is strongly affected by annealing treatment and miscut direction of the sapphire substrate. X-ray diffraction study revealed that all films exhibit a wurtzite phase and have a c-axis orientation. ZnO films deposited on sapphire substrate (α ZnO layer deposited on annealed sapphire substrate with increase the annealing substrate temperature for all samples. AFM image show significant differences between morphologies of samples depending on annealing treatment and miscut direction of substrates but no significant differences on surface roughness have been found. Sapphire annealing at 1100 °C with a nominally vicinal-cut angle α = 0.25° toward the m-plane (1 0 1 bar 0), provides the best optical quality of ZnO film.

  5. Influence of anisotropy on thermal boundary conductance at solid interfaces

    Science.gov (United States)

    Hopkins, Patrick E.; Beechem, Thomas; Duda, John C.; Hattar, Khalid; Ihlefeld, Jon F.; Rodriguez, Mark A.; Piekos, Edward S.

    2011-09-01

    We investigate the role of anisotropy on interfacial transport across solid interfaces by measuring the thermal boundary conductance from 100 to 500 K across Al/Si and Al/sapphire interfaces with different substrate orientations. The measured thermal boundary conductances show a dependency on substrate crystallographic orientation in the sapphire samples (trigonal conventional cell) but not in the silicon samples (diamond cubic conventional cell). The change in interface conductance in the sapphire samples is ascribed to anisotropy in the Brillouin zone along the principal directions defining the conventional cell. This leads to resultant phonon velocities in the direction of thermal transport that vary nearly 40% based on crystallographic direction.

  6. IR surface polariton spectroscopy as a method for studying the optical properties of ultra thin films

    Directory of Open Access Journals (Sweden)

    Vinogradov E.A.

    2017-01-01

    Full Text Available Experimental results of investigation of optical properties of MgO thin films (thickness 10, 30, 100 и 300 nm and AlN films (thickness 40 и 400 nm on sapphire substrate are discussed. The optical phonon frequencies of these films are located in frequency region of surface polariton of sapphire. Due to the resonance between them the splitting and the shift of absorption spectra of sapphire surface polariton appear. From these experimental data it is possible to reconstruct all constants of the permittivity of both the film and substrate, the film thickness, and to specify its structure.

  7. In-Flight Imaging Systems for Hypervelocity and Re-Entry Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — It is proposed to create a rugged, reliable, compact, standardized imaging system for hypervelocity and re-entry vehicles using sapphire windows, small imagers, and...

  8. Tool development to understand rural resource users' land use and ...

    African Journals Online (AJOL)

    ,. Hunting in the Marshes (light green), Onion/ Rice/ Vegetable Farming in either. Marshes/ Agriculture zone (yellow)/ Open landscape (orange), or Rosewood logging or Sapphire mining in the Forest (dark green); players can also invest into.

  9. High-Frequency, Low-Noise Nitride-Based Power Transistors Grown on Bulk III-N Project

    Data.gov (United States)

    National Aeronautics and Space Administration — One of the main issues for III-nitride growth is the lack of a suitable native substrate. Growth on foreign substrates such as sapphire or SiC results in nitride...

  10. Advanced photon detectors using superconducting MgB2 films Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The goals of the proposed work are to Investigate the film thickness (10–50 nm), substrate material (c-plane sapphire, MgO), and temperature (20-35 K)...

  11. Autocorrelation and Frequency-Resolved Optical Gating Measurements Based on the Third Harmonic Generation in a Gaseous Medium

    National Research Council Canada - National Science Library

    Yoshinari Takao; Tomoko Imasaka; Yuichiro Kida; Totaro Imasaka

    2015-01-01

      A gas was utilized in producing the third harmonic emission as a nonlinear optical medium for autocorrelation and frequency-resolved optical gating measurements to evaluate the pulse width and chirp of a Ti:sapphire laser...

  12. Rhombohedrel Hybrid Crystal Semiconductor Device Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA Langley has succeeded in growing a rhombohedrally oriented single crystal SiGe on sapphire substrate. This opens up new challenges in micro-electronics. Since...

  13. Tunneling anisotropic magnetoresistance in Co/AIOx/Al tunnel junctions with fcc Co (111) electrodes

    NARCIS (Netherlands)

    Wang, Kai; Tran, T. Lan Ahn; Brinks, Peter; Brinks, P.; Sanderink, Johannes G.M.; Bolhuis, Thijs; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    2013-01-01

    Tunneling anisotropic magnetoresistance (TAMR) has been characterized in junctions comprised of face-centered cubic (fcc) Co (111) ferromagnetic electrodes grown epitaxially on sapphire substrates, amorphous AlOx tunnel barriers, and nonmagnetic Al counterelectrodes. Large TAMR ratios have been

  14. Femtosecond optical transfection of cells:viability and efficiency

    National Research Council Canada - National Science Library

    D. Stevenson; B. Agate; X. Tsampoula; P. Fischer; C. T. A. Brown; W. Sibbett; A. Riches; F. Gunn-Moore; K. Dholakia

    2006-01-01

    .... However, there remains no study into the true efficiency of this procedure. Here, we present a detailed analysis of transfection efficiency and cell viability for femtosecond optical transfection using a titanium sapphire laser at 800 nm...

  15. GaN Based Structures for NEA by MBE and Investigation of Nitrogen Species and Precursors for Optimum Layer Properties

    National Research Council Canada - National Science Library

    Morkoc, Hadis

    1997-01-01

    ... (GaN which are stable at 500 deg C, Pt Schottky barriers with nearly a unity ideality factor which appear stable at operation temperatures of about 500 deg C, AlGaN/GaN MODFETs on sapphire substrates...

  16. Investigation of Critical Problems in GaN/AIGaN Modfets

    National Research Council Canada - National Science Library

    Morkoc, Hadis

    2000-01-01

    MBE AlN layers have been optimized on sapphire substrates. MBE GaN layers have been optimized with ammonia and RF nitrogen sources and Ga polarity films have been consistently obtained using both ammonia and RF nitrogen...

  17. Low radioactivity material for use in mounting radiation detectors

    Science.gov (United States)

    Fong, Marshall; Metzger, Albert E.; Fox, Richard L.

    1988-01-01

    Two materials, sapphire and synthetic quartz, have been found for use in Ge detector mounting assemblies. These materials combine desirable mechanical, thermal, and electrical properties with the radioactive cleanliness required to detect minimal amounts of K, Th, and U.

  18. Low-noise X-band Oscillator and Amplifier Technologies: Comparison and Status

    National Research Council Canada - National Science Library

    Howe, D. A; Hati, A

    2005-01-01

    .... Best-in-class results are presented based on recent measurements at NIST. In particular, comparisons are made between mature technologies of multiplied quartz, sapphire dielectric in whispering gallery mode (WGM...

  19. Millimeter-wave receiver design for plasma diagnostics

    DEFF Research Database (Denmark)

    Leipold, Frank; Hansen, S. K.; Jacobsen, Asger Schou

    2016-01-01

    Scattered millimeter waves entering from the collective Thomson scattering diagnostic at ASDEX Upgrade fusion device are generally elliptically polarized. In order to convert the millimeter waves to linearly polarized waves (required for the detector), birefringent window assemblies (sapphire) ha...

  20. Development of a Photoelectrochemical Etch Process to Enable Heterogeneous Substrate Integration of Epitaxial III-Nitride Semiconductors

    Science.gov (United States)

    2017-12-01

    transfer of a GaN lasing stack onto a diamond submount. Although GaN liftoff from sapphire has been demonstrated with laser irradiation,1 the physical ... quantum wells6 provides an alternative way to have a light absorber that etches in an electrochemical environment. Approved for public release...sapphire substrates. Applied Physics Letters. 1998;72:599–601. 2. Khare R, Hu EL. Dopant selective photoelectrochemical etching of GaAs homostructures

  1. Substrate Effect on Optical Properties of Insulator-Metal Transition in VO2 Thin Films

    OpenAIRE

    Radue, E.; Crisman, E.; L. Wang; Kittiwatanakul, S.; Lu, J.; Wolf, S. A.; Wincheski, R.; Lukaszew, R. A.; Novikova, I.

    2012-01-01

    In this paper we used Raman spectroscopy to investigate the optical properties of vanadium dioxide (VO2) thin films during the thermally induced insulating to metallic phase transition. We observed a significant difference in transition temperature in similar VO2 films grown on quartz and sapphire substrates: the film grown on quartz displayed the phase transition at a lower temperature (Tc=50C) compared a film grown on sapphire (Tc=68C). We also investigated differences in the detected Raman...

