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1 Oct 2000

Volume 88, Issue 7, pp. 3795-4457

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Glass transition behavior, crystallization kinetics, and microstructure change of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass under high pressure

Wei Hua Wang, Yan Xin Zhuang, Ming Xiang Pan, and Yu Su Yao

J. Appl. Phys. 88, 3914 (2000); http://dx.doi.org/10.1063/1.1290262 (5 pages) | Cited 15 times

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Glass transition behavior, crystallization kinetics, and the microstructural change of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) are studied in ambient, annealing, and high pressure conditions. Significant structural relaxation induced by preannealing and high pressure annealing has been observed in the BMG obtained with a low cooling rate. The experimental results indicate that the BMG contains a large amount of vacancy-like free volume. The relaxation results in the microstructural transformation from short-range order to medium-range order and significant effects on the subsequent glass transition and crystallization. The role of relaxation in the glass transition and the crystallization is phenomenologically explained. © 2000 American Institute of Physics.
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61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids

Residual stress in deuterium implanted nominal copper coatings

M. Y. Inal, M. Alam, R. A. Peascoe, and T. R. Watkins

J. Appl. Phys. 88, 3919 (2000); http://dx.doi.org/10.1063/1.1289795 (7 pages) | Cited 3 times

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The effects of deuterium (D) implantation on the residual stresses in Cu and CuAl2 phases present in nominal Cu coatings (containing Al) deposited on Al-alloy (Al-6061) substrates were measured using an x-ray diffraction technique. The coatings were deposited by radio frequency magnetron sputtering of a pure Cu target under identical conditions and Al was incorporated in the coatings during growth by diffusion from the substrate. Deuterium was implanted in the coatings at energies of 40 or 40+120 keV with fluences of 1×1021, 2×1021, or 3×1021 D+/m2. Pole figures of the Cu phase in the coatings prior to and after implantation indicated no effect of implantation on the fibrous texture. Triaxial stress analysis indicated the surface normal stress component to be negligible in Cu and slightly tensile in CuAl2 under all conditions. Furthermore, under all conditions, the in-plane residual stresses in both phases were found to be compressive and nearly isotropic. The magnitude of the isotropic compressive stress was always higher in CuAl2 as compared to Cu. The compressive residual stresses in the Cu phase changed only mildly with increasing coating weight, ion energy, and fluence. However, in the CuAl2 phase the compressive residual stresses changed markedly with increasing ion energy (initial decrease followed by leveling off) and increasing ion fluence (initial decrease followed by an increase), but remained unaffected by increasing coating weight. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys
62.20.-x Mechanical properties of solids

Crystallization behavior of as-deposited, melt quenched, and primed amorphous states of Ge2Sb2.3Te5 films

Pramod K. Khulbe, Ewan M. Wright, and Masud Mansuripur

J. Appl. Phys. 88, 3926 (2000); http://dx.doi.org/10.1063/1.1289811 (8 pages) | Cited 36 times

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We compare the crystallization behavior of thin films of Ge2Sb2.3Te5 in various amorphous states, namely, as-deposited, melt-quenched, and primed. These films are embedded in a quadrilayer stack similar in structure to the commercially available phase-change optical disks. This study shows that the melt-quenched amorphous film has a shorter crystallization onset time and a higher crystallization rate in comparison to the as-deposited amorphous film. We also observed that variable priming leads to crystallization behavior falling between that of the as-deposited and melt-quenched states. A qualitative model of the modification in crystallization behavior due to priming is given based on the notion that priming produces crystalline embryos which hastens crystallization process. © 2000 American Institute of Physics.
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61.43.Fs Glasses
42.70.Ce Glasses, quartz
78.66.Jg Amorphous semiconductors; glasses
42.79.Vb Optical storage systems, optical disks
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Coarsening and phase separation in ultraviolet cured polymer dispersed liquid crystals

