jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Oct 2010

Volume 108, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 108, 081101 (2010); http://dx.doi.org/10.1063/1.3493111 (18 pages)

Yiping Wang
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds
back to top Electronic Structure and Transport

Polaron transport in TiO2 thin films

Abdullah Yildiz, Felicia Iacomi, and Diana Mardare

J. Appl. Phys. 108, 083701 (2010); http://dx.doi.org/10.1063/1.3493742 (8 pages) | Cited 4 times

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Undoped and Fe-doped TiO2 thin films were obtained by rf-sputtering technique onto heated glass substrates (250 °C) covered with indium tin oxide. The temperature dependence of the electrical conductivity was investigated in the temperature range 13–320 K, and it shows that the conduction mechanism in the studied samples is described by small-polaron hopping (SPH) at temperatures higher than half of the Debye temperature (θD). It was found that the magnitude of the SPH coupling increases by Fe doping in TiO2 thin films. With decreasing temperature, the conduction behavior transited from SPH conduction to variable-range hopping (VRH) conduction. In the intermediate temperature domain (200 K<T<θD/2), the VRH conduction was found to be dominant, while a temperature-independent conductivity behavior was observed in the lower temperature range (T<200 K).
Show PACS
81.15.Cd Deposition by sputtering
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Ee Mobility edges; hopping transport
71.38.-k Polarons and electron-phonon interactions
68.55.aj Insulators

Simulation of spin field effect transistors: Effects of tunneling and spin relaxation on performance

Yunfei Gao, Tony Low, Mark S. Lundstrom, and Dmitri E. Nikonov

J. Appl. Phys. 108, 083702 (2010); http://dx.doi.org/10.1063/1.3496666 (10 pages) | Cited 1 time

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A numerical simulation of spin-dependent quantum transport for a spin field effect transistor is implemented in a widely used simulator, nanoMOS. This method includes the effect of both spin scattering in the channel and the tunneling barrier between the source/drain and the channel. Accounting for these factors permits setting more realistic performance limits for the transistor, especially the magnetoresistance, which is found to be lower compared to earlier predictions. The interplay between tunneling and spin scattering is elucidated by numerical simulation. Insertion of the tunneling barrier leads to an increased magnetoresistance. Simulations are used to explore the tunneling barrier design issues.
Show PACS
85.30.Tv Field effect devices

Thermoelectric properties and crystallographic shear structures in titanium oxides of the Magnèli phases

Shunta Harada, Katsushi Tanaka, and Haruyuki Inui

J. Appl. Phys. 108, 083703 (2010); http://dx.doi.org/10.1063/1.3498801 (6 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thermoelectric properties of Magnèli phase titanium oxides TinO2n−1 (n = 2,3,…) have been investigated, paying special attention to how the thermoelectric performance can be altered by changing the microstructure. Dense polycrystalline specimens with nominal composition of TiO2−x (x = 0.05, 0.10, 0.15, and 0.20) prepared by conventional hot-pressing are all identified to be one of the Magnèli phases, in which crystallographic shear planes are regularly introduced according to the oxygen deficiency. Electrical conduction is n-type for all specimens and the carrier concentration increases with the increase in the oxygen deficiency. The values of lattice thermal conductivity, on the other hand, decrease with the increase in the oxygen deficiency, which can be attributed to phonon scattering at the crystallographic shear plane. The largest value of thermoelectric figure of merit Z, 1.6×10−4 K−1 was obtained at 773 K for the hot-pressed specimen of TiO1.90.
Show PACS
72.20.Pa Thermoelectric and thermomagnetic effects
61.72.-y Defects and impurities in crystals; microstructure
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
72.20.-i Conductivity phenomena in semiconductors and insulators
72.20.Fr Low-field transport and mobility; piezoresistance
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

X-ray photoelectron spectroscopy characterization of fluorite and perovskite phases in Sr1−xBi2+yTa2O9−z films