  2. Development of high resolution resonance ionization mass spectrometry for trace analysis of {sup 93m}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Takatsuka, Takaaki; Tomita, Hideki, E-mail: tomita@nagoya-u.jp [Nagoya University (Japan); Sonoda, Tetsu [RIKEN Nishina Center (Japan); Sonnenschein, Volker [Johannes Gutenberg University (Germany); Sakamoto, Chika [Nagoya University (Japan); Mita, Hiroki [University of Tsukuba, Institute of Physics (Japan); Noto, Takuma [Nagoya University (Japan); Ito, Chikara; Maeda, Shigetaka [Japan Atomic Energy Agency, Oarai Research and Development Center (Japan); Iguchi, Tetsuo [Nagoya University (Japan); Wada, Michiharu [RIKEN Nishina Center (Japan); Wendt, Klaus [Johannes Gutenberg University (Germany); Moore, Iain [University of Jyvaeskylae, Department of Physics (Finland)

    2013-04-15

    {sup 93}Nb(n, n Prime ){sup 93m}Nb reaction allows retrospective estimation of integrated fast neutron dose in nuclear reactor. We proposed isomer-selective trace analysis of {sup 93m}Nb by Resonance Ionization Mass Spectrometry (RIMS) combined with a gas-jet atomic source and an injection locked Ti:Sapphire laser system operated at several kHz. Resonant ionization spectroscopy of Nb in gas-jet using Ti:Sapphire laser was demonstrated.

  3. A Fluorescence-Based Determination of Quantum Efficiency

    Science.gov (United States)

    2013-12-01

    accepted high quantum efficiency values of close to 1. 3. Equipment The following equipment was used: • Spectra-Physics titanium sapphire laser...fiber with a 550-µm core and a 0.22 numerical aperture • Edmund Optics integrating sphere • Avian Technologies Avian-B barium sulfate white reflectance...sphere used in this experiment was one purchased from Edmund Optics. The Spectra-Physics titanium sapphire laser was chopped at 100 Hz and then allowed

  4. Pb(Zr,TiO3 (PZT Thin Film Sensors for Fully-Integrated, Passive Telemetric Transponders

    Directory of Open Access Journals (Sweden)

    Richard X. FU

    2011-04-01

    Full Text Available The great potential of taking advantages of PZT in a single chip to achieve inexpensive, fully-integrated, passive telemetric transponders has been shown in this paper. The processes for the sputter deposition of Pb(Zr,TiO3 (PZT thin films from two different composite targets on both Si and c-plane sapphire substrates have been demonstrated. PZT thin films have been deposited by sputter technique. PZT films were deposited onto substrates (Si [(100 Cz wafer] and c-plane sapphire (0001//Ti//Pt followed by sputter-deposited Pt top electrodes. X-ray diffraction results showed that both sputtered PZT films were textured along the [110] direction. The degree of preference for the [110] direction was greater on sapphire substrate where the intensity of that peak is seen to be larger compared to the intensity one Si substrate. TEM data revealed that both sputtered PZT films were polycrystalline in nature. Selected area diffraction (SAD pattern showed that the degree of disorientation between the crystallites was smaller on sapphire substrate compared to on Si substrate, which confirmed the results from the XRD. The remnant polarization Pr on sapphire substrate was larger than on Si’s. The leakage current for the 11 % Pb target sputtered film was much less than 22 % Pb target sputtered film. The breakdown voltage on sapphire substrate was the best. However, for the 11 % Pb target sputtered film’s breakdown voltage was much higher than 22 % Pb target sputtered film.

  5. AlN thin film grown on different substrates by hydride vapor phase epitaxy

    Science.gov (United States)

    Sun, M. S.; Zhang, J. C.; Huang, J.; Wang, J. F.; Xu, K.

    2016-02-01

    AlN thin films have been grown on GaN/sapphire templates, 6 H-SiC and sapphire by hydride vapor phase epitaxy. The influence of growth conditions and substrates on the crystal qualities and growth mode has been investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results showed that the low pressure was favorable for high-quality AlN thin film growth around 1000 °C. The full-width at half-maximum (FWHM) of (0002) XRD of 200-nm AlN thin film grown on GaN/sapphire, 6 H-SiC and sapphire are 220, 187 and 260 arc s, respectively. While the corresponding counterparts of (10-12) are 1300, 662 and 2650 arc s, respectively. Both suggested that low dislocation density in AlN grown on 6 H-SiC. The morphology of AlN thin film on sapphire showed islands without coalescence initially, and then changed to be coalescent with atomic steps at 1200 nm. However, those for samples on 6 H-SiC and GaN/sapphire showed smooth surface with clear atomic steps at thickness of 200 nm. The result indicated different growth modes of AlN on different substrates. It was believed that the different lattice mismatchs between AlN and substrates led to the different crystal qualities and growth modes.

  6. Integrated Multi-Color Light Emitting Device Made with Hybrid Crystal Structure

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

    2017-01-01

    An integrated hybrid crystal Light Emitting Diode ("LED") display device that may emit red, green, and blue colors on a single wafer. The various embodiments may provide double-sided hetero crystal growth with hexagonal wurtzite III-Nitride compound semiconductor on one side of (0001) c-plane sapphire media and cubic zinc-blended III-V or II-VI compound semiconductor on the opposite side of c-plane sapphire media. The c-plane sapphire media may be a bulk single crystalline c-plane sapphire wafer, a thin free standing c-plane sapphire layer, or crack-and-bonded c-plane sapphire layer on any substrate. The bandgap energies and lattice constants of the compound semiconductor alloys may be changed by mixing different amounts of ingredients of the same group into the compound semiconductor. The bandgap energy and lattice constant may be engineered by changing the alloy composition within the cubic group IV, group III-V, and group II-VI semiconductors and within the hexagonal III-Nitrides.

  7. New Optical Sensor Suite for Ultrahigh Temperature Fossil Fuel Applications

    Energy Technology Data Exchange (ETDEWEB)

    Russell G. May; Tony Peng; Gary Pickrell

    2005-10-31

    Development of practical, high-temperature optical claddings for improved waveguiding in sapphire fibers continued during the reporting period. A set of designed experiments using the Taguchi method was undertaken to efficiently determine the optimal set of processing variables to yield clad fibers with good optical and mechanical properties. Eighteen samples of sapphire fibers were prepared with spinel claddings, each with a unique set of variables. Statistical analyses of the results were then used to predict the set of factors that would result in a spinel cladding with the optimal geometrical, mechanical, and optical properties. To confirm the predictions of the Taguchi analysis, sapphire fibers were clad with the magnesium aluminate spinel coating using the predicted optimal set of factors. In general, the clad fibers demonstrated high quality, exceeding the best results obtained during the Phase I effort. Tests of the high-temperature stability of the clad fibers were also conducted. The results indicated that the clad fibers were stable at temperatures up to 1300 C for the duration of the three day test. At the higher temperatures, some changes in the geometry of the fibers were observed. The design, fabrication, and testing of a sapphire sensor for measurement of temperature was undertaken. The specific sensor configuration uses a polished sapphire wafer as the temperature-sensitive element. The wafer is attached to a sapphire fiber (clad or unclad), and interrogated as a Fabry-Perot sensor. Methods for assembling the sensor were investigated. A prototype sensor was fabricated and tested at room temperature and elevated temperatures. Results were difficult to interpret, due to the presence of modal noise which was found to result from the use of a spectrometer that was not designed for use with multimode fibers. A spectrometer optimized for use of multimode fiber has been obtained, and further evaluation of the sapphire temperature sensor is continuing.

  8. Abbreviated epitaxial growth mode (AGM) method for reducing cost and improving quality of LEDs and lasers

    Science.gov (United States)

    Tansu, Nelson; Chan, Helen M; Vinci, Richard P; Ee, Yik-Khoon; Biser, Jeffrey

    2013-09-24

    The use of an abbreviated GaN growth mode on nano-patterned AGOG sapphire substrates, which utilizes a process of using 15 nm low temperature GaN buffer and bypassing etch-back and recovery processes during epitaxy, enables the growth of high-quality GaN template on nano-patterned AGOG sapphire. The GaN template grown on nano-patterned AGOG sapphire by employing abbreviated growth mode has two orders of magnitude lower threading dislocation density than that of conventional GaN template grown on planar sapphire. The use of abbreviated growth mode also leads to significant reduction in cost of the epitaxy. The growths and characteristics of InGaN quantum wells (QWs) light emitting diodes (LEDs) on both templates were compared. The InGaN QWs LEDs grown on the nano-patterned AGOG sapphire demonstrated at least a 24% enhancement of output power enhancement over that of LEDs grown on conventional GaN templates.