L. Lucchetti and F. Simoni

J. Appl. Phys. 88, 3934 (2000); http://dx.doi.org/10.1063/1.1290264 (7 pages) | Cited 14 times

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An extended investigation of the phase separation process in polymer dispersed liquid crystals is presented. A detailed analysis of the experimental results shows that the nucleation and growth of the liquid crystal droplets from the polymeric matrix can be described as the coarsening process occurring in binary alloys. © 2000 American Institute of Physics.
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61.30.-v Liquid crystals
64.75.-g Phase equilibria
82.50.-m Photochemistry
82.35.-x Polymers: properties; reactions; polymerization

Effect of radiation-induced defects on silicon solar cells

S. Zh. Karazhanov

J. Appl. Phys. 88, 3941 (2000); http://dx.doi.org/10.1063/1.1290453 (7 pages) | Cited 7 times

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Recent experiments indicated an anomalous degradation of n+–p–p+ silicon space solar cells irradiated with high-energy protons or electrons. Several models have been proposed, which assumes that radiation-induced defects are responsible for the degradation. The effect of the radiation-induced deep defects with energy levels Ec−0.17, Ec−0.1, Ec−0.43, and Ev+0.36 eV on solar cells is studied in this article. It is shown that among these defects only the defect with energy level Ec−0.1 eV causes the anomalous degradation, when the base thickness W is approximately 250 μm. © 2000 American Institute of Physics.
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84.60.Jt Photoelectric conversion
81.05.Cy Elemental semiconductors
61.82.Fk Semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Cn Elemental semiconductors
73.61.Cw Elemental semiconductors
61.80.Jh Ion radiation effects
61.80.Fe Electron and positron radiation effects

Raman scattering study of GaAs crystalline layers grown by molecular beam epitaxy at low temperature

H. Sano, A. Suda, T. Hatanaka, G. Mizutani, and N. Otsuka

J. Appl. Phys. 88, 3948 (2000); http://dx.doi.org/10.1063/1.1290263 (6 pages) | Cited 2 times

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Raman scattering, x-ray diffraction, and transmission electron microscopy (TEM) were used to study GaAs layers grown by molecular beam epitaxy at low substrate temperatures (LT-GaAs). The intensity of forbidden Raman scattering of longitudinal optical and transverse optical phonons linearly increases as a function of the concentration of excess As in the range of [AsGa]=0.04×1020–1.175×1020 cm−3. Concentrations of excess As in LT-GaAs layers were estimated from the lattice spacings measured with an x-ray diffractometer. No obvious defect was seen in cross-sectional TEM images of these nonstoichiometric As-rich GaAs layers. The origin of the forbidden Raman scattering of the nonstoichiometric LT-GaAs layers is explained as the strain induced by AsGa (As antisite)-related defects with low structural symmetry. © 2000 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.J- Point defects and defect clusters

Characterization of Si nanocrystals grown by annealing SiO2 films with uniform concentrations of implanted Si

