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26 Oct 1992

Volume 61, Issue 17, pp. 2001-2118

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Nuclear magnetic resonance study on Si‐H microstructure in hydrogenated amorphous silicon prepared by diluted‐hydrogen and hydrogen‐atom‐treatment methods

Kuo‐Chiang Hsu and Huey‐Liang Hwang

Appl. Phys. Lett. 61, 2075 (1992); http://dx.doi.org/10.1063/1.108311 (3 pages) | Cited 7 times

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Silicon‐hydrogen microstructures in hydrogenated amorphous silicon films are characterized by nuclear magnetic resonance (NMR) measurements. Spectral differences are associated with hydrogen incorporation for several novel fabrication methods. It is found that hydrogen dilution of the SiH4/H2 mixture can produce a significant effect on the NMR results and that the NMR spectra tend to show a sharp line shape as the substrate temperature (Ts) is increased to about 300 °C. The hydrogen‐atom‐treatment method also produces the same effect even at a lower substrate temperature of about 250 °C.
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61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals
61.05.Qr Magnetic resonance techniques; Mössbauer spectroscopy (for structure determination only)
61.72.-y Defects and impurities in crystals; microstructure

Transverse electric and transverse magnetic polarization active intersubband transitions in narrow InGaAs quantum wells

L. H. Peng, J. H. Smet, T. P. E. Broekaert, and C. G. Fonstad

Appl. Phys. Lett. 61, 2078 (1992); http://dx.doi.org/10.1063/1.108312 (3 pages) | Cited 31 times

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Polarization‐resolved infrared spectroscopy has been used to demonstrate the existence of transverse electric (TE) and transverse magnetic (TM) active intersubband transitions in lattice‐matched, unstrained In0.53Ga0.47As/In0.52Al0.48As and strained In0.7Ga0.3As/AlAs quantum wells grown by molecular beam epitaxy on Fe‐doped semi‐insulating InP (001) substrates. It is shown that a previously reported intersubband absorption peak at 0.3 eV in a 4.0‐nm wide, lattice‐matched InGaAs/InAlAs quantum well can be resolved into two peaks active for TE and TM polarizations, respectively, with a 10 meV splitting between them. Bound to quasibound state transition at 0.59 eV (2.1 μm) for a narrow, 2.8‐nm‐wide InGaAs quantum well has also been observed. Group symmetry analyses considering D2d symmetry, tetragonal perturbation of local crystal and strain deformation potential, and interface roughness of the ternary quantum‐well structure is proposed to explain the polarization selection rules, and the Stark splitting in the intersubband absorption.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Effect of Al doping on low‐temperature epitaxy of 3C‐SiC/Si by chemical vapor deposition using hexamethyldisilane as a source material

Koji Takahashi, Shigehiro Nishino, and Junji Saraie

Appl. Phys. Lett. 61, 2081 (1992); http://dx.doi.org/10.1063/1.108313 (3 pages) | Cited 4 times

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Low‐temperature growth of 3C‐SiC by atmospheric‐pressure chemical vapor deposition was carried out using hexamethyldisilane (Si2(CH3)6) as a source material. Single‐crystal undoped SiC was grown on Si(111) without employing a carbonized buffer layer and on Si(100) with a buffer layer. In the case of adding Al(CH3)3 to the source gas, the Al‐doped initial layer works as a buffer layer which controls the initial nucleation. The Al doping lowers the expitaxial temperature of this gas system down to 1000 °C.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

In‐depth distribution of ion irradiation defects evaluated by mobility of Al0.3Ga0.7As/GaAs two‐dimensional electron gas

Yukihiro Takeuchi, Hajime Soga, Yoshiki Ueno, Toshihiko Kanayama, Yoshinobu Sugiyama, and Munecazu Tacano

Appl. Phys. Lett. 61, 2084 (1992); http://dx.doi.org/10.1063/1.108314 (3 pages) | Cited 3 times

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It has been found that the low‐temperature (<100 K) mobility of two‐dimensional electron gas is a sensitive and quantitative measure for ion irradiation defects. With this technique, the depth distribution of defects resulting from 10‐keV Ar ion irradiation (projected range=8.8 nm) to doses of 0.3–6.78×1011/cm2 onto Al0.3Ga0.7As/GaAs heterostructures was evaluated at depth of 60–120 nm. The distribution, which was estimated by reciprocal of mobility, has been found to be exponential with a 1/e penetration length of 20 nm for irradiation temperatures of 85–90 K and 16 nm for room temperature. From this result, it is suggested that the cause of defect penetration in deep regions is the ion channeling.
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61.80.Jh Ion radiation effects
61.72.U- Doping and impurity implantation
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

