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17 Apr 2000

Volume 76, Issue 16, pp. 2149-2312

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The nitrogen transport in austenitic stainless steel at moderate temperatures

S. Parascandola, W. Möller, and D. L. Williamson

Appl. Phys. Lett. 76, 2194 (2000); http://dx.doi.org/10.1063/1.126294 (3 pages) | Cited 43 times

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A model for the transport of nitrogen in austenitic stainless steel at temperatures around 400 °C is presented and discussed. The model considers the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium. Nitrogen depth profiles simulated on the basis of the model with diffusion and detrapping activation energies of 1.1 and 1.45 eV, respectively, are in good agreement with experimental nitrogen profiles. © 2000 American Institute of Physics.
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66.30.J- Diffusion of impurities

Strain-induced optical anisotropy in self-organized quantum structures at the E1 transition

J. A. Prieto, G. Armelles, C. Priester, J. M. García, L. González, and R. García

Appl. Phys. Lett. 76, 2197 (2000); http://dx.doi.org/10.1063/1.126854 (3 pages) | Cited 10 times

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In-plane optical anisotropies of (001)-oriented InAs/InP self-assembled quantum wires and dots structures are studied by means of photoreflectance in the spectral region of the E1 transition of bulk InAs. The energy position of the transition observed in the quantum wires depends on the light polarization; quantum dots do not exhibit, in contrast, such an optical anisotropy. This anisotropy is attributed to the splitting of the four-fold degenerate E1 transition produced by the strong triaxial behavior of the strain that appears in wires and not in dots. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.20.-e Optical properties of bulk materials and thin films

Photoluminescence dynamics of amorphous Si/SiO2 quantum wells

Yoshihiko Kanemitsu, Makoto Iiboshi, and Takashi Kushida

Appl. Phys. Lett. 76, 2200 (2000); http://dx.doi.org/10.1063/1.126295 (3 pages) | Cited 14 times

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We have studied photoluminescence (PL) spectrum and dynamics of amorphous silicon (a-Si) based quantum wells at low temperatures. In a-Si/SiO2 quantum-well samples with thin a-Si layers, the PL spectra appear in the visible spectral region. With a decrease of the a-Si well thickness, the PL peak energy shifts to higher energy and the PL lifetime becomes shorter. The well-thickness and temperature dependence of the PL lifetime show that the nonradiative recombination of carriers occurs at the a-Si/SiO2 interface and the lifetime is determined by the energy relaxation process in the a-Si well and the carrier diffusion to the interface. The quantum confinement and localization of carriers in a-Si/SiO2 quantum-well structures will be discussed. © 2000 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.66.Jg Amorphous semiconductors; glasses
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.25.+i Surface conductivity and carrier phenomena
78.66.Db Elemental semiconductors and insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.20.Fr Low-field transport and mobility; piezoresistance

Mode Grüneisen parameters and negative thermal expansion of cubic ZrW2O8 and ZrMo2O8

Kai Wang and Robert R. Reeber

Appl. Phys. Lett. 76, 2203 (2000); http://dx.doi.org/10.1063/1.126296 (2 pages) | Cited 13 times

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Thermal expansion for ZrW2O8 and ZrMo2O8 is analyzed by a multifrequency Einstein model. Vibrational modes that contribute significantly to the thermal expansion are empirically identified. For ZrW2O8, a negative Grüneisen parameter mode is consistent with the observed Raman spectral peak of 40 cm−1. Experimental confirmation of the results is proposed. © 2000 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
78.30.Hv Other nonmetallic inorganics
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Enhancement of p-type doping of ZnSe using a modified (N+Te)δ -doping technique

W. Lin, S. P. Guo, M. C. Tamargo, I. Kuskovsky, C. Tian, and G. F. Neumark

Appl. Phys. Lett. 76, 2205 (2000); http://dx.doi.org/10.1063/1.126297 (3 pages) | Cited 12 times

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Delta doping techniques have been investigated to enhance the p-type doping of ZnSe. Tellurium was used as a codopant for improving the nitrogen doping efficiency. The net acceptor concentration (NA−ND) increased to 1.5×1018 cm−3 using single δ doping of N and Te (N+Te), while it was limited to 8×1017 cm−3 by δ doping of N alone. A promising approach was developed in which three consecutive δ-doped layers of N+Te were deposited for each δ-doping cycle. An enhancement in the (NA−ND) level to 6×1018 cm−3 has been achieved in ZnSe using this technique. The resultant layer has an average ZnTe content of only about 3%. This doping method shows potential for obtaining highly p-type doped ohmic contact layers without introducing significant lattice mismatch to ZnSe. Low-temperature photoluminescence spectra reveal some Te-related emissions. © 2000 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
71.55.Gs II-VI semiconductors
78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
61.72.S- Impurities in crystals

