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Electron Mobility (electron + mobility)
Kinds of Electron Mobility Terms modified by Electron Mobility Selected AbstractsHigh Electron Mobility and Ambient Stability in Solution-Processed Perylene-Based Organic Field-Effect TransistorsADVANCED MATERIALS, Issue 16 2009Claudia Piliego Bottom-contact n-channel OFETs based on spin-coated films of N,N, -1H,1H -perfluorobutyl dicyanoperylenediimide (PDI-FCN2) exhibit a saturation-regime mobility of 0.15,cm2 V,1 s,1 in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy. [source] High Electron Mobility in Room-Temperature Discotic Liquid-Crystalline Perylene Diimides,ADVANCED MATERIALS, Issue 21 2005Z. An Perylene diimide discotic columnar liquid-crystalline mesophases (see Figure) can show very high electron mobilities under ambient conditions. While the mobilities are strongly dependent on sample morphology and processing conditions, mobilities as high as 1.3,cm2,V,1,s,1 are measured, greater than that of amorphous silicon. [source] Acenaphtho[1,,2- c]phosphole P -Oxide: A Phosphole,Naphthalene ,-Conjugated System with High Electron MobilityCHEMISTRY - A EUROPEAN JOURNAL, Issue 39 2009Arihiro Saito One order of magnitude: Naphthalene- and acenaphthene-fused phosphole P -oxides (see figure) are shown to have reasonably high thermal and electrochemical stabilities and electron-accepting ability. The electron mobility of the naphthalene-fused phosphole P -oxide is about one order higher than that of tris(8-hydroxyquinoline)aluminium(III) Alq3 at any given electric field. [source] Low-Temperature Solution-Processed Memory Transistors Based on Zinc Oxide NanoparticlesADVANCED MATERIALS, Issue 30 2009Hendrik Faber We report on thin!film transistors based on ZnO nanoparticles processed from solution and with a maximum temperature of 100,°C. Electron mobilities up to 2.5,cm2V,1s,1 are obtained, and top-gate TFTs show non-volatile memory properties with a large, stable hysteresis and a memory ratio of 105. Memory TFTs operate in ambient, have good shelf-life (>6 months), and useful endurance properties. [source] Air-Stable n-Type Organic Field-Effect Transistors Based on Carbonyl-Bridged Bithiazole DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Yutaka Ie Abstract An electronegative conjugated compound composed of a newly designed carbonyl-bridged bithiazole unit and trifluoroacetyl terminal groups is synthesized as a candidate for air-stable n-type organic field-effect transistor (OFET) materials. Cyclic voltammetry measurements reveal that carbonyl-bridging contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the anionic species. X-ray crystallographic analysis of the compound shows a planar molecular geometry and a dense molecular packing, which is advantageous to electron transport. Through these appropriate electrochemical properties and structures for n-type semiconductor materials, OFET devices based on this compound show electron mobilities as high as 0.06,cm2 V,1 s,1 with on/off ratios of 106 and threshold voltages of 20,V under vacuum conditions. Furthermore, these devices show the same order of electron mobility under ambient conditions. [source] High Mobility and Luminescent Efficiency in Organic Single-Crystal Light-Emitting TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Satria Zulkarnaen Bisri Abstract A high-performance ambipolar light-emitting transistor (LET) that has high hole and electron mobilities and excellent luminescence characteristics is described. By using this device, a conspicuous light-confined edge emission and current-density-dependent spectral evolution are observed. These findings will result in broader utilization of device potential and they provide a promising route for realizing electrically driven organic lasers. [source] Enhanced Performance of Fullerene n-Channel Field-Effect Transistors with Titanium Sub-Oxide Injection LayerADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Shinuk Cho Abstract Enhanced performance of n-channel organic field-effect transistors (OFETs) is demonstrated by introducing a titanium sub-oxide (TiOx) injection layer. The n-channel OFETs utilize [6,6]-phenyl-C61 butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) as the semiconductor in the channel. With the TiOx injection layer, the electron mobilities of PC61BM and PC71BM FET using Al as source/drain electrodes are comparable to those obtained from OFETs using Ca as the source/drain electrodes. Direct measurement of contact resistance (Rc) shows significantly decreased Rc values for FETs with the TiOx layer. Ultraviolet photoelectron spectroscopy (UPS) studies demonstrate that the TiOx layer reduces the electron injection barrier because of the relatively strong interfacial dipole of TiOx. In addition to functioning as an