  9. Spectroscopic studies on technetium and silicon. A solid-state laser system for the resonance-ionization spectroscopy; Spektroskopische Untersuchungen an Technetium und Silizium. Ein Festkoerperlasersystem fuer die Resonanzionisationsspektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Mattolat, Christoph

    2010-11-15

    This doctoral thesis describes advancement and refinement of the titanium:sapphire laser system of the working group LARISSA, Institut fuer Physik, Johannes Gutenberg- Universitaet Mainz and its application to resonance ionization spectroscopy. Activities on the laser systems comprised three major tasks: The output power of the conventional titanium:sapphire lasers could be increased by a factor of two in order to match the needs at resonance ionization laser ion source at ISOL facilities. Additionally, the laser system was complemented by a titanium:sapphire laser in Littrow geometry, which ensures a mode-hop free tuning range from 700 nm to 950 nm, and by an injection seeded titanium:sapphire laser with a spectral width of 20 MHz (in respect to a spectral width of 3 GHz for the conventional lasers). The performance of the new laser system was tested in spectroscopic investigations of highly excited atomic levels of gold and technetium. From the measured level positions the ionization potential of gold could be verified by using the Rydberg-Ritz formula, while the ionization potential of technetium could be determined precisely for the first time. Using the seeded titanium: sapphire laser Doppler-free two-photon spectroscopy inside a hot ionizer cavity was demonstrated. A width of the recorded resonances of 90 MHz was achieved and the hyperfine structure and isotope shift of stable silicon isotopes was well resolved with this method. (orig.)

  10. Cleaning Genesis Solar Wind Collectors with Ultrapure Water: Residual Contaminant Particle Analysis

    Science.gov (United States)

    Allton, J. H.; Wentworth, S. J.; Rodriquez, M. C.; Calaway, M. J.

    2008-01-01

    Additional experience has been gained in removing contaminant particles from the surface of Genesis solar wind collectors fragments by using megasonically activated ultrapure water (UPW)[1]. The curatorial facility has cleaned six of the eight array collector material types to date: silicon (Si), sapphire (SAP), silicon-on-sapphire (SOS), diamond-like carbon-on-silicon (DOS), gold-on-sapphire (AuOS), and germanium (Ge). Here we make estimates of cleaning effectiveness using image analysis of particle size distributions and an SEM/EDS reconnaissance of particle chemistry on the surface of UPW-cleaned silicon fragments (Fig. 1). Other particle removal techniques are reported by [2] and initial assessment of molecular film removal is reported by [3].

  11. WAFER TEST CAVITY -Linking Surface Microstructure to RF Performance: a ‘Short-­Sample Test Facility’ for characterizing superconducting materials for SRF cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Pogue, Nathaniel; Comeaux, Justin; McIntyre, Peter

    2014-05-30

    The Wafer Test cavity was designed to create a short sample test system to determine the properties of the superconducting materials and S-I-S hetero-structures. The project, funded by ARRA, was successful in accomplishing several goals to achieving a high gradient test system for SRF research and development. The project led to the design and construction of the two unique cavities that each severed unique purposes: the Wafer test Cavity and the Sapphire Test cavity. The Sapphire Cavity was constructed first to determine the properties of large single crystal sapphires in an SRF environment. The data obtained from the cavity greatly altered the design of the Wafer Cavity and provided the necessary information to ascertain the Wafer Test cavity’s performance.

  12. Development of resonance ionization in a supersonic gas-jet for studies of short-lived and long-lived radioactive nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Takatsuka, Takaaki, E-mail: takatsuka.takaaki@e.mbox.nagoya-u.ac.jp [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Tomita, Hideki [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Sonnenschein, Volker [Department of Physics, University of Jyväskylä, 40014 Jyväskylä (Finland); Sonoda, Tetsu [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Adachi, Yoshitaka; Sakamoto, Chika [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Mita, Hiroki [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Noto, Takuma [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Ito, Chikara; Maeda, Shigetaka [Oarai Research and Development Center, Japan Atomic Energy Agency, 4002 Narita, Oarai, Ibaraki 311-1393 (Japan); Iguchi, Tetsuo [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Wada, Michiharu [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wendt, Klaus [Johannes Gutenberg Univ., Staudingerweg 7, Mainz 55128 (Germany); Moore, Iain [Department of Physics, University of Jyväskylä, 40014 Jyväskylä (Finland)

    2013-12-15

    Highlights: • Resonance ionization of {sup 93}Nb in gas-jet was demonstrated using Ti:Sapphire laser. • The line width of the spectrum in the gas-jet was similar to that in vacuum. • An experimental setup for high-resolution RIS was designed. -- Abstract: High-resolution resonance ionization spectroscopy (RIS) is required for laser spectroscopy and trace analysis of short-lived and long-lived radioactive nuclei. We have proposed high-resolution resonance ionization spectroscopy in a gas jet combined with a narrow band-width injection-locked Ti:Sapphire laser. Resonance ionization of stable {sup 93}Nb in a gas jet was demonstrated using a broad bandwidth Ti:Sapphire laser. In addition, a setup for high-resolution RIS in a gas-jet was designed using numerical simulations of the gas-jet conditions based on computational fluid dynamics.

  13. The temperature dependent fracture strength of doped single crystal alumina fibers

    Energy Technology Data Exchange (ETDEWEB)

    Sayir, H.; Farmer, S.C.; Lagerlof, P. [NASA Lewis Research Center, Cleveland, OH (United States)] [and others

    1994-12-31

    The tensile strength of impurity doped, laser heated float zone (LHFZ) grown, single crystal sapphire ({alpha}-Al{sub 2}O{sub 3}) fibers were measured at elevated temperatures, 1100 and 1450{degrees}C. The effects of MgO doping, TiO{sub 2} doping and TiO{sub 2}/MgO co-doping were examined. MgO doping significantly enhanced the high temperature strength. At 1450{degrees}C, tensile strengths of MgO doped sapphire ({approximately}1760 MPa) are almost twice the strength of undoped fibers. In contrast, the effect of TiO{sub 2} doping and TiO{sub 2}/MgO-codoping on the tensile strength of sapphire fibers was not statistically significant at either 1100 or 1450{degrees}C. The relationship between strength distributions and temperature is examined and possible strengthening mechanisms are discussed.

  14. Solid-state laser source of narrowband ultraviolet B light for skin disease care with advanced performance

    Science.gov (United States)

    Tarasov, Aleksandr A.; Chu, Hong; Buchwald, Kristian

    2015-02-01

    Two years ago we reported about the development of solid state laser source for medical skin treatment with wavelength 310.6 nm and average power 200 mW. Here we describe the results of investigation of the advanced version of the laser, which is a more compact device with increased output power and flat top beam profile. Ti: Sapphire laser, the main module of our source, was modified and optimized such, that UV average power of the device was increased 1.7 times. Fiber optic homogenizer was replaced by articulated arm with diffraction diffuser, providing round spot with flat profile at the skin. We investigated and compare characteristics of Ti: Sapphire lasers with volume Bragg grating and with fused silica transmission grating, which was used first time for Ti: Sapphire laser spectral selection and tuning. Promising performance of last gratings is demonstrated.

  15. Polarity control and preparation of AlN nano-islands by hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, Toru; Hironaka, Keiichiro; Takada, Kazuya [Tsukuba Research Laboratories, Tokuyama Corporation, 40 Wadai, Tsukuba-shi, Ibaraki 300-4247 (Japan); Ishizuki, Masanari [Tsukuba Research Laboratories, Tokuyama Corporation, 40 Wadai, Tsukuba-shi, Ibaraki 300-4247 (Japan); Department of Applied Chemistry, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Kumagai, Yoshinao; Koukitu, Akinori [Department of Applied Chemistry, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2009-06-15

    Initial growth condition of AlN on sapphire substrate by HVPE was investigated. It was found that polarity of AlN was significantly affected by temperature even under the condition of AlCl{sub 3} pre-flow and that polarity was drastically changed from N-polarity to Al-polarity with increasing temperature around 1000 C. Polarity of AlN was easily controlled by growth temperature. By utilizing these findings and etching technique by alkaline solution, AlN nano-islands were successfully obtained on sapphire substrates. AlN nano-islands had mixture of trapezoid and column structure with 100 nm or less in diameter. Also it had epitaxial relation to sapphire substrates. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Black-blood native T1 mapping: Blood signal suppression for reduced partial voluming in the myocardium.

