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15 May 1999

Volume 85, Issue 10, pp. 6957-7485

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A comprehensive thermodynamic analysis of native point defect and dopant solubilities in gallium arsenide

D. T. J. Hurle

J. Appl. Phys. 85, 6957 (1999); http://dx.doi.org/10.1063/1.370506 (66 pages) | Cited 41 times

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A detailed analysis of the role of charged native point defects in controlling the solubility of electrically active dopants in gallium arsenide is presented. The key roles of (a) positively charged arsenic vacancies (VAs+) in determining the doping range over which the solubility curve is linear and (b) multiply negative charged gallium vacancies (VGam−) determining annealing and diffusion behavior in n+ material are demonstrated. An equilibrium thermodynamic model based on these concepts is shown to accurately describe the doping behavior of Te, Zn, Sn, Ge, Si, and C and the formation and annealing of the deep level denoted EL2 (assumed to be the arsenic antisite defect AsGa) in melt- and solution-grown crystals. The model provides a much more comprehensive and accurate description of dopant solubility than the widely cited Schottky barrier model of bulk nonequilibrium dopant incorporation. It is unambiguously shown that partial autocompensation of donor dopants by the donor–gallium vacancy acceptor complex occurs for both group IV and group VI donor dopants. The deduced concentrations of arsenic vacancies grown into the crystal during melt growth are shown to be in excellent agreement with values determined by titration and by density/lattice parameter measurements. The obtained data are used to plot the Ga–As solidus. Due to the presence of charged native point defect species (notably, VAs+), the free-carrier concentration at high temperatures is greater than the intrinsic concentration. The calculated concentration is shown to be in excellent agreement with published experimental data. The utility of an equilibrium thermodynamic model in seeking an understanding of doping behavior under conditions of high supersaturation, such as occur with organometallic vapor phase epitaxy and molecular beam epitaxy, is demonstrated. Finally, some suggestions are made as to the likely native point defect equilibria in indium phosphide. © 1999 American Institute of Physics.
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61.72.J- Point defects and defect clusters
71.55.Eq III-V semiconductors
65.20.-w Thermal properties of liquids
65.40.gd Entropy
64.75.-g Phase equilibria
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Gh Other heat and thermomechanical treatments
66.30.J- Diffusion of impurities
61.72.Yx Interaction between different crystal defects; gettering effect
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Surface discharge and tracking phenomena induced on acrylonitrile-butadiene-styrene polymer dielectric material by acid rain

X. Wang and N. Yoshimura

J. Appl. Phys. 85, 7023 (1999); http://dx.doi.org/10.1063/1.370507 (7 pages) | Cited 1 time

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The discharge and tracking phenomena induced on the polymer dielectric materials by acid rain are investigated by the accelerated aging of acrylonitrile-butadiene-styrene copolymer in artificial rainwater in this article. Based on the investigation of acid rain, the artificial rainwater is chosen to agree well with the actual ingredients of precipitation. The influence of hydrophobicity degradation on the surface discharge and tracking is studied. The relations among the surface discharge, tracking, hydrophobicity, and microchemical structure and physical morphology of material are furthermore discussed. Experimental results show that the polymer dielectric materials suffer a large attack and degradation from acid rain. The dielectric surface degrades and becomes rough, and the hydrophobicity decreases so that the surface discharge and tracking may occur on them. © 1999 American Institute of Physics.  
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77.84.Jd Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
77.22.Jp Dielectric breakdown and space-charge effects
81.05.Qk Reinforced polymers and polymer-based composites

A unifying view on some experimental effects in tapping-mode atomic force microscopy