electron injection layer that eliminates the contact resistance, the TiOx layer acts as a passivation layer that prevents penetration of O2 and H2O; devices with the TiOx injection layer exhibit a significant improvement in lifetime when exposed to air. [source] Ambipolar Organic Field-Effect Transistors from Cross-Conjugated Aromatic Quaterthiophenes; Comparisons with Quinoidal Parent MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Rocío Ponce Ortiz Abstract This contribution presents an electrochemical, Raman spectroscopic, and theoretical study probing the differences in molecular and electronic structure of two quinoidal oligothiophenes (3,,4,-dibutyl-5,5,-bis(dicyanomethylene)-5,5,-dihydro-2,2,:5,,2,-terthiophene and 5,5,-bis(dicyanomethylene)-3-hexyl-2,5-dihydro-4,4,-dihexyl-2,2,,5,5,-tetrahydro-tetrathiophene) with terminal tetracyanomethylene functionalization and aromatic oligothiophenes where acceptor moieties are positioned at lateral positions along the conjugated chain (6,6,-dibutylsulfanyl-[2,2,-bi-[4-dicyanovinylene-4H-cyclopenta[2,1-b:3,4-b,]dithiophene]). In this way, the consequences of linear and cross conjugation are compared and contrasted. From this analysis, it is apparent that organic field-effect transistors fabricated with cross-conjugated tetrathiophene semiconductors should combine the benefits of an electron-donor aromatic chain with strongly electron-accepting tetracyanomethylene substituents. The corresponding organic field-effect transistors exhibit ambipolar transport with rather similar hole and electron mobilities. Moreover, n-channel conduction is enhanced to yield one of the highest electron mobilities found to date for this type of material. [source] Flexible Fullerene Field-Effect Transistors Fabricated Through Solution ProcessingADVANCED MATERIALS, Issue 47 2009Chao-Feng Sung C60-based thin-film transistors are fabricated through solution processing. On rigid indium tin oxide glass, the transistors display electron mobilities as high as 0.21,cm2 V,1 s,1 and a threshold voltage of 0.7,V, only slightly lower than those of organic thin-film transistors prepared through vacuum deposition. On ITO-coated PET substrates, the mobilities in the flexible devices (see image) are approximately one order of magnitude lower than those of devices prepared on rigid glass substrates. [source] High Electron Mobility in Room-Temperature Discotic Liquid-Crystalline Perylene Diimides,ADVANCED MATERIALS, Issue 21 2005Z. An Perylene diimide discotic columnar liquid-crystalline mesophases (see Figure) can show very high electron mobilities under ambient conditions. While the mobilities are strongly dependent on sample morphology and processing conditions, mobilities as high as 1.3,cm2,V,1,s,1 are measured, greater than that of amorphous silicon. [source] Phase effects in HgTe quantum structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2007M. König Abstract HgTe quantum well structures with high electron mobilities have been used to fabricate quantum interference devices. Aharonov-Bohm oscillations have been studied in the low and high magnetic field regime. In the latter case a decrease of the effective ring radius is observed. Additionally, as a consequence of the strong Rashba spin-orbit coupling within this material, it was possible to observe conductance oscillations which are due to the so-called Aharonov-Casher effect. These quantum interference effects are effectively controlled by the applied magnetic and electric field. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Emission Color Tuning in Ambipolar Organic Single-Crystal Field-Effect Transistors by Dye-DopingADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Hajime Nakanotani Abstract The effect of dye-doping in ambipolar light-emitting organic field-effect transistors (LE-OFETs) is investigated from the standpoint of the carrier mobilities and the electroluminescence (EL) characteristics under ambipolar operation. Dye-doping of organic crystals permits not only tuning of the emission color but also significantly increases the efficiency of ambipolar LE-OFETs. A rather high external EL quantum efficiency (,0.64%) of one order of magnitude higher than that of a pure p -distyrylbenzene (P3V2) single crystal is obtained by tetracene doping. The doping of tetracene molecules into a host P3V2 crystal has almost no effect on the electron mobility and the dominant carrier recombination process in the tetracene-doped P3V2 crystal involves direct carrier recombination on the tetracene molecules. [source] Effect of Carbon Chain Length in the Substituent of PCBM-like Molecules on Their Photovoltaic PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Guangjin Zhao Abstract A series of [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM)-like fullerene derivatives with the