Growth Related Carrier Mobility Enhancement of Pentacene Thin-Film Transistors with High-k Oxide Gate Dielectric

International Nuclear Information System (INIS)

Ai-Fang, Yu; Qiong, Qi; Peng, Jiang; Chao, Jiang

2009-01-01

Carrier mobility enhancement from 0.09 to 0.59 cm 2 /Vs is achieved for pentacene-based thin-film transistors (TFTs) by modifying the HfO 2 gate dielectric with a polystyrene (PS) thin film. The improvement of the transistor's performance is found to be strongly related to the initial film morphologies of pentacene on the dielectrics. In contrast to the three-dimensional island-like growth mode on the HfO 2 surface, the Stranski-Krastanov growth mode on the smooth and nonpolar PS/HfO 2 surface is believed to be the origin of the excellent carrier mobility of the TFTs. A large well-connected first monolayer with fewer boundaries is formed via the Stranski–Krastanov growth mode, which facilitates a charge transport parallel to the substrate and promotes higher carrier mobility. (cross-disciplinary physics and related areas of science and technology)

Tuning carrier mobility of phosphorene nanoribbons by edge passivation and strain

International Nuclear Information System (INIS)

Zhang, Xiaoou; Li, Qingfang; Xu, Bo; Wan, Bo; Yin, Jiang; Wan, X.G.

2016-01-01

Using first-principles calculations, we have studied the effects of different edge passivation groups on the carrier mobility of the phosphorene nanoribbons (PNRs) and strain effect on the transport property in passivated PNRs. The numerical results show that the size-dependent carrier mobility of passivated PNRs is not very sensitive to the different passivation groups, such as hydrogen (H), fluorine (F) and chlorine (Cl), but strongly associated with the orientation of nanoribbons. Passivated armchair-PNR has much larger carrier mobility than passivated zigzag-PNR at the similar ribbon width. With increasing ribbon width, the electron mobility of passivated PNRs can be further enhanced. We also find that the anisotropy of carrier mobility in passivated PNRs can be reversed by applying tensile strain resulting from order switching of the conduction bands around Fermi level.

Tuning carrier mobility of phosphorene nanoribbons by edge passivation and strain

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaoou [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China); Li, Qingfang, E-mail: qingfangli@nuist.edu.cn [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Xu, Bo, E-mail: xubonju@gmail.com [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Wan, Bo [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China); Yin, Jiang [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Wan, X.G. [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China)

2016-02-05

Using first-principles calculations, we have studied the effects of different edge passivation groups on the carrier mobility of the phosphorene nanoribbons (PNRs) and strain effect on the transport property in passivated PNRs. The numerical results show that the size-dependent carrier mobility of passivated PNRs is not very sensitive to the different passivation groups, such as hydrogen (H), fluorine (F) and chlorine (Cl), but strongly associated with the orientation of nanoribbons. Passivated armchair-PNR has much larger carrier mobility than passivated zigzag-PNR at the similar ribbon width. With increasing ribbon width, the electron mobility of passivated PNRs can be further enhanced. We also find that the anisotropy of carrier mobility in passivated PNRs can be reversed by applying tensile strain resulting from order switching of the conduction bands around Fermi level.

Determination of Charge-Carrier Mobility in Disordered Thin-Film Solar Cells as a Function of Current Density

Science.gov (United States)

Mäckel, Helmut; MacKenzie, Roderick C. I.

2018-03-01

Charge-carrier mobility is a fundamental material parameter, which plays an important role in determining solar-cell efficiency. The higher the mobility, the less time a charge carrier will spend in a device and the less likely it is that it will be lost to recombination. Despite the importance of this physical property, it is notoriously difficult to measure accurately in disordered thin-film solar cells under operating conditions. We, therefore, investigate a method previously proposed in the literature for the determination of mobility as a function of current density. The method is based on a simple analytical model that relates the mobility to carrier density and transport resistance. By revising the theoretical background of the method, we clearly demonstrate what type of mobility can be extracted (constant mobility or effective mobility of electrons and holes). We generalize the method to any combination of measurements that is able to determine the mean electron and hole carrier density, and the transport resistance at a given current density. We explore the robustness of the method by simulating typical organic solar-cell structures with a variety of physical properties, including unbalanced mobilities, unbalanced carrier densities, and for high or low carrier trapping rates. The simulations reveal that near VOC and JSC , the method fails due to the limitation of determining the transport resistance. However, away from these regions (and, importantly, around the maximum power point), the method can accurately determine charge-carrier mobility. In the presence of strong carrier trapping, the method overestimates the effective mobility due to an underestimation of the carrier density.

Suppressed carrier density for the patterned high mobility two-dimensional electron gas at γ-Al2O3/SrTiO3 heterointerfaces

DEFF Research Database (Denmark)

Niu, Wei; Gan, Yulin; Christensen, Dennis Valbjørn

2017-01-01

The two-dimensional electron gas (2DEG) at the non-isostructural interface between spinel γ-Al2O3 and perovskite SrTiO3 is featured by a record electron mobility among complex oxide interfaces in addition to a high carrier density up to the order of 1015 cm-2. Herein, we report on the patterning...... is found to be approximately 3×1013 cm-2, much lower than that of the unpatterned sample (~1015 cm-2). Remarkably, a high electron mobility of approximately 3,600 cm2V-1s-1 was obtained at low temperatures for the patterned 2DEG at a carrier density of ~ 7×1012 cm-2, which exhibits clear Shubnikov-de Hass...... quantum oscillations. The patterned high-mobility 2DEG at the γ-Al2O3/SrTiO3 interface paves the way for the design and application of spinel/perovskite interfaces for high-mobility all-oxide electronic devic...

Two-frequency method for measuring Hall emf in high-resistive materials with charge-carrier low mobility

International Nuclear Information System (INIS)

Aleksandrov, A.L.; Vedeneev, A.S.; Gulyaev, I.B.; Zhdan, A.G.

1982-01-01

A facility for measuring Hall emf in high-resistive materials with low mobility of charge carriers by the two-frequency method using digital synchronous integration is described. The facility permits to detect the minimum Hall emf approxamatety equat to 5 μV at approximatety equal to 1 T Ohm of the investigated.sample resistance during the measuring time of approximately equal to 2000 s. Sensitivity by Hall mobility makes up >= 0.01 cm 2 /Vxs at the same measuring time. Measuring results of the Hall emf on GaAs monocrystals, CdSe films and island film of gold are presented

Disorder effect on carrier mobility in Fullerene organic semiconductor

International Nuclear Information System (INIS)

Mendil, N; Daoudi, M; Berkai, Z; Belghachi, A

2015-01-01

The critical factor that limits the efficiencies of organic electronic devices is the low charge carrier mobility which is attributed to disorder in organic films. In this context, we have studied the effects of disorder on carrier mobility in organic Schottky diode of electrons for the fullerene (C 60 ). Our results show that the mobility is sensitive probes of structural phase transitions and order-disorder underlying C 60 . Where it is one reason behind the low mobility which it take as value 1.4x10 -2 cm 2 /V.s above critical temperature Tc =289K. (paper)

Charge carrier mobility in thin films of organic semiconductors by the gated van der Pauw method

Science.gov (United States)

Rolin, Cedric; Kang, Enpu; Lee, Jeong-Hwan; Borghs, Gustaaf; Heremans, Paul; Genoe, Jan

2017-01-01

Thin film transistors based on high-mobility organic semiconductors are prone to contact problems that complicate the interpretation of their electrical characteristics and the extraction of important material parameters such as the charge carrier mobility. Here we report on the gated van der Pauw method for the simple and accurate determination of the electrical characteristics of thin semiconducting films, independently from contact effects. We test our method on thin films of seven high-mobility organic semiconductors of both polarities: device fabrication is fully compatible with common transistor process flows and device measurements deliver consistent and precise values for the charge carrier mobility and threshold voltage in the high-charge carrier density regime that is representative of transistor operation. The gated van der Pauw method is broadly applicable to thin films of semiconductors and enables a simple and clean parameter extraction independent from contact effects. PMID:28397852

Influence of packing motives on charge Carrier mobility in perylene tetracarboxdiimide derivatives

Energy Technology Data Exchange (ETDEWEB)

May, Falk; Andrienko, Denis [Max-Planck Institute for Polymer Research, Mainz (Germany); Marcon, Valentina [Center of Smart Interfaces, Darmstadt (Germany)

2010-07-01

Discotic mesophases are known for their ability to self-assemble into columnar structures and can serve as semiconducting molecular wires. Charge carrier mobility along these wires strongly depends on molecular packing which is controlled by intermolecular interactions. In this work we compare the influence of side chains on the packing motives of perylene tetracarboxdiimide (PDI) derivatives. Two different (alkyl and glycol) side chains are considered. We first establish how the packing of side chains affects the molecular orientation within the columns using molecular dynamics. Then, using the high temperature non-adiabatic limit of Marcus theory for hopping rates and solving the rate equation for charge transport, we analyze the link between the secondary structure and charge carrier mobility. This analysis eventually provides a pathway to rational design of columnar assemblies of PDI derivatives with high charge mobilities.

Large Modulation of Charge Carrier Mobility in Doped Nanoporous Organic Transistors

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fengjiao [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Dai, Xiaojuan [Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Zhu, Weikun [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Chung, Hyunjoong [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Diao, Ying [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA

2017-05-10

Molecular doping of organic electronics has shown promise to sensitively modulate important device metrics. One critical challenge is the disruption of structure order upon doping of highly crystalline organic semiconductors, which significantly reduces the charge carrier mobility. This paper demonstrates a new method to achieve large modulation of charge carrier mobility via channel doping without disrupting the molecular ordering. Central to the method is the introduction of nanopores into the organic semiconductor thin films via a simple and robust templated meniscus-guided coating method. Using this method, the charge carrier mobility of C8-benzothieno[3,2-b]benzothiophene transistors is boosted by almost sevenfold. This paper further demonstrates enhanced electron transport by close to an order of magnitude in a diketopyrrolopyrrole-based donor–acceptor polymer. Combining spectroscopic measurements, density functional theory calculations, and electrical characterizations, the doping mechanism is identified as partial-charge-transfer induced trap filling. The nanopores serve to enhance the dopant/organic semiconductor charge transfer reaction by exposing the π-electrons to the pore wall.

Achieving high carrier mobility exceeding 70 cm2/Vs in amorphous zinc tin oxide thin-film transistors

Science.gov (United States)

Kim, Sang Tae; Shin, Yeonwoo; Yun, Pil Sang; Bae, Jong Uk; Chung, In Jae; Jeong, Jae Kyeong

2017-09-01

This paper proposes a new defect engineering concept for low-cost In- and Ga-free zinc tin oxide (ZTO) thin-film transistors (TFTs). This concept is comprised of capping ZTO films with tantalum (Ta) and a subsequent modest thermal annealing treatment at 200 °C. The Ta-capped ZTO TFTs exhibited a remarkably high carrier mobility of 70.8 cm2/Vs, low subthreshold gate swing of 0.18 V/decade, threshold voltage of -1.3 V, and excellent ION/OFF ratio of 2 × 108. The improvement (> two-fold) in the carrier mobility compared to the uncapped ZTO TFT can be attributed to the effective reduction of the number of adverse tailing trap states, such as hydroxyl groups or oxygen interstitial defects, which stems from the scavenging effect of the Ta capping layer on the ZTO channel layer. Furthermore, the Ta-capped ZTO TFTs showed excellent positive and negative gate bias stress stabilities. [Figure not available: see fulltext.

Large enhancements of thermopower and carrier mobility in quantum dot engineered bulk semiconductors.

Science.gov (United States)

Liu, Yuanfeng; Sahoo, Pranati; Makongo, Julien P A; Zhou, Xiaoyuan; Kim, Sung-Joo; Chi, Hang; Uher, Ctirad; Pan, Xiaoqing; Poudeu, Pierre F P

2013-05-22

The thermopower (S) and electrical conductivity (σ) in conventional semiconductors are coupled adversely through the carriers' density (n) making it difficult to achieve meaningful simultaneous improvements in both electronic properties through doping and/or substitutional chemistry. Here, we demonstrate the effectiveness of coherently embedded full-Heusler (FH) quantum dots (QDs) in tailoring the density, mobility, and effective mass of charge carriers in the n-type Ti(0.1)Zr(0.9)NiSn half-Heusler matrix. We propose that the embedded FH QD forms a potential barrier at the interface with the matrix due to the offset of their conduction band minima. This potential barrier discriminates existing charge carriers from the conduction band of the matrix with respect to their relative energy leading to simultaneous large enhancements of the thermopower (up to 200%) and carrier mobility (up to 43%) of the resulting Ti(0.1)Zr(0.9)Ni(1+x)Sn nanocomposites. The improvement in S with increasing mole fraction of the FH-QDs arises from a drastic reduction (up to 250%) in the effective carrier density coupled with an increase in the carrier's effective mass (m*), whereas the surprising enhancement in the mobility (μ) is attributed to an increase in the carrier's relaxation time (τ). This strategy to manipulate the transport behavior of existing ensembles of charge carriers within a bulk semiconductor using QDs is very promising and could pave the way to a new generation of high figure of merit thermoelectric materials.

Charge-carrier mobilities in disordered semiconducting polymers: effects of carrier density and electric field [refereed

NARCIS (Netherlands)

Meisel, K.D.; Pasveer, W.F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P.A.; Blom, P.W.M.; Leeuw, de D.M.; Michels, M.A.J.

2006-01-01

We model charge transport in disordered semiconducting polymers by hopping of charge carriers on a square lattice of sites with Gaussian on-site energy disorder, using Fermi-Dirac statistics. From numerically exact solns. of the Master equation, we study the dependence of the charge-carrier mobility

Monolayer CS as a metal-free photocatalyst with high carrier mobility and tunable band structure: a first-principles study

Science.gov (United States)

Yang, Xiao-Le; Ye, Xiao-Juan; Liu, Chun-Sheng; Yan, Xiao-Hong

2018-02-01

Producing hydrogen fuel using suitable photocatalysts from water splitting is a feasible method to harvest solar energy. A desired photocatalyst is expected to have suitable band gap, moderate band edge position, and high carrier mobility. By employing first-principles calculations, we explore a α-CS monolayer as a metal-free efficient photocatalyst. The α-CS monolayer shows good energetic, dynamic, and thermal stabilities and is insoluble in water, suggesting its experimental practicability. Monolayer and bilayer α-CS present not only appropriate band gaps for visible and ultraviolet light absorption but also moderate band alignments with water redox potentials in pH neutral water. Remarkably, the α-CS monolayer exhibits high (up to 8453.19 cm2 V-1s-1 for hole) and anisotropic carrier mobility, which is favorable to the migration and separation of photogenerated carriers. In addition, monolayer α-CS experiences an interesting semiconductor-metal transition by applying uniaxial strain and external electric field. Moreover, α-CS under certain strain and electric field is still dynamically stable with the absence of imaginary frequencies. Furthermore, we demonstrate that the graphite (0 0 1) surface is a potential substrate for the α-CS growth with the intrinsic properties of α-CS maintaining. Therefore, our results could pave the way for the application of α-CS as a promising photocatalyst.

A self-consistent first-principle based approach to model carrier mobility in organic materials

International Nuclear Information System (INIS)

Meded, Velimir; Friederich, Pascal; Symalla, Franz; Neumann, Tobias; Danilov, Denis; Wenzel, Wolfgang

2015-01-01

Transport through thin organic amorphous films, utilized in OLEDs and OPVs, has been a challenge to model by using ab-initio methods. Charge carrier mobility depends strongly on the disorder strength and reorganization energy, both of which are significantly affected by the details in environment of each molecule. Here we present a multi-scale approach to describe carrier mobility in which the materials morphology is generated using DEPOSIT, a Monte Carlo based atomistic simulation approach, or, alternatively by molecular dynamics calculations performed with GROMACS. From this morphology we extract the material specific hopping rates, as well as the on-site energies using a fully self-consistent embedding approach to compute the electronic structure parameters, which are then used in an analytic expression for the carrier mobility. We apply this strategy to compute the carrier mobility for a set of widely studied molecules and obtain good agreement between experiment and theory varying over several orders of magnitude in the mobility without any freely adjustable parameters. The work focuses on the quantum mechanical step of the multi-scale workflow, explains the concept along with the recently published workflow optimization, which combines density functional with semi-empirical tight binding approaches. This is followed by discussion on the analytic formula and its agreement with established percolation fits as well as kinetic Monte Carlo numerical approaches. Finally, we skatch an unified multi-disciplinary approach that integrates materials science simulation and high performance computing, developed within EU project MMM@HPC

Importance of polaron effects for charge carrier mobility above and ...

Indian Academy of Sciences (India)

Orifjon Ganiev

2017-05-30

May 30, 2017 ... sizes and effective masses are large polarons. According ... nating metallic and insulating domains with mobile ... The mobile polaronic carriers are con- ..... [51] T Kondo, Y Hamaya, A D Palczewski, T Takeuchi, J S Wen,.

Towards high charge carrier mobilities by rational design of organic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Andrienko, Denis; Ruehle, Victor; Baumeier, Bjoern; Vehoff, Thorsten; Lukyanov, Alexander; Kremer, Kurt [Max Planck Institute for Polymer Research, Mainz (Germany); Marcon, Valentina [Technische Universitaet Darmstadt (Germany); Kirkpatrick, James; Nelson, Jenny [Imperial College London (United Kingdom); Lennartz, Christian [BASF AG, Ludwigshafen (Germany)

2010-07-01

The role of material morphology on charge carrier mobility in partially disordered organic semiconductors is discussed for several classes of materials: derivatives of hexabenzocoronenens, perylenediimides, triangularly-shaped polyaromatic hydrocarbons, and Alq{sub 3}. Simulations are performed using a package developed by Imperial College, London and Max Planck Institute for Polymer Research, Mainz (votca.org). This package combines several techniques into one scheme: quantum chemical methods for the calculation of molecular electronic structures and reorganization energies; molecular dynamics and systematic coarse-graining approaches for simulation of self-assembly and relative positions and orientations of molecules on large scales; kinetic Monte Carlo and master equation for studies of charge transport.

Intrinsic carrier mobility extraction based on a new quasi-analytical model for graphene field-effect transistors

International Nuclear Information System (INIS)

Wang, Shaoqing; Jin, Zhi; Muhammad, Asif; Peng, Songang; Huang, Xinnan; Zhang, Dayong; Shi, Jingyuan

2016-01-01

The most common method of mobility extraction for graphene field-effect transistors is proposed by Kim. Kim’s method assumes a constant mobility independent of carrier density and gets the mobility by fitting the transfer curves. However, carrier mobility changes with the carrier density, leading to the inaccuracy of Kim’s method. In our paper, a new and more accurate method is proposed to extract mobility by fitting the output curves at a constant gate voltage. The output curves are fitted using several kinds of current–voltage models. Besides the models in the literature, we present a modified model, which takes into account not only the quantum capacitance, contact resistance, but also a modified drift velocity-field relationship. Comparing with the other models, this new model can fit better with our experimental data. The dependence of carrier intrinsic mobility on carrier density is obtained based on this model. (paper)

Enhancement of carrier mobility in all-inkjet-printed organic thin-film transistors using a blend of poly(3-hexylthiophene) and carbon nanoparticles

International Nuclear Information System (INIS)

Lin, Chih-Ting; Hsu, Chun-Hao; Chen, Iu-Ren; Lee, Chang-Hung; Wu, Wen-Jung

2011-01-01

To enhance the carrier mobility of all-inkjet-printed organic thin film transistors, we fabricated devices that incorporated poly(3-hexylthiophene) (P3HT) and carbon nanoparticles (CNPs). The fabricated devices had an on/off ratio of 10 4 , which is one order less than that of pristine organic thin-film transistors (OTFTs). The maximum carrier mobility as high as 0.053 cm 2 /V-s was achieved for a CNP/P3HT weight-weight ratio of 7/100. This degree of mobility is 10 times greater than average mobility of pristine P3HT-OTFTs. X-ray diffraction and scanning electron microscopy images reveal that the carrier mobility was enhanced by reducing the injection barrier and enhancing the carrier injection. This work demonstrates the feasibility of all-inkjet-printed OTFT technology.

Measuring the lateral charge-carrier mobility in metal-insulator-semiconductor capacitors via Kelvin-probe.

Science.gov (United States)

Milotti, Valeria; Pietsch, Manuel; Strunk, Karl-Philipp; Melzer, Christian

2018-01-01

We report a Kelvin-probe method to investigate the lateral charge-transport properties of semiconductors, most notably the charge-carrier mobility. The method is based on successive charging and discharging of a pre-biased metal-insulator-semiconductor stack by an alternating voltage applied to one edge of a laterally confined semiconductor layer. The charge carriers spreading along the insulator-semiconductor interface are directly measured by a Kelvin-probe, following the time evolution of the surface potential. A model is presented, describing the device response for arbitrary applied biases allowing the extraction of the lateral charge-carrier mobility from experimentally measured surface potentials. The method is tested using the organic semiconductor poly(3-hexylthiophene), and the extracted mobilities are validated through current voltage measurements on respective field-effect transistors. Our widely applicable approach enables robust measurements of the lateral charge-carrier mobility in semiconductors with weak impact from the utilized contact materials.

Measuring the lateral charge-carrier mobility in metal-insulator-semiconductor capacitors via Kelvin-probe

Science.gov (United States)

Milotti, Valeria; Pietsch, Manuel; Strunk, Karl-Philipp; Melzer, Christian

2018-01-01

We report a Kelvin-probe method to investigate the lateral charge-transport properties of semiconductors, most notably the charge-carrier mobility. The method is based on successive charging and discharging of a pre-biased metal-insulator-semiconductor stack by an alternating voltage applied to one edge of a laterally confined semiconductor layer. The charge carriers spreading along the insulator-semiconductor interface are directly measured by a Kelvin-probe, following the time evolution of the surface potential. A model is presented, describing the device response for arbitrary applied biases allowing the extraction of the lateral charge-carrier mobility from experimentally measured surface potentials. The method is tested using the organic semiconductor poly(3-hexylthiophene), and the extracted mobilities are validated through current voltage measurements on respective field-effect transistors. Our widely applicable approach enables robust measurements of the lateral charge-carrier mobility in semiconductors with weak impact from the utilized contact materials.

Importance of polaron effects for charge carrier mobility above and ...

Indian Academy of Sciences (India)

It is shown that the scattering of polaronic charge carriers and bosonic Cooper pairs at acoustic and optical phonons are responsible for the charge carrier mobility above and below the PG temperature. We show that the energy scales of the binding energies of large polarons and polaronic Cooper pairs can be identified by ...

Mobility Analysis for Inter-Site Carrier Aggregation in LTE Heterogeneous Networks

DEFF Research Database (Denmark)

Barbera, Simone; Pedersen, Klaus I.; Michaelsen, Per Henrik

2013-01-01

In this paper we analyze the mobility performance for an LTE Heterogeneous Network with macro and pico cells deployed on different carriers. Cases with/without downlink inter-site carrier aggregation are investigated. Extensive system level simulations are exploited to quantify the performance...

Carrier mobility and scattering lifetime in electric double-layer gated few-layer graphene

Energy Technology Data Exchange (ETDEWEB)

Piatti, E.; Galasso, S.; Tortello, M.; Nair, J.R.; Gerbaldi, C. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Bruna, M.; Borini, S. [Istituto Nazionale di Ricerca Metrologica (INRIM), 10135 Torino (Italy); Daghero, D. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Gonnelli, R.S., E-mail: renato.gonnelli@polito.it [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy)

2017-02-15

Highlights: • We fabricated few-layer graphene FETs by mechanical exfoliation and standard microfabrication techniques. • We employed a Li-TFSI based ion gel to induce carrier densities as high as ≈6e14 e{sup −}/cm{sup 2} in the devices' channel. • We found a strong asymmetry in the sheet conductance and mobility doping dependences between electron and hole doping. • We combined the experimental results with ab initio DFT calculations to obtain the average scattering lifetime of the charge carriers. • We found that the increase in the carrier density and an unexpected increase in the density of charged scattering centers compete in determining the scattering lifetime. - Abstract: We fabricate electric double-layer field-effect transistor (EDL-FET) devices on mechanically exfoliated few-layer graphene. We exploit the large capacitance of a polymeric electrolyte to study the transport properties of three, four and five-layer samples under a large induced surface charge density both above and below the glass transition temperature of the polymer. We find that the carrier mobility shows a strong asymmetry between the hole and electron doping regime. We then employ ab initio density functional theory (DFT) calculations to determine the average scattering lifetime from the experimental data. We explain its peculiar dependence on the carrier density in terms of the specific properties of the electrolyte we used in our experiments.

Intrinsic Charge Carrier Mobility in Single-Layer Black Phosphorus.

Science.gov (United States)

Rudenko, A N; Brener, S; Katsnelson, M I

2016-06-17

We present a theory for single- and two-phonon charge carrier scattering in anisotropic two-dimensional semiconductors applied to single-layer black phosphorus (BP). We show that in contrast to graphene, where two-phonon processes due to the scattering by flexural phonons dominate at any practically relevant temperatures and are independent of the carrier concentration n, two-phonon scattering in BP is less important and can be considered negligible at n≳10^{13}  cm^{-2}. At smaller n, however, phonons enter in the essentially anharmonic regime. Compared to the hole mobility, which does not exhibit strong anisotropy between the principal directions of BP (μ_{xx}/μ_{yy}∼1.4 at n=10^{13} cm^{-2} and T=300  K), the electron mobility is found to be significantly more anisotropic (μ_{xx}/μ_{yy}∼6.2). Absolute values of μ_{xx} do not exceed 250 (700)  cm^{2} V^{-1} s^{-1} for holes (electrons), which can be considered as an upper limit for the mobility in BP at room temperature.

Organic-inorganic hybrid perovskite quantum dots with high PLQY and enhanced carrier mobility through crystallinity control by solvent engineering and solid-state ligand exchange.

Science.gov (United States)

Woo Choi, Jin; Woo, Hee Chul; Huang, Xiaoguang; Jung, Wan-Gil; Kim, Bong-Joong; Jeon, Sie-Wook; Yim, Sang-Youp; Lee, Jae-Suk; Lee, Chang-Lyoul

2018-05-22

The photoluminescence quantum yield (PLQY) and charge carrier mobility of organic-inorganic perovskite QDs were enhanced by the optimization of crystallinity and surface passivation as well as solid-state ligand exchange. The crystallinity of perovskite QDs was determined by the Effective solvent field (Esol) of various solvents for precipitation. The solvent with high Esol could more quickly countervail the localized field generated by the polar solvent, and it causes fast crystallization of the dissolved precursor, which results in poor crystallinity. The post-ligand adding process (PLAP) and post-ligand exchange process (PLEP) increase the PLQY of perovskite QDs by reducing non-radiative recombination and the density of surface defect states through surface passivation. Particularly, the post ligand exchange process (PLEP) in the solid-state improved the charge carrier mobility of perovskite QDs in addition to the PLQY enhancement. The ligand exchange with short alkyl chain length ligands could improve the packing density of perovskite QDs in films by reducing the inter-particle distance between perovskite QDs. The maximum hole mobility of 6.2 × 10-3 cm2 V-1 s-1, one order higher than that of pristine QDs without the PLEP, is obtained at perovskite QDs with hexyl ligands. By using PLEP treatment, compared to the pristine device, a 2.5 times higher current efficiency in perovskite QD-LEDs was achieved due to the improved charge carrier mobility and PLQY.

A possible high-mobility signal in bulk MoTe2: Temperature independent weak phonon decay

Directory of Open Access Journals (Sweden)

Titao Li

2016-11-01

Full Text Available Layered transition metal dichalcogenides (TMDs have attracted great attention due to their non-zero bandgap for potential application in high carrier mobility devices. Recent studies demonstrate that the carrier mobility of MoTe2 would decrease by orders of magnitude when used for few-layer transistors. As phonon scattering has a significant influence on carrier mobility of layered material, here, we first reported temperature-dependent Raman spectra of bulk 2H-MoTe2 from 80 to 300 K and discovered that the phonon lifetime of both E12g and A1g vibration modes are independent with temperature. These results were explained by the weak phonon decay in MoTe2. Our results imply the existence of a carrier mobility higher than the theoretical value in intrinsic bulk 2H-MoTe2 and the feasibility to obtain MoTe2-based transistors with sufficiently high carrier mobility.

Low-field mobility and carrier transport mechanism transition in nanoscale MOSFETs

International Nuclear Information System (INIS)

Liu Hongwei; Wang Runsheng; Huang Ru; Zhang Xing

2010-01-01

This paper extends the flux scattering method to study the carrier transport property in nanoscale MOSFETs with special emphasis on the low-field mobility and the transport mechanism transition. A unified analytical expression for the low-field mobility is proposed, which covers the entire regime from drift-diffusion transport to quasi-ballistic transport in 1-D, 2-D and 3-D MOSFETs. Two key parameters, namely the long-channel low-field mobility (μ 0 ) and the low-field mean free path (λ 0 ), are obtained from the experimental data, and the transport mechanism transition in MOSFETs is further discussed both experimentally and theoretically. Our work shows that λ 0 is available to characterize the inherent transition of the carrier transport mechanism rather than the low-field mobility. The mobility reduces in the MOSFET with the shrinking of the channel length; however, λ 0 is nearly a constant, and λ 0 can be used as the 'entry criterion' to determine whether the device begins to operate under quasi-ballistic transport to some extent. (semiconductor devices)

Interplay between hopping and band transport in high-mobility disordered semiconductors at large carrier concentrations: The case of the amorphous oxide InGaZnO

Science.gov (United States)

Fishchuk, I. I.; Kadashchuk, A.; Bhoolokam, A.; de Jamblinne de Meux, A.; Pourtois, G.; Gavrilyuk, M. M.; Köhler, A.; Bässler, H.; Heremans, P.; Genoe, J.

2016-05-01

We suggest an analytic theory based on the effective medium approximation (EMA) which is able to describe charge-carrier transport in a disordered semiconductor with a significant degree of degeneration realized at high carrier concentrations, especially relevant in some thin-film transistors (TFTs), when the Fermi level is very close to the conduction-band edge. The EMA model is based on special averaging of the Fermi-Dirac carrier distributions using a suitably normalized cumulative density-of-state distribution that includes both delocalized states and the localized states. The principal advantage of the present model is its ability to describe universally effective drift and Hall mobility in heterogeneous materials as a function of disorder, temperature, and carrier concentration within the same theoretical formalism. It also bridges a gap between hopping and bandlike transport in an energetically heterogeneous system. The key assumption of the model is that the charge carriers move through delocalized states and that, in addition to the tail of the localized states, the disorder can give rise to spatial energy variation of the transport-band edge being described by a Gaussian distribution. It can explain a puzzling observation of activated and carrier-concentration-dependent Hall mobility in a disordered system featuring an ideal Hall effect. The present model has been successfully applied to describe experimental results on the charge transport measured in an amorphous oxide semiconductor, In-Ga-Zn-O (a-IGZO). In particular, the model reproduces well both the conventional Meyer-Neldel (MN) compensation behavior for the charge-carrier mobility and inverse-MN effect for the conductivity observed in the same a-IGZO TFT. The model was further supported by ab initio calculations revealing that the amorphization of IGZO gives rise to variation of the conduction-band edge rather than to the creation of localized states. The obtained changes agree with the one we

Toward High Carrier Mobility and Low Contact Resistance:Laser Cleaning of PMMA Residues on Graphene Surfaces

Institute of Scientific and Technical Information of China (English)

Yuehui Jia; Xin Gong; Pei Peng; Zidong Wang; Zhongzheng Tian; Liming Ren; Yunyi Fu; Han Zhang

2016-01-01

Poly(methyl methacrylate)(PMMA) is widely used for graphene transfer and device fabrication.However,it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of device performance.How to eliminate contamination and restore clean surfaces of graphene is still highly demanded.In this paper,we present a reliable and position-controllable method to remove the polymer residues on graphene films by laser exposure.Under proper laser conditions,PMMA residues can be substantially reduced without introducing defects to the underlying graphene.Furthermore,by applying this laser cleaning technique to the channel and contacts of graphene fieldeffect transistors(GFETs),higher carrier mobility as well as lower contact resistance can be realized.This work opens a way for probing intrinsic properties of contaminant-free graphene and fabricating high-performance GFETs with both clean channel and intimate graphene/metal contact.

Towards predictive many-body calculations of phonon-limited carrier mobilities in semiconductors

Science.gov (United States)

Poncé, Samuel; Margine, Elena R.; Giustino, Feliciano

2018-03-01

We probe the accuracy limit of ab initio calculations of carrier mobilities in semiconductors, within the framework of the Boltzmann transport equation. By focusing on the paradigmatic case of silicon, we show that fully predictive calculations of electron and hole mobilities require many-body quasiparticle corrections to band structures and electron-phonon matrix elements, the inclusion of spin-orbit coupling, and an extremely fine sampling of inelastic scattering processes in momentum space. By considering all these factors we obtain excellent agreement with experiment, and we identify the band effective masses as the most critical parameters to achieve predictive accuracy. Our findings set a blueprint for future calculations of carrier mobilities, and pave the way to engineering transport properties in semiconductors by design.

High Thermoelectric Power Factor of High-Mobility 2D Electron Gas.

Science.gov (United States)

Ohta, Hiromichi; Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi; Hashizume, Tamotsu

2018-01-01

Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower ( S ), high electrical conductivity (σ), and low thermal conductivity (κ). State-of-the-art nanostructuring techniques that significantly reduce κ have realized high-performance thermoelectric materials with a figure of merit ( ZT = S 2 ∙σ∙ T ∙κ -1 ) between 1.5 and 2. Although the power factor (PF = S 2 ∙σ) must also be enhanced to further improve ZT , the maximum PF remains near 1.5-4 mW m -1 K -2 due to the well-known trade-off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS-HEMT simultaneously modulates S and σ of the high-mobility electron gas from -490 µV K -1 and ≈10 -1 S cm -1 to -90 µV K -1 and ≈10 4 S cm -1 , while maintaining a high carrier mobility (≈1500 cm 2 V -1 s -1 ). The maximized PF of the high-mobility electron gas is ≈9 mW m -1 K -2 , which is a two- to sixfold increase compared to state-of-the-art practical thermoelectric materials.

Simultaneous enhancement of carrier mobility and concentration via tailoring of Al-chemical states in Al-ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Kumar, Manish, E-mail: manishk@skku.edu; Wen, Long; Sahu, Bibhuti B. [Center for Advance Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma-Nano Materials (IPNM), School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon-440746 (Korea, Republic of); Han, Jeon Geon [Center for Advance Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma-Nano Materials (IPNM), School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon-440746 (Korea, Republic of); Department of Industrial Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai-50200 (Thailand)

2015-06-15

Simultaneously achieving higher carriers concentration and mobility is a technical challenge against up-scaling the transparent-conductive performances of transparent-conductive oxides. Utilizing one order higher dense (∼1 × 10{sup 11} cm{sup −3}) plasmas (in comparison to the conventional direct current plasmas), highly c-axis oriented Al-doped ZnO films have been prepared with precise control over relative composition and chemical states of constituting elements. Tailoring of intrinsic (O vacancies) and extrinsic (ionic Al and zero-valent Al) dopants provide simultaneous enhancement in mobility and concentration of charge carriers. Room-temperature resistivity as low as 4.89 × 10{sup −4} Ω cm along the carrier concentration 5.6 × 10{sup 20} cm{sup −3} is obtained in 200 nm thick transparent films. Here, the control of atomic Al reduces the charge trapping at grain boundaries and subdues the effects of grain boundary scattering. A mechanism based on the correlation between electron-hole interaction and carrier mobility is proposed for degenerately doped wide band-gap semiconductors.

Low-voltage and high-efficiency white organic light emitting devices with carrier balance

International Nuclear Information System (INIS)

Wei Fuxiang; Huang, Y.; Fang, L.

2010-01-01

White organic light emitting devices with the structure of ITO/m-MTDATA:x%4F-TCNQ/NPB/TBADN:EBDP:DCJTB/Bphen:Liq/LiF/Al have been demonstrated in this paper. High-mobility m-MTDATA:4F-TCNQ is added into the region between ITO and NBP to increase hole injection and transport. The high-mobility Bphen:Liq layer is added into the region between cathode and emission layers to lower cathode barrier and facilitate carrier injection. In the meanwhile, an effective carrier balance (number of holes is equal to number of electrons) between holes and electrons is considered to be one of the most important factors for improving OLEDs. During the experiment, by modulating the doping concentration of 4F-TCNQ, we can control hole injection and transport to make the carriers reach a high-level balance. The maximum current efficiency and power efficiency of devices were 9.3 cd/A and 4.6 lm/A, respectively.

Scattering and mobility in indium gallium arsenide channel, pseudomorphic high electron mobility transistors (InGaAs pHEMTs)

International Nuclear Information System (INIS)

Pearson, J.L.

1999-03-01

Extensive transport measurements have been completed on deep and shallow-channelled InGaAs p-HEMTs of varying growth temperature, indium content, spacer thickness and doping density, with a view to a thorough characterisation, both in the metallic and the localised regimes. Particular emphasis was given to MBE grown layers, with characteristics applicable for device use, but low measurement temperatures were necessary to resolve the elastic scattering mechanisms. Measurements made in the metallic regime included transport and quantum mobility - the former over a range of temperatures between 1.5K to 300K. Conductivity measurements were also acquired in the strong localisation regime between about 1.5K and 100K. Experimentally determined parameters were tested for comparison with those predicted by an electrostatic model. Excellent agreement was obtained for carrier density. Other parameters were less well predicted, but the relevant experimental measurements, including linear depletion of the 2DEG, were sensitive to any excess doping above a 'critical' value determined by the model. At low temperature (1.5K), it was found that in all samples tested, transport mobility was strongly limited at all carrier densities by a large q mechanism, possibly intrinsic to the channel. This was ascribed either to scattering by the long-range potentials arising from the indium concentration fluctuations or fluctuations in the thickness of the channel layer. This mechanism dominates the transport at low carrier densities for all samples, but at high carrier density, an additional mechanism is significant for samples with the thinnest spacers tested (2.5nm). This is ascribed to direct electron interaction with the states of the donor layer, and produces a characteristic transport mobility peak. At higher carrier densities, past the peak, quantum mobility was found only to increase monotonically in value. Remote ionised impurity scattering while significant, particularly for samples

300% Enhancement of Carrier Mobility in Uniaxial-Oriented Perovskite Films Formed by Topotactic-Oriented Attachment.

Science.gov (United States)

Kim, Dong Hoe; Park, Jaehong; Li, Zhen; Yang, Mengjin; Park, Ji-Sang; Park, Ik Jae; Kim, Jin Young; Berry, Joseph J; Rumbles, Garry; Zhu, Kai

2017-06-01

Organic-inorganic perovskites with intriguing optical and electrical properties have attracted significant research interests due to their excellent performance in optoelectronic devices. Recent efforts on preparing uniform and large-grain polycrystalline perovskite films have led to enhanced carrier lifetime up to several microseconds. However, the mobility and trap densities of polycrystalline perovskite films are still significantly behind their single-crystal counterparts. Here, a facile topotactic-oriented attachment (TOA) process to grow highly oriented perovskite films, featuring strong uniaxial-crystallographic texture, micrometer-grain morphology, high crystallinity, low trap density (≈4 × 10 14 cm -3 ), and unprecedented 9 GHz charge-carrier mobility (71 cm 2 V -1 s -1 ), is demonstrated. TOA-perovskite-based n-i-p planar solar cells show minimal discrepancies between stabilized efficiency (19.0%) and reverse-scan efficiency (19.7%). The TOA process is also applicable for growing other state-of-the-art perovskite alloys, including triple-cation and mixed-halide perovskites. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transparent, high mobility InGaZnO thin films deposited by PLD

International Nuclear Information System (INIS)

Suresh, Arun; Gollakota, Praveen; Wellenius, Patrick; Dhawan, Anuj; Muth, John F.

2008-01-01

Transparent oxide semiconductor, InGaZnO, thin films were prepared by pulsed laser deposition at room temperature. The carrier concentration was found to vary by several orders of magnitude from insulating to 10 19 carriers/cm 3 depending on the oxygen partial pressure during deposition. Hall mobilities as high as 16 cm 2 /V s were observed. This is approximately an order of magnitude higher than the mobility of amorphous silicon and indicates that InGaO 3 (ZnO) x with x ≤ 5 may be suitable for transparent, thin film transistor applications. Post-deposition annealing was found to strongly influence the carrier concentration while annealing effects on the electron mobility was less influential

77 FR 14012 - Eligible Telecommunications Carrier Designation for Participation in Mobility Fund Phase I

Science.gov (United States)

2012-03-08

...; DA 12-271] Eligible Telecommunications Carrier Designation for Participation in Mobility Fund Phase I... Wireless Telecommunications and Wireline Competition Bureaus describe the process and requirements for applicants seeking Eligible Telecommunications Carrier (ETC) Designation from the Commission for...

Origin of high carrier mobility and low residual stress in RF superimposed DC sputtered Al doped ZnO thin film for next generation flexible devices

Science.gov (United States)

Kumar, Naveen; Dubey, Ashish; Bahrami, Behzad; Venkatesan, S.; Qiao, Qiquan; Kumar, Mukesh

2018-04-01

In this work, the energy and flux of high energetic ions were controlled by RF superimposed DC sputtering process to increase the grain size and suppress grain boundary potential with minimum residual stress in Al doped ZnO (AZO) thin film. AZO thin films were deposited at different RF/(RF + DC) ratios by keeping total power same and were investigated for their electrical, optical, structural and nanoscale grain boundaries potential. All AZO thin film showed high crystallinity and orientation along (002) with peak shift as RF/(RF + DC) ratio increased from 0.0, pure DC, to 1.0, pure RF. This peak shift was correlated with high residual stress in as-grown thin film. AZO thin film grown at mixed RF/(RF + DC) of 0.75 showed high electron mobility, low residual stress and large crystallite size in comparison to other AZO thin films. The nanoscale grain boundary potential was mapped using Kelvin Probe Force Microscopy in all AZO thin film and it was observed that carrier mobility is controlled not only by grains size but also by grain boundary potential. The XPS analysis confirms the variation in oxygen vacancies and zinc interstitials which explain the origin of low grain boundaries potential and high carrier mobility in AZO thin film deposited at 0.75 RF/(RF + DC) ratio. This study proposes a new way to control the grain size and grain boundary potential to further tune the optoelectronic-mechanical properties of AZO thin films for next generation flexible and optoelectronic devices.

Drift mobility of thermalized and highly energetic holes in thin layers of amorphous dielectric SiC

International Nuclear Information System (INIS)

Sielski, Jan; Jeszka, Jeremiasz K.

2012-01-01

The development of new technology in the electronics industry requires new dielectric materials. It is also important to understand the charge-carrier transport mechanism in these materials. We examined the hole drift mobility in amorphous SiC dielectric thin films using the time-of-flight (TOF) method. Charge carriers were generated using an electron gun. The generated holes gave a dispersive TOF signal and the mobility was low. For electric field strengths above 4 x 10 5 V cm -1 the drift mobility shows a very strong dependence on the electric field and a weak temperature dependence (transport of ''high-energy'' charge carriers). At lower electric fields and for thermalized charge carriers the mobility is practically field independent and thermally activated. The observed phenomenon was attributed to the changes in the effective energy of the generated carriers moving in the high electric fields and consequently in the density of localized states taking part in the transport. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Diverse carrier mobility of monolayer BNCx: A combined density functional theory and Boltzmann transport theory study.

Science.gov (United States)

Wu, Tao; Deng, Kaiming; Deng, Wei-Qiao; Lu, Ruifeng

2017-09-19

BNCX monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNCX (x=1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC2-1 is a material with very small band gap (0.02 eV) among all the structures while other BNCX monolayers are semiconductors with band gap ranging from 0.51 to 1.32 eV. The carrier mobility of BNCX varies considerably from tens to millions of cm2 V-1 s-1. For BNC2-1, the hole mobility and electron mobility along both x and y directions can reach 105 orders of magnitude, which is similar to the carrier mobility of graphene. Besides, all studied BNCX monolayers obviously have anisotropic hole mobility and electron mobility. In particular, for semiconductor BNC4, its hole mobility along y direction and electron mobility along x direction unexpectedly reach 106 orders of magnitude, even higher than that of graphene. Our findings suggest that BNCX layered materials with proper ratio and arrangement of carbon atoms will possess desirable charge transport properties, exhibiting potential applications in nanoelectronic devices. © 2017 IOP Publishing Ltd.

Tuning the Electronic Properties, Effective Mass and Carrier Mobility of MoS2 Monolayer by Strain Engineering: First-Principle Calculations

Science.gov (United States)

Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Hieu, Nguyen V.; Thu, Tran V.; Hung, Nguyen M.; Ilyasov, Victor V.; Poklonski, Nikolai A.; Nguyen, Chuong V.

2018-01-01

In this paper, we studied the electronic properties, effective masses, and carrier mobility of monolayer MoS_2 using density functional theory calculations. The carrier mobility was considered by means of ab initio calculations using the Boltzmann transport equation coupled with deformation potential theory. The effects of mechanical biaxial strain on the electronic properties, effective mass, and carrier mobility of monolayer MoS_2 were also investigated. It is demonstrated that the electronic properties, such as band structure and density of state, of monolayer MoS_2 are very sensitive to biaxial strain, leading to a direct-indirect transition in semiconductor monolayer MoS_2. Moreover, we found that the carrier mobility and effective mass can be enhanced significantly by biaxial strain and by lowering temperature. The electron mobility increases over 12 times with a biaxial strain of 10%, while the carrier mobility gradually decreases with increasing temperature. These results are very useful for the future nanotechnology, and they make monolayer MoS_2 a promising candidate for application in nanoelectronic and optoelectronic devices.

Studies of the mobility of charge carriers in low-dimensional systems in a transverse DC electric field

Energy Technology Data Exchange (ETDEWEB)

Sinyavskii, E. P., E-mail: sinyavskii@gmail.com [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of); Karapetyan, S. A., E-mail: karapetyan.sa@gmail.com [Shevchenko Pridnestrovskii State University (Moldova, Republic of)

2011-08-15

The mobility of charge carriers {mu} in a parabolic quantum well in an electric field E directed along the size-confinement axis is calculated. With consideration for scattering of charge carriers at a rough surface, the mobility {mu} is shown to decrease with increasing E. A physical interpretation of this effect is proposed.

High electron mobility and large magnetoresistance in the half-Heusler semimetal LuPtBi

KAUST Repository

Hou, Zhipeng

2015-12-18

Materials with high carrier mobility showing large magnetoresistance (MR) have recently received much attention because of potential applications in future high-performance magnetoelectric devices. Here, we report on an electron-hole-compensated half-Heusler semimetal LuPtBi that exhibits an extremely high electron mobility of up to 79000cm2/Vs with a nonsaturating positive MR as large as 3200% at 2 K. Remarkably, the mobility at 300 K is found to exceed 10500cm2/Vs, which is among the highest values reported in three-dimensional bulk materials thus far. The clean Shubnikov–de Haas quantum oscillation observed at low temperatures and the first-principles calculations together indicate that the high electron mobility is due to a rather small effective carrier mass caused by the distinctive band structure of the crystal. Our findings provide a different approach for finding large, high-mobility MR materials by designing an appropriate Fermi surface topology starting from simple electron-hole-compensated semimetals.

High-resolution charge carrier mobility mapping of heterogeneous organic semiconductors

Science.gov (United States)

Button, Steven W.; Mativetsky, Jeffrey M.

2017-08-01

Organic electronic device performance is contingent on charge transport across a heterogeneous landscape of structural features. Methods are therefore needed to unravel the effects of local structure on overall electrical performance. Using conductive atomic force microscopy, we construct high-resolution out-of-plane hole mobility maps from arrays of 5000 to 16 000 current-voltage curves. To demonstrate the efficacy of this non-invasive approach for quantifying and mapping local differences in electrical performance due to structural heterogeneities, we investigate two thin film test systems, one bearing a heterogeneous crystal structure [solvent vapor annealed 5,11-Bis(triethylsilylethynyl)anthradithiophene (TES-ADT)—a small molecule organic semiconductor] and one bearing a heterogeneous chemical composition [p-DTS(FBTTh2)2:PC71BM—a high-performance organic photovoltaic active layer]. TES-ADT shows nearly an order of magnitude difference in hole mobility between semicrystalline and crystalline areas, along with a distinct boundary between the two regions, while p-DTS(FBTTh2)2:PC71BM exhibits subtle local variations in hole mobility and a nanoscale domain structure with features below 10 nm in size. We also demonstrate mapping of the built-in potential, which plays a significant role in organic light emitting diode and organic solar cell operation.