S. Guha, S. B. Qadri, R. G. Musket, M. A. Wall, and Tsutomu Shimizu-Iwayama

J. Appl. Phys. 88, 3954 (2000); http://dx.doi.org/10.1063/1.1308096 (8 pages) | Cited 24 times

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We have performed physical and optical characterization of Si nanocrystals grown by ion implantation of Si+ ions at multiple energies with varying doses into thermally grown SiO2 films. The purpose of multiple implants was to achieve uniform composition of the added Si profile throughout the SiO2 film to produce Si particles with a narrow size distribution upon annealing at 1000 °C in a nitrogen atmosphere. The depth distribution of the composition and sizes of the Si particles in SiO2 films before and after the anneal were determined using Rutherford backscattering (RBS), forward recoil spectroscopy, small-angle x-ray diffraction (SXRD), and high-resolution transmission electron microscopy (HRTEM). From RBS we concluded that the amount of free silicon was reduced by annealing, presumably due to oxidation in the annealing process. The mean cluster sizes of the annealed samples were determined by SXRD. HRTEM was also employed to determine the average size of Si particles. Photoluminescence spectra (PL) from these samples were broad and the peak positions of the PL spectra were blue-shifted with decreasing cluster size. The line shapes of the PL spectra were calculated with a quantum confinement model assuming a log-normal size distribution of Si nanoparticles and (1/D)1.25 dependence of the band gap energy as a function of particle size D. The band gap energy and the average particle size obtained from the calculated line shape spectra agree well with the quantum confinement model. © 2000 American Institute of Physics.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.72.Cc Kinetics of defect formation and annealing
61.72.up Other materials
61.80.Jh Ion radiation effects
61.82.Ms Insulators
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

X-ray induced photoemission of a localized electron and its application to site-selective x-ray absorption fine structure measurement

Masashi Ishii, Yoko Yoshino, Ken-ichi Takarabe, and Osamu Shimomura

J. Appl. Phys. 88, 3962 (2000); http://dx.doi.org/10.1063/1.1308098 (6 pages) | Cited 4 times

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For local structure analyses of carrier trap centers in semiconductors, site-selective x-ray absorption fine structure (XAFS) measurement, the “capacitance XAFS” method, is proposed. The concept of capacitance XAFS measurement is based on the fact that the amount of x-ray absorption of trap centers, not the bulk, may be evaluated from the capacitance change due to x-ray induced photoemission of a localized electron. In order to verify this model, characteristics of x-ray induced photoemission from defects are investigated by capacitance–voltage measurement. The temperature dependence of the photocarrier concentration in a semiconductor corresponds to that of the capacitance XAFS signal amplitude. On the other hand, no influence of the thermal excitation of defects on the capacitance XAFS signal amplitude is observed. These results indicate that the capacitance XAFS signal originates from localized electron emission via the inner-shell excitation of defect atoms, resulting in site selectivity to the trap centers. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.70.Dm X-ray absorption spectra

Influence of microwave energy on semiconductors during ion implantation process

H-C. Gay, P. Gibert, and J. Lin-Kwang

J. Appl. Phys. 88, 3968 (2000); http://dx.doi.org/10.1063/1.1289218 (8 pages) | Cited 1 time

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Microwave energy is used during the implantation-annealing process of semiconductors where it is shown that the implant ion damage anneal takes place at the same time as the implantation step. The microwave energy is observed to be focused within the plasma volume created by the electron–hole pairs, where the conductivity is increased considerably. It is shown that the implantation takes place perpendicularly with respect to the wafer surface and that there is very little lateral redistribution of ions. The transmission electron microscopy and measurements of the implanted zone confirm the predicted good results of this process. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
72.30.+q High-frequency effects; plasma effects

Low temperature, postgrowth self-doping of CdTe single crystals due to controlled deviation from stoichiometry

V. Lyahovitskaya, L. Chernyak, J. Greenberg, L. Kaplan, and David Cahen

J. Appl. Phys. 88, 3976 (2000); http://dx.doi.org/10.1063/1.1308065 (6 pages) | Cited 3 times

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Careful analysis of the Cd–Te pressure-temperature-composition phase diagram, shows a deviation of CdTe stoichiometry only in the Te-depletion direction between 450 and 550 °C. Combined control over the semiconductor composition, via intrinsic defects, and over the atmosphere and cooling rate can, therefore, yield a process for intrinsic doping of CdTe at these relatively low temperatures. We present results that support this. Quenching of CdTe, following its annealing in Te atmosphere at 400–550 °C, leads to p-type conductivity with a hole concentration of ∼2×1016 cm−3. Slow cooling of the samples, after 550 °C annealing in Te or in vacuum, increases the hole concentration by one order of magnitude, as compared to quenching at the same temperature. We explain this increase by the defect reaction between Te vacancies and Te interstitials. Annealing in Cd at 400–550 °C leads to n-type conductivity with an electron concentration of ∼2×1016 cm−3. Annealing at 450–550 °C in the equilibrium atmosphere, provided by adding CdTe powder, gives n-type material. © 2000 American Institute of Physics.
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61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology

Transmission electron microscopy analysis of crystallographic transition from fcc to fct on PtMn spin valves

Akihiro Maesaka, Satoru Ishii, and Akihiiko Okabe

J. Appl. Phys. 88, 3982 (2000); http://dx.doi.org/10.1063/1.1309051 (6 pages) | Cited 10 times

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The structural changes during the crystallographic transition from fcc to fct of antiferromagnetic PtMn layers with postdeposition annealing, in spin-valve multilayers constructed by Ta/PtMn/CoFe/Cu/CoFe/NiFe/Ta/Si, were investigated using transmission electron microscopy and energy dispersive x-ray spectroscopy. We determined that the crystallographic orientation of the PtMn layers after postdeposition annealing depends on the initial size of the columnar grains in as-deposited spin valves. For spin valves with an initial grain size of 10 nm, the fcc→fct transition of PtMn layers was completed with the crystallographic orientation on the (111) texture. In contrast, spin valves with an initial grain size of 50 nm brought about a crystallographic reconstruction of the PtMn layer due to the tensile stress from neighboring grains during the fcc→fct transition. This results in a transformation from a fcc(111) to a fct(101) texture and a recombination of grains to form giant grains of 300–500 nm in the PtMn layer. This dynamic reconstruction promotes the interlayer diffusion of constituent atoms in spin-valve multilayers, leading to an increase in the interlayer coupling field between the pinned and free layers (Hin) and a promotion of thermal degradation of magnetoresistance (ΔR). © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
64.70.K- Solid-solid transitions
75.50.Ee Antiferromagnetics
61.72.Cc Kinetics of defect formation and annealing
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.35.Fx Diffusion; interface formation

Oxidation induced precipitation in Al implanted epitaxial silicon

A. La Ferla, G. Galvagno, P. K. Giri, G. Franzò, E. Rimini, V. Raineri, A. Gasparotto, and D. Cali

J. Appl. Phys. 88, 3988 (2000); http://dx.doi.org/10.1063/1.1309049 (5 pages)

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The behavior of Al implanted in silicon has been investigated during thermal oxidation. It has been found that precipitation of Al into Al–O-defect complexes depends on the implant energy, i.e., on the distance of the dopant from the surface. It occurs at 650 keV, but it does not at 2.0 MeV or higher energies. This phenomenon has been explained taking into account the diffusivity of self-interstitials introduced during oxidation, the oxygen present in the Si, the Al concentration, and the annealing out of defects. © 2000 American Institute of Physics.
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81.65.Mq Oxidation
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
81.05.Cy Elemental semiconductors

Damage profiles in high-energy As implanted Si

G. Lulli, M. Bianconi, A. Parisini, S. Sama, and M. Servidori

J. Appl. Phys. 88, 3993 (2000); http://dx.doi.org/10.1063/1.1290712 (7 pages) | Cited 8 times

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Deep distributions of lattice disorder induced in Si by room temperature, high-energy (3 MeV), nonamorphizing As ion implants have been characterized by Rutherford backscattering spectrometry channeling (RBS-C), double crystal x-ray diffractometry (DCXD), and cross-sectional transmission electron microscopy (XTEM). After accurate calibration of the measurement conditions, the depth positions of the profiles of displaced atoms, lattice strain, and XTEM weak-beam dark-field contrast in a sample implanted at a dose of 1014 As cm−2 agree within 3%. This confirms that the quantities measured by the three techniques have a similar qualitative correlation with the depth profile of as-implanted damage. The shape of the disorder profiles indicates different rates of damage accumulation as a function of depth, which have been characterized by a series of DCXD measurements at doses in the range 1012–1014 As cm−2. The problem of a quantitative determination of the number of defects is also addressed. In particular, the result of RBS-C, which gives as output the concentration of displaced atoms, is sensitive to the configuration of damage assumed when fitting experimental spectra. As a consequence, to give a reliable estimate of defect number a more refined microstructural model of damage (including, for instance, the deformation induced in the background lattice by heavily displaced atoms) should be used within the simulation of the measurement process. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.S- Impurities in crystals
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Localization of gate oxide integrity defects in silicon metal-oxide-semiconductor structures with lock-in IR thermography