    Science.gov (United States)

    Weingärtner, Sebastian; Meßner, Nadja M; Zöllner, Frank G; Akçakaya, Mehmet; Schad, Lothar R

    2017-08-01

    To study the feasibility of black-blood contrast in native T1 mapping for reduction of partial voluming at the blood-myocardium interface. A saturation pulse prepared heart-rate-independent inversion recovery (SAPPHIRE) T1 mapping sequence was combined with motion-sensitized driven-equilibrium (MSDE) blood suppression for black-blood T1 mapping at 3 Tesla. Phantom scans were performed to assess the T1 time accuracy. In vivo black-blood and conventional SAPPHIRE T1 mapping was performed in eight healthy subjects and analyzed for T1 times, precision, and inter- and intraobserver variability. Furthermore, manually drawn regions of interest (ROIs) in all T1 maps were dilated and eroded to analyze the dependence of septal T1 times on the ROI thickness. Phantom results and in vivo myocardial T1 times show comparable accuracy with black-blood compared to conventional SAPPHIRE (in vivo: black-blood: 1562 ± 56 ms vs. conventional: 1583 ± 58 ms, P = 0.20); Using black-blood SAPPHIRE precision was significantly lower (standard deviation: 133.9 ± 24.6 ms vs. 63.1 ± 6.4 ms, P T1 time measurement was not possible. Significantly increased interobserver interclass correlation coefficient (ICC) (0.996 vs. 0.967, P = 0.011) and similar intraobserver ICC (0.979 vs. 0.939, P = 0.11) was obtained with the black-blood sequence. Conventional SAPPHIRE showed strong dependence on the ROI thickness (R(2) = 0.99). No such trend was observed using the black-blood approach (R(2) = 0.29). Black-blood SAPPHIRE successfully eliminates partial voluming at the blood pool in native myocardial T1 mapping while providing accurate T1 times, albeit at a reduced precision. Magn Reson Med 78:484-493, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  17. NEW OPTICAL SENSOR SUITE FOR ULTRAHIGH TEMPERATURE FOSSIL FUEL APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Russell G. May; Tony Peng; Tom Flynn

    2004-12-01

    Accomplishments during the Phase I of a program to develop and demonstrate technology for the instrumentation of advanced powerplants are described. Engineers from Prime Research, LC and Babcock and Wilcox Research Center collaborated to generate a list of potential applications for robust photonic sensors in existing and future boiler plants. From that list, three applications were identified as primary candidates for initial development and demonstration of high-temperature sensors in an ultrasupercritical power plant. A matrix of potential fiber optic sensor approaches was derived, and a data set of specifications for high-temperature optical fiber was produced. Several fiber optic sensor configurations, including interferometric (extrinsic and intrinsic Fabry-Perot interferometer), gratings (fiber Bragg gratings and long period gratings), and microbend sensors, were evaluated in the laboratory. In addition, progress was made in the development of materials and methods to apply high-temperature optical claddings to sapphire fibers, in order to improve their optical waveguiding properties so that they can be used in the design and fabrication of high-temperature sensors. Through refinements in the processing steps, the quality of the interface between core and cladding of the fibers was improved, which is expected to reduce scattering and attenuation in the fibers. Numerical aperture measurements of both clad and unclad sapphire fibers were obtained and used to estimate the reduction in mode volume afforded by the cladding. High-temperature sensors based on sapphire fibers were also investigated. The fabrication of an intrinsic Fabry-Perot cavity within sapphire fibers was attempted by the bulk diffusion of magnesium oxide into short localized segments of longer sapphire fibers. Fourier analysis of the fringes that resulted when the treated fiber was interrogated by a swept laser spectrometer suggested that an intrinsic cavity had been formed in the fiber. Also

  18. Graphene, conducting polymer and their composites as transparent and current spreading electrode in GaN solar cells

    Science.gov (United States)

    Mahala, Pramila; Kumar, Ajay; Nayak, Sasmita; Behura, Sanjay; Dhanavantri, Chenna; Jani, Omkar

    2016-04-01

    Understanding the physics of charge carrier transport at graphene/p-GaN interface is critical for achieving efficient device functionality. Currently, the graphene/p-GaN interface is being explored as light emitting diodes, however this interface can be probed as a potential photovoltaic cell. We report the intimate interfacing of mechanically exfoliated graphene (EG), conducting polymer (PEDOT:PSS) and composite of reduced graphene oxide (rGO) and PEDOT:PSS with a wide band gap p-GaN layer. To explore their potential in energy harvesting, three heterojunction devices such as: (i) EG/p-GaN/sapphire, (ii) PEDOT:PSS/p-GaN/sapphire and (iii) PEDOT:PSS(rGO)/p-GaN/sapphire are designed and their photovoltaic characteristics are examined. It is interesting to observe that the EG/p-GaN/sapphire solar cell exhibits high open-circuit voltage of 0.545 V with low ideality factor and reverse saturation current. However, improved short circuit current density (13.7 mA/cm2) is noticed for PEDOT:PSS/p-GaN/sapphire solar cell because of enhanced conductivity accompanied by high transmittance for PEDOT:PSS. Further, the low series resistance for PEDOT:PSS(rGO)/p-GaN/sapphire is observed suggesting that the PEDOT:PSS and rGO composite is well dispersed and exhibits low interfacial resistances with p-GaN. The present investigation leverages the potential of graphene, conducting polymer and their composites as dual capability of (a) transparent and current spreading electrode and (b) an active top layer to make an intimate contact with wide bandgap p-type GaN for possible prospect towards high performance diodes, switches and solar cells.

  19. Advanced dry etching studies for micro- and nano-systems

    DEFF Research Database (Denmark)

    Rasmussen, Kristian Hagsted

    for structuring of sapphire and many polymers. Metals and metal alloys have been structured by physical sputtering with argon ions in an ion beam etching system. The materials for which etch characteristics have been investigated are commonly used in device fabrication at DTU-Danchip. Ion beam etching was first...... and even contaminate the surface with metal flakes after resist removal. Ion beam etching has also been used for etching of steel without any problems with redeposition. For steel the etch rate was low which reduced the selectivity to the photo resist. Sapphire, a crystal of aluminum oxide, has a very low...

  20. Substrate impact on the low-temperature growth of GaN thin films by plasma-assisted atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kizir, Seda; Haider, Ali; Biyikli, Necmi, E-mail: biyikli@unam.bilkent.edu.tr [National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, Ankara 06800, Turkey and Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, Ankara 06800 (Turkey)

    2016-07-15

    Gallium nitride (GaN) thin films were grown on Si (100), Si (111), and c-plane sapphire substrates at 200 °C via hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD) using GaEt{sub 3} and N{sub 2}/H{sub 2} plasma as group-III and V precursors, respectively. The main aim of the study was to investigate the impact of substrate on the material properties of low-temperature ALD-grown GaN layers. Structural, chemical, and optical characterizations were carried out in order to evaluate and compare film quality of GaN on different substrates. X-ray reflectivity measurements showed film density values of 5.70, 5.74, and 5.54 g/cm{sup 3} for GaN grown on Si (100), Si (111), and sapphire, respectively. Grazing incidence x-ray diffraction measurements exhibited hexagonal wurtzite structure in all HCPA-ALD grown GaN samples. However, dominant diffraction peak for GaN films grown on Si and sapphire substrates were detected differently as (002) and (103), respectively. X-ray diffraction gonio scans measured from GaN grown on c-plane sapphire primarily showed (002) orientation. All samples exhibited similar refractive index values (∼2.17 at 632 nm) with 2–3 at. % of oxygen impurity existing within the bulk of the films. The grain size was calculated as ∼9–10 nm for GaN grown on Si (100) and Si (111) samples while it was ∼5 nm for GaN/sapphire sample. Root-mean-square surface roughness values found as 0.68, 0.76, and 1.83 nm for GaN deposited on Si (100), Si (111), and sapphire, respectively. Another significant difference observed between the samples was the film growth per cycle: GaN/sapphire sample showed a considerable higher thickness value when compared with GaN/Si samples, which might be attributed to a possibly more-efficient nitridation and faster nucleation of sapphire surface.

  1. Isotope-selective laser photodetachment for {sup 129}I accelerator mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Tone, E-mail: takahashi.ton@d.mbox.nagoya-u.ac.jp; Tomita, Hideki; Nakayama, Motoi; Adachi, Yoshitaka [Nagoya University (Japan); Sonnenschein, Volker [Johannes Gutenberg University (Germany); Iguchi, Tetsuo [Nagoya University (Japan); Wendt, Klaus [Johannes Gutenberg University (Germany)

    2013-04-15

    A pulsed injection-locked Ti:Sapphire laser and a negative ion laser ablation source are developed for compact accelerator mass spectrometry assisted by isotope-selective laser photodetachment. An output of about 60 mW at a repetition rate of 1 kHz is available using intracavity second-harmonic generation with a bandwidth of 20 MHz. A negative iodine ion pulse with a width of 100 ns is obtained by laser ablation of a NH{sub 4}I sample. The negative ion source and the injection-locked Ti:Sapphire laser are suitable for trace analysis of {sup 129}I.

  2. Development of resonance ionization in a supersonic gas-jet for studies of short-lived and long-lived radioactive nuclei

    Science.gov (United States)

    Takatsuka, Takaaki; Tomita, Hideki; Sonnenschein, Volker; Sonoda, Tetsu; Adachi, Yoshitaka; Sakamoto, Chika; Mita, Hiroki; Noto, Takuma; Ito, Chikara; Maeda, Shigetaka; Iguchi, Tetsuo; Wada, Michiharu; Wendt, Klaus; Moore, Iain

    2013-12-01

    High-resolution resonance ionization spectroscopy (RIS) is required for laser spectroscopy and trace analysis of short-lived and long-lived radioactive nuclei. We have proposed high-resolution resonance ionization spectroscopy in a gas jet combined with a narrow band-width injection-locked Ti:Sapphire laser. Resonance ionization of stable 93Nb in a gas jet was demonstrated using a broad bandwidth Ti:Sapphire laser. In addition, a setup for high-resolution RIS in a gas-jet was designed using numerical simulations of the gas-jet conditions based on computational fluid dynamics.