Thermoelectric transport properties of high mobility organic semiconductors

Science.gov (United States)

Venkateshvaran, Deepak; Broch, Katharina; Warwick, Chris N.; Sirringhaus, Henning

2016-09-01

Transport in organic semiconductors has traditionally been investigated using measurements of the temperature and gate voltage dependent mobility of charge carriers within the channel of organic field-effect transistors (OFETs). In such measurements, the behavior of charge carrier mobility with temperature and gate voltage, studied together with carrier activation energies, provide a metric to quantify the extent of disorder within these van der Waals bonded materials. In addition to the mobility and activation energy, another potent but often-overlooked transport coefficient useful in understanding disorder is the Seebeck coefficient (also known as thermoelectric power). Fundamentally, the Seebeck coefficient represents the entropy per charge carrier in the solid state, and thus proves powerful in distinguishing materials in which charge carriers move freely from those where a high degree of disorder causes the induced carriers to remain trapped. This paper briefly covers the recent highlights in the field of organic thermoelectrics, showing how significant strides have been made both from an applied standpoint as well as from a viewpoint of fundamental thermoelectric transport physics. It shall be illustrated how thermoelectric transport parameters in organic semiconductors can be tuned over a significant range, and how this tunability facilitates an enhanced performance for heat-to-electricity conversion as well as quantifies energetic disorder and the nature of the density of states (DOS). The work of the authors shall be spotlighted in this context, illustrating how Seebeck coefficient measurements in the polymer indacenodithiophene-co-benzothiadiazole (IDTBT) known for its ultra-low degree of torsion within the polymer backbone, has a trend consistent with low disorder. 1 Finally, using examples of the small molecules C8-BTBT and C10-DNTT, it shall be discussed how the Seebeck coefficient can aid the estimation of the density and distribution of trap states

Determination of charge carrier mobility in doped low density polyethylene using DC transients

DEFF Research Database (Denmark)

Khalil, M.Salah; Henk, Peter O; Henriksen, Mogens

1989-01-01

Charge carrier mobility was determined for plain and doped low-density polyethylene (LDPE) using DC transient currents. Barium titanate was used as a strongly polar dopant and titanium dioxide as a semiconductor dopant. The values of the mobility obtained were on the order of 10-10 cm2 v-1 s-1...

Graphene/Pentacene Barristor with Ion-Gel Gate Dielectric: Flexible Ambipolar Transistor with High Mobility and On/Off Ratio.

Science.gov (United States)

Oh, Gwangtaek; Kim, Jin-Soo; Jeon, Ji Hoon; Won, EunA; Son, Jong Wan; Lee, Duk Hyun; Kim, Cheol Kyeom; Jang, Jingon; Lee, Takhee; Park, Bae Ho

2015-07-28

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.

Multi-THz spectroscopy of mobile charge carriers in P3HT:PCBM on a sub-100 fs time scale

DEFF Research Database (Denmark)

Cooke, David G.; Krebs, Frederik C; Jepsen, Peter Uhd

2013-01-01

The dynamics of mobile charge carrier generation in polymer bulk heterojunction films is of vital importance to the development of more efficient organic photovoltaics. As with conventional semiconductors, the optical signatures of mobile carriers lie in the far-infrared (1-30 THz) although...

Time-dependent mobility and recombination of the photoinduced charge carriers in conjugated polymer/fullerene bulk heterojunction solar cells

Science.gov (United States)

Mozer, A. J.; Dennler, G.; Sariciftci, N. S.; Westerling, M.; Pivrikas, A.; Österbacka, R.; Juška, G.

2005-07-01

Time-dependent mobility and recombination in the blend of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)- C61 (PCBM) is studied simultaneously using the photoinduced charge carrier extraction by linearly increasing voltage technique. The charge carriers are photogenerated by a strongly absorbed, 3 ns laser flash, and extracted by the application of a reverse bias voltage pulse after an adjustable delay time (tdel) . It is found that the mobility of the extracted charge carriers decreases with increasing delay time, especially shortly after photoexcitation. The time-dependent mobility μ(t) is attributed to the energy relaxation of the charge carriers towards the tail states of the density of states distribution. A model based on a dispersive bimolecular recombination is formulated, which properly describes the concentration decay of the extracted charge carriers at all measured temperatures and concentrations. The calculated bimolecular recombination coefficient β(t) is also found to be time-dependent exhibiting a power law dependence as β(t)=β0t-(1-γ) with increasing slope (1-γ) with decreasing temperatures. The temperature dependence study reveals that both the mobility and recombination of the photogenerated charge carriers are thermally activated processes with activation energy in the range of 0.1 eV. Finally, the direct comparison of μ(t) and β(t) shows that the recombination of the long-lived charge carriers is controlled by diffusion.

Photoinduced reversible switching of charge carrier mobility in conjugated polymers

Czech Academy of Sciences Publication Activity Database

Weiter, M.; Navrátil, J.; Vala, M.; Toman, Petr

2009-01-01

Roč. 48, č. 1 (2009), 10401_1-10401_6 ISSN 1286-0042 R&D Projects: GA ČR GA203/06/0285; GA AV ČR KAN401770651 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymers * switch * charge carrier mobility Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.756, year: 2009

Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

International Nuclear Information System (INIS)

Wenlong Yao

2006-01-01

This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M 2 S + (0.1 Ga 2 S 3 + 0.9 GeS 2 ) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga 2 S 3 + 0.9 GeS 2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M 2 S + (0.1Ga 2 S 3 + 0.9 GeS 2 ) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na 2 S + B 2 S 3 (x (le) 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x-ray diffraction experiments. The results provide direct

Boost Up Carrier Mobility for Ferroelectric Organic Transistor Memory via Buffering Interfacial Polarization Fluctuation

Science.gov (United States)

Sun, Huabin; Wang, Qijing; Li, Yun; Lin, Yen-Fu; Wang, Yu; Yin, Yao; Xu, Yong; Liu, Chuan; Tsukagoshi, Kazuhito; Pan, Lijia; Wang, Xizhang; Hu, Zheng; Shi, Yi

2014-11-01

Ferroelectric organic field-effect transistors (Fe-OFETs) have been attractive for a variety of non-volatile memory device applications. One of the critical issues of Fe-OFETs is the improvement of carrier mobility in semiconducting channels. In this article, we propose a novel interfacial buffering method that inserts an ultrathin poly(methyl methacrylate) (PMMA) between ferroelectric polymer and organic semiconductor layers. A high field-effect mobility (μFET) up to 4.6 cm2 V-1 s-1 is obtained. Subsequently, the programming process in our Fe-OFETs is mainly dominated by the switching between two ferroelectric polarizations rather than by the mobility-determined charge accumulation at the channel. Thus, the ``reading'' and ``programming'' speeds are significantly improved. Investigations show that the polarization fluctuation at semiconductor/insulator interfaces, which affect the charge transport in conducting channels, can be suppressed effectively using our method.

Diverse carrier mobility of monolayer BNC x : a combined density functional theory and Boltzmann transport theory study.

Science.gov (United States)

Wu, Tao; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng

2017-10-19

BNC x monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNC x (x  =  1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC 2 -1 is a material with very small band gap (0.02 eV) among all the structures while other BNC x monolayers are semiconductors with band gap ranging from 0.51 eV to 1.32 eV. The carrier mobility of BNC x varies considerably from tens to millions of cm 2 V -1 s -1 . For BNC 2 -1, the hole mobility and electron mobility along both x and y directions can reach 10 5 orders of magnitude, which is similar to the carrier mobility of graphene. Besides, all studied BNC x monolayers obviously have anisotropic hole mobility and electron mobility. In particular, for semiconductor BNC 4 , its hole mobility along the y direction and electron mobility along the x direction unexpectedly reach 10 6 orders of magnitude, even higher than that of graphene. Our findings suggest that BNC x layered materials with the proper ratio and arrangement of carbon atoms will possess desirable charge transport properties, exhibiting potential applications in nanoelectronic devices.

Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films.

Science.gov (United States)

Röhr, Jason A; Moia, Davide; Haque, Saif A; Kirchartz, Thomas; Nelson, Jenny

2018-03-14

Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches a value of two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical of single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed.

Exploring the validity and limitations of the Mott-Gurney law for charge-carrier mobility determination of semiconducting thin-films

Science.gov (United States)

Röhr, Jason A.; Moia, Davide; Haque, Saif A.; Kirchartz, Thomas; Nelson, Jenny

2018-03-01

Using drift-diffusion simulations, we investigate the voltage dependence of the dark current in single carrier devices typically used to determine charge-carrier mobilities. For both low and high voltages, the current increases linearly with the applied voltage. Whereas the linear current at low voltages is mainly due to space charge in the middle of the device, the linear current at high voltage is caused by charge-carrier saturation due to a high degree of injection. As a consequence, the current density at these voltages does not follow the classical square law derived by Mott and Gurney, and we show that for trap-free devices, only for intermediate voltages, a space-charge-limited drift current can be observed with a slope that approaches a value of two. We show that, depending on the thickness of the semiconductor layer and the size of the injection barriers, the two linear current-voltage regimes can dominate the whole voltage range, and the intermediate Mott-Gurney regime can shrink or disappear. In this case, which will especially occur for thicknesses and injection barriers typical of single-carrier devices used to probe organic semiconductors, a meaningful analysis using the Mott-Gurney law will become unachievable, because a square-law fit can no longer be achieved, resulting in the mobility being substantially underestimated. General criteria for when to expect deviations from the Mott-Gurney law when used for analysis of intrinsic semiconductors are discussed.

Calculated carrier mobility of h-BN/γ-InSe/h-BN van der Waals heterostructures

Science.gov (United States)

Kang, P.; Michaud-Rioux, V.; Kong, X.-H.; Yu, G.-H.; Guo, H.

2017-12-01

Recent experiments reported excellent transport properties of two-dimensional (2D) van der Waals (vdW) heterostructures made of atomically thin InSe layers encapsulated by two hBN capping layers (ISBN). The carrier mobility of the ISBN films exceeded μ ˜ 1.2× {{10}4} \\text{c}{{\\text{m}}2} {{\\text{V}}-1} {{\\text{s}}-1} at low temperature, much higher than that of pristine InSe films. It has been puzzling why the relatively inert hBN capping layer could so drastically enhance mobility of the ISBN composite. Using a state-of-the-art first principles method, we have calculated phonon limited carrier mobility of 18 different ISBN films and 6 pristine InSe films with different thicknesses, the largest system containing 2212 atoms. The hBN capping layer significantly alters the elastic stiffness coefficient as compared with pure InSe—thus the acoustic phonons in the ISBN composite—giving rise to the observed large mobility of ISBN films. Of the 18 calculated ISBN films, the ones with no strain at the hBN/InSe interface possess the highest electron mobility, reaching 4340~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at room temperature, which could easily go over {{10}4}~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at low temperatures. We conclude that the mechanical properties of the composite 2D vdW ISBN material play the crucial role for inducing the large carrier mobility, a principle that could be applied to many other 2D vdW heterostructures.

Carbon doped GaAs/AlGaAs heterostructures with high mobility two dimensional hole gas

Energy Technology Data Exchange (ETDEWEB)

Hirmer, Marika; Bougeard, Dominique; Schuh, Dieter [Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, D 93040 Regensburg (Germany); Wegscheider, Werner [Laboratorium fuer Festkoerperphysik, ETH Zuerich, 8093 Zuerich (Switzerland)

2011-07-01

Two dimensional hole gases (2DHG) with high carrier mobilities are required for both fundamental research and possible future ultrafast spintronic devices. Here, two different types of GaAs/AlGaAs heterostructures hosting a 2DHG were investigated. The first structure is a GaAs QW embedded in AlGaAs barrier grown by molecular beam epitaxy with carbon-doping only at one side of the quantum well (QW) (single side doped, ssd), while the second structure is similar but with symmetrically arranged doping layers on both sides of the QW (double side doped, dsd). The ssd-structure shows hole mobilities up to 1.2*10{sup 6} cm{sup 2}/Vs which are achieved after illumination. In contrast, the dsd-structure hosts a 2DHG with mobility up to 2.05*10{sup 6} cm{sup 2}/Vs. Here, carrier mobility and carrier density is not affected by illuminating the sample. Both samples showed distinct Shubnikov-de-Haas oscillations and fractional quantum-Hall-plateaus in magnetotransport experiments done at 20mK, indicating the high quality of the material. In addition, the influence of different temperature profiles during growth and the influence of the Al content of the barrier Al{sub x}Ga{sub 1-x}As on carrier concentration and mobility were investigated and are presented here.

Carrier mobility and crystal perfection of tetracene thin film FET

International Nuclear Information System (INIS)

Moriguchi, N.; Nishikawa, T.; Anezaki, T.; Unno, A.; Tachibana, M.; Kojima, K.

2006-01-01

It is well-known that the carrier mobility of an organic field effect semiconductor (FET) depended on the crystal quality and/or the crystal perfection of the organic thin films [T.W. Kelly, D.V. Muyres, P.F. Baude, T.P. Smith, T.D. Jones, Mater. Res. Soc. Symp. Proc. 771 (2003) L6.5.1; D.J. Gundlach, J.A. Nichols, L. Zhou, T.N. Jackson, Appl. Phys. Lett. 80 (2002) 2925; H.K. Lauk, M. Halik, U. Zschieschang, G. Schmid, W. Radlik, J. Appl. Phys. 92 (2002) 5259; M. Shtein, J. Mapel, J.B. Benziger, S.R. Forrest, Appl. Phys. Lett. 81 (2002) 268; D. Knipp, R.A. Street, A.R. Volkel, Appl. Phys. Lett. 82 (2003) 3907; R. Ruiz, A.C. Mayer, G.G. Malliaras, Appl. Phys. Lett. 85 (2004) 4926; R.W.I. de Boer, M.E. Gershenson, A.F. Morpurgo, V. Podzorov, Phys. Stat. Sol. A 201 (2004) 1031]. To improve the crystal quality of the thin film many efforts were made. One of the important improvements was the surface treatment of the substrate. The tetracene thin film FET (top contact structure) was fabricated using the substrate, which was coated by a spin-coating method with a 0.1% poly α-methylstyrene (AMS) solution. The crystal quality was improved by this treatment so that the carrier mobility was higher than that of non-treatment. The maximum mobility of the AMS-treated sample was obtained to be 0.12 cm 2 /V s

Stability and carrier mobility of organic-inorganic hybrid perovskite CH3NH3PbI3 in two-dimensional limit

Science.gov (United States)

Huang, Kui; Lai, Kang; Yan, Chang-Lin; Zhang, Wei-Bing

2017-10-01

Recently, atomically thin organic-inorganic hybrid perovskites have been synthesized experimentally, which opens up new opportunities for exploring their novel properties in the 2D limit. Based on the comparative density functional theory calculation with and without spin-orbit coupling effects, the stability, electronic structure, and carrier mobility of the two-dimensional organic-inorganic hybrid perovskites MAPbI3 (MA = CH3NH3) have been investigated systemically. Two single-unit-cell-thick 2D MAPbI3 terminated by PbI2 and CH3NH3I are constructed, and their thermodynamic stabilities are also evaluated using the first-principles constrained thermodynamics method. Our results indicate that both 2D MAPbI3 with different terminations can be stable under certain conditions and have a suitable direct bandgap. Moreover, they are also found to have termination-dependent band edge and carrier mobility. The acoustic-phonon-limited carrier mobilities estimated using the deformation theory and effective mass approximation are on the order of thousands of square centimeters per volt per second and also highly anisotropic. These results indicate that 2D MAPbI3 are competitive candidates for low-dimensional photovoltaic applications.

Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

Energy Technology Data Exchange (ETDEWEB)

Yao, Wenlong [Iowa State Univ., Ames, IA (United States)

2006-01-01

This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M₂S + (0.1 Ga₂S₃ + 0.9 GeS₂) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga₂S₃ + 0.9 GeS₂ was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M₂S + (0.1Ga₂S₃ + 0.9 GeS₂) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na₂S + B₂S₃ (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction

Observation of disorder effects on charged carrier mobility in triphenylene-based discotic materials

International Nuclear Information System (INIS)

Zhang Chunxiu; He, Zhiqun; Mao Huaxiang; Wang Junjie; Wang Dongdong; Wang Yongsheng; Li Zhongxiao; Pu Jialing

2007-01-01

A discotic 2,6,10-trihydroxy-3,7,11-tripentyloxytriphenylene material and a triphenylene-based hyperbranched macromolecule were synthesized, in which the latter was prepared from AB m molecules in a one-pot reaction. Adipic chloride and butyryl chloride were chosen as terminal groups to the 2,6,10-trihydroxy-3,7,11-tripentyloxytriphenylene. Mesophase and their structural orders were determined using a polarized optical microscope and a differential scanning calorimeter. Carrier mobilities of the pure and composite materials were measured via a time-of-flight method. A change in carrier mobility on the morphology of the materials was further discussed. It was found that degree of crystallization was the key for a discotic triphenylene material to possess charge-transporting properties, no matter it is ordered or disordered

Nonlinear transport in semiconducting polymers at high carrier densities.

Science.gov (United States)

Yuen, Jonathan D; Menon, Reghu; Coates, Nelson E; Namdas, Ebinazar B; Cho, Shinuk; Hannahs, Scott T; Moses, Daniel; Heeger, Alan J

2009-07-01

Conducting and semiconducting polymers are important materials in the development of printed, flexible, large-area electronics such as flat-panel displays and photovoltaic cells. There has been rapid progress in developing conjugated polymers with high transport mobility required for high-performance field-effect transistors (FETs), beginning with mobilities around 10(-4) cm(2) V(-1) s(-1) to a recent report of 1 cm(2) V(-1) s(-1) for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Here, the electrical properties of PBTTT are studied at high charge densities both as the semiconductor layer in FETs and in electrochemically doped films to determine the transport mechanism. We show that data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in the Luttinger liquid description of the one-dimensional 'metal'.

Density and mobility effects of the majority carriers in organic semiconductors under light excitation

Energy Technology Data Exchange (ETDEWEB)

Vagenas, N.; Giannopoulou, A.; Kounavis, P., E-mail: pkounavis@upatras.gr [Department of Electrical and Computer Engineering, University of Patras, 26504 Patra (Greece)

2015-01-21

This study demonstrates that the effect of light excitation on the density and the mobility of the majority carriers can be explored in organic semiconductors by modulated photocurrent spectroscopy. The spectra of phase and amplitude of the modulated photocurrent of pentacene films indicate a significant increase in the density of the photogenerated mobile holes (majority carriers). This increase is accompanied by a comparatively much smaller increase of the steady state photocurrent response which can be reconciled with a decrease in the mobility (μ) of holes. The decrease of μ is supported from an unusual increase of the Y/μ ratio of the out-of-phase modulated photocurrent (Y) signal to the mobility under light excitation. It is proposed that the mobile holes, which are generated from the dissociation of the light-created excitons more likely near the pentacene-substrate interface by electron trapping, populate grain boundaries charging them and producing a downward band bending. As a result, potential energy barriers are build up which limit the transport of holes interacting through trapping-detrapping with deep partially occupied traps in the charged grain boundaries. On the other hand, the transport of holes interacting through trapping-detrapping with empty traps is found unaffected.

Correlation Between Two-Dimensional Electron Gas Mobility and Crystal Quality in AlGaN/GaN High-Electron-Mobility Transistor Structure Grown on 4H-SiC.

Science.gov (United States)

Heo, Cheon; Jang, Jongjin; Lee, Kyngjae; So, Byungchan; Lee, Kyungbae; Ko, Kwangse; Nam, Okhyun

2017-01-01

We investigated the correlation between the crystal quality and two-dimensional electron gas (2DEG) mobility of an AlGaN/GaN high-electron-mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition. For the structure with an AlN nucleation layer grown at 1100 °C, the 2DEG mobility and sheet carrier density were 1627 cm²/V·s and 3.23 × 10¹³ cm⁻², respectively, at room temperature. Further, it was confirmed that the edge dislocation density of the GaN buffer layer was related to the 2DEG mobility and sheet carrier density in the AlGaN/GaN HEMT.

Temperature dependence of ballistic mobility in a metamorphic InGaAs/InAlAs high electron mobility transistor

International Nuclear Information System (INIS)

Lee, Jongkyong; Gang, Suhyun; Jo, Yongcheol; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Im, Hyunsik

2014-01-01

We have investigated the temperature dependence of ballistic mobility in a 100 nm-long InGaAs/InAlAs metamorphic high-electron-mobility transistor designed for millimeter-wavelength RF applications. To extract the temperature dependence of quasi-ballistic mobility, our experiment involves measurements of the effective mobility in the low-bias linear region of the transistor and of the collision-dominated Hall mobility using a gated Hall bar of the same epitaxial structure. The data measured from the experiment are consistent with that of modeled ballistic mobility based on ballistic transport theory. These results advance the understanding of ballistic transport in various transistors with a nano-scale channel length that is comparable to the carrier's mean free path in the channel.

High electron mobility and large magnetoresistance in the half-Heusler semimetal LuPtBi

KAUST Repository

Hou, Zhipeng; Wang, Wenhong; Xu, Guizhou; Zhang, Xiaoming; Wei, Zhiyang; Shen, Shipeng; Liu, Enke; Yao, Yuan; Chai, Yisheng; Sun, Young; Xi, Xuekui; Wang, Wenquan; Liu, Zhongyuan; Wu, Guangheng; Zhang, Xixiang

2015-01-01

Materials with high carrier mobility showing large magnetoresistance (MR) have recently received much attention because of potential applications in future high-performance magnetoelectric devices. Here, we report on an electron-hole

High-precision high-sensitivity clock recovery circuit for a mobile payment application

International Nuclear Information System (INIS)

Sun Lichong; Yan Na; Min Hao; Ren Wenliang

2011-01-01

This paper presents a fully integrated carrier clock recovery circuit for a mobile payment application. The architecture is based on a sampling-detection module and a charge pump phase locked loop. Compared with clock recovery in conventional 13.56 MHz transponders, this circuit can recover a high-precision consecutive carrier clock from the on/off keying (OOK) signal sent by interrogators. Fabricated by a SMIC 0.18-μm EEPROM CMOS process, this chip works from a single power supply as low as 1.5 V Measurement results show that this circuit provides 0.34% frequency deviation and 8 mV sensitivity. (semiconductor integrated circuits)

Side chain engineering of fused aromatic thienopyrazine based low band-gap polymers for enhanced charge carrier mobility

KAUST Repository

Mondal, Rajib

2011-01-01

A strategic side-chain engineering approach leads to the two orders of magnitude enhancement of charge carrier mobility in phenanthrene based fused aromatic thienopyrazine polymers. Hole carrier mobility up to 0.012 cm 2/Vs can be obtained in thin film transistor devices. Polymers were also utilized to fabricate bulk heterojunction photovoltaic devices and the maximum PCE obtained in these OPV\\'s was 1.15%. Most importantly, performances of the devices were correlated with thin morphological analysis performed by atomic force microscopy and grazing incidence X-ray scattering. © 2011 The Royal Society of Chemistry.

Organic High Electron Mobility Transistors Realized by 2D Electron Gas.

Science.gov (United States)

Zhang, Panlong; Wang, Haibo; Yan, Donghang

2017-09-01

A key breakthrough in inorganic modern electronics is the energy-band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field-effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high-mobility crystalline organic materials. Therefore, there emerges a chance for applying energy-band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy-band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm 2 V -1 s -1 , and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy-band engineering, offering a promising way for the step forward of organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

41 CFR 302-10.200 - What costs are allowable when a commercial carrier transports my mobile home overland or over water?

Science.gov (United States)

2010-07-01

... when a commercial carrier transports my mobile home overland or over water? 302-10.200 Section 302-10... carrier transports my mobile home overland or over water? Your agency will allow the following costs for... State or local law. (b) When transporting over water cost must include, but not limited to the cost of...

Modelling of the charge carrier mobility in disordered linear polymer materials

Czech Academy of Sciences Publication Activity Database

Toman, Petr; Menšík, Miroslav; Bartkowiak, W.; Pfleger, Jiří

2017-01-01

Roč. 19, č. 11 (2017), s. 7760-7771 ISSN 1463-9076 R&D Projects: GA ČR(CZ) GA15-05095S Grant - others:AV ČR(CZ) M200501204 Program:M Institutional support: RVO:61389013 Keywords : charge carrier mobility * conjugated polymer * charge transport modelling Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 4.123, year: 2016

Charge carrier mobility and electronic properties of Al(Op3: impact of excimer formation

Directory of Open Access Journals (Sweden)

Andrea Magri

2015-05-01

Full Text Available We have studied the electronic properties and the charge carrier mobility of the organic semiconductor tris(1-oxo-1H-phenalen-9-olatealuminium(III (Al(Op3 both experimentally and theoretically. We experimentally estimated the HOMO and LUMO energy levels to be −5.93 and −3.26 eV, respectively, which were close to the corresponding calculated values. Al(Op3 was successfully evaporated onto quartz substrates and was clearly identified in the absorption spectra of both the solution and the thin film. A structured steady state fluorescence emission was detected in solution, whereas a broad, red-shifted emission was observed in the thin film. This indicates the formation of excimers in the solid state, which is crucial for the transport properties. The incorporation of Al(Op3 into organic thin film transistors (TFTs was performed in order to measure the charge carrier mobility. The experimental setup detected no electron mobility, while a hole mobility between 0.6 × 10−6 and 2.1 × 10−6 cm2·V−1·s−1 was measured. Theoretical simulations, on the other hand, predicted an electron mobility of 9.5 × 10−6 cm2·V−1·s−1 and a hole mobility of 1.4 × 10−4 cm2·V−1·s−1. The theoretical simulation for the hole mobility predicted an approximately one order of magnitude higher hole mobility than was observed in the experiment, which is considered to be in good agreement. The result for the electron mobility was, on the other hand, unexpected, as both the calculated electron mobility and chemical common sense (based on the capability of extended aromatic structures to efficiently accept and delocalize additional electrons suggest more robust electron charge transport properties. This discrepancy is explained by the excimer formation, whose inclusion in the multiscale simulation workflow is expected to bring the theoretical simulation and experiment into agreement.

Field effect measurements on charge carrier mobilities in various polymer-fullerene blend compositions

International Nuclear Information System (INIS)

Hauff, Elizabeth von; Parisi, Juergen; Dyakonov, Vladimir

2006-01-01

In this study we investigated materials typically used in polymer photovoltaics. Field effect measurements were performed in order to determine the hole mobilities in the conjugated polymer poly(3-hexylthiophene) (P3HT) and the electron mobilities in the methanofullerene[6,6]-phenyl C 61 -butyric acid methyl ester (PCBM), and, particularly, in the polymer-fullerene composite blends. Regarding the pure films, electron mobilities in PCBM were found to be in the 10 -2 cm 2 /Vs range, and hole mobilities in P3HT were found to be in the 10 -3 cm2/Vs range. In the PCBM:P3HT blends, it was found that varying the PCBM content in PCBM:P3HT blends led to a steep increase in electron mobility with increasing PCBM content, while the hole mobility was found to slightly decrease with the increasing PCBM concentration. In 2:1 PCBM:P3HT tempered blends, the charge carrier mobilities were found to be roughly balanced, at 10 -3 cm 2 /Vs. For improved electron transport in the blends, tempering was found to be crucial

The design of a linear L-band high power amplifier for mobile communication satellites

Science.gov (United States)

Whittaker, N.; Brassard, G.; Li, E.; Goux, P.

1990-01-01

A linear L-band solid state high power amplifier designed for the space segment of the Mobile Satellite (MSAT) mobile communication system is described. The amplifier is capable of producing 35 watts of RF power with multitone signal at an efficiency of 25 percent and with intermodulation products better than 16 dB below carrier.

A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations

International Nuclear Information System (INIS)

Song, Linze; Shi, Qiang

2015-01-01

We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated

Designing thiophene-based azomethine oligomers with tailored properties: Self-assembly and charge carrier mobility

DEFF Research Database (Denmark)

Kiriy, N.; Bocharova, V.; Kiriy, A.

2004-01-01

This paper describes synthesis and characterization of two thiophene-based azomethines designed to optimize solubility, self-assembly, and charge carrier mobility. We found that incorporation of azomethine and amide moieties in the alpha,omega-position, and hexyl chains in the beta-position of th...... with the mobilities of the best organic semiconductors. All these significant differences in properties of related compounds can be attributed to the hydrogen bonding between QT-amide molecules responsible for the observed self-assembly....

Investigation of carrier density and mobility in microcrystalline silicon alloys using Hall effect and thermopower measurements; Untersuchung der Ladungstraegerkonzentration und -beweglichkeit in mikrokristallinen Siliziumlegierungen mit Hall-Effekt und Thermokraft

Energy Technology Data Exchange (ETDEWEB)

Sellmer, Christian

2012-08-31

The electronic properties of amorphous and microcrystalline silicon layers in thin-film solar cells significantly affect the efficiency of solar cells. An important property of the individual layer is the electronic transport, which is described by the variables conductivity, photoconductivity, mobility, and carrier concentration. In the past, individual characterization methods were typically used to determine the electronic properties. Using the combination of Hall effect, conductivity, and thermoelectric power measurements additional variables can be derived, such as the effective density of states at the valence and conduction band edge, making a more detailed description of the material possible. To systematically study the electronic properties - in particular carrier mobility and carrier concentration - various series of silicon films are prepared for this work including microcrystalline silicon layers of different doping and crystallinity and a series of silicon films where the Fermi level is moved by irradiation with high energy electrons on one and the same sample. The results show that the transition from amorphous to microcrystalline transport is relatively abrupt. If the electron transport takes place in only amorphous regions, it is marked by the sign anomaly of the Hall effect. If a continuous crystalline path exists, the electronic properties are dominated by the crystalline volume fraction. The results of the measurements of silicon layers are compared with those of microcrystalline silicon carbide samples. Silicon carbide is especially interesting for future applications in thin-film solar cells due to high transparency and high conductivity. It is shown that the effective density of states at the valence and conduction band edge as a function of temperature in p- and n-type microcrystalline silicon and silicon carbide samples largely coincide with those of crystalline silicon or silicon carbide. A square root shaped profile of the density of

Thickness and growth-condition dependence of in-situ mobility and carrier density of epitaxial thin-film Bi2Se3

International Nuclear Information System (INIS)

Hellerstedt, Jack; Fuhrer, Michael S.; Edmonds, Mark T.; Zheng, C. X.; Chen, J. H.; Cullen, William G.

2014-01-01

Bismuth selenide Bi 2 Se 3 was grown by molecular beam epitaxy, while carrier density and mobility were measured directly in situ as a function of film thickness. Carrier density shows high interface n-doping (1.5 × 10 13  cm −2 ) at the onset of film conduction and bulk dopant density of ∼5 × 10 11  cm −2 per quintuple-layer unit, roughly independent of growth temperature profile. Mobility depends more strongly on the growth temperature and is related to the crystalline quality of the samples quantified by ex-situ atomic force microscopy measurements. These results indicate that Bi 2 Se 3 as prepared by widely employed parameters is n-doped before exposure to atmosphere, the doping is largely interfacial in origin, and dopants are not the limiting disorder in present Bi 2 Se 3 films.

Carrier mobility in mesoscale heterogeneous organic materials: Effects of crystallinity and anisotropy on efficient charge transport

Science.gov (United States)

Kobayashi, Hajime; Shirasawa, Raku; Nakamoto, Mitsunori; Hattori, Shinnosuke; Tomiya, Shigetaka

2017-07-01

Charge transport in the mesoscale bulk heterojunctions (BHJs) of organic photovoltaic devices (OPVs) is studied using multiscale simulations in combination with molecular dynamics, the density functional theory, the molecular-level kinetic Monte Carlo (kMC) method, and the coarse-grained kMC method, which was developed to estimate mesoscale carrier mobility. The effects of the degree of crystallinity and the anisotropy of the conductivity of donors on hole mobility are studied for BHJ structures that consist of crystalline and amorphous pentacene grains that act as donors and amorphous C60 grains that act as acceptors. We find that the hole mobility varies dramatically with the degree of crystallinity of pentacene because it is largely restricted by a low-mobility amorphous region that occurs in the hole transport network. It was also found that the percolation threshold of crystalline pentacene is relatively high at approximately 0.6. This high percolation threshold is attributed to the 2D-like conductivity of crystalline pentacene, and the threshold is greatly improved to a value of approximately 0.3 using 3D-like conductive donors. We propose essential guidelines to show that it is critical to increase the degree of crystallinity and develop 3D conductive donors for efficient hole transport through percolative networks in the BHJs of OPVs.

Charge mobility modification of semiconducting carbon nanotubes by intrinsic defects

International Nuclear Information System (INIS)

Bai, Hongcun; Ma, Yujia; Ma, Jinsuo; Mei, Jingnan; Tong, Yan; Ji, Yongqiang

2017-01-01

Charge carrier mobility is a central transport property in nanoscale electronics. Carbon nanotubes (CNTs) are supposed to have high carrier mobility. The preparation methods of CNTs have been greatly improved, but the defects always exist. This work presented first-principle investigations on the charge carrier mobility of carbon nanotubes containing several intrinsic defects. The charge carrier mobilities of zigzag (10, 0) tubes with Stone–Wales, mono vacant and 5/8/5 defects were studied as an example to explore the role of defects. Most carrier mobilities were decreased, but several values of mobility are unexpectedly increased upon the appearance of the defects. This interesting result is discussed based on the changes of the stretching modulus, the effective mass of the carrier and deformation potential constant induced by the defects. (paper)

High mobility and quantum well transistors design and TCAD simulation

CERN Document Server

Hellings, Geert

2013-01-01

For many decades, the semiconductor industry has miniaturized transistors, delivering increased computing power to consumers at decreased cost. However, mere transistor downsizing does no longer provide the same improvements. One interesting option to further improve transistor characteristics is to use high mobility materials such as germanium and III-V materials. However, transistors have to be redesigned in order to fully benefit from these alternative materials. High Mobility and Quantum Well Transistors: Design and TCAD Simulation investigates planar bulk Germanium pFET technology in chapters 2-4, focusing on both the fabrication of such a technology and on the process and electrical TCAD simulation. Furthermore, this book shows that Quantum Well based transistors can leverage the benefits of these alternative materials, since they confine the charge carriers to the high-mobility material using a heterostructure. The design and fabrication of one particular transistor structure - the SiGe Implant-Free Qu...

Mobility of delocalized charge carriers in an ideal homopolar glass as a function of temperature

International Nuclear Information System (INIS)

Iskra, V.D.

1986-01-01

The relationship between temperature and the mobility of delocalized charge carriers for an intrinsic random field of a homopolar glass is investigated through application of a method of scattering amplitude calculation based on employing short-lived potential factorization

On the role of local charge carrier mobility in the charge separation mechanism of organic photovoltaics.

Science.gov (United States)

Yoshikawa, Saya; Saeki, Akinori; Saito, Masahiko; Osaka, Itaru; Seki, Shu

2015-07-21

Although the charge separation (CS) and transport processes that compete with geminate and non-geminate recombination are commonly regarded as the governing factors of organic photovoltaic (OPV) efficiency, the details of the CS mechanism remain largely unexplored. Here we provide a systematic investigation on the role of local charge carrier mobility in bulk heterojunction films of ten different low-bandgap polymers and polythiophene analogues blended with methanofullerene (PCBM). By correlating with the OPV performances, we demonstrated that the local mobility of the blend measured by time-resolved microwave conductivity is more important for the OPV output than those of the pure polymers. Furthermore, the results revealed two separate trends for crystalline and semi-crystalline polymers. This work offers guidance in the design of high-performance organic solar cells.

Accurate Extraction of Charge Carrier Mobility in 4-Probe Field-Effect Transistors

KAUST Repository

Choi, Hyun Ho; Rodionov, Yaroslav I.; Paterson, Alexandra F.; Panidi, Julianna; Saranin, Danila; Kharlamov, Nikolai; Didenko, Sergei I.; Anthopoulos, Thomas D.; Cho, Kilwon; Podzorov, Vitaly

2018-01-01

Charge carrier mobility is an important characteristic of organic field-effect transistors (OFETs) and other semiconductor devices. However, accurate mobility determination in FETs is frequently compromised by issues related to Schottky-barrier contact resistance, that can be efficiently addressed by measurements in 4-probe/Hall-bar contact geometry. Here, it is shown that this technique, widely used in materials science, can still lead to significant mobility overestimation due to longitudinal channel shunting caused by voltage probes in 4-probe structures. This effect is investigated numerically and experimentally in specially designed multiterminal OFETs based on optimized novel organic-semiconductor blends and bulk single crystals. Numerical simulations reveal that 4-probe FETs with long but narrow channels and wide voltage probes are especially prone to channel shunting, that can lead to mobilities overestimated by as much as 350%. In addition, the first Hall effect measurements in blended OFETs are reported and how Hall mobility can be affected by channel shunting is shown. As a solution to this problem, a numerical correction factor is introduced that can be used to obtain much more accurate experimental mobilities. This methodology is relevant to characterization of a variety of materials, including organic semiconductors, inorganic oxides, monolayer materials, as well as carbon nanotube and semiconductor nanocrystal arrays.

Accurate Extraction of Charge Carrier Mobility in 4-Probe Field-Effect Transistors

KAUST Repository

Choi, Hyun Ho

2018-04-30

Charge carrier mobility is an important characteristic of organic field-effect transistors (OFETs) and other semiconductor devices. However, accurate mobility determination in FETs is frequently compromised by issues related to Schottky-barrier contact resistance, that can be efficiently addressed by measurements in 4-probe/Hall-bar contact geometry. Here, it is shown that this technique, widely used in materials science, can still lead to significant mobility overestimation due to longitudinal channel shunting caused by voltage probes in 4-probe structures. This effect is investigated numerically and experimentally in specially designed multiterminal OFETs based on optimized novel organic-semiconductor blends and bulk single crystals. Numerical simulations reveal that 4-probe FETs with long but narrow channels and wide voltage probes are especially prone to channel shunting, that can lead to mobilities overestimated by as much as 350%. In addition, the first Hall effect measurements in blended OFETs are reported and how Hall mobility can be affected by channel shunting is shown. As a solution to this problem, a numerical correction factor is introduced that can be used to obtain much more accurate experimental mobilities. This methodology is relevant to characterization of a variety of materials, including organic semiconductors, inorganic oxides, monolayer materials, as well as carbon nanotube and semiconductor nanocrystal arrays.

Record high hole mobility in polymer semiconductors via side-chain engineering.

Science.gov (United States)

Kang, Il; Yun, Hui-Jun; Chung, Dae Sung; Kwon, Soon-Ki; Kim, Yun-Hi

2013-10-09

Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.

MODELLING OF CHARGE CARRIER MOBILITY FOR TRANSPORT BETWEEN ELASTIC POLYACETYLENE-LIKE POLYMER NANORODS

Directory of Open Access Journals (Sweden)

M. Mensik

2017-03-01

Full Text Available A quantum model solving the charge carrier mobility between polyacetylene-like polymer nanorods is presented. The model assumes: a Quantum mechanical calculation of hole on-chain delocalization involving electron-phonon coupling leading to the Peierls instability, b Hybridization coupling between the polymer backbone and side-groups (or environmental states, which act as hole traps, and c Semiclassical description of the inter-chain hole transfer in an applied voltage based on Marcus theory. We have found that mobility resonantly depends on the hybridization coupling between polymer and linked groups. We observed also non-trivial mobility dependences on the difference of energies of the highest occupied molecular orbitals localized on the polymer backbone and side-groups, respectively, and hole concentration. Those findings are important for optimization of hybrid opto-electronic devices.

Contribution of current carrier mobility variation to piezo-resistive effect in SmS

International Nuclear Information System (INIS)

Vasil'ev, L.N.; Kaminskij, V.V.

1999-01-01

The value of the contribution from the change in the current carriers mobility and pressure to the piezo-resistive effect value in the materials on the basis of the samarium, monosulfide is studied. The conclusion, that the value of the piezoresistance of comprehensive compression should not exceed 7x10 -3 MPa -1 at T=300 K, experimental data [ru

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method.

Science.gov (United States)

Yuan, Yongbo; Giri, Gaurav; Ayzner, Alexander L; Zoombelt, Arjan P; Mannsfeld, Stefan C B; Chen, Jihua; Nordlund, Dennis; Toney, Michael F; Huang, Jinsong; Bao, Zhenan

2014-01-01

Organic semiconductors with higher carrier mobility and better transparency have been actively pursued for numerous applications, such as flat-panel display backplane and sensor arrays. The carrier mobility is an important figure of merit and is sensitively influenced by the crystallinity and the molecular arrangement in a crystal lattice. Here we describe the growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from a blended solution of C8-BTBT and polystyrene by using a novel off-centre spin-coating method. Combined with a vertical phase separation of the blend, the highly aligned, meta-stable C8-BTBT films provide a significantly increased thin film transistor hole mobility up to 43 cm(2) Vs(-1) (25 cm(2) Vs(-1) on average), which is the highest value reported to date for all organic molecules. The resulting transistors show high transparency of >90% over the visible spectrum, indicating their potential for transparent, high-performance organic electronics.

Two-dimensional n -InSe/p -GeSe(SnS) van der Waals heterojunctions: High carrier mobility and broadband performance

Science.gov (United States)

Xia, Cong-xin; Du, Juan; Huang, Xiao-wei; Xiao, Wen-bo; Xiong, Wen-qi; Wang, Tian-xing; Wei, Zhong-ming; Jia, Yu; Shi, Jun-jie; Li, Jing-bo

2018-03-01

Recently, constructing van der Waals (vdW) heterojunctions by stacking different two-dimensional (2D) materials has been considered to be effective strategy to obtain the desired properties. Here, through first-principles calculations, we find theoretically that the 2D n -InSe/p -GeSe(SnS) vdW heterojunctions are the direct-band-gap semiconductor with typical type-II band alignment, facilitating the effective separation of photogenerated electron and hole pairs. Moreover, they possess the high optical absorption strength (˜105 ), broad spectrum width, and excellent carrier mobility (˜103c m2V-1s-1 ). Interestingly, under the influences of the interlayer coupling and external electric field, the characteristics of type-II band alignment is robust, while the band-gap values and band offset are tunable. These results indicate that 2D n -InSe/p -GeSe(SnS) heterojunctions possess excellent optoelectronic and transport properties, and thus can become good candidates for next-generation optoelectronic nanodevices.

Hopping mobility of charge carriers in polymers in the earliest stages after their generation

International Nuclear Information System (INIS)

Tyutnev, A.P.; Subbotin, A.V.; Chekunaev, N.I.

1989-01-01

It has been found that both the photo- and the radiation conductivity of a number of polymers (primarily polyvinylcarbazole, polystyrene, and polyethylene terephthalate) are of a molecular nature, and movement of the generated charge carriers is by a hopping and not by a band mechanism. Analytical expressions for the instantaneous effective mobility and effective displacement of charge carriers in a unitary electric field were obtained in the approximation of isolated pairs of nearest neighbors for four species (monoenergetic, exponential, Gaussian, and bilevel) of energy application of hopping sites randomly distributed in space. Problems of the application of these expressions to real polymers are discussed on the example of polyvinylcarbazole

Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

International Nuclear Information System (INIS)

Nian, Qiong; Zhang, Martin Y.; Schwartz, Bradley D.; Cheng, Gary J.

2014-01-01

One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm 2 /V s at a low carrier concentration of 7.9 × 10 +19  cm −3 . This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.

Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

Energy Technology Data Exchange (ETDEWEB)

Morrison, C., E-mail: c.morrison.2@warwick.ac.uk; Casteleiro, C.; Leadley, D. R.; Myronov, M. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2016-09-05

The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm{sup 2}/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m{sub 0}. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

Science.gov (United States)

Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

2016-09-01

The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

Charge fluctuations in high-electron-mobility transistors: a review

International Nuclear Information System (INIS)

Green, F.

1993-01-01

The quasi-two-dimensional carrier population, free to move within a near-perfect crystalline matrix, is the key to remarkable improvements in signal gain, current density and quiet operation. Current-fluctuation effects are central to all of these properties. Some of these are easily understood within linear-response theory, but other fluctuation phenomena are less tractable. In particular, nonequilibrium noise poses significant theoretical challenges, both descriptive and predictive. This paper examines a few of the basic physical issues which motivate device-noise theory. The structure and operation of high-electron-mobility transistor are first reviewed. The recent nonlinear fluctuation theory of Stanton and Wilkins (1987) help to identify at least some of the complicated noise physics which can arise when carriers in GaAs-like conduction bands are subjected to high fields. Simple examples of fluctuation-dominated behaviour are discussed, with numerical illustrations. 20 refs., 9 figs

Estimation of carrier mobility at organic semiconductor/insulator interface using an asymmetric capacitive test structure

Directory of Open Access Journals (Sweden)

Rajesh Agarwal

2016-04-01

Full Text Available Mobility of carriers at the organic/insulator interface is crucial to the performance of organic thin film transistors. The present work describes estimation of mobility using admittance measurements performed on an asymmetric capacitive test structure. Besides the advantage of simplicity, it is shown that at low frequencies, the measured capacitance comes from a large area of channel making the capacitance-voltage characteristics insensitive to contact resistances. 2-D numerical simulation and experimental results obtained with Pentacene/Poly(4-vinyphenol system are presented to illustrate the operation and advantages of the proposed technique.

Ultrahigh Carrier Mobility Achieved in Photoresponsive Hybrid Perovskite Films via Coupling with Single-Walled Carbon Nanotubes

KAUST Repository

Li, Feng; Wang, Hong; Kufer, Dominik; Liang, Liangliang; Yu, Weili; Alarousu, Erkki; Ma, Chun; Li, Yangyang; Liu, Zhixiong; Liu, Changxu; Wei, Nini; Wang, Fei; Chen, Lang; Mohammed, Omar F.; Fratalocchi, Andrea; Liu, Xiaogang; Konstantatos, Gerasimos; Wu, Tao

2017-01-01

Organolead trihalide perovskites have drawn substantial interest for photovoltaic and optoelectronic applications due to their remarkable physical properties and low processing cost. However, perovskite thin films suffer from low carrier mobility as a result of their structural imperfections such as grain boundaries and pinholes, limiting their device performance and application potential. Here we demonstrate a simple and straightforward synthetic strategy based on coupling perovskite films with embedded single-walled carbon nanotubes. We are able to significantly enhance the hole and electron mobilities of the perovskite film to record-high values of 595.3 and 108.7 cm(2) V(-1) s(-1) , respectively. Such a synergistic effect can be harnessed to construct ambipolar phototransistors with an ultrahigh detectivity of 3.7 × 10(14) Jones and a responsivity of 1 × 10(4) A W(-1) , on a par with the best devices available to date. The perovskite/carbon nanotube hybrids should provide a platform that is highly desirable for fields as diverse as optoelectronics, solar energy conversion, and molecular sensing.

Ultrahigh Carrier Mobility Achieved in Photoresponsive Hybrid Perovskite Films via Coupling with Single-Walled Carbon Nanotubes

KAUST Repository

Li, Feng

2017-02-22

Organolead trihalide perovskites have drawn substantial interest for photovoltaic and optoelectronic applications due to their remarkable physical properties and low processing cost. However, perovskite thin films suffer from low carrier mobility as a result of their structural imperfections such as grain boundaries and pinholes, limiting their device performance and application potential. Here we demonstrate a simple and straightforward synthetic strategy based on coupling perovskite films with embedded single-walled carbon nanotubes. We are able to significantly enhance the hole and electron mobilities of the perovskite film to record-high values of 595.3 and 108.7 cm(2) V(-1) s(-1) , respectively. Such a synergistic effect can be harnessed to construct ambipolar phototransistors with an ultrahigh detectivity of 3.7 × 10(14) Jones and a responsivity of 1 × 10(4) A W(-1) , on a par with the best devices available to date. The perovskite/carbon nanotube hybrids should provide a platform that is highly desirable for fields as diverse as optoelectronics, solar energy conversion, and molecular sensing.