Housei Akazawa and Hiroshi Ando

J. Appl. Phys. 108, 083704 (2010); http://dx.doi.org/10.1063/1.3499252 (7 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High-resolution x-ray photoelectron spectroscopy of strontium bismuth tantalate films revealed distinct chemical states of constituent atoms in fluorite and perovskite crystals. Reflecting the number of nearest-neighbor oxygen atoms coordinated with Bi3+ ions, the Bi 4f peak could be deconvoluted into Bi2O3 (sixfold coordination), Bi2O2 (fourfold coordination), and (Bi2O2)2+ (intermediate between sixfold and fourfold coordination) components. We found that amorphous and fluorite phases could be expressed as a mixture of Bi2O3 and Bi2O2, whereas the (Bi2O2)2+ component representing the bismuth oxide layer, being adjacent to the (SrTa2O7)2− block, predominated in the perovskite phase. Similarly, the Sr 3d peak could be deconvoluted into the components of Sr oxide (SrO) and Sr in (SrTa2O7)2−. The volume fraction of the (SrTa2O7)2− component increased at higher annealing temperatures. The Ta 4d peaks, in contrast, located at the same binding energy for all samples, indicated that an energetically stable TaO6 octahedron unit is preferentially created. The binding energies of the O 1s state corresponding to O–Bi, O–Ta, and O–Sr bonds were identified at 531, 530, and 528.9 eV, respectively.
Show PACS
77.55.F- High-permittivity capacitive films
79.60.Dp Adsorbed layers and thin films
81.40.Gh Other heat and thermomechanical treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates

Negatively charged hydrogen at oxygen-vacancy sites in BaTiO3: Density-functional calculation

Yoshiki Iwazaki, Toshimasa Suzuki, and Shinji Tsuneyuki

J. Appl. Phys. 108, 083705 (2010); http://dx.doi.org/10.1063/1.3483243 (7 pages) | Cited 2 times

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
With a specific focus on defects formed from H atoms and oxygen vacancies (VO) in perovskite-type oxide, stability and stable valence states of complex defects formation processes within BaTiO3 are studied by using first-principle density-functional theory calculations. In our findings, H atoms diffuse as protons (H+) into interstitial sites in BaTiO3, whereas these atoms when trapped at centers of VO sites convert to negatively ionized states (H−). We also find that H atom trapping at VO sites occurs only in n-type carrier-rich environments without carrier compensation of VO2+ and H+. If carrier electrons are compensated, H+ ions are excluded from VO2+ sites due to the repulsive Coulomb potential existing between the H+ ion and the positively charged VO2+ site. Difficulties in the calculation of the diffusion-energy diagram for H atoms, involving essential changes in the stable valence states during the diffusion process, are discussed and a practical solution is presented.
Show PACS
71.55.Ht Other nonmetals
61.72.jj Interstitials
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.jd Vacancies
66.30.jp Proton diffusion

Evidence of quantum correction to conductivity in strained epitaxial LaNiO3 films

Yogesh Kumar, R. J. Choudhary, Abhinav Pratap Singh, G. Anjum, and Ravi Kumar

J. Appl. Phys. 108, 083706 (2010); http://dx.doi.org/10.1063/1.3494091 (6 pages) | Cited 3 times

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have deposited epitaxial thin films of LaNiO3 (LNO) on LaAlO3 (001) single crystals by rf-magnetron sputtering. Further, we studied the effect of systematically varied swift heavy ion irradiation induced strain on structural, electrical, and magnetotransport properties of the films. Deposited films were irradiated at varying fluence (1×1011, 1×1012, and 5×1012 ions/cm2) using 200 MeV Ag15+ beam. X-ray diffraction results reveal c-axis oriented epitaxial growth of the LNO film which is maintained even up to the highest fluence. All the films, except the one irradiated with highest fluence, show metallic behavior along with a resistivity upturn at lower temperatures. Film irradiated with the highest fluence value exhibits semiconducting behavior in the studied temperature range. Low temperature resistivity of the metallic films has been explained by quantum corrections to conductivity and it is observed that localization increases with the disorder. Presence of weak localization in metallic films is also supported by our magnetotransport data. At high temperatures, variable range hopping shown by the film irradiated with the highest fluence confirms the semiconducting behavior, which may be due to the disorder induced localization of charge carriers.
Show PACS
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Dn Low-field transport and mobility; piezoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
68.55.-a Thin film structure and morphology

Electron relaxation in empty quantum-well states of a Pb island on Cu(111) studied by Z-V (distance-voltage) spectroscopy in scanning tunneling microscopy