  3. Characterization of short-pulse oscillators by means of a high-dynamic-range autocorrelation measurement.

    Science.gov (United States)

    Braun, A; Rudd, J V; Cheng, H; Mourou, G; Kopf, D; Jung, I D; Weingarten, K J; Keller, U

    1995-09-15

    A high-dynamic-range autocorrelation technique was used to characterize the temporal pulse shape of ultrashort laser pulses produced from four separate oscillators. These lasers included two Kerr-lens mode-locked Ti:sapphire oscillators as well as a Nd:glass and a Ti:sapphire oscillator, each passively mode locked by an antiresonant Fabry-Perot semiconductor saturable absorber. It was shown that the Nd:glass oscillator supported a pulse that was temporally clean over 8 orders of magnitude.

  4. Insulator dielectric properties during irradiation and influence of RIED effect

    Energy Technology Data Exchange (ETDEWEB)

    Molla, J. (EURATOM-CIEMAT Association, Inst. Investigacion Basica, CIEMAT, Avda. Complutense, 22, E-28040, Madrid (Spain)); Ibarra, A. (EURATOM-CIEMAT Association, Inst. Investigacion Basica, CIEMAT, Avda. Complutense, 22, E-28040, Madrid (Spain)); Hodgson, E.R. (EURATOM-CIEMAT Association, Inst. Investigacion Basica, CIEMAT, Avda. Complutense, 22, E-28040, Madrid (Spain))

    1994-09-01

    The use of insulators for fusion applications is subject to considerable uncertainty due to the lack of a reliable database about the dielectric properties of insulator materials during irradiation at different frequencies. A set-up for the room-temperature measurement of these properties during electron irradiation at 15 GHz is described. Sapphire, spinel, beryllia and several alumina grades have been measured. Some very complex flux and fluence effects are observed. Several sapphire samples degraded by the RIED effect at 250 and 450 C are examined. ((orig.))

  5. Autonomous Motion Segmentation of Multiple Objects in Low Resolution Video Using Variational Level Sets

    Energy Technology Data Exchange (ETDEWEB)

    Moelich, M

    2003-11-18

    This report documents research that was done during a ten week internship in the Sapphire research group at the Lawrence Livermore National Laboratory during the Summer of 2003. The goal of the study was to develop an algorithm that is capable of isolating (segmenting) moving objects in low resolution video sequences. This capability is currently being developed by the Sapphire research group as the first stage in a longer term video data mining project. This report gives a chronological account of what ideas were tried in developing the algorithm and what was learned from each attempt. The final version of the algorithm, which is described in detail, gives good results and is fast.

  6. Note: A wide temperature range MOKE system with annealing capability

    Science.gov (United States)

    Chahil, Narpinder Singh; Mankey, G. J.

    2017-07-01

    A novel sample stage integrated with a longitudinal MOKE system has been developed for wide temperature range measurements and annealing capabilities in the temperature range 65 K < T < 760 K. The sample stage incorporates a removable platen and copper block with inserted cartridge heater and two thermocouple sensors. It is supported and thermally coupled to a cold finger with two sapphire bars. The sapphire based thermal coupling enables the system to perform at higher temperatures without adversely affecting the cryostat and minimizes thermal drift in position. In this system the hysteresis loops of magnetic samples can be measured simultaneously while annealing the sample in a magnetic field.

  7. Natural substrate lift-off technique for vertical light-emitting diodes

    Science.gov (United States)

    Lee, Chia-Yu; Lan, Yu-Pin; Tu, Po-Min; Hsu, Shih-Chieh; Lin, Chien-Chung; Kuo, Hao-Chung; Chi, Gou-Chung; Chang, Chun-Yen

    2014-04-01

    Hexagonal inverted pyramid (HIP) structures and the natural substrate lift-off (NSLO) technique were demonstrated on a GaN-based vertical light-emitting diode (VLED). The HIP structures were formed at the interface between GaN and the sapphire substrate by molten KOH wet etching. The threading dislocation density (TDD) estimated by transmission electron microscopy (TEM) was reduced to 1 × 108 cm-2. Raman spectroscopy indicated that the compressive strain from the bottom GaN/sapphire was effectively released through the HIP structure. With the adoption of the HIP structure and NSLO, the light output power and yield performance of leakage current could be further improved.

  8. A Substrate-Reclamation Technology for GaN-Based Lighting-Emitting Diodes Wafer

    Directory of Open Access Journals (Sweden)

    Shih-Yung Huang

    2017-03-01

    Full Text Available This study reports on the use of a substrate-reclamation technology for a gallium nitride (GaN-based lighting-emitting diode (LED wafer. There are many ways to reclaim sapphire substrates of scrap LED wafers. Compared with a common substrate-reclamation method based on chemical mechanical polishing, this research technology exhibits simple process procedures, without impairing the surface morphology and thickness of the sapphire substrate, as well as the capability of an almost unlimited reclamation cycle. The optical performances of LEDs on non-reclaimed and reclaimed substrates were consistent for 28.37 and 27.69 mcd, respectively.

  9. Enhanced magnetoresistance of Co/Cu(111) wedge superlattices grown by MBE

    Science.gov (United States)

    Xu, J.; Hickey, B. J.; Howson, M. A.; Greig, D.; Walker, M. J.; Wiser, N.

    1996-04-01

    We have grown epitaxial Co/Cu multilayer samples at different temperatures using MBE on sapphire (11 overline20)0 substrates with a 30 Å layer of Nb as a buffer, and find a remarkable correlation between the sharpness of X-ray rocking curves and the magnitude of the GMR. Whereas the peak GMR for our previous samples grown on GaAs was never greater than 26%, the maximum GMR of samples grown on sapphire under optimal growth conditions was as high as 50%.

  10. Optical trigger: a Cherenkov effect discriminator for high energy physics. Realisation and characterisation of thin films whose refractive index allow discrimination over a wide spectral range.; Le Trigger Optique: un discriminateur a effet Cherenkov pour la physique des particules. Realisation et caracterisation de couches minces dont l`indice de refraction autorise la discrimination sur un large domaine spectral

    Energy Technology Data Exchange (ETDEWEB)

    Delbart, A.

    1996-06-19

    The first part of this thesis sets the physical principles, and properties of actual Optical Triggers. For each of them, the cupel is sapphire made, and the external medium is liquid because of refractive index. The theory of Cherenkov emitted light cone explain how sapphire birefringence affects discrimination conditions.The second parts of the thesis (the main one) is focussed on study and realization of thin films for Optical Trigger. A layer characterization method has been developed by spectrophotometry, based on Perkin-Elmer laboratory device. Computerized simulation helped us to determine characteristics and limits of the studied device. (D.L.). Refs.

  11. Polarizer design for millimeter-wave plasma diagnostics

    DEFF Research Database (Denmark)

    Leipold, Frank; Salewski, Mirko; Jacobsen, Asger Schou

    2013-01-01

    by birefringent windows, the microwave receivers can be designed to be more compact at lower cost. Sapphire windows (a-cut) as well as grooved high density polyethylene windows can serve this purpose. The sapphire window can be designed such that the calculated transmission of the wave energy is better than 99......Radiation from magnetized plasmas is in general elliptically polarized. In order to convert the elliptical polarization to linear polarization, mirrors with grooved surfaces are currently employed in our collective Thomson scattering diagnostic at ASDEX Upgrade. If these mirrors can be substituted...

  12. Silicon integrated circuits part A : supplement 2

    CERN Document Server

    Kahng, Dawon

    1981-01-01

    Applied Solid State Science, Supplement 2: Silicon Integrated Circuits, Part A focuses on MOS device physics. This book is divided into three chapters-physics of the MOS transistor; nonvolatile memories; and properties of silicon-on-sapphire substrates devices, and integrated circuits. The topics covered include the short channel effects, MOSFET structures, floating gate devices, technology for nonvolatile semiconductor memories, sapphire substrates, and SOS integrated circuits and systems. The MOS capacitor, MIOS devices, and SOS process and device technology are also deliberated. This public

  13. Coherent anti-Stokes Raman scattering microscopy with a photonic crystal fiber based light source

    DEFF Research Database (Denmark)

    Paulsen, H.N.; Hilligsøe, Karen Marie; Thøgersen, J.

    2003-01-01

    A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup is demonstra......A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup...

  14. Silicon—a new substrate for GaN growth

    Indian Academy of Sciences (India)

    Generally, GaN-based devices are grown on silicon carbide or sapphire substrates. But these substrates are costly and insulating in nature and also are not available in large diameter. Silicon can meet the requirements for a low cost and conducting substrate and will enable integration of optoelectronic or high power ...

