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1 Aug 1990

Volume 68, Issue 3, pp. 917-1409

Page 1 of 4 Pages Next Page | Jump to Page

The Cerenkov free‐electron laser for the relativistic electron beam with a slow rotating equilibrium

Sun‐Kook Kim, Duk‐In Choi, and Jeong‐Sik Choi

J. Appl. Phys. 68, 917 (1990); http://dx.doi.org/10.1063/1.346654 (7 pages) | Cited 1 time

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In a dielectric‐loaded waveguide a slow rotating equilibrium of a relativistic electron beam which interacts with the electromagnetic waves is investigated in a self‐consistent way. General dispersion relations for the fundamental transverse magnetic modes in the presence of the external magnetic field are derived using the cold fluid Maxwell equations and the appropriate boundary conditions. For slow space charge and slow cyclotron modes an algebraic equation is obtained from the dispersion relation by using a tenuous beam approximation. Solutions of the resulting equation are obtained for variations of several parameters, such as the external magnetic field, the dielectric constant, the thickness of the dielectric material, and the gap between beam and dielectric materials. With the beam‐dielectric gap satisfying the stability condition, the growth rate of the space charge and the slow cyclotron instabilities show the same behavior as previous results for the no gap case [IEEE Trans. Plasma Sci. PS‐17 576 (1989)]. Finally, emphasis in the analysis is given to the effect of the finite gap between the beam and dielectric and the comparison to the previous study of a no‐gap case. From this analysis it is also shown that as the gap width increases, the growth rate, ωic decreases due to the finite geometric effect related to the gap width.
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41.60.Cr Free-electron lasers
41.75.Ht Relativistic electron and positron beams
41.60.-m Radiation by moving charges

Anticipated improvement in laser beam uniformity using distributed phase plates with quasirandom patterns

R. Epstein and S. Skupsky

J. Appl. Phys. 68, 924 (1990); http://dx.doi.org/10.1063/1.346655 (8 pages) | Cited 6 times

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The uniformity of focused laser beams, that has been modified with randomly phased distributed phase plates [C. B. Burckhardt, Appl. Opt. 9, 695 (1970); Kato and Mima, Appl. Phys. B 29, 186 (1982); Kato et al., Phys. Rev. Lett. 53, 1057 (1984); LLE Rev. 33, 1 (1987)], can be improved further by constructing patterns of phase elements which minimize phase correlations over small separations. Long‐wavelength nonuniformities in the intensity distribution, which are relatively difficult to overcome in the target by thermal smoothing and in the laser by, e.g., spectral dispersion [Skupsky et al., J. Appl. Phys. 66, 3456 (1989); LLE Rev. 36, 158 (1989); 37, 29 (1989); 37, 40 (1989)], result largely from short‐range phase correlations between phase plate elements. To reduce the long‐wavelength structure, we have constructed phase patterns with smaller short‐range correlations than would occur randomly. Calculations show that long‐wavelength nonuniformities in single‐beam intensity patterns can be reduced with these masks when the intrinsic phase error of the beam falls below certain limits. We show the effect of this improvement on uniformity for spherical irradiation by a multibeam system.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Mv Dye lasers

Optical step frequency reflectometer

K. Iizuka, Y. Imai, A. P. Freundorfer, R. James, R. Wong, and S. Fujii

J. Appl. Phys. 68, 932 (1990); http://dx.doi.org/10.1063/1.347179 (5 pages) | Cited 14 times

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The carrier generated by a solid‐state laser can be frequency shifted by a significant amount. This fact was exploited to implement a high‐resolution optical‐fiber fault locator. A resolution of 4 mm was achieved. Compared to the resolution of a frequency‐domain reflectometer that shifts the frequency of the AM modulation of the light, the proposed fault locator has a resolution about 1000 times better. The potential of developing the proposed reflectometer into an ultrahigh‐resolution integrated optics fault locator is also discussed. UFaipxr
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42.81.Cn Fiber testing and measurement of fiber parameters
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Scanning electron microscopy investigations of the initial degradation mechanism of GaAs quantum well lasers grown on silicon substrates