M. Marth, D. Maier, J. Honerkamp, R. Brandsch, and G. Bar

J. Appl. Phys. 85, 7030 (1999); http://dx.doi.org/10.1063/1.370508 (7 pages) | Cited 39 times

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Several experimental effects that occur in tapping-mode atomic force microscopy are examined: apparent hysteresis effects in force probes and frequency sweeps and distortions in imaging. It is found through examinations of the phase space that they can all be reduced to one common cause: the existence of more than one stable state of the tip vibration for certain parameters. It is shown that the experimental effects can be explained considering only the phase space under the assumption that measurement noise exists. Numerical simulations confirm the theoretical and experimental findings. © 1999 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
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Optical distortion and birefringence in a heated trigonal crystal rod

Charles E. Greninger

J. Appl. Phys. 85, 7037 (1999); http://dx.doi.org/10.1063/1.370509 (6 pages) | Cited 1 time

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Analytic expressions for the optical distortion and the fractional polarization purity loss when a perfectly plane, perfectly linearly polarized moderate power laser beam traverses a heated, rectangular trigonal class 3m, 32, or mathm crystal rod are given. The expressions are in terms of the crystal physical parameters of the rod, as well as the local stresses and strains that are developed in the rod by heating from the beam. When the crystal temperature variation is symmetric in the rod’s transverse coordinates, these expressions become analytic in the temperature variation and two simple temperature integrals. An example with a symmetric temperature variation in a lithium niobate crystal is given. © 1999 American Institute of Physics.  
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78.20.Fm Birefringence
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.79.-e Optical elements, devices, and systems
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Two-dimensional Z scan for arbitrary beam shape and sample thickness

P. Chen, D. A. Oulianov, I. V. Tomov, and P. M. Rentzepis

J. Appl. Phys. 85, 7043 (1999); http://dx.doi.org/10.1063/1.370510 (8 pages) | Cited 12 times

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A two-dimensional Z-scan technique has been developed using a two-dimensional charge-coupled device (CCD) detector to study the nonlinear optical properties and beam profile evolution within optical limiting devices. Using the split step beam propagation method, the far field pattern at each Z position can be calculated precisely for any arbitrary beam shape and sample thickness. A two-dimensional far field pattern is recorded by the CCD detector, and the evolution of the beam distribution inside the nonlinear optical medium can be obtained directly. This technique has been applied to study the nonlinear optical parameters and laser beam profiles in nonlinear liquids. We have used thin and thick samples and Gaussian, top-hat and split Gaussian beam distributions, and the experimental results agreed very well with the calculation. This technique also offers a simple and accurate means for optimizing the design of optical limiting devices. © 1999 American Institute of Physics.
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42.79.-e Optical elements, devices, and systems
42.79.Pw Imaging detectors and sensors
42.15.Eq Optical system design
02.60.Pn Numerical optimization
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Simulation of ZnSe-based self-electro-optic effect devices

D. Merbach, E. Schöll, and J. Gutowski

J. Appl. Phys. 85, 7051 (1999); http://dx.doi.org/10.1063/1.370511 (8 pages)

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We present computer simulations of self-electro-optic effect devices in different circuit environments, based on the quantum confined Stark effect in wide-gap materials with strong excitonic features. Our work is founded on a microscopic model of the electric field dependent absorption in ZnCdSe/ZnSSe quantum well structures, taking full account of Coulomb induced intersubband coupling and strong excitonic effects, which is essential for all wide-gap materials and distinguishes our theory from standard models of III–V compounds. Optical bistability and even multistability are predicted from the electro-optical and optical input–output characteristics for a wide range of operating conditions. The dependence upon the optical frequency, bias voltage, length of the waveguide and quantum well width, and possible optimization of the performance of the electro-optic modulator are discussed. © 1999 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.65.Pc Optical bistability, multistability, and switching, including local field effects
71.35.-y Excitons and related phenomena

Depth profiling of thermally inhomogeneous materials by neural network recognition of photothermal time domain data