  15. Surface texturing of sialon ceramic by femtosecond pulsed laser

    CSIR Research Space (South Africa)

    Tshabalala, Lerato C

    2017-01-01

    Full Text Available AlONSi(sub3)N(sub4) ceramic using the Ti: Sapphire Femtosecond laser system was investigated. Parametric analysis was conducted using surface drilling, unidirectional and cross-hatching machining procedures performed on the substrate at a varied power...

  16. alumina phase transformation from thermal decomposition

    African Journals Online (AJOL)

    HOD

    for the foreseeable future, the most important types of nanoparticles which possess high specific surface area are simple oxides such as Al2O3, which are used in established applications [6], and for sapphire crystal growth [7]. Presently, alpha-alumina (α-Al2O3) has many uses in traditional and advanced ceramics. It is an.

  17. Investigations on the slope efficiency of a pulsed 2.8-µm Er3+:LiYF4 laser

    NARCIS (Netherlands)

    Pollnau, Markus; Spring, R.; Wittwer, S.; Lüthy, W.; Weber, H.P.

    1997-01-01

    A slope efficiency of 40% from an Er3+:LiYF4 laser is demonstrated under pulsed Ti:sapphire pumping at 973 nm. With reduction of the pump-pulse duration a significant decrease of the slope efficiency and an increase of the threshold is observed in the experiment and confirmed with high accuracy in a

  18. Kristiina Uslar Londoni klaasivõistluse finaalis

    Index Scriptorium Estoniae

    2006-01-01

    Londonis avati rahvusvahelise klaasikonkursi "The Bombay Sapphire Prize" 2006. aasta finalistide näitus. Eestit esindab Kristiina Uslar tööga "Data Turbine". Konkursi peaauhinna võitis hispaania kunstnik Jaune Plensa, parima uustulnuka auhinna inglise klaasikunstnik Laura Birdsall

  19. Picosecond optical nonlinearities in symmetrical and unsymmetrical ...

    Indian Academy of Sciences (India)

    We present our experimental results on the picosecond nonlinear optical. (NLO) studies of symmetrical and unsymmetrical phthalocyanines, examined using the. Z-scan technique. Both the open-aperture ... Z-scan measurements were performed using the amplified Ti:sapphire laser system. (LEGEND, Coherent) delivering ...

  20. High power AlGaN ultraviolet light emitters

    Science.gov (United States)

    Shatalov, Max; Sun, Wenhong; Jain, Rakesh; Lunev, Alex; Hu, Xuhong; Dobrinsky, Alex; Bilenko, Yuri; Yang, Jinwei; Garrett, Gregory A.; Rodak, Lee E.; Wraback, Michael; Shur, Michael; Gaska, Remis

    2014-06-01

    We present the analysis of the external quantum efficiency in AlGaN deep ultraviolet (DUV) light-emitting diodes (LEDs) on sapphire substrates and discuss factors affecting the output power of DUV LEDs. Performance of the LED is related to optimization of the device structure design and improvements of the epitaxial material quality.

  1. Microstructural analyses, magnetic and magneto-optic effects in high oriented BaFe12O19 thin films

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.

    2001-01-01

    Barium ferrite films applicable for data storage have been grown on sapphire substrate by pulsed laser deposition. BaFe12O19/Al2O3 films show a polycrystalline structure with high oriented perpendicular anisotropy. Large megneto-optic effects have been observed in the UV wavelength. The magnetic

  2. V V Raman is Emeritus Professor of Physics and Humanities at the ...

    Indian Academy of Sciences (India)

    edu http://en.wikipedia.org/wiki/Varadaraja_V. _Raman petty piece of charcoal; rubies, sapphires and emeralds would all be dark as the depths of hell. The effect of light on the world around us is of incredible variety. The magnificent aurora and.

  3. Biomarkers and Biological Spectral Imaging

    Science.gov (United States)

    2001-01-23

    1’ 22 using a solid state (10 W Coherent Verdi)-pumped, mode- locked , tunable Ti:sapphire laser (Coherent Mira 900) as excitation source. The pulse...because fluorescence was mainly obtained from the cheek pouch capillaries. Control cheek pouches contained a plexus of capillaries with uniform diameters

  4. Optoelectronic Properties and Structural Characterization of GaN Thick Films on Different Substrates through Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Wei-Kai Wang

    2017-01-01

    Full Text Available Approximately 4-μm-thick GaN epitaxial films were directly grown onto a GaN/sapphire template, sapphire, Si(111, and Si(100 substrates by high-temperature pulsed laser deposition (PLD. The influence of the substrate type on the crystalline quality, surface morphology, microstructure, and stress states was investigated by X-ray diffraction (XRD, photoluminescence (PL, atomic force microscopy (AFM, transmission electron microscopy (TEM, and Raman spectroscopy. Raman scattering spectral analysis showed a compressive film stress of −0.468 GPa for the GaN/sapphire template, whereas the GaN films on sapphire, Si(111, and Si(100 exhibited a tensile stress of 0.21, 0.177, and 0.081 GPa, respectively. Comparative analysis indicated the growth of very close to stress-free GaN on the Si(100 substrate due to the highly directional energetic precursor migration on the substrate’s surface and the release of stress in the nucleation of GaN films during growth by the high-temperature (1000 °C operation of PLD. Moreover, TEM images revealed that no significant GaN meltback (Ga–Si etching process was found in the GaN/Si sample surface. These results indicate that PLD has great potential for developing stress-free GaN templates on different substrates and using them for further application in optoelectronic devices.

  5. Thin Film Deposition of Boron Nitride by Femtosecond Laser Pulses with Different Wavelengths

    Science.gov (United States)

    Miyake, Hidekazu; Luculescu, Catalin; Sato, Shunichi

    2002-12-01

    Thin film deposition of hexagonal boron nitride was carried out using fundamental and second harmonic waves of a femtosecond Ti:sapphire laser. Morphological investigation of the deposited thin films showed that the number of fragments and the ablation threshold were smaller in the case of second harmonic wave ablation than fundamental wave ablation.

  6. Silicon—a new substrate for GaN growth

    Indian Academy of Sciences (India)

    Unknown

    obtained good results. Therefore, the use of compliant substrates for GaN growth seems to be promising, as the quality of material is comparable to that grown on SiC or sapphire. (IV) Patterning substrates by masking or etching the sub- strates or buffer layer is another low cost but highly effec- tive way to reduce the stress ...

  7. Meso-size Effect from Self-assembled Carbon Structures and Their Device Applications

    Science.gov (United States)

    2013-08-23

    Levendorf, A. W. Tsen , J. Park, and H. C. Choi, “Large Scale Metal-free Synthesis of Graphene on Sapphire and Transfer-free Device Fabrication...Nanoscale, 4, 3050-3054 (2012). [12]R. Havener, W. Tsen , H. C. Choi, and J. Park, “Laser-based imaging of individual carbon nanostructures,” (invited

  8. Phase diagram for droplet impact on superheated surfaces

    NARCIS (Netherlands)

    Staat, Erik-Jan; Tran, Tuan; Geerdink, B.M.; Riboux, G.; Sun, Chao; Gordillo, J.M.; Lohse, Detlef

    2015-01-01

    We experimentally determine the phase diagram for impacting ethanol droplets on a smooth, sapphire surface in the parameter space of Weber number We versus surface temperature T. We observe two transitions, namely the one towards splashing (disintegration of the droplet) with increasing We, and the

  9. Dielectric Waveguide lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Orlovic, V.A.; Pachenko, V.; Scherbakov, I.A.

    2007-01-01

    Our recent results on planar and channel waveguide fabrication and lasers in the dielectric oxide materials Ti:sapphire and rare-earth-ion-doped potassium yttrium double tungstate (KYW) are reviewed. We have employed waveguide fabrication methods such as liquid phase epitaxy and reactive ion etching

  10. 7TH International Workshop on Laser Physics (LPHYS󈨦) Berlin, Germany July 6-10, 1998 Program and Book of Abstracts: Volume 2.