S. M. Lu, W. B. Su, C. L. Lin, W. Y. Chan, H. L. Hsiao, C. S. Chang, and Tien T. Tsong

J. Appl. Phys. 108, 083707 (2010); http://dx.doi.org/10.1063/1.3483241 (5 pages)

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We use the Z-V (distance-voltage) spectroscopy in scanning tunneling microscopy to detect the linewidths of empty quantum-well (QW) states acquired from a Pb island grown on the Cu(111) substrate. It is found that the continual broadening of the linewidth can extend to the electronic states near the vacuum level. We apply the Fermi-liquid theory with the Fabry–Pérot mode to analyze the linewidths of the QW states, and obtain the electron-phonon coupling constant, the electron-electron coupling factor, and the product of the electron reflectivities at the surface and interface of the Pb island.
Show PACS
73.21.Fg Quantum wells
72.15.Lh Relaxation times and mean free paths
71.10.Ay Fermi-liquid theory and other phenomenological models
63.22.Np Layered systems
63.20.kd Phonon-electron interactions
73.63.Hs Quantum wells

Temperature dependence of hole mobility in GaAs1−xBix alloys

D. A. Beaton, R. B. Lewis, M. Masnadi-Shirazi, and T. Tiedje

J. Appl. Phys. 108, 083708 (2010); http://dx.doi.org/10.1063/1.3493734 (4 pages) | Cited 2 times

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The Hall mobility of holes has been measured in GaAs grown at low temperatures and in GaAs1−xBix alloys for Bi concentrations x ranging from 0.94% to 5.5%. The hole mobility is found to decrease with increasing Bi content. The temperature dependence of the mobility in the 25 to 300 K range is fit with a combination of phonon scattering, ionized impurity scattering, and Bi related scattering. The hole scattering cross-section for an isolated Bi impurity is estimated to be 0.2 nm2. The temperature independent mobility at the highest Bi concentration (x = 5.5%), is interpreted as being limited by scattering from Bi clusters.
Show PACS
72.20.My Galvanomagnetic and other magnetotransport effects
63.20.-e Phonons in crystal lattices
61.72.S- Impurities in crystals
72.20.Ee Mobility edges; hopping transport

Enhanced high temperature thermoelectric properties of Bi-doped c-axis oriented Ca3Co4O9 thin films by pulsed laser deposition

T. Sun, H. H. Hng, Q. Y. Yan, and J. Ma

J. Appl. Phys. 108, 083709 (2010); http://dx.doi.org/10.1063/1.3499324 (5 pages) | Cited 1 time

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ca3−xBixCo4O9 (x = 0–0.4) thin films were deposited on single-crystal sapphire (0001) substrates by pulsed laser deposition. Structural characterizations indicated that these thin films exhibited perfect c-axis orientation and were well crystallized. Surface chemical states analysis confirmed Bi-substitution for Ca in the thin films with x<0.4. For the thin film with x = 0.4, excessive Bi were found isolated within the film. Due to their perfect orientation, in-plane electrical properties of these thin films measured from 300 to 740 K were found to be comparable to those of the single crystals. Furthermore, Bi-substitution was noted for the reduced electrical resistivity and enhanced Seebeck coefficient. The above superior properties resulted in a high power factor of 0.81 mW m−1 K−2 at 740 K for thin film Ca2.7Bi0.3Co4O9, which was about 29% improvement as compared to that of pure Ca3Co4O9 thin film. The results suggested that Bi-doped Ca3Co4O9 thin films could be a promising candidate for thermoelectric applications at elevated temperatures.
Show PACS
73.50.Lw Thermoelectric effects
68.55.jm Texture
73.20.At Surface states, band structure, electron density of states
81.15.Fg Pulsed laser ablation deposition
68.55.aj Insulators
73.61.Ng Insulators

Structural and electrical characteristics of high quality (100) orientated-Zn3N2 thin films grown by radio-frequency magnetron sputtering