butyl chain in PCBM changing from 3 to 7 carbon atoms, respectively (F1,F5), are designed and synthesized to investigate the relationship between photovoltaic properties and the molecular structure of fullerene derivative acceptors. F2 with a butyl chain is PCBM itself for comparison. Electrochemical, optical, electron mobility, morphology, and photovoltaic properties of the molecules are characterized, and the effect of the alkyl chain length on their properties is investigated. Although there is little difference in the absorption spectra and LUMO energy levels of F1,F5, an interesting effect of the alkyl chain length on the photovoltaic properties is observed. For the polymer solar cells (PSCs) based on P3HT as donor and F1,F5, respectively, as acceptors, the photovoltaic behavior of the P3HT/F1 and P3HT/F4 systems are similar to or a little better than that of the P3HT/PCBM device with power conversion efficiencies (PCEs) above 3.5%, while the performances of P3HT/F3 and P3HT/F5-based solar cells are poorer, with PCE values below 3.0%. The phenomenon is explained by the effect of the alkyl chain length on the absorption spectra, fluorescence quenching degree, electron mobility, and morphology of the P3HT/F1,F5 (1:1, w/w) blend films. [source] Air-Stable n-Type Organic Field-Effect Transistors Based on Carbonyl-Bridged Bithiazole DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Yutaka Ie Abstract An electronegative conjugated compound composed of a newly designed carbonyl-bridged bithiazole unit and trifluoroacetyl terminal groups is synthesized as a candidate for air-stable n-type organic field-effect transistor (OFET) materials. Cyclic voltammetry measurements reveal that carbonyl-bridging contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the anionic species. X-ray crystallographic analysis of the compound shows a planar molecular geometry and a dense molecular packing, which is advantageous to electron transport. Through these appropriate electrochemical properties and structures for n-type semiconductor materials, OFET devices based on this compound show electron mobilities as high as 0.06,cm2 V,1 s,1 with on/off ratios of 106 and threshold voltages of 20,V under vacuum conditions. Furthermore, these devices show the same order of electron mobility under ambient conditions. [source] Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Abay Gadisa Abstract The morphological, bipolar charge-carrier transport, and photovoltaic characteristics of poly(3-alkylthiophene) (P3AT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side-chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3-butylthiophene) (P3BT, m,=,4), poly(3-pentylthiophene) (P3PT, m,=,5), and poly(3-hexylthiophene) (P3HT, m,=,6). Solar cells with these blends deliver similar order of photo-current yield (exceeding 10,mA cm,2) irrespective of side-chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole-only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field-effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells. [source] Electron Trapping in Higher Adduct Fullerene-Based Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Martijn Lenes Abstract Here, the performance of bulk-heterojunction solar cells based on a series of bisadduct analogues of commonly used derivatives of C60 and C70, such PCBMs and their thienyl versions, is investigated. Due to their higher lowest unoccupied molecular orbital an increase in open-circuit voltage and thus performance is expected. It is shown that the occurrence of a multitude of different isomers results in a decrease in the electron transport for some of the materials. Surprisingly, the solar-cell characteristics are very similar for all materials. This apparent discrepancy is explained by a significant amount of shallow trapping occurring in the fullerene phase that does not hamper the solar cell performance due the filling of these shallow traps during illumination. Furthermore, the trisadduct analogue of [60]PCBM has been investigated, which, despite an even further increase in open-circuit voltage, results in a significantly reduced device performance due to a strong deterioration of the electron mobility in the fullerene phase. [source] Nanostructured Bulk Silicon as an Effective Thermoelectric MaterialADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Sabah K. Bux Abstract Thermoelectric power sources have consistently demonstrated their extraordinary reliability and longevity for deep space missions and small unattended terrestrial systems. However, more efficient bulk materials and practical devices are required to improve existing technology and expand into large-scale waste heat recovery applications. Research has long focused on complex compounds that best combine the electrical properties of degenerate semiconductors