The effects of inorganic surface treatments on photogenerated carrier mobility and lifetime in PbSe quantum dot thin films

Energy Technology Data Exchange (ETDEWEB)

Goodwin, E.D.; Straus, Daniel B. [Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (United States); Gaulding, E. Ashley [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104 (United States); Murray, Christopher B. [Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kagan, Cherie R., E-mail: kagan@seas.upenn.edu [Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2016-06-01

Highlights: • Na{sub 2}Se and PbCl{sub 2} treatments modified the surface chemistry of PbSe quantum dots. • Excess Se (Pb) p-doped (n-doped) PbSe quantum dot thin films. • Carrier mobility and lifetime were studied using time-resolved microwave conductivity. • Mobility increased as the Fermi level approached the band edges. - Abstract: We used flash-photolysis, time-resolved microwave conductivity (TRMC) to probe the carrier mobility and lifetime in PbSe quantum dot (QD) thin films treated with solutions of the metal salts of Na{sub 2}Se and PbCl{sub 2}. The metal salt treatments tuned the Pb:Se stoichiometry and swept the Fermi energy throughout the QD thin film bandgap. A stoichiometric imbalance favoring excess Se heavily p-doped the QD thin film, shifted the Fermi energy toward the valence band, and yielded the highest TRMC mobility and lifetime. Introducing Pb first compensated the p-doping and shifted the Fermi level through mid-gap, decreasing the TRMC mobility. Further Pb addition created an excess of Pb, n-doped the QD thin film, moved the Fermi level to near the conduction band, and again increased the TRMC mobility. The increase in TRMC mobility as the Fermi energy was shifted toward the band edges by non-stoichiometry is consistent with the QD thin film density of states.

Comparison of mobility extraction methods based on field-effect measurements for graphene

Directory of Open Access Journals (Sweden)

Hua Zhong

2015-05-01

Full Text Available Carrier mobility extraction methods for graphene based on field-effect measurements are explored and compared according to theoretical analysis and experimental results. A group of graphene devices with different channel lengths were fabricated and measured, and carrier mobility is extracted from those electrical transfer curves using three different methods. Accuracy and applicability of those methods were compared. Transfer length method (TLM can obtain accurate density dependent mobility and contact resistance at relative high carrier density based on data from a group of devices, and then can act as a standard method to verify other methods. As two of the most popular methods, direct transconductance method (DTM and fitting method (FTM can extract mobility easily based on transfer curve of a sole graphene device. DTM offers an underestimated mobility at any carrier density owing to the neglect of contact resistances, and the accuracy can be improved through fabricating field-effect transistors with long channel and good contacts. FTM assumes a constant mobility independent on carrier density, and then can obtain mobility, contact resistance and residual density stimulations through fitting a transfer curve. However, FTM tends to obtain a mobility value near Dirac point and then overestimates carrier mobility of graphene. Comparing with the DTM and FTM, TLM could offer a much more accurate and carrier density dependent mobility, that reflects the complete properties of graphene carrier mobility.

Field-effect measurements of mobility and carrier concentration of Cu2S colloidal quantum dot thin films after ligand exchange

International Nuclear Information System (INIS)

Brewer, Adam S.; Arnold, Michael S.

2014-01-01

Colloidal quantum dots (CQDs) of copper sulfide (Cu 2 S), an earth-abundant semiconductor, have a number of intriguing applications that require knowledge of their electrical properties. Depending on stoichiometry, mobility, and surface treatment, applications include photoabsorbers for solar cells, tunable plasmonics, and counter-electrodes for polysulfate electrolytes. However, there have not been any direct measurements of electrical properties in Cu 2 S CQD thin films. Here, we exchange as synthesized dodecanethiol ligands with short ethanedithiol or ethylenediamine ligands to form thin films of coupled Cu 2 S CQDs. The mobility and carrier concentration were found to vary by ligand treatment from 10 −5 cm 2 /Vs and 10 19 holes/cm 3 for ethanedithiol ligands to 10 −3 cm 2 /Vs and 10 20 holes/cm 3 for ethylenediamine. These results are consistent with the carrier concentrations inferred from sub-bandgap surface-plasmon-resonances measured by infrared spectroscopy. These results will be useful when designing Cu 2 S materials for future applications. - Highlights: • Colloidal Cu2S quantum dots were synthesized and characterized. • Ligand exchange was performed to alter the Cu2S nanocrystal properties. • Ligand exchange was studied using photoluminescence and infrared spectroscopy. • Field effect mobility and carrier concentration were directly measured. • Carrier concentration was compared to estimates from surface plasmon resonances

Mobility enhancements for LTE-Advanced Multilayer Networks with Inter-Site Carrier Aggregation

DEFF Research Database (Denmark)

Pedersen, Klaus I.; Michaelsen, Per Henrik; Rosa, Claudio

2013-01-01

In this article we first summarize some of the most recent HetNet mobility studies for LTE-Advanced, and use these to highlight the challenges that should be further addressed in theresearch community. A state-of-the-art HetNet scenario with macros and small cells deployed on different carriers...... decide small cell addition, removal, and change without any explicit signaling of Measurement events to the network or any signaling of hand-over commands from the network. Hence, the proposed solution effectively offloads the network from having to perform frequent small cell handoff decisions...

Mobility spectrum analytical approach for intrinsic band picture of Ba(FeAs)2

Science.gov (United States)

Huynh, K. K.; Tanabe, Y.; Urata, T.; Heguri, S.; Tanigaki, K.; Kida, T.; Hagiwara, M.

2014-09-01

Unconventional high temperature superconductivity as well as three-dimensional bulk Dirac cone quantum states arising from the unique d-orbital topology have comprised an intriguing research area in physics. Here we apply a special analytical approach using a mobility spectrum, in which the carrier number is conveniently described as a function of mobility without any hypothesis, both on the types and the numbers of carriers, for the interpretations of longitudinal and transverse electric transport of high quality single crystal Ba(FeAs)2 in a wide range of magnetic fields. We show that the majority carriers are accommodated in large parabolic hole and electron pockets with very different topology as well as remarkably different mobility spectra, whereas the minority carriers reside in Dirac quantum states with the largest mobility as high as 70,000 cm2(Vs)-1. The deduced mobility spectra are discussed and compared to the reported sophisticated first principle band calculations.

Growth parameter optimization and interface treatment for enhanced electron mobility in heavily strained GaInAs/AlInAs high electron mobility transistor structures

International Nuclear Information System (INIS)

Fedoryshyn, Yuriy; Ostinelli, Olivier; Alt, Andreas; Pallin, Angel; Bolognesi, Colombo R.

2014-01-01

The optimization of heavily strained Ga 0.25 In 0.75 As/Al 0.48 In 0.52 As high electron mobility transistor structures is discussed in detail. The growth parameters and the channel layer interfaces were optimized in order to maximize the mobility of the two-dimensional electron gas. Structures composed of an 11 nm thick channel layer and a 4 nm thick spacer layer exhibited electron mobilities as high as 15 100 cm 2 /Vs and 70 000 cm 2 /Vs at 300 and 77 K, respectively, for channels including InAs strained layers. The sheet carrier density was kept above 2.5 × 10 12  cm −2 throughout the entire study

Coexistence of Dirac and massive carriers in α-(BEDT-TTF){sub 2}I{sub 3} under hydrostatic pressure

Energy Technology Data Exchange (ETDEWEB)

Navarin, Fabien; Tisserond, Emilie [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France); Auban-Senzier, Pascale, E-mail: pascale.senzier@u-psud.fr [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France); Mézière, Cécile; Batail, Patrick [MOLTECH-Anjou, UMR 6200, CNRS-Université d' Angers, Bat. K, Angers F-49045 (France); Pasquier, Claude; Monteverde, Miguel [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France)

2015-03-01

We present magnetotransport measurements of α-(BEDT-TTF){sub 2}I{sub 3} crystals under hydrostatic pressure larger than 1.5 GPa where Dirac carriers are present. We show not only the existence of high-mobility Dirac carriers but we also prove experimentally the presence of low-mobility massive carriers, in agreement with band-structure calculations.

Increase in electron mobility of InGaAs/InP composite channel high electron mobility transistor structure due to SiN passivation

International Nuclear Information System (INIS)

Liu Yuwei; Wang Hong; Radhakrishnan, K.

2007-01-01

The influence of silicon nitride passivation on electron mobility of InGaAs/InP composite channel high electron mobility transistor structure has been studied. Different from the structures with single InGaAs channel, an increase in effective mobility μ e with a negligible change of sheet carrier density n s after SiN deposition is clearly observed in the composite channel structures. The enhancement of μ e could be explained under the framework of electrons transferring from the InP sub-channel into InGaAs channel region due to the energy band bending at the surface region caused by SiN passivation, which is further confirmed by low temperature photoluminescence measurements

Dependence of the carrier mobility and trapped charge limited conduction on silver nanoparticles embedment in doped polypyrrole nanostructures

Science.gov (United States)

Biswas, Swarup; Dutta, Bula; Bhattacharya, Subhratanu

2013-10-01

The present article demonstrates an intensive study upon the temperature dependent current density (J)-voltage (V) characteristics of moderately doped polypyrrole nanostructure and its silver nanoparticles incorporated nanocomposites. Analysis of the measured J-V characteristics of different synthesized nano-structured samples within a wide temperature range revealed that the electrical conduction behavior followed a trapped charge-limited conduction and a transition of charge transport mechanism from deep exponential trap limited conduction to shallow traps limited conduction had been occurred due to the incorporation of silver nanoparticles within the polypyrrole matrix. A direct evaluation of carrier mobility as a function of electric field and temperature from the measured J-V characteristics illustrates that the incorporation of silver nanoparticles within the polypyrrole matrix enhances the carrier mobility at a large extent by reducing the concentration of traps within the polypyrrole matrix. The calculated mobility is consistent with the Poole-Frenkel form for the electrical field up to a certain temperature range. The nonlinear low temperature dependency of mobility of all the nanostructured samples was explained by Mott variable range hopping conduction mechanisms. Quantitative information regarding the charge transport parameters obtained from the above study would help to extend optimization strategies for the fabrication of new organic semiconducting nano-structured devices.

On the correct interpretation of the low voltage regime in intrinsic single-carrier devices.

Science.gov (United States)

Röhr, Jason A; Kirchartz, Thomas; Nelson, Jenny

2017-05-24

We discuss the approach of determining the charge-carrier density of a single-carrier device by combining Ohm's law and the Mott-Gurney law. We show that this approach is seldom valid, due to the fact that whenever Ohm's law is applicable the Mott-Gurney law is usually not, and vice versa. We do this using a numerical drift-diffusion solver to calculate the current density-voltage curves and the charge-carrier density, with increasing doping concentration. As this doping concentration is increased to very large values, using Ohm's law becomes a sensible way of measuring the product of mobility and doping density in the sample. However, in the high-doping limit, the current is no longer governed by space-charge and it will no longer be possible to determine the charge-carrier mobility using the Mott-Gurney law. This leaves the value for the mobility as an unknown in the mobility-doping density product in Ohm's law. We also show that, when the charge-carrier mobility for an intrinsic semiconductor is known in advance, the carrier density is underestimated up to many orders of magnitude if Ohm's law is used. We finally seek to establish a window of conditions where the two methods can be combined to yield reasonable results.

The impact of occupational load carriage on carrier mobility: a critical review of the literature.

Science.gov (United States)

Carlton, Simon D; Orr, Robin M

2014-01-01

Military personnel and firefighters are required to carry occupational loads and complete tasks in hostile and unpredictable environments where a lack of mobility may risk lives. This review critically examines the literature investigating the impacts of load carriage on the mobility of these specialist personnel. Several literature databases, reference lists, and subject matter experts were employed to identify relevant studies. Studies meeting the inclusion criteria were critiqued using the Downs and Black protocol. Inter-rater agreement was determined by Cohen's κ. Twelve original research studies, which included male and female participants from military and firefighting occupations, were critiqued (κ = .81). A review of these papers found that as the carried load weight increased, carrier mobility during aerobic tasks (like road marching) and anaerobic tasks (like obstacle course negotiation) decreased. As such, it can be concluded that the load carried by some specialist personnel may increase their occupational risk by reducing their mobility.

Theoretical modeling of influence of the structural disorder on the charge carrier mobility in triphenylene stacks

Czech Academy of Sciences Publication Activity Database

Mikolajczyk, M.; Toman, Petr; Bartkowiak, W.

2010-01-01

Roč. 485, 1-3 (2010), s. 253-257 ISSN 0009-2614 R&D Projects: GA MŠk MEB050815; GA AV ČR IAA401770601 Institutional research plan: CEZ:AV0Z40500505 Keywords : triphenylene * charge carrier mobility * tight-binding approximation Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.282, year: 2010

Theoretical prediction of high electron mobility in multilayer MoS2 heterostructured with MoSe2

Science.gov (United States)

Ji, Liping; Shi, Juan; Zhang, Z. Y.; Wang, Jun; Zhang, Jiachi; Tao, Chunlan; Cao, Haining

2018-01-01

Two-dimensional (2D) MoS2 has been considered to be one of the most promising semiconducting materials with the potential to be used in novel nanoelectronic devices. High carrier mobility in the semiconductor is necessary to guarantee a low power dissipation and a high switch speed of the corresponding electronic device. Strain engineering in 2D materials acts as an important approach to tailor and design their electronic and carrier transport properties. In this work, strain is introduced to MoS2 through perpendicularly building van der Waals heterostructures MoSe2-MoS2. Our first-principles calculations demonstrate that acoustic-phonon-limited electron mobility can be significantly enhanced in the heterostructures compared with that in pure multilayer MoS2. It is found that the effective electron mass and the deformation potential constant are relatively smaller in the heterostructures, which is responsible for the enhancement in the electron mobility. Overall, the electron mobility in the heterostructures is about 1.5 times or more of that in pure multilayer MoS2 with the same number of layers for the studied structures. These results indicate that MoSe2 is an excellent material to be heterostructured with multilayer MoS2 to improve the charge transport property.

The Complementary Relationship between Organizational Architecture and Organizational Agility An Empirical Study in Mobile Carriers of Erbil – Iraq

OpenAIRE

Laith Ali Yousif Al-Hakim; Thabit Hassan Thabit; Hamed Adel Abbas Al-Nasrawi

2017-01-01

The present research aims to investigate the relationship between organizational architecture and organizational agility in the mobile carriers of Erbil in Iraq. A questionnaire was conducted on mobile companies based on a random sampling technique. The results show there is a statistically significance and positive relation between organizational architecture and organizational agility. The results also indicated that organizational architecture has a statistically significant and direct pos...

Ultra-high carrier mobility InSb film by rapid thermal annealing on glass substrate

Directory of Open Access Journals (Sweden)

Charith Jayanada Koswaththage

2016-11-01

Full Text Available InSb films were deposited on both mica and glass substrates using thermal evaporation and subjected to FA or RTA. Crystallinity, composition and electrical properties were investigated. High Hall electron mobility as high as 25,000 cm2/(Vs was obtained with the capped InSb film by keeping the In:Sb ratio after RTA at 520°C for 30 sec or more without adopting epitaxial growth on glass.

Improvement in carrier mobility and photovoltaic performance through random distribution of segments of linear and branched side chains

Energy Technology Data Exchange (ETDEWEB)

Egbe, Daniel A.M.; Adam, Getachew; Pivrikas, Almantas; Ulbricht, Christoph; Ramil, Alberto M.; Sariciftci, Niyazi Serdar [Johannes Kepler Univ., Linz (AT). Linz Inst. for Organic Solar Cells (LIOS); Hoppe, Harald [Technische Univ. Ilmenau (Germany). Inst. of Physics and Inst. of Micro- and Nanotechnologies; Rathgeber, Silke [Mainz Univ. (Germany). Inst. of Physics

2010-07-01

The random distribution of segments of linear octyloxy side chains and of branched 2-ethylhexyloxy side chains, on the backbone of anthracene containing poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) (PPE-PPV) has resulted in a side chain based statistical copolymer, denoted AnE-PVstat, showing optimized features as compared to the well defined homologues AnE-PVaa, -ab, -ba and -bb, whose constitutional units are incorporated into its backbone. WAXS studies on AnE-P's demonstrate the highest degree of order at the self-assembly state of AnE-PVstat, which is confirmed by its highly structured thin film absorption band. Electric field independent charge carrier mobility ({mu}{sub hole}) for AnE-PVstat was demonstrated by CELIV and OFET measurements, both methods resulting in similar {mu}{sub hole} values of up to 5.43 x 10{sup -4} cm{sup 2}/Vs. Upon comparison, our results show that charge carrier mobility as measured by CELIV technique is predominantly an intrachain process and less an interchain one, which is in line with past photoconductivity results from PPE-PPV based materials. The present side chain distribution favors efficient solar cell active layer phase separation. As a result, a smaller amount of PC{sub 60}BM is needed to achieve relatively high energy conversion efficiencies above 3 %. The efficiency of {eta}{sub AM1.5} {approx} 3.8 % obtained for AnE-PVstat:PC{sub 60}BM blend is presently the state-of-art value for PPV-based materials. (orig.)

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

KAUST Repository

Jang, Ji-Wook; Friedrich, Dennis; Mü ller, Sö nke; Lamers, Marlene; Hempel, Hannes; Lardhi, Sheikha F.; Cao, Zhen; Harb, Moussab; Cavallo, Luigi; Heller, René ; Eichberger, Rainer; van de Krol, Roel; Abdi, Fatwa F.

2017-01-01

and are relatively cheap, are particularly interesting, but high efficiency is still hindered by the poor carrier transport properties (i.e., carrier mobility and lifetime). Here, a mild hydrogen treatment is introduced to bismuth vanadate (BiVO4), which is one

Investigations of the drift mobility of carriers and density of states in nanocrystalline CdS thin films

Energy Technology Data Exchange (ETDEWEB)

Singh, Baljinder [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Department of Physics, Panjab University, Chandigarh 160014 (India); Singh, Janpreet; Kaur, Jagdish [Department of Physics, Panjab University, Chandigarh 160014 (India); Moudgil, R.K. [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Tripathi, S.K., E-mail: surya@pu.ac.in [Department of Physics, Panjab University, Chandigarh 160014 (India)

2016-06-01

Nanocrystalline Cadmium Sulfide (nc-CdS) thin films have been prepared on well-cleaned glass substrate at room temperature (300 K) by thermal evaporation technique using inert gas condensation (IGC) method. X-ray diffraction (XRD) analysis reveals that the films crystallize in hexagonal structure with preferred orientation along [002] direction. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) studies reveal that grains are spherical in shape and uniformly distributed over the glass substrates. The optical band gap of the film is estimated from the transmittance spectra. Electrical parameters such as Hall coefficient, carrier type, carrier concentration, resistivity and mobility are determined using Hall measurements at 300 K. Transit time and mobility are estimated from Time of Flight (TOF) transient photocurrent technique in gap cell configuration. The measured values of electron drift mobility from TOF and Hall measurements are of the same order. Constant Photocurrent Method in ac-mode (ac-CPM) is used to measure the absorption spectra in low absorption region. By applying derivative method, we have converted the measured absorption data into a density of states (DOS) distribution in the lower part of the energy gap. The value of Urbach energy, steepness parameter and density of defect states have been calculated from the absorption and DOS spectra.

Mobility of charge carriers in electron-irradiated crystals of n-type Hg0.8Cd0.2Te

International Nuclear Information System (INIS)

Voitsekhovskii, A.V.; Kiryushkin, E.M.; Kokhanenko, A.P.; Kurbanov, K.R.; Lilenko, Yu.V.

1988-01-01

We present the results of an investigation of the behavior of the mobility of the charge carriers in Hg 1-x Cd x Te crystals with n-type conduction as a function of the dose of irradiation by electrons with an energy of 3.0 MeV at 300 K and the initial content of defects in the material. The complex character of the variation of the mobility of the electrons as a function of the dose observed when crystals of n-Hg 1-x Cd x Te (x ∼ 0.20) with different initial concentrations of defects are irradiated by fast electrons has been attributed to the influence of the factors of the shielding of the ionized scattering centers by electrons and the additional scattering of the charge carriers on the radiation defects. Good agreement between the experimental and calculated plots of the dependence of the mobility of electrons on the irradiation dose has been obtained with consideration of a model of the simultaneous introduction of donor (single charged) and acceptor (doubly charged) defects into a narrow-band semiconductor characterized by a degenerate and nonparabolic conduction band

On the correct interpretation of the low voltage regime in intrinsic single-carrier devices

International Nuclear Information System (INIS)

Röhr, Jason A; Nelson, Jenny; Kirchartz, Thomas

2017-01-01

We discuss the approach of determining the charge-carrier density of a single-carrier device by combining Ohm’s law and the Mott–Gurney law. We show that this approach is seldom valid, due to the fact that whenever Ohm’s law is applicable the Mott–Gurney law is usually not, and vice versa. We do this using a numerical drift-diffusion solver to calculate the current density–voltage curves and the charge-carrier density, with increasing doping concentration. As this doping concentration is increased to very large values, using Ohm’s law becomes a sensible way of measuring the product of mobility and doping density in the sample. However, in the high-doping limit, the current is no longer governed by space-charge and it will no longer be possible to determine the charge-carrier mobility using the Mott–Gurney law. This leaves the value for the mobility as an unknown in the mobility-doping density product in Ohm’s law. We also show that, when the charge-carrier mobility for an intrinsic semiconductor is known in advance, the carrier density is underestimated up to many orders of magnitude if Ohm’s law is used. We finally seek to establish a window of conditions where the two methods can be combined to yield reasonable results. (paper)

Wafer-scale characterization of carrier dynamics in graphene

DEFF Research Database (Denmark)

Buron, Jonas Christian Due; Petersen, Dirch Hjorth; Bøggild, Peter

2015-01-01

The electronic properties of single-layer graphene, such as surface conductance, carrier concentration, scattering time and mobility, can be characterized in a noncontact manner by THz time-domain spectroscopy. Standard spectroscopic imaging reveals the AC conductance over large areas with a few...... hundred μm resolution, and spectroscopic imaging on back-gated graphene allows for extraction of both the carrier concentration and the mobility. We find that spatial variations of the conductance of single-layer CVD-grown graphene are predominantly due to variations in mobility rather than in carrier...

Understanding mobility degeneration mechanism in organic thin-film transistors (OTFT)

Science.gov (United States)

Wang, Wei; Wang, Long; Xu, Guangwei; Gao, Nan; Wang, Lingfei; Ji, Zhuoyu; Lu, Congyan; Lu, Nianduan; Li, Ling; Liu, Miwng

2017-08-01

Mobility degradation at high gate bias is often observed in organic thin film transistors. We propose a mechanism for this confusing phenomenon, based on the percolation theory with the presence of disordered energy landscape with an exponential density of states. Within a simple model we show how the surface states at insulator/organic interface trap a portion of channel carriers, and result in decrease of mobility as well as source/drain current with gate voltage. Depending on the competition between the carrier accumulation and surface trapping effect, two different carrier density dependences of mobility are obtained, in excellent agreement with experiment data.

Use of natural gas, methanol, and ethanol fuel emulsions as environmentally friendly energy carriers for mobile heat power plants

Science.gov (United States)

Likhanov, V. A.; Lopatin, O. P.

2017-12-01

The need for using environmentally friendly energy carriers for mobile heat power plants (HPPs) is grounded. Ecologically friendly sources of energy, such as natural gas as well as renewable methyl and ethyl alcohols, are investigated. In order to develop, determine, and optimize the composition of environmentally friendly energy carriers for an HPP, the latter has been tested when working on diesel fuel (DF), compressed natural gas (CNG), and methanol and ethanol fuel emulsions (MFE, EFE). It has been experimentally established that, for the application of environmentally friendly energy carriers for a 4Ch 11.0/12.5 diesel engine of a mobile fuel and power plant, it is necessary to maintain the following ratio of components when working on CNG: 80% gas and 20% DF primer portion. When working on an alcohol mixture, emulsions of the following composition were used: 25% alcohol (methanol or ethanol), 0.5% detergent-dispersant additive succinimide C-5A, 7% water, and 67.5% DF. When this diesel passed from oil DF to environmentally friendly energy sources, it allowed for the reduction of the content of exhaust gases (EG) (1) when working on CNG with recirculation of exhaust gases (EGR) (recirculation was used to eliminate the increased amount of nitric oxides by using CNG): carbon black by 5.8 times, carbon dioxide by 45.9%, and carbon monoxide by 23.8%; (2) when working on MFE: carbon black by 6.4 times, nitrogen oxides by 29.6%, carbon dioxide by 10.1%, and carbon oxide by 47.6%; (3) when working on EFE: carbon black by 4.8 times; nitrogen oxides by 40.3%, carbon dioxide by 26.6%, and carbon monoxide by 28.6%. The prospects of use of environmentally friendly energy carriers in diesels of mobile HPPs, such as natural gas, ethanol, and methanol, has been determined.

Mobiles Robotersystem

OpenAIRE

Schmierer, G.; Wolf, A.

1999-01-01

DE 19816893 A UPAB: 20000203 NOVELTY - An optical and or acoustic noticeable advertising and or information carrier (10) is fixed permitting detachment in such a manner at the mobile platform (8), that the advertising and or information carrier does not impair the movability of the mobile platform. The advertising is provided at an exposed place on the mobile platform. USE - Advertising or information communication. ADVANTAGE - Advertising or information is imparted in prominent positioning w...

Modelling of charge carrier mobility for transport between elastic polyacetylene-like polymer nanorods

Czech Academy of Sciences Publication Activity Database

Menšík, Miroslav; Sun, S. J.; Toman, Petr; Král, Karel

2017-01-01

Roč. 61, č. 2 (2017), s. 127-135 ISSN 0862-5468 R&D Projects: GA MŠk(CZ) LD14011; GA ČR(CZ) GA15-05095S Grant - others:European Commission(XE) COST Action MP1202 HINT; AV ČR(CZ) KONNECT-007 Program:Bilaterální spolupráce Institutional support: RVO:61389013 ; RVO:68378271 Keywords : charge carrier mobility * polymers * electron-phonon coupling Subject RIV: CF - Physical ; Theoretical Chemistry; CF - Physical ; Theoretical Chemistry (FZU-D) OBOR OECD: Physical chemistry; Physical chemistry (FZU-D) Impact factor: 0.439, year: 2016

Growth of high mobility GaN and AlGaN/GaN high electron mobility transistor structures on 4H-SiC by ammonia molecular-beam epitaxy

International Nuclear Information System (INIS)

Webb, James B.; Tang, H.; Bardwell, J. A.; Coleridge, P.

2001-01-01

Ammonia molecular-beam epitaxy has been used to grow high-quality epilayers of GaN and AlGaN/GaN heterostructure field-effect transistor (HFET) structures on insulating 4H-SiC. The growth process, which used a magnetron sputter epitaxy deposited buffer layer of AlN, has been described previously. Ex situ pretreatment of the SiC substrate was found to be unnecessary. For a single 2.0 μm thick silicon doped epilayer, a room temperature (RT) electron mobility of 500 cm2/Vs was measured at a carrier density of 6.6x10 16 cm -3 . For the HFET structure, a room temperature mobility of 1300 cm2/Vs at a sheet carrier density of 3.3x10 12 cm -2 was observed, increasing to 11000 cm2/Vs at 77 K. The surface morphology of the layers indicated a coalesced mesa structure similar to what we observed for growth on sapphire, but with a lower overall defect density and correspondingly larger grain size. The observation of well-resolved Shubnikov de Haas oscillations at fields as low as 3 T indicated a relatively smooth interface. [copyright] 2001 American Institute of Physics

Dithiopheneindenofluorene (TIF) Semiconducting Polymers with Very High Mobility in Field-Effect Transistors

KAUST Repository

Chen, Hu

2017-07-19

The charge-carrier mobility of organic semiconducting polymers is known to be enhanced when the energetic disorder of the polymer is minimized. Fused, planar aromatic ring structures contribute to reducing the polymer conformational disorder, as demonstrated by polymers containing the indacenodithiophene (IDT) repeat unit, which have both a low Urbach energy and a high mobility in thin-film-transistor (TFT) devices. Expanding on this design motif, copolymers containing the dithiopheneindenofluorene repeat unit are synthesized, which extends the fused aromatic structure with two additional phenyl rings, further rigidifying the polymer backbone. A range of copolymers are prepared and their electrical properties and thin-film morphology evaluated, with the co-benzothiadiazole polymer having a twofold increase in hole mobility when compared to the IDT analog, reaching values of almost 3 cm2 V−1 s−1 in bottom-gate top-contact organic field-effect transistors.

The influence of surfaces on the transient terahertz conductivity and electron mobility of GaAs nanowires

International Nuclear Information System (INIS)

Joyce, Hannah J; Baig, Sarwat A; Parkinson, Patrick; Davies, Christopher L; Boland, Jessica L; Herz, Laura M; Johnston, Michael B; Tan, H Hoe; Jagadish, Chennupati

2017-01-01

Bare unpassivated GaAs nanowires feature relatively high electron mobilities (400–2100 cm 2 V −1 s −1 ) and ultrashort charge carrier lifetimes (1–5 ps) at room temperature. These two properties are highly desirable for high speed optoelectronic devices, including photoreceivers, modulators and switches operating at microwave and terahertz frequencies. When engineering these GaAs nanowire-based devices, it is important to have a quantitative understanding of how the charge carrier mobility and lifetime can be tuned. Here we use optical-pump–terahertz-probe spectroscopy to quantify how mobility and lifetime depend on the nanowire surfaces and on carrier density in unpassivated GaAs nanowires. We also present two alternative frameworks for the analysis of nanowire photoconductivity: one based on plasmon resonance and the other based on Maxwell–Garnett effective medium theory with the nanowires modelled as prolate ellipsoids. We find the electron mobility decreases significantly with decreasing nanowire diameter, as charge carriers experience increased scattering at nanowire surfaces. Reducing the diameter from 50 nm to 30 nm degrades the electron mobility by up to 47%. Photoconductivity dynamics were dominated by trapping at saturable states existing at the nanowire surface, and the trapping rate was highest for the nanowires of narrowest diameter. The maximum surface recombination velocity, which occurs in the limit of all traps being empty, was calculated as 1.3  ×  10 6 cm s −1 . We note that when selecting the optimum nanowire diameter for an ultrafast device, there is a trade-off between achieving a short lifetime and a high carrier mobility. To achieve high speed GaAs nanowire devices featuring the highest charge carrier mobilities and shortest lifetimes, we recommend operating the devices at low charge carrier densities. (paper)

High-mobility ultrathin semiconducting films prepared by spin coating

Science.gov (United States)

Mitzi, David B.; Kosbar, Laura L.; Murray, Conal E.; Copel, Matthew; Afzali, Ali

2004-03-01

The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (~50Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105Acm-2) and mobilities greater than 10cm2V-1s-1-an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

International Nuclear Information System (INIS)

Khanal, D. R.; Levander, A. X.; Wu, J.; Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.

2011-01-01

We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy α particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

Strain engineering on electronic structure and carrier mobility in monolayer GeP3

Science.gov (United States)

Zeng, Bowen; Long, Mengqiu; Zhang, Xiaojiao; Dong, Yulan; Li, Mingjun; Yi, Yougen; Duan, Haiming

2018-06-01

Using density functional theory coupled with the Boltzmann transport equation with relaxation time approximation, we have studied the strain effect on the electronic structure and carrier mobility of two-dimensional monolayer GeP3. We find that the energies of valence band maximum and conduction band minimum are nearly linearly shifted with a biaxial strain in the range of  ‑4% to 6%, and the band structure experiences a remarkable transition from semiconductor to metal with the appropriate compression (‑5% strain). Under biaxial strain, the mobility of the electron and hole in monolayer GeP3 reduces and increases by more than one order of magnitude, respectively. It is suggested that it is possible to perform successive transitions from an n-type semiconductor (‑4% strain) to a good performance p-semiconductor (+6% strain) by applying strain in monolayer GeP3, which is potentially useful for flexible electronics and nanosized mechanical sensors.

Cyclotron resonance spectroscopy of a high-mobility two-dimensional electron gas from 0.4 to 100 K at high filling factors

Energy Technology Data Exchange (ETDEWEB)

Curtis, Jeremy A. [Univ. of Alabama, Birmingham, AL (United States); Tokumoto, Takahisa [Univ. of Alabama, Birmingham, AL (United States); Cherian, Judy G. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Kuno, J. [Rice Univ., Houston, TX (United States); Reno, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); McGill, Stephen A. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Karaiskaj, Denis [Univ. of South Florida, Tampa, FL (United States); Hilton, David J. [Univ. of Alabama, Birmingham, AL (United States)

2015-10-01

We have studied the cyclotron mobility of a Landau-quantized two-dimensional electron gas as a function of temperature (0.4 --100 K) at a fixed magnetic field (1.25 T) using terahertz time-domain spectroscopy in a sample with a low frequency mobility of μ_dc = 3.6 x 10⁶ cm² V^-1 s^-1 and a carrier concentration of ns = 2 x 10₆ cm^-2. The low temperature mobility in this sample results from both impurity scattering and acoustic deformation potential scattering, with μ$-1\\atop{CR}$ ≈ (2.1 x 10⁵ cm² V^-1 s^-1)^-1 + (3.8 x 10^-8 V sK^-1 cm^-2 x T)^-1 at low temperatures. Above 50 K, the cyclotron oscillations show a strong reduction in both the oscillation amplitude and lifetime that is dominated by the contribution due to polar optical phonons. These results suggest that electron dephasing times as long as ~ 300 ps are possible even at this high lling factor (v = 6:6) in higher mobility samples (> 10⁷ cm² V^-1 s^-1) that have lower impurity concentrations and where the cyclotron mobility at this carrier concentration would be limited by acoustic deformation potential scattering.

Insights into the charge carrier terahertz mobility in polyfluorenes from large-scale atomistic simulations and time-resolved terahertz spectroscopy

Czech Academy of Sciences Publication Activity Database

Vukmirović, N.; Ponseca, C.S.; Němec, Hynek; Yartsev, A.; Sundström, V.

2012-01-01

Roč. 116, č. 37 (2012), s. 19665-1972 ISSN 1932-7447 Institutional research plan: CEZ:AV0Z10100520 Keywords : charge carrier mobility * time-resolved terahertz spectroscopy * multiscale atomistic calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.814, year: 2012

Carrier transport in amorphous silicon utilizing picosecond photoconductivity

Science.gov (United States)

Johnson, A. M.

1981-08-01

The development of a high-speed electronic measurement capability permitted the direct observation of the transient photoresponse of amorphous silicon (a-Si) with a time resolution of approximately 10ps. This technique was used to measure the initial mobility of photogenerated (2.1eV) free carriers in three types of a-Si having widely different densities of structural defects (i.e., as prepared by: (1) RF glow discharge (a-Si:H); (2) chemical vapor deposition; and (3) evaporation in ultra-high vacuum). In all three types of a-Si, the same initial mobility of approximately 1 cu cm/Vs at room temperature was found. This result tends to confirm the often-made suggestion that the free carrier mobility is determined by the influence of shallow states associated with the disorder in the random atomic network, and is an intrinsic property of a-Si which is unaffected by the method of preparation. The rate of decay of the photocurrent correlates with the density of structural defects and varies from 4ps to 200ps for the three types of a-Si investigated. The initial mobility of a-Si:H was found to be thermally activated. The possible application of extended state transport controlled by multiple trapping and small polaron formation is discussed.

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene.

Science.gov (United States)

Tsutsui, Yusuke; Schweicher, Guillaume; Chattopadhyay, Basab; Sakurai, Tsuneaki; Arlin, Jean-Baptiste; Ruzié, Christian; Aliev, Almaz; Ciesielski, Artur; Colella, Silvia; Kennedy, Alan R; Lemaur, Vincent; Olivier, Yoann; Hadji, Rachid; Sanguinet, Lionel; Castet, Frédéric; Osella, Silvio; Dudenko, Dmytro; Beljonne, David; Cornil, Jérôme; Samorì, Paolo; Seki, Shu; Geerts, Yves H

2016-09-01

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Complementary Relationship between Organizational Architecture and Organizational Agility An Empirical Study in Mobile Carriers of Erbil – Iraq

Directory of Open Access Journals (Sweden)

Laith Ali Yousif Al-Hakim

2017-02-01

Full Text Available The present research aims to investigate the relationship between organizational architecture and organizational agility in the mobile carriers of Erbil in Iraq. A questionnaire was conducted on mobile companies based on a random sampling technique. The results show there is a statistically significance and positive relation between organizational architecture and organizational agility. The results also indicated that organizational architecture has a statistically significant and direct positive effect on organizational agility. Finally, the researchers draw an overall conclusion from the research as a whole.

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

KAUST Repository

Jang, Ji-Wook

2017-08-25

Widespread application of solar water splitting for energy conversion is largely dependent on the progress in developing not only efficient but also cheap and scalable photoelectrodes. Metal oxides, which can be deposited with scalable techniques and are relatively cheap, are particularly interesting, but high efficiency is still hindered by the poor carrier transport properties (i.e., carrier mobility and lifetime). Here, a mild hydrogen treatment is introduced to bismuth vanadate (BiVO4), which is one of the most promising metal oxide photoelectrodes, as a method to overcome the carrier transport limitations. Time-resolved microwave and terahertz conductivity measurements reveal more than twofold enhancement of the carrier lifetime for the hydrogen-treated BiVO4, without significantly affecting the carrier mobility. This is in contrast to the case of tungsten-doped BiVO4, although hydrogen is also a donor type dopant in BiVO4. The enhancement in carrier lifetime is found to be caused by significant reduction of trap-assisted recombination, either via passivation or reduction of deep trap states related to vanadium antisite on bismuth or vanadium interstitials according to density functional theory calculations. Overall, these findings provide further insights on the interplay between defect modulation and carrier transport in metal oxides, which benefit the development of low-cost, highly-efficient solar energy conversion devices.

Anisotropic mobility and carrier dynamics in the β-type BEDT-TTF salts as studied by inter-layer transverse magnetoresistance

Directory of Open Access Journals (Sweden)

Shigeharu Sugawara and Masafumi Tamura

2013-01-01

Full Text Available A new method to estimate an in-plane conduction anisotropy in a quasi-two-dimensional (q2D layered conductor by measuring the inter-layer transverse magnetoresistance is proposed. We applied this method to layered organic conductors β-(BEDT-TTF2X (BEDT-TTF = bis(ethylenedithiotetrathiafulvalene, C10H8S8; X = IBr2, I2Br by applying magnetic field rotating within the basal plane at 4.2 K. We found the anisotropic behaviour of carrier mobility μ. From this, anomalous distribution of carrier lifetime τ on the Fermi surface is derived, by the use of Fermi surface data reported for the materials. Calculations of the non-uniform susceptibility χ0(q suggest that carrier scattering is enhanced at specific k-points related to partial nesting of the Fermi surface. The present method is thus demonstrated to be an efficient experimental tool to elucidate anisotropic carrier dynamics in q2D conductors.

Role of dislocations and carrier concentration in limiting the electron mobility of InN films grown by plasma assisted molecular beam epitaxy

Science.gov (United States)

Tangi, Malleswararao; De, Arpan; Shivaprasad, S. M.

2018-01-01

We report the molecular beam epitaxy growth of device quality InN films on GaN epilayer and nano-wall network (NWN) templates deposited on c-sapphire by varying the film thickness up to 1 μm. The careful experiments are directed towards obtaining high mobility InN layers having a low band gap with improved crystal quality. The dislocation density is quantified by using high resolution X-ray diffraction rocking curve broadening values of symmetric and asymmetric reflections, respectively. We observe that the dislocation density of the InN films grown on GaN NWN is less than that of the films grown on the GaN epilayer. This is attributed to the nanoepitaxial lateral overlayer growth (ELOG) process, where the presence of voids at the interface of InN/GaN NWN prevents the propagation of dislocation lines into the InN epilayers, thereby causing less defects in the overgrown InN films. Thus, this new adaptation of the nano-ELOG growth process enables us to prepare InN layers with high electron mobility. The obtained electron mobility of 2121 cm2/Vs for 1 μm thick InN/GaN NWN is comparable with the literature values of similar thickness InN films. Furthermore, in order to understand the reasons that limit electron mobility, the charge neutrality condition is employed to study the variation of electron mobility as a function of dislocation density and carrier concentration. Overall, this study provides a route to attaining improved crystal quality and electronic properties of InN films.

High mobility In0.75Ga0.25As quantum wells in an InAs phonon lattice

Science.gov (United States)

Chen, C.; Holmes, S. N.; Farrer, I.; Beere, H. E.; Ritchie, D. A.

2018-03-01

InGaAs based devices are great complements to silicon for CMOS, as they provide an increased carrier saturation velocity, lower operating voltage and reduced power dissipation (International technology roadmap for semiconductors (www.itrs2.net)). In this work we show that In0.75Ga0.25As quantum wells with a high mobility, 15 000 to 20 000 cm2 V-1 s-1 at ambient temperature, show an InAs-like phonon with an energy of 28.8 meV, frequency of 232 cm-1 that dominates the polar-optical mode scattering from  ˜70 K to 300 K. The measured optical phonon frequency is insensitive to the carrier density modulated with a surface gate or LED illumination. We model the electron scattering mechanisms as a function of temperature and identify mechanisms that limit the electron mobility in In0.75Ga0.25As quantum wells. Background impurity scattering starts to dominate for temperatures  <100 K. In the high mobility In0.75Ga0.25As quantum well, GaAs-like phonons do not couple to the electron gas unlike the case of In0.53Ga0.47As quantum wells.

Improvement in carrier mobility and photovoltaic performance through random distribution of segments of linear and branched side chains

Czech Academy of Sciences Publication Activity Database

Egbe, D. A. M.; Adam, G.; Pivrikas, A.; Ramil, A. M.; Birckner, E.; Cimrová, Věra; Hoppe, H.; Sariciftci, N. S.

2010-01-01

Roč. 20, č. 43 (2010), s. 9726-9734 ISSN 0959-9428 R&D Projects: GA MŠk(CZ) 1M06031 Institutional research plan: CEZ:AV0Z40500505 Keywords : poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) * solar cells * charge carrier mobility Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.101, year: 2010

High-mobility ultrathin semiconducting films prepared by spin coating.

Science.gov (United States)

Mitzi, David B; Kosbar, Laura L; Murray, Conal E; Copel, Matthew; Afzali, Ali

2004-03-18

The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (approximately 50 A), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS(2-x)Se(x) films, which exhibit n-type transport, large current densities (>10(5) A cm(-2)) and mobilities greater than 10 cm2 V(-1) s(-1)--an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

High mobility and high concentration Type-III heterojunction FET

Science.gov (United States)

Tsu, R.; Fiddy, M. A.; Her, T.

2018-02-01

The PN junction was introduced in transistors by doping, resulting in high losses due to Coulomb scattering from the dopants. The MOSFET introduced carriers in the form of electrons and holes with an applied bias to the oxide barrier, resulting in carrier transfer without doping. This avoids high scattering losses and dominates the IC industries. With heterojunctions having valence-band maxima near and even above the conduction-band minimum in the formation of Type-III superlattices, very useful devices, introduced by Tsu, Sai-Halacz, and Esaki, soon followed. If the layer thicknesses are more than the carrier mean-free-path, incoherent scattering results in the formation of carrier transfer via diffusion instead of opening up new energy gaps. The exploitation of carriers without scattering represents a new and significant opportunity in what we call a Broken Gap Heterojunction FET.

Behaviour of tetraalkylammonium ions in high-field asymmetric waveform ion mobility spectrometry.

Science.gov (United States)

Aksenov, Alexander A; Kapron, James T

2010-05-30

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an ion-filtering technique recently adapted for use with liquid chromatography/mass spectrometry (LC/MS) to remove interferences during analysis of complex matrices. This is the first systematic study of a series of singly charged tetraalkylammonium ions by FAIMS-MS. The compensation voltage (CV) is the DC offset of the waveform which permits the ion to emerge from FAIMS and it was determined for each member of the series under various conditions. The electrospray ionization conditions explored included spray voltage, vaporizer temperature, and sheath and auxiliary gas pressure. The FAIMS conditions explored included carrier gas flow rate, electrode temperature and composition of the carrier gas. Optimum desolvation was achieved using sufficient carrier gas (flow rate > or = 2 L/min) to ensure stable response. Low-mass ions (m/z 100-200) are more susceptible to changes in electrode temperature and gas composition than high mass ions (m/z 200-700). As a result of this study, ions are reliably analyzed using standard FAIMS conditions (dispersion voltage -5000 V, carrier gas flow rate 3 L/min, 50% helium/50%nitrogen, inner electrode temperature 70 degrees C and outer electrode temperature 90 degrees C). Variation of FAIMS conditions may be of great use for the separation of very low mass tetraalkylammonium (TAA) ions from other TAA ions. The FAIMS conditions do not appear to have a major effect on higher mass ions. Copyright 2010 John Wiley & Sons, Ltd.

Band gap tunning in BN-doped graphene systems with high carrier mobility

KAUST Repository

Kaloni, T. P.

2014-02-17

Using density functional theory, we present a comparative study of the electronic properties of BN-doped graphene monolayer, bilayer, trilayer, and multilayer systems. In addition, we address a superlattice of pristine and BN-doped graphene. Five doping levels between 12.5% and 75% are considered, for which we obtain band gaps from 0.02 eV to 2.43 eV. We demonstrate a low effective mass of the charge carriers.

Investigation of high mobility pseudomorphic SiGe p-channels in Si MOSFETS at low and high electric fields

International Nuclear Information System (INIS)

Palmer, Martin John

2001-01-01

Silicon Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) for high speed, high current applications are rapidly approaching the physical and financial limits of the technology. This opens opportunities for the incorporation of materials with intrinsically better transport characteristics. An alloy of silicon and germanium is one such material that is gaining much recognition as the active component of MOSFETs and as the secondary structures (such as the gate electrode). This work examines a batch of buried channel Si 0.64 Ge 0.36 p-MOSFETs, with a minimum effective length of 0.35 μm, under different bias conditions and at different temperatures. High current and transconductance enhancements are apparent at long gate lengths. The carrier mobility is up to a factor of 2.5 times that of silicon at room temperature and 7.5 times at 4 K. A clear trend of decreasing peak mobility with decreasing silicon cap thickness is evident. Simulations show that scattering caused by the roughness of the SiO 2 /Si interface dominates, rather than alloy scattering or Si/SiGe roughness, even for a buried channel. This scattering increases with the proximity of the carriers to the interface. An increase of interface trap density with decreasing cap thickness, demonstrates that segregated germanium exists some distance into the cap and interferes with the oxidation process. This will increase scattering through increased SiO 2 /Si roughness and increased trapped charge. The short channel, high field results are comparable or slightly worse than those of silicon due to lower saturation drift velocity. However, fitting to a drift-diffusion model shows an apparent increase in saturation velocity for short channels, especially at low temperatures. This effect correlates with the low field mobility and is greater for devices containing SiGe. This is an indication of velocity overshoot, which may enhance the performance of SiGe MOSFETs at deep submicron gate lengths. (author)

Measurement of the drift mobilities and the mobility-lifetime products of charge carriers in a CdZnTe crystal by using a transient pulse technique

International Nuclear Information System (INIS)

Cho, H Y; Kwon, Y K; Lee, C S; Lee, J H; Moon, J Y

2011-01-01

In this work we present results on the measurement of the drift mobility and the mobility-lifetime product of charge carriers in a 16-pixellated CdZnTe detector. For the determination of an interaction position based on the pulse rise-time method in a CZT detector, it is necessary to characterize the transport properties governed by drift mobility and lifetime for electrons and holes. In order to extract the transport properties of an electron and a hole, we bombarded 5.5-MeV alpha particles from a 241 Am source and 81-keV gamma rays emitted from a 133 Ba source on the negatively biased contact of the CZT detector. A time-of-flight (TOF) method was used to measure the electron drift mobility at room temperature whose value turned out to be 906.4 cm 2 /Vc s. With the Hecht's equation, the electron mobility-lifetime product was also determined from the bias-dependent alpha response and was equal to (9.88 ± 2.33) x 10 -3 cm 2 /V. On the other hand, the hole mobility-lifetime product was evaluated by a model based on the average charge collection efficiency which accounts for the absorption probability with a given photon energy. By using a single parameter fitting of the model, we obtained the hole mobility-lifetime product of (8.28 ± 0.17) x 10 -4 cm 2 /V.

Charge-carrier mobilities in disordered semiconducting polymers : effects of carrier density and electric field

NARCIS (Netherlands)

Meisel, K.D.; Pasveer, W.F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P.A.; Blom, P.W.M.; Leeuw, D.M. de; Michels, M.A.J.