G. Z. Xing, D. D. Wang, B. Yao, L. F. N. Ah Qune, T. Yang, Q. He, J. H. Yang, and L. L. Yang

J. Appl. Phys. 108, 083710 (2010); http://dx.doi.org/10.1063/1.3493208 (5 pages) | Cited 1 time

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on highly crystalline zinc nitride (Zn3N2) thin films which were grown by rf magnetron sputtering on quartz substrates. The substrate temperature during growth is found to strongly affect the crystal quality of the thin films. The chemical bonding states were determined by x-ray photoelectron spectroscopy. Large chemical shifts in core-level N 1s peaks with binding energy of 396.4 eV were observed as compared to N 1s of free amine (398.8 eV), indicating Zn–N bond formation. Two N 1s states were found: one is N1 formed by Zn–N bonds and another is (N2) produced by substitution of N molecules at N ion sites, which leads to larger lattice constants, consistent with x-ray diffraction results. Temperature-dependent Hall effect measurements of our Zn3N2 films exhibited distinct conduction mechanisms at specific different temperature ranges.
Show PACS
81.05.Hd Other semiconductors
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
79.60.Dp Adsorbed layers and thin films

SiBCN materials for high-temperature applications: Atomistic origin of electrical conductivity

J. Houska and S. Kos

J. Appl. Phys. 108, 083711 (2010); http://dx.doi.org/10.1063/1.3493265 (7 pages)

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The paper contains a detailed discussion of the electronic structure of the novel hard and thermally stable amorphous SiBCN materials. We focus on the weight of individual electronic states on different elements, bond types, bonds of different lengths, and the number of atoms and clusters of atoms the states are localized on. A special attention is paid to the states around the Fermi level. We show in detail the effect of individual elements and bond types on the (non)conductivity of the materials. The results provide a detailed insight into the complex relationships between the material composition and the electronic properties, and allow one to tailor SiBCN compositions which can combine different functional properties, such as high thermal stability with electrical conductivity.
Show PACS
71.23.-k Electronic structure of disordered solids
61.43.Er Other amorphous solids
72.80.Ng Disordered solids

First principles investigations of the thermoelectric behavior of tin sulfide

David Parker and David J. Singh

J. Appl. Phys. 108, 083712 (2010); http://dx.doi.org/10.1063/1.3496661 (3 pages) | Cited 1 time

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present the results of density functional theory and Boltzmann transport calculations suggesting that the commonly available and inexpensive material SnS may show reasonable thermoelectric performance at temperatures suitable for exhaust waste heat recovery, if the material can be heavily p-doped and if the mobility is not greatly degraded by high doping.
Show PACS
72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Jc Other crystalline inorganic semiconductors
61.72.up Other materials
61.72.sd Impurity concentration

Structural, electronic, and optical aspects of Cr doping of the Bi4Ge3O12: An ab initio study

A. F. Lima and M. V. Lalic

J. Appl. Phys. 108, 083713 (2010); http://dx.doi.org/10.1063/1.3500452 (8 pages)

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ab initio calculations based on density functional theory have been employed to study energetic, structural, electronic, and optical properties of Cr doped Bi4Ge3O12 (BGO). Two possible accommodations of Cr impurity have been taken into account: at the Ge (Cr4+) and the Bi (Cr3+) substitution site. For each accommodation the local structure around the Cr has been determined, and in the Cr3+ case the Cr off-site displacement was analyzed. The Cr d-states are positioned at the bottom of the conduction band and within the gap in form of two deeplike (Cr4+) and shallowlike (Cr3+) bands, exhibiting magnetic moments of +1.58 μB and −2.44 μB, respectively. The Cr dominated part of absorption spectrum is calculated and analyzed in terms of Cr band arrangement. Comparison with the experimental BGO:Cr absorption spectrum suggests that it consists of both Cr3+ and Cr4+ contributions, indicating the Cr simultaneous presence at both substitution sites.
Show PACS
71.55.Ht Other nonmetals
71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.up Other materials
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics

Many-body interaction in resonant tunneling of terahertz quantum cascade lasers

F. Wang, X. G. Guo, and J. C. Cao

J. Appl. Phys. 108, 083714 (2010); http://dx.doi.org/10.1063/1.3498803 (6 pages) | Cited 2 times

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The time-dependent population inversion is simulated by the semiconductor Bloch equations with the many-body interaction in the resonant tunneling of the terahertz quantum cascade lasers (QCLs). When the many-body interaction is considered, the oscillation amplitude of the population inversion induced by the resonant tunneling is larger in the set up process, and the steady population inversion is little larger at the same dephasing time. The gain recovery process after the terahertz QCL being pumped by a nonchirped π pulse is simulated. The gain recovery time is shorter with the many-body interaction being considered. These phenomena stem from the induced more intense resonant tunneling that caused by the renormalized energy detuning when the many-body interaction is considered. We show the importance of the many-body interaction in electron resonant tunneling between two neighbor periods of the terahertz QCL.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
84.40.-x Radiowave and microwave (including millimeter wave) technology

Effect of Li doping in NiO thin films on its transparent and conducting properties and its application in heteroepitaxial p-n junctions

Titas Dutta, P. Gupta, A. Gupta, and J. Narayan

J. Appl. Phys. 108, 083715 (2010); http://dx.doi.org/10.1063/1.3499276 (7 pages) | Cited 3 times

Online Publication Date: 25 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Li doped NiO (LixNi1−xO) thin films were epitaxially grown along [111] orientation on c-sapphire by pulsed laser deposition. The structural, electrical, and optical properties of the films were investigated using x-ray diffraction, four probe technique, and UV-visible spectra, respectively. The epitaxial growth of [111] Li doped NiO on [0001] sapphire was determined by using high resolution x-ray Φ scan. Effects of the deposition condition and Li doping concentration variations on the electrical and optical properties of Li doped NiO films were also investigated. The analysis of the resistivity data show that doped Li ions occupy the substitutional sites in the films, enhancing the p-type conductivity. The minimum resistivity of 0.15 Ω cm was obtained for Li0.07Ni0.93O film. The activation energy of Li doped NiO films were estimated to be in the range of 0.11–0.14 eV. Based upon these values, a possible electrical transport mechanism is discussed. A p-n heterojunction has also been fabricated for the optimized p-Li doped NiO with n-ZnO. The insertion of i-MgZnO between the p and n layer led to improved current-voltage characteristics due to reduced leakage current. In the diode architecture, a heteroepitaxial relationship of [111]NiO‖[0001]MgZnO‖[0001]ZnO‖[0001]GZO‖[0001]Al2O3 among the layers was obtained. The p-i-n heterojunction showed good rectification behavior with turn on voltage of 2.8 V and breakdown voltage of 8.0 V.
Show PACS
68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.up Other materials
81.15.Fg Pulsed laser ablation deposition

Hydrogen-related n-type conductivity in hydrothermally grown epitaxial ZnO films

Y. B. Zhang, G. K. L. Goh, K. F. Ooi, and S. Tripathy

J. Appl. Phys. 108, 083716 (2010); http://dx.doi.org/10.1063/1.3500353 (4 pages) | Cited 1 time

Online Publication Date: 25 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Epitaxial ZnO films were grown on single crystal spinel substrates at 90 °C in water. Hall measurements showed that the n-type carrier concentration and conductivity of the ZnO films decreased as postgrowth annealing temperature increases or pH of the growth solution decreases. At the same time, x-ray photoelectron spectroscopy, room temperature and low-temperature photoluminescence, and secondary ion mass spectroscopy observations revealed that H incorporation was enhanced at a higher pH value but reduced with increasing annealing temperature. All these observations show that the unintentionally-incorporated hydrogen in solution grown ZnO acts as a shallow donor and enhances the n-type carrier density.
Show PACS
73.61.Ga II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.ag Semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.66.Hf II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

The nonlocal dielectric function in the random phase approximation for n-type delta-doped quantum wells in GaAs

H. Rodríguez-Coppola, L. M. Gaggero-Sager, M. E. Mora-Ramos, and R. Pérez-Álvarez

J. Appl. Phys. 108, 083717 (2010); http://dx.doi.org/10.1063/1.3493206 (10 pages)

Online Publication Date: 26 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The nonlocal dielectric function, calculated using the random phase approximation (RPA) is obtained for a delta-doped quantum well of Si in GaAs. The formal analysis can be performed by considering the response function in the RPA and/or further approximations. The behavior of the real and imaginary parts of the dielectric function is studied for different values of three basic parameters of the system: the energy of an exciting signal, the in-plane linear momentum, and the distance from the doping plane as a function of the concentration of electrons in the doping plane. The results are obtained varying the concentration of electrons in the doping plane from n2D = 3×1012 to 7×1012 cm−2. They show a natural change in the intensity of the dielectric response as long as the concentration changes from n2D = 6×1012 to 7×1012 cm−2, in agreement with recent experimental results for the mobility of electric carriers.
Show PACS
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
61.72.U- Doping and impurity implantation
73.63.Hs Quantum wells
73.21.Fg Quantum wells
71.15.-m Methods of electronic structure calculations