Some notes on the metal‐insulator‐semiconductor conductance technique

K. J. Pluciński

Appl. Phys. Lett. 61, 2087 (1992); http://dx.doi.org/10.1063/1.108315 (3 pages)

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This letter reports the study of the small‐signal approximations forming the basis of the theory of the metal‐insulator‐semiconductor conductance technique. It is shown that these approximations may cause significant errors in evaluation and interpretation of the results of the conductance measurements.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.De Semiconductor-device characterization, design, and modeling

Second harmonic generation in InGaAsP waveguides at 1.3 μm wavelength

M. Cada, M. Svilans, S. Janz, R. Bierman, R. Normandin, and J. Glinski

Appl. Phys. Lett. 61, 2090 (1992); http://dx.doi.org/10.1063/1.108316 (3 pages) | Cited 4 times

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We report the first surface emission of red light from an InGaAs waveguide, generated by the nonlinear mixing of two counterpropagating guided waves at wavelengths around 1.3 μm. A nine layer InGaAsP/InP heterostructure was grown by low pressure MOCVD on 〈100〉 InP substrate. All layers were n‐doped with silicon to a level of 1.0×1017 cm−3. The structures functioned in both planar as well as ridge waveguide configurations. Measurements were performed with both a YAG laser and a semiconductor laser in the pulsed as well as the cw regime and were compared with theoretical calculations, used in the design of the structure. Red light was detected even in a single slab InGaAsP waveguide with a cw semiconductor laser diode.  
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

High activation efficiency in Mg+ implanted GaAs by P+ coimplantation

Honglie Shen, Zuyao Zhou, Honglai Xu, Guanqun Xia, and Shichang Zou

Appl. Phys. Lett. 61, 2093 (1992); http://dx.doi.org/10.1063/1.108317 (3 pages) | Cited 5 times

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Coimplantation of 125 keV Mg+ ions and 160 keV P+ ions with the same dose of 5×1014 cm−2 was investigated. Samples were annealed in a conventional furnace or a halogen tungsten lamp rapid thermal annealing system. It was found that the additional implant of P+ improves the electrical quality of the Mg+ implanted GaAs more effectively than additional implant of As+. By using rapid thermal annealing, a maximum activation efficiency of 92% with a sheet resistance of 145 Ω/☒ was obtained for Mg+ and P+ coimplantation after an anneal at 1050 °C for 5 s, while the maximum activation efficiency for Mg+ single implant was 36% corresponding to a sheet resistance of 358 Ω/☒ after an anneal at 800 °C for 5 s. Coimplantation of P+ evidently can also reduce the redistribution of the implanted Mg.
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61.72.U- Doping and impurity implantation
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
72.80.Ey III-V and II-VI semiconductors

In situ probing at the growth temperature of the surface composition of (InGa)As and (InAl)As

Jean‐Michel Gerard

Appl. Phys. Lett. 61, 2096 (1992); http://dx.doi.org/10.1063/1.108318 (3 pages) | Cited 50 times

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A sudden shift from a bidimensional to a three‐dimensional growth mode is observed when InAs is deposited by molecular‐beam epitaxy on a pseudomorphic buffer layer grown on GaAs. The critical thickness for this shift is merely sensitive to the indium composition of the surface monolayer prior to growth. This property allows a direct in situ probing of the surface composition at the temperature of the growth. A detailed quantitative study of the surface segregation of indium atoms is performed for (InGa)As and (InAl)As alloys.  
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Nq Composition and phase identification
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Use of triethylindium and bisphosphinoethane for the growth on InP by chemical beam epitaxy

Albert Chin, Paul Martin, Utpal Das, John Mazurowski, and Jim Ballingall

Appl. Phys. Lett. 61, 2099 (1992); http://dx.doi.org/10.1063/1.108491 (3 pages) | Cited 8 times

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We have demonstrated the first CBE growth of InP using bisphosphinoethane as a group V source. Mirrorlike surface morphology and excellent reflection high‐energy electron diffraction patterns were observed. Room temperature and 77 K Hall mobilities for a 2.0 μm thick InP epitaxial layer were 4200 and 22 000 cm2/V s, with carrier densities of 5.7×1015 and 4.0×1015 cm−3, respectively. Although a high n‐type impurity concentration is observed at the epitaxial layer‐substrate interface, the epitaxial layer background impurity concentration is low enough for device fabrication. The full width at half maximum linewidth of the dominant donor bound exciton is 0.84 meV.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase

Magnetization studies of the influence of fast neutron irradiation on critical current density of melt‐textured YBa2Cu3O7−x

R. Puźniak, A. Wiśniewski, H. Szymczak, Jingrong Wang, Pingxiang Zhang, and Lian Zhou

Appl. Phys. Lett. 61, 2102 (1992); http://dx.doi.org/10.1063/1.108319 (3 pages) | Cited 4 times