R. B. Martins, P. Henoc, B. Akamatsu, G. Bartenlian, and M. N. Charasse

J. Appl. Phys. 68, 937 (1990); http://dx.doi.org/10.1063/1.346656 (6 pages) | Cited 5 times

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Cathodoluminescence and electron beam induced current are used to investigate the degradation of the graded‐index separate‐confining heterostructure laser devices grown on silicon substrates. By examining the evolution of the microscopic electronic properties of these devices during operation or under electron beam bombardment, a better understanding of the initial mechanism of degradation in a laser device results: it is concluded from this study that the degradation starts in the vicinity of the p‐n junction before attaining the active layer or the formation of dark line defects. This starting of degradation is attributed to the point‐defect migration or coupling in the space‐charge region. The built‐in electrical field plus the nonradiative recombination of excesses carriers seems to be related to these phenomena. It is also pointed out that the technological processes for device fabrication have a strong influence on the degradation mechanism.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Tunable lasers at 1080 nm for helium optical pumping

L. D. Schearer and Padetha Tin

J. Appl. Phys. 68, 943 (1990); http://dx.doi.org/10.1063/1.346657 (7 pages) | Cited 11 times

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We describe the current status of tunable, cw, solid‐state lasers in the infrared region of the spectrum which may be tuned to the helium resonance transition near 1083 nm. The principal use for these laser devices is the optical pumping of 3He and 4He atoms via the 23S1 metastable state. The tunable lasers we have examined include Nd3+‐doped YAlO3, LaxNd1−xMgAl11O19 (x ∼0.15), Nd:LiNbO3, and Nd:silica glass fibers. Power outputs from these lasers range from a milliwatt to more than 1 W at the helium transition. Laser emission bandwidths range from less than 40 MHz (single‐mode operation) to several GHz. Applications include magnetometry, dense nuclear targets, and polarized electron beams.
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42.60.By Design of specific laser systems
42.55.-f Lasers

A high power, tunable, arc‐lamp pumped Nd‐doped lanthanum‐hexaluminate laser

Padetha Tin and L. D. Schearer

J. Appl. Phys. 68, 950 (1990); http://dx.doi.org/10.1063/1.346658 (4 pages) | Cited 8 times

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An LNA (Nd‐doped lanthanum‐hexaluminate) crystal has been pumped with a cw, krypton arc lamp in a commercial Nd:YAG cavity. The cw output power greater than 6 W is obtained in a 28‐cm long, plane mirror cavity. The free‐running wavelength is near 1083 nm and has a width of about 0.8 nm. Inserting a 0.25 mm thick, uncoated solid etalon in the cavity permits the laser output to be continuously tuned from 1082 to 1084 nm by tilting the etalon. The laser bandwidth is reduced to below 0.016 nm. Over 3 W are obtained at the helium resonance transition. The maximum power output is limited by severe thermal lensing effects in the LNA crystal. The single, arc‐lamp pump is operated at less than 70% of its maximum rated current; thus, substantial increases in the power output can be expected if crystal quality can be improved.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

A novel model of ‘‘new donors’’ in Czochralski‐grown silicon

J. J. Qian, Z. G. Wang, S. K. Wan, and L. Y. Lin

J. Appl. Phys. 68, 954 (1990); http://dx.doi.org/10.1063/1.346659 (4 pages) | Cited 7 times

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A new model of ‘‘new donors’’ is presented, based on electrical, infrared measurements, transmission electron microscopy, and high‐resolution electron microscopy observations on Czochralski‐grown silicon single crystals containing ‘‘new donors.’’ In this model, the electrical activity of ‘‘new donors’’ originates from the uncoordinated Si dangling bonds on small dislocation loops resulting from oxygen precipitation. In comparison with other models, the present model can better explain the experimental results of the heat treatment Czochralski‐grown Si wafers.
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61.72.Bb Theories and models of crystal defects
61.72.jd Vacancies
61.72.jj Interstitials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors

Reconstruction of three‐dimensional range distributions by a modified tomographic technique

D. Fink, M. Müller, and L. Wang

J. Appl. Phys. 68, 958 (1990); http://dx.doi.org/10.1063/1.346660 (7 pages) | Cited 13 times

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First, an overview of the present state of art of imaging of three‐dimensional particle (or damage) distributions in the field of ion implantation is given. Usually, the direct measurement of three‐dimensional distributions in the field of ion implantation is restricted to cases when the impinging ion beam diameter is small against the size of the corresponding distributions, i.e., to ion energies above typically 100 MeV and to microbeams of a few μm diameter. To gain information also for lower ion energies without the restriction in the beam diameter, a modified tomographic reconstruction technique has been developed recently by us and is described here in detail. Three‐dimensional distributions are reconstructed from a number of one‐dimensional depth profiles, implanted under various angles. Competing algorithms for the solution are discussed. For the mathematical technique chosen, some consistency tests are presented. Good accuracy of a sufficient number of input profiles is vital for the quality of the three‐dimensional reconstruction
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61.72.uf Ge and Si
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.80.Jh Ion radiation effects
61.72.up Other materials