Spin-degenerate surface and the resonant spin lifetime transistor in wurtzite structures

Wan-Tsang Wang, C. L. Wu, J. C. Chiang, Ikai Lo, H. F. Kao, Y. C. Hsu, W. Y. Pang, D. J. Jang, Meng-En Lee, Yia-Chung Chang, and Chun-Nan Chen

J. Appl. Phys. 108, 083718 (2010); http://dx.doi.org/10.1063/1.3484042 (4 pages) | Cited 1 time

Online Publication Date: 27 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Spin-splitting energies of wurtzite AlN and InN are calculated using the linear combination of atomic orbital method, and the data are analyzed utilizing the two-band k⋅p model. It is found that in the k⋅p scheme, a spin-degenerate surface exists in the wurtzite Brillouin zone. Consequently, the D’yakonov-Perel’ spin relaxation mechanism can be effectively suppressed for all spin components in the [001]-grown wurtzite quantum wells (QWs) at a resonant condition through application of appropriate strain or a suitable gate bias. Therefore, wurtzite QWs (e.g., InGaN/AlGaN and GaN/AlGaN) are potential structures for spintronic devices such as the resonant spin lifetime transistor.
Show PACS
85.75.Hh Spin polarized field effect transistors
85.30.Tv Field effect devices
73.20.At Surface states, band structure, electron density of states
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
68.65.Fg Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Appearance of a correlation between the Hall coefficient and electrical resistivity upon dihydrogenation of yttrium

M. Sakai, D. Kodama, S. Ito, M. Ito, O. Nakamura, S. Hasegawa, A. Kitajima, and A. Oshima

J. Appl. Phys. 108, 083719 (2010); http://dx.doi.org/10.1063/1.3500443 (7 pages)

Online Publication Date: 28 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
To shed light on the correlation between the Hall coefficient (RH) and electrical resistivity (ρ), we performed simultaneous measurements of these two transport coefficients in fcc dihydride phase of yttrium (YHx), having H/Y values ranging from 1.73 to 2.04. Unlike the typical behavior of metals, an approximately linear relationship was observed between RH and ρ at room temperature after dihydrogenation of yttrium. Interpretation of this relationship, based on the Boltzmann–Bloch scheme, reveals that the transverse (cyclotron) relaxation rate (1/τc) of the carriers is relatively insensitive to the generation of hydrogen defects in the dihydride phase of yttrium, unlike the longitudinal relaxation rate (1/τ), which is affected by the presence of hydrogen defect. Low-temperature (77 K) measurements of RH and ρ on the same samples show that the approximately linear relationship observed at room temperature disappears but a certain nonlinear relationship may exist at 77 K.
Show PACS
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
82.30.-b Specific chemical reactions; reaction mechanisms

Real-time counting of single electron tunneling through a T-shaped double quantum dot system

JunYan Luo, Shi-Kuan Wang, Xiao-Ling He, Xin-Qi Li, and YiJing Yan

J. Appl. Phys. 108, 083720 (2010); http://dx.doi.org/10.1063/1.3501026 (7 pages)

Online Publication Date: 28 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Real-time detection of single electron tunneling through a T-shaped double quantum dot is simulated, based on a Monte Carlo scheme. The double dot is embedded in a dissipative environment and the presence of electrons on the double dot is detected with a nearby quantum point contact. We demonstrate directly the bunching behavior in electron transport, which leads eventually to a super-Poissonian noise. Particularly, in the context of full counting statistics, we investigate the essential difference between the dephasing mechanisms induced by the quantum point contact detection and the coupling to the external phonon bath. A number of intriguing noise features associated with various transport mechanisms are revealed.
Show PACS
73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Gk Tunneling
73.63.Kv Quantum dots
81.07.Ta Quantum dots
73.21.La Quantum dots
72.70.+m Noise processes and phenomena