    Science.gov (United States)

    1998-07-01

    7,8], dental and bone-like materials [I] it could be shown that sub-picosecond-pulse laser ablation leads to enhanced structuring quality... Coumarine or Rhodamine 6G dye lasers, Ti:sapphire, and Q- switched Alexandrite laser operating in visible spectral region had been used for the stone

  11. Optically-pumped lasing of semi-polar InGaN/GaN(1122) heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Strittmatter, A.; Teepe, M.; Yang, Z.; Chua, C.; Northrup, J.; Johnson, N.M. [Palo Alto Research Center, Palo Alto, CA (United States); Spiberg, P.; Brown, R.G.W. [Ostendo Technologies, Inc., Carlsbad, CA (United States); Ivantsov, V.; Syrkin, A.; Shapovalov, L.; Usikov, A. [TDI, Inc., an Oxford Instruments Company, Silver Spring, MD (United States)

    2010-07-15

    Results for long-wavelength emitters are presented for semi-polar InGaN/AlGaN/GaN heterostructures grown on GaN(11-22)/m-sapphire templates by metalorganic chemical vapor deposition. The semi-polar GaN layers were 10 to 25 {mu}m thick and grown by HVPE on sapphire substrates. X-ray diffraction measurements indicate high crystallographic quality that approaches that of GaN(0001) layers on sapphire. Growth studies on the semi-polar GaN templates established the high efficiency of indium incorporation into InGaN layers, with a wide growth-temperature window up to 800 C for green light emitting structures. Basic LEDs were fabricated with peak emission up to 527 nm wavelength. Further growth studies established conditions for growing reasonably smooth, undoped InGaN/GaN laser heterostructures suitable for optical pumping. Optically-pumped lasing was achieved at wavelengths from 400 nm up to 500 nm. The results demonstrate the viability of semi-polar GaN(11-22) on sapphire templates for long-wavelength nitride laser diodes (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Visual observation of gas hydrates nucleation and growth at a water - organic liquid interface

    Science.gov (United States)

    Stoporev, Andrey S.; Semenov, Anton P.; Medvedev, Vladimir I.; Sizikov, Artem A.; Gushchin, Pavel A.; Vinokurov, Vladimir A.; Manakov, Andrey Yu.

    2018-03-01

    Visual observation of nucleation sites of methane and methane-ethane-propane hydrates and their further growth in water - organic liquid - gas systems with/without surfactants was carried out. Sapphire Rocking Cell RCS6 with transparent sapphire cells was used. The experiments were conducted at the supercooling ΔTsub = 20.2 °C. Decane, toluene and crude oils were used as organics. Gas hydrate nucleation occurred on water - metal - gas and water - sapphire - organic liquid three-phase contact lines. At the initial stage of growth hydrate crystals rapidly covered the water - gas or water - organics interfaces (depending on the nucleation site). Further hydrate phase accrete on cell walls (sapphire surface) and into the organics volume. At this stage, growth was accompanied by water «drawing out» from under initial hydrate film formed at water - organic interface. Apparently, it takes place due to water capillary inflow in the reaction zone. It was shown that the hydrate crystal morphology depends on the organic phase composition. In the case of water-in-decane emulsion relay hydrate crystallization was observed in the whole sample, originating most likely due to the hydrate crystal intergrowth through decane. Contacts of such crystals with adjacent water droplets result in rapid hydrate crystallization on this droplet.

  13. Biaxial prestressing of brittle materials

    Science.gov (United States)

    Greszczuk, L.; Miller, R.; Netter, W.

    1970-01-01

    Strengthening of chemically consolidated zirconia with tungsten fibers, graphite fibers, sapphire whiskers, and silicon carbide whiskers is investigated. Addition of silicon carbide whiskers gives the highest increase in strength of zirconia at room and elevated temperatures. Prestressing with tungsten cables increases tensile strength and ductility

  14. Dynamic, Infrared Bandpass Filters Prepared from Polymer-Stabilized Cholesteric Liquid Crystals (Postprint)

    Science.gov (United States)

    2016-04-04

    sapphire slides were spun-coated with an alignment layer from a polyimide (PI- 2555, HD Microsystem ) or a nylon (Elvamide, DuPont), which was rubbed...crystal materials find a new order in biomedical applications,” Nat. Mater. 6, 929–938 (2007). 19. C. Binet, M. Mitov, and M. Mauzac, “Switchable

  15. 78 FR 25418 - Initiation of Antidumping and Countervailing Duty Administrative Reviews and Request for...

    Science.gov (United States)

    2013-05-01

    .... Ltd. LF Products Pte. Ltd. Stone Sapphire (HK) Limited Countervailing Duty Proceedings INDIA: Certain Hot-Rolled Carbon Steel Flat 1/1/12-12/31/12 Products,\\9\\ C-533-821 TURKEY: Welded Carbon Steel Pipe... duty order on Certain Hot-Rolled Carbon Steel Flat Products from India. See Initiation of Antidumping...

  16. Transient measurements with an ultrafast scanning tunneling microscope

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1998-01-01

    the transmission line while the change in delay time between pump beam (on the sample) and probe beam (on the probe) provides the temporal information. The investigated photoconductor sample is a low-temperature-grown GaAs layer placed on a sapphire substrate with a thin, semitransparent gold layer. In tunneling...

  17. Modeling Finite Deformations in Trigonal Ceramic Crystals with Lattice Defects

    Science.gov (United States)

    2010-02-08

    sapphire from 15 to 420 kbar. The effects of large anisotropic compressions. J. Phys. Chem. Solids 32, 2311–2330. Heuer, A.H., 1966. Deformation twinning in...Horstemeyer, M.F., Korellis, J.S., Grishabar, R.B., Mosher, D., 1998. High temperature sensitivity of notched AISI 304L stainless steel tests. Theor

  18. New class of compact diode pumped sub 10 fs lasers for biomedical applications

    DEFF Research Database (Denmark)

    Le, T.; Mueller, A.; Sumpf, B.

    2016-01-01

    Diode-pumping Ti: sapphire lasers promises a new approach to low-cost femtosecond light sources. Thus in recent years much effort has been taken just to overcome the quite low power and low beam qualities of available green diodes to obtain output powers of several hundred milliwatts from a fs-la...

  19. Development of Enhanced Performance Tunable RF Materials and Devices for On The Move (OTM) Communication Systems

    Science.gov (United States)

    2010-12-06

    Electron image 1 Zn Ka1 Nb La1 Bi Ma1 Figure 5. Elemental distribution on silicon wafers. CICTA CENTRO DE INVESTIGACIÓN EN...656) 688-4800, x4571 Electron image 1 Bi Ma1 Nb La1 Zn Ka1 Figure 9. Elemental distribution on sapphire wafers. 1.3

  20. Autocorrelation measurement of femtosecond laser pulses by use of a ZnSe two-photon detector array.

    Science.gov (United States)

    Gutierrez, A; Dorn, P; Zeller, J; King, D; Lester, L F; Rudolph, W; Sheik-Bahae, M

    1999-08-15

    We demonstrate autocorrelation measurements of 85-fs Ti:sapphire laser pulses, using a 32-pixel ZnSe detector array in a single-shot geometry. The two-photon photoconductor is fabricated by deposition of an array of interdigitated gold fingers on a single-crystal ZnSe substrate.

  1. Autocorrelation measurement of 6-fs pulses based on the two-photon-induced photocurrent in a GaAsP photodiode

    NARCIS (Netherlands)

    Ranka, J.K.; Gaeta, A.L.; Baltuska, A.; Pshenichnikov, M.S.; Wiersma, D.A.

    1997-01-01

    We experimentally characterize the two-photon response of a GaAsP photodiode by use of a femtosecond Ti:sapphire laser tuned below the diode bandgap. The photodiode is shown to be highly suitable for real-time second-order autocorrelation measurements of pulses as short as 6 fs in duration and with

  2. All-solid-state cavity-dumped sub-5-fs laser

    NARCIS (Netherlands)

    Baltuska, A.; Wei, Z; Pshenichnikov, M.S; Wiersma, D. A.; Szipocs, R.

    We discuss in detail a compact all-solid-state laser delivering sub-5-fs, 2-MW pulses at repetition rates up to 1 MHz. The shortest pulse generated thus far measures only 4.6 fs. The laser system employed is based on a cavity-dumped Ti:sapphire oscillator whose output is chirped in a single-mode

  3. Investigation of the structural defects in GaN thin films grown by organometallic vapor phase epitaxy

    Science.gov (United States)

    Choi, J.-H.; Lim, S.-J.; Cho, M.-S.; Cho, N.-H.; Chung, S.-J.; Sohn, C.-S.

    2003-02-01

    GaN thin films were prepared on {0001} planes of sapphire substrates by organometallic vapor phase epitaxy (OMVPE) techniques. The crystall orgaphic relation between the film and the substrate as well as the structural features of the defects in the film were investigated by transmission electron microscopy (TEM). Epitaxial relationship was observed in the GaN/sapphire heterostructure prepared in this investigation; (0001) GaN//(0001) sapphire;[ {01bar 10} ] GaN//[ {bar 12bar 10} ] sapphire. Dislocations of Burgers vectorbar b = {1/3} [ {2bar 1bar 10} ] were observed in the film; the propagation behavior of the dislocations exhibits a slip system{ {10bar 10} }< {2bar 1bar 10} rangle is operative in the film. Inversion domain boundary (IDB) facets lying parallel to{ {01bar 10} } and{ {bar 12bar 10} } planes were observed; the type of anti-site bonds (Ga-Ga, N-N) is altemate along these IDB planes, keeping the simple stoichiometry of the compound.