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The decrease of the magnetization hysteresis loop proportional to the decrease of the sample size was found for unirradiated and fast neutron irradiated bulk samples obtained from a powder melting process (PMP). This fact indicates that the superconducting current flows throughout the whole sample even when the magnetic field is applied. Thus, the critical current is not limited by field induced decoupling of the weak links. This is a consequence of specific microstructure of PMP samples. The increase of the critical current density by the factor of about 3 was observed after irradiation in magnetic field of 1 T in the examined temperature range from 60 to 85 K. The highest critical current density of the irradiated sample determined from magnetic measurements was equal to 5×104 A/cm2 in 1 T at 77 K.  
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates

Use of Zn doping for tuning of the operating temperature of a bolometer based on the high Tc superconductor thin film of Y1Ba2Cu3O7−δ

S. B. Ogale, M. Vedawyas, G. S. T. Bendre, and S. M. Kanetkar

Appl. Phys. Lett. 61, 2105 (1992); http://dx.doi.org/10.1063/1.108320 (3 pages) | Cited 7 times

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A simple microbridge type of bolometer configuration is fabricated using high quality Zn doped Y1Ba2Cu3O7−δ superconducting thin film. It is shown that Zn doping lowers the Tco without affecting the transition width significantly. This feature is found to be useful in tuning the operating temperature of the bolometer to 77 K or to another convenient value.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.N- Response to electromagnetic fields
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Magnetic force microscopy utilizing an ultrasensitive vertical cantilever geometry

A. DiCarlo, M. R. Scheinfein, and R. V. Chamberlin

Appl. Phys. Lett. 61, 2108 (1992); http://dx.doi.org/10.1063/1.108321 (3 pages) | Cited 11 times

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We have developed a novel magnetic force microscope (MFM) utilizing a vertically cantilevered microtip probe. This new geometry provides maximum sensitivity while inhibiting uncontrolled vertical deflections (tip crashes). We demonstrate the capability of our MFM by imaging domain structure in prerecorded magnetic tape and domain walls in single‐crystal iron whiskers. Good agreement is obtained between the observed magnetic contrast and predictions of a micromagnetic model.
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75.60.Ch Domain walls and domain structure
75.70.Rf Surface magnetism

Change in conductance is the fundamental measure of spin‐valve magnetoresistance

B. Dieny, J. P. Nozieres, V. S. Speriosu, B. A. Gurney, and D. R. Wilhoit

Appl. Phys. Lett. 61, 2111 (1992); http://dx.doi.org/10.1063/1.108322 (3 pages) | Cited 15 times

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The absolute change of sheet conductance (ΔG) of spin‐valve multilayers is shown analytically and experimentally to be the macroscopic observable most directly related to the physical mechanism of giant magnetoresistance. Unlike the changes in resistance ΔR/R or ΔR, ΔG is directly connected to the changes in the Fermi spheres of the ferromagnetic layers induced by the variation in magnetic alignment. In structures comprising Si/Co 80 Å/Cu 25 Å/NiFe 50 Å/FeMn 90 Å/Ta 50 Å/Cu tCu/Ta 50 Å, in which only the thickness tCu is varied, the values and the thermal variations of ΔR/R(T) and ΔR(T) are strongly influenced by tCu through its shunting effect. In contrast ΔG is found to be independent of shunting.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Formation of carbon fibers by laser ablation of graphite

A. Sharma

Appl. Phys. Lett. 61, 2114 (1992); http://dx.doi.org/10.1063/1.108323 (2 pages) | Cited 4 times

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We describe a novel technique for the formation of carbon fibers by ablation of a graphite target with 50–150 mJ pulses of excimer laser light. Under a suitably applied electric field, carbon fibers grow on one of the electrodes as the laser ablation of graphite proceeds in a cell filled with argon gas. Optical and scanning electron micrographs of the fibers are discussed.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)

Disorder induced Raman scattering of nanocrystalline carbon

Fang Li and Jeffrey S. Lannin

Appl. Phys. Lett. 61, 2116 (1992); http://dx.doi.org/10.1063/1.108324 (3 pages) | Cited 37 times

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Weak, low frequency disorder induced Raman scattering is observed in nanocrystalline, ‘‘glassy’’ carbon having an in‐plane correlation length La≂30 Å. Similar, relatively more intense low frequency scattering is observed after the annealing of amorphous carbon films to 600 °C, suggesting the formation of quite small nanocrystallites of diameters estimated to be in the range of 10–15 Å. A comparison with the glassy carbon inelastic neutron scattering spectrum demonstrates that the Raman spectra represent a weighted phonon density of states of low frequency modes. The results confirm theoretically predicted low frequency, disorder induced scattering from nanocrystalline solids.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
63.50.-x Vibrational states in disordered systems
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