S. Huth, O. Breitenstein, A. Huber, and U. Lambert

J. Appl. Phys. 88, 4000 (2000); http://dx.doi.org/10.1063/1.1310185 (4 pages) | Cited 9 times

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A technique to image gate oxide integrity (GOI) defects across large gate areas has been developed. First, a low-ohmic bias pulse is used in order to break down nearly all GOI defects in a large area metal-oxide-semiconductor (MOS) structure. Then a periodic bias of typically 2 V is applied and the local heating caused by the leakage current through the broken GOI defects is imaged by infrared (IR) lock-in thermography. This method allows us to detect very small temperature variations down to 10 μK at a lateral resolution down to 10 μm. The determined defect densities in Czochralski silicon materials with various densities of crystal originated particles are in good agreement with charge-to-breakdown measurements of small area MOS capacitors. In conclusion, IR lock-in thermography provides a fast and reliable imaging technique of the lateral GOI defect distribution across the entire wafer area. © 2000 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
42.79.Pw Imaging detectors and sensors
84.32.Tt Capacitors

Cavity expansion resistance of brittle materials obeying a two-curve pressure–shear behavior

Sikhanda S. Satapathy and Stephan J. Bless

J. Appl. Phys. 88, 4004 (2000); http://dx.doi.org/10.1063/1.1288007 (9 pages) | Cited 5 times

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We derived a closed-form solution for the pressure required to open a spherical or a cylindrical cavity in brittle materials which demonstrate a two-curve pressure–shear behavior. The material is allowed to crack under tension and fail under shear; only both failure modes result in comminution. Since the cavity expansion pressure is closely related to the penetration resistance of a target material, this solution identifies the material parameters that are important in impact and penetration problems. It is found that cracking and comminution can be prevented when a large enough confinement pressure is present, and the resulting high cavity expansion resistance could explain the intriguing phenomenon of interface defeat. The effects of dilatancy, and shear strength of comminuted ceramic on cavity expansion pressure are explicitly revealed. © 2000 American Institute of Physics.
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62.20.M- Structural failure of materials
46.50.+a Fracture mechanics, fatigue and cracks
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Void-containing materials with tailored Poisson’s ratio

Olga A. Goussev, Peter Richner, Michael G. Rozman, and Andrei A. Gusev

J. Appl. Phys. 88, 4013 (2000); http://dx.doi.org/10.1063/1.1289236 (4 pages) | Cited 6 times

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Assuming square, hexagonal, and random packed arrays of nonoverlapping identical parallel cylindrical voids dispersed in an aluminum matrix, we have calculated numerically the concentration dependence of the transverse Poisson’s ratios. It was shown that the transverse Poisson’s ratio of the hexagonal and random packed arrays approached 1 upon increasing the concentration of voids while the ratio of the square packed array along the principal continuation directions approached 0. Experimental measurements were carried out on rectangular aluminum bricks with identical cylindrical holes drilled in square and hexagonal packed arrays. Experimental results were in good agreement with numerical predictions. We then demonstrated, based on the numerical and experimental results, that by varying the spatial arrangement of the holes and their volume fraction, one can design and manufacture voided materials with a tailored Poisson’s ratio between 0 and 1. In practice, those with a high Poisson’s ratio, i.e., close to 1, can be used to amplify the lateral responses of the structures while those with a low one, i.e., close to 0, can largely attenuate the lateral responses and can therefore be used in situations where stringent lateral stability is needed. © 2000 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
61.72.Qq Microscopic defects (voids, inclusions, etc.)
62.20.D- Elasticity