Schlieren measurements of the hydrodynamics of excimer laser ablation of polymers in atmospheric pressure gas

Peter L. G. Ventzek, Ronald M. Gilgenbach, Jeffrey A. Sell, and David M. Heffelfinger

J. Appl. Phys. 68, 965 (1990); http://dx.doi.org/10.1063/1.346661 (4 pages) | Cited 34 times

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Pulsed schlieren photography and fast helium‐neon laser deflection are used to study the hydrodynamics of laser ablation of polyethyleneterephthalate and polymethylmethacrylate by pulsed KrF (248 nm) radiation in atmospheric air, Ar and N2. Schlieren measurements show the evolution of shock waves, sound waves, and reduced‐density, hot gas plumes. A transition from sound to shock at the ablation threshold for both polymers is observed. The shock velocity of PET tends to approach agreement with blast wave theory at fluences higher than 1 J/cm2. Plumes in air are consistently larger than those produced in Ar and N2 (at fluences below 5 J/cm2) suggesting that combustion may occur. Laser deflection measurements for PET at 150 mJ/cm2 indicate a plume density of 0.6 kg/m3 (50% atmospheric density).
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
47.35.-i Hydrodynamic waves
47.40.Nm Shock wave interactions and shock effects
07.68.+m Photography, photographic instruments; xerography

Reproducible leaky tube diffusion of Cd in InP at 500 °C

C. B. Wheeler, R. J. Roedel, Randall W. Nelson, Stephan N. Schauer, and Peter Williams

J. Appl. Phys. 68, 969 (1990); http://dx.doi.org/10.1063/1.346662 (4 pages) | Cited 2 times

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We report for the first time the successful application of the leaky tube method to diffuse elemental Cd into InP at 500 °C. Specular surfaces are consistently realized while additional phosphorus in the ambient is not required. Free‐carrier concentration profiles and junction depths were experimentally determined for times ranging from 20 min to 21/2 h. A reproducible surface concentration of ionized acceptors is ∼1×1018 cm−3 (T=300 K). A concentration dependent diffusion coefficient ranging from approximately 1×10−14 to 1×10−10 cm2/s is calculated for the conditions under investigation. Secondary ion mass spectroscopy analysis shows the atomic Cd concentration to be very similar to that of the ionized acceptors, with the atomic surface concentration approximately two times greater than the surface hole concentration.
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61.72.U- Doping and impurity implantation
61.72.Yx Interaction between different crystal defects; gettering effect
66.30.J- Diffusion of impurities

Texture formation in polycrystalline diamond films

Ch. Wild, N. Herres, and P. Koidl

J. Appl. Phys. 68, 973 (1990); http://dx.doi.org/10.1063/1.346663 (6 pages) | Cited 170 times

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Structure and morphology of polycrystalline diamond films prepared by chemical vapor deposition (CVD) have been studied using x‐ray texture analysis, angle‐resolved optical reflection, and scanning electron microscopy. The films under investigation exhibit a pronounced 110 fiber texture, i.e., a preferential alignment of {110} planes perpendicular to the growth direction. By thinning a 180‐μm‐thick CVD diamond film in an oxygen discharge the dependence of the degree of 110 texture on the film thickness has been investigated. It was found that the crystals formed at the beginning of the film growth are randomly oriented, and that a preferential orientation of {110} planes develops with increasing film thickness. Computer simulations show that this behavior can be explained by evolutionary selection, i.e., competing growth of differently oriented crystals, which implies that 〈110〉 is the direction of fastest growth. In addition, angle‐resolved optical reflection and scanning electron micrographs show that the surface of the diamond films consists of {111} faces. Possible explanations for these findings are discussed.
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81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Crystal size dependence for impact initiation of cyclotrimethylenetrinitramine explosive