2006-01-01

We model charge transport in disordered semiconducting polymers by hopping of charge carriers on a square lattice of sites with Gaussian on-site energy disorder, using Fermi-Dirac statistics. From numerically exact solutions of the Master equation, we study the dependence of the charge-carrier

Hall mobility reduction in single-crystalline silicon gradually compensated by thermal donors activation

Science.gov (United States)

Veirman, J.; Dubois, S.; Enjalbert, N.; Garandet, J. P.; Heslinga, D. R.; Lemiti, M.

2010-06-01

This letter focuses on the variation of the Hall majority carrier mobility with the dopant compensation level in purely Boron-doped Czochralski grown silicon single crystals. Compensation was varied continuously at the sample scale via a step by step activation of the oxygen-based thermal donors. At room temperature, we show a strong drop in mobility for high compensation levels in both p- and n-type Si. Mobility models taking into account carrier scattering on ionized impurities and phonons could not reproduce this drop. We conclude that a specific effect of compensation must be taken into account to explain the observed behaviour. We qualitatively discuss physical mechanisms susceptible to reduce mobility in highly compensated Si.

Spatial variation in carrier dynamics along a single CdSSe nanowire

International Nuclear Information System (INIS)

Blake, Jolie C.; Eldridge, Peter S.; Gundlach, Lars

2014-01-01

Highlights: • Femtosecond Kerr-gate microscopy allows ultrafast fluorescence measurements along different positions of a single nanowire. • Amplified spontaneous emission observed at high fluences can be used to calculate recombination rates. • Observation of ASE at different locations along a single CdSSe nanowire provides the ability to extract defect densities. - Abstract: Ultrafast charge carrier dynamics along individual CdS x Se 1−x nanowires has been measured. The use of an improved ultrafast Kerr-gated microscope allows for spatially resolved luminescence measurements along a single nanowire. Amplified spontaneous emission (ASE) was observed at high excitation fluences. Position dependent variations of ultrafast ASE dynamics were observed. SEM and colorimetric measurements showed that the difference in dynamics can be attributed to variations in non-radiative recombination rates along the wire. The dominant Shockley-Read recombination rate can be extracted from ASE dynamics and can be directly related to charge carrier mobility and defect density. Employing ASE as a probe for defect densities provides a new sub-micron spatially resolved, contactless method for measurements of charge carrier mobility

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

Science.gov (United States)

Lee, H-P; Perozek, J; Rosario, L D; Bayram, C

2016-11-21

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {Al x Ga 1-x N}/AlN, (b) Thin-GaN/3 × {Al x Ga 1-x N}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm 2 /V∙s) and 2DEG carrier concentration (>1.0 × 10 13  cm -2 ) on Si(111) substrates.

Study of carrier mobility of N,N′-diphenyl-N,N′bis(1,1′-biphenyl)-4,4′-diamine (NPB) by transmission line model of impedance spectroscopy

International Nuclear Information System (INIS)

Tang, Chao; Xu, Hui; Wang, Xu-Liang; Liu, Wei; Liu, Rui-Lan; Rong, Zhou; Fan, Qu-Li; Huang, Wei

2013-01-01

As a powerful method for electrical measurement, impedance spectroscopy and admittance spectroscopy methods began to receive more and more attention in organic electronics research scholars. It demonstrates outstanding advantages especially in the measurement of the mobility of the charge carriers. In this paper, the hole mobility of N,N′-diphenyl-N,N′bis(1,1′-biphenyl)-4,4′-diamine (NPB) was studied by the transmission line model based on impedance spectroscopy. According to energy level of the materials of each layer, a hole-only current device with single-layer structure of indium-tin-oxide(ITO)/NPB/Ag was designed and fabricated, and its Nyquist diagram was measured at different biased voltage. The corresponding transmission line model was proposed according to the device structure and the materials, which was used to the fitting procedure to get the transfer time of the carrier. At last, the carrier mobility was obtained from the transfer time. The results showed that the hole mobility of NPB obtained by transmission line model was in line with the Poole–Freckle model. The zero-field mobility and the pre-exponential factor was further achieved to be 3.9 × 10 −5 cm 2 · V −1 · s −1 and 6.8 × 10 −3 (V/cm) −1/2 , respectively. Moreover, the method can also be easily used for the study of the electron transport properties of the organic semiconductor. - Highlights: • Hole mobility of N,N′-diphenyl-N,N′bis(1,1′-biphenyl)-4,4′-diamine (NPB) was studied by the transmission line model • The results was in line with the Poole-Freckle model • Zero-field mobility and the pre-exponential factor was further achieved

High-throughput bioscreening system utilizing high-performance affinity magnetic carriers exhibiting minimal non-specific protein binding

International Nuclear Information System (INIS)

Hanyu, Naohiro; Nishio, Kosuke; Hatakeyama, Mamoru; Yasuno, Hiroshi; Tanaka, Toshiyuki; Tada, Masaru; Nakagawa, Takashi; Sandhu, Adarsh; Abe, Masanori; Handa, Hiroshi

2009-01-01

For affinity purification of drug target protein we have developed magnetic carriers, narrow in size distribution (184±9 nm), which exhibit minimal non-specific binding of unwanted proteins. The carriers were highly dispersed in aqueous solutions and highly resistant to organic solvents, which enabled immobilization of various hydrophobic chemicals as probes on the carrier surfaces. Utilizing the carriers we have automated the process of separation and purification of the target proteins that had been done by manual operation previously.

Determination of energy band diagram and charge carrier mobility of white emitting polymer from optical, electrical and impedance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Mohd Sarjidan, M.A., E-mail: mohd.arif@um.edu.my; Mohd Mokhtar, H.A.; Abd Majid, W.H., E-mail: q3haliza@um.edu.my

2015-03-15

A single-layer white polymer light-emitting device (WPLED) has been fabricated using spin coating technique. The device was constructed as ITO/PEDOT:PSS(50 nm)/SPW-111(50 nm)/LiF(1 nm)/Al(100 nm). Indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) are used as the transparent anode. SPW-111 is fabricated as a white emissive layer and lithium fluoride (LiF) and aluminum (Al) are used as reflecting cathode. Energy band diagram of the device was estimated from a combination of ultraviolet–visible (UV–vis) and current–voltage (J–V) analyses. Charge carrier mobility (μ) of PLED was evaluated using negative differential susceptance (−ΔB) method from impedance spectroscopy (IS) analysis. The calculated μ of the SPW-111 device is in the magnitude of 10{sup −6} cm{sup 2}/V/s. - Highlights: • Single layer PLED has been fabricated with spin-coating technique and device performance has been evaluated. • Energy band diagram of the SPW-111 is estimated from optical and electrical analyses. • Charge carrier mobility of the SPW-111 materials is obtained by impedance spectroscopy.

Thermal instability and the growth of the InGaAs/AlGaAs pseudomorphic high electron mobility transistor system

International Nuclear Information System (INIS)

Pellegrino, Joseph G.; Qadri, Syed B.; Mahadik, Nadeemullah A.; Rao, Mulpuri V.; Tseng, Wen F.; Thurber, Robert; Gajewski, Donald; Guyer, Jonathan

2007-01-01

The effects of temperature overshoot during molecular beam epitaxy growth on the transport properties of conventionally and delta-doped pseudomorphic high electron mobility transistor (pHEMT) structures have been examined. A diffuse reflectance spectroscopy (DRS)-controlled versus a thermocouple (TC)-controlled, growth scheme is compared. Several advantages of the DRS-grown pHEMTs over the TC-controlled version were observed. Modest improvements in mobility, on the order of 2%-3%, were observed in addition to a 20% reduction in carrier freeze-out for the DRS-grown pHEMTs at 77 K

Imaging ballistic carrier trajectories in graphene using scanning gate microscopy

Energy Technology Data Exchange (ETDEWEB)

Morikawa, Sei; Masubuchi, Satoru [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Dou, Ziwei; Wang, Shu-Wei; Smith, Charles G.; Connolly, Malcolm R., E-mail: mrc61@cam.ac.uk [Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE (United Kingdom); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Machida, Tomoki, E-mail: tmachida@iis.u-tokyo.ac.jp [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

2015-12-14

We use scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and subject to a weak magnetic field. We employ a magnetic focusing geometry to image carriers that emerge ballistically from an injector, follow a cyclotron path due to the Lorentz force from an applied magnetic field, and land on an adjacent collector probe. The local electric field generated by the scanning tip in the vicinity of the carriers deflects their trajectories, modifying the proportion of carriers focused into the collector. By measuring the voltage at the collector while scanning the tip, we are able to obtain images with arcs that are consistent with the expected cyclotron motion. We also demonstrate that the tip can be used to redirect misaligned carriers back to the collector.

High mobility In{sub 2}O{sub 3}:H transparent conductive oxides prepared by atomic layer deposition and solid phase crystallization

Energy Technology Data Exchange (ETDEWEB)

Macco, B.; Wu, Y.; Vanhemel, D. [Department of Applied Physics, Eindhoven University of Technology (Netherlands); Kessels, W.M.M. [Department of Applied Physics, Eindhoven University of Technology (Netherlands); Solliance Solar Research, Eindhoven (Netherlands)

2014-12-01

The preparation of high-quality In{sub 2}O{sub 3}:H, as transparent conductive oxide (TCO), is demonstrated at low temperatures. Amorphous In{sub 2}O{sub 3}:H films were deposited by atomic layer deposition at 100 C, after which they underwent solid phase crystallization by a short anneal at 200 C. TEM analysis has shown that this approach can yield films with a lateral grain size of a few hundred nm, resulting in electron mobility values as high as 138 cm{sup 2}/V s at a device-relevant carrier density of 1.8 x 10{sup 20} cm{sup -3}. Due to the extremely high electron mobility, the crystallized films simultaneously exhibit a very low resistivity (0.27 mΩ cm) and a negligible free carrier absorption. In conjunction with the low temperature processing, this renders these films ideal candidates for front TCO layers in for example silicon heterojunction solar cells and other sensitive optoelectronic applications. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Equivalence of donor and acceptor fits of temperature dependent Hall carrier density and Hall mobility data: Case of ZnO

International Nuclear Information System (INIS)

Brochen, Stéphane; Feuillet, Guy; Pernot, Julien

2014-01-01

In this work, statistical formulations of the temperature dependence of ionized and neutral impurity concentrations in a semiconductor, needed in the charge balance equation and for carrier scattering calculations, have been developed. These formulations have been used in order to elucidate a confusing situation, appearing when compensating acceptor (donor) levels are located sufficiently close to the conduction (valence) band to be thermally ionized and thereby to emit (capture) an electron to (from) the conduction (valence) band. In this work, the temperature dependent Hall carrier density and Hall mobility data adjustments are performed in an attempt to distinguish the presence of a deep acceptor or a deep donor level, coexisting with a shallower donor level and located near the conduction band. Unfortunately, the present statistical developments, applied to an n-type hydrothermal ZnO sample, lead in both cases to consistent descriptions of experimental Hall carrier density and mobility data and thus do not allow to determine the nature, donor or acceptor, of the deep level. This demonstration shows that the emission of an electron in the conduction band, generally assigned to a (0/+1) donor transition from a donor level cannot be applied systematically and could also be attributed to a (−1/0) donor transition from an acceptor level. More generally, this result can be extended for any semiconductor and also for deep donor levels located close to the valence band (acceptor transition)

Entanglement of conjugated polymer chains influences molecular self-assembly and carrier transport

KAUST Repository

Zhao, Kui; Khan, Hadayat Ullah; Li, Ruipeng; Su, Yisong; Amassian, Aram

2013-01-01

The influence of polymer entanglement on the self-assembly, molecular packing structure, and microstructure of low-Mw (lightly entangled) and high-Mw (highly entangled) poly (3-hexylthiophene) (P3HT), and the carrier transport in thin-film transistors, are investigated. The polymer chains are gradually disentangled in a marginal solvent via ultrasonication of the polymer solution, and demonstrate improved diffusivity of precursor species (coils, aggregates, and microcrystallites), enhanced nucleation and crystallization of P3HT in solution, and self-assembly of well-ordered and highly textured fibrils at the solid-liquid interface. In low-Mw P3HT, reducing chain entanglement enhances interchain and intrachain ordering, but reduces the interconnectivity of ordered domains (tie molecules) due to the presence of short chains, thus deteriorating carrier transport even in the face of improving crystallinity. Reducing chain entanglement in high-Mw P3HT solutions increases carrier mobility up to ≈20-fold, by enhancing interchain and intrachain ordering while maintaining a sufficiently large number of tie molecules between ordered domains. These results indicate that charge carrier mobility is strongly governed by the balancing of intrachain and interchain ordering, on the one hand, and interconnectivity of ordered domains, on the other hand. In high-Mw P3HT, intrachain and interchain ordering appear to be the key bottlenecks to charge transport, whereas in low-Mw P3HT, the limited interconnectivity of the ordered domains acts as the primary bottleneck to charge transport. Conjugated polymer chains of poly(3-hexylthiophene) (P3HT) are gradually disentangled in solution and trends in carrier transport mechanisms in organic thin film transistors for low- and high-molecular weight P3HT are investigated. While intrachain and interchain ordering within ordered domains are the key bottlenecks to charge transport in high-Mw P3HT films, the limited interconnectivity of ordered

Entanglement of conjugated polymer chains influences molecular self-assembly and carrier transport

KAUST Repository

Zhao, Kui

2013-06-26

The influence of polymer entanglement on the self-assembly, molecular packing structure, and microstructure of low-Mw (lightly entangled) and high-Mw (highly entangled) poly (3-hexylthiophene) (P3HT), and the carrier transport in thin-film transistors, are investigated. The polymer chains are gradually disentangled in a marginal solvent via ultrasonication of the polymer solution, and demonstrate improved diffusivity of precursor species (coils, aggregates, and microcrystallites), enhanced nucleation and crystallization of P3HT in solution, and self-assembly of well-ordered and highly textured fibrils at the solid-liquid interface. In low-Mw P3HT, reducing chain entanglement enhances interchain and intrachain ordering, but reduces the interconnectivity of ordered domains (tie molecules) due to the presence of short chains, thus deteriorating carrier transport even in the face of improving crystallinity. Reducing chain entanglement in high-Mw P3HT solutions increases carrier mobility up to ≈20-fold, by enhancing interchain and intrachain ordering while maintaining a sufficiently large number of tie molecules between ordered domains. These results indicate that charge carrier mobility is strongly governed by the balancing of intrachain and interchain ordering, on the one hand, and interconnectivity of ordered domains, on the other hand. In high-Mw P3HT, intrachain and interchain ordering appear to be the key bottlenecks to charge transport, whereas in low-Mw P3HT, the limited interconnectivity of the ordered domains acts as the primary bottleneck to charge transport. Conjugated polymer chains of poly(3-hexylthiophene) (P3HT) are gradually disentangled in solution and trends in carrier transport mechanisms in organic thin film transistors for low- and high-molecular weight P3HT are investigated. While intrachain and interchain ordering within ordered domains are the key bottlenecks to charge transport in high-Mw P3HT films, the limited interconnectivity of ordered

Hybrid Perovskites for Photovoltaics: Charge-Carrier Recombination, Diffusion, and Radiative Efficiencies.

Science.gov (United States)

Johnston, Michael B; Herz, Laura M

2016-01-19

values extracted from OPTP measurements and their dependence on perovskite composition and morphology. The significance of the reviewed charge-carrier recombination and mobility parameters is subsequently evaluated in terms of the charge-carrier diffusion lengths and radiative efficiencies that may be obtained for such hybrid perovskites. We particularly focus on calculating such quantities in the limit of ultra-low trap-related recombination, which has not yet been demonstrated but could be reached through further advances in material processing. We find that for thin films of hybrid lead iodide perovskites with typical charge-carrier mobilities of ∼30cm(2)/(V s), charge-carrier diffusion lengths at solar (AM1.5) irradiation are unlikely to exceed ∼10 μm even if all trap-related recombination is eliminated. We further examine the radiative efficiency for hybrid lead halide perovskite films and show that if high efficiencies are to be obtained for intermediate charge-carrier densities (n ≈ 10(14) cm(-3)) trap-related recombination lifetimes will have to be enhanced well into the microsecond range.

Introducing correlations into carrier transport simulations of disordered materials through seeded nucleation: impact on density of states, carrier mobility, and carrier statistics

Science.gov (United States)

Brown, J. S.; Shaheen, S. E.

2018-04-01

Disorder in organic semiconductors has made it challenging to achieve performance gains; this is a result of the many competing and often nuanced mechanisms effecting charge transport. In this article, we attempt to illuminate one of these mechanisms in the hopes of aiding experimentalists in exceeding current performance thresholds. Using a heuristic exponential function, energetic correlation has been added to the Gaussian disorder model (GDM). The new model is grounded in the concept that energetic correlations can arise in materials without strong dipoles or dopants, but may be a result of an incomplete crystal formation process. The proposed correlation has been used to explain the exponential tail states often observed in these materials; it is also better able to capture the carrier mobility field dependence, commonly known as the Poole-Frenkel dependence, when compared to the GDM. Investigation of simulated current transients shows that the exponential tail states do not necessitate Montroll and Scher fits. Montroll and Scher fits occur in the form of two distinct power law curves that share a common constant in their exponent; they are clearly observed as linear lines when the current transient is plotted using a log-log scale. Typically, these fits have been found appropriate for describing amorphous silicon and other disordered materials which display exponential tail states. Furthermore, we observe the proposed correlation function leads to domains of energetically similar sites separated by boundaries where the site energies exhibit stochastic deviation. These boundary sites are found to be the source of the extended exponential tail states, and are responsible for high charge visitation frequency, which may be associated with the molecular turnover number and ultimately the material stability.

Charge carrier mobility in poly[methyl(phenyl)silylene] studied by time-resolved terahertz spectroscopy and molecular modeling

Czech Academy of Sciences Publication Activity Database

Němec, Hynek; Kratochvílová, Irena; Kužel, Petr; Šebera, Jakub; Kochalska, Anna; Nožár, Juraj; Nešpůrek, Stanislav

2011-01-01

Roč. 13, č. 7 (2011), s. 2850-2856 ISSN 1463-9076 R&D Projects: GA ČR(CZ) GP202/09/P099; GA ČR GA203/08/1594; GA AV ČR KAN401770651; GA MŠk LC512; GA ČR(CZ) GAP304/10/1951 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : molecular electronics * THz spectroscopy * charge carrier mobility Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.573, year: 2011

Improved DC performance of AlGaN/GaN high electron mobility transistors using hafnium oxide for surface passivation

International Nuclear Information System (INIS)

Liu, Chang; Chor, Eng Fong; Tan, Leng Seow

2007-01-01

Improved DC performance of AlGaN/GaN high electron mobility transistors (HEMTs) have been demonstrated using reactive-sputtered hafnium oxide (HfO 2 ) thin film as the surface passivation layer. Hall data indicate a significant increase in the product of sheet carrier concentration (n s ) and electron mobility (μ n ) in the HfO 2 -passivated HEMTs, compared to the unpassivated HEMTs. This improvement in electron carrier characteristics gives rise to a 22% higher I Dmax and an 18% higher g mmax in HEMTs with HfO 2 passivation relative to the unpassivated devices. On the other hand, I gleak of the HEMTs decreases by nearly one order of magnitude when HfO 2 passivation is applied. In addition, drain current is measured in the subthreshold regime. Compared to the unpassivated HEMTs, HfO 2 -passivated HEMTs exhibit a much smaller off-state I D , indicating better turn-off characteristics

Microstructure-mobility correlation in self-organised, conjugated polymer field-effect transistors

DEFF Research Database (Denmark)

Sirringhaus, H.; Brown, P.J.; Friend, R.H.

2000-01-01

We have investigated the correlation between polymer microstructure and charge carrier mobility in high-mobility, self-organised field-effect transistors of poly-3-hexyl-thiophene (P3HT). Two different preferential orientations of the microcrystalline P3HT domains with respect to the substrate have...

Recovery of synthetic dye from simulated wastewater using emulsion liquid membrane process containing tri-dodecyl amine as a mobile carrier

Energy Technology Data Exchange (ETDEWEB)

Othman, N., E-mail: norasikin@cheme.utm.my [Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Zailani, S.N.; Mili, N. [Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

2011-12-30

Highlights: Black-Right-Pointing-Pointer The emulsion liquid membrane process for synthetic reactive dyes recovery was examined. Black-Right-Pointing-Pointer Mobile carriers of tri-dodycylamine and salicyclic acid was used in formulation to remove the reactive dyes from simulated wastewater. Black-Right-Pointing-Pointer Almost 100% of dye was extracted and recovered in receiving phase. Black-Right-Pointing-Pointer An electrical field was used to breakdown the emulsion to separate the liquid membrane and receiving/recovery phase. - Abstract: The extraction of Red 3BS reactive dye from aqueous solution was studied using emulsion liquid membrane (ELM). ELM is one of the processes that have very high potential in treating industrial wastewater consisting of dyes. In this research, Red 3BS reactive dye was extracted from simulated wastewater using tridodecylamine (TDA) as the carrier agent, salicyclic acid (SA) to protonate TDA, sodium chloride as the stripping agent, kerosene as the diluent and SPAN 80 as emulsifier. Experimental parameters investigated were salicyclic acid concentration, extraction time, SPAN 80 concentration, sodium chloride concentration, TDA concentration, agitation speed, homogenizer speed, emulsifying time and treat ratio. The results show almost 100% of Red 3BS was removed and stripped in the receiving phase at the optimum condition in this ELM system. High voltage coalesce was applied to break the emulsion hence, enables recovery of Red 3BS in the receiving phase.

Understanding morphology-mobility dependence in PEDOT:Tos

Science.gov (United States)

Rolland, Nicolas; Franco-Gonzalez, Juan Felipe; Volpi, Riccardo; Linares, Mathieu; Zozoulenko, Igor V.

2018-04-01

The potential of conjugated polymers to compete with inorganic materials in the field of semiconductor is conditional on fine-tuning of the charge carriers mobility. The latter is closely related to the material morphology, and various studies have shown that the bottleneck for charge transport is the connectivity between well-ordered crystallites, with a high degree of π -π stacking, dispersed into a disordered matrix. However, at this time there is a lack of theoretical descriptions accounting for this link between morphology and mobility, hindering the development of systematic material designs. Here we propose a computational model to predict charge carriers mobility in conducting polymer PEDOT depending on the physicochemical properties of the system. We start by calculating the morphology using molecular dynamics simulations. Based on the calculated morphology we perform quantum mechanical calculation of the transfer integrals between states in polymer chains and calculate corresponding hopping rates using the Miller-Abrahams formalism. We then construct a transport resistive network, calculate the mobility using a mean-field approach, and analyze the calculated mobility in terms of transfer integrals distributions and percolation thresholds. Our results provide theoretical support for the recent study [Noriega et al., Nat. Mater. 12, 1038 (2013), 10.1038/nmat3722] explaining why the mobility in polymers rapidly increases as the chain length is increased and then saturates for sufficiently long chains. Our study also provides the answer to the long-standing question whether the enhancement of the crystallinity is the key to designing high-mobility polymers. We demonstrate, that it is the effective π -π stacking, not the long-range order that is essential for the material design for the enhanced electrical performance. This generic model can compare the mobility of a polymer thin film with different solvent contents, solvent additives, dopant species or

High school Tay-Sachs disease carrier screening: 5 to 11-year follow-up.

Science.gov (United States)

Curd, Helen; Lewis, Sharon; Macciocca, Ivan; Sahhar, Margaret; Petrou, Vicki; Bankier, Agnes; Lieberman, Sari; Levy-Lahad, Ephrat; Delatycki, Martin B

2014-04-01

The Melbourne high school Tay-Sachs disease (TSD) carrier screening program began in 1997. The aim of this study was to assess the outcomes of this screening program among those who had testing more than 5 years ago, to evaluate the long-term impact of screening. A questionnaire was used for data collection and consisted of validated scales and purposively designed questions. Questionnaires were sent to all carriers and two non-carriers for each carrier who were screened in the program between 1999 and 2005. Twenty-four out of 69 (34.8 %) carriers and 30/138 (21.7 %) non-carriers completed the questionnaire. Most participants (82 %) retained good knowledge of TSD and there was no evidence of a difference in knowledge between carriers and non-carriers. Most participants (83 %) were happy with the timing and setting of screening and thought that education and screening for TSD should be offered during high school. There was no difference between carriers and non-carriers in mean scores for the State Trait Anxiety Inventory and Decision Regret Scale. This evaluation indicated that 5-11 years post high school screening, those who were screened are supportive of the program and that negative consequences are rare.

Ab initio theory of charge-carrier conduction in ultrapure organic crystals

NARCIS (Netherlands)

Hannewald, K.; Bobbert, P.A.

2004-01-01

We present an ab initio description of charge-carrier mobilities in organic molecular crystals of high purity. Our approach is based on Holstein's original concept of small-polaron bands but generalized with respect to the inclusion of nonlocal electron-phonon coupling. By means of an explicit

Graphene mobility mapping

DEFF Research Database (Denmark)

Buron, Jonas Christian Due; Pizzocchero, Filippo; Jepsen, Peter Uhd

2015-01-01

Carrier mobility and chemical doping level are essential figures of merit for graphene, and large-scale characterization of these properties and their uniformity is a prerequisite for commercialization of graphene for electronics and electrodes. However, existing mapping techniques cannot directly...... assess these vital parameters in a non-destructive way. By deconvoluting carrier mobility and density from non-contact terahertz spectroscopic measurements of conductance in graphene samples with terahertz-transparent backgates, we are able to present maps of the spatial variation of both quantities over...... graphene indicates dominance by charged scatterers. Unexpectedly, significant variations in mobility rather than doping are the cause of large conductance inhomogeneities, highlighting the importance of statistical approaches when assessing large-area graphene transport properties....

Recombination in liquid filled ionisation chambers with multiple charge carrier species: Theoretical and numerical results

International Nuclear Information System (INIS)

Aguiar, P.; González-Castaño, D.M.; Gómez, F.; Pardo-Montero, J.

2014-01-01

Liquid-filled ionisation chambers (LICs) are used in radiotherapy for dosimetry and quality assurance. Volume recombination can be quite important in LICs for moderate dose rates, causing non-linearities in the dose rate response of these detectors, and needs to be corrected for. This effect is usually described with Greening and Boag models for continuous and pulsed radiation respectively. Such models assume that the charge is carried by two different species, positive and negative ions, each of those species with a given mobility. However, LICs operating in non-ultrapure mode can contain different types of electronegative impurities with different mobilities, thus increasing the number of different charge carriers. If this is the case, Greening and Boag models can be no longer valid and need to be reformulated. In this work we present a theoretical and numerical study of volume recombination in parallel-plate LICs with multiple charge carrier species, extending Boag and Greening models. Results from a recent publication that reported three different mobilities in an isooctane-filled LIC have been used to study the effect of extra carrier species on recombination. We have found that in pulsed beams the inclusion of extra mobilities does not affect volume recombination much, a behaviour that was expected because Boag formula for charge collection efficiency does not depend on the mobilities of the charge carriers if the Debye relationship between mobilities and recombination constant holds. This is not the case in continuous radiation, where the presence of extra charge carrier species significantly affects the amount of volume recombination. - Highlights: • Analytical extension of Greening and Boag theories to multiple charge carriers. • Detailed numerical study of process of volume recombination in LICs. • Recombination in pulsed beams is independent of number and mobilities of carriers. • Multiple charge carriers have a significant effect in continuous

Charge carrier coherence and Hall effect in organic semiconductors

Science.gov (United States)

Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

2016-01-01

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor. PMID:27025354

Charge carrier coherence and Hall effect in organic semiconductors.

Science.gov (United States)

Yi, H T; Gartstein, Y N; Podzorov, V

2016-03-30

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

Impact of Gate Dielectric in Carrier Mobility in Low Temperature Chalcogenide Thin Film Transistors for Flexible Electronics

KAUST Repository

Salas-Villasenor, A. L.; Mejia, I.; Hovarth, J.; Alshareef, Husam N.; Cha, D. K.; Ramirez-Bon, R.; Gnade, B. E.; Quevedo-Lopez, M. A.

2010-01-01

Cadmium sulfide thin film transistors were demonstrated as the n-type device for use in flexible electronics. CdS thin films were deposited by chemical bath deposition (70° C) on either 100 nm HfO2 or SiO2 as the gate dielectrics. Common gate transistors with channel lengths of 40-100 μm were fabricated with source and drain aluminum top contacts defined using a shadow mask process. No thermal annealing was performed throughout the device process. X-ray diffraction results clearly show the hexagonal crystalline phase of CdS. The electrical performance of HfO 2 /CdS -based thin film transistors shows a field effect mobility and threshold voltage of 25 cm2 V-1 s-1 and 2 V, respectively. Improvement in carrier mobility is associated with better nucleation and growth of CdS films deposited on HfO2. © 2010 The Electrochemical Society.

Impact of Gate Dielectric in Carrier Mobility in Low Temperature Chalcogenide Thin Film Transistors for Flexible Electronics

KAUST Repository

Salas-Villasenor, A. L.

2010-06-29

Cadmium sulfide thin film transistors were demonstrated as the n-type device for use in flexible electronics. CdS thin films were deposited by chemical bath deposition (70° C) on either 100 nm HfO2 or SiO2 as the gate dielectrics. Common gate transistors with channel lengths of 40-100 μm were fabricated with source and drain aluminum top contacts defined using a shadow mask process. No thermal annealing was performed throughout the device process. X-ray diffraction results clearly show the hexagonal crystalline phase of CdS. The electrical performance of HfO 2 /CdS -based thin film transistors shows a field effect mobility and threshold voltage of 25 cm2 V-1 s-1 and 2 V, respectively. Improvement in carrier mobility is associated with better nucleation and growth of CdS films deposited on HfO2. © 2010 The Electrochemical Society.

Electron drift time in silicon drift detectors: A technique for high precision measurement of electron drift mobility

International Nuclear Information System (INIS)

Castoldi, A.; Rehak, P.

1995-01-01

This paper presents a precise absolute measurement of the drift velocity and mobility of electrons in high resistivity silicon at room temperature. The electron velocity is obtained from the differential measurement of the drift time of an electron cloud in a silicon drift detector. The main features of the transport scheme of this class of detectors are: the high uniformity of the electron motion, the transport of the signal electrons entirely contained in the high-purity bulk, the low noise timing due to the very small anode capacitance (typical value 100 fF), and the possibility to measure different drift distances, up to the wafer diameter, in the same semiconductor sample. These features make the silicon drift detector an optimal device for high precision measurements of carrier drift properties. The electron drift velocity and mobility in a 10 kΩ cm NTD n-type silicon wafer have been measured as a function of the electric field in the range of possible operation of a typical drift detector (167--633 V/cm). The electron ohmic mobility is found to be 1394 cm 2 /V s. The measurement precision is better than 1%. copyright 1995 American Institute of Physics

High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi2O2Se

Science.gov (United States)

Wu, Jinxiong; Yuan, Hongtao; Meng, Mengmeng; Chen, Cheng; Sun, Yan; Chen, Zhuoyu; Dang, Wenhui; Tan, Congwei; Liu, Yujing; Yin, Jianbo; Zhou, Yubing; Huang, Shaoyun; Xu, H. Q.; Cui, Yi; Hwang, Harold Y.; Liu, Zhongfan; Chen, Yulin; Yan, Binghai; Peng, Hailin

2017-07-01

High-mobility semiconducting ultrathin films form the basis of modern electronics, and may lead to the scalable fabrication of highly performing devices. Because the ultrathin limit cannot be reached for traditional semiconductors, identifying new two-dimensional materials with both high carrier mobility and a large electronic bandgap is a pivotal goal of fundamental research. However, air-stable ultrathin semiconducting materials with superior performances remain elusive at present. Here, we report ultrathin films of non-encapsulated layered Bi2O2Se, grown by chemical vapour deposition, which demonstrate excellent air stability and high-mobility semiconducting behaviour. We observe bandgap values of ˜0.8 eV, which are strongly dependent on the film thickness due to quantum-confinement effects. An ultrahigh Hall mobility value of >20,000 cm2 V-1 s-1 is measured in as-grown Bi2O2Se nanoflakes at low temperatures. This value is comparable to what is observed in graphene grown by chemical vapour deposition and at the LaAlO3-SrTiO3 interface, making the detection of Shubnikov-de Haas quantum oscillations possible. Top-gated field-effect transistors based on Bi2O2Se crystals down to the bilayer limit exhibit high Hall mobility values (up to 450 cm2 V-1 s-1), large current on/off ratios (>106) and near-ideal subthreshold swing values (˜65 mV dec-1) at room temperature. Our results make Bi2O2Se a promising candidate for future high-speed and low-power electronic applications.

Micro-structure-mobility correlation in self-organised, conjugated polymer field-effect transistors

NARCIS (Netherlands)

Sirringhaus, H.; Brown, P.J.; Friend, R.H.; Nielsen, M.M.; Bechgaard, K.; Langeveld-Voss, B.M.W.; Spiering, A.J.H.; Janssen, R.A.J.; Meijer, E.W.

2000-01-01

We have investigated the correlation between polymer microstructure and charge carrier mobility in high-mobility, self-organised field-effect transistors of poly-3-hexyl-thiophene (P3HT). Two different preferential orientations of the microcrystalline P3HT domains with respect to the substrate have

Direct Effect of Dielectric Surface Energy on Carrier Transport in Organic Field-Effect Transistors.

Science.gov (United States)

Zhou, Shujun; Tang, Qingxin; Tian, Hongkun; Zhao, Xiaoli; Tong, Yanhong; Barlow, Stephen; Marder, Seth R; Liu, Yichun

2018-05-09

The understanding of the characteristics of gate dielectric that leads to optimized carrier transport remains controversial, and the conventional studies applied organic semiconductor thin films, which introduces the effect of dielectric on the growth of the deposited semiconductor thin films and hence only can explore the indirect effects. Here, we introduce pregrown organic single crystals to eliminate the indirect effect (semiconductor growth) in the conventional studies and to undertake an investigation of the direct effect of dielectric on carrier transport. It is shown that the matching of the polar and dispersive components of surface energy between semiconductor and dielectric is favorable for higher mobility. This new empirical finding may show the direct relationship between dielectric and carrier transport for the optimized mobility of organic field-effect transistors and hence show a promising potential for the development of next-generation high-performance organic electronic devices.

Pore-Confined Carriers and Biomolecules in Mesoporous Silica for Biomimetic Separation and Targeting

Science.gov (United States)

Zhou, Shanshan

Selectively permeable biological membranes composed of lipophilic barriers inspire the design of biomimetic carrier-mediated membranes for aqueous solute separation. This work imparts selective permeability to lipid-filled pores of silica thin film composite membranes using carrier molecules that reside in the lipophilic self-assemblies. The lipids confined inside the pores of silica are proven to be a more effective barrier than bilayers formed on the porous surface through vesicle fusion, which is critical for quantifying the function of an immobilized carrier. The ability of a lipophilic carrier embedded in the lipid bilayer to reversibly bind the target solute and transport it through the membrane is demonstrated. Through the functionalization of the silica surface with enzymes, enzymatic catalysis and biomimetic separations can be combined on this nanostructured composite platform. The successful development of biomimetic nanocomposite membrane can provide for efficient dilute aqueous solute upgrading or separations using engineered carrier/catalyst/support systems. While the carrier-mediated biomimetic membranes hold great potential, fully understanding of the transport processes in composite synthetic membranes is essential for improve the membrane performance. Electrochemical impedance spectroscopy (EIS) technique is demonstrated to be a useful tool for characterizing the thin film pore accessibility. Furthermore, the effect of lipid bilayer preparation methods on the silica thin film (in the form of pore enveloping, pore filling) on ion transport is explored, as a lipid bilayer with high electrically insulation is essential for detecting activity of proteins or biomimetic carriers in the bilayer. This study provides insights for making better barriers on mesoporous support for carrier-mediated membrane separation process. Porous silica nanoparticles (pSNPs) with pore sizes appropriate for biomolecule loading are potential for encapsulating dsRNA within the

High field-effect mobility at the (Sr,Ba)SnO{sub 3}/BaSnO{sub 3} interface

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, Kohei, E-mail: kfujiwara@imr.tohoku.ac.jp; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2016-08-15

A perovskite oxide, BaSnO{sub 3}, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO{sub 3}-based heterostructures with atomically smooth surfaces, fabricated on SrTiO{sub 3} substrates by the (Sr,Ba)SnO{sub 3} buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,Ba)SnO{sub 3} as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO{sub 3}-based field-effect transistors.

Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells

KAUST Repository

Melianas, Armantas; Etzold, Fabian; Savenije, Tom J.; Laquai, Fré dé ric; Inganä s, Olle; Kemerink, Martijn

2015-01-01

motion is boosted by this process, leading to a time-dependent carrier mobility as confirmed by direct experiments. We identify the time and distance scales relevant for carrier extraction and show that the photo-generated carriers are extracted from

High electron mobility InN

International Nuclear Information System (INIS)

Jones, R. E.; Li, S. X.; Haller, E. E.; van Genuchten, H. C. M.; Yu, K. M.; Ager, J. W. III; Liliental-Weber, Z.; Walukiewicz, W.; Lu, H.; Schaff, W. J.

2007-01-01

Irradiation of InN films with 2 MeV He + ions followed by thermal annealing below 500 deg. C creates films with high electron concentrations and mobilities, as well as strong photoluminescence. Calculations show that electron mobility in irradiated samples is limited by triply charged donor defects. Subsequent thermal annealing removes a fraction of the defects, decreasing the electron concentration. There is a large increase in electron mobility upon annealing; the mobilities approach those of the as-grown films, which have 10 to 100 times smaller electron concentrations. Spatial ordering of the triply charged defects is suggested to cause the unusual increase in electron mobility

Limitations of high dose carrier based formulations.

Science.gov (United States)

Yeung, Stewart; Traini, Daniela; Tweedie, Alan; Lewis, David; Church, Tanya; Young, Paul M

2018-06-10

This study was performed to investigate how increasing the active pharmaceutical ingredient (API) content within a formulation affects the dispersion of particles and the aerosol performance efficiency of a carrier based dry powder inhalable (DPI) formulation, using a custom dry powder inhaler (DPI) development rig. Five formulations with varying concentrations of API beclomethasone dipropionate (BDP) between 1% and 30% (w/w) were formulated as a multi-component carrier system containing coarse lactose and fine lactose with magnesium stearate. The morphology of the formulation and each component were investigated using scanning electron micrographs while the particle size was measured by laser diffraction. The aerosol performance, in terms of aerodynamic diameter, was assessed using the British pharmacopeia Apparatus E cascade impactor (Next generation impactor). Chemical analysis of the API was observed by high performance liquid chromatography (HPLC). Increasing the concentration of BDP in the blend resulted in increasing numbers and size of individual agglomerates and densely packed BDP multi-layers on the surface of the lactose carrier. BDP present within the multi-layer did not disperse as individual primary particles but as dense agglomerates, which led to a decrease in aerosol performance and increased percentage of BDP deposition within the Apparatus E induction port and pre-separator. As the BDP concentration in the blends increases, aerosol performance of the formulation decreases, in an inversely proportional manner. Concurrently, the percentage of API deposition in the induction port and pre-separator could also be linked to the amount of micronized particles (BDP and Micronized composite carrier) present in the formulation. The effect of such dose increase on the behaviour of aerosol dispersion was investigated to gain greater insight in the development and optimisation of higher dosed carrier-based formulations. Copyright © 2018 Elsevier B.V. All

Temperature-dependent field-effect carrier mobility in organic thin-film transistors with a gate SiO2 dielectric modified by H2O2 treatment

Science.gov (United States)

Lin, Yow-Jon; Hung, Cheng-Chun

2018-02-01

The effect of the modification of a gate SiO2 dielectric using an H2O2 solution on the temperature-dependent behavior of carrier transport for pentacene-based organic thin-film transistors (OTFTs) is studied. H2O2 treatment leads to the formation of Si(-OH) x (i.e., the formation of a hydroxylated layer) on the SiO2 surface that serves to reduce the SiO2 capacitance and weaken the pentacene-SiO2 interaction, thus increasing the field-effect carrier mobility ( µ) in OTFTs. The temperature-dependent behavior of carrier transport is dominated by the multiple trapping model. Note that H2O2 treatment leads to a reduction in the activation energy. The increased value of µ is also attributed to the weakening of the interactions of the charge carriers with the SiO2 dielectric that serves to reduce the activation energy.

Quantum calculations of the carrier mobility: Methodology, Matthiessen's rule, and comparison with semi-classical approaches

Energy Technology Data Exchange (ETDEWEB)

Niquet, Yann-Michel, E-mail: yniquet@cea.fr; Nguyen, Viet-Hung; Duchemin, Ivan [L-Sim, SP2M, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble (France); Triozon, François [CEA, LETI-MINATEC, Grenoble (France); Nier, Olivier; Rideau, Denis [ST Microelectronics, Crolles (France)

2014-02-07

We discuss carrier mobilities in the quantum Non-Equilibrium Green's Functions (NEGF) framework. We introduce a method for the extraction of the mobility that is free from contact resistance contamination and with minimal needs for ensemble averages. We focus on silicon thin films as an illustration, although the method can be applied to various materials such as semiconductor nanowires or carbon nanostructures. We then introduce a new paradigm for the definition of the partial mobility μ{sub M} associated with a given elastic scattering mechanism “M,” taking phonons (PH) as a reference (μ{sub M}{sup −1}=μ{sub PH+M}{sup −1}−μ{sub PH}{sup −1}). We argue that this definition makes better sense in a quantum transport framework as it is free from long range interference effects that can appear in purely ballistic calculations. As a matter of fact, these mobilities satisfy Matthiessen's rule for three mechanisms [e.g., surface roughness (SR), remote Coulomb scattering (RCS) and phonons] much better than the usual, single mechanism calculations. We also discuss the problems raised by the long range spatial correlations in the RCS disorder. Finally, we compare semi-classical Kubo-Greenwood (KG) and quantum NEGF calculations. We show that KG and NEGF are in reasonable agreement for phonon and RCS, yet not for SR. We discuss the reasons for these discrepancies.

Enhancement of carrier mobility in MoS{sub 2} field effect transistors by a SiO{sub 2} protective layer

Energy Technology Data Exchange (ETDEWEB)

Shao, Peng-Zhi; Zhao, Hai-Ming; Cao, Hui-Wen; Wang, Xue-Feng; Pang, Yu; Li, Yu-Xing; Deng, Ning-Qin; Yang, Yi; Ren, Tian-Ling, E-mail: RenTL@tsinghua.edu.cn, E-mail: zhangsh@sz.tsinghua.edu.cn [Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); Zhang, Jing [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Guang-Yu [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); CollaborativeInnovation Center of Quantum Matter, Beijing 100190 (China); Zhang, Sheng, E-mail: RenTL@tsinghua.edu.cn, E-mail: zhangsh@sz.tsinghua.edu.cn [Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); The State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Shanghai 200050 (China); Advanced Sensor and Integrated System Lab, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

2016-05-16

Molybdenum disulfide is a promising channel material for field effect transistors (FETs). In this paper, monolayer MoS{sub 2} grown by chemical vapor deposition (CVD) was used to fabricate top-gate FETs through standard optical lithography. During the fabrication process, charged impurities and interface states are introduced, and the photoresist is not removed cleanly, which both limit the carrier mobility and the source-drain current. We apply a SiO{sub 2} protective layer, which is deposited on the surface of MoS{sub 2}, in order to avoid the MoS{sub 2} directly contacting with the photoresist and the ambient environment. Therefore, the contact property between the MoS{sub 2} and the electrodes is improved, and the Coulomb scattering caused by the charged impurities and the interface states is reduced. Comparing MoS{sub 2} FETs with and without a SiO{sub 2} protective layer, the SiO{sub 2} protective layer is found to enhance the characteristics of the MoS{sub 2} FETs, including transfer and output characteristics. A high mobility of ∼42.3 cm{sup 2}/V s is achieved, which is very large among the top-gate CVD-grown monolayer MoS{sub 2} FETs.

Ambipolar carrier transport properties and molecular packing structure of octahexyl-substituted copper phthalocyanine

Science.gov (United States)

Watanabe, Ken; Watanabe, Koichi; Tohnai, Norimitsu; Itani, Hiromichi; Shimizu, Yo; Fujii, Akihiko; Ozaki, Masanori

2018-04-01

The charge carrier mobility of a solution-processable low-molecular-weight organic semiconductor material, i.e., 1,4,8,11,15,18,22,25-octahexylphthalocyanine copper complex (C6PcCu), was investigated by the time-of-flight technique. The anomalous ambipolar carrier mobility was discussed from the viewpoint of the molecular packing structure, which was clarified by single-crystal X-ray structure analysis. In the comparison between the molecular packing structures of C6PcCu and its metal-free-type homologue, it was found that the difference in carrier mobility originates from the rotation of the molecule, which is caused by the steric hindrance due to the introduction of a center metal and the interpenetration of the nonperipheral alkyl chains.

Extremely large nonsaturating magnetoresistance and ultrahigh mobility due to topological surface states in the metallic Bi2Te3 topological insulator

Science.gov (United States)

Shrestha, K.; Chou, M.; Graf, D.; Yang, H. D.; Lorenz, B.; Chu, C. W.

2017-05-01

Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large nonsaturating magnetoresistance and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-Larkin-Nagaoka formula. At high charge-carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge-carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magnetoelectric sensors and memory devices.

Ultrafast carrier thermalization in lead iodide perovskite probed with two-dimensional electronic spectroscopy.

Science.gov (United States)

Richter, Johannes M; Branchi, Federico; Valduga de Almeida Camargo, Franco; Zhao, Baodan; Friend, Richard H; Cerullo, Giulio; Deschler, Felix

2017-08-29

In band-like semiconductors, charge carriers form a thermal energy distribution rapidly after optical excitation. In hybrid perovskites, the cooling of such thermal carrier distributions occurs on timescales of about 300 fs via carrier-phonon scattering. However, the initial build-up of the thermal distribution proved difficult to resolve with pump-probe techniques due to the requirement of high resolution, both in time and pump energy. Here, we use two-dimensional electronic spectroscopy with sub-10 fs resolution to directly observe the carrier interactions that lead to a thermal carrier distribution. We find that thermalization occurs dominantly via carrier-carrier scattering under the investigated fluences and report the dependence of carrier scattering rates on excess energy and carrier density. We extract characteristic carrier thermalization times from below 10 to 85 fs. These values allow for mobilities of 500 cm 2  V -1  s -1 at carrier densities lower than 2 × 10 19  cm -3 and limit the time for carrier extraction in hot carrier solar cells.Carrier-carrier scattering rates determine the fundamental limits of carrier transport and electronic coherence. Using two-dimensional electronic spectroscopy with sub-10 fs resolution, Richter and Branchi et al. extract carrier thermalization times of 10 to 85 fs in hybrid perovskites.

Minority carrier diffusion, defects, and localization in InGaAsN, with 2% nitrogen

International Nuclear Information System (INIS)

Kurtz, Steven R.; Allerman, A. A.; Seager, C. H.; Sieg, R. M.; Jones, E. D.

2000-01-01

Electron and hole transport in compensated InGaAsN (≅2% N) are examined through Hall mobility, photoconductivity, and solar cell photoresponse measurements. Short minority carrier diffusion lengths, photoconductive-response spectra, and doping dependent, thermally activated Hall mobilities reveal a broad distribution of localized states. At this stage of development, lateral carrier transport appears to be limited by large scale (>> mean free path) material inhomogeneities, not a random alloy-induced mobility edge. (c) 2000 American Institute of Physics

Optical conductivity and optical effective mass in a high-mobility organic semiconductor: Implications for the nature of charge transport

KAUST Repository

Li, Yuan

2014-12-03

We present a multiscale modeling of the infrared optical properties of the rubrene crystal. The results are in very good agreement with the experimental data that point to nonmonotonic features in the optical conductivity spectrum and small optical effective masses. We find that, in the static-disorder approximation, the nonlocal electron-phonon interactions stemming from low-frequency lattice vibrations can decrease the optical effective masses and lead to lighter quasiparticles. On the other hand, the charge-transport and infrared optical properties of the rubrene crystal at room temperature are demonstrated to be governed by localized carriers driven by inherent thermal disorders. Our findings underline that the presence of apparently light carriers in high-mobility organic semiconductors does not necessarily imply bandlike transport.