  4. Ultrafast optical dynamics of HITCI in ethylene glycol. A non-Markovian Brownian oscillator description

    NARCIS (Netherlands)

    de Boeij, Wim P; Pshenichnikov, Maxim S.; Duppen, Koos; Wiersma, Douwe A.

    1994-01-01

    Femtosecond photon echo, chirped four-wave mixing and pump-probe experiments are reported, using a 13 fs cavity-dumped Ti: sapphire laser for excitation. It is shown that the optical dynamics of HITCI in ethylene glycol occurs on distinctly different time scales. The ultrafast solvent response is

  5. A Novel Approach to Regeneration of Bone: Using Focused Ultrasound for the Spatiotemporal Patterning of Angiogenic and Osteogenic Factors

    Science.gov (United States)

    2012-04-01

    Vilaboa c , Oliver Kripfgans b , Brian Fowlkes b , Renny Franceschi a a Center for Craniofacial Regeneration, University of Michigan School of Dentistry ...fs-pulsed Ti:sapphire laser (Mai Tai Deep See, Spectra-Physics, Santa Clara, CA) for multiphoton excitation of the Hoechst 33258 and an argon laser

  6. Effect of process conditions on gain and loss in GaN:Eu cavities on different substrates

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.H.; Steckl, A.J. [Nanoelectronics Laboratory, University of Cincinnati, Cincinnati, Ohio 45221-0030 (United States)

    2008-01-15

    GaN:Eu laser cavities have been fabricated by MBE growth on several substrates. Gain and loss from Eu stimulated emission have been investigated as a function of several process parameters: Eu concentration, post-growth anneal and substrate (sapphire, silicon and glass). (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Towards optical attosecond pulses: broadband phase coherence between an ultrafast laser and OPO using lock-tozero CEO stabilization

    Directory of Open Access Journals (Sweden)

    Reid D. T.

    2013-03-01

    Full Text Available The carrier-envelope-offset frequencies of the pump, signal, idler and related sum-frequency mixing pulses have been locked to 0 Hz in a 20-fs-Ti:sapphire-pumped optical parametric oscillator, satisfying a critical prerequisite for optical attosecond pulse synthesis.

  8. Evaluation of the effects of solar radiation on glasses

    Science.gov (United States)

    Harada, Y.

    1981-01-01

    Four optical materials were exposed to simulated solar and particulate radiation in a space environment. Sapphire and fused silica experienced little change in transmittance while optical crown glass and ultra low expansion glass darkened appreciably. A complete analysis of the 500 hour simulated space exposure test was conducted. Additionally, studies were performed to aid in sample selection for a 100 hour simulated exposure test.

  9. Efficiency of erbium 3-µm crystal and fiber lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Spring, R.; Ghisler, C.; Wittwer, S.; Lüthy, W.; Weber, H.P.

    1996-01-01

    The population dynamics of erbium 3-μm crystal and fiber lasers are compared experimentally and theoretically. Laser slope efficiencies of 40% in Er:LiYF4 and 23% in a fluorozirconate fiber are experimentally demonstrated under Ti:sapphire pumping. These are both to our knowledge the highest values

  10. Mechanical and Microstructural Evaluation of Barium Strontium Titanate Thin Films for Improved Antenna Performance and Reliability

    National Research Council Canada - National Science Library

    Hubbard, C

    1999-01-01

    Ferroelectric barium strontium titanate (Ba(1-x)SrxTiO3 BSTO) films of 1-micron nominal thickness were deposited on single crystals of sapphire and electroded substrates at substrate temperatures varying from 30 deg C to 700 deg C...

  11. Comments on a peak of AlxGa1-xN observed by infrared reflectance

    Science.gov (United States)

    Marx, G.; Engelbrecht, J. A. A.; Lee, M. E.; Wagener, M. C.; Henry, A.

    2016-05-01

    AlxGa1-xN epilayers, grown on c-plane oriented sapphire substrates by metal organic chemical vapour deposition (MOCVD), were evaluated using FTIR infrared reflectance spectroscopy. A peak at ∼850 cm-1 in the reflectance spectra, not reported before, was observed. Possible origins for this peak are considered and discussed.

  12. Growth of single-crystal gallium nitride

    Science.gov (United States)

    Clough, R.; Richman, D.; Tietjen, J.

    1970-01-01

    Use of ultrahigh purity ammonia prevents oxygen contamination of GaN during growth, making it possible to grow the GaN at temperatures as high as 825 degrees C, at which point single crystal wafers are deposited on /0001/-oriented sapphire surfaces.

  13. Giant magnetoresistance of dissymmetrical Co/Au multilayers

    Science.gov (United States)

    Kolb, E.; Walker, M. J.; Vélu, E.; Howson, M. A.; Veillet, P.; Greig, D.; Renard, J. P.; Dupas, C.

    1996-04-01

    Results are presented for the magnetoresistance (MR) of sapphire/Nb 3/Cu 3/Au 8/(Co/Au 8) n dissymmetrical multilayers built by alternating a 0.3 nm discontinuous Co layer with a 0.7 nm continuous one. The observed enhanced MR is related to a higher spin scattering asymmetry for the granular Co layers.

  14. Candela photo-injector experimental results

    CERN Document Server

    Travier, C; Cayla, J N; Leblond, B; Georges, P; Thomas, P; Travier, C; Boy, L; Cayla, J N; Leblond, B; Georges, P; Thomas, P

    1995-01-01

    The CANDELA photo-injector is a two cell S-band photo-injector. The copper cathode is illuminated by a 500 fs Ti:sapphire laser. This paper presents energy spectrum measurements of the dark current and intense electron emission that occurs when the laser power density is very high.

  15. Weibull Analysis and Area Scaling for Infrared Window Materials (U)

    Science.gov (United States)

    2016-08-01

    given for the ring-on-ring test configuration by Equation 6 and for the pressure on ring configuration by Equation 7. The reference area o is chosen...Linevsky, J. W. Giles, T. A. Kennedy, M. Fatemi, D. R. Black, and K. P. D. Lagerlöf. “ Neutron Irradiation for Sapphire Compressive Strengthening: II

  16. Manufacturing Technology Development of Advanced Components for High Power Solid State Lasers

    Science.gov (United States)

    2010-07-19

    controlled KTiOP04 optical parametric oscillator," Opt. Lett. 32, 274-276 (2007). [2] P. B. Phua, B. S. Tan, R. F. Wu, K. S. Lai, L. Chia , E. Lau...ultrafast seed laser, 1st amplifier stage, 2 a amplifier stage, and beam characterization equipment. 4. Ti:Sapphire Laser Oscillator, Pre-Amplifier, and

  17. Transmission measurement of the photonic band gap of GaN photonic crystal slabs

    NARCIS (Netherlands)

    Caro, J.; Roeling, E.M.; Rong, B.; Nguyen, H.M.; Van der Drift, E.W.J.M.; Rogge, S.; Karouta, F.; Van der Heijden, R.W.; Salemink, H.W.M.

    2008-01-01

    A high-contrast-ratio (30 dB) photonic band gap in the near-infrared transmission of hole-type GaN two-dimensional photonic crystals (PhCs) is reported. These crystals are deeply etched in a 650 nm thick GaN layer grown on sapphire. A comparison of the measured spectrum with finite difference time

  18. Radar Imaging of Building Interiors using Sparse Reconstruction

    NARCIS (Netherlands)

    Rossum, W.L. van; Wit, J.J.M. de; Tan, R.G.

    2012-01-01

    At TNO an innovative concept to obtain inside building awareness with stand-off, through-the-wall radar has been developed: SAPPHIRE. The system concept exploits particular phase behavior in the 3D radar data to extract dominant scatterers inside a building. These scatterers can be reconstructed

  19. Thermal resistance of indium coated sapphire–copper contacts below 0.1K

    CERN Document Server

    Eisel, T; Koettig, T

    2014-01-01

    High thermal resistances exist at ultra-low temperatures for solid-solid interfaces. This is especially true for pressed metal-sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1 K. Consequently, it is difficult to predict the thermal resistance of pressed metal-sapphire joints at temperatures below 1 K. In this paper the thermal resistances across four different copper-sapphire-copper sandwiches are presented in a temperature range between 30 mK and 100 mK. The investigated sandwiches feature either rough or polished sapphire discs (empty set 20 mm x 1.5 mm) to investigate the phonon scattering at the bo...

  20. Red-IR stimulated luminescence in K-feldspar: Single or multiple trap origin?

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Jain, Mayank; Tidemand-Lichtenberg, Peter

    2012-01-01

    We investigate on the origins of the infra-red stimulated luminescence (IRSL) signals in 3 potassium feldspars based on IR-red spectroscopy (700–1050 nm) using a fiber-coupled tunable Ti:Sapphire laser, in combination with different thermal and optical (pre)treatments of the samples. We also...