Impacts of recombination at the surface and in the substrate on carrier lifetimes of n-type 4H–SiC epilayers

Tsunenobu Kimoto, Toru Hiyoshi, Toshihiko Hayashi, and Jun Suda

J. Appl. Phys. 108, 083721 (2010); http://dx.doi.org/10.1063/1.3498818 (7 pages) | Cited 6 times

Online Publication Date: 28 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
After remarkable reduction in the Z1/2 center in n-type 4H–SiC epilayers, the measured carrier lifetimes can be severely affected by other recombination paths. Impacts of carrier recombination at the surface as well as in the substrate are investigated in detail by using numerical simulation based on a diffusion equation. The simulation reveals that a very thick (>100 μm) epilayer is required for accurate measurement of carrier lifetimes if the bulk lifetime in the epilayer is longer than several microsecond, due to the extremely short lifetimes in the substrate. The fast decay often observed at the initial stage of decay curves can be explained by fast recombination at the surface and in the substrate. In experiments, the carrier lifetime is improved from 0.69 to 9.5 μs by reducing the Z1/2 center via two-step thermal treatment (thermal oxidation and Ar annealing) for a 148-μm-thick n-type epilayer. This lifetime must be still, to large extent, affected by the recombination at the surface and in the substrate, and the real bulk lifetime may be much longer. The carrier recombination paths and their impacts on the decay curves are discussed.
Show PACS
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.80.Jc Other crystalline inorganic semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena
Author Select

Consideration of the mechanism of microwave emission due to material destruction

Tadashi Takano, Hirokazu Ikeda, and Takashi Maeda

J. Appl. Phys. 108, 083722 (2010); http://dx.doi.org/10.1063/1.3499291 (5 pages)

Online Publication Date: 29 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Microwave emission due to material destruction by hypervelocity impact with several kilometers per second was found at 2 and 22 GHz, and its power was calibrated in the laboratory for the first time ever. In this paper, we first summarize the experimental results in relation to the mechanism of microwave emission. We then propose three kinds of hypotheses on the mechanism, which are based on the dynamic relative motion of an atom’s nucleus and the outermost electron and lead to dipole radiation. The deduced equation represents the power dependence on the target’s thickness, which agrees well with the experimental result. The models were then numerically analyzed in consideration of the experimental data. In the most promising model, a projectile molecule flicks the nucleus out and the outermost electron is left out of the orbit of the atom. Accordingly, the material is polarized or ionized to form an impulsive dipole, which leads to microwave emission. This model is compatible with material ionization by mechanical excitation, such as rubbing and peeling, or triboelectricity. The calculated energy shows good agreement with the experimental value. On the other hand, if the outermost electron remains within the gravity field of the nucleus, the calculated and experimental results do not agree with each other.
Show PACS
62.50.Ef Shock wave effects in solids and liquids
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.35.Ja Surface and interface dynamics and vibrations
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Electronic effect on hydrogen brittleness of austenitic steels

V. G. Gavriljuk, B. D. Shanina, V. N. Shyvanyuk, and S. M. Teus

J. Appl. Phys. 108, 083723 (2010); http://dx.doi.org/10.1063/1.3499610 (9 pages)

Online Publication Date: 29 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Hydrogen effects in austenitic steels are studied using the ab initio calculations of the electronic structure, conduction electron spin resonance, internal friction, and mechanical tests. It is shown that the hydrogen-caused elastic shielding of dislocations is not sufficient for interpretation of hydrogen-enhanced localized plasticity (HELP). Similar effects of hydrogen and nitrogen and the opposite effect of carbon on dislocation mobility are demonstrated, which cannot be explained within the framework of continuum mechanics. An interpretation of hydrogen embrittlement in terms of the hydrogen-increased concentration of free (conduction) electrons is proposed. Based on the electronic approach to the HELP phenomenon, practical recommendations for increase in hydrogen resistance of austenitic steels are made and tested.
Show PACS
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.25.Mn Fracture/brittleness
76.30.-v Electron paramagnetic resonance and relaxation
81.40.Lm Deformation, plasticity, and creep
71.20.Gj Other metals and alloys
62.20.mj Brittleness
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close