R. W. Armstrong, C. S. Coffey, V. F. DeVost, and W. L. Elban

J. Appl. Phys. 68, 979 (1990); http://dx.doi.org/10.1063/1.346664 (6 pages) | Cited 54 times

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The dislocation pile‐up avalanche model is used to explain the crystal size dependence for hot spot‐controlled initiation of chemical decomposition in cyclotrimethylenetrinitramine crystals subjected to drop‐weight impact testing. Deformation‐induced temperature rises, hot spot sizes, and lifetimes are related to previously reported values for direct thermal decomposition. A reasonable chemical reaction yield is estimated from available kinetic data.
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62.20.F- Deformation and plasticity
62.20.M- Structural failure of materials
61.72.Lk Linear defects: dislocations, disclinations

Effects of isovalent substitutions on lattice softening and transition character of BaTiO3 solid solutions

J. N. Lin and T. B. Wu

J. Appl. Phys. 68, 985 (1990); http://dx.doi.org/10.1063/1.346665 (9 pages) | Cited 29 times

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The transition character of paraelectric‐to‐ferroelectric phase transition and its relation to lattice soft‐mode behavior in the solid solutions of (Ba,Sr)TiO3, (Ba,Ca)TiO3, Ba(Ti,Zr)O3, and Ba(Ti,Sn)O3 were investigated by the measurements of dielectric constants in the temperature range from −30 to 150 °C, and x‐ray line breadth of 100, 110, and 111 Bragg reflections at temperatures above the transition point. From the result of dielectric measurement, it was found that the specimens containing Ti‐site substituents have shown a diffuse phase transition character, whereas those having Ba‐site substituents have preserved a sharp phase transition. It was also noted from the change of line breath of Bragg reflections that for the solutions of Ba(Ti,Zr)O3 and Ba(Ti,Sn)O3, the high dynamic strain at the 〈1 0 0〉 axis, induced from the soft‐mode of lattice vibration, become repressed when a large amount of solutes is contained, but for the solutions of (Ba,Sr)TiO3 and (Ba,Ca)TiO3, it is recovered at temperatures near the transition point. Moreover, the dynamic strain at the 〈1 1 1〉 axis can be rapidly repressed by the addition of Ti‐site substituents. The different effects on the dynamic strains are attributed to the disparate distortions of oxygen octahedra in the perovskite lattice, induced by the solutes of different site substitution. It is also believed that the influence on the soft‐mode of lattice vibration has caused the different phase transition characters of the four BaTiO3 solid solutions.
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77.80.B- Phase transitions and Curie point
77.90.+k Other topics in dielectrics, piezoelectrics, and ferroelectrics and their properties (restricted to new topics in section 77)
64.70.K- Solid-solid transitions

Numerical modeling of microscopic fluid distribution in porous media

Rosemary Knight, Alice Chapman, and Michael Knoll

J. Appl. Phys. 68, 994 (1990); http://dx.doi.org/10.1063/1.346666 (8 pages) | Cited 7 times

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Three numerical methods have been developed to model the equilibrium distribution of fluid phases in a multiphase saturated porous medium. The basic assumption made is that the distribution of phases is governed by the static interfacial free energy of the system, such that the equilibrium phase distribution corresponds to a minimum in the total interfacial free energy of the system. The example of determining the distribution of water vapor and liquid water in 2D numerical models of the pore space in a rock is considered. Starting with a numerical model of the pore space, the objective of each method is to obtain the minimum energy configuration of water vapor and liquid water in the pore space for some set level of water saturation. Two of the methods are simple and computationally fast methods that can produce fluid distributions close to, or matching, the equilibrium configuration. These methods can, however, produce metastable configurations due to the simplistic nature of the algorithms. The third method applied to this problem is a simulated annealing method. This method consistently produced the lowest possible energy configuration. It is concluded that simulated annealing can be successfully used to numerically model fluid distribution in multiphase saturated porous media.
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47.56.+r Flows through porous media