Optical conductivity and optical effective mass in a high-mobility organic semiconductor: Implications for the nature of charge transport

KAUST Repository

Li, Yuan; Yi, Yuanping; Coropceanu, Veaceslav; Bredas, Jean-Luc

2014-01-01

We present a multiscale modeling of the infrared optical properties of the rubrene crystal. The results are in very good agreement with the experimental data that point to nonmonotonic features in the optical conductivity spectrum and small optical effective masses. We find that, in the static-disorder approximation, the nonlocal electron-phonon interactions stemming from low-frequency lattice vibrations can decrease the optical effective masses and lead to lighter quasiparticles. On the other hand, the charge-transport and infrared optical properties of the rubrene crystal at room temperature are demonstrated to be governed by localized carriers driven by inherent thermal disorders. Our findings underline that the presence of apparently light carriers in high-mobility organic semiconductors does not necessarily imply bandlike transport.

Conductance fluctuations in high mobility monolayer graphene: Nonergodicity, lack of determinism and chaotic behavior.

Science.gov (United States)

da Cunha, C R; Mineharu, M; Matsunaga, M; Matsumoto, N; Chuang, C; Ochiai, Y; Kim, G-H; Watanabe, K; Taniguchi, T; Ferry, D K; Aoki, N

2016-09-09

We have fabricated a high mobility device, composed of a monolayer graphene flake sandwiched between two sheets of hexagonal boron nitride. Conductance fluctuations as functions of a back gate voltage and magnetic field were obtained to check for ergodicity. Non-linear dynamics concepts were used to study the nature of these fluctuations. The distribution of eigenvalues was estimated from the conductance fluctuations with Gaussian kernels and it indicates that the carrier motion is chaotic at low temperatures. We argue that a two-phase dynamical fluid model best describes the transport in this system and can be used to explain the violation of the so-called ergodic hypothesis found in graphene.

High Charge Mobility of a Perylene Bisimide Dye with Hydrogen-bond Formation Group

Institute of Scientific and Technical Information of China (English)

无

2005-01-01

A perylene bisimide dye covalently bonded with a hydrogen-bond formation group of 1,3, 5-triazine-2, 4-diamine has been synthesized. Its casting films show a charge carrier mobility over 10-3 cm2/Vs, which is in the range of the highest values found for other promising charge transport materials suitable for solution processable technique.

Motion of a carrier with a mobile load along a rough inclined plane

Science.gov (United States)

Bilchenko, G. G.

2018-03-01

The mechanical system consisting of a carrier and a load is considered. The load can move respectively the carrier according to the preset given motion law. The carrier motion from rest caused the load motion is investigated. The carrier can move translationally along rectilinear trajectory along rough inclined plane. The trajectory is the line of the greatest descent. The axis of rectilinear channel along which the load moves is situated in vertical plane containing the carrier trajectory. The Coulomb model is taken to describe the friction forces on sloped plane. Differential equations of motion of carrier with load are obtained. The sufficient condition of the carrier motion without detachment from inclined plane is given. For two special cases of the channel installation angle and the plane inclination angle combination the motion types are described. The computation experiments results are presented: the carrier motions in the special cases are illustrated, the phase portraits for some types of motions are constructed.

High power terahertz induced carrier multiplication in Silicon

DEFF Research Database (Denmark)

Tarekegne, Abebe Tilahun; Pedersen, Pernille Klarskov; Iwaszczuk, Krzysztof

2015-01-01

The application of an intense THz field results a nonlinear transmission in high resistivity silicon. Upon increasing field strength, the transmission falls from 70% to 62% due to carrier generation through THz-induced impact ionization and subsequent absorption of the THz field by free electrons....

Lead Halide Perovskites as Charge Generation Layers for Electron Mobility Measurement in Organic Semiconductors.

Science.gov (United States)

Love, John A; Feuerstein, Markus; Wolff, Christian M; Facchetti, Antonio; Neher, Dieter

2017-12-06

Hybrid lead halide perovskites are introduced as charge generation layers (CGLs) for the accurate determination of electron mobilities in thin organic semiconductors. Such hybrid perovskites have become a widely studied photovoltaic material in their own right, for their high efficiencies, ease of processing from solution, strong absorption, and efficient photogeneration of charge. Time-of-flight (ToF) measurements on bilayer samples consisting of the perovskite CGL and an organic semiconductor layer of different thickness are shown to be determined by the carrier motion through the organic material, consistent with the much higher charge carrier mobility in the perovskite. Together with the efficient photon-to-electron conversion in the perovskite, this high mobility imbalance enables electron-only mobility measurement on relatively thin application-relevant organic films, which would not be possible with traditional ToF measurements. This architecture enables electron-selective mobility measurements in single components as well as bulk-heterojunction films as demonstrated in the prototypical polymer/fullerene blends. To further demonstrate the potential of this approach, electron mobilities were measured as a function of electric field and temperature in an only 127 nm thick layer of a prototypical electron-transporting perylene diimide-based polymer, and found to be consistent with an exponential trap distribution of ca. 60 meV. Our study furthermore highlights the importance of high mobility charge transporting layers when designing perovskite solar cells.

High capacity carrier ethernet transport networks

DEFF Research Database (Denmark)

Rasmussen, Anders; Zhang, Jiang; Yu, Hao

2009-01-01

OAM functions, survivability and the increased bandwidth requirements of carrier class systems. This article provides an overview of PBB-TE and T-MPLS and demonstrates how IPTV services can be realized in the framework of Carrier Ethernet. In addition we provide a case study on performing bit error...

Charge transport in organic molecular semiconductors from first principles: The bandlike hole mobility in a naphthalene crystal

Science.gov (United States)

Lee, Nien-En; Zhou, Jin-Jian; Agapito, Luis A.; Bernardi, Marco

2018-03-01

Predicting charge transport in organic molecular crystals is notoriously challenging. Carrier mobility calculations in organic semiconductors are dominated by quantum chemistry methods based on charge hopping, which are laborious and only moderately accurate. We compute from first principles the electron-phonon scattering and the phonon-limited hole mobility of naphthalene crystal in the framework of ab initio band theory. Our calculations combine GW electronic bandstructures, ab initio electron-phonon scattering, and the Boltzmann transport equation. The calculated hole mobility is in very good agreement with experiment between 100 -300 K , and we can predict its temperature dependence with high accuracy. We show that scattering between intermolecular phonons and holes regulates the mobility, though intramolecular phonons possess the strongest coupling with holes. We revisit the common belief that only rigid molecular motions affect carrier dynamics in organic molecular crystals. Our paper provides a quantitative and rigorous framework to compute charge transport in organic crystals and is a first step toward reconciling band theory and carrier hopping computational methods.

New approach for measuring the microwave Hall mobility of semiconductors

International Nuclear Information System (INIS)

Murthy, D. V. B.; Subramanian, V.; Murthy, V. R. K.

2006-01-01

Measurement of Hall mobility in semiconductor samples using bimodal cavity method gives distinct advantages due to noncontact nature as well as the provision to measure anisotropic mobility. But the measurement approaches followed till now have a disadvantage of having high error values primarily due to the problem in evaluating the calibration constant of the whole experimental arrangement. This article brings out a new approach that removes such disadvantage and presents the calibration constant with 1% accuracy. The overall error in the carrier mobility values is within 5%

77 FR 35336 - Privacy and Security of Information Stored on Mobile Communications Devices

Science.gov (United States)

2012-06-13

... made available to a carrier by the customer solely by virtue of the carrier-customer relationship,'' a... mobile wireless services providers with respect to customer information stored on their users' mobile... practices of mobile wireless service providers with respect to customer information stored on their users...

Method to quantify the delocalization of electronic states in amorphous semiconductors and its application to assessing charge carrier mobility of p -type amorphous oxide semiconductors

Science.gov (United States)

de Jamblinne de Meux, A.; Pourtois, G.; Genoe, J.; Heremans, P.

2018-01-01

Amorphous semiconductors are usually characterized by a low charge carrier mobility, essentially related to their lack of long-range order. The development of such material with higher charge carrier mobility is hence challenging. Part of the issue comes from the difficulty encountered by first-principles simulations to evaluate concepts such as the electron effective mass for disordered systems since the absence of periodicity induced by the disorder precludes the use of common concepts derived from condensed matter physics. In this paper, we propose a methodology based on first-principles simulations that partially solves this problem, by quantifying the degree of delocalization of a wave function and of the connectivity between the atomic sites within this electronic state. We validate the robustness of the proposed formalism on crystalline and molecular systems and extend the insights gained to disordered/amorphous InGaZnO4 and Si. We also explore the properties of p -type oxide semiconductor candidates recently reported to have a low effective mass in their crystalline phases [G. Hautier et al., Nat. Commun. 4, 2292 (2013), 10.1038/ncomms3292]. Although in their amorphous phase none of the candidates present a valence band with delocalization properties matching those found in the conduction band of amorphous InGaZnO4, three of the seven analyzed materials show some potential. The most promising candidate, K2Sn2O3 , is expected to possess in its amorphous phase a slightly higher hole mobility than the electron mobility in amorphous silicon.

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

Energy Technology Data Exchange (ETDEWEB)

Held, Martin; Schießl, Stefan P.; Gannott, Florentina [Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen D-91058 (Germany); Institute for Physical Chemistry, Universität Heidelberg, Heidelberg D-69120 (Germany); Miehler, Dominik [Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen D-91058 (Germany); Zaumseil, Jana, E-mail: zaumseil@uni-heidelberg.de [Institute for Physical Chemistry, Universität Heidelberg, Heidelberg D-69120 (Germany)

2015-08-24

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfO{sub x}) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states at the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100–300 nF/cm{sup 2}) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfO{sub x} dielectrics.

Opportunistic tri-band carrier aggregation in licensed spectrum for multi-operator 5G hetnet

Science.gov (United States)

Maksymuk, Taras; Kyryk, Maryan; Klymash, Mykhailo; Jo, Minho; Romaniuk, Ryszard; Kotyra, Andrzej; Zhanpeisova, Aizhan; Kozbekova, Ainur

2017-08-01

Increasing capacity of mobile networks is a real challenge due to rapid increasing of traffic demands and spectrum scarcity. Carrier aggregation technology is aimed to increase the user data rate by combining the throughput of few spectrum bands, even if they are not physically collocated. Utilization of unlicensed Wi-Fi 5 GHz band for mobile transmission opens new perspectives for carrier aggregation due to vast amount of spectrum range, which can be available for aggregation to supplement data rates for end users. There are many solutions proposed to enable mobile data transmission in unlicensed band without disturbing interference for the existing Wi-Fi users. The paper presents a new approach for opportunistic carrier aggregation in licensed and unlicensed band for multi-operator 5G network. It allows multiple network operators to utilize unlicensed spectrum opportunistically if it is not currently used by Wi-Fi or other mobile network operators. Performance of the proposed approach has been simulated in case of two competing operators. Simulation results reveal that applying the proposed method ensures achieving satisfactory performance of carrier aggregation for the case of two network operators.

Electrical Conductivity of Rocks and Dominant Charge Carriers. Part 1; Thermally Activated Positive Holes

Science.gov (United States)

Freund, Friedemann T.; Freund, Minoru M.

2012-01-01

The prevailing view in the geophysics community is that the electrical conductivity structure of the Earth's continental crust over the 5-35 km depth range can best be understood by assuming the presence of intergranular fluids and/or of intragranular carbon films. Based on single crystal studies of melt-grown MgO, magma-derived sanidine and anorthosite feldspars and upper mantle olivine, we present evidence for the presence of electronic charge carriers, which derive from peroxy defects that are introduced during cooling, under non-equilibrium conditions, through a redox conversion of pairs of solute hydroxyl arising from dissolution of H2O.The peroxy defects become thermally activated in a 2-step process, leading to the release of defect electrons in the oxygen anion sublattice. Known as positive holes and symbolized by h(dot), these electronic charge carriers are highly mobile. Chemically equivalent to O(-) in a matrix of O(2-) they are highly oxidizing. Being metastable they can exist in the matrix of minerals, which crystallized in highly reduced environments. The h(dot) are highly mobile. They appear to control the electrical conductivity of crustal rocks in much of the 5-35 km depth range.

Piezotronic effect tuned AlGaN/GaN high electron mobility transistor

Science.gov (United States)

Jiang, Chunyan; Liu, Ting; Du, Chunhua; Huang, Xin; Liu, Mengmeng; Zhao, Zhenfu; Li, Linxuan; Pu, Xiong; Zhai, Junyi; Hu, Weiguo; Wang, Zhong Lin

2017-11-01

The piezotronic effect utilizes strain-induced piezoelectric polarization charges to tune the carrier transportation across the interface/junction. We fabricated a high-performance AlGaN/GaN high electron mobility transistor (HEMT), and the transport property was proven to be enhanced by applying an external stress for the first time. The enhanced source-drain current was also observed at any gate voltage and the maximum enhancement of the saturation current was up to 21% with 15 N applied stress (0.18 GPa at center) at -1 V gate voltage. The physical mechanism of HEMT with/without external compressive stress conditions was carefully illustrated and further confirmed by a self-consistent solution of the Schrödinger-Poisson equations. This study proves the cause-and-effect relationship between the piezoelectric polarization effect and 2D electron gas formation, which provides a tunable solution to enhance the device performance. The strain tuned HEMT has potential applications in human-machine interface and the security control of the power system.

Theoretical interpretation of the electron mobility behavior in InAs nanowires

International Nuclear Information System (INIS)

Marin, E. G.; Ruiz, F. G.; Godoy, A.; Tienda-Luna, I. M.; Martínez-Blanque, C.; Gámiz, F.

2014-01-01

This work studies the electron mobility in InAs nanowires (NWs), by solving the Boltzmann Transport Equation under the Momentum Relaxation Time approximation. The numerical solver takes into account the contribution of the main scattering mechanisms present in III-V compound semiconductors. It is validated against experimental field effect-mobility results, showing a very good agreement. The mobility dependence on the nanowire diameter and carrier density is analyzed. It is found that surface roughness and polar optical phonons are the scattering mechanisms that mainly limit the mobility behavior. Finally, we explain the origin of the oscillations observed in the mobility of small NWs at high electric fields.

Theoretical interpretation of the electron mobility behavior in InAs nanowires

Energy Technology Data Exchange (ETDEWEB)

Marin, E. G., E-mail: egmarin@ugr.es; Ruiz, F. G., E-mail: franruiz@ugr.es; Godoy, A.; Tienda-Luna, I. M.; Martínez-Blanque, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada (Spain)

2014-11-07

This work studies the electron mobility in InAs nanowires (NWs), by solving the Boltzmann Transport Equation under the Momentum Relaxation Time approximation. The numerical solver takes into account the contribution of the main scattering mechanisms present in III-V compound semiconductors. It is validated against experimental field effect-mobility results, showing a very good agreement. The mobility dependence on the nanowire diameter and carrier density is analyzed. It is found that surface roughness and polar optical phonons are the scattering mechanisms that mainly limit the mobility behavior. Finally, we explain the origin of the oscillations observed in the mobility of small NWs at high electric fields.

Magnetotransport of High Mobility Holes in Monolayer and Bilayer WSe2

Science.gov (United States)

Tutuc, Emanuel

Transition metal dichalcogenides have attracted significant interest because of their two-dimensional crystal structure, large band-gap, and strong spin-orbit interaction which leads to spin-valley locking. Recent advances in sample fabrication have allowed the experimental study of low temperature magneto-transport of high mobility holes in WSe2. We review here the main results of these studies which reveal clear quantum Hall states in mono- and bilayer WSe2. The data allows the extraction of an effective hole mass of m* = 0.45me (me is the bare electron mass) in both mono and bilayer WSe2. A systematic study of the carrier distribution in bilayer WSe2 determined from a Fourier analysis of the Shubnikov-de Haas oscillations indicates that the two layers are weakly coupled. The individual layer density dependence on gate bias shows negative compressibility, a signature of strong electron-electron interaction in these materials associated with the large effective mass. We discuss the interplay between cyclotron and Zeeman splitting using the dependence of the quantum Hall state sequence on carrier density, and the angle between the magnetic field and the WSe2 plane. Work done in collaboration with B. Fallahazad, H. C. P. Movva, K. Kim, S. K. Banerjee, T. Taniguchi, and K. Watanabe. This work supported by the Nanoelectronics Research Initiative SWAN center, Intel Corp., and National Science Foundation.

Black Phosphorus Based Field Effect Transistors with Simultaneously Achieved Near Ideal Subthreshold Swing and High Hole Mobility at Room Temperature.

Science.gov (United States)

Liu, Xinke; Ang, Kah-Wee; Yu, Wenjie; He, Jiazhu; Feng, Xuewei; Liu, Qiang; Jiang, He; Dan Tang; Wen, Jiao; Lu, Youming; Liu, Wenjun; Cao, Peijiang; Han, Shun; Wu, Jing; Liu, Wenjun; Wang, Xi; Zhu, Deliang; He, Zhubing

2016-04-22

Black phosphorus (BP) has emerged as a promising two-dimensional (2D) material for next generation transistor applications due to its superior carrier transport properties. Among other issues, achieving reduced subthreshold swing and enhanced hole mobility simultaneously remains a challenge which requires careful optimization of the BP/gate oxide interface. Here, we report the realization of high performance BP transistors integrated with HfO2 high-k gate dielectric using a low temperature CMOS process. The fabricated devices were shown to demonstrate a near ideal subthreshold swing (SS) of ~69 mV/dec and a room temperature hole mobility of exceeding >400 cm(2)/Vs. These figure-of-merits are benchmarked to be the best-of-its-kind, which outperform previously reported BP transistors realized on traditional SiO2 gate dielectric. X-ray photoelectron spectroscopy (XPS) analysis further reveals the evidence of a more chemically stable BP when formed on HfO2 high-k as opposed to SiO2, which gives rise to a better interface quality that accounts for the SS and hole mobility improvement. These results unveil the potential of black phosphorus as an emerging channel material for future nanoelectronic device applications.

Carrier mobilities in irradiated silicon

CERN Document Server

Brodbeck, T J; Sloan, T; Fretwurst, E; Kuhnke, M; Lindström, G

2002-01-01

Using laser pulses with <1 ns duration and a 500 MHz digital oscilloscope the current pulses were investigated for p-i-n Si diodes irradiated by neutrons up to 1 MeV equivalent fluences of 2.4x10 sup 1 sup 4 n/cm sup 2. Fitting the current pulse duration as a function of bias voltage allowed measurement of mobility and saturation velocity for both electrons and holes. No significant changes in these parameters were observed up to the maximum fluence. There are indications of a non-uniform space charge distribution in heavily irradiated diodes.

On motions of a carrier with a mobile load along a rough inclined plane

Science.gov (United States)

Bilchenko, Grigory; Bilchenko, Grigory; Bilchenko, Nataly

2018-05-01

A mechanical system consisting of a carrier and a load is considered. The load can move respectively to the carrier according to a predetermined motion law. The carrier can move translationally along a rectilinear trajectory on a rough inclined plane. The trajectory is the line of the greatest descent. The axis of the rectilinear channel, along which the load moves, is located in a vertical plane passing through the trajectory of the carrier. The Coulomb dry friction model is applied for simulation the forces of resistance to the motion of the carrier from the side of the underlying inclined plane. The extreme value of plane inclination angle at which the carrier is at rest, when the load is stationary, is obtained by taking into account the frictional forces of sliding at rest. Differential equations of motion of a carrier with a load moving with respect to the carrier are obtained taking into account the requirement of motion of the carrier along an inclined plane without detachment. The determining relationships are given which made it possible to classify the types of carrier motion when the channel setting angle and the plane inclination angle are related by a certain inequality. The results of computational experiments are presented.

Intrinsic broadening of the mobility spectrum of bulk n-type GaAs

International Nuclear Information System (INIS)

Jolley, G; Umana-Membreno, G A; Akhavan, N D; Antoszewski, J; Faraone, L; Fischetti, M V

2014-01-01

Modern devices consisting of multiple semiconductor layers often result in the population of numerous distinct carrier species. Conventional Hall measurements at a single-magnetic-field strength provide only a weighted average of the electron mobility and carrier concentration of a semiconductor structure and, therefore, are of limited use for the extraction of carrier transport information. In recent years, mobility spectrum analysis techniques, which have been developed to extract a mobility spectrum from magnetic field-dependent conductivity-tensor measurements, have been applied in the analysis of carrier conductivity mechanisms of numerous semiconductor structures and devices. Currently there is a severe lack of reported studies on theoretical calculations of the mobility distribution of semiconductor structures or devices. In addition, the majority of reports on experimental mobility spectrum analysis are of complex, multi layered structures such as type-II superlattices, and the interpretation of the mobility spectra has been difficult. Therefore, a good understanding of the mobility spectrum has yet to be developed. For example, it is often assumed that distinct peaks of a mobility spectrum result from fundamentally different conduction mechanisms such as the bulk and surface conduction of narrow-band-gap semiconductors. In this article, we present calculations of the electron mobility distribution of bulk GaAs, which predict the existence of multiple mobility spectrum peaks that result from electron conductivity in the Γ conduction band. This report serves as an important and simple test case upon which experimentally measured mobility spectra can be compared. It also presents insight into the general nature of electron mobility distributions. (paper)

Polaron mobility obtained by a variational approach for lattice Fröhlich models

Science.gov (United States)

Kornjača, Milan; Vukmirović, Nenad

2018-04-01

Charge carrier mobility for a class of lattice models with long-range electron-phonon interaction was investigated. The approach for mobility calculation is based on a suitably chosen unitary transformation of the model Hamiltonian which transforms it into the form where the remaining interaction part can be treated as a perturbation. Relevant spectral functions were then obtained using Matsubara Green's functions technique and charge carrier mobility was evaluated using Kubo's linear response formula. Numerical results were presented for a wide range of electron-phonon interaction strengths and temperatures in the case of one-dimensional version of the model. The results indicate that the mobility decreases with increasing temperature for all electron-phonon interaction strengths in the investigated range, while longer interaction range leads to more mobile carriers.

Mobility Optimization in LaxBa1-xSnO3 Thin Films Deposited via High Pressure Oxygen Sputtering

Science.gov (United States)

Postiglione, William Michael

BaSnO3 (BSO) is one of the most promising semiconducting oxides currently being explored for use in future electronic applications. BSO possesses a unique combination of high room temperature mobility (even at very high carrier concentrations, > 1019 cm-3), wide band gap, and high temperature stability, making it a potentially useful material for myriad applications. Significant challenges remain however in optimizing the properties and processing of epitaxial BSO, a critical step towards industrial applications. In this study we investigate the viability of using high pressure oxygen sputtering to produce high mobility La-doped BSO thin films. In the first part of our investigation we synthesized, using solid state reaction, phase-pure stoichiometric polycrystalline 2% La-doped BaSnO 3 for use as a target material in our sputtering system. We verified the experimental bulk lattice constant, 4.117 A, to be in good agreement with literature values. Next, we set out to optimize the growth conditions for DC sputtering of La doped BaSnO3. We found that mobility for all our films increased monotonically with deposition temperature, suggesting the optimum temperature for deposition is > 900 °C and implicating a likely improvement in transport properties with post-growth thermal anneal. We then preformed systematic studies aimed at probing the effects of varying thickness and deposition rate to optimize the structural and electronic transport properties in unbuffered BSO films. In this report we demonstrate the ability to grow 2% La BSO thin films with an effective dopant activation of essentially 100%. Our films showed fully relaxed (bulk), out-of-plane lattice parameter values when deposited on LaAlO3, MgO, and (LaAlO3)0.3(Sr2 TaAlO6)0.7 substrates, and slightly expanded out-of-plane lattice parameters for films deposited on SrTiO3, GdScO3, and PrScO3 substrates. The surface roughness's of our films were measured via AFM, and determined to be on the nm scale or better

Investigation of the High Mobility IGZO Thin Films by Using Co-Sputtering Method

Science.gov (United States)

Hsu, Chao-Ming; Tzou, Wen-Cheng; Yang, Cheng-Fu; Liou, Yu-Jhen

2015-01-01

High transmittance ratio in visible range, low resistivity, and high mobility of IGZO thin films were prepared at room temperature for 30 min by co-sputtering of Zn2Ga2O5 (Ga2O3 + 2 ZnO, GZO) ceramic and In2O3 ceramic at the same time. The deposition power of pure In2O3 ceramic target was fixed at 100 W and the deposition power of GZO ceramic target was changed from 80 W to 140 W. We chose to investigate the deposition power of GZO ceramic target on the properties of IGZO thin films. From the SEM observations, all of the deposited IGZO thin films showed a very smooth and featureless surface. From the measurements of XRD patterns, only the amorphous structure was observed. We aimed to show that the deposition power of GZO ceramic target had large effect on the Eg values, Hall mobility, carrier concentration, and resistivity of IGZO thin films. Secondary ion mass spectrometry (SIMS) analysis in the thicknesses’ profile of IGZO thin films found that In and Ga elements were uniform distribution and Zn element were non-uniform distribution. The SIMS analysis results also showed the concentrations of Ga and Zn elements increased and the concentrations of In element was almost unchanged with increasing deposition power.

Investigation of the High Mobility IGZO Thin Films by Using Co-Sputtering Method

Directory of Open Access Journals (Sweden)

Chao-Ming Hsu

2015-05-01

Full Text Available High transmittance ratio in visible range, low resistivity, and high mobility of IGZO thin films were prepared at room temperature for 30 min by co-sputtering of Zn2Ga2O5 (Ga2O3 + 2 ZnO, GZO ceramic and In2O3 ceramic at the same time. The deposition power of pure In2O3 ceramic target was fixed at 100 W and the deposition power of GZO ceramic target was changed from 80 W to 140 W. We chose to investigate the deposition power of GZO ceramic target on the properties of IGZO thin films. From the SEM observations, all of the deposited IGZO thin films showed a very smooth and featureless surface. From the measurements of XRD patterns, only the amorphous structure was observed. We aimed to show that the deposition power of GZO ceramic target had large effect on the Eg values, Hall mobility, carrier concentration, and resistivity of IGZO thin films. Secondary ion mass spectrometry (SIMS analysis in the thicknesses’ profile of IGZO thin films found that In and Ga elements were uniform distribution and Zn element were non-uniform distribution. The SIMS analysis results also showed the concentrations of Ga and Zn elements increased and the concentrations of In element was almost unchanged with increasing deposition power.

Impact of optical phonon scattering on inversion channel mobility in 4H-SiC trenched MOSFETs

Science.gov (United States)

Kutsuki, Katsuhiro; Kawaji, Sachiko; Watanabe, Yukihiko; Onishi, Toru; Fujiwara, Hirokazu; Yamamoto, Kensaku; Yamamoto, Toshimasa

2017-04-01

Temperature characteristics of the channel mobility were investigated for 4H-SiC trenched MOSFETs in the range from 30 to 200 °C. The conventional model of channel mobility limited by carrier scattering is based on Si-MOSFETs and shows a greatly different channel mobility from the experimental value, especially at high temperatures. On the other hand, our improved mobility model taking into account optical phonon scattering yielded results in excellent agreement with experimental results. Moreover, the major factors limiting the channel mobility were found to be Coulomb scattering in a low effective field (<0.7 MV/cm) and optical phonon scattering in a high effective field.

First principles calculation of point defects and mobility degradation in bulk AlSb for radiation detection application

International Nuclear Information System (INIS)

Lordi, V; Aberg, D; Erhart, P; Wu, K J

2007-01-01

The development of high resolution, room temperature semiconductor radiation detectors requires the introduction of materials with increased carrier mobility-lifetime (μτ) product, while having a band gap in the 1.4-2.2 eV range. AlSb is a promising material for this application. However, systematic improvements in the material quality are necessary to achieve an adequate μτ product. We are using a combination of simulation and experiment to develop a fundamental understanding of the factors which affect detector material quality. First principles calculations are used to study the microscopic mechanisms of mobility degradation from point defects and to calculate the intrinsic limit of mobility from phonon scattering. We use density functional theory (DFT) to calculate the formation energies of native and impurity point defects, to determine their equilibrium concentrations as a function of temperature and charge state. Perturbation theory via the Born approximation is coupled with Boltzmann transport theory to calculate the contribution toward mobility degradation of each type of point defect, using DFT-computed carrier scattering rates. A comparison is made to measured carrier concentrations and mobilities from AlSb crystals grown in our lab. We find our predictions in good quantitative agreement with experiment, allowing optimized annealing conditions to be deduced. A major result is the determination of oxygen impurity as a severe mobility killer, despite the ability of oxygen to compensation dope AlSb and reduce the net carrier concentration. In this case, increased resistivity is not a good indicator of improved material performance, due to the concomitant sharp reduction in μτ

Control of charge carrier dynamics in disordered conjugated polymers

Energy Technology Data Exchange (ETDEWEB)

Hertel, Dirk [Physical Chemistry, University of Cologne, Luxemburgerstr. 116, 50939 Cologne, Germany, (Germany)

2011-07-01

We developed a new method to probe charge carrier mobility on ultrafast time scale. It is based on electric field induced second harmonic generation. The method is applied to prototypical amorphous conjugated polymers of the polyphenylene- and polyfluorene-type. Typically the carrier mobility in these organic polymers decreases with time in a power law fashion from about 1 cm{sup 2}Vs{sup -1} at 1 ps to its stationary value of about 10{sup -6} cm{sup 2}Vs{sup -1} in hundreds of ns. The dynamics of the mobility is discussed. It is shown, that in nanoscale devices the macroscopic mobility is not adequate to describe charge transport. We study the influence of disorder, morphology and temperature on ultrafast transport. At early times the transport is dominated by tunneling and disorder plays already an essential role. Comparison of transient photocurrents with Monte-Carlo simulation reveals that on-chain transport has to be invoked to rationalize our results. The hopping rates for intrachain transport are much larger compared with interchain transport. The results give access to essential transport properties for the development of advanced theoretical models and may help to design improved solar cells.

Cooperative Transmission in Mobile Wireless Sensor Networks with Multiple Carrier Frequency Offsets: A Double-Differential Approach

Directory of Open Access Journals (Sweden)

Kun Zhao

2014-01-01

Full Text Available As a result of the rapidly increasing mobility of sensor nodes, mobile wireless sensor networks (MWSNs would be subject to multiple carrier frequency offsets (MCFOs, which result in time-varying channels and drastically degrade the network performance. To enhance the performance of such MWSNs, we propose a relay selection (RS based double-differential (DD cooperative transmission scheme, termed RSDDCT, in which the best relay sensor node is selected to forward the source sensor node’s signals to the destination sensor node with the detect-and-forward (DetF protocol. Assuming a Rayleigh fading environment, first, exact closed-form expressions for the outage probability and average bit error rate (BER of the RSDDCT scheme are derived. Then, simple and informative asymptotic outage probability and average BER expressions at the large signal-to-noise ratio (SNR regime are presented, which reveal that the RSDDCT scheme can achieve full diversity. Furthermore, the optimum power allocation strategy in terms of minimizing the average BER is investigated, and simple analytical solutions are obtained. Simulation results demonstrate that the proposed RSDDCT scheme can achieve excellent performance over fading channels in the presence of unknown random MCFOs. It is also shown that the proposed optimum power allocation strategy offers substantial average BER performance improvement over the equal power allocation strategy.

Minority carrier diffusion length extraction in Cu2ZnSn(Se,S)4 solar cells

Science.gov (United States)

Gokmen, Tayfun; Gunawan, Oki; Mitzi, David B.

2013-09-01

We report measurement of minority carrier diffusion length (Ld) for high performance Cu2ZnSn(S,Se)4 (CZTSSe) solar cells in comparison with analogous Cu(In,Ga)(S,Se)2 (CIGSSe) devices. Our Ld extraction method involves performing systematic measurements of the internal quantum efficiency combined with separate capacitance-voltage measurement. This method also enables the measurement of the absorption coefficient of the absorber material as a function of wavelength in a finished device. The extracted values of Ld for CZTSSe samples are at least factor of 2 smaller than those for CIGSSe samples. Combined with minority carrier lifetime (τ) data measured by time-resolved photoluminescence, we deduce the minority carrier mobility (μe), which is also relatively low for the CZTSSe samples.

Does the low hole transport mass in and Si nanowires lead to mobility enhancements at high field and stress: A self-consistent tight-binding study

Science.gov (United States)

Kotlyar, R.; Linton, T. D.; Rios, R.; Giles, M. D.; Cea, S. M.; Kuhn, K. J.; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard

2012-06-01

The hole surface roughness and phonon limited mobility in the silicon , , and square nanowires under the technologically important conditions of applied gate bias and stress are studied with the self-consistent Poisson-sp3d5s*-SO tight-binding bandstructure method. Under an applied gate field, the hole carriers in a wire undergo a volume to surface inversion transition diminishing the positive effects of the high and valence band nonparabolicities, which are known to lead to the large gains of the phonon limited mobility at a zero field in narrow wires. Nonetheless, the hole mobility in the unstressed wires down to the 5 nm size remains competitive or shows an enhancement at high gate field over the large wire limit. Down to the studied 3 nm sizes, the hole mobility is degraded by strong surface roughness scattering in and wires. The channels are shown to experience less surface scattering degradation. The physics of the surface roughness scattering dependence on wafer and channel orientations in a wire is discussed. The calculated uniaxial compressive channel stress gains of the hole mobility are found to reduce in the narrow wires and at the high field. This exacerbates the stressed mobility degradation with size. Nonetheless, stress gains of a factor of 2 are obtained for wires down to 3 nm size at a 5×1012 cm-2 hole inversion density per gate area.

3,4-Disubstituted Polyalkylthiophenes for High-Performance Thin-Film Transistors and Photovoltaics

KAUST Repository

Ko, Sangwon

2011-10-26

We demonstrate that poly(3,4-dialkylterthiophenes) (P34ATs) have comparable transistor mobilities (0.17 cm2 V-1 s-1) and greater environmental stability (less degradation of on/off ratio) than regioregular poly(3-alkylthiophenes) (P3ATs). Unlike poly(3-hexylthiophene) (P3HT), P34ATs do not show a strong and distinct π-π stacking in X-ray diffraction. This suggests that a strong π-π stacking is not always necessary for high charge-carrier mobility and that other potential polymer packing motifs in addition to the edge-on structure (π-π stacking direction parallel to the substrate) can lead to a high carrier mobility. The high charge-carrier mobilities of the hexyl and octyl-substituted P34AT produce power conversion efficiencies of 4.2% in polymer:fullerene bulk heterojunction photovoltaic devices. An enhanced open-circuit voltage (0.716-0.771 eV) in P34AT solar cells relative to P3HT due to increased ionization potentials was observed. © 2011 American Chemical Society.

3,4-Disubstituted Polyalkylthiophenes for High-Performance Thin-Film Transistors and Photovoltaics

KAUST Repository

Ko, Sangwon; Verploegen, Eric; Hong, Sanghyun; Mondal, Rajib; Hoke, Eric T.; Toney, Michael F.; McGehee, Michael D.; Bao, Zhenan

2011-01-01

We demonstrate that poly(3,4-dialkylterthiophenes) (P34ATs) have comparable transistor mobilities (0.17 cm2 V-1 s-1) and greater environmental stability (less degradation of on/off ratio) than regioregular poly(3-alkylthiophenes) (P3ATs). Unlike poly(3-hexylthiophene) (P3HT), P34ATs do not show a strong and distinct π-π stacking in X-ray diffraction. This suggests that a strong π-π stacking is not always necessary for high charge-carrier mobility and that other potential polymer packing motifs in addition to the edge-on structure (π-π stacking direction parallel to the substrate) can lead to a high carrier mobility. The high charge-carrier mobilities of the hexyl and octyl-substituted P34AT produce power conversion efficiencies of 4.2% in polymer:fullerene bulk heterojunction photovoltaic devices. An enhanced open-circuit voltage (0.716-0.771 eV) in P34AT solar cells relative to P3HT due to increased ionization potentials was observed. © 2011 American Chemical Society.

Prediction of a mobile two-dimensional electron gas at the LaSc O3 /BaSn O3 (001) interface

Science.gov (United States)

Paudel, Tula R.; Tsymbal, Evgeny Y.

2017-12-01

Two-dimensional electron gases (2DEG) at oxide interfaces, such as LaAl O3 /SrTi O3 (001), have aroused significant interest due to their high carrier density (˜1014c m-2 ) and strong lateral confinement (˜1 nm). However, these 2DEGs are normally hosted by the weakly dispersive and degenerate d bands (e.g., Ti -3 d bands), which are strongly coupled to the lattice, causing mobility of such 2DEGs to be relatively low at room temperature (˜1 c m2/Vs ). Here, we propose using oxide host materials with the conduction bands formed from s electrons to increase carrier mobility and soften its temperature dependence. Using first-principles density functional theory calculations, we investigate LaSc O3 /BaSn O3 (001) heterostructure and as a model system, where the conduction band hosts the s -like carriers. We find that the polar discontinuity at this interface leads to electronic reconstruction resulting in the formation of the 2DEG at this interface. The conduction electrons reside in the highly dispersive Sn -5 s bands, which have a large band width and a low effective mass. The predicted 2DEG is expected to be highly mobile even at room temperature due to the reduced electron-phonon scattering via the inter-band scattering channel. A qualitatively similar behavior is predicted for a doped BaSn O3 , where a monolayer of BaO is replaced with LaO. We anticipate that the quantum phenomena associated with these 2DEGs to be more pronounced owing to the high mobility of the carriers.

Driving Sustainable Competitive Advantage in the Mobile Industry: Evidence from U.S. Wireless Carriers

Directory of Open Access Journals (Sweden)

Changhee Kim

2016-07-01

Full Text Available In light of the growing importance of data network quality in the wireless industry, this study analyzes and compares efficiencies in management, service quality, network quality, and market in the 4G Long Term Evolution (LTE wireless industry. For this purpose, a bootstrap data envelopment analysis (DEA model using representative U.S. wireless carriers as decision making units (DMUs was designed and conducted, with further verification through the Mann-Whitney U and Wilcoxon W test, to examine the differences in efficiency distribution. The results indicate that, in terms of efficiency distribution, network quality efficiency and market efficiency belongs to the same group as that which has high management efficiency. Based on these results, this paper suggests implications and strategic guidelines for wireless carriers for improvement in management efficiency.

Turbostratic stacked CVD graphene for high-performance devices

Science.gov (United States)

Uemura, Kohei; Ikuta, Takashi; Maehashi, Kenzo

2018-03-01

We have fabricated turbostratic stacked graphene with high-transport properties by the repeated transfer of CVD monolayer graphene. The turbostratic stacked CVD graphene exhibited higher carrier mobility and conductivity than CVD monolayer graphene. The electron mobility for the three-layer turbostratic stacked CVD graphene surpassed 10,000 cm2 V-1 s-1 at room temperature, which is five times greater than that for CVD monolayer graphene. The results indicate that the high performance is derived from maintenance of the linear band dispersion, suppression of the carrier scattering, and parallel conduction. Therefore, turbostratic stacked CVD graphene is a superior material for high-performance devices.

Determination of charge carrier mobility of hole transporting polytriarylamine-based diodes

International Nuclear Information System (INIS)

Barea, Eva M.; Garcia-Belmonte, Germa; Sommer, Michael; Huettner, Sven; Bolink, Henk J.; Thelakkat, Mukundan

2010-01-01

Hole transport properties of three different side chain poly(triarylamines) have been determined by means of the analysis of steady-state current-voltage characteristics using co-planar diode structures. The interpretation is based on space-charge limited models with field-dependent mobility. Mobilities between ∼ 10 -8 and 10 -6 cm 2 V -1 s -1 are obtained. The highest mobility is achieved for poly(tetraphenylbenzidine) devices and the lowest for poly(triphenylamine) devices. Electron-rich methoxy substituents increase the mobility of poly(triphenylamine)s. A comparison of the mobility values with those obtained using organic field-effect transistors is also given.

High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

KAUST Repository

Nazir, Safdar

2012-05-18

A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

KAUST Repository

Nazir, Safdar; Schwingenschlö gl, Udo; Upadhyay Kahaly, M.

2012-01-01

A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

Structural vs. intrinsic carriers: contrasting effects of cation chemistry and disorder on ionic conductivity in pyrochlores

International Nuclear Information System (INIS)

Perriot, Romain; Uberuaga, Blas P.

2015-01-01

We use molecular dynamics simulations to investigate the role of cation disorder on oxygen diffusion in Gd 2 Zr 2 O 7 (GZO) and Gd 2 Ti 2 O 7 (GTO) pyrochlores, a class of complex oxides which contain a structural vacancy relative to the basic fluorite structure. The introduction of disorder has distinct effects depending on the chemistry of the material, increasing the mobility of structural carriers by up to four orders of magnitude in GZO. In contrast, in GTO, there is no mobility at zero or low disorder on the ns timescale, but higher disorder liberates the otherwise immobile carriers, allowing diffusion with rates comparable to GZO for the fully disordered material. Here, we show that the cation disorder enhances the diffusivity by both increasing the concentration of mobile structural carriers and their individual mobility. The disorder also influences the diffusion in materials containing intrinsic carriers, such as additional vacancies VO or oxygen interstitials OI. And while in ordered GZO and GTO the contribution of the intrinsic carriers dominates the overall diffusion of oxygen, OI in GZO contributes along with structural carriers, and the total diffusion rate can be calculated by assuming simple additive contributions from the two sources. Although the disorder in the materials with intrinsic defects usually enhances the diffusivity as in the defect-free case, in low concentrations, cation antisites AB or BA, where A = Gd and B = Zr or Ti, can act as traps for fast intrinsic defects. The trapping results in a lowering of the diffusivity, and causes a non-monotonic behavior of the diffusivity with disorder. Conversely, in the case of slow intrinsic defects, the main effect of the disorder is to liberate the structural carriers, resulting in an increase of the diffusivity regardless of the defect trapping.

Visualizing Carrier Transport in Metal Halide Perovskite Nanoplates via Electric Field Modulated Photoluminescence Imaging.

Science.gov (United States)

Hu, Xuelu; Wang, Xiao; Fan, Peng; Li, Yunyun; Zhang, Xuehong; Liu, Qingbo; Zheng, Weihao; Xu, Gengzhao; Wang, Xiaoxia; Zhu, Xiaoli; Pan, Anlian

2018-05-09

Metal halide perovskite nanostructures have recently been the focus of intense research due to their exceptional optoelectronic properties and potential applications in integrated photonics devices. Charge transport in perovskite nanostructure is a crucial process that defines efficiency of optoelectronic devices but still requires a deep understanding. Herein, we report the study of the charge transport, particularly the drift of minority carrier in both all-inorganic CsPbBr 3 and organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoplates by electric field modulated photoluminescence (PL) imaging. Bias voltage dependent elongated PL emission patterns were observed due to the carrier drift at external electric fields. By fitting the drift length as a function of electric field, we obtained the carrier mobility of about 28 cm 2 V -1 S -1 in the CsPbBr 3 perovskite nanoplate. The result is consistent with the spatially resolved PL dynamics measurement, confirming the feasibility of the method. Furthermore, the electric field modulated PL imaging is successfully applied to the study of temperature-dependent carrier mobility in CsPbBr 3 nanoplates. This work not only offers insights for the mobile carrier in metal halide perovskite nanostructures, which is essential for optimizing device design and performance prediction, but also provides a novel and simple method to investigate charge transport in many other optoelectronic materials.

Determination of charge carrier mobility of hole transporting polytriarylamine-based diodes

Energy Technology Data Exchange (ETDEWEB)

Barea, Eva M. [Photovoltaic and Optoelectronic Devices Group, Departament de Fisica, Universitat Jaume I, 12071 Castello (Spain); Garcia-Belmonte, Germa, E-mail: garciag@uji.e [Photovoltaic and Optoelectronic Devices Group, Departament de Fisica, Universitat Jaume I, 12071 Castello (Spain); Sommer, Michael; Huettner, Sven [Applied Functional Polymers, Universitaet Bayreuth, 95440 Bayreuth (Germany); Bolink, Henk J. [Molecular Science Institute-Universitat de Valencia, Poligon La Coma s/n, 46980 Paterna, Valencia (Spain); Thelakkat, Mukundan, E-mail: mukundan.thelakkat@uni-bayreuth.d [Applied Functional Polymers, Universitaet Bayreuth, 95440 Bayreuth (Germany)

2010-04-02

Hole transport properties of three different side chain poly(triarylamines) have been determined by means of the analysis of steady-state current-voltage characteristics using co-planar diode structures. The interpretation is based on space-charge limited models with field-dependent mobility. Mobilities between {approx} 10{sup -8} and 10{sup -6} cm{sup 2} V{sup -1} s{sup -1} are obtained. The highest mobility is achieved for poly(tetraphenylbenzidine) devices and the lowest for poly(triphenylamine) devices. Electron-rich methoxy substituents increase the mobility of poly(triphenylamine)s. A comparison of the mobility values with those obtained using organic field-effect transistors is also given.

Terahertz wafer-scale mobility mapping of graphene on insulating substrates without a gate

DEFF Research Database (Denmark)

Buron, Jonas Due; Mackenzie, David M. A.; Petersen, Dirch Hjorth

2015-01-01

We demonstrate wafer-scale, non-contact mapping of essential carrier transport parameters, carrier mobility (mu(drift)), carrier density (N-S), DC sheet conductance (sigma(dc)), and carrier scattering time (tau(SC)) in CVD graphene, using spatially resolved terahertz time-domain conductance...

High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

Science.gov (United States)

Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; Scarpulla, Michael A.

2018-05-01

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 1016 and 1020 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 1017 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 1017/cm3 range is observed for samples quenched at 200-300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 1016 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 1018 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Charge carrier transport and collection enhancement of copper indium diselenide photoactive nanoparticle-ink by laser crystallization

Energy Technology Data Exchange (ETDEWEB)

Nian, Qiong; Cheng, Gary J., E-mail: gjcheng@purdue.edu [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); School of Industrial Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Zhang, Martin Y. [School of Industrial Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Wang, Yuefeng [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Das, Suprem R.; Bhat, Venkataprasad S. [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); Huang, Fuqiang [Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China)

2014-09-15

There has been increasing needs for cost-effective and high performance thin film deposition techniques for photovoltaics. Among all deposition techniques, roll-to-roll printing of nanomaterials has been a promising method. However, the printed thin film contains many internal imperfections, which reduce the charge-collection performance. Here, direct pulse laser crystallization (DPLC) of photoactive nanoparticles-inks is studied to meet this challenge. In this study, copper indium selenite (CIS) nanoparticle-inks is applied as an example. Enhanced crystallinity, densified structure in the thin film is resulted after DLPC under optimal conditions. It is found that the decreased film internal imperfections after DPLC results in reducing scattering and multi-trapping effects. Both of them contribute to better charge-collection performance of CIS absorber material by increasing extended state mobility and carrier lifetime, when carrier transport and kinetics are coupled. Charge carrier transport was characterized after DPLC, showing mobility increased by 2 orders of magnitude. Photocurrent under AM1.5 illumination was measured and shown 10 times enhancement of integrated power density after DPLC, which may lead to higher efficiency in photo-electric energy conversion.

Tunable Mobility in Double-Gated MoTe2 Field-Effect Transistor: Effect of Coulomb Screening and Trap Sites.

Science.gov (United States)

Ji, Hyunjin; Joo, Min-Kyu; Yi, Hojoon; Choi, Homin; Gul, Hamza Zad; Ghimire, Mohan Kumar; Lim, Seong Chu

2017-08-30

There is a general consensus that the carrier mobility in a field-effect transistor (FET) made of semiconducting transition-metal dichalcogenides (s-TMDs) is severely degraded by the trapping/detrapping and Coulomb scattering of carriers by ionic charges in the gate oxides. Using a double-gated (DG) MoTe 2 FET, we modulated and enhanced the carrier mobility by adjusting the top- and bottom-gate biases. The relevant mechanism for mobility tuning in this device was explored using static DC and low-frequency (LF) noise characterizations. In the investigations, LF-noise analysis revealed that for a strong back-gate bias the Coulomb scattering of carriers by ionized traps in the gate dielectrics is strongly screened by accumulation charges. This significantly reduces the electrostatic scattering of channel carriers by the interface trap sites, resulting in increased mobility. The reduction of the number of effective trap sites also depends on the gate bias, implying that owing to the gate bias, the carriers are shifted inside the channel. Thus, the number of active trap sites decreases as the carriers are repelled from the interface by the gate bias. The gate-controlled Coulomb-scattering parameter and the trap-site density provide new handles for improving the carrier mobility in TMDs, in a fundamentally different way from dielectric screening observed in previous studies.

High Stability Pentacene Transistors Using Polymeric Dielectric Surface Modifier.