Fatigue study of metalorganic-decomposition-derived SrBi2Ta2O9 thin films: The effect of partial switching

Di Wu, Aidong Li, Huiqin Ling, Tao Yu, Zhiguo Liu, and Naiben Ming

Appl. Phys. Lett. 76, 2208 (2000); http://dx.doi.org/10.1063/1.126298 (3 pages) | Cited 30 times

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Fatigue characteristics of metalorganic-decomposition derived SrBi2Ta2O9 (SBT) ferroelectric thin films were investigated with varying film thickness, capacitor size, switching pulse amplitude, and pulse width. The effect of partial switching on fatigue was studied. An increase of nonvolatile polarization (Pnv) was observed over the initial period of fatigue when the capacitor was fully switched by the applied bipolar cycles. Fatigue increases with decreasing applied field and pulse width. These support the idea that fatigue in SBT may be viewed as a competition between domain-wall pinning and field-assisted unpinning. Partial switching caused by small field and short pulse width enhances charge trapping at domain walls, thus increasing fatigue. © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Photoelectron spectroscopic study of amorphous GaAsN films

A. R. Zanatta, P. Hammer, and F. Alvarez

Appl. Phys. Lett. 76, 2211 (2000); http://dx.doi.org/10.1063/1.126299 (3 pages) | Cited 7 times

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Amorphous gallium–arsenic–nitrogen (a-GaAsN) thin films were deposited by sputtering a crystalline GaAs target with different mixtures of argon and nitrogen. X-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES) were employed to study the Ga and As core levels and the corresponding LMM Auger transitions of films with different N concentrations. Chemical information of these samples was obtained through the analysis of the Auger parameter, which is exempt from problems inherent in the interpretation of XPS and XAES shifts, revealing aspects associated with the composition of the a-GaAsN films. In particular, these experimental results show the preferential bonding of N to Ga atoms in the formation of N-rich amorphous GaAsN films. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
79.20.Fv Electron impact: Auger emission
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Effect of phase transformations on the shape of the unloading curve in the nanoindentation of silicon

Vladislav Domnich, Yury Gogotsi, and Sergey Dub

Appl. Phys. Lett. 76, 2214 (2000); http://dx.doi.org/10.1063/1.126300 (3 pages) | Cited 133 times

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Silicon wafers subject to depth-sensing indentation tests have been studied using Raman microspectroscopy. We report a strong correlation between the shape of the load-displacement curve and the phase transformations occurring within a nanoindentation. The results of Raman microanalysis of nanoindentations in silicon suggest that sudden volume change in the unloading part of the load-displacement curve (“pop-out” or “kink-back” effect) corresponds to the formation of Si–XII and Si–III phases, whereas the gradual slope change of the unloading curve (“elbow”) is due to the amorphization of silicon on pressure release. The transformation pressures obtained in nanoindentation tests are in agreement with the results of high pressure cell experiments. © 2000 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
81.05.Cy Elemental semiconductors
62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
62.20.M- Structural failure of materials
62.20.Qp Friction, tribology, and hardness
61.43.Dq Amorphous semiconductors, metals, and alloys
78.30.Am Elemental semiconductors and insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Nonlinear resonance ultrasonic vibrations in Czochralski-silicon wafers

S. Ostapenko and I. Tarasov

Appl. Phys. Lett. 76, 2217 (2000); http://dx.doi.org/10.1063/1.126301 (3 pages) | Cited 4 times

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A resonance effect of generation of subharmonic acoustic vibrations is observed in as-grown, oxidized, and epitaxial silicon wafers. Ultrasonic vibrations were generated into a standard 200 mm Czochralski-silicon (Cz-Si) wafer using a circular ultrasound transducer with major frequency of the radial vibrations at about 26 kHz. By tuning frequency (f) of the transducer within a resonance curve, we observed a generation of intense f/2 subharmonic acoustic mode assigned as a “whistle.” The whistle mode has a threshold amplitude behavior and narrow frequency band. The whistle is attributed to a nonlinear acoustic vibration of a silicon plate. It is demonstrated that characteristics of the whistle mode are sensitive to internal stress and can be used for quality control and in-line diagnostics of oxidized and epitaxial Cz-Si wafers. © 2000 American Institute of Physics.
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62.65.+k Acoustical properties of solids
81.05.Cy Elemental semiconductors
43.25.Dc Nonlinear acoustics of solids
68.60.Bs Mechanical and acoustical properties
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
43.35.Ns Acoustical properties of thin films
43.25.Gf Standing waves; resonance
68.55.-a Thin film structure and morphology