C. Glorieux, R. Li Voti, J. Thoen, M. Bertolotti, and C. Sibilia

J. Appl. Phys. 85, 7059 (1999); http://dx.doi.org/10.1063/1.370512 (5 pages) | Cited 9 times

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Thermal conductivity depth profiles of thermally inhomogeneous materials are retrieved from the time dependence of the surface temperature after a flash illumination. A neural network method, which is trained to recognize the correlation between depth profiles and the surface temperature on the basis of many examples, is employed. Depth profiles retrieved from simulated noisy signals are shown and the average reconstruction errors are analyzed for different circumstances. © 1999 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
07.05.Mh Neural networks, fuzzy logic, artificial intelligence
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
44.05.+e Analytical and numerical techniques

Enhanced electron attachment to Rydberg states in molecular hydrogen volume discharges

L. A. Pinnaduwage, W. X. Ding, D. L. McCorkle, S. H. Lin, A. M. Mebel, and A. Garscadden

J. Appl. Phys. 85, 7064 (1999); http://dx.doi.org/10.1063/1.370513 (6 pages) | Cited 15 times

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We review recent studies on negative ion formation and studies in other areas that are relevant to the role of high-Rydberg states of H2 and H3 in hydrogen negative ion sources. Possible mechanisms for the formation of these excited states are discussed, including the formation of long-lived superexcited (core-excited) Rydberg states. Experimental evidence for negative ion formation via electron attachment to core-excited Rydberg states in a glow discharge apparatus is presented. An expression for the dissociative electron attachment rate constant for Rydberg molecules is derived based on electron capture by a Rydberg molecule due to polarization interaction. © 1999 American Institute of Physics.
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31.50.Df Potential energy surfaces for excited electronic states
34.80.Lx Recombination, attachment, and positronium formation
29.25.Ni Ion sources: positive and negative
52.80.Hc Glow; corona

[OH(X)] measurements by resonant absorption spectroscopy in a pulsed dielectric barrier discharge

C. Hibert, I. Gaurand, O. Motret, and J. M. Pouvesle

J. Appl. Phys. 85, 7070 (1999); http://dx.doi.org/10.1063/1.370514 (6 pages) | Cited 43 times

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Good understanding of the different phases of the plasma-chemistry involved is essential for the development of nonthermal plasma technologies for pollution control. These techniques are often based on the dissociation of parent gases to produce radicals that, in turn, decompose the toxic compounds. Our research concerns OH radical production in a pulsed dielectric barrier discharge (DBD). OH[A 2Σ+–X 2Π(0,0)] emission in argon-water vapor gas mixtures has been studied. Particular attention has been paid to the influence of water vapor partial pressure on the lifetime and intensity of emitted fluorescence in order to develop a pulsed DBD ultraviolet light source for spectroscopic investigation. This source was used to perform OH(X 2Π) time-resolved average absolute density measurements in other DBD discharges based on resonant absorption spectroscopy. This diagnostic has been validated in argon and air-water vapor mixtures. The temporal behavior of the density OH(X 2Π) radicals after a pulse discharge has been studied in argon and air with and without 500 ppm of trichloroethylene. This simple and inexpensive tool, compared to more sophisticated laser absorption or laser-induced fluorescence measurements for plasma investigation, is very useful for characterizing the OH radical potential for pollutant oxidation. © 1999 American Institute of Physics.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.80.-s Electric discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Radiation from an alternating current high-pressure mercury discharge: A comparison between experiments and model calculations

G. Hartel, H. Schöpp, H. Hess, and L. Hitzschke

J. Appl. Phys. 85, 7076 (1999); http://dx.doi.org/10.1063/1.370515 (13 pages) | Cited 25 times

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An alternating current (ac) high-pressure mercury arc has been experimentally investigated, and the results have been compared with model calculations. In the model, only radial dependencies are considered, and a careful treatment of the radiation transport is included. The absolutely measured side-on radiance in the visible and near ultraviolet spectral range can now be quantitatively reproduced by this model starting from the measured arc current. Agreement between the measured and calculated radial temperature profile can be obtained only by taking into account the time-dependent behavior of the investigated ac arc. The calculated field strengths agree with the measured ones only if more recent values of momentum transfer cross sections for the calculation of the electrical conductivity of mercury have been used. The time-dependent pressure in the discharge is determined via the electrical conductivity using Ohm’s law, the radial temperature distribution, and the electrical field strength. © 1999 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Cathode fall-dominated Ar discharge: Transient and steady-state experiments