Scanning tunneling microscope measurements of the amplitude of vibration of a quartz crystal oscillator

B. Borovsky, B. L. Mason, and J. Krim

J. Appl. Phys. 88, 4017 (2000); http://dx.doi.org/10.1063/1.1289235 (5 pages) | Cited 37 times

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We report highly accurate measurements of the vibrational amplitude of a transverse shear mode quartz resonator, obtained by directly imaging the surface oscillatory motion with a scanning tunneling microscope. Amplitude measurements, performed over a range of resonator drive levels and quality factors, agree with theoretical predictions to within a factor of two. © 2000 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.30.Ng Oscillators, pulse generators, and function generators

Soliton interpretation of relation between driving force and velocity of interface motion in martensitic transformation

Yu Zhao, Jihua Zhang, and T. Y. Hsu (Xu Zuyao)

J. Appl. Phys. 88, 4022 (2000); http://dx.doi.org/10.1063/1.1288164 (4 pages) | Cited 3 times

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The relationship between the driving force for a martensitic transformation, ΔG, and the motion velocity of the martensite/parent interface, v, is derived for the Hamiltonian of a one-dimensional atomic chain with a nonlinear periodic potential model suggested by Peyrard and Remoissenet [Phys. Rev. B 26, 2886 (1982)] as ΔG=(2ma/π2)ω[C/math](4.026 92−2.931 92r−0.762 24r2), where m is the atomic mass, a the spacing of the one-dimensional lattice, r the shape parameter indicating the periodic lattice potential and C and ω are the characteristic velocity and frequency of the system, respectively. This result shows that the velocity of interface motion increases as the driving force increases. This equation is valid for different materials, regardless of whether the softening for martensitic transformation exists. © 2000 American Institute of Physics.
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81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
64.60.-i General studies of phase transitions

Microstructure of the nitride layer of AISI 316 stainless steel produced by intensified plasma assisted processing

J. C. Jiang and E. I. Meletis

J. Appl. Phys. 88, 4026 (2000); http://dx.doi.org/10.1063/1.1289476 (6 pages) | Cited 13 times

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Nitrided austenitic 316 stainless steel produced by intensified plasma assisted processing has been studied by transmission electron microscopy (TEM), high-resolution TEM, and image simulation techniques. Cross-sectional TEM studies showed that the nitride layer is composed of a single phase that was found to possess a simple cubic structure. This nitride is produced by introducing one N atom into one of the interstitial sites of the octahedra within the unit cell of the γ-austenite. The lattice constant of the nitrided simple cubic structure was determined to be a=3.78 Å, which is expanded by about 5.4% from that of austenite. Stacking faults, antiphase domains, and antiphase domain boundaries in the nitride layer were observed using dark-field and high-resolution TEM imaging. The evolution of the nitride phase seems to be preceded by lattice expansion and formation of stacking faults due to the presence of N and is consistent with the observed lattice constant reduction with depth. © 2000 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
61.72.Nn Stacking faults and other planar or extended defects
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.J- Point defects and defect clusters