Influence of buffer layer and growth temperature on the properties of an undoped GaN layer grown on sapphire substrate by metalorganic chemical vapor deposition

T. Wang, T. Shirahama, H. B. Sun, H. X. Wang, J. Bai, S. Sakai, and H. Misawa

Appl. Phys. Lett. 76, 2220 (2000); http://dx.doi.org/10.1063/1.126302 (3 pages) | Cited 15 times

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The influence of low-temperature buffer layer thickness on the electrical properties of GaN film is investigated, and the surface morphology is also examined by atomic force microscopy. A best surface morphology does not show best electrical properties, which could be attributed to the usual growth mechanism for GaN film on sapphire substrate. The influence of the growth temperature for the final GaN layer is also investigated. When the growth temperature increases to 1100 °C, the mobility is greatly enhanced to 600 cm2/V s with a background carrier density of 3.3×1016/cm3 at room temperature. The emission energy of the near band gap exciton at a low temperature shows a blueshift with increasing growth temperature due to an enhanced thermal stress. The calculation based on a thermal stress model agrees very well with the photoluminescence measurement. This result could partly explain the reason that the previously published values for the near band gap exciton emission energy are scattered. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
71.35.-y Excitons and related phenomena

Infrared photoluminescence and optical absorption characteristics in Ge-doped ZnSe crystals

Yoh Mita, Masayuki Akami, and Susumu Maruyama

Appl. Phys. Lett. 76, 2223 (2000); http://dx.doi.org/10.1063/1.126303 (3 pages) | Cited 1 time

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Intense infrared emission peaking at a wavelength of 1.35 μm has been observed in Ge-doped ZnSe crystals at low temperatures. The emission was particularly strong in the crystals doped with Ge in Se atmosphere and was then rapidly quenched. The emission was accompanied by a characteristic additive absorption band centered around a wavelength of 500 nm, which showed a partial but distinct metastable change upon light irradiation. The excitation spectrum and the preparation conditions of the infrared emission corresponded to those of electron spin resonance signals, owing to isolated, trivalent Ge ions in ZnSe. The nature and the possible applications of the emission are discussed. © 2000 American Institute of Physics.
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71.55.Gs II-VI semiconductors
81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors
78.40.Fy Semiconductors

Electronic structure of Ti3SiC2

R. Ahuja, O. Eriksson, J. M. Wills, and B. Johansson

Appl. Phys. Lett. 76, 2226 (2000); http://dx.doi.org/10.1063/1.126304 (3 pages) | Cited 35 times

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We have investigated the electronic structure of Ti3SiC2 by means of first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method. Our calculated volume is in good agreement (within 4%) with experiment. Also, the calculated values for c/a and positional parameters are in excellent agreement with the experimental data. We have compared the electronic structure of Ti3SiC2 with TiC. Our calculations show that Ti3SiC2 has a chemical bonding similar to the one of TiC, which is predominantly covalent. © 2000 American Institute of Physics.
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71.15.Nc Total energy and cohesive energy calculations
71.20.Ps Other inorganic compounds
61.50.Lt Crystal binding; cohesive energy
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
61.66.Fn Inorganic compounds

Ordering and shape of self-assembled InAs quantum dots on GaAs(001)

K. Zhang, Ch. Heyn, W. Hansen, Th. Schmidt, and J. Falta

Appl. Phys. Lett. 76, 2229 (2000); http://dx.doi.org/10.1063/1.126305 (3 pages) | Cited 25 times

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Quantitative grazing-incidence small-angle x-ray scattering experiments have been performed on self-assembled InAs quantum dots (QDs) grown by molecular-beam epitaxy. We find pronounced nonspecular diffuse scattering satellite peaks with high diffraction orders, indicating a lateral ordering in the spatial positions of the InAs QDs. The mean-dot–dot distance and correlation lengths of the dot lateral distribution are found to be anisotropic. We observe the sharpest dot distribution in the [110] direction. Additional broad diffraction peaks are observed and associated with dot facet crystal truncation rods of the {111} and {101} facet families. This suggests an octagonal-based dot shape. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Propagation of guided optical waves in thick GaN layers grown on (0001) sapphire

D. Ciplys, R. Gaska, M. S. Shur, R. Rimeika, J. W. Yang, and M. Asif Khan

Appl. Phys. Lett. 76, 2232 (2000); http://dx.doi.org/10.1063/1.126331 (3 pages) | Cited 8 times