B. M. Jelenković and A. V. Phelps

J. Appl. Phys. 85, 7089 (1999); http://dx.doi.org/10.1063/1.370516 (8 pages) | Cited 15 times

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The time-dependent transition of an Ar discharge from a low-current diffuse or Townsend discharge to a moderately high-current diffuse or abnormal discharge is investigated. We measure the current, voltage, and optical emission transients after a high-voltage pulse is superimposed on the direct current voltage of the low-current discharge. Emission transients are obtained near the cathode, at the end of the steady-state cathode fall, and near the anode. Spatial scans of absolute optical emission at the 750 and 811 nm lines are taken during the development of the cathode fall. These data show the initial growth of current and emission while the electric field is essentially uniform; the early minimum in emission near the anode marking the collapse of the electric field; the motion toward the cathode of the peak of emission; the drop in the discharge voltage, current, and emission during the approach to the steady-state; and the spatial distribution of emission from the steady-state discharge. Measurements are for pressure times electrode separations from 0.5 to 2 Torr cm and steady-state current densities of 500–100 μA/cm2, respectively. The initial rate of rise of the discharge voltage is roughly 100 V/μs and the times required to reach steady state are about 10 μs. © 1999 American Institute of Physics.
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52.80.Dy Low-field and Townsend discharges
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A small angle neutron scattering and Mössbauer spectrometry study of magnetic structures in nanocrystalline Ni3Fe

H. N. Frase, B. Fultz, S. Spooner, and J. L. Robertson

J. Appl. Phys. 85, 7097 (1999); http://dx.doi.org/10.1063/1.370517 (8 pages) | Cited 5 times

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Results are reported from small angle neutron scattering and Mössbauer spectrometry measurements on nanocrystalline Ni3Fe. The nanocrystalline materials were prepared by mechanical attrition and studied in the as-milled state, after annealing at 265 °C to relieve internal stress, and after annealing 600 °C to prepare a control sample comprising large crystals. The small angle neutron scattering (SANS) measurements were performed for a range of applied magnetic fields. Small differences were found in how the different samples reached magnetic saturation. From the SANS data obtained at magnetic saturation, we found little difference in the nuclear scattering of the as-milled material and the material annealed at 265 °C. Reductions in nuclear scattering and magnetic scattering were observed for the control sample, and this was interpreted as grain growth. The material annealed at 265 °C also showed a reduction in magnetic SANS compared to the as-milled material. This was interpreted as an increase in magnetic moments of atoms at the grain boundaries after a low temperature annealing. Both Mössbauer spectroscopy and small angle neutron scattering showed an increase in the grain boundary magnetic moments after the 265 °C annealing (0.2 and 0.4μB/atom, respectively), even though there was little change in the grain boundary atomic density. © 1999 American Institute of Physics.
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75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.50.Tt Fine-particle systems; nanocrystalline materials
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Cr Saturation moments and magnetic susceptibilities
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions

Porous silicon strain during in situ ultrahigh vacuum thermal annealing

D. Buttard, G. Dolino, C. Faivre, A. Halimaoui, F. Comin, V. Formoso, and L. Ortega

J. Appl. Phys. 85, 7105 (1999); http://dx.doi.org/10.1063/1.370518 (7 pages) | Cited 14 times

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In situ synchrotron radiation measurements of porous silicon (PS) strain have been performed during ultrahigh vacuum (UHV) thermal annealing. For a p+ sample, the initial lattice expansion shifts toward a contraction above 270 °C in relation with hydrogen desorption. For a p− sample, the strain variation is similar to that of a p+ one, but with effects five times larger: after hydrogen desorption, the contraction strain is large (>1.5%) and inhomogeneous. In both cases, most of these strains are elastic as an HF etch re-establishes the initial expansion with a narrow diffraction peak. For p+ samples, the lattice constant exhibited a slow variation during subsequent exposure to air due to a slow oxidation of the annealed porous samples. The origin of these strain variations is discussed in relation with the presence of hydrogen or oxide coverage. The observation of similar variations in other PS properties is also discussed. Finally, the absence of a strain effect during the introduction of water vapor in UHV is discussed as possibly due to a contamination of the PS sample by residual water during the long time passed under UHV at high temperature. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.05.Rm Porous materials; granular materials
61.43.Gt Powders, porous materials
61.72.Cc Kinetics of defect formation and annealing
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.65.Mq Oxidation

Mechanically alloyed Zr55Al10Cu30Ni5 metallic glass composites containing nanocrystalline W particles

J. Eckert, A. Kübler, and L. Schultz

J. Appl. Phys. 85, 7112 (1999); http://dx.doi.org/10.1063/1.370519 (8 pages) | Cited 57 times

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Composites based on the Zr55Al10Cu30Ni5 bulk metallic glass forming alloy, containing up to 17.5 vol % W particles were synthesized by mechanical alloying. Milling produces a metallic glass matrix with a homogeneous dispersion of nanoscale W particles. The composites exhibit almost the same thermal stability and no reduction of the supercooled liquid region compared to the particle-free metallic glass despite some small amount of dissolution of W into the glassy matrix. The viscosity in the supercooled liquid increases with increasing volume fraction of particles. This will be discussed with respect to the contribution of the particles as well as to changes in matrix composition and in the free volume of the material in the framework of the free volume model for viscous flow. Independent of the W content, the samples behave as moderately strong glasses. The viscous flow of the supercooled liquid is used to consolidate dense bulk samples. The Vickers hardness, HV, of the composites increases with increasing volume fraction of particles. It is suggested that both the matrix and the nanocrystalline particles contribute to the overall hardness of the composites. © 1999 American Institute of Physics.
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81.05.Ni Dispersion-, fiber-, and platelet-reinforced metal-based composites
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.07.-b Nanoscale materials and structures: fabrication and characterization

A deep level transient spectroscopy study of electron irradiation induced deep levels in p-type 6H–SiC

M. Gong, S. Fung, C. D. Beling, and Zhipu You

J. Appl. Phys. 85, 7120 (1999); http://dx.doi.org/10.1063/1.370520 (3 pages) | Cited 16 times

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1.7 MeV electron irradiation-induced deep levels in p-type 6H–SiC have been studied using deep level transient spectroscopy. Two deep hole traps are observed, which are located at EV+0.55 eV and EV+0.78 eV. They have been identified as two different defects because they have different thermal behaviors. These defects at EV+0.55 eV and EV+0.78 eV are annealed out at 500–200 °C, respectively, and are different from the main defects E1/E2, Z1/Z2 observed in electron irradiated n-type 6H–SiC. This indicates that new defects have been formed in p-type 6H–SiC during electron irradiation. © 1999 American Institute of Physics.
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71.55.Ht Other nonmetals
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Low temperature dependence of the elastic properties of Ti3SiC2

P. Finkel, M. W. Barsoum, and T. El-Raghy

J. Appl. Phys. 85, 7123 (1999); http://dx.doi.org/10.1063/1.370521 (4 pages) | Cited 13 times

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In this work, the Young’s, E, and shear, μ, moduli of Ti3SiC2 are measured ultrasonically in the 20–300 K temperature range. At room temperature, Young’s, ERT, and shear, μRT, moduli are 322±2 and 133.6±0.8 GPa, respectively. Poisson’s ratio is 0.2. Both moduli increase slowly with decreasing temperature and plateau out at temperatures below ≈130 K. A least square fit of the data yields, μ/μRT = 1−1.42×10−4(T−298) and E/ERT = 1−0.95×10−4(T−298) for temperatures greater than 140 K. The elastic Debye temperature is estimated to be 427 K, which is significantly lower than the value of 620 K calculated from heat capacity measurements. © 1999 American Institute of Physics.
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62.20.D- Elasticity
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
81.40.Jj Elasticity and anelasticity, stress-strain relations