Science.gov (United States)

Wang, Xiaohong; Lin, Guangqing; Li, Peng; Lv, Guoqiang; Qiu, Longzhen; Ding, Yunsheng

2015-08-01

1,6-bis(trichlorosilyl)hexane (C6Cl), polystyrene (PS), and cross-linked polystyrene (CPS) were investigated as gate dielectric modified layers for high performance organic transistors. The influence of the surface energy, roughness and morphology on the charge transport of the organic thin-film transistors (OTFTs) was investigated. The surface energy and roughness both affect the grain size of the pentacene films which will control the charge carrier mobility of the devices. Pentacene thin-film transistors fabricated on the CPS modified dielectric layers exhibited charge carrier mobility as high as 1.11 cm2 V-1 s-1. The bias stress stability for the CPS devices shows that the drain current only decays 1% after 1530 s and the mobility never decreases until 13530 s.

The influence of electron irradiation at the various temperatures and annealing on carriers mobility at the low temperatures in neutron transmutation doped gallium arsenide

International Nuclear Information System (INIS)

Korshunov, F.P.; Kurilovich, N.F.; Prokhorenko, T.A.; Troshchinskii, V.T.; Shesholko, V.K.

1999-01-01

The influence of electron irradiation at the various temperatures and annealing on measured at T=100 K carriers mobility in neutron transmutation doped GaAs have been investigated. It was detected that rate of mobility decreasing with irradiation dose increasing decreases when irradiation temperature increases. It was shown that at the same time it take place the radiation defects creating and their particular or full annealing (in the dependence on irradiation temperature). Radiation stimulated annealing (annealing that take place during irradiation at the elevated temperatures) is more effective than the annealing at the same temperatures that take place after crystals are irradiated at room temperature. It means that any defects annealing during irradiation at elevated temperatures take place at more low temperatures than that during annealing after irradiation at room temperature

Multiple carrier transport in N-face indium nitride

International Nuclear Information System (INIS)

Koblmueller, Gregor; Gallinat, Chad S.; Speck, James S.; Umana-Membreno, Gilberto A.; Nener, Brett D.; Parish, Giacinta; Fehlberg, Tamara B.

2008-01-01

We present temperature (20-300 K) dependent multi-carrier measurements of electron species in N-face indium nitride. N-face InN samples were grown to different thicknesses (500-2000 nm) via plasma-assisted molecular beam epitaxy on C-face SiC substrates. Surface and bulk electron transport properties were extracted using a quantitative mobility spectrum analysis. Mobility of both bulk and surface electron species increase with film thickness. The temperature dependence of the mobility of both species differs to that of In-polar samples studied previously, while the mobility of surface electrons is more than twice that of In-polar samples with only a slight corresponding reduction in sheet concentration. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Mobility Engineering in Vertical Field Effect Transistors Based on Van der Waals Heterostructures.

Science.gov (United States)

Shin, Yong Seon; Lee, Kiyoung; Kim, Young Rae; Lee, Hyangsook; Lee, I Min; Kang, Won Tae; Lee, Boo Heung; Kim, Kunnyun; Heo, Jinseong; Park, Seongjun; Lee, Young Hee; Yu, Woo Jong

2018-03-01

Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field-effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered. The traps in WSe 2 are the main source of scattering, which influences the vertical mobility and three distinct transport mechanisms: Ohmic transport, trap-limited transport, and space-charge-limited transport. The vertical mobility in VFET can be improved by suppressing the trap states by raising the Fermi level of WSe 2 . This is achieved by increasing the injected carrier density by applying a high drain voltage, or decreasing the Schottky barrier at the graphene/WSe 2 and metal/WSe 2 junctions by applying a gate bias and reducing the metal work function, respectively. Consequently, the mobility in Mn vdWH at +50 V gate voltage is about 76 times higher than the initial mobility of Au vdWH. This work enables further improvements in the VFET for successful application in integrated circuits. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy

Science.gov (United States)

Ponseca, C. S., Jr.; Sundström, V.

2016-03-01

Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

Seasonal storage and alternative carriers: A flexible hydrogen supply chain model

International Nuclear Information System (INIS)

Reuß, M.; Grube, T.; Robinius, M.; Preuster, P.; Wasserscheid, P.; Stolten, D.

2017-01-01

Highlights: •Techno-economic model of future hydrogen supply chains. •Implementation of liquid organic hydrogen carriers into a hydrogen mobility analysis. •Consideration of large-scale seasonal storage for fluctuating renewable hydrogen production. •Implementation of different technologies for hydrogen storage and transportation. -- Abstract: A viable hydrogen infrastructure is one of the main challenges for fuel cells in mobile applications. Several studies have investigated the most cost-efficient hydrogen supply chain structure, with a focus on hydrogen transportation. However, supply chain models based on hydrogen produced by electrolysis require additional seasonal hydrogen storage capacity to close the gap between fluctuation in renewable generation from surplus electricity and fuelling station demand. To address this issue, we developed a model that draws on and extends approaches in the literature with respect to long-term storage. Thus, we analyse Liquid Organic Hydrogen Carriers (LOHC) and show their potential impact on future hydrogen mobility. We demonstrate that LOHC-based pathways are highly promising especially for smaller-scale hydrogen demand and if storage in salt caverns remains uncompetitive, but emit more greenhouse gases (GHG) than other gaseous or hydrogen ones. Liquid hydrogen as a seasonal storage medium offers no advantage compared to LOHC or cavern storage since lower electricity prices for flexible operation cannot balance the investment costs of liquefaction plants. A well-to-wheel analysis indicates that all investigated pathways have less than 30% GHG-emissions compared to conventional fossil fuel pathways within a European framework.

Carrier heating in disordered conjugated polymers in electric field

Energy Technology Data Exchange (ETDEWEB)

Vukmirovic, Nenad; Wang, Lin-Wang

2010-01-26

The electric field dependence of charge carrier transport and the effect of carrier heating in disordered conjugated polymers were investigated. A parameter-free multiscale methodology consisting of classical molecular dynamics simulation for the generation of the atomic structure, large system electronic structure and electron-phonon coupling constants calculations and the procedure for extracting the bulk polymer mobility, was used. The results suggested that the mobility of a fully disordered poly(3-hexylthiophene) (P3HT) polymer increases with electric field which is consistent with the experimental results on samples of regiorandom P3HT and different from the results on more ordered regioregular P3HT polymers, where the opposite trend is often observed at low electric fields. We calculated the electric field dependence of the effective carrier temperature and showed however that the effective temperature cannot be used to replace the joint effect of temperature and electric field, in contrast to previous theoretical results from phenomenological models. Such a difference was traced to originate from the use of simplified Miller-Abrahams hopping rates in phenomenological models in contrast to our considerations that explicitly take into account the electronic state wave functions and the interaction with all phonon modes.

Charge Carrier Transport and Photogeneration in P3HT:PCBM Photovoltaic Blends

KAUST Repository

Laquai, Frederic

2015-05-03

This article reviews the charge transport and photogeneration in bulk-heterojunction solar cells made from blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and methano­fullerene (PCBM). The charge transport, specifically the hole mobility in the RR-P3HT phase of the polymer:fullerene photovoltaic blend, is dramatically affected by thermal annealing. The hole mobility increases more than three orders of magnitude and reaches a value of up to 2 × 10−4 cm2 V−1 s−1 after the thermal annealing process as a result of an improved semi-crystallinity of the film. This significant increase of the hole mobility balances the electron and hole mobilities in a photovoltaic blend in turn reducing space-charge formation, and this is the most important factor for the strong enhancement of the photovoltaic efficiency compared to an as cast, that is, non-annealed device. In fact, the balanced charge carrier mobility in RR-P3HT:PCBM blends in combination with a field- and temperature-independent charge carrier generation and greatly reduced non-geminate recombination explains the large quantum efficiencies mea­sured in P3HT:PCBM photovoltaic devices.

Femtosecond pump-probe studies of phonons and carriers in bismuth under high pressure

International Nuclear Information System (INIS)

Kasami, M.; Ogino, T.; Mishina, T.; Yamamoto, S.; Nakahara, J.

2006-01-01

We investigate the high-pressure phase of Bi under hydrostatic pressure using pump-probe spectroscopy at pressures up to 3.0 GPa, and we observe coherent phonons signal and relaxation signal of photo-excited carriers at Bi(II) and Bi(III) phases. The pressure dependence of the coherent phonons shows that the amplitude of coherent phonons is extremely small and the frequency of coherent phonons changes at high-pressure phases. As results from our experiment, we obtain its frequencies are 2.5 and 2.2 THz at Bi(II) and Bi(III), respectively. Furthermore, photo-excited carrier relaxation indicates drastic changes near 2.5 GPa. Bismuth transforms from semimetal to semiconductor near 2.5 GPa, and band-overlapping between at L-point and at T-point disappears. We consider that the drastic changes of the photo-excited carrier relaxation are strongly correlated with the band-overlapping disappearing

Intrinsic mobility limit for anisotropic electron transport in Alq3.

Science.gov (United States)

Drew, A J; Pratt, F L; Hoppler, J; Schulz, L; Malik-Kumar, V; Morley, N A; Desai, P; Shakya, P; Kreouzis, T; Gillin, W P; Kim, K W; Dubroka, A; Scheuermann, R

2008-03-21

Muon spin relaxation has been used to probe the charge carrier motion in the molecular conductor Alq3 (tris[8-hydroxy-quinoline] aluminum). At 290 K, the magnetic field dependence of the muon spin relaxation corresponds to that expected for highly anisotropic intermolecular electron hopping. Intermolecular mobility in the fast hopping direction has been found to be 0.23+/-0.03 cm2 V-1 s(-1) in the absence of an electric- field gradient, increasing to 0.32+/-0.06 cm2 V-1 s(-1) in an electric field gradient of 1 MV m(-1). These intrinsic mobility values provide an estimate of the upper limit for mobility achievable in bulk material.

High Dynamic Optimized Carrier Loop Improvement for Tracking Doppler Rates

Directory of Open Access Journals (Sweden)

Amirhossein Fereidountabar

2015-01-01

Full Text Available Mathematical analysis and optimization of a carrier tracking loop are presented. Due to fast changing of the carrier frequency in some satellite systems, such as Low Earth Orbit (LEO or Global Positioning System (GPS, or some planes like Unmanned Aerial Vehicles (UAVs, high dynamic tracking loops play a very important role. In this paper an optimized tracking loop consisting of a third-order Phase Locked Loop (PLL assisted by a second-order Frequency Locked Loop (FLL for UAVs is proposed and discussed. Based on this structure an optimal loop has been designed. The main advantages of this approach are the reduction of the computation complexity and smaller phase error. The paper shows the simulation results, comparing them with a previous work.

Atomistic simulation on charge mobility of amorphous tris(8-hydroxyquinoline) aluminum (Alq3): origin of Poole-Frenkel-type behavior.

Science.gov (United States)

Nagata, Yuki; Lennartz, Christian

2008-07-21

The atomistic simulation of charge transfer process for an amorphous Alq(3) system is reported. By employing electrostatic potential charges, we calculate site energies and find that the standard deviation of site energy distribution is about twice as large as predicted in previous research. The charge mobility is calculated via the Miller-Abrahams formalism and the master equation approach. We find that the wide site energy distribution governs Poole-Frenkel-type behavior of charge mobility against electric field, while the spatially correlated site energy is not a dominant mechanism of Poole-Frenkel behavior in the range from 2x10(5) to 1.4x10(6) V/cm. Also we reveal that randomly meshed connectivities are, in principle, required to account for the Poole-Frenkel mechanism. Charge carriers find a zigzag pathway at low electric field, while they find a straight pathway along electric field when a high electric field is applied. In the space-charge-limited current scheme, the charge-carrier density increases with electric field strength so that the nonlinear behavior of charge mobility is enhanced through the strong charge-carrier density dependence of charge mobility.

High p-Type Doping, Mobility, and Photocarrier Lifetime in Arsenic-Doped CdTe Single Crystals

Energy Technology Data Exchange (ETDEWEB)

Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagaoka, Akira [Kyoto University; University of Utah; McCoy, Jedidiah [Washington State University; Scarpulla, Michael A. [University of Utah

2018-05-08

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10^16 and 10^20 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10^17 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 10^17/cm3 range is observed for samples quenched at 200-300 degrees C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10^16 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10^18 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Solid phase epitaxial growth of high mobility La:BaSnO_3 thin films co-doped with interstitial hydrogen

International Nuclear Information System (INIS)

Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Moram, Michelle A.; Ide, Keisuke; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

2016-01-01

This work presents the solid phase epitaxial growth of high mobility La:BaSnO_3 thin films on SrTiO_3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO_3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm"2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO_3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO_3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO_3 thin films were increased to 3 × 10"1"9" cm"−"3 and in La:BaSnO_3 thin films from 6 × 10"1"9" cm"−"3 to 1.5 × 10"2"0" cm"−"3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO_3 electron effective mass of 0.27 ± 0.05 m_0 and an optical mobility of 26 ± 7 cm"2/Vs. As compared to La:BaSnO_3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO_3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

Effect of phosphorus dopant concentration on the carrier mobility in ...

African Journals Online (AJOL)

This study investigated the effect of phosphorus dopant concentration on mobility of crystalline silicon (c-Si). It considers different temperature ranges, from 100 K to 500 K, and dopant concentration from 1012 cm-3 to 1020 cm-3 in relation to its effect on the mobility of the crystalline silicon. This study indicates that the ...

Current collapse imaging of Schottky gate AlGaN/GaN high electron mobility transistors by electric field-induced optical second-harmonic generation measurement

International Nuclear Information System (INIS)

Katsuno, Takashi; Ishikawa, Tsuyoshi; Ueda, Hiroyuki; Uesugi, Tsutomu; Manaka, Takaaki; Iwamoto, Mitsumasa

2014-01-01

Two-dimensional current collapse imaging of a Schottky gate AlGaN/GaN high electron mobility transistor device was achieved by optical electric field-induced second-harmonic generation (EFISHG) measurements. EFISHG measurements can detect the electric field produced by carriers trapped in the on-state of the device, which leads to current collapse. Immediately after (e.g., 1, 100, or 800 μs) the completion of drain-stress voltage (200 V) in the off-state, the second-harmonic (SH) signals appeared within 2 μm from the gate edge on the drain electrode. The SH signal intensity became weak with time, which suggests that the trapped carriers are emitted from the trap sites. The SH signal location supports the well-known virtual gate model for current collapse.

Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells

KAUST Repository

Melianas, Armantas

2015-11-05

In photovoltaic devices, the photo-generated charge carriers are typically assumed to be in thermal equilibrium with the lattice. In conventional materials, this assumption is experimentally justified as carrier thermalization completes before any significant carrier transport has occurred. Here, we demonstrate by unifying time-resolved optical and electrical experiments and Monte Carlo simulations over an exceptionally wide dynamic range that in the case of organic photovoltaic devices, this assumption is invalid. As the photo-generated carriers are transported to the electrodes, a substantial amount of their energy is lost by continuous thermalization in the disorder broadened density of states. Since thermalization occurs downward in energy, carrier motion is boosted by this process, leading to a time-dependent carrier mobility as confirmed by direct experiments. We identify the time and distance scales relevant for carrier extraction and show that the photo-generated carriers are extracted from the operating device before reaching thermal equilibrium.

Mobile Support For Logistics

Science.gov (United States)

2016-03-01

support wireless capabilities, such as Wi-Fi or LTE -based 4G cellular infrastructures, into the DOD’s enterprise software, GCSS-MC could be a large...fielded mobile devices through ViaSat Inc. ViaSat’s goal is to provide secure communications over 3G/4G/ LTE cellular and Wi-Fi networks, secure...or commercial carrier network. While these measures are not all encompassing for protecting mobile devices, they are a ways that drastically improve

High-frequency hearing loss among mobile phone users.

Science.gov (United States)

Velayutham, P; Govindasamy, Gopala Krishnan; Raman, R; Prepageran, N; Ng, K H

2014-01-01

The objective of this study is to assess high frequency hearing (above 8 kHz) loss among prolonged mobile phone users is a tertiary Referral Center. Prospective single blinded study. This is the first study that used high-frequency audiometry. The wide usage of mobile phone is so profound that we were unable to find enough non-users as a control group. Therefore we compared the non-dominant ear to the dominant ear using audiometric measurements. The study was a blinded study wherein the audiologist did not know which was the dominant ear. A total of 100 subjects were studied. Of the subjects studied 53% were males and 47% females. Mean age was 27. The left ear was dominant in 63%, 22% were dominant in the right ear and 15% did not have a preference. This study showed that there is significant loss in the dominant ear compared to the non-dominant ear (P mobile phone revealed high frequency hearing loss in the dominant ear (mobile phone used) compared to the non dominant ear.

Carrier transport and electronic structure in amorphous oxide semiconductor, a-InGaZnO4

International Nuclear Information System (INIS)

Takagi, Akihiro; Nomura, Kenji; Ohta, Hiromichi; Yanagi, Hiroshi; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

2005-01-01

Carrier transport properties in amorphous oxide semiconductor InGaZnO 4 (a-IGZO) thin films were investigated in detail using temperature dependence of Hall measurements. It was found that Hall mobility increased distinctly as carrier concentration increased. Unlikely conventional amorphous semiconductors such as a-Si/H, definite normal Hall voltage signals were observed on the films with carrier concentrations (N e )>10 16 cm -3 , and Hall mobilities as large as 15 cm 2 (Vs) -1 were attained in the films with N e >10 20 cm -3 . When N e was less than 10 19 cm -3 , the temperature dependence of Hall mobility showed thermally-activated behavior in spite that carrier concentration was independent of temperature. While, it changed to almost degenerate conduction at N e >10 18 cm -3 . These behaviors are similar to those observed in single-crystalline IGZO, and are explained by percolation conduction through distributed potential barriers which are formed in the vicinity of the conduction band bottom due to the randomness of the amorphous structure. The effective mass of a-IGZO was estimated to be ∼0.34 m e (m e is the mass of free electron) from optical data, which is almost the same as that of crystalline IGZO (∼0.32 m e )

Infrared absorption spectrum of free carriers in polar semiconductors. Progress report, July 1, 1979-June 30, 1980

International Nuclear Information System (INIS)

Jensen, B.

1980-02-01

The Drude Zener theory of the absorption of high frequency radiation by free carriers (inverse bremsstrahlung) has been extended into the quantum region (h-bar omega > k 0 T) in terms of a frequency dependent relaxation time which predicts the dc mobility in the quasiclassical limit. Numerical calculations of the frequency and concentration dependent electron scattering rate have been completed for InP, InAs, Ga 0 47 In 0 53 As, and previous results for GaAs extended to high carrier concentrations. When starting from a quantum statistical theory, the fact that n/sub q/oh-bar omega → k 0 T at low frequencies can be used to prevent the divergence of the coulomb scattering rate without inclusion of a screening radius. A result containing no adjustable parameters is found which predicts a mobility for uncompensated samples that decreases strongly at high concentrations. This has been observed in GaAs, and is not accounted for by the usual dc calculation which assumes h-bar omega = 0 and a screening parameter. Calculated results for GaAs are in good agreement with experimental measurements of the mobility which are found to be independent of a wide variety of conditions of material preparation. This indicates that disagreement with previous theoretical calculations was not due to compensation. Calculations for ZnSe and further investigation of the modification of the optical constants by the presence of an intense laser field and by a static magnetic field are currently planned

Effect of grain boundary on the field-effect mobility of microrod single crystal organic transistors.

Science.gov (United States)

Kim, Jaekyun; Kang, Jingu; Cho, Sangho; Yoo, Byungwook; Kim, Yong-Hoon; Park, Sung Kyu

2014-11-01

High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.

47 CFR 25.143 - Licensing provisions for the 1.6/2.4 GHz mobile-satellite service and 2 GHz mobile-satellite...

Science.gov (United States)

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Licensing provisions for the 1.6/2.4 GHz mobile-satellite service and 2 GHz mobile-satellite service. 25.143 Section 25.143 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses...

Micromagnetics on high-performance workstation and mobile computational platforms

Science.gov (United States)

Fu, S.; Chang, R.; Couture, S.; Menarini, M.; Escobar, M. A.; Kuteifan, M.; Lubarda, M.; Gabay, D.; Lomakin, V.

2015-05-01

The feasibility of using high-performance desktop and embedded mobile computational platforms is presented, including multi-core Intel central processing unit, Nvidia desktop graphics processing units, and Nvidia Jetson TK1 Platform. FastMag finite element method-based micromagnetic simulator is used as a testbed, showing high efficiency on all the platforms. Optimization aspects of improving the performance of the mobile systems are discussed. The high performance, low cost, low power consumption, and rapid performance increase of the embedded mobile systems make them a promising candidate for micromagnetic simulations. Such architectures can be used as standalone systems or can be built as low-power computing clusters.

Study of Charge Carrier Transport in GaN Sensors

Science.gov (United States)

Gaubas, Eugenijus; Ceponis, Tomas; Kuokstis, Edmundas; Meskauskaite, Dovile; Pavlov, Jevgenij; Reklaitis, Ignas

2016-01-01

Capacitor and Schottky diode sensors were fabricated on GaN material grown by hydride vapor phase epitaxy and metal-organic chemical vapor deposition techniques using plasma etching and metal deposition. The operational characteristics of these devices have been investigated by profiling current transients and by comparing the experimental regimes of the perpendicular and parallel injection of excess carrier domains. Profiling of the carrier injection location allows for the separation of the bipolar and the monopolar charge drift components. Carrier mobility values attributed to the hydride vapor phase epitaxy (HVPE) GaN material have been estimated as μe = 1000 ± 200 cm2/Vs for electrons, and μh = 400 ± 80 cm2/Vs for holes, respectively. Current transients under injection of the localized and bulk packets of excess carriers have been examined in order to determine the surface charge formation and polarization effects. PMID:28773418

Renewable energy carriers: Hydrogen or liquid air/nitrogen?

International Nuclear Information System (INIS)

Li Yongliang; Chen Haisheng; Zhang Xinjing; Tan Chunqing; Ding Yulong

2010-01-01

The world's energy demand is met mainly by the fossil fuels today. The use of such fuels, however, causes serious environmental issues, including global warming, ozone layer depletion and acid rains. A sustainable solution to the issues is to replace the fossil fuels with renewable ones. Implementing such a solution, however, requires overcoming a number of technological barriers including low energy density, intermittent supply and mobility of the renewable energy sources. A potential approach to overcoming these barriers is to use an appropriate energy carrier, which can store, transport and distribute energy. The work to be reported in this paper aims to assess and compare a chemical energy carrier, hydrogen, with a physical energy carrier, liquid air/nitrogen, and discuss potential applications of the physical carrier. The ocean energy is used as an example of the renewable energy sources in the work. The assessment and comparison are carried out in terms of the overall efficiency, including production, storage/transportation and energy extraction. The environmental impact, waste heat recovery and safety issues are also considered. It is found that the physical energy carrier may be a better alternative to the chemical energy carrier under some circumstances, particularly when there are waste heat sources.

Charge carrier transport and photogeneration in P3HT:PCBM photovoltaic blends.

Science.gov (United States)

Laquai, Frédéric; Andrienko, Denis; Mauer, Ralf; Blom, Paul W M

2015-06-01

This article reviews the charge transport and photogeneration in bulk-heterojunction solar cells made from blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and methano-fullerene (PCBM). The charge transport, specifically the hole mobility in the RR-P3HT phase of the polymer:fullerene photovoltaic blend, is dramatically affected by thermal annealing. The hole mobility increases more than three orders of magnitude and reaches a value of up to 2 × 10(-4) cm(2) V(-1) s(-1) after the thermal annealing process as a result of an improved semi-crystallinity of the film. This significant increase of the hole mobility balances the electron and hole mobilities in a photovoltaic blend in turn reducing space-charge formation, and this is the most important factor for the strong enhancement of the photovoltaic efficiency compared to an as cast, that is, non-annealed device. In fact, the balanced charge carrier mobility in RR-P3HT:PCBM blends in combination with a field- and temperature-independent charge carrier generation and greatly reduced non-geminate recombination explains the large quantum efficiencies mea-sured in P3HT:PCBM photovoltaic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Renewable carbohydrates are a potential high-density hydrogen carrier

Energy Technology Data Exchange (ETDEWEB)

Zhang, Y.-H. Percival [Biological Systems Engineering Department, 210-A Seitz Hall, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Institute for Critical Technology and Applied Sciences (ICTAS), Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); DOE BioEnergy Science Center (BESC), Oak Ridge, TN 37831 (United States)

2010-10-15

The possibility of using renewable biomass carbohydrates as a potential high-density hydrogen carrier is discussed here. Gravimetric density of polysaccharides is 14.8 H{sub 2} mass% where water can be recycled from PEM fuel cells or 8.33% H{sub 2} mass% without water recycling; volumetric densities of polysaccharides are >100 kg of H{sup 2}/m{sup 3}. Renewable carbohydrates (e.g., cellulosic materials and starch) are less expensive based on GJ than are other hydrogen carriers, such as hydrocarbons, biodiesel, methanol, ethanol, and ammonia. Biotransformation of carbohydrates to hydrogen by cell-free synthetic (enzymatic) pathway biotransformation (SyPaB) has numerous advantages, such as high product yield (12 H{sub 2}/glucose unit), 100% selectivity, high energy conversion efficiency (122%, based on combustion energy), high-purity hydrogen generated, mild reaction conditions, low-cost of bioreactor, few safety concerns, and nearly no toxicity hazards. Although SyPaB may suffer from current low reaction rates, numerous approaches for accelerating hydrogen production rates are proposed and discussed. Potential applications of carbohydrate-based hydrogen/electricity generation would include hydrogen bioreactors, home-size electricity generators, sugar batteries for portable electronics, sugar-powered passenger vehicles, and so on. Developments in thermostable enzymes as standardized building blocks for cell-free SyPaB projects, use of stable and low-cost biomimetic NAD cofactors, and accelerating reaction rates are among the top research and development priorities. International collaborations are urgently needed to solve the above obstacles within a short time. (author)

Piezoelectric scattering limited mobility of hybrid organic-inorganic perovskites CH3NH3PbI3

Science.gov (United States)

Lu, Ying-Bo; Kong, Xianghua; Chen, Xiaobin; Cooke, David G.; Guo, Hong

2017-01-01

Carrier mobility is one of the most important parameters for semiconducting materials and their use in optoelectronic devices. Here we report a systematic first principles analysis of the acoustic phonon scattering mechanism that limits the mobility of CH3NH3PbI3 (MAPbI3) perovskites. Due to the unique hybrid organic-inorganic structure, the mechanical, electronic and transport properties are dominated by the same factor, i.e. the weak interatomic bond and the easy rotation of methylammonium (MA) molecules under strain. Both factors make MAPbI3 soft. Rotation of MA molecule induces a transverse shift between Pb and I atoms, resulting in a very low deformation potential and a strong piezoelectricity in MAPbI3. Hence the carrier mobility of pristine MAPbI3 is limited by the piezoelectric scattering, which is consistent to the form of its temperature dependence. Our calculations suggest that in the pristine limit, a high mobility of about several thousand cm2 V−1 S−1 is expected for MAPbI3. PMID:28150743

Fundamental limits on the electron mobility of β-Ga2O3.

Science.gov (United States)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G

2017-06-14

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga 2 O 3 . We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi's golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga 2 O 3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga 2 O 3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 10 17 to 10 20 cm -3 . We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 10 19 cm -3 . We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

Fundamental limits on the electron mobility of β-Ga2O3

Science.gov (United States)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G.

2017-06-01

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga2O3. We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi’s golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga2O3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga2O3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 1017 to 1020 cm-3. We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 1019 cm-3. We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

On the Comparative Performance Analysis of Turbo-Coded Non-Ideal Sigle-Carrier and Multi-Carrier Waveforms over Wideband Vogler-Hoffmeyer HF Channels

Directory of Open Access Journals (Sweden)

F. Genc

2014-09-01

Full Text Available The purpose of this paper is to compare the turbo-coded Orthogonal Frequency Division Multiplexing (OFDM and turbo-coded Single Carrier Frequency Domain Equalization (SC-FDE systems under the effects of Carrier Frequency Offset (CFO, Symbol Timing Offset (STO and phase noise in wide-band Vogler-Hoffmeyer HF channel model. In mobile communication systems multi-path propagation occurs. Therefore channel estimation and equalization is additionally necessary. Furthermore a non-ideal local oscillator generally is misaligned with the operating frequency at the receiver. This causes carrier frequency offset. Hence in coded SC-FDE and coded OFDM systems; a very efficient, low complex frequency domain channel estimation and equalization is implemented in this paper. Also Cyclic Prefix (CP based synchronization synchronizes the clock and carrier frequency offset.The simulations show that non-ideal turbo-coded OFDM has better performance with greater diversity than non-ideal turbo-coded SC-FDE system in HF channel.

High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy

International Nuclear Information System (INIS)

Miyashita, Naoya; Ahsan, Nazmul; Monirul Islam, Muhammad; Okada, Yoshitaka; Inagaki, Makoto; Yamaguchi, Masafumi

2012-01-01

We report the highest mobility values above 2000 cm 2 /Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.

Enhancement of hole mobility in InSe monolayer via an InSe and black phosphorus heterostructure.

Science.gov (United States)

Ding, Yi-Min; Shi, Jun-Jie; Xia, Congxin; Zhang, Min; Du, Juan; Huang, Pu; Wu, Meng; Wang, Hui; Cen, Yu-Lang; Pan, Shu-Hang

2017-10-05

To enhance the low hole mobility (∼40 cm 2 V -1 s -1 ) of InSe monolayer, a novel two-dimensional (2D) van der Waals heterostructure made of InSe and black phosphorus (BP) monolayers with high hole mobility (∼10 3 cm 2 V -1 s -1 ) has been constructed and its structural and electronic properties are investigated using first-principles calculations. We find that the InSe/BP heterostructure exhibits a direct band gap of 1.39 eV and type-II band alignment with electrons (holes) located in the InSe (BP) layer. The band offsets of InSe and BP are 0.78 eV for the conduction band minimum and 0.86 eV for the valence band maximum, respectively. Surprisingly, the hole mobility in the InSe/BP heterostructure exceeds 10 4 cm 2 V -1 s -1 , which is one order of magnitude larger than the hole mobility of BP and three orders larger than that of the InSe monolayer. The electron mobility is also increased to 3 × 10 3 cm 2 V -1 s -1 . The physical reason has been analyzed deeply, and a universal method is proposed to improve the carrier mobility of 2D materials by forming heterostructures with them and other 2D materials with complementary properties. The InSe/BP heterostructure can thus be widely used in nanoscale InSe-based field-effect transistors, photodetectors and photovoltaic devices due to its type-II band alignment and high carrier mobility.

Data dissemination in the wild: A testbed for high-mobility MANETs

DEFF Research Database (Denmark)

Vingelmann, Peter; Pedersen, Morten Videbæk; Heide, Janus

2012-01-01

This paper investigates the problem of efficient data dissemination in Mobile Ad hoc NETworks (MANETs) with high mobility. A testbed is presented; which provides a high degree of mobility in experiments. The testbed consists of 10 autonomous robots with mobile phones mounted on them. The mobile...... information, and the goal is to convey that information to all devices. A strategy is proposed that uses UDP broadcast transmissions and random linear network coding to facilitate the efficient exchange of information in the network. An application is introduced that implements this strategy on Nokia phones...

The Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

KAUST Repository

Baran, Derya

2015-08-10

Non-radiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore it is possible to correlate changes in luminescence emission with changes in open-circuit voltage and in the charge carrier lifetime. Here we use luminescence studies combined with transient photovoltage and differential charging analyses to study the effect of polymer fractionation in indacenoedithiophene-co-benzothiadiazole (IDTBT):fullerene solar cells. In this system, polymer fractionation increases electroluminescence and reduces non-radiative recombination. High molecular weight and fractionated IDTBT polymers exhibit higher carrier lifetime-mobility product compared to their non-fractionated analogues, resulting in improved solar cell performance.

The Role of Polymer Fractionation in Energetic Losses and Charge Carrier Lifetimes of Polymer: Fullerene Solar Cells

KAUST Repository

Baran, Derya; Vezie, Michelle S; Gasparini, Nicola; Deledalle, Florent; Yao, Jizhong; Schroeder, Bob C.; Bronstein, Hugo; Ameri, Tayebeh; Kirchartz, Thomas; McCulloch, Iain; Nelson, Jenny; Brabec, Christoph J

2015-01-01

Non-radiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore it is possible to correlate changes in luminescence emission with changes in open-circuit voltage and in the charge carrier lifetime. Here we use luminescence studies combined with transient photovoltage and differential charging analyses to study the effect of polymer fractionation in indacenoedithiophene-co-benzothiadiazole (IDTBT):fullerene solar cells. In this system, polymer fractionation increases electroluminescence and reduces non-radiative recombination. High molecular weight and fractionated IDTBT polymers exhibit higher carrier lifetime-mobility product compared to their non-fractionated analogues, resulting in improved solar cell performance.

Role of band states and trap states in the electrical properties of organic semiconductors: Hopping versus mobility edge model

KAUST Repository

Mehraeen, Shafigh; Coropceanu, Veaceslav; Bré das, Jean-Luc

2013-01-01

We compare the merits of a hopping model and a mobility edge model in the description of the effect of charge-carrier concentration on the electrical conductivity, carrier mobility, and Fermi energy of organic semiconductors. We consider the case

A three-dimensional nitrogen-doped graphene structure: a highly efficient carrier of enzymes for biosensors

Science.gov (United States)

Guo, Jingxing; Zhang, Tao; Hu, Chengguo; Fu, Lei

2015-01-01

In recent years, graphene-based enzyme biosensors have received considerable attention due to their excellent performance. Enormous efforts have been made to utilize graphene oxide and its derivatives as carriers of enzymes for biosensing. However, the performance of these sensors is limited by the drawbacks of graphene oxide such as slow electron transfer rate, low catalytic area and poor conductivity. Here, we report a new graphene-based enzyme carrier, i.e. a highly conductive 3D nitrogen-doped graphene structure (3D-NG) grown by chemical vapour deposition, for highly effective enzyme-based biosensors. Owing to the high conductivity, large porosity and tunable nitrogen-doping ratio, this kind of graphene framework shows outstanding electrical properties and a large surface area for enzyme loading and biocatalytic reactions. Using glucose oxidase (GOx) as a model enzyme and chitosan (CS) as an efficient molecular binder of the enzyme, our 3D-NG based biosensors show extremely high sensitivity for the sensing of glucose (226.24 μA mM-1 m-2), which is almost an order of magnitude higher than those reported in most of the previous studies. The stable adsorption and outstanding direct electrochemical behaviour of the enzyme on the nanocomposite indicate the promising application of this 3D enzyme carrier in high-performance electrochemical biosensors or biofuel cells.In recent years, graphene-based enzyme biosensors have received considerable attention due to their excellent performance. Enormous efforts have been made to utilize graphene oxide and its derivatives as carriers of enzymes for biosensing. However, the performance of these sensors is limited by the drawbacks of graphene oxide such as slow electron transfer rate, low catalytic area and poor conductivity. Here, we report a new graphene-based enzyme carrier, i.e. a highly conductive 3D nitrogen-doped graphene structure (3D-NG) grown by chemical vapour deposition, for highly effective enzyme

Variation of minority charge carrier lifetime in high-resistance p-type silicon under irradiation

International Nuclear Information System (INIS)

Basheleishvili, Z.V.; Garnyk, V.S.; Gorin, S.N.; Pagava, T.A.

1984-01-01

The minority carrier lifetime (tau) variation was studied in the process of p-type silicon bombardment with fast 8 MeV electrons. The irradiation and all measurements were carried out at room temperature. The tau quantity was measured by the photoconductivity attenuation method at a low injection level 20% measurement error; the resistivity was measured by the four-probe method (10% error). The resistivity and minority charge carrier lifetime tau are shown to increase with the exposure dose. It is supposed that as radiation dose increases, the rearrangement of the centres responsible for reducing the lifetime occurs and results in a tau increase in the material being irradiated, however the tau value observed in the original samples is not attained. The restoration of the minority carrier lifetime in p-type high-resistance silicon with a growing exposure dose might proceed due to reduction in the free carrier concentration

Evaluation of electron mobility in InSb quantum wells by means of percentage-impact

International Nuclear Information System (INIS)

Mishima, T. D.; Edirisooriya, M.; Santos, M. B.

2014-01-01

In order to quantitatively analyze the contribution of each scattering factor toward the total carrier mobility, we use a new convenient figure-of-merit, named a percentage impact. The mobility limit due to a scattering factor, which is widely used to summarize a scattering analysis, has its own advantage. However, a mobility limit is not quite appropriate for the above purpose. A comprehensive understanding of the difference in contribution among many scattering factors toward the total carrier mobility can be obtained by evaluating percentage impacts of scattering factors, which can be straightforwardly calculated from their mobility limits and the total mobility. Our percentage impact analysis shows that threading dislocation is one of the dominant scattering factors for the electron transport in InSb quantum wells at room temperature

Quantitative evaluation of spatial scale of carrier trapping at grain boundary by GHz-microwave dielectric loss spectroscopy

Science.gov (United States)

Choi, W.; Tsutsui, Y.; Miyakai, T.; Sakurai, T.; Seki, S.

2017-11-01

Charge carrier mobility is an important primary parameter for the electronic conductive materials, and the intrinsic limit of the mobility has been hardly access by conventional direct-current evaluation methods. In the present study, intra-grain hole mobility of pentacene thin films was estimated quantitatively using microwave-based dielectric loss spectroscopy (time-resolved microwave conductivity measurement) in alternating current mode of charge carrier local motion. Metal-insulator-semiconductor devices were prepared with different insulating polymers or substrate temperature upon vacuum deposition of the pentacene layer, which afforded totally four different grain-size conditions of pentacene layers. Under the condition where the local motion was determined by interfacial traps at the pentacene grain boundaries (grain-grain interfaces), the observed hole mobilities were plotted against the grain sizes, giving an excellent correlation fit successfully by a parabolic function representative of the boarder length. Consequently, the intra-grain mobility and trap-release time of holes were estimated as 15 cm2 V-1 s-1 and 9.4 ps.

Hybrid complementary circuits based on p-channel organic and n-channel metal oxide transistors with balanced carrier mobilities of up to 10 cm2/Vs

KAUST Repository

Isakov, Ivan

2016-12-29

We report the development of hybrid complementary inverters based on p-channel organic and n-channel metal oxide thin-film transistors (TFTs) both processed from solution at <200 °C. For the organic TFTs, a ternary blend consisting of the small-molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene, the polymer indacenodithiophene-benzothiadiazole (CIDT-BT) and the p-type dopant CF was employed, whereas the isotype InO/ZnO heterojunction was used for the n-channel TFTs. When integrated on the same substrate, p- and n-channel devices exhibited balanced carrier mobilities up to 10 cm/Vs. Hybrid complementary inverters based on these devices show high signal gain (>30 V/V) and wide noise margins (70%). The moderate processing temperatures employed and the achieved level of device performance highlight the tremendous potential of the technology for application in the emerging sector of large-area microelectronics.

Hybrid complementary circuits based on p-channel organic and n-channel metal oxide transistors with balanced carrier mobilities of up to 10 cm2/Vs

KAUST Repository

Isakov, Ivan; Paterson, Alexandra F.; Solomeshch, Olga; Tessler, Nir; Zhang, Qiang; Li, Jun; Zhang, Xixiang; Fei, Zhuping; Heeney, Martin; Anthopoulos, Thomas D.

2016-01-01

We report the development of hybrid complementary inverters based on p-channel organic and n-channel metal oxide thin-film transistors (TFTs) both processed from solution at <200 °C. For the organic TFTs, a ternary blend consisting of the small-molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene, the polymer indacenodithiophene-benzothiadiazole (CIDT-BT) and the p-type dopant CF was employed, whereas the isotype InO/ZnO heterojunction was used for the n-channel TFTs. When integrated on the same substrate, p- and n-channel devices exhibited balanced carrier mobilities up to 10 cm/Vs. Hybrid complementary inverters based on these devices show high signal gain (>30 V/V) and wide noise margins (70%). The moderate processing temperatures employed and the achieved level of device performance highlight the tremendous potential of the technology for application in the emerging sector of large-area microelectronics.

Development of high-performance transparent conducting oxides and their impact on the performance of CdS/CdTe solar cells

Energy Technology Data Exchange (ETDEWEB)

Coutts, T.J.; Wu, X.; Sheldon, P.; Rose, D.H. [National Renewable Energy Lab., Golden, CO (United States)

1998-09-01

This paper begins with a review of the modeled performance of transparent conducting oxides (TCOs) as a function of their free-carrier concentration, mobility, and film thickness. It is shown that it is vital to make a film with high mobility to minimize the width and height of the free-carrier absorption band, and to optimize the optical properties. The free-carrier concentration must be kept sufficiently small that the absorption band does not extend into that part of the spectrum to which the solar cell responds. Despite this consideration, a high electrical conductivity is essential to minimize series resistance losses. Hence, a high mobility is vital for these materials. The fabrication of thin-films of cadmium stannate is then discussed, and their performance is compared with that of tin oxide, both optically and as these materials influence the performance of CdTe solar cells.

Hierarchical micro-mobility management in high-speed multihop access networks

Institute of Scientific and Technical Information of China (English)

TANG Bi-hua; MA Xiao-lei; LIU Yuan-an; GAO Jin-chun

2006-01-01

This article integrates the hierarchical micro-mobility management and the high-speed multihop access networks (HMAN), to accomplish the smooth handover between different access routers. The proposed soft handover scheme in the high-speed HMAN can solve the micro-mobility management problem in the access network. This article also proposes the hybrid access router (AR) advertisement scheme and AR selection algorithm, which uses the time delay and stable route to the AR as the gateway selection parameters. By simulation, the proposed micro-mobility management scheme can achieve high packet delivery fraction and improve the lifetime of network.

Mobile marketing for mobile games

OpenAIRE

Vu, Giang

2016-01-01

Highly developed mobile technology and devices enable the rise of mobile game industry and mobile marketing. Hence mobile marketing for mobile game is an essential key for a mobile game success. Even though there are many articles on marketing for mobile games, there is a need of highly understanding mobile marketing strategies, how to launch a mobile campaign for a mobile game. Besides that, it is essential to understand the relationship between mobile advertising and users behaviours. There...

Influence of the number of layers on ultrathin CsSnI3 perovskite: from electronic structure to carrier mobility

Science.gov (United States)

Liu, Biao; Long, Mengqiu; Cai, Meng-Qiu; Yang, Junliang

2018-03-01

Inorganic halide perovskites have attracted great attention in recent years as promising materials for optoelectronic devices, with ultrathin inorganic halide perovskites showing excellent properties and great potential applications. Herein, the intrinsic electronic and optical properties of ultrathin cesium tin tri-iodide (CsSnI3) perovskite with a varying number of layers are explored using first-principles calculations. The results reveal that ultrathin CsSnI3 is a direct band gap semiconductor, and the band gap continues to increase to 1.83 eV from 1.28 eV as the number of layers is reduced to one layer from the bulk. By decreasing the number of layers, the effective mass of ultrathin CsSnI3 increases, and the optical absorption intensity along the x and y directions shows that the linear dichroism becomes stronger and stronger. Furthermore, the carrier mobilities (µ) can be predicted, and they show obvious in-plane anisotropy. The µ of the electrons is higher than that of the holes, and the electron mobility along the y direction is higher than that along the x direction. The layer thickness does not distinctly influence the µ. The difference in the atomic orbital distribution has the nature of obvious anisotropy in ultrathin CsSnI3. This work suggests that ultrathin inorganic perovskite could be a potential candidate for future nano-optoelectronic devices.

High-electric-field-stress-induced degradation of SiN passivated AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Wen-Ping, Gu; Huan-Tao, Duan; Jin-Yu, Ni; Yue, Hao; Jin-Cheng, Zhang; Qian, Feng; Xiao-Hua, Ma

2009-01-01

AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current I Dsat , maximal transconductance g m , and the positive shift of threshold voltage V TH at high drain-source voltage V DS . The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEG depletion a little during the high-electric-field stress. After the hot carrier stress with V DS = 20 V and V GS = 0 V applied to the device for 10 4 sec, the SiN passivation decreases the stress-induced degradation of I Dsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of I Dsat , which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Deterministic patterned growth of high-mobility large-crystal graphene: a path towards wafer scale integration

Science.gov (United States)

Miseikis, Vaidotas; Bianco, Federica; David, Jérémy; Gemmi, Mauro; Pellegrini, Vittorio; Romagnoli, Marco; Coletti, Camilla

2017-06-01

We demonstrate rapid deterministic (seeded) growth of large single-crystals of graphene by chemical vapour deposition (CVD) utilising pre-patterned copper substrates with chromium nucleation sites. Arrays of graphene single-crystals as large as several hundred microns are grown with a periodicity of up to 1 mm. The graphene is transferred to target substrates using aligned and contamination- free semi-dry transfer. The high quality of the synthesised graphene is confirmed by Raman spectroscopy and transport measurements, demonstrating room-temperature carrier mobility of 21 000 cm2 V-1 s-1 when transferred on top of hexagonal boron nitride. By tailoring the nucleation of large single-crystals according to the desired device geometry, it will be possible to produce complex device architectures based on single-crystal graphene, thus paving the way to the adoption of CVD graphene in wafer-scale fabrication.

Effective electro-optical modulation with high extinction ratio by a graphene-silicon microring resonator

DEFF Research Database (Denmark)

Ding, Yunhong; Zhu, Xiaolong; Xiao, Sanshui

2015-01-01

Graphene opens up for novel optoelectronic applications thanks to its high carrier mobility, ultra-large absorption bandwidth, and extremely fast material response. In particular, the opportunity to control optoelectronic properties through tuning of the Fermi level enables electro-optical modula......Graphene opens up for novel optoelectronic applications thanks to its high carrier mobility, ultra-large absorption bandwidth, and extremely fast material response. In particular, the opportunity to control optoelectronic properties through tuning of the Fermi level enables electro...... with an extinction ratio of 3.8 dB is successfully demonstrated by applying a square-waveform with a 4 V peak-to-peak voltage....

High school students’ usage behavior and views about mobile phones

Directory of Open Access Journals (Sweden)

Ahmet Ergin

2014-09-01

Full Text Available Objective: The aim of this study was to determine high school students’ usage behavior and views about mobile phones. Methods:Totally 253 (85.5% students educated at Honaz High School within the academic year 2010-2011, participated to this cross-sectional study and a questionnaire consisting of 42 questions which aimed to determine usage behavior and views about mobile phones was administered to the students. Results:The mean age of the students was 16.1 ± 1.1 years, and 56.9% of them were girl. 79.8% of students have mobile phone and 53.9% of them make daily average of over 30 minutes mobile phone calls. 76.1% of participants stated that they did not use headphones, 78.1% did not turn off their mobile phones when they are sleeping and 67.3% put it right next to them or under the pillow. 83.1% of students think mobile phones are harmful for human health, 56.7% think the base stations are harmful to human health and the environment, 91.3% think mobile phones are harmful for children, pregnant women and elderly people. Conclusion: It is found that students’ mobile phone ownership is widespread, the age of starting to use mobile phone and headphones usage is low, knowledge about the base stations is not adequate.

On the high charge-carrier mobility in polyaniline molecular channels in nanogaps between carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Emelianov, A. V., E-mail: emmsowton@gmail.com; Romashkin, A. V.; Tsarik, K. A. [National Research University of Electronic Technology (MIET) (Russian Federation); Nasibulin, A. G. [Skolkovo Institute of Science and Technology (Russian Federation); Nevolin, V. K.; Bobrinetskiy, I. I. [National Research University of Electronic Technology (MIET) (Russian Federation)

2017-04-15

This study is devoted to the fabrication of molecular semiconductor channels based on polymer molecules with nanoscale electrodes made of single-walled carbon nanotubes. A reproducible technology for forming nanoscale gaps in carbon nanotubes using a focused Ga{sup +} ion beam is proposed. Polyaniline molecules are deposited into nanogaps up to 30 nm wide between nanotubes by electrophoresis from N-methyl-2-pyrrolidone solution. As a result, molecular organic transistors are fabricated, in which the field effect is studied and the molecular-channel mobility is determined as 0.1 cm{sup 2}/(V s) at an on/off current ratio of 5 × 10{sup 2}.