O2 and CO2 glow‐discharge‐assisted oxygen transport through Ag

R. A. Outlaw

J. Appl. Phys. 68, 1002 (1990); http://dx.doi.org/10.1063/1.346734 (3 pages) | Cited 1 time

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The permeation of oxygen through Ag normally occurs by a sequence of steps which include the initial dissociative adsorption of molecular oxygen at the upstream surface, the dissolution of the atoms into the bulk, and the subsequent migration of the atoms between octahedral sites of the lattice until they arrive at the vacuum interface downstream. The dissociative adsorption step, however, proceeds slowly, as indicated by the low sticking coefficient of O2 on Ag(10−6–10−3). The application of a dc field in 0.5 Torr of O2 (E/n∼10−14 V cm2) on the upstream side of a Ag membrane generated gas phase atomic oxygen that substantially enhanced the transport. The transport flux was observed to increase from a value of 4.4×1013 cm−2 s−1 to a glow discharge value of 2.83×1014 cm−2 s−1 at a membrane temperature of 650 °C. This suggests that the dissociative adsorption step limits the supply of oxygen atoms to the upstream side of the membrane. When the upstream O2 was replaced by an equal pressure of CO2, only a small permeation signal was observed, but the application of the glow discharge substantially increased the transport flux from 3.25×1012 cm−2 s−1 to 1.74×1014 cm−2 s−1. This method of separating O2 from a CO2 environment may be a possible mechanism for providing a supply of oxygen for astronauts in a manned mission to Mars.
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47.70.Fw Chemically reactive flows
66.30.-h Diffusion in solids
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Diffusion of hydrogen in post‐plasma‐hydrogenated amorphous silicon film

Minoru Nakamura and Yutaka Misawa

J. Appl. Phys. 68, 1005 (1990); http://dx.doi.org/10.1063/1.346735 (4 pages) | Cited 7 times

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In order to elucidate the diffusion mechanism of hydrogen in post‐plasma‐hydrogenation of amorphous silicon (a‐Si) film prepared by chemical vapor deposition (CVD), the change in the hydrogen depth profiles with plasma exposure time and with successive hydrogenation of hydrogen isotopes were measured by secondary ion mass spectrometry and infrared absorption. The post‐hydrogenation process of the CVD a‐Si film is explained by a model composed of fast diffusion (small activation energy) of atomic hydrogen through weakly bound sites such as interstitials, its capture by reactive sites such as weak SiSi bonds and dangling bonds, and an exchange between weakly bound and bonded hydrogens.
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66.10.C- Diffusion and thermal diffusion
66.30.J- Diffusion of impurities
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Dynamic approach for finding effective elastic and piezoelectric constants of superlattices

E. Akçakaya, G. W. Farnell, and E. L. Adler

J. Appl. Phys. 68, 1009 (1990); http://dx.doi.org/10.1063/1.346736 (4 pages) | Cited 10 times

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A dynamic approach is presented for determining a set of equivalent elastic, piezoelectric, and permittivity constants for a superlattice consisting of a periodic multilayer of anisotropic materials. The objective is to predict the acoustic properties of such a periodic structure in the long‐wavelength (low‐frequency) limit. It is shown that the acoustic wave propagation properties for propagation in any plane defined by an arbitrary direction and the superlattice axis are contained in a 6×6 system matrix requiring only a subset of at most 29 material constants (from a total of 46) for its construction. The computation of an equivalent system matrix for a superlattice is demonstrated and the manner of obtaining the equivalent density, six permittivities, 21 stiffness, and 18 piezoelectric constants is given.
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62.20.D- Elasticity
62.30.+d Mechanical and elastic waves; vibrations
77.22.Ch Permittivity (dielectric function)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Strain relaxation of GaAs layers grown on heavily In‐doped substrates by organometallic vapor phase epitaxy

Shunro Fuke, Katsumi Mori, Kazuhiro Kuwahara, and Tetsuji Imai

J. Appl. Phys. 68, 1013 (1990); http://dx.doi.org/10.1063/1.346737 (5 pages) | Cited 1 time

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Heavily Zn‐doped epitaxial layers have been grown on In‐doped GaAs substrates by organometallic vapor phase epitaxy in order to investigate the strain relaxation mechanism and hence the nucleation and propagation of misfit dislocations. Samples doped with Zn higher than 3×1020 cm−3 still show a perfectly strained state beyond the coherent length obtained for undoped GaAs epilayers. Hence, epilayers having a higher Zn concentration seem to have a higher activation barrier for nucleation and propagation of misfit dislocations. Furthermore, for the Zn‐doped/undoped/substrate(In‐doped) double‐epilayer structure, the elastic strain in the heavily Zn‐doped layer is found to be unrelaxed, regardless of the increase in the thickness of the Zn‐doped upper layer. This result suggests dislocation generation at the growing surface and glide along the {111} slip planes into the heterointerface.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.60.Bs Mechanical and acoustical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Mechanical properties of a‐C:H films prepared by plasma decomposition of C2H2