Variable behavior of the current exponent in a microscopic nucleation model for electromigration

M. Tammaro and B. Setlik

J. Appl. Phys. 85, 7127 (1999); http://dx.doi.org/10.1063/1.370522 (3 pages) | Cited 5 times

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A microscopic nucleation model for electromigration on a lattice is proposed. The solution of the master equations for site occupancy produces a variable current exponent with 1<n<2. These results disprove previous claims that n=2 in nucleation models. We show that n=2 is the limiting behavior of all nucleation models and argue that physical regimes exist where the deviation from n=2 is significant. © 1999 American Institute of Physics.
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66.30.Qa Electromigration

Process-dependent thermal transport properties of silicon-dioxide films deposited using low-pressure chemical vapor deposition

Y. S. Ju and K. E. Goodson

J. Appl. Phys. 85, 7130 (1999); http://dx.doi.org/10.1063/1.370523 (5 pages) | Cited 23 times

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The volumetric heat capacity and thermal conductivity of silicon-dioxide films prepared using low-pressure chemical vapor deposition (LPCVD) are measured. The measurements employ the 3ω technique, which is extended to determine the thermal conductivity anisotropy and volumetric heat capacity of thin dielectric films. The thermal conductivity of the silicon-dioxide films exhibits a significant process dependence, which cannot be attributed to highly oriented microvoids or impurities. The volumetric heat capacity, in contrast, is largely independent of processing history provided that appropriate corrections are made to account for porosity and impurity contributions. This study provides evidence that process-dependent structural disorder strongly influences the thermal conductivity of amorphous films. © 1999 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
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
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.43.Er Other amorphous solids
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Study of interdiffusion in thin Fe film deposited on Si(111) by x-ray reflectivity and secondary ion mass spectrometry

S. Banerjee, G. Raghavan, and M. K. Sanyal

J. Appl. Phys. 85, 7135 (1999); http://dx.doi.org/10.1063/1.370524 (5 pages) | Cited 13 times

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We report on the effect of annealing on a thin Fe film deposited on a Si(111) substrate, using x-ray reflectivity and secondary ion mass spectrometry (SIMS) techniques. Using Fourier transform of the x-ray reflectivity data, we have estimated the layer thickness of the film. From the estimated thickness and critical value of the scattering vector qc obtained from the reflectivity data, an initial guess model of the electron density profile of the film is made. Using an iterative inversion technique, based on the Born approximation, with the obtained initial guess model, we have extracted the actual electron density profile of the film as a function of depth from the specular x-ray reflectivity data. On annealing, we observe interdiffusion of Fe and Si resulting in an increase in the thickness of the film. We have also carried out a SIMS measurement on the annealed sample to support the result of the annealing effect observed from the analysis of x-ray reflectivity data. The SIMS analysis indicates that the top of the film is rich in Si which has diffused from the substrate to the surface of the Fe film on annealing. © 1999 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Thermal desorption spectra of SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate/O3 atmospheric-pressure chemical vapor deposition

Degang Cheng, Koji Tsukamoto, Hiroshi Komiyama, Yuko Nishimoto, Noboru Tokumasu, and Kazuo Maeda