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We report on the propagation of guided optical modes in insulating and Si-doped n-GaN layers grown by low-pressure metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. The effective refractive indices of the guided modes were measured using the prism-coupling technique for layers with thicknesses from 1 to 6 μm. Ordinary and extraordinary refractive indices of GaN layers at wavelength of 632.8 nm were evaluated from the comparison of the measured index values and the index values calculated by solving the characteristic equation for a planar optical waveguide. The obtained results are in a good agreement with the step-like index profile model, indicating a high optical homogeneity of the investigated layers. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.82.Et Waveguides, couplers, and arrays

Diffusion kinetics of formation of holographic polymer-dispersed liquid crystal display materials

C. C. Bowley and G. P. Crawford

Appl. Phys. Lett. 76, 2235 (2000); http://dx.doi.org/10.1063/1.126306 (3 pages) | Cited 89 times

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The underlying physical phenomena behind the increased reflection/diffraction efficiency of holographically formed polymer-dispersed liquid crystal gratings formed from blended oligomers are investigated. Using parameters determined by in situ diffraction measurements during grating formation, a phenomenological diffusion model shows that a composition modulation in the polymer network results in blended oligomer systems. Scanning electron microscope studies reveal polymer morphologies consistent with this hypothesis. © 2000 American Institute of Physics.
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61.30.-v Liquid crystals
42.40.Eq Holographic optical elements; holographic gratings
42.79.Kr Display devices, liquid-crystal devices

Observation of Li-atomic array in spinel-LiMn2O4 films spin-coated on Si substrates using an atomic force microscopy

K. Kushida and K. Kuriyama

Appl. Phys. Lett. 76, 2238 (2000); http://dx.doi.org/10.1063/1.126307 (3 pages) | Cited 15 times

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The thin films of spinel-LiMn2O4 were synthesized on (100) Si substrates by a sol-gel method and subsequent furnace annealing at various temperatures (300–800 °C) for 30 min. Li and Mn acetates (the atomic ratio Li/Mn of 1:2) were used as a coating solution, and dissolved in methanol with a small amount of a chelating agent. The films were confirmed to be a single phase of LiMn2O4 (space group: Fd3m) by x-ray diffraction studies. The surface morphologies of the films were examined by an atomic force microscopy, showing that the films consisted of bar-shaped crystalline parts. The area of these parts extended with increasing the annealing temperature. In the films annealed at 300 °C, the Li atomic array with slight distortions was observed in an atomically flat surface, which was associated with an unit cell with a lattice spacing of 8.195±0.005 Å on the (100) surface in spinel-LiMn2O4. © 2000 American Institute of Physics.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing

Evidence of strong carrier localization below 100 K in a GaInNAs/GaAs single quantum well

L. Grenouillet, C. Bru-Chevallier, G. Guillot, P. Gilet, P. Duvaut, C. Vannuffel, A. Million, and A. Chenevas-Paule

Appl. Phys. Lett. 76, 2241 (2000); http://dx.doi.org/10.1063/1.126308 (3 pages) | Cited 106 times

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We report an anomalous temperature dependence of the photoluminescence (PL) spectrum of a 7 nm Ga0.72In0.28N0.028As0.972/GaAs single quantum well. The PL peak energy exhibits an inverted S-shape dependence with temperature. Below 100 K, the PL integrated intensity shows a temperature dependence similar to that of amorphous semiconductors. The observed anomalous behavior is explained by a strong localization of carriers at low temperatures that could be induced by the presence of nitrogen. Thermal annealing does not significantly change the anomalous temperature dependence. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Distinctly different thermal decomposition pathways of ultrathin oxide layer on Ge and Si surfaces

K. Prabhakaran, F. Maeda, Y. Watanabe, and T. Ogino

Appl. Phys. Lett. 76, 2244 (2000); http://dx.doi.org/10.1063/1.126309 (3 pages) | Cited 88 times

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The thermal decomposition pathway of an ultrathin oxide layer on Ge(100) and Si(100) surfaces is examined by synchrotron radiation photoelectron spectroscopy and ultraviolet photoelectron spectroscopy with helium I radiation. The as-prepared oxide layer consists of a mixture of oxides, namely, suboxides and dioxides, on both the surfaces. Upon annealing, the oxide layers decompose and desorb as monoxides. However, we find that the decomposition pathways are different from each other. On annealing Ge oxides, GeO2 species transform to GeO and remain on the surface and desorb at >420 °C. In contrast, annealing of Si oxides results in the transformation of SiO to SiO2 up to temperatures (∼780 °C) close to the desorption. At higher temperatures, SiO2 decomposes and desorbs, implying a reverse transformation to volatile SiO species. © 2000 American Institute of Physics.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
79.60.Dp Adsorbed layers and thin films
61.72.Cc Kinetics of defect formation and annealing
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
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