X. Jiang, K. Reichelt, and B. Stritzker

J. Appl. Phys. 68, 1018 (1990); http://dx.doi.org/10.1063/1.346738 (5 pages) | Cited 47 times

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Diamondlike a‐C:H films have been deposited by decomposition of C2H2. By the combination of Brillouin scattering and the ultralow load indentation technique, the following mechanical properties of the films were studied: the microhardness H, the Young’s modulus E, the shear modulus μ, and the Poisson’s ratio ν. From the measured data of mass density, hydrogen concentration, and the ratio of sp3/sp2 bonds the filling factors of these films were calculated. The results show that the hardness, Young’s modulus, and shear modulus of these films depend strongly on the volume concentration of voids and are directly proportional to the filling factor.
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68.55.Nq Composition and phase identification
62.20.D- Elasticity

Optical characterization of Cd1−xMnxTe epilayers grown by liquid‐phase epitaxy

Y. R. Lee, R. G. Alonso, E.‐K. Suh, A. K. Ramdas, L.‐X. Li, and J. K. Furdyna

J. Appl. Phys. 68, 1023 (1990); http://dx.doi.org/10.1063/1.346739 (6 pages) | Cited 3 times

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Epilayers of Cd1−xMnxTe grown on CdTe substrates by liquid‐phase epitaxy (LPE) are characterized by x‐ray, modulated (piezo‐ or photo‐) reflectivity, and Raman spectroscopy. The epilayers are found to be of excellent structural quality, having sharp excitonic signatures in the reflectivity spectra and highly uniform Mn concentrations. Intentional introduction of In donors during LPE growth of Cd1−xMnxTe has been verified by spin‐flip Raman signals which show large Raman shifts with a Brillouin function behavior characteristic of donors in diluted magnetic semiconductors. During the LPE growth we also encountered the formation of large‐area, free‐standing platelets of Cd1−xMnxTe. They have been similarly characterized with x‐rays, as well as modulation and Raman spectroscopy.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.30.Fs III-V and II-VI semiconductors
78.20.Ls Magneto-optical effects

Effect of substrate temperature on recrystallization of plasma chemical vapor deposition amorphous silicon films

Kenji Nakazawa and Keiji Tanaka

J. Appl. Phys. 68, 1029 (1990); http://dx.doi.org/10.1063/1.346740 (4 pages) | Cited 47 times

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The effect of substrate temperature on the recrystallization of plasma chemical vapor deposition amorphous silicon films is investigated. The grain size of polycrystalline silicon films recrystallized at 600 °C increases as the substrate temperature decreases. The enlargement in the grain size is attributed to the decrease in the nucleation rate. The nucleation rate is suppressed by an increase in structural disorder of the Si network. Electrical properties of recrystallized films are improved by the increase in the grain size.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Rs Electrical and magnetic properties related to treatment conditions

A transmission electron microscopy study of low‐temperature reaction at the Co‐Si interface

P. Ruterana, P. Houdy, and P. Boher

J. Appl. Phys. 68, 1033 (1990); http://dx.doi.org/10.1063/1.346741 (5 pages) | Cited 69 times

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An efficient preparation method, which provides wedge‐shaped cross‐section transmission electron microscopy samples, has been developed. It was then used to investigate the structure of as‐deposited cobalt multilayers on silicon substrates by rf plasma sputtering. It was found that an extended reaction takes place between Co and Si probably during the deposition. The cobalt atoms react with the silicon substrate to form an amorphous silicide layer. When the deposited layer is <3 nm thick, it entirely reacts with the substrate and can form an amorphous silicide as large as 5 nm. Above 4–5 nm thickness, growth of Co crystallites comes in competition with the formation of the amorphous silicide and limits it to 2 nm. The composition of this amorphous silicide is estimated to be Co2Si. In Co/C multilayers, the reactivity between the two materials is negligible, and the coalescence thickness of cobalt is 2–3 nm. At 2 nm, the cobalt layers are noncontinuous and very rough, whereas at 3 nm the critical thickness for crystalline nuclei coalescence has already been reached. The cobalt layers are then polycrystalline and have a reasonable roughness.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.65.-b Surface treatments
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
81.15.Cd Deposition by sputtering