J. Appl. Phys. 85, 7140 (1999); http://dx.doi.org/10.1063/1.370525 (6 pages) | Cited 4 times

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SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate [TEOS, Si(OC2H5)4]/O3 atmospheric-pressure chemical vapor deposition (APCVD) were analyzed by thermal desorption spectra (TDS). The TDS results show that more silanols were incorporated during deposition and more water was absorbed during and after deposition in films deposited on Si substrates than on thermal oxide substrates. The latter result indicates that the elimination of water by-products is not the limiting step in TEOS/O3 APCVD. Based on the former result, a silanol model was proposed for the surface processes. On surfaces with a uniform and high density of silanol sites, or on which silanols readily form under TEOS/O3 APCVD conditions, the active silanol groups in the gas phase contribute to film formation and replenish silanol sites, resulting in continuous, high growth rates. On surfaces with few silanol sites, it is difficult to form silanol sites and the nonsilanol-containing polysiloxanes contribute to film formation, resulting in continuous, low growth rate. This model explains well both the surface dependence and the memory effect of TEOS/O3 APCVD. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
68.55.Nq Composition and phase identification
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies

Phase formation in Zr–Fe multilayers: Effect of irradiation

A. T. Motta, A. Paesano, R. C. Birtcher, M. E. Brückmann, S. R. Teixeira, and L. Amaral

J. Appl. Phys. 85, 7146 (1999); http://dx.doi.org/10.1063/1.370526 (13 pages) | Cited 2 times

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We have conducted a detailed in situ study of phase formation in Zr–Fe metallic multilayers using irradiation and thermal annealing. Metallic multilayers with near equiatomic and Fe-rich overall compositions and with repetition thicknesses ranging from 7.4 to 33 nm were either irradiated with 300 keV Kr ions at various temperatures (from 17 to 623 K) or thermally annealed at 773 K while being observed in situ. The kinetics of multilayer reaction were monitored by following the diffraction patterns. For near equiatomic samples, irradiation causes complete amorphization. The dose to amorphization increases in proportion to the square of the wavelength, indicating a process controlled by atomic transport. Amorphization was also achieved by 900 keV electron irradiation at 25 K showing that displacement cascades are not required. The critical dose to amorphization was independent of temperature below room temperature and decreased above room temperature. The activation energy for this second process is 0.17 eV. For the temperature range studied, diffraction from Zr disappears first, indicating that amorphization takes place in the Zr layer by atomic transport of Fe from the Fe layers. These results are consistent with a combination of simple ballistic mixing at low temperature and either simple diffusion or radiation-enhanced diffusion at higher temperatures. Thermal annealing of the equiatomic samples at 773 K produced the same reaction products with slower kinetics. Ion irradiation of Fe-rich samples did not cause complete amorphization and intermetallic compounds Zr3Fe and ZrFe2 were observed in longer wavelength samples. Amorphization of Fe-rich samples was more sluggish, likely because there was competition with formation of other phases. The reaction kinetics were not proportional to square of wavelength for Fe-rich samples, indicating a process that depends on more than atomic transport. Thermal annealing at 773 K of a long wavelength, 57% Fe sample resulted in intermetallic compounds Zr3Fe and ZrFe2 which amorphized during subsequent irradiation. The ease of amorphization of equiatomic samples relative to Fe-rich samples can be explained by a narrower, single minimum free energy curve for the amorphous phase. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Cc Kinetics of defect formation and annealing
65.20.-w Thermal properties of liquids
65.40.gd Entropy
61.80.Fe Electron and positron radiation effects
61.80.Jh Ion radiation effects
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Near-edge x-ray absorption fine structure and Raman characterization of amorphous and nanostructured carbon films