Microstructure of epitaxial La0.7Ca0.3MnO3 thin films grown on LaAlO3 and SrTiO3

C. J. Lu, Z. L. Wang, C. Kwon, and Q. X. Jia

J. Appl. Phys. 88, 4032 (2000); http://dx.doi.org/10.1063/1.1290741 (12 pages) | Cited 50 times

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Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films of a thickness ∼170 nm were grown on (001) LaAlO3 (LAO) and (001) SrTiO3 (STO) substrates by pulsed laser deposition. Transmission electron microscopy and associated techniques have been applied to investigate the microstructures introduced by lattice mismatch that are responsible for the observed differences in properties between these two films. Numerous secondary phase rods were observed in both films. For the LCMO/LAO film, Ca-deficient secondary-phase rods originated in the film after a thickness of about 25 nm and were found to be responsible for relieving in-plane compressive stress during the island growth. In the case of STO substrate, however, almost all of secondary-phase rods initiated at the film–substrate interface. The lattice mismatch between LCMO and STO is relaxed into regions of good coherent fit separated by such secondary phases, possibly resulting from interfacial reaction. The two types of substrates lead to the formation of two different crystallographic domain structures in the LCMO films. The film on LAO exhibits an almost pure [110] out-of-plane texture with 90° domains in plane. In contrast, the film grown on STO consists of mixed domains of [001] and [110] orientations and is dominated by [001] texture. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
68.60.Bs Mechanical and acoustical properties

Ge composition in Si1−xGex films grown from SiH2Cl2/GeH4 precursors

K. Y. Suh and Hong H. Lee

J. Appl. Phys. 88, 4044 (2000); http://dx.doi.org/10.1063/1.1289515 (4 pages) | Cited 9 times

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A simple model for the Ge composition in Si1−xGex films grown from SiH2Cl2/GeH4 precursors is developed on the basis of adsorption and desorption kinetics for the intermediate temperature range (600 °C<T<900 °C). For this system, the solid phase composition of Ge, x, is related to the gas phase composition ratio of the two source gases, G, by x2/(1−x)=constant×G, which contrasts with the conventional relationship, x/(1−x)=constant×G, that is known for SiH4/GeH4 chemical vapor deposition. The proportionality constant depends not only on temperature but also on pressure. The model compares well with the experimental data in the literature. © 2000 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Hd Other semiconductors

Principles of strain relaxation in heteroepitaxial films growing on compliant substrates

G. Kästner and U. Gösele

J. Appl. Phys. 88, 4048 (2000); http://dx.doi.org/10.1063/1.1289810 (8 pages) | Cited 10 times

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In spite of various reports that the density of misfit dislocations threading a growing heteroepitaxial thin film can be considerably reduced by means of using a “compliant substrate,” the underlying physical mechanisms are not well understood. The common theoretical models suppose that the growing film can preferably relax in an elastic way by slipping on this kind of substrate. This idea, however, requires us to suppose macroscopic slip displacements. Such displacements are disregarded in the common theories and not reported to occur experimentally. This very doubtful free-slipping hypothesis has been used to establish a force balance (“strain partitioning”) between the growing film and the template layer below it and, consequently, to theoretically derive an enhanced critical thickness for the onset of slip of misfit dislocations. In the present article, more realistic mechanisms are discussed, including early plastic relaxation at a low film thickness where multiplicative interaction of dislocations hardly occurs. Possibilities for an enhanced elastic relaxation of the film in the case of Stranski–Krastanow island growth are discussed. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
62.20.F- Deformation and plasticity
61.72.Yx Interaction between different crystal defects; gettering effect

Mechanisms for Si dopant migration in molecular beam epitaxy AlxGa1−xAs

A. P. Mills, L. N. Pfeiffer, K. W. West, and C. W. Magee

J. Appl. Phys. 88, 4056 (2000); http://dx.doi.org/10.1063/1.1308073 (5 pages) | Cited 3 times

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Because of well-known surface segregation effects in molecular beam epitaxy growth, Si dopant atoms deposited as thin layers in AlxGa1−xAs typically become distributed over many atomic layers. We have measured the Si depth distributions in (100) and (311)A samples grown at temperatures between 420 and 655 °C, with Al fraction x=0, 0.1, and 0.32. The surface migration decay length Λ for a Si atom on a growing (100) surface is strongly temperature dependent but nearly independent of x, with Λ≈8 nm at 655 °C. The x=0(100) measurements show evidence for a minimum value Λ≈0.6 nm at low temperatures and a maximum value Λ≈8.5 nm at high temperatures. The data are in accord with a thermally activated surface segregation process with activation energy (1.8±0.4) eV acting in parallel with a temperature independent surface segregation mechanism. The (311)A surface shows Λ=(3.3±0.1) nm virtually independent of temperature for x=0. The Si decay length for the (311)A surface strongly increases with x, and for x=0.32 there is no significant difference in Λ for the (100) and (311)A surfaces. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation

Simulation of physical vapor deposition into trenches and vias: Validation and comparison with experiment

Peter L. O’Sullivan, Frieder H. Baumann, and George H. Gilmer

J. Appl. Phys. 88, 4061 (2000); http://dx.doi.org/10.1063/1.1310182 (8 pages) | Cited 5 times

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We have performed two-dimensional (2D) and three-dimensional (3D) (axisymmetric) numerical simulations of physical vapor deposition into high aspect ratio trenches and vias used for modern very large-scale integration interconnects. The topographic evolution is modeled using (continuum) level set methods. The level set approach is a powerful computational technique for accurately tracking moving interfaces or boundaries, where the advancing front is embedded as the zero level set (isosurface) of a higher dimensional mathematical function. We have validated both codes against analytic formulas for step coverage. First, we study the 2D case of long rectangular trenches including 3D out-of-plane target flux. The 3D flux can be obtained from molecular dynamics computations, and hence our approach represents a hybrid atomistic/continuum model. Second, we report results of axisymmetric 3D simulations of high aspect ratio vias, which we compare with experimental data for Ti/TiN barrier layers. We find that the simulations (using a cosine angular distribution for the flux from the target) overpredict bottom coverage in some cases by approximately 20%–30% for both collimated and uncollimated deposition, but in other cases provide a reasonably accurate comparison with experiment. © 2000 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Sz Deposition technology
02.60.Lj Ordinary and partial differential equations; boundary value problems
02.10.Ab Logic and set theory
85.40.Bh Computer-aided design of microcircuits; layout and modeling
02.70.Ns Molecular dynamics and particle methods
81.15.Cd Deposition by sputtering

Triboluminescence of alkaline earth aluminate polycrystals doped with Dy3+

Katsuhisa Tanaka, Koji Fujita, Tomohiro Taniguchi, Kazuyuki Hirao, and Tsuguo Ishihara

J. Appl. Phys. 88, 4069 (2000); http://dx.doi.org/10.1063/1.1290735 (6 pages) | Cited 3 times

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Triboluminescence spectra have been measured for polycrystalline (Sr,Ba)Al2O4 and (Sr,Ca)Al2O4 doped with Dy3+. Sr1−xBaxAl2O4:Dy3+ with x=0, 0.1, 0.2, and 0.4 and Sr0.9Ca0.1Al2O4:Dy3+ clearly exhibit triboluminescence caused by the 4f–4f transitions of Dy3+. In contrast, triboluminescence is barely observed in Sr0.8Ca0.2Al2O4:Dy3+ and Sr0.6Ca0.4Al2O4:Dy3+ although both of them show photoluminescence due to the 4f–4f transitions of Dy3+. For the Sr1−xBaxAl2O4:Dy3+ with x=0, 0.1, 0.2, and 0.4 and Sr0.9Ca0.1Al2O4:Dy3+, the compositional dependence of the relative integrated intensity of the emission lines is different between triboluminescence and photoluminescence spectra. We suggest two possibilities to explain this phenomenon; one of them is the self-absorption by Dy3+ in the case of triboluminescence, and the other is a situation that a strain is imposed on Dy3+, which brings about the triboluminescence due to the 4f–4f transitions. We speculate that the latter is the main cause for the difference between triboluminescence and photoluminescence spectra. © 2000 American Institute of Physics.
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78.60.Mq Sonoluminescence, triboluminescence
78.55.Hx Other solid inorganic materials
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