Ultrafast carrier dynamics in Br.sup.+./sup.-bombarded InP studied by time-resolved terahertz spectroscopy

Czech Academy of Sciences Publication Activity Database

Němec, Hynek; Fekete, Ladislav; Kadlec, Filip; Kužel, Petr

2008-01-01

Roč. 78, č. 23 (2008), 235206/1-235206/7 ISSN 1098-0121 R&D Projects: GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : InP * carrier lifetime * carrier mobility * ultrafast * ion-bombardment * terahertz Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

Trustworthy execution on mobile devices

CERN Document Server

Vasudevan, Amit; Newsome, James

2013-01-01

This brief considers the various stakeholders in today's mobile device ecosystem, and analyzes why widely-deployed hardware security primitives on mobile device platforms are inaccessible to application developers and end-users. Existing proposals are also evaluated for leveraging such primitives, and proves that they can indeed strengthen the security properties available to applications and users, without reducing the properties currently enjoyed by OEMs and network carriers. Finally, this brief makes recommendations for future research that may yield practical and deployable results.

Mobility activation in thermally deposited CdSe thin films

Indian Academy of Sciences (India)

Effect of illumination on mobility has been studied from the photocurrent decay characteristics of thermally evaporated CdSe thin films deposited on suitably cleaned glass substrate held at elevated substrate temperatures. The study indicates that the mobilities of the carriers of different trap levels are activated due to the ...

High accuracy positioning using carrier-phases with the opensource GPSTK software

OpenAIRE

Salazar Hernández, Dagoberto José; Hernández Pajares, Manuel; Juan Zornoza, José Miguel; Sanz Subirana, Jaume

2008-01-01

The objective of this work is to show how using a proper GNSS data management strategy, combined with the flexibility provided by the open source "GPS Toolkit" (GPSTk), it is possible to easily develop both simple code-based processing strategies as well as basic high accuracy carrier-phase positioning techniques like Precise Point Positioning (PPP

Charge carrier transport properties in layer structured hexagonal boron nitride

Directory of Open Access Journals (Sweden)

T. C. Doan

2014-10-01

Full Text Available Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV, hexagonal boron nitride (hBN has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K. The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0−α with α = 3.02, satisfying the two-dimensional (2D carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1, which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

High mobility two-dimensional hole gases in GaAs/AlGaAs heterostructures; Hochbewegliche zweidimensionale Lochsysteme in GaAs/AlGaAs Heterostrukturen

Energy Technology Data Exchange (ETDEWEB)

Gerl, Christian

2009-10-14

This thesis outlines the fabrication of high mobility two-dimensional hole-gases (2DHG) in GaAs/AlGaAs heterostructures with molecular beam epitaxy (MBE) and their characterization with magnetotransport measurements at low temperatures between 4 K and 30 mK. Here the optimization of the carrier mobility is focused. This will be achieved by introducing a novel carbon-filament doping source, with which contaminations of the MBE system and therefore in the grown layers can be reduced and by vary the band structure design to minimize scattering processes. With the help of these actions, hole mobilities above 1 E6 cm{sup 2}/Vs are achievable, what reflects an increase of factor 3 in the (001)- and factor 6.5 in the (110)- oriented transport plane compared to common 2DHGs. Furthermore states of the fractional Quantum Hall Effect can be observed in these 2DHGs, only visible in n-doped 2D systems so fare. Magnetotransport measurements on 2DHGs with aluminum gates reveal a hysteretic behavior of the carrier density with respect to the gate potential which can be attributed to the incorporation mechanisms of carbon atoms as acceptor. Temperature dependent magnetotransport measurements allow the evaluation of effective mass and quantum scattering time as well as the dependence of these parameters from the band structure design. In these experiments an aperiodic behavior of the Shubnikov-de Haas oscillations can be observed in the inverse magnetic field, which is attributed to the position of the fermi energy in the immediate vicinity of crossing regions of the complex Landau fan of 2DHGs. (orig.)

47 CFR 22.409 - Developmental authorization for a new Public Mobile Service or technology.

Science.gov (United States)

2010-10-01

... Mobile Service or technology. 22.409 Section 22.409 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES PUBLIC MOBILE SERVICES Developmental Authorizations § 22.409 Developmental authorization for a new Public Mobile Service or technology. The FCC may grant applications for...

Interface-controlled, high-mobility organic transistors

NARCIS (Netherlands)

Jurchescu, Oana D.; Popinciuc, Mihaita; van Wees, Bart J.; Palstra, Thomas T. M.

2007-01-01

The achievement of high mobilities in field-effect transistors (FETs) is one of the main challenges for the widespread application of organic conductors in devices. Good device performance of a single-crystal pentacene FET requires both removal of impurity molecules from the bulk and the

High-frequency, scaled graphene transistors on diamond-like carbon

NARCIS (Netherlands)

Wu, Y.; Lin, Y.M.; Bol, A.A.; Jenkins, K.A.; Xia, F.; Farmer, D.B.; Zu, Y.; Avouris, Ph.

2011-01-01

Owing to its high carrier mobility and saturation velocity, graphene has attracted enormous attention in recent years In particular, high-performance graphene transistors for radio-frequency (r.f.) applications are of great interest. Synthesis of large-scale graphene sheets of high quality and at

A combined strategy for screening a clustered mobile population returning from highly endemic areas for Plasmodium falciparum.

Science.gov (United States)

Li, Mei; Li, Jun; Xia, Zhigui; Xiao, Ning; Jiang, Weikang; Wen, Yongkang

2017-04-30

Early and accurate diagnosis of imported malaria cases in clusters is crucial for protecting the health of patients and local populations, especially confirmed parasitic persons who are asymptomatic. A total of 226 gold miners who had stayed in highly endemic areas of Ghana for more than six months and returned in clusters were selected randomly. Blood samples from them were tested with microscopy, nest polymerase chain reaction, and rapid diagnostic test (RDT). The sensitivity, specificity, predictive values, agreement rate, and Youden's index of each of three diagnostic methods were calculated and compared with the defined gold standard. A quick and efficient way to respond to screening such a clustered mobile population was predicted and analyzed by evaluating two assumed results of combining microscopy and RDT with or without symptoms of illness. The rate of the carriers of malaria parasites in the populations of gold miners was 19.47%, including 39 P. falciparum. Among the three diagnostic methods, the microscopy method showed the highest specificity, while the RDT method showed the highest sensitivity but the lowest specificity in detecting P. falciparum. The assumed results of combining RDT and microscopy with symptoms showed the best results among all the test results in screening P. falciparum. It was too complex and difficult to catch all parasite carriers in a short period of time among populations with such a complicated situation as that in Shanglin County. A strategy of combing microscopy and RDT for diagnosis is highly recommended.

The effect of charged quantum dots on the mobility of a two-dimensional electron gas: How important is the Coulomb scattering?

International Nuclear Information System (INIS)

Kurzmann, A.; Beckel, A.; Lorke, A.; Geller, M.; Ludwig, A.; Wieck, A. D.

2015-01-01

We have investigated the influence of a layer of charged self-assembled quantum dots (QDs) on the mobility of a nearby two-dimensional electron gas (2DEG). Time-resolved transconductance spectroscopy was used to separate the two contributions of the change in mobility, which are: (i) The electrons in the QDs act as Coulomb scatterers for the electrons in the 2DEG. (ii) The screening ability and, hence, the mobility of the 2DEG decreases when the charge carrier density is reduced by the charged QDs, i.e., the mobility itself depends on the charge carrier concentration. Surprisingly, we find a negligible influence of the Coulomb scattering on the mobility for a 2DEG, separated by a 30 nm tunneling barrier to the layer of QDs. This means that the mobility change is completely caused by depletion, i.e., reduction of the charge carrier density in the 2DEG, which indirectly influences the mobility

Kinetics of non-equilibrium carries in high-resistance materials

International Nuclear Information System (INIS)

Arkhipov, V.I.; Rudenko, A.I.

1979-01-01

The kinetics of equilibrium carriers of high-resistance material samples is analytically studied to investigate and control the parameters and properties of these materials. Nonequilibrium carriers were generated by electron beam in these samples near by one of the contacts. The carrier drift causes the transient current. The study of it permits to make a conclusion about carrier mobility, their capture and release times and also about zone structure of material. Both the model taking into account energy-level transitions and the model taking into account the conduction zone interaction with local energy- level are shown to have features of anomalous behaviour

SC-FDMA for mobile communications

CERN Document Server

Abd El-Samie, Fathi E

2013-01-01

SC-FDMA for Mobile Communications examines Single-Carrier Frequency Division Multiple Access (SC-FDMA). Explaining this rapidly evolving system for mobile communications, it describes its advantages and limitations and outlines possible solutions for addressing its current limitations. The book explores the emerging trend of cooperative communication with SC-FDMA and how it can improve the physical layer security. It considers the design of distributed coding schemes and protocols for wireless relay networks where users cooperate to send their data to the destination. Supplying you with the re

Multiscale transparent electrode architecture for efficient light management and carrier collection in solar cells.

Science.gov (United States)

Boccard, Mathieu; Battaglia, Corsin; Hänni, Simon; Söderström, Karin; Escarré, Jordi; Nicolay, Sylvain; Meillaud, Fanny; Despeisse, Matthieu; Ballif, Christophe

2012-03-14

The challenge for all photovoltaic technologies is to maximize light absorption, to convert photons with minimal losses into electric charges, and to efficiently extract them to the electrical circuit. For thin-film solar cells, all these tasks rely heavily on the transparent front electrode. Here we present a multiscale electrode architecture that allows us to achieve efficiencies as high as 14.1% with a thin-film silicon tandem solar cell employing only 3 μm of silicon. Our approach combines the versatility of nanoimprint lithography, the unusually high carrier mobility of hydrogenated indium oxide (over 100 cm(2)/V/s), and the unequaled light-scattering properties of self-textured zinc oxide. A multiscale texture provides light trapping over a broad wavelength range while ensuring an optimum morphology for the growth of high-quality silicon layers. A conductive bilayer stack guarantees carrier extraction while minimizing parasitic absorption losses. The tunability accessible through such multiscale electrode architecture offers unprecedented possibilities to address the trade-off between cell optical and electrical performance. © 2012 American Chemical Society

Tunable electron heating induced giant magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system.

Science.gov (United States)

Wang, Zhuo; Samaraweera, R L; Reichl, C; Wegscheider, W; Mani, R G

2016-12-07

Electron-heating induced by a tunable, supplementary dc-current (I dc ) helps to vary the observed magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system. The magnetoresistance at B = 0.3 T is shown to progressively change from positive to negative with increasing I dc , yielding negative giant-magnetoresistance at the lowest temperature and highest I dc . A two-term Drude model successfully fits the data at all I dc and T. The results indicate that carrier heating modifies a conductivity correction σ 1 , which undergoes sign reversal from positive to negative with increasing I dc , and this is responsible for the observed crossover from positive- to negative- magnetoresistance, respectively, at the highest B.

Photocatalytic hydrogen generation enhanced by band gap narrowing and improved charge carrier mobility in AgTaO3 by compensated co-doping.

Science.gov (United States)

Li, Min; Zhang, Junying; Dang, Wenqiang; Cushing, Scott K; Guo, Dong; Wu, Nianqiang; Yin, Penggang

2013-10-14

The correlation of the electronic band structure with the photocatalytic activity of AgTaO3 has been studied by simulation and experiments. Doping wide band gap oxide semiconductors usually introduces discrete mid-gap states, which extends the light absorption but has limited benefit for photocatalytic activity. Density functional theory (DFT) calculations show that compensated co-doping in AgTaO3 can overcome this problem by increasing the light absorption and simultaneously improving the charge carrier mobility. N/H and N/F co-doping can delocalize the discrete mid-gap states created by sole N doping in AgTaO3, which increases the band curvature and the electron-to-hole effective mass ratio. In particular, N/F co-doping creates a continuum of states that extend the valence band of AgTaO3. N/F co-doping thus improves the light absorption without creating the mid-gap states, maintaining the necessary redox potentials for water splitting and preventing from charge carrier trapping. The experimental results have confirmed that the N/F-codoped AgTaO3 exhibits a red-shift of the absorption edge in comparison with the undoped AgTaO3, leading to remarkable enhancement of photocatalytic activity toward hydrogen generation from water.

Non-contact, non-destructive, quantitative probing of interfacial trap sites for charge carrier transport at semiconductor-insulator boundary

Energy Technology Data Exchange (ETDEWEB)

Choi, Wookjin; Miyakai, Tomoyo; Sakurai, Tsuneaki; Saeki, Akinori [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Yokoyama, Masaaki [Kaneka Fundamental Technology Research Alliance Laboratories, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Seki, Shu, E-mail: seki@chem.eng.osaka-u.ac.jp [Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Kaneka Fundamental Technology Research Alliance Laboratories, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan)

2014-07-21

The density of traps at semiconductor–insulator interfaces was successfully estimated using microwave dielectric loss spectroscopy with model thin-film organic field-effect transistors. The non-contact, non-destructive analysis technique is referred to as field-induced time-resolved microwave conductivity (FI-TRMC) at interfaces. Kinetic traces of FI-TRMC transients clearly distinguished the mobile charge carriers at the interfaces from the immobile charges trapped at defects, allowing both the mobility of charge carriers and the number density of trap sites to be determined at the semiconductor-insulator interfaces. The number density of defects at the interface between evaporated pentacene on a poly(methylmethacrylate) insulating layer was determined to be 10{sup 12 }cm{sup −2}, and the hole mobility was up to 6.5 cm{sup 2} V{sup −1} s{sup −1} after filling the defects with trapped carriers. The FI-TRMC at interfaces technique has the potential to provide rapid screening for the assessment of interfacial electronic states in a variety of semiconductor devices.

Electron mobility in the inversion layers of fully depleted SOI films

Energy Technology Data Exchange (ETDEWEB)

Zaitseva, E. G., E-mail: ZaytsevaElza@yandex.ru; Naumova, O. V.; Fomin, B. I. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2017-04-15

The dependences of the electron mobility μ{sub eff} in the inversion layers of fully depleted double–gate silicon-on-insulator (SOI) metal–oxide–semiconductor (MOS) transistors on the density N{sub e} of induced charge carriers and temperature T are investigated at different states of the SOI film (inversion–accumulation) from the side of one of the gates. It is shown that at a high density of induced charge carriers of N{sub e} > 6 × 10{sup 12} cm{sup –2} the μeff(T) dependences allow the components of mobility μ{sub eff} that are related to scattering at surface phonons and from the film/insulator surface roughness to be distinguished. The μ{sub eff}(N{sub e}) dependences can be approximated by the power functions μ{sub eff}(N{sub e}) ∝ N{sub e}{sup −n}. The exponents n in the dependences and the dominant mechanisms of scattering of electrons induced near the interface between the SOI film and buried oxide are determined for different N{sub e} ranges and film states from the surface side.

Effects of carrier concentrations on the charge transport properties in monolayer silicene

International Nuclear Information System (INIS)

Abidin, B I; Yeoh, K H; Yong, T K; Ong, D S

2017-01-01

Using analytical band Monte Carlo approach, we have carried out a systematic study on the effects of carrier concentrations on the steady-state and transient electron transports that occur within a monolayer silicene. In particular, we have observed the following: First at steady-state, the electron mobility reduces with higher carrier concentrations. Secondly, in the transient regime we found that the drift velocity overshoot can be controlled by varying the carrier concentrations. We uncover that at carrier concentration of 1  ×  10 13 cm −2 , the drift velocity overshoot can reach up to 3.8  ×  10 7 cm s −1 which is close to the steady-state drift velocity saturation of graphene. Thirdly, the distance of the velocity over shoot can be further extended with higher carrier concentrations. Our findings could be useful and can be used as benchmark for future development of nanoscale silicene based devices. (paper)

Sensitivity of GRETINA position resolution to hole mobility

Energy Technology Data Exchange (ETDEWEB)

Prasher, V.S. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Cromaz, M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Merchan, E.; Chowdhury, P. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Crawford, H.L. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Lister, C.J. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Campbell, C.M.; Lee, I.Y.; Macchiavelli, A.O. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Radford, D.C. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Wiens, A. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2017-02-21

The sensitivity of the position resolution of the gamma-ray tracking array GRETINA to the hole charge-carrier mobility parameter is investigated. The χ{sup 2} results from a fit of averaged signal (“superpulse”) data exhibit a shallow minimum for hole mobilities 15% lower than the currently adopted values. Calibration data on position resolution is analyzed, together with simulations that isolate the hole mobility dependence of signal decomposition from other effects such as electronics cross-talk. The results effectively exclude hole mobility as a dominant parameter for improving the position resolution for reconstruction of gamma-ray interaction points in GRETINA.

Highly immunogenic and fully synthetic peptide-carrier constructs targetting GnRH

DEFF Research Database (Denmark)

Beekman, N.J.C.M.; Schaaper, W.M.M.; Turkstra, J.A.

1999-01-01

To use peptides as synthetic vaccines, they have to be coupled to a carrier protein to make them more immunogenic. Coupling efficiency between a carrier protein and a peptide, however, is difficult to control with respect to loading density of the peptide, This makes these carrier proteins poorly...... for the induction of antibodies against GnRH and immunocastration of pigs....

Charge carrier motion in disordered conjugated polymers: a multiscale ab-initio study

Energy Technology Data Exchange (ETDEWEB)

Vukmirovic, Nenad; Wang, Lin-Wang

2009-11-10

We developed an ab-initio multiscale method for simulation of carrier transport in large disordered systems, based on direct calculation of electronic states and electron-phonon coupling constants. It enabled us to obtain the never seen before rich microscopic details of carrier motion in conjugated polymers, which led us to question several assumptions of phenomenological models, widely used in such systems. The macroscopic mobility of disordered poly(3- hexylthiophene) (P3HT) polymer, extracted from our simulation, is in agreement with experimental results from the literature.

Carbohydrate-Assisted Combustion Synthesis To Realize High-Performance Oxide Transistors.

Science.gov (United States)

Wang, Binghao; Zeng, Li; Huang, Wei; Melkonyan, Ferdinand S; Sheets, William C; Chi, Lifeng; Bedzyk, Michael J; Marks, Tobin J; Facchetti, Antonio

2016-06-08

Owing to high carrier mobilities, good environmental/thermal stability, excellent optical transparency, and compatibility with solution processing, thin-film transistors (TFTs) based on amorphous metal oxide semiconductors (AOSs) are promising alternatives to those based on amorphous silicon (a-Si:H) and low-temperature (IGZO) TFTs suffer from low carrier mobilities and/or inferior bias-stress stability versus their sputtered counterparts. Here we report that three types of environmentally benign carbohydrates (sorbitol, sucrose, and glucose) serve as especially efficient fuels for IGZO film combustion synthesis to yield high-performance TFTs. The results indicate that these carbohydrates assist the combustion process by lowering the ignition threshold temperature and, for optimal stoichiometries, enhancing the reaction enthalpy. IGZO TFT mobilities are increased to >8 cm(2) V(-1) s(-1) on SiO2/Si gate dielectrics with significantly improved bias-stress stability. The first correlations between precursor combustion enthalpy and a-MO densification/charge transport are established.

Problems of noise modeling in the presence of total current branching in high electron mobility transistor and field-effect transistor channels

International Nuclear Information System (INIS)

Shiktorov, P; Starikov, E; Gružinskis, V; Varani, L; Sabatini, G; Marinchio, H; Reggiani, L

2009-01-01

In the framework of analytical and hydrodynamic models for the description of carrier transport and noise in high electron mobility transistor/field-effect transistor channels the main features of the intrinsic noise of transistors are investigated under continuous branching of the current between channel and gate. It is shown that the current-noise and voltage-noise spectra at the transistor terminals contain an excess noise related to thermal excitation of plasma wave modes in the dielectric layer between the channel and gate. It is found that the set of modes of excited plasma waves can be governed by the external embedding circuits, thus violating a universal description of noise in terms of Norton and Thevenin noise generators

Carrier Current Line Systems Technologies in M2M Architecture for Wireless Communication

Directory of Open Access Journals (Sweden)

Hua-Ching Chen

2016-01-01

Full Text Available This paper investigates the Carrier Current Line Systems (CCLS technologies of Machine to Machine (M2M architecture which applied for mobile station coverage working with metro, high speed railway, and subway such as analysis for public transport of an indoor transition system. It is based on the theory and practical engineering principle which provide guidelines and formulas for link budget design to help designers fully control and analyze the single output power of uplink and downlink between Fiber Repeaters (FR and mobile station as well as base station. Finally, the results of this leakage cable system are successfully applied to indoor coverage design for metro rapid transit system which are easily installed cellular over fiber solutions for WCDMA/LTE access is becoming Ubiquitous Network to Internet of Thing (IOT real case hierarchy of telecommunication.

High pH mobile phase effects on silica-based reversed-phase high-performance liquid chromatographic columns

NARCIS (Netherlands)

Kirkland, J.J.; Straten, van M.A.; Claessens, H.A.

1995-01-01

Aqueous mobile phases above pH 8 often cause premature column failure, limiting the utility of silica-based columns for applications requiring high pH. Previous studies suggest that covalently bound silane ligands are hydrolyzed and removed by high-pH mobile phases. However, we found that the

Ultra high hole mobilities in a pure strained Ge quantum well

International Nuclear Information System (INIS)

Mironov, O.A.; Hassan, A.H.A.; Morris, R.J.H.; Dobbie, A.; Uhlarz, M.; Chrastina, D.; Hague, J.P.; Kiatgamolchai, S.; Beanland, R.; Gabani, S.; Berkutov, I.B.; Helm, M.; Drachenko, O.; Myronov, M.; Leadley, D.R.

2014-01-01

Hole mobilities at low and room temperature (RT) have been studied for a strained sGe/SiGe heterostructure using standard Van der Pauw resistivity and Hall effect measurements. The range of magnetic field and temperatures used were − 14 T < B < + 14 T and 1.5 K < T < 300 K respectively. Using maximum entropy-mobility spectrum analysis (ME-MSA) and Bryan's algorithm mobility spectrum (BAMS) analysis, a RT two dimensional hole gas drift mobility of (3.9 ± 0.4) × 10 3 cm 2 /V s was determined for a sheet density (p s ) 9.8 × 10 10 cm −2 (by ME-MSA) and (3.9 ± 0.2) × 10 3 cm 2 /V s for a sheet density (p s ) 5.9 × 10 10 cm −2 (by BAMS). - Highlights: • Pure strained Ge channel grown by reduced pressure chemical vapor deposition • Maximum entropy-mobility spectrum analysis • Bryan's algorithm mobility spectrum analysis • High room temperature hole drift mobility of (3.9 ± 0.4) × 10 3 cm 2 /V s • Extremely high hole mobility of 1.1 × 10 6 cm 2 /V s at 12 K

Rational In Silico Design of an Organic Semiconductor with Improved Electron Mobility.

Science.gov (United States)

Friederich, Pascal; Gómez, Verónica; Sprau, Christian; Meded, Velimir; Strunk, Timo; Jenne, Michael; Magri, Andrea; Symalla, Franz; Colsmann, Alexander; Ruben, Mario; Wenzel, Wolfgang

2017-11-01

Organic semiconductors find a wide range of applications, such as in organic light emitting diodes, organic solar cells, and organic field effect transistors. One of their most striking disadvantages in comparison to crystalline inorganic semiconductors is their low charge-carrier mobility, which manifests itself in major device constraints such as limited photoactive layer thicknesses. Trial-and-error attempts to increase charge-carrier mobility are impeded by the complex interplay of the molecular and electronic structure of the material with its morphology. Here, the viability of a multiscale simulation approach to rationally design materials with improved electron mobility is demonstrated. Starting from one of the most widely used electron conducting materials (Alq 3 ), novel organic semiconductors with tailored electronic properties are designed for which an improvement of the electron mobility by three orders of magnitude is predicted and experimentally confirmed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measuring Charge Carrier Diffusion in Coupled Colloidal Quantum Dot Solids

KAUST Repository

Zhitomirsky, David

2013-06-25

Colloidal quantum dots (CQDs) are attractive materials for inexpensive, room-temperature-, and solution-processed optoelectronic devices. A high carrier diffusion length is desirable for many CQD device applications. In this work we develop two new experimental methods to investigate charge carrier diffusion in coupled CQD solids under charge-neutral, i.e., undepleted, conditions. The methods take advantage of the quantum-size-effect tunability of our materials, utilizing a smaller-bandgap population of quantum dots as a reporter system. We develop analytical models of diffusion in 1D and 3D structures that allow direct extraction of diffusion length from convenient parametric plots and purely optical measurements. We measure several CQD solids fabricated using a number of distinct methods and having significantly different doping and surface ligand treatments. We find that CQD materials recently reported to achieve a certified power conversion efficiency of 7% with hybrid organic-inorganic passivation have a diffusion length of 80 ± 10 nm. The model further allows us to extract the lifetime, trap density, mobility, and diffusion coefficient independently in each material system. This work will facilitate further progress in extending the diffusion length, ultimately leading to high-quality CQD solid semiconducting materials and improved CQD optoelectronic devices, including CQD solar cells. © 2013 American Chemical Society.

Both Hemophilia Health Care Providers and Hemophilia A Carriers Report that Carriers have Excessive Bleeding

Science.gov (United States)

Paroskie, Allison; Oso, Olatunde; DeBaun, Michael R.; Sidonio, Robert F

2014-01-01

Introduction Hemophilia A, the result of reduced factor VIII (FVIII) activity, is an X-linked recessive bleeding disorder. Previous reports of Hemophilia A carriers suggest an increased bleeding tendency. Our objective was to determine the attitudes and understanding of the Hemophilia A carrier bleeding phenotype, and opinions regarding timing of carrier testing from the perspective of both medical providers and affected patients. Data from this survey was used as preliminary data for an ongoing prospective study. Material and Methods An electronic survey was distributed to physicians and nurses employed at Hemophilia Treatment Centers (HTC), and Hemophilia A carriers who were members of Hemophilia Federation of America. Questions focused on the clinical understanding of bleeding symptoms and management of Hemophilia A carriers, and the timing and intensity of carrier testing. Results Our survey indicates that 51% (36/51) of providers compared to 78% (36/46) of carriers believe that Hemophilia A carriers with normal FVIII activity have an increased bleeding tendency (pHemophilia A carriers report a high frequency of bleeding symptoms. Regarding carrier testing, 72% (50/69) of medical providers recommend testing after 14 years of age, conversely 65% (29/45) of Hemophilia A carriers prefer testing to be done prior to this age (pHemophilia A carriers self-report a higher frequency of bleeding than previously acknowledged, and have a preference for earlier testing to confirm carrier status. PMID:24309601

High mobility transparent conducting oxides for thin film solar cells

International Nuclear Information System (INIS)

Calnan, S.; Tiwari, A.N.

2010-01-01

A special class of transparent conducting oxides (TCO) with high mobility of > 65 cm 2 V -1 s -1 allows film resistivity in the low 10 -4 Ω cm range and a high transparency of > 80% over a wide spectrum, from 300 nm to beyond 1500 nm. This exceptional coincidence of desirable optical and electrical properties provides opportunities to improve the performance of opto-electronic devices and opens possibilities for new applications. Strategies to attain high mobility (HM) TCO materials as well as the current status of such materials based on indium and cadmium containing oxides are presented. Various concepts used to understand the underlying mechanisms for high mobility in HMTCO films are discussed. Examples of HMTCO layers used as transparent electrodes in thin film solar cells are used to illustrate possible improvements in solar cell performance. Finally, challenges and prospects for further development of HMTCO materials are discussed.

Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO3/SrTiO3 superlattices: coexistence of Auger recombination and single-carrier trapping

Directory of Open Access Journals (Sweden)

H. J. Harsan Ma

2015-06-01

Full Text Available We report emerging photoluminescence (PL of bilayer two-dimensional electron gases (2DEG in LaAlO3/SrTiO3 (LAO/STO systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.

Contention aware mobility prediction routing for intermittently connected mobile networks

KAUST Repository

Elwhishi, Ahmed; Ho, Pin-Han; Shihada, Basem

2013-01-01

This paper introduces a novel multi-copy routing protocol, called predict and forward (PF), for delay tolerant networks, which aims to explore the possibility of using mobile nodes as message carriers for end-to-end delivery of the messages. With PF, the message forwarding decision is made by manipulating the probability distribution of future inter-contact and contact durations based on the network status, including wireless link condition and nodal buffer availability. In particular, PF is based on the observations that the node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. We implemented the proposed protocol and compared it with a number of existing encounter-based routing approaches in terms of delivery delay, delivery ratio, and the number of transmissions required for message delivery. The simulation results show that PF outperforms all the counterpart multi-copy encounter-based routing protocols considered in the study.

Contention aware mobility prediction routing for intermittently connected mobile networks

KAUST Repository

Elwhishi, Ahmed

2013-04-26

This paper introduces a novel multi-copy routing protocol, called predict and forward (PF), for delay tolerant networks, which aims to explore the possibility of using mobile nodes as message carriers for end-to-end delivery of the messages. With PF, the message forwarding decision is made by manipulating the probability distribution of future inter-contact and contact durations based on the network status, including wireless link condition and nodal buffer availability. In particular, PF is based on the observations that the node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. We implemented the proposed protocol and compared it with a number of existing encounter-based routing approaches in terms of delivery delay, delivery ratio, and the number of transmissions required for message delivery. The simulation results show that PF outperforms all the counterpart multi-copy encounter-based routing protocols considered in the study.

High mobility solution-processed hybrid light emitting transistors

International Nuclear Information System (INIS)

Walker, Bright; Kim, Jin Young; Ullah, Mujeeb; Burn, Paul L.; Namdas, Ebinazar B.; Chae, Gil Jo; Cho, Shinuk; Seo, Jung Hwa

2014-01-01

We report the design, fabrication, and characterization of high-performance, solution-processed hybrid (inorganic-organic) light emitting transistors (HLETs). The devices employ a high-mobility, solution-processed cadmium sulfide layer as the switching and transport layer, with a conjugated polymer Super Yellow as an emissive material in non-planar source/drain transistor geometry. We demonstrate HLETs with electron mobilities of up to 19.5 cm 2 /V s, current on/off ratios of >10 7 , and external quantum efficiency of 10 −2 % at 2100 cd/m 2 . These combined optical and electrical performance exceed those reported to date for HLETs. Furthermore, we provide full analysis of charge injection, charge transport, and recombination mechanism of the HLETs. The high brightness coupled with a high on/off ratio and low-cost solution processing makes this type of hybrid device attractive from a manufacturing perspective

Recycling Gene Carrier with High Efficiency and Low Toxicity Mediated by L-Cystine-Bridged Bis(β-cyclodextrin)s

Science.gov (United States)

Zhang, Yu-Hui; Chen, Yong; Zhang, Ying-Ming; Yang, Yang; Chen, Jia-Tong; Liu, Yu

2014-12-01

Constructing safe and effective gene delivery carriers is becoming highly desirable for gene therapy. Herein, a series of supramolecular crosslinking system were prepared through host-guest binding of adamantyl-modified low molecular weight of polyethyleneimine with L-cystine-bridged bis(β-cyclodextrin)s and characterized by 1H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, flow cytometry and confocal fluorescence microscopy. The results showed that these nanometersized supramolecular crosslinking systems exhibited higher DNA transfection efficiencies and lower cytotoxicity than the commercial DNA carrier gold standard (25 kDa bPEI) for both normal cells and cancer cells, giving a very high DNA transfection efficiency up to 54% for 293T cells. Significantly, this type of supramolecular crosslinking system possesses a number of enzyme-responsive disulfide bonds, which can be cleaved by reductive enzyme to promote the DNA release but recovered by oxidative enzyme to make the carrier renewable. These results demonstrate that these supramolecular crosslinking systems can be used as promising gene carriers.

Interaction of a non-histone chromatin protein (high-mobility group protein 2) with DNA

International Nuclear Information System (INIS)

Goodwin, G.H.; Shooter, K.V.; Johns, E.W.

1975-01-01

The interaction with DNA of the calf thymus chromatin non-histone protein termed the high-mobility group protein 2 has been studied by sedimentation analysis in the ultracentrifuge and by measuring the binding of the 125 I-labelled protein to DNA. The results have been compared with those obtained previously by us [Eur. J. Biochem. (1974) 47, 263-270] for the interaction of high-mobility group protein 1 with DNA. Although the binding parameters are similar for these two proteins, high-mobility group protein 2 differs from high-mobility group protein 1 in that the former appears to change the shape of the DNA to a more compact form. The molecular weight of high-mobility group protein 2 has been determined by equilibrium sedimentation and a mean value of 26,000 was obtained. A low level of nuclease activity detected in one preparation of high-mobility group protein 2 has been investigated. (orig.) [de

Highly Mobile Students: Educational Problems and Possible Solutions. ERIC/CUE Digest, Number 73.

Science.gov (United States)

ERIC Clearinghouse on Urban Education, New York, NY.

The following two types of student mobility stand out as causing educational problems: (1) inner-city mobility, which is prompted largely by fluctuations in the job market; and (2) intra-city mobility, which is caused by upward mobility or by poverty and homelessness. Most research indicates that high mobility negatively affects student…

Measuring the local mobility of graphene on semiconductors

Science.gov (United States)

Zhong, Haijian; Liu, Zhenghui; Wang, Jianfeng; Pan, Anlian; Xu, Gengzhao; Xu, Ke

2018-04-01

Mobility is an important parameter to gauge the performance of graphene devices, which is usually measured by FET or Hall methods relying on the use of insulating substrates. However, these methods are not applicable for the case of graphene on semiconductors, because some current will inevitably cross their junctions and flow through the semiconductors except directly traversing the graphene surface. Here we demonstrate a method for measuring the local mobility of graphene on gallium nitrides combining Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (C-AFM). The carrier density related to Fermi level shifts in graphene can be acquired from KPFM. The local mobility of graphene is calculated from the carrier mean free path available from the effective contact area, which can be fitted from the local I-V curves in graphene/GaN junctions by C-AFM. Our method can be used to investigate an arbitrary region in graphene and also be applied to other semiconductor substrates and do not introduce damages. These results will benefit recent topical application researches for graphene integration in various semiconductor devices.

BEYOND THE WORK-LIFE BALANCE: FAMILY AND INTERNATIONAL MOBILITY OF THE HIGHLY SKILLED

Directory of Open Access Journals (Sweden)

Núria Vergés Bosch

2013-10-01

Full Text Available International mobility of the highly skilled has become one of the cornerstones of development in the current knowledge society. Correspondingly, highly skilled personnel are impelled to move abroad in order to improve their competences and build influential professional networks. Mobility implies some advantages involving personal, social and family opportunities when movers experience handicaps in their country of origin. For movers, mobility becomes a new challenge beyond the work-family balance, particularly for women who usually take on the lion’s share of childcare and domestic tasks within the family. The literature exploring the gender dimension in relation to international mobility points to complex outcomes. Firstly, women are taking on a more active role in international mobility processes, even when they have family. Secondly, family and international mobility are interrelated both for men and for women, although family could become a hindrance, particularly for women. Thirdly, international mobility and women’s career development may interfere with family formation or modify traditional family values. Finally, families moving abroad constitute a challenge for public policy, since they present a new area of problems. We aim to analyse the relationship between international mobility and family based on in-depth interviews from a purposive sample of highly skilled personnel in science and technology. The results of our research suggest that international mobility of the highly skilled has effects on the family and vice versa; however, while international mobility and family are compatible, measures and policies to reconcile them are still insufficient.

Enabling high-mobility, ambipolar charge-transport in a DPP-benzotriazole copolymer by side-chain engineering

DEFF Research Database (Denmark)

Gruber, Mathias; Jung, Seok-Heon; Schott, Sam

2015-01-01

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear...... side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers...

High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric.

Science.gov (United States)

Fujii, Mami N; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

2015-12-18

The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices.

An Architecture Offering Mobile Pollution Sensing with High Spatial Resolution

Directory of Open Access Journals (Sweden)

Oscar Alvear

2016-01-01

Full Text Available Mobile sensing is becoming the best option to monitor our environment due to its ease of use, high flexibility, and low price. In this paper, we present a mobile sensing architecture able to monitor different pollutants using low-end sensors. Although the proposed solution can be deployed everywhere, it becomes especially meaningful in crowded cities where pollution values are often high, being of great concern to both population and authorities. Our architecture is composed of three different modules: a mobile sensor for monitoring environment pollutants, an Android-based device for transferring the gathered data to a central server, and a central processing server for analyzing the pollution distribution. Moreover, we analyze different issues related to the monitoring process: (i filtering captured data to reduce the variability of consecutive measurements; (ii converting the sensor output to actual pollution levels; (iii reducing the temporal variations produced by mobile sensing process; and (iv applying interpolation techniques for creating detailed pollution maps. In addition, we study the best strategy to use mobile sensors by first determining the influence of sensor orientation on the captured values and then analyzing the influence of time and space sampling in the interpolation process.

Low intrinsic carrier density LSMO/Alq3/AlOx/Co organic spintronic devices

Science.gov (United States)

Riminucci, Alberto; Graziosi, Patrizio; Calbucci, Marco; Cecchini, Raimondo; Prezioso, Mirko; Borgatti, Francesco; Bergenti, Ilaria; Dediu, Valentin Alek

2018-04-01

The understanding of spin injection and transport in organic spintronic devices is still incomplete, with some experiments showing magnetoresistance and others not detecting it. We have investigated the transport properties of a large number of tris-(8-hydroxyquinoline)aluminum-based organic spintronic devices with an electrical resistance greater than 5 MΩ that did not show magnetoresistance. Their transport properties could be described satisfactorily by known models for organic semiconductors. At high voltages (>2 V), the results followed the model of space charge limited current with a Poole-Frenkel mobility. At low voltages (˜0.1 V), that are those at which the spin valve behavior is usually observed, the charge transport was modelled by nearest neighbor hopping in intra-gap impurity levels, with a charge carrier density of n0 = (1.44 ± 0.21) × 1015 cm-3 at room temperature. Such a low carrier density can explain why no magnetoresistance was observed.

Efficient photogeneration of charge carriers in silicon nanowires with a radial doping gradient

International Nuclear Information System (INIS)

Murthy, D H K; Houtepen, A J; Savenije, T J; Siebbeles, L D A; Xu, T; Nys, J P; Krzeminski, C; Grandidier, B; Stievenard, D; Chen, W H; Pareige, P; Jomard, F; Patriarche, G; Lebedev, O I

2011-01-01

by performing electrodeless time-resolved microwave conductivity measurements, the efficiency of charge carrier generation, their mobility, and the decay kinetics on photoexcitation were studied in arrays of Si nanowires grown by the vapor-liquid-solid mechanism. Large enhancements in the magnitude of the photoconductance and charge carrier lifetime are found depending on the incorporation of impurities during the growth. They are explained by the internal electric field that builds up, due to higher doped sidewalls, as revealed by detailed analysis of the nanowire morphology and chemical composition.

Mobile high-voltage switchboard. Variable and uncomplicated; Mobile Hochspannungsschaltanlage. Variabel und unkompliziert in der Anwendung

Energy Technology Data Exchange (ETDEWEB)

Albert, Andreas [Siemens AG, Erlangen (Germany). Sector Energy

2009-07-13

The mobile high-voltage switchboard ''REE-Movil 2'' for voltages up to 245 kV provides a complete and nearly autonomous switchboard in a container, a solution that has been available in the medium-voltage sector for some time already. It can be used whenever a quick replacement of a switchboard section or a temporary supplement to a switching substation is needed. The container is mounted on a trailer for maximum flexibility and mobility. (orig.)

High level bacterial contamination of secondary school students' mobile phones.

Science.gov (United States)

Kõljalg, Siiri; Mändar, Rando; Sõber, Tiina; Rööp, Tiiu; Mändar, Reet

2017-06-01

While contamination of mobile phones in the hospital has been found to be common in several studies, little information about bacterial abundance on phones used in the community is available. Our aim was to quantitatively determine the bacterial contamination of secondary school students' mobile phones. Altogether 27 mobile phones were studied. The contact plate method and microbial identification using MALDI-TOF mass spectrometer were used for culture studies. Quantitative PCR reaction for detection of universal 16S rRNA, Enterococcus faecalis 16S rRNA and Escherichia coli allantoin permease were performed, and the presence of tetracycline ( tet A, tet B, tet M), erythromycin ( erm B) and sulphonamide ( sul 1) resistance genes was assessed. We found a high median bacterial count on secondary school students' mobile phones (10.5 CFU/cm 2 ) and a median of 17,032 bacterial 16S rRNA gene copies per phone. Potentially pathogenic microbes ( Staphylococcus aureus , Acinetobacter spp. , Pseudomonas spp., Bacillus cereus and Neisseria flavescens ) were found among dominant microbes more often on phones with higher percentage of E. faecalis in total bacterial 16S rRNA. No differences in contamination level or dominating bacterial species between phone owner's gender and between phone types (touch screen/keypad) were found. No antibiotic resistance genes were detected on mobile phone surfaces. Quantitative study methods revealed high level bacterial contamination of secondary school students' mobile phones.

LIQUIFIED NATURAL GAS (LNG CARRIERS

Directory of Open Access Journals (Sweden)

Daniel Posavec

2010-12-01

Full Text Available Modern liquefied natural gas carriers are double-bottom ships classified according to the type of LNG tank. The tanks are specially designed to store natural gas cooled to -161°C, the boiling point of methane. Since LNG is highly flammable, special care must be taken when designing and operating the ship. The development of LNG carriers has begun in the middle of the twentieth century. LNG carrier storage space has gradually grown to the current maximum of 260000 m3. There are more than 300 LNG carriers currently in operation (the paper is published in Croatian.

High mobility ZnO nanowires for terahertz detection applications

International Nuclear Information System (INIS)

Liu, Huiqiang; Peng, Rufang; Chu, Shijin; Chu, Sheng

2014-01-01

An oxide nanowire material was utilized for terahertz detection purpose. High quality ZnO nanowires were synthesized and field-effect transistors were fabricated. Electrical transport measurements demonstrated the nanowire with good transfer characteristics and fairly high electron mobility. It is shown that ZnO nanowires can be used as building blocks for the realization of terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave (∼0.3 THz) induced photovoltages were obtained at room temperature with varying incidence intensities. Further analysis showed that the terahertz photoresponse is closely related to the high electron mobility of the ZnO nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.

Improved Mobility and Bias Stability of Thin Film Transistors Using the Double-Layer a-InGaZnO/a-InGaZnO:N Channel.

Science.gov (United States)

Yu, H; Zhang, L; Li, X H; Xu, H Y; Liu, Y C

2016-04-01

The amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) were demonstrated based on a double-layer channel structure, where the channel is composed of an ultrathin nitro-genated a-IGZO (a-IGZO:N) layer and an undoped a-IGZO layer. The double-layer channel device showed higher saturation mobility and lower threshold-voltage shift (5.74 cm2/Vs, 2.6 V) compared to its single-layer counterpart (0.17 cm2/Vs, 7.23 V). The improvement can be attributed to three aspects: (1) improved carrier transport properties of the channel by the a-IGZO:N layer with high carrier mobility and the a-IGZO layer with high carrier concentration, (2) reduced interfacial trap density between the active channel and the gate insulator, and (3) higher surface flatness of the double-layer channel. Our study reveals key insights into double-layer channel, involving selecting more suitable electrical property for back-channel layer and more suitable interface modification for active layer. Meanwhile, room temperature fabrication amorphous TFTs offer certain advantages on better flexibility and higher uniformity over a large area.

Mobile Communication, Public Participation and E-Governance in China

DEFF Research Database (Denmark)

Liu, Jun; Zhao, Hui

2010-01-01

China has become the biggest mobile communication carrier in the world since 2001. Advanced technologies create a communication revolution, and the individual, through the advent of mobile media, has become an active participant in this process. This study investigates the mobile phone’s impact...... upon the developments of public participation, social inclusion and citizenship through the case study of Xiamen PX demonstration. In terms of local environmental activism, the Xiamen residents shared information with the help of wireless communication about the alleged misdeeds of party officials...

Performance Analysis of GaN Capping Layer Thickness on GaN/AlGaN/GaN High Electron Mobility Transistors.

Science.gov (United States)

Sharma, N; Periasamy, C; Chaturvedi, N

2018-07-01

In this paper, we present an investigation of the impact of GaN capping layer and AlGaN layer thickness on the two-dimensional (2D)-electron mobility and the carrier concentration which was formed close to the AlGaN/GaN buffer layer for Al0.25Ga0.75N/GaN and GaN/Al0.25Ga0.75N/GaN heterostructures deposited on sapphire substrates. The results of our analysis clearly indicate that expanding the GaN capping layer thickness from 1 nm to 100 nm prompts an increment in the electron concentration at hetero interface. As consequence of which drain current was additionally increments with GaN cap layer thicknesses, and eventually saturates at approximately 1.85 A/mm for capping layer thickness greater than 40 nm. Interestingly, for the same structure, the 2D-electron mobility, decrease monotonically with GaN capping layer thickness, and saturate at approximately 830 cm2/Vs for capping layer thickness greater than 50 nm. A device with a GaN cap layer didn't exhibit gate leakage current. Furthermore, it was observed that the carrier concentration was first decrease 1.03 × 1019/cm3 to 6.65 × 1018/cm3 with AlGaN Layer thickness from 5 to 10 nm and after that it increases with the AlGaN layer thickness from 10 to 30 nm. The same trend was followed for electric field distributions. Electron mobility decreases monotonically with AlGaN layer thickness. Highest electron mobility 1354 cm2/Vs were recorded for the AlGaN layer thickness of 5 nm. Results obtained are in good agreement with published experimental data.

High-skilled labour mobility in Europe before and after the 2004 enlargement.

Science.gov (United States)

Petersen, Alexander M; Puliga, Michelangelo

2017-03-01

The extent to which international high-skilled mobility channels are forming is a question of great importance in an increasingly global knowledge-based economy. One factor facilitating the growth of high-skilled labour markets is the standardization of certifiable degrees meriting international recognition. Within this context, we analysed an extensive high-skilled mobility database comprising roughly 382 000 individuals from five broad profession groups (Medical, Education, Technical, Science & Engineering and Business & Legal) over the period 1997-2014, using the 13-country expansion of the European Union (EU) to provide insight into labour market integration. We compare the periods before and after the 2004 enlargement, showing the emergence of a new east-west migration channel between the 13 mostly eastern EU entrants (E) and the rest of the western European countries (W). Indeed, we observe a net directional loss of human capital from E → W, representing 29% of the total mobility after 2004. Nevertheless, the counter-migration from W → E is 7% of the total mobility over the same period, signalling the emergence of brain circulation within the EU. Our analysis of the country-country mobility networks and the country-profession bipartite networks provides timely quantitative evidence for the convergent integration of the EU, and highlights the central role of the UK and Germany as high-skilled labour hubs. We conclude with two data-driven models to explore the structural dynamics of the mobility networks. First, we develop a reconfiguration model to explore the potential ramifications of Brexit and the degree to which redirection of high-skilled labourers away from the UK may impact the integration of the rest of the European mobility network. Second, we use a panel regression model to explain empirical high-skilled mobility rates in terms of various economic 'push-pull' factors, the results of which show that government expenditure on education, per capita

Inert carriers for column extraction chromatography

International Nuclear Information System (INIS)

Katykhin, G.S.

1978-01-01

Inert carriers used in column extraction chromatography are reviewed. Such carriers are devided into two large groups: hydrophilic carriers which possess high surface energy and are well wetted only with strongly polar liquids (kieselguhrs, silica gels, glasses, cellulose, Al 2 O 3 ) and water-repellent carriers which possess low surface energy and are well wetted with various organic solvents (polyethylene, polytetrafluorethylene polytrifluorochlorethylene). Properties of various carriers are presented: structure, chemical and radiation stability, adsorption properties, extracting agent capacity. The effect of structure and sizes of particles on the efficiency of chromatography columns is considered. Ways of immovable phase deposition on the carrier and the latter's regeneration. Peculiarities of column packing for preparative and continuous chromatography are discussed

Hybrid Tunable Wideband Single Feed Antenna Element for Smartphones supporting Carrier Aggregation

DEFF Research Database (Denmark)

Stanev, Simon Peter; Tatomirescu, Alexandru

2016-01-01

This paper presents a single feed antenna with a dual branch matching circuit combined with a 3dB microstrip power divider to support the carrier aggregation in LTE advanced mobile handsets. By the use of the matching circuits, an independent and versatile broadband antenna is achieved. Hence, th...

Sustained Pulmonary Delivery of a Water-Soluble Antibiotic Without Encapsulating Carriers.