with the low thermal conductivity of glassy materials. Recently it has been found that nanostructuring is an effective method to decouple electrical and thermal transport parameters. Dramatic reductions in the lattice thermal conductivity are achieved by nanostructuring bulk silicon with limited degradation in its electron mobility, leading to an unprecedented increase by a factor of 3.5 in its performance over that of the parent single-crystal material. This makes nanostructured bulk (nano-bulk) Si an effective high temperature thermoelectric material that performs at about 70% the level of state-of-the-art Si0.8Ge0.2 but without the need for expensive and rare Ge. [source] Structure,Property Relationship of Pyridine-Containing Triphenyl Benzene Electron-Transport Materials for Highly Efficient Blue Phosphorescent OLEDsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Shi-Jian Su Abstract Three triphenyl benzene derivatives of 1,3,5-tri(m -pyrid-2-yl-phenyl)benzene (Tm2PyPB), 1,3,5-tri(m -pyrid-3-yl-phenyl)benzene (Tm3PyPB) and 1,3,5-tri(m -pyrid-4-yl-phenyl)benzene (Tm4PyPB), containing pyridine rings at the periphery, are developed as electron-transport and hole/exciton-blocking materials for iridium(III) bis(4,6-(di-fluorophenyl)pyridinato- N,C2,)picolinate (FIrpic)-based blue phosphorescent organic light-emitting devices. Their highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) energy levels decrease as the nitrogen atom of the pyridine ring moves from position 2 to 3 and 4; this is supported by both experimental results and density functional theory calculations, and gives improved electron-injection and hole-blocking properties. They exhibit a high electron mobility of 10,4,10,3,cm2,V,1,s,1 and a high triplet energy level of 2.75,eV. Confinement of FIrpic triplet excitons is strongly dependent on the nitrogen atom position of the pyridine ring. The second exponential decay component in the transient photoluminescence decays of Firpic-doped films also decreases when the position of the nitrogen atom in the pyridine ring changes. Reduced driving voltages are obtained when the nitrogen atom position changes because of improved electron injection as a result of the reduced LUMO level, but a better carrier balance is achieved for the Tm3PyPB-based device. An external quantum efficiency (EQE) over 93% of maximum EQE was achieved for the Tm4PyPB-based device at an illumination-relevant luminance of 1000,cd,m,2, indicating reduced efficiency roll-off due to better confinement of FIrpic triplet excitons by Tm4PyPB in contrast to Tm2PyPB and Tm3PyPB. [source] Solution-Deposited Zinc Oxide and Zinc Oxide/Pentacene Bilayer Transistors: High Mobility n-Channel, Ambipolar, and Nonvolatile Devices,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008Bhola Nath Pal Abstract A solution processed n-channel zinc oxide (ZnO) field effect transistor (FET) was fabricated by simple dip coating and subsequent heat treatment of a zinc acetate film. The field effect mobility of electrons depends on ZnO grain size, controlled by changing the number of coatings and zinc acetate solution concentration. The highest electron mobility achieved by this method is 7.2,cm2 V,1 s,1 with On/Off ratio of 70. This electron mobility is higher than for the most recently reported solution processed ZnO transistor. We also fabricated bilayer transistors where the first layer is ZnO, and the second layer is pentacene, a p-channel organic which is deposited by thermal evaporation. By changing the ZnO grain size (or thickness) this type of bilayer transistor shows p-channel, ambipolar and n-channel behavior. For the ambipolar transistor, well balanced electron and hole mobilities are 7.6,×,10,3 and 6.3,×,10,3,cm2 V,1 s,1 respectively. When the ZnO layer is very thin, the transistor shows p-channel behavior with very high reversible hysteresis. The nonvolatile tuning function of this transistor was investigated. [source] Influences of Connecting Unit Architecture on the Performance of Tandem Organic Light-Emitting Devices,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007Y. Chan Abstract The present work investigates the influence of the n-type layer in the connecting unit on the performance of tandem organic light-emitting devices (OLEDs). The n-type layer is typically an organic electron-transporting layer doped with reactive metals. By systematically varying the metal dopants and the electron-transporting hosts, we have identified the important factors affecting the performance of the tandem OLEDs. Contrary to common belief, device characteristics were found to be insensitive to metal work functions, as supported by the ultraviolet photoemission spectroscopy results that the lowest unoccupied molecular orbitals of all metal-doped n-type layers studied here have similar energy