C. Lenardi, P. Piseri, V. Briois, C. E. Bottani, A. Li Bassi, and P. Milani

J. Appl. Phys. 85, 7159 (1999); http://dx.doi.org/10.1063/1.370527 (9 pages) | Cited 47 times

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Amorphous and nanostructured carbon films were grown by using two different techniques: ion sputtering and cluster beam deposition. The films were studied by near-edge x-ray absorption fine structure (NEXAFS) and Raman spectroscopy. Depending on the precursors, atoms, or clusters, the films are characterized by a different sp2/sp3 ratio which influences the mechanical and the electronic properties. Due to the sensitivities of NEXAFS (local order) and Raman (medium-range order), we have characterized and compared the structure of the films over different length scales. The complementarity of NEXAFS and Raman techniques for the characterization of disordered forms of carbon is here presented and discussed. We also present an original method of NEXAFS spectra calibration allowing a better determination of peak positions. © 1999 American Institute of Physics.
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61.43.Er Other amorphous solids
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
78.70.Dm X-ray absorption spectra
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.15.Cd Deposition by sputtering
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Steady-state, planar growth parameters in the reactive deposition of thin films

G. Carter

J. Appl. Phys. 85, 7168 (1999); http://dx.doi.org/10.1063/1.370528 (12 pages)

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A generalized model is developed which predicts the composition and growth rate of thin films when multiple atomic fluxes impinge onto a substrate and react chemically to form a composite film. The effects of simultaneous energetic ion irradiation which can mediate reaction rates and cause differential sputter removal of different film components are included and are shown to modify film composition and growth rate. A comparison of the model predictions with available experimental data is shown to give satisfactory agreement and it is demonstrated that two distinct cases of gas–solid and solid-state reactions can dominate and be distinguished, with theoretical analysis being more straightforward in the former case. © 1999 American Institute of Physics.
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81.15.Aa Theory and models of film growth
68.55.Nq Composition and phase identification
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Dv Composition, segregation; defects and impurities
81.15.Cd Deposition by sputtering
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.20.Pm Rate constants, reaction cross sections, and activation energies

Pd2Si-assisted crystallization of amorphous silicon thin films at low temperature

Seok-Woon Lee, Byung-Il Lee, Tae-Kyung Kim, and Seung-Ki Joo

J. Appl. Phys. 85, 7180 (1999); http://dx.doi.org/10.1063/1.370529 (5 pages) | Cited 14 times

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An ultrathin palladium layer was deposited on top of amorphous silicon films and the crystallization enhancement of the underlying amorphous silicon films was observed. The crystallization temperature was lowered down to 350 °C while that of intrinsic silicon films is around 600 °C. The degree of enhancement was found to be dependent on the thickness of the palladium layer as well as the annealing temperature. From the microstructure analysis, the formation of Pd2Si precipitates in the amorphous silicon was observed at the initial stage of crystallization and after further annealing, the crystallization of amorphous silicon was observed with the simultaneous split of the preformed Pd2Si precipitates into many small pieces. The mechanism of this abnormal phenomenon is discussed with the theory of epitaxial growth. © 1999 American Institute of Physics.
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81.05.Gc Amorphous semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria

Strain-induced surface morphology of slightly mismatched InxGa1−xAs films grown on vicinal (100) InP substrates

H. Dumont, L. Auvray, J. Dazord, V. Souliere, Y. Monteil, and J. Bouix

J. Appl. Phys. 85, 7185 (1999); http://dx.doi.org/10.1063/1.370530 (6 pages) | Cited 1 time

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A surface investigation by atomic force microscope of InP and slightly lattice-mismatched InGaAs epilayers grown by metalorganic vapor phase epitaxy shows the effect of strain on InGaAs/InP surface morphology. Epilayers were grown at 600 °C with arsine at 760 Torr. We could clearly observe the regular step/terrace-like feature of the vicinal surface morphology for InP and InGaAs lattice-matched epilayers. It is shown that the step flow mode appears with a step edge with regular spacing for lattice-matched epilayers. A crosshatch pattern, i.e., an array of perpendicular lines visible at the surface, were obtained for strain-relaxed InGaAs epilayers (∣(Δa/a)⊥∣>10−3) with an average separation of 1000–1500 nm. The detailed surface structure of the step edge presents a specific bending of terraces. The influence of step kinetics on the morphological stability of the surface will be illustrated. The relationship between the misfit dislocation network and anisotropic growth rate of the front step will be discussed. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
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