Science.gov (United States)

Ong, Winston; Nowak, Pawel; Cu, Yen; Schopf, Lisa; Bourassa, James; Enlow, Elizabeth; Moskowitz, Samuel M; Chen, Hongming

2016-03-01

Traditional polymeric nanoparticle formulations for prolonged local action during inhalation therapy are highly susceptible to muco-ciliary clearance. In addition, polymeric carriers are typically administered in high doses due to finite drug loading. For toxicological reasons, these carriers and their degradation byproducts are undesirable for inhalation therapy, particularly for chronic use, due to potential lung accumulation. We synthesized a novel, insoluble prodrug (MRPD) of a time-dependent β-lactam, meropenem, and formulated MRPD into mucus-penetrating crystals (MRPD-MPCs). After characterizing their mucus mobility (in vitro) and stability, we evaluated the lung pharmacokinetics of intratracheally-instilled MRPD-MPCs and a meropenem solution in guinea pigs. Meropenem levels rapidly declined in the lungs of guinea pigs receiving meropenem solution compared to those given MRPD-MPCs. At 9 h after dosing, drug levels in the lungs of animals that received meropenem solution dropped to 12 ng/mL, whereas those that received MRPD-MPCs maintained an average drug level of ≥1,065 ng/mL over a 12-h period. This work demonstrated that the combination of prodrug chemistry and mucus-penetrating platform created nanoparticles that produced sustained levels of meropenem in guinea pig lungs. This strategy represents a novel approach for sustained local drug delivery to the lung without using encapsulating matrices.

Low-temperature mobility measurements on CMOS devices

International Nuclear Information System (INIS)

Hairpetian, A.; Gitlin, D.; Viswanathan, C.R.

1989-01-01

The surface channel mobility of carriers in eta- and rho-MOS transistors fabricated in a CMOS process was accurately determined at low temperatures down to 5 Κ. The mobility was obtained by an accurate measurement of the inversion charge density using a split C-V technique and the conductance at low drain voltages. The split C-V technique was validated at all temperatures using a one-dimensional Poisson solver (MOSCAP), which was modified for low-temperature application. The mobility dependence on the perpendicular electric field for different substrate bias values appears to have different temperature dependence for eta- and rho-channel devices. The electron mobility increases with a decrease in temperature at all gate voltages. On the other hand, the hole mobility exhibits a different temperature behavior depending upon whether the gate voltage corresponds to strong inversion or is near threshold

A high resolution EELS study of free-carrier variations in H2+/H+ bombarded (100)GaAs

International Nuclear Information System (INIS)

Dubois, L.H.; Schwartz, G.P.

1984-01-01

High resolution electron energy loss spectroscopy (EELS) has been used to examine whether thermal recovery of the near-surface free-carrier concentration in Te-doped (100) GaAs is accomplished following low energy (250--1500 eV) hydrogen ion bombardment. For hydrogen ion impact energies below 500 eV, the nominal bulk free-carrier density is recovered by annealing at 725 K for 2 h. For comparable ion doses, the net free-carrier concentration decreases monotonically at higher impact energies under similar annealing conditions. The threshold for damage retention occurs close to the value of transmitted energy which is necessary to create either a Ga or an As interstitial point defect

Ultimate response time of high electron mobility transistors

International Nuclear Information System (INIS)

Rudin, Sergey; Rupper, Greg; Shur, Michael

2015-01-01

We present theoretical studies of the response time of the two-dimensional gated electron gas to femtosecond pulses. Our hydrodynamic simulations show that the device response to a short pulse or a step-function signal is either smooth or oscillating time-decay at low and high mobility, μ, values, respectively. At small gate voltage swings, U 0  = U g  − U th , where U g is the gate voltage and U th is the threshold voltage, such that μU 0 /L < v s , where L is the channel length and v s is the effective electron saturation velocity, the decay time in the low mobility samples is on the order of L 2 /(μU 0 ), in agreement with the analytical drift model. However, the decay is preceded by a delay time on the order of L/s, where s is the plasma wave velocity. This delay is the ballistic transport signature in collision-dominated devices, which becomes important during very short time periods. In the high mobility devices, the period of the decaying oscillations is on the order of the plasma wave velocity transit time. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet the requirements for applications as terahertz detectors, mixers, delay lines, and phase shifters in ultra high-speed wireless communication circuits

Vectorization of agrochemicals: amino acid carriers are more efficient than sugar carriers to translocate phenylpyrrole conjugates in the Ricinus system.

Science.gov (United States)

Wu, Hanxiang; Marhadour, Sophie; Lei, Zhi-Wei; Yang, Wen; Marivingt-Mounir, Cécile; Bonnemain, Jean-Louis; Chollet, Jean-François

2018-05-01

Producing quality food in sufficient quantity while using less agrochemical inputs will be one of the great challenges of the twenty-first century. One way of achieving this goal is to greatly reduce the doses of plant protection compounds by improving the targeting of pests to eradicate. Therefore, we developed a vectorization strategy to confer phloem mobility to fenpiclonil, a contact fungicide from the phenylpyrrole family used as a model molecule. It consists in coupling the antifungal compound to an amino acid or a sugar, so that the resulting conjugates are handled by active nutrient transport systems. The method of click chemistry was used to synthesize three conjugates combining fenpiclonil to glucose or glutamic acid with a spacer containing a triazole ring. Systemicity tests with the Ricinus model have shown that the amino acid promoiety was clearly more favorable to phloem mobility than that of glucose. In addition, the transport of the amino acid conjugate is carrier mediated since the derivative of the L series was about five times more concentrated in the phloem sap than its counterpart of the D series. The systemicity of the L-derivative is pH dependent and almost completely inhibited by the protonophore carbonyl cyanide 3-chlorophenylhydrazone (CCCP). These data suggest that the phloem transport of the L-derivative is governed by a stereospecific amino acid carrier system energized by the proton motive force.

Investigation of Doppler Effects on high mobility OFDM-MIMO systems with the support of High Altitude Platforms (HAPs)

Science.gov (United States)

Mohammed, H. A.; Sibley, M. J. N.; Mather, P. J.

2012-05-01

The merging of Orthogonal Frequency Division Multiplexing (OFDM) with Multiple-input multiple-output (MIMO) is a promising mobile air interface solution for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. This paper details the design of a highly robust and efficient OFDM-MIMO system to support permanent accessibility and higher data rates to users moving at high speeds, such as users travelling on trains. It has high relevance for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. The paper begins with a comprehensive literature review focused on both technologies. This is followed by the modelling of the OFDM-MIMO physical layer based on Simulink/Matlab that takes into consideration high vehicular mobility. Then the entire system is simulated and analysed under different encoding and channel estimation algorithms. The use of High Altitude Platform system (HAPs) technology is considered and analysed.

Investigation of Doppler Effects on high mobility OFDM-MIMO systems with the support of High Altitude Platforms (HAPs)

International Nuclear Information System (INIS)

Mohammed, H A; Sibley, M J N; Mather, P J

2012-01-01

The merging of Orthogonal Frequency Division Multiplexing (OFDM) with Multiple-input multiple-output (MIMO) is a promising mobile air interface solution for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. This paper details the design of a highly robust and efficient OFDM-MIMO system to support permanent accessibility and higher data rates to users moving at high speeds, such as users travelling on trains. It has high relevance for next generation wireless local area networks (WLANs) and 4G mobile cellular wireless systems. The paper begins with a comprehensive literature review focused on both technologies. This is followed by the modelling of the OFDM-MIMO physical layer based on Simulink/Matlab that takes into consideration high vehicular mobility. Then the entire system is simulated and analysed under different encoding and channel estimation algorithms. The use of High Altitude Platform system (HAPs) technology is considered and analysed.

First-principles calculations of mobility

Science.gov (United States)

Krishnaswamy, Karthik

First-principles calculations can be a powerful predictive tool for studying, modeling and understanding the fundamental scattering mechanisms impacting carrier transport in materials. In the past, calculations have provided important qualitative insights, but numerical accuracy has been limited due to computational challenges. In this talk, we will discuss some of the challenges involved in calculating electron-phonon scattering and carrier mobility, and outline approaches to overcome them. Topics will include the limitations of models for electron-phonon interaction, the importance of grid sampling, and the use of Gaussian smearing to replace energy-conserving delta functions. Using prototypical examples of oxides that are of technological importance-SrTiO3, BaSnO3, Ga2O3, and WO3-we will demonstrate computational approaches to overcome these challenges and improve the accuracy. One approach that leads to a distinct improvement in the accuracy is the use of analytic functions for the band dispersion, which allows for an exact solution of the energy-conserving delta function. For select cases, we also discuss direct quantitative comparisons with experimental results. The computational approaches and methodologies discussed in the talk are general and applicable to other materials, and greatly improve the numerical accuracy of the calculated transport properties, such as carrier mobility, conductivity and Seebeck coefficient. This work was performed in collaboration with B. Himmetoglu, Y. Kang, W. Wang, A. Janotti and C. G. Van de Walle, and supported by the LEAST Center, the ONR EXEDE MURI, and NSF.

Carbon: Hydrogen carrier or disappearing skeleton?

International Nuclear Information System (INIS)

De Jong, K.P.; Van Wechem, H.M.H.

1994-01-01

The use of liquid hydrocarbons as energy carriers implies the use of carbon as a carrier for hydrogen to facilitate hydrogen transport and storage. The current trend for liquid energy carriers used in the transport sector is to maximize the load of hydrogen on the carbon carrier. The recently developed Shell Middle Distillate Hydrogenation process for the manufacture of high quality diesel from aromatic refinery streams fits this picture. In the future, the hydrogen required to raise the product H/C ratio will be increasingly produced via gasification of large amounts of heavy residues. In the light of the strong preference towards using liquid fuels in the transport sector, the Shell Middle Distillate Synthesis process to convert natural gas into diesel of very high quality is discussed. Finally, a few comments on the use of hydrogen without a carbon carrier are made. Long lead times and the likelihood of producing the 'first' hydrogen from fossil fuel are highlighted. 13 figs., 6 tabs., 5 refs

Optimizations in Heterogeneous Mobile Networks

DEFF Research Database (Denmark)

Popovska Avramova, Andrijana

nodes. The independent control of the user’s transmit power at each node may cause degradation of the overall performance. In this line, a dedicated study of power distribution among the carriers is performed. An optimization of the power allocation is proposed and evaluated. The results show...... significant performance improvement to the achieved user throughput in low as well as in high loads in the cell. The flow control of the data between the nodes is another challenge for effective aggregation of the resources in case of dual connectivity. As such, this thesis discusses the challenges...... with the densification of the base stations, bring into a very complex network management and operation control for the mobile operators. Furthermore, the need to provide always best connection and service with high quality demands for a joint overall network resource management. This thesis addresses this challenge...

Residual carrier density in GaSb grown on Si substrates

International Nuclear Information System (INIS)

Akahane, Kouichi; Yamamoto, Naokatsu; Gozu, Shin-ichiro; Ueta, Akio; Ohtani, Naoki

2006-01-01

The relationships between the densities of residual carriers and those of dislocation in GaSb films grown on Si substrates were investigated. Dislocation density was evaluated by cross-sectional transmission electron microscopy (TEM). The TEM images indicated that the dislocation density after a 5-μm-thick GaSb film was grown was below 1 x 10 8 /cm 2 although the density near the interface between the Si substrate and the GaSb film was about 3 x 10 9 /cm 2 . Forming a dislocation loop by growing a thick GaSb layer may decrease the dislocation density. The density and mobility of the residual carrier were investigated by Hall measurement using the van der Pauw method. The residual carriers in GaSb grown on Si substrates were holes, and their densities decreased significantly from 4.2 x 10 18 to 1.4 x 10 17 /cm 3 as GaSb thickness was increased from 500 to 5500 nm

Single Carrier Cyclic Prefix-Assisted CDMA System with Frequency Domain Equalization for High Data Rate Transmission

Directory of Open Access Journals (Sweden)

Madhukumar A. S.

2004-01-01

Full Text Available Multiple-access interference and interfinger interference limit the capacity of conventional single-carrier DS-CDMA systems. Even though multicarrier CDMA posses the advantages of conventional CDMA and OFDM, it suffers from two major implementation difficulties such as peak-to-average power ratio and high sensitivity to frequency offset and RF phase noise. A novel approach based on single-carrier cyclic prefix-assisted CDMA has been proposed to overcome the disadvantages of single-carrier CDMA and multicarrier modulation. The usefulness of the proposed approach for high-speed packet access with simplified channel estimation procedures are investigated in this paper. The paper also proposes a data-dependent pilot structure for the downlink transmission of the proposed system for enhancing pilot-assisted channel estimation in frequency domain. The performance of the proposed pilot structure is compared against the data-independent common pilot structure. The proposed system is extensively simulated for different channel parameters with different channel estimation and equalization methods and the results are compared against conventional multicarrier CDMA systems with identical system specifications.

Charge Carrier Transport Properties of Vacuum Evaporated Anthrylvinylbenzene Thin Films

Directory of Open Access Journals (Sweden)

Haikel HRICHI

2014-05-01

Full Text Available The charge carrier conduction processes and dielectric properties of two new materials based on anthracene core structure, 1-(9 anthrylvinyl-4-benzyloxybenzene (AVB and 1,4- bis(9-anthrylvinylbenzene (AV2B diodes have been investigated using dc current density–voltage (J–V and AC impedance spectroscopy (100 Hz–10 MHz. The DC electrical properties of ITO/anthracene derivative /Al device showing an ohmic behavior at low voltages and switches to space charge limited current (SCLC conduction with exponential trap distribution at higher voltages. The best performance device was achieved from ITO/AVB/Al structure showing the high charge carrier mobility which has also been evaluated from SCLC as 6.55´10-6 cm/Vs. According to the impedance spectroscopy results the structures were modeled by equivalent circuit designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The evolution of the electrical parameters with frequency and bias voltage of these anthracene-based systems has been discussed. The conductivity s(w evolution with frequency and bias voltage was studied for ITO/anthracene derivatives/Al devices. The dc conductivity sdc for these devices has been determined. The ac conductivity sac showed a variation in angular frequency as A.ws with a critical exponent s< 1 suggesting a hopping conduction mechanism at high frequency.

Two dimensional numerical simulations of carrier dynamics during time-resolved photoluminescence decays in two-photon microscopy measurements in semiconductors

International Nuclear Information System (INIS)

Kanevce, Ana; Kuciauskas, Darius; Levi, Dean H.; Johnston, Steven W.; Allende Motz, Alyssa M.

2015-01-01

We use two-dimensional numerical simulations to analyze high spatial resolution time-resolved spectroscopy data. This analysis is applied to two-photon excitation time-resolved photoluminescence (2PE-TRPL) but is broadly applicable to all microscopic time-resolved techniques. By solving time-dependent drift-diffusion equations, we gain insight into carrier dynamics and transport characteristics. Accurate understanding of measurement results establishes the limits and potential of the measurement and enhances its value as a characterization method. Diffusion of carriers outside of the collection volume can have a significant impact on the measured decay but can also provide an estimate of carrier mobility as well as lifetime. In addition to material parameters, the experimental conditions, such as spot size and injection level, can impact the measurement results. Although small spot size provides better resolution, it also increases the impact of diffusion on the decay; if the spot size is much smaller than the diffusion length, it impacts the entire decay. By reproducing experimental 2PE-TRPL decays, the simulations determine the bulk carrier lifetime from the data. The analysis is applied to single-crystal and heteroepitaxial CdTe, material important for solar cells, but it is also applicable to other semiconductors where carrier diffusion from the excitation volume could affect experimental measurements

Demonstration of InAlN/AlGaN high electron mobility transistors with an enhanced breakdown voltage by pulsed metal organic chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Xue, JunShuai, E-mail: junshuaixue@hotmail.com; Zhang, JinCheng; Hao, Yue [Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China)

2016-01-04

In this work, InAlN/AlGaN heterostructures employing wider bandgap AlGaN instead of conventional GaN channel were grown on sapphire substrate by pulsed metal organic chemical vapor deposition, where the nominal Al composition in InAlN barrier and AlGaN channel were chosen to be 83% and 5%, respectively, to achieve close lattice-matched condition. An electron mobility of 511 cm{sup 2}/V s along with a sheet carrier density of 1.88 × 10{sup 13 }cm{sup −2} were revealed in the prepared heterostructures, both of which were lower compared with lattice-matched InAlN/GaN due to increased intrinsic alloy disorder scattering resulting from AlGaN channel and compressively piezoelectric polarization in barrier, respectively. While the high electron mobility transistor (HEMT) processed on these structures not only exhibited a sufficiently high drain output current density of 854 mA/mm but also demonstrated a significantly enhanced breakdown voltage of 87 V, which is twice higher than that of reported InAlN/GaN HEMT with the same device dimension, potential characteristics for high-voltage operation of GaN-based electronic devices.

The fabrication of a back-gated high electron mobility transistor - a novel approach using MBE regrowth on an in situ ion beam patterned epilayer

International Nuclear Information System (INIS)

Linfield, E.H.; Jones, G.A.C.; Ritchie, D.A.; Thompson, J.H.

1993-01-01

A new technique for the fabrication of GaAs/AlGaAs back-gated high electron mobility transistors (HEMTs) is described in this paper. First we demonstrate that a dose of > 2 x 10 13 cm -2 Ga ions at an energy of 10 keV can be used to damage a 67 nm n + GaAs layer, rendering the implanted regions non-conducting. After implantation the epilayer has a 4 K sheet resistivity which is increased by a factor of ∼ 10 7 when compared with the original unimplanted value. This isolation procedure is then used to form a patterned back-gated HEMT by MBE regrowth on top of an in situ ion-implanted n + GaAs layer. The resulting structure is designed so that the back gate is rendered highly resistive under the regions where the ohmic contacts to the two-dimensional electron gas (2DEG) are formed, thus making shallow ohmic contacts unnecessary. The results obtained characteristic of a high-quality 2DEG with mobility limited by remote ionized impurity scattering. This technique can therefore be used as a means of controlling the 2DEG carrier concentration, whilst leaving the surface of the HEMT structure free for conventional lithographic processing. (Author)

Carbon nanotube transistor based high-frequency electronics

Science.gov (United States)

Schroter, Michael

At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

Capacity planning for Carrier Ethernet LTE backhaul networks

DEFF Research Database (Denmark)

Checko, Aleksandra; Ellegaard, Lars; Berger, Michael Stübert

2012-01-01

With the introduction of LTE networks operators need to plan a new, IP-based mobile backhaul. In this paper, we provide recommendation on dimensioning LTE backhaul networks links using three methods: delay-, dimensioning formula- and overbooking factor-based. Results are obtained from OPNET simul...... and verified. Simulation in this work proves that Carrier Ethernet, one of the candidate technologies for mobile backhaul, protects the network from users that want to flood the network with their data and manages to keep the delay experienced by other users low....... simulations with traffic model based on traffic forecast for 2015. A delay-based approach gives recommended bandwidth for expected number of users. A dimensioning formula is proposed to calculate link bandwidth when mean value of aggregated traffic in the network is known. An overbooking factor is calculated...

Indolo-naphthyridine-6,13-dione Thiophene Building Block for Conjugated Polymer Electronics: Molecular Origin of Ultrahigh n-Type Mobility

KAUST Repository

Fallon, Kealan J.

2016-10-18

Herein, we present the synthesis and characterization of four conjugated polymers containing a novel chromophore for organic electronics based on an indigoid structure. These polymers exhibit extremely small band gaps of ∼1.2 eV, impressive crystallinity, and extremely high n-type mobility exceeding 3 cm V s. The n-type charge carrier mobility can be correlated with the remarkably high crystallinity along the polymer backbone having a correlation length in excess of 20 nm. Theoretical analysis reveals that the novel polymers have highly rigid nonplanar geometries demonstrating that backbone planarity is not a prerequisite for either narrow band gap materials or ultrahigh mobilities. Furthermore, the variation in backbone crystallinity is dependent on the choice of comonomer. OPV device efficiencies up to 4.1% and charge photogeneration up to 1000 nm are demonstrated, highlighting the potential of this novel chromophore class in high-performance organic electronics.

Indolo-naphthyridine-6,13-dione Thiophene Building Block for Conjugated Polymer Electronics: Molecular Origin of Ultrahigh n-Type Mobility

KAUST Repository

Fallon, Kealan J.; Wijeyasinghe, Nilushi; Manley, Eric F.; Dimitrov, Stoichko D.; Yousaf, Syeda A.; Ashraf, Raja S.; Duffy, Warren; Guilbert, Anne A. Y.; Freeman, David M. E.; Al-Hashimi, Mohammed; Nelson, Jenny; Durrant, James R.; Chen, Lin X.; McCulloch, Iain; Marks, Tobin J.; Clarke, Tracey M.; Anthopoulos, Thomas D.; Bronstein, Hugo

2016-01-01

Herein, we present the synthesis and characterization of four conjugated polymers containing a novel chromophore for organic electronics based on an indigoid structure. These polymers exhibit extremely small band gaps of ∼1.2 eV, impressive crystallinity, and extremely high n-type mobility exceeding 3 cm V s. The n-type charge carrier mobility can be correlated with the remarkably high crystallinity along the polymer backbone having a correlation length in excess of 20 nm. Theoretical analysis reveals that the novel polymers have highly rigid nonplanar geometries demonstrating that backbone planarity is not a prerequisite for either narrow band gap materials or ultrahigh mobilities. Furthermore, the variation in backbone crystallinity is dependent on the choice of comonomer. OPV device efficiencies up to 4.1% and charge photogeneration up to 1000 nm are demonstrated, highlighting the potential of this novel chromophore class in high-performance organic electronics.

Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

KAUST Repository

Shi, Dong

2016-04-15

We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD’s paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD’s intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.

Doping dependence and anisotropy of minority electron mobility in molecular beam epitaxy-grown p type GaInP

Energy Technology Data Exchange (ETDEWEB)

Haegel, N. M.; Christian, T.; Norman, A. G.; Mascarenhas, A. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Scandrett, C. [Naval Postgraduate School, Monterey, California 93943 (United States); Misra, Pranob; Liu, Ting; Sukiasyan, Arsen; Pickett, Evan; Yuen, Homan [Solar Junction, Inc., San Jose, California 95131 (United States)

2014-11-17

Direct imaging of minority electron transport via the spatially resolved recombination luminescence signature has been used to determine carrier diffusion lengths in GaInP as a function of doping. Minority electron mobility values are determined by performing time resolved photoluminescence measurements of carrier lifetime on the same samples. Values at 300 K vary from ∼2000 to 400 cm{sup 2}/V s and decrease with increasing doping. Anisotropic diffusion lengths and strongly polarized photoluminescence are observed, resulting from lateral composition modulation along the [110] direction. We report anisotropic mobility values associated with carrier transport parallel and perpendicular to the modulation direction.

LIQUIFIED NATURAL GAS (LNG) CARRIERS

OpenAIRE

Daniel Posavec; Katarina Simon; Matija Malnar

2010-01-01

Modern liquefied natural gas carriers are double-bottom ships classified according to the type of LNG tank. The tanks are specially designed to store natural gas cooled to -161°C, the boiling point of methane. Since LNG is highly flammable, special care must be taken when designing and operating the ship. The development of LNG carriers has begun in the middle of the twentieth century. LNG carrier storage space has gradually grown to the current maximum of 260000 m3. There are more than 300 L...

The role of molecular mobility in the transfer of charge generated by ionizing radiation in polymers

International Nuclear Information System (INIS)

Khatinov, S.A.; Edrisov, K.M.; Turdybekov, K.M.; Milinchuk, V.K.

1995-01-01

The dependence of radiation-induced electrical conductivity on the irradiation time and temperature was studied for a number of polymers. The character of variation of radiation-induced conductivity with time and temperature correlates with the physical state of a polymer. Defreezing of the segmental mobility in the region of α-relaxation transition leads to a sharp change in radiation-induced conductivity, and the appearance of peaks in the kinetic curves and break points on the Arrhenius plots in conductivity versus temperature coordinates. Molecular mobility plays a determining role in the transfer of charge carriers generated by radiation. This conclusion agrees with the data on the carrier mobility obtained by the time-of-flight methods. 24 refs., 8 figs

Highly efficient low color temperature organic LED using blend carrier modulation layer

Science.gov (United States)

Hsieh, Yao-Ching; Chen, Szu-Hao; Shen, Shih-Ming; Wang, Ching-Chiun; Chen, Chien-Chih; Jou, Jwo-Huei

2012-10-01

Color temperature (CT) of light has great effect on human physiology and psychology, and low CT light, minimizing melatonin suppression and decreasing the risk of breast, colorectal, and prostate cancer. We demonstrates the incorporation of a blend carrier modulation interlayer (CML) between emissive layers to improve the device performance of low CT organic light emitting diodes, which exhibits an external quantum efficiency of 22.7% and 36 lm W-1 (54 cd A-1) with 1880 K at 100 cd m-2, or 20.8% and 29 lm W-1 (50 cd A-1) with 1940 K at 1000 cd m-2. The result shows a CT much lower than that of incandescent bulbs, which is 2500 K with 15 lmW-1 efficiency, and even as low as that of candles, which is 2000 K with 0.1 lmW-1. The high efficiency of the proposed device may be attributed to its CML, which helps effectively distribute the entering carriers into the available recombination zones.

The indicating FTA elute cartridge a solid sample carrier to detect high-risk HPV and high-grade cervical lesions

NARCIS (Netherlands)

Bie, R.P. de; Schmeink, C.E.; Bakkers, J.M.J.E.; Snijders, P.J.L.M.; Quint, W.G.V.; Massuger, L.F.A.G.; Bekkers, R.L.M.; Melchers, W.J.G.

2011-01-01

The clinically validated high-risk human papillomavirus (hrHPV) Hybrid Capture 2 (HC2) and GP5+/6+-PCR assays were analyzed on an Indicating FTA Elute cartridge (FTA cartridge). The FTA cartridge is a solid dry carrier that allows safe transport of cervical samples. FTA cartridge samples were

Mobile cosmetics advisor: an imaging based mobile service

Science.gov (United States)

Bhatti, Nina; Baker, Harlyn; Chao, Hui; Clearwater, Scott; Harville, Mike; Jain, Jhilmil; Lyons, Nic; Marguier, Joanna; Schettino, John; Süsstrunk, Sabine

2010-01-01

Selecting cosmetics requires visual information and often benefits from the assessments of a cosmetics expert. In this paper we present a unique mobile imaging application that enables women to use their cell phones to get immediate expert advice when selecting personal cosmetic products. We derive the visual information from analysis of camera phone images, and provide the judgment of the cosmetics specialist through use of an expert system. The result is a new paradigm for mobile interactions-image-based information services exploiting the ubiquity of camera phones. The application is designed to work with any handset over any cellular carrier using commonly available MMS and SMS features. Targeted at the unsophisticated consumer, it must be quick and easy to use, not requiring download capabilities or preplanning. Thus, all application processing occurs in the back-end system and not on the handset itself. We present the imaging pipeline technology and a comparison of the services' accuracy with respect to human experts.

High Charge-Carrier Mobility of 2.5 cm(2) V(-1) s(-1) from a Water-Borne Colloid of a Polymeric Semiconductor via Smart Surfactant Engineering.

Science.gov (United States)

Cho, Jangwhan; Cheon, Kwang Hee; Ahn, Hyungju; Park, Kwang Hun; Kwon, Soon-Ki; Kim, Yun-Hi; Chung, Dae Sung

2015-10-07

Semiconducting polymer nanoparticles dispersed in water are synthesized by a novel method utilizing non-ionic surfactants. By developing a smart surfactant engineering technique involving a selective post-removal process of surfactants, an unprecedentedly high mobility of 2.51 cm(2) V(-1) s(-1) from a water-borne colloid is demonstrated for the first time. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carrier effect on separation efficiency of the column in reversed-phase partition chromatography

International Nuclear Information System (INIS)

Pszonicka, M.; Siekierski, S.

1972-01-01

Chromatographic columns were filled with carriers of diatomaceous earth type (Hyflo Super Cell, and Celite 545) of large pores, and two microporous silica gels respectively. These columns were used for the separation of europium and gadolinium by reversed-phase partition chromatography in the system: stationary phase-diethylhexylphosphoric acid (HDEHP) mobile phase-0.4 N nitric acid. In each case the separation of the above mentioned elements was achieved. The plate height that characterizes separation efficiency of the column, decreases with the decrease of particle diameter of the carrier. Best columns were obtained from carriers of large pores (Hyflo Super Cell and Celite 545) for which plate hights below 0.1 mm could be achieved. Columns filled with microporous silica gels showed plate heights of 0.2-0.3 mm. (author)

High-mobility pyrene-based semiconductor for organic thin-film transistors.

Science.gov (United States)

Cho, Hyunduck; Lee, Sunyoung; Cho, Nam Sung; Jabbour, Ghassan E; Kwak, Jeonghun; Hwang, Do-Hoon; Lee, Changhee

2013-05-01

Numerous conjugated oligoacenes and polythiophenes are being heavily studied in the search for high-mobility organic semiconductors. Although many researchers have designed fused aromatic compounds as organic semiconductors for organic thin-film transistors (OTFTs), pyrene-based organic semiconductors with high mobilities and on-off current ratios have not yet been reported. Here, we introduce a new pyrene-based p-type organic semiconductor showing liquid crystal behavior. The thin film characteristics of this material are investigated by varying the substrate temperature during the deposition and the gate dielectric condition using the surface modification with a self-assembled monolayer, and systematically studied in correlation with the performances of transistor devices with this compound. OTFT fabricated under the optimum deposition conditions of this compound, namely, 1,6-bis(5'-octyl-2,2'-bithiophen-5-yl)pyrene (BOBTP) shows a high-performance transistor behavior with a field-effect mobility of 2.1 cm(2) V(-1) s(-1) and an on-off current ratio of 7.6 × 10(6) and enhanced long-term stability compared to the pentacene thin-film transistor.

Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

International Nuclear Information System (INIS)

Feng, Shih-Wei; Liao, Po-Hsun; Leung, Benjamin; Han, Jung; Yang, Fann-Wei; Wang, Hsiang-Chen

2015-01-01

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED

Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Feng, Shih-Wei, E-mail: swfeng@nuk.edu.tw; Liao, Po-Hsun [Department of Applied Physics, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan Tzu Dist., 811 Kaohsiung, Taiwan (China); Leung, Benjamin; Han, Jung [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Yang, Fann-Wei [Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Wang, Hsiang-Chen [Graduate Institute of Opto-Mechatronics and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chia-Yi, Taiwan (China)

2015-07-28

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED.

Temperature dependence of mobility in silicon (100) inversion layers at low temperatures

International Nuclear Information System (INIS)

Kawaguchi, Y.; Suzuki, T.; Kawaji, S.

1982-01-01

Electron mobility of Si(100) n-inversion layers in MOSFETs having μsub(peak) (4.2 K) = 4000.6500 and 12000 cm 2 /V x s has been measured at temperatures between 1 and 80 K. The carrier concentration dependence of the mobility extrapolated to T = O and the temperature dependent part of the scattering probability are investigated. (orig.)

Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures

Science.gov (United States)

Zhang, Yuewei; Neal, Adam; Xia, Zhanbo; Joishi, Chandan; Johnson, Jared M.; Zheng, Yuanhua; Bajaj, Sanyam; Brenner, Mark; Dorsey, Donald; Chabak, Kelson; Jessen, Gregg; Hwang, Jinwoo; Mou, Shin; Heremans, Joseph P.; Rajan, Siddharth

2018-04-01

In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in the modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure, indicating a high-quality electron channel formed at the heterojunction interface. The formation of the 2DEG channel was further confirmed by the weak temperature dependence of the carrier density, and the peak low temperature mobility was found to be 2790 cm2/Vs, which is significantly higher than that achieved in bulk-doped Beta-phase Gallium Oxide (β-Ga2O3). The observed SdH oscillations allowed for the extraction of the electron effective mass in the (010) plane to be 0.313 ± 0.015 m0 and the quantum scattering time to be 0.33 ps at 3.5 K. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure lays the foundation for future exploration of quantum physical phenomena and semiconductor device technologies based on the β-Ga2O3 material system.

Carrier Transport Enhancement in Conjugated Polymers through Interfacial Self-Assembly of Solution-State Aggregates

KAUST Repository

Zhao, Kui

2016-07-13

We demonstrate that local and long range orders of poly(3-hexylthiophene) (P3HT) semicrystalline films can be synergistically improved by combining chemical functionalization of the dielectric surface with solution-state disentanglement and pre-aggregation of P3HT in a theta solvent, leading to a very significant enhancement of the field effect carrier mobility. The pre-aggregation and surface functionalization effects combine to enhance the carrier mobility nearly 100-fold as compared with standard film preparation by spin-coating, and nearly 10-fold increase over the benefits of pre-aggregation alone. In situ quartz crystal microbalance with dissipation (QCM-D) experiments reveal enhanced deposition of pre-aggregates on surfaces modified with an alkyl-terminated self-assembled monolayer (SAM) in comparison to un-aggregated polymer chains. Additional investigations reveal the combined pre-aggregation and surface functionalization significantly enhances local order of the conjugated polymer through planarization and extension of the conjugated backbone of the polymer which clearly translate to significant improvements of carrier transport at the semiconductor-dielectric interface in organic thin film transistors. This study points to opportunities in combining complementary routes, such as well-known pre-aggregation with substrate chemical functionalization, to enhance the polymer self-assembly and improve its interfacial order with benefits for transport properties.

Multi-User Interference Cancellation Scheme(s) for Muliple Carrier Frequency Offset Compensation in Uplink OFDMA

DEFF Research Database (Denmark)

Nguyen, Huan Cong; Carvalho, Elisabeth De; Prasad, Ramjee

2006-01-01

(ICI) and degrade the system performance considerably. In this paper, we propose a novel Multi-User Interference (MUI) cancellation scheme for uplink OFDMA, which utilizes multiple OFDM-demodulators architecture to correct and then compensate the negative effects of multiple CFOs at the receiver's side......We consider the uplink of an Orthogonal Frequency Division Multiple Access (OFDMA)-based system, where each Mobile Station (MS) experiences a different Carrier Frequency Offset (CFO). Uncorrected CFO destroy the orthogonality among subcarriers, which could cause severe Inter-Carrier Interference...

Influence of quasi-particle density over polaron mobility in armchair graphene nanoribbons.

Science.gov (United States)

Silva, Gesiel Gomes; da Cunha, Wiliam Ferreira; de Sousa Junior, Rafael Timóteo; Almeida Fonseca, Antonio Luciano; Ribeiro Júnior, Luiz Antônio; E Silva, Geraldo Magela

2018-06-20

An important aspect concerning the performance of armchair graphene nanoribbons (AGNRs) as materials for conceiving electronic devices is related to the mobility of charge carriers in these systems. When several polarons are considered in the system, a quasi-particle wave function can be affected by that of its neighbor provided the two are close enough. As the overlap may affect the transport of the carrier, the question concerning how the density of polarons affect its mobility arises. In this work, we investigate such dependence for semiconducting AGNRs in the scope of nonadiabatic molecular dynamics. Our results unambiguously show an impact of the density on both the stability and average velocity of the quasi-particles. We have found a phase transition between regimes where increasing density stops inhibiting and starts promoting mobility; densities higher than 7 polarons per 45 Å present increasing mean velocity with increasing density. We have also established three different regions relating electric field and average velocity. For the lowest electric field regime, surpassing the aforementioned threshold results in overcoming the 0.3 Å fs-1 limit, thus representing a transition between subsonic and supersonic regimes. For the highest of the electric fields, density effects alone are responsible for a stunning difference of 1.5 Å fs-1 in the mean carrier velocity.

Thermal generation and mobility of charge carriers in collective proton transport in hydrogen-bonded chains

International Nuclear Information System (INIS)

Peyrard, M.; Boesch, R.; Kourakis, I.

1991-01-01

The transport of protons in hydrogen-bonded systems is a long standing problem which has not yet obtained a satisfactorily theoretical description. Although this problem was examined first for ice, it is relevant in many systems and in particular in biology for the transport along proteins or for proton conductance across membranes, an essential process in cell life. The broad relevance makes the study of proton conduction very appealing. Since the original work of Bernal and Fowler on ice, the idea that the transport occurs through chains of hydrogen bonds has been well accepted. Such ''proton wires'' were invoked by Nagle and Morowitz for proton transport across membranes proteins and more recently across lipid bilayers. In this report, we assume the existence of such an hydrogen-bonded chain and discuss its consequences on the dynamics of the charge carriers. We show that this assumption leads naturally to the idea of soliton transport and we put a special emphasis on the role of the coupling between the protons and heavy ions motions. The model is presented. We show how the coupling affects strongly the dynamics of the charge carriers and we discuss the role it plays in the thermal generation of carriers. The work presented has been performed in 1986 and 87 with St. Pnevmatikos and N. Flyzanis and was then completed in collaboration with D. Hochstrasser and H. Buettner. Therefore the results presented in this part are not new but we think that they are appropriate in the context of this multidisciplinary workshop because they provide a rather complete example of the soliton picture for proton conduction. This paper discusses the thermal generation of the charge carriers when the coupling between the protons and heavy ions dynamics is taken into account. The results presented in this part are very recent and will deserve further analysis but they already show that the coupling can assist for the formation of the charge carriers

Theory of high temperature superconductivity

International Nuclear Information System (INIS)

Srivastava, C.M.

1989-01-01

This paper develops a semi-empirical electronic band structure for a high T c superconductor like YBa 2 Cu 3 O 6 - δ . The author accounts for the electrical transport properties on the model based on the correlated electron transfer arising from the electron-phonon interaction. The momentum pairing leading to the superconducting phase amongst the mobile charge carriers is shown

Slow hot carrier cooling in cesium lead iodide perovskites

Science.gov (United States)

Shen, Qing; Ripolles, Teresa S.; Even, Jacky; Ogomi, Yuhei; Nishinaka, Koji; Izuishi, Takuya; Nakazawa, Naoki; Zhang, Yaohong; Ding, Chao; Liu, Feng; Toyoda, Taro; Yoshino, Kenji; Minemoto, Takashi; Katayama, Kenji; Hayase, Shuzi

2017-10-01

Lead halide perovskites are attracting a great deal of interest for optoelectronic applications such as solar cells, LEDs, and lasers because of their unique properties. In solar cells, heat dissipation by hot carriers results in a major energy loss channel responsible for the Shockley-Queisser efficiency limit. Hot carrier solar cells offer the possibility to overcome this limit and achieve energy conversion efficiency as high as 66% by extracting hot carriers. Therefore, fundamental studies on hot carrier relaxation dynamics in lead halide perovskites are important. Here, we elucidated the hot carrier cooling dynamics in all-inorganic cesium lead iodide (CsPbI3) perovskite using transient absorption spectroscopy. We observe that the hot carrier cooling rate in CsPbI3 decreases as the fluence of the pump light increases and the cooling is as slow as a few 10 ps when the photoexcited carrier density is 7 × 1018 cm-3, which is attributed to phonon bottleneck for high photoexcited carrier densities. Our findings suggest that CsPbI3 has a potential for hot carrier solar cell applications.

Self-consistent simulation of carrier confinement characteristics in (AlyGa1−yN/AlN)SLs/GaN/(InxGa1−xN/GaN)MQW/GaN heterostructures

International Nuclear Information System (INIS)

Ding Jieqin; Wang Xiaoliang; Xiao Hongling; Wang Cuimei; Yin Haibo; Chen Hong; Feng Chun; Jiang Lijuan

2012-01-01

Highlights: ► We present calculations of carrier confinement characteristics. ► An optimization of In x Ga 1−x N/GaN multiquantum-well (MQW) was made. ► 2DEG sheet carrier density in designed heterostructure is greatly increased. ► Interface roughness and alloy disorder scattering reduced. ► Carrier mobility will be improved in designed heterostructure. - Abstract: We present calculations of carrier confinement characteristics in (Al y Ga 1−y N/AlN)SLs/GaN/(In x Ga 1−x N/GaN)MQW/GaN heterojunction structure in the presence of spontaneous and piezoelectrically induced polarization effects. The calculations were made using a self-consistent solution of the Schrödinger, Poisson, potential and charge balance equations. An optimization of In x Ga 1−x N/GaN multiquantum-well (MQW) was made firstly including thickness of GaN channel, InGaN, and indium composition of In x Ga 1−x N in order to increase carrier density and mobility, and the influence of pairs of AlGaN/AlN superlattices (SLs) and InGaN/GaN MQWs on structure was discussed. Theoretical calculations clearly indicate that the two-dimensional electron gas (2DEG) sheet carrier density in designed heterostructure is greatly increased due to the enhancing of carrier confinement compared to those in conventional AlGaN/GaN one at the similar Al composition. Furthermore, the calculated carrier distribution shows that carrier mobility will be improved by reducing interface roughness and alloy disorder scattering in designed heterostructure.

High-mobility BaSnO{sub 3} grown by oxide molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Raghavan, Santosh; Schumann, Timo; Kim, Honggyu; Zhang, Jack Y.; Cain, Tyler A.; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

2016-01-01

High-mobility perovskite BaSnO{sub 3} films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO{sub 3} films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnO{sub x}. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO{sub 3}. We demonstrate room temperature electron mobilities of 150 cm{sup 2} V{sup −1} s{sup −1} in films grown on PrScO{sub 3}. The results open up a wide range of opportunities for future electronic devices.

From computational discovery to experimental characterization of a high hole mobility organic crystal.

KAUST Repository

Sokolov, Anatoliy N

2011-08-16

For organic semiconductors to find ubiquitous electronics applications, the development of new materials with high mobility and air stability is critical. Despite the versatility of carbon, exploratory chemical synthesis in the vast chemical space can be hindered by synthetic and characterization difficulties. Here we show that in silico screening of novel derivatives of the dinaphtho[2,3-b:2\\',3\\'-f]thieno[3,2-b]thiophene semiconductor with high hole mobility and air stability can lead to the discovery of a new high-performance semiconductor. On the basis of estimates from the Marcus theory of charge transfer rates, we identified a novel compound expected to demonstrate a theoretic twofold improvement in mobility over the parent molecule. Synthetic and electrical characterization of the compound is reported with single-crystal field-effect transistors, showing a remarkable saturation and linear mobility of 12.3 and 16 cm(2) V(-1) s(-1), respectively. This is one of the very few organic semiconductors with mobility greater than 10 cm(2) V(-1) s(-1) reported to date.

Electron-electron scattering and mobilities in semiconductors and quantum wells

International Nuclear Information System (INIS)

Lyo, S.K.

1986-01-01

The effect of electron-electron scattering on the mobility in semiconductors and semiconductor quantum wells is examined. A general exact formula is derived for the mobility, when the electron-electron collision rate is much faster than other scattering rates such as those by ionized impurities and phonons. In this limit, the transport relaxation rate is independent of the carrier's energy and contributions to the inverse mobility from individual scattering mechanism add up. The mobility becomes significantly reduced from its value in the absence of electron-electron scattering. When the collision rates are not necessarily dominated by electron-electron scattering, the mobility is calculated by the Kohler-Sondheimer variational method in the presence of ionized-impurity scattering and acoustic-phonon scattering in a nondegenerate two-dimensional quantum well

Impact of Tortuosity on Charge-Carrier Transport in Organic Bulk Heterojunction Blends

Science.gov (United States)

Heiber, Michael C.; Kister, Klaus; Baumann, Andreas; Dyakonov, Vladimir; Deibel, Carsten; Nguyen, Thuc-Quyen

2017-11-01

The impact of the tortuosity of the charge-transport pathways through a bulk heterojunction film on the charge-carrier mobility is theoretically investigated using model morphologies and kinetic Monte Carlo simulations. The tortuosity descriptor provides a quantitative metric to characterize the quality of the charge-transport pathways, and model morphologies with controlled domain size and tortuosity are created using an anisotropic domain growth procedure. The tortuosity is found to be dependent on the anisotropy of the domain structure and is highly tunable. Time-of-flight charge-transport simulations on morphologies with a range of tortuosity values reveal that tortuosity can significantly reduce the magnitude of the mobility and the electric-field dependence relative to a neat material. These reductions are found to be further controlled by the energetic disorder and temperature. Most significantly, the sensitivity of the electric-field dependence to the tortuosity can explain the different experimental relationships previously reported, and exploiting this sensitivity could lead to simpler methods for characterizing and optimizing charge transport in organic solar cells.

Ultrafast nonlinear carrier dynamics in doped semiconductors in high THz fields

DEFF Research Database (Denmark)

Hoffmann, Matthias C.; Turchinovich, Dmitry

2011-01-01

THz frequency saturable absorption and intervalley carrier scattering in n-type semiconductors were observed using intensity-dependent transmission experiments as well as THz-pump—THz probe spectroscopy with ultrabroadband probe pulses.......THz frequency saturable absorption and intervalley carrier scattering in n-type semiconductors were observed using intensity-dependent transmission experiments as well as THz-pump—THz probe spectroscopy with ultrabroadband probe pulses....

Quality assessment of graphene: Continuity, uniformity,and accuracy of mobility measurements

Institute of Scientific and Technical Information of China (English)

David M.A.Mackenzie; Timothy J.Booth; Lene Gammelgaard; Johanna Zultak; Bjarke S.Jessen; Peter Bφggild; Dirch H.Petersen; Jonas D.Buron; Patrick R.Whelan; José M.Caridad; Martin Bjergfelt; Birong Luo; Abhay Shivayogimath; Anne L.Smitshuysen; Joachim D.Thomsen

2017-01-01

With the increasing availability of large-area graphene,the ability to rapidly and accurately assess the quality of the electrical properties has become critically important.For practical applications,spatial variability in carrier density and carrier mobility must be controlled and minimized.We present a simple framework for assessing the quality and homogeneity of large-area graphene devices.The field effect in both exfoliated graphene devices encapsulated in hexagonal boron nitride and chemical vapor-deposited (CVD) devices was measured in dual current-voltage configurations and used to derive a single,gate-dependent effective shape factor,β,for each device.β is a sensitive indicator of spatial homogeneity that can be obtained from samples of arbitrary shape.All 50 devices investigated in this study show a variation (up to tenfold) inβ as a function of the gate bias.Finite element simulations suggest that spatial doping inhomogeneity,rather than mobility inhomogeneity,is the primary cause of the gate dependence ofβ,and that measurable variations ofβ can be caused by doping variations as small as 1010 cm-2.Our results suggest that local variations in the position of the Dirac point alter the current flow and thus the effective sample shape as a function of the gate bias.We also found that such variations lead to systematic errors in carrier mobility calculations,which can be revealed by inspecting the correspondingβ factor.

Diketopyrrolopyrrole-diketopyrrolopyrrole-based conjugated copolymer for high-mobility organic field-effect transistors

KAUST Repository

Kanimozhi, Catherine K.

2012-10-10

In this communication, we report the synthesis of a novel diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP)-based conjugated copolymer and its application in high-mobility organic field-effect transistors. Copolymerization of DPP with DPP yields a copolymer with exceptional properties such as extended absorption characteristics (up to ∼1100 nm) and field-effect electron mobility values of >1 cm 2 V -1 s -1. The synthesis of this novel DPP-DPP copolymer in combination with the demonstration of transistors with extremely high electron mobility makes this work an important step toward a new family of DPP-DPP copolymers for application in the general area of organic optoelectronics. © 2012 American Chemical Society.

Highly stable microwave carrier generation using a dual-frequency distributed feedback laser

NARCIS (Netherlands)

Khan, M.R.H.; Bernhardi, Edward; Marpaung, D.A.I.; Burla, M.; de Ridder, R.M.; Worhoff, Kerstin; Pollnau, Markus; Roeloffzen, C.G.H.

2012-01-01

Photonic generation of microwave carriers by using a dual-frequency distributed feedback waveguide laser in ytterbium-doped aluminum oxide is demonstrated. A highperformance optical frequency locked loop is implemented to stabilize the microwave carrier. This approach results in a microwave

Transport and mobility properties of wurtzite InN and GaN

International Nuclear Information System (INIS)

Yarar, Zeki

2007-01-01

The results of an ensemble Monte Carlo model of the electron transport in wurtzite gallium nitride (GaN) and indium nitride (InN) are presented. There is a controversy over the material parameters of InN, therefore the recently reported and the traditionally accepted parameter values for InN are used in simulations and the results are compared. The steady-state and transient electron transport characteristics are analyzed and the valley populations of electrons are determined as a function of electric field. The low-field mobility of electrons is also obtained as a function of temperature and over a wide range of carrier concentrations. It is seen that with the recently published material parameters the peak velocity of carriers in InN increases significantly, while the field at which it is attained decreases. The calculated maximum low field mobility at 300 K in InN with the recent material parameters is about 10000 cm 2 /V s for low carrier concentrations. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Field-effect transistors with high mobility and small hysteresis of transfer characteristics based on CH3NH3PbBr3 films

Science.gov (United States)