levels. It suggests that the electron injection barriers from the connecting units are not sensitive to the metal dopant used. On the other hand, it was found that performance of the n-type layers depends on their electrical conductivities which can be improved by using an electron-transporting host with higher electron mobility. This effect is further modulated by the optical transparency of constituent organic layers. The efficiency of tandem OLEDs would decrease as the optical transmittance decreases. [source] High Ambipolar Mobility in a Highly Ordered Smectic Phase of a Dialkylphenylterthiophene Derivative That Can Be Applied to Solution-Processed Organic Field-Effect Transistors,ADVANCED MATERIALS, Issue 3 2007M. Funahashi A phenylterthiophene derivative that exhibits a highly ordered smectic phase around room temperature is synthesized. In the bulk of the smectic phase, ambipolar carrier transport is observed and electron mobility exceeds 0.2,cm2,V,1,s,1. Thin-film transistors (see the AFM image in the figure) are fabricated by a spin-coating method and exhibit p-type operation, a field-effect mobility of 0.02,cm2,V,1,s,1, and an on/off ratio of 106. [source] All-Solution-Processed n-Type Organic Transistors Using a Spinning Metal Process,ADVANCED MATERIALS, Issue 18 2005T.-W. Lee An all-solution-processed n-type transistor of soluble fullerene derivatives, based on a photosensitive organic silver precursor route to deposit source and drain metal electrodes, is reported (see Figure). The field-effect mobility of such devices is strongly dependent on the morphology of the spin-cast semiconducting thin film. The devices fabricated in this manner show a higher electron mobility than devices fabricated by vacuum-shadow deposition. [source] Laser induced negative conductivity of diamondLASER PHYSICS LETTERS, Issue 12 2006A. S. Baturin Abstract We consider the negative mobility of electrons in diamond excited by a picosecond laser pulse at low temperatures, due to the inelastic electron-phonon collisions. For the first time the dependence of the deformation potential on the phonon wave number has been taken into account. This dependence changes significantly the region of the negative electron mobility as a function of the phonon temperature. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Cover Picture: phys. stat. sol. (RRL) 1/2007PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1 2007Article first published online: 6 NOV 200 In the Rapid Research Letter on p. R37 Musubu Ichikawa et al. report very high electron mobility above 10,3 cm2/Vs in the electron transporting material bipyridyl substituted oxadiazole (Bpy-OXD). These favourable electrical properties make the amorphous molecular semiconductor promising for potential applications in organic light-emitting diodes (OLEDs), flatpanel displays and lighting. The authors also give reasons , by means of computational chemistry , why this planar material forms stable amorphous solid films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Helicon-wave-excited plasma sputtering deposition of Ga-doped ZnO transparent conducting filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006Mutsumi Sugiyama Abstract Sputtering deposition of Ga-doped ZnO (ZnO:Ga) thin films was carried out using the helicon-wave-excited plasma sputtering (HWPS) method. The films sputtered above 150 °C had a preferential {0001} orientation. According to the surface-damage-free nature, the films having featureless surface morphology exhibited an optical transmittance greater than 80% in the visible spectral wavelengths. However, because the deposition temperature was limited to 250 °C, the electron mobility was limited to as low as 2,3 cm2/V s due to the small grain size (,25 nm). The results indicate that ZnO:Ga films deposited by HWPS can be used in the transparent conducting oxide layer, provided that higher electron mobility is achieved. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth optimisation of the GaN layers and GaN/AlGaN heterojunctions on bulk GaN substrates using plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2004C. Skierbiszewski Abstract Influence of growth conditions in plasma assisted molecular beam epitaxy on quality of GaN layers and GaN/AlGaN heterojunctions is studied. The growth diagram for step-flow growth mode and different nitrogen flux is presented. The low defect density of bulk GaN substrates together with very low impurity background concentrations resulted in high electron mobility for GaN/AlGaN heterojunctions: 109,000 cm2/Vs at 1.5 K, and 2500 cm2/Vs at 295 K. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Unintentionally doped InN grown onto an atomically flat AlN intermediate layer using plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006K. R. Wang Abstract Unintentionally doped InN has been grown onto an atomically flat AlN intermediate layer on top of the Si(111) substrate using plasma-assisted molecular beam epitaxy (PA-MBE). Though there are lots of micrometer-size indium droplets randomly distributed on the top of the surface, the highest electron mobility of this InN thin film measured at room temperature by van der Pauw method is still higher than 1000 cm2/V s with a carrier concentration of 5,8.9 × 1018 cm,3. A symmetrical X-ray rocking curve is measured and the full-width-at-half-maximum (FWHM) of this sample is 1089 arcsec. In the meantime, the threading dislocation (TD) density of this material is estimated to around 9.8 × 108 cm,2 , 7.5 × 109 cm,2 depending on the probing regions that are studied by the etching technique and field-emission scanning electron microscopy (FE-SEM). (2 × 1) in situ reflection high-energy electron diffraction (RHEED) patterns show that this sample is grown under In-rich environment with possible In-terminated surface. From the FE-SEM pictures which were taken from the samples after 10 minutes etching in hydrochloride, the surface morphology shows In-polarity-like patterns that coincide with those procured in RHEED. To select and grow a high-quality laminated AlN as intermediate layer is believed to be the major step in obtaining this high electron mobility InN thin film on Si substrate. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN/GaN-based MEMS with two-dimensional electron gas for novel sensor applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008F. Niebelschütz Abstract Novel microelectromechanical resonators structures have been realized based on AlGaN/GaN heterostructures, which provide a basis for sophisticated sensor structures. There were grown on SiC substrates confining a two dimensional electron gas (2DEG). By means of the developed etching technology, freestanding resonators were patterned without degrading the sheet carrier concentration and electron mobility of the 2DEG inside the beams, which was confirmed by electrical measurements before and after the various process steps. As actuation and read out principle magnetomotive and piezoelectric effects were used, respectively. Due to the high sensitivity of the 2DEG and the chemical stability of the utilized materials these structures are suitable for chemical and biological sensor applications, where the sensitivity of the 2DEG on the surrounding environment acts as additional sensing signal, for example for simultaneous measurements of the viscosity and pH , value of a nanoliter droplet. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 3D Monte Carlo simulation including full Coulomb interaction under high electron concentration regimesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008Tadayoshi Uechi Abstract We construct 3D Monte Carlo (MC) simulations including the full Coulomb interaction as accurately as possible. In order to achieve this goal, the usual strategy for the MC approach is employed; the Coulomb potential is split into the long-range and the short-range parts. The long-range part of the Coulomb potential is taken into account by solving the Poisson equation, in which the simulation parameters such as mesh size, charged-particle size, time step etc are carefully optimized by performing the particle simulations with turning off artificially all short-ranged scatterings. The short-range part of the Coulomb potential is incorporated into the MC simulations as scattering processes by developing a new scattering model, in which the impurities are localized in real space. It is shown that the present 3D MC simulations successfully explain the entire regime of the electron mobility as a function of impurity concentrations. In addition, it is found for the first time that the plasma frequency is modulated due to localization of the background impurities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrafast dynamics of plasmon-phonon coupling: Estimation of electron mobility in GaAsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008*Article first published online: 29 NOV 200, Muneaki Hase Abstract Utilizing a femtosecond pump-probe technique, ultrafast relaxation of plasmon-like LO phonon-plasmon coupled (LOPC) modes is studied. The time-resolved reflectivity change exhibits strong mode beating between the LO phonon and the lower branch of the LOPC modes. It is revealed that the decay of the upper branch (or plasmon-like mode) of the coupled modes is very rapid in time-frequency space, explored by using wavelet analysis. The decay time of the plasmon-like LOPC mode, which corresponds to the relaxation time ,, is obtained to be , 79 fs and this time constant enables us to extract the electron mobility , to be 2074 ± 200 cm2/Vs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||