High‐quality molecular‐beam epitaxial regrowth of (Al,Ga)As on Se‐modified (100) GaAs surfaces

F. S. Turco, C. J. Sandroff, D. M. Hwang, T. S. Ravi, and M. C. Tamargo

J. Appl. Phys. 68, 1038 (1990); http://dx.doi.org/10.1063/1.346742 (5 pages) | Cited 7 times

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It is shown that high‐quality molecular‐beam epitaxial (MBE) regrowth of (Al,Ga)As on GaAs can be achieved by chemically passivating the GaAs surface ex situ prior to regrowth with aqueous selenium reagents. Reflection high‐energy electron diffraction intensity oscillations show the bidimensional character of the regrowth and high‐resolution transmission electron microscopy reveals defect‐free regrown interfaces. Photoluminescence intensity from the Se‐treated GaAs surfaces on which Al0.5Ga0.5 As is regrown rivals that from an all in situ grown AlGaAs/GaAs interface. The high quality of these regrown interfaces could be attributed to the thermally and chemically stable selenium and oxygen phases that remain bound to GaAs under MBE conditions.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.-b Surface treatments
85.40.Ls Metallization, contacts, interconnects; device isolation
78.55.Cr III-V semiconductors

A thermodynamic approach for interpreting metallization layer stability and thin‐film reactions involving four elements: Application to integrated circuit contact metallurgy

A. S. Bhansali, R. Sinclair, and A. E. Morgan

J. Appl. Phys. 68, 1043 (1990); http://dx.doi.org/10.1063/1.346743 (7 pages) | Cited 22 times

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We propose a means of constructing simplified quaternary phase diagrams based on a thermodynamic approach using known and estimated data for Gibbs free energy of formation. Isothermal, isobaric sections of the condensed phase diagrams are built up as tie lines, tie planes, and tie tetrahedra (representing two‐, three‐, and four‐phase equilibrium, respectively) in a regular tetrahedron. This extends the now well‐established methodology for ternary systems described, for instance, by Beyers [J. Appl. Phys. 56, 147 (1984); Mat. Res. Soc. Symp. Proc. 47, 143 (1985)]. The procedure is illustrated by reference to Ti‐Si‐N‐O, Al‐Si‐N‐O, Ti‐Al‐Si‐N and Ti‐Al‐Si‐O, systems which are relevant to interactions occurring at various interfaces during the formation of contacts in integrated circuits. These phase diagrams are then used to predict the stability of—or reactions in—metallization layers and thin‐film systems involving four elements. In addition, a method is suggested to estimate unknown free energies of formation from observations of thin‐film reactions and stability.
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68.35.Rh Phase transitions and critical phenomena
68.60.Dv Thermal stability; thermal effects
68.35.Md Surface thermodynamics, surface energies

Recrystallization and grain growth phenomena in polycrystalline Si/CoSi2 thin‐film couples

Stefan Nygren and Stefan Johansson

J. Appl. Phys. 68, 1050 (1990); http://dx.doi.org/10.1063/1.346744 (9 pages) | Cited 23 times

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This paper presents high‐temperature effects on CoSi2/polycrystalline silicon (poly‐Si) bilayers, intended for metal‐oxide‐semiconductor gate applications. Both rapid thermal annealing and conventional furnace annealing were utilized for the investigation. At temperatures above 700 °C the structure breaks down due to silicon recrystallization within the silicide and simultaneous silicide growth into the polycrystalline silicon film. Recrystallized silicon adopts the silicide texture and this process terminates when the entire polysilicon layer is consumed. After completion the layer configuration is inverted, i.e., the silicide is adjacent to the gate oxide and covered with elemental silicon at the surface. This surface layer consists of large grains with few crystal defects, very different from the columnar structure of the as‐deposited silicon. With further annealing, grain growth in both phases continues, and each grain will ultimately extend from the oxide interface to the free surface. Lateral grain dimensions are typically a few times the total film thickness at this stage. Silicon recrystallization in the silicide layer can be suppressed if the polysilicon is doped with phosphorus prior to metal deposition, or the phenomenon can be alleviated by an arsenic or boron implantation into the silicide.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.40.Gh Other heat and thermomechanical treatments
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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