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15 Jun 1986

Volume 59, Issue 12, pp. 3945-4191

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Thermal, fracture, and laser‐induced decomposition of pentaerythritol tetranitrate

W. L. Ng, J. E. Field, and H. M. Hauser

J. Appl. Phys. 59, 3945 (1986); http://dx.doi.org/10.1063/1.336743 (8 pages) | Cited 7 times

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This paper describes a study of the decomposition of pentaerythritol tetranitrate (PETN) using a high‐resolution time‐of‐flight mass spectrometer. The decomposition was induced by fracturing single crystals and by laser irradiation. In the fracture experiments, the energy input was varied from the lowest level necessary to produce smooth cleavage surfaces to high‐energy loading which produced rough conchoidal fracture surfaces. In the laser experiments, a ruby laser was used in both normal and Q‐switched modes, and again the energy input was varied. For all the various experiments, the reaction products were analyzed and reaction schemes are proposed. It is shown that low‐energy fracture causes decomposition which follows the same reaction pathway as that induced thermally, with initial failure at the RO‐NO2 bond. However, high‐energy fracture results in the breaking of the C‐C bonds. Two reaction pathways were observed with the laser irradiation. The first is the normal thermal process, but evidence was also found for failure at the R‐ONO2 bond. The reaction continued for several milliseconds after the end of the laser pulse, suggesting a ‘‘partial’’ ignition of the explosive. In other experiments, the conditions for laser initiation of PETN in vacuum were investigated. Explosion occurred when Q‐switched pulses of 1 J energy were applied to a molten layer of PETN.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.33.Vx Reactions in flames, combustion, and explosions
82.20.Hf Product distribution
62.20.M- Structural failure of materials

3s–3p laser gain and x‐ray line ratios for the carbon isoelectronic sequence

U. Feldman, J. F. Seely, G. A. Doschek, and A. K. Bhatia

J. Appl. Phys. 59, 3953 (1986); http://dx.doi.org/10.1063/1.336695 (5 pages) | Cited 8 times

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The populations of the 46 levels belonging to the configurations 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, and 2s22p3d have been calculated for ions in the C I isoelectronic sequence with atomic numbers Z=18, 22, 26, 30, 34, and 36 and for electron densities from 1015 to 1022 cm−3. The populations of the 2s22p3p levels are relatively large owing to the large electron collisional monopole excitation rates from the ground configuration and to the small radiative decay rates to the ground configuration. This results in population inversions for transitions of the type 3s–3p. The gain coefficients for these transitions are determined and are compared to previous calculations. At high electron densities where collisional mixing of the excited levels becomes important, the intensities of the x‐ray transitions from the 2s22p3p levels to the 2s2p3 levels decrease relative to the x‐ray transitions from the 2s22p3s and 2s22p3d levels. The density dependence of these x‐ray line ratios is also presented. These line ratios represent a promising diagnostic for electron density.
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32.30.Rj X-ray spectra
32.70.Fw Absolute and relative intensities
34.80.Dp Atomic excitation and ionization
52.70.La X-ray and γ-ray measurements

Longitudinal‐mode stabilization in semiconductor lasers with wavelength‐selective feedback

Govind P. Agrawal

J. Appl. Phys. 59, 3958 (1986); http://dx.doi.org/10.1063/1.336696 (4 pages) | Cited 6 times

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In optical communication systems operating near the zero‐dispersion wavelength of the fiber, the wavelength of semiconductor lasers should remain stabilized to minimize the effects of fiber dispersion. We analyze theoretically the requirements for mode stabilization when external dispersive feedback is used to select a longitudinal mode. The feedback bandwidth should be less than the external‐cavity mode spacing to avoid the excitation of side modes corresponding to the longitudinal modes of the external cavity. By a suitable choice of laser parameters, a multimode laser can remain stabilized in the vicinity of the feedback‐selected wavelength even when the free‐running wavelength has drifted by more than 10 nm.
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42.55.Mv Dye lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Rydberg–bremsstrahlung maser

A. Jay Palmer

J. Appl. Phys. 59, 3962 (1986); http://dx.doi.org/10.1063/1.336697 (3 pages)

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Stimulated emission of bremsstrahlung radiation by electrons in high Rydberg states is analyzed theoretically. This approach to bremsstrahlung masers is shown to overcome some of the previous difficulties in realizing a practical value for the bremsstrahlung gain in the millimeter‐wave regime by allowing volumetric production of monoenergetic electrons within a time period which is short compared to the thermalization time of the electron energy distribution, and by relaxing the criteria on the energy dependence of the collision cross section for achieving a positive bremsstrahlung gain coefficient.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
34.50.-s Scattering of atoms and molecules
32.30.Bv Radio-frequency, microwave, and infrared spectra

A highly efficient, compact chemical oxygen–iodine laser

Hideaki Yoshimoto, Hideo Yamakoshi, Yukio Shibukawa, and Taro Uchiyama

J. Appl. Phys. 59, 3965 (1986); http://dx.doi.org/10.1063/1.336698 (3 pages) | Cited 12 times

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The dependence of the laser output power on the flow velocity at a cavity for a compact chemical oxygen–iodine laser is reported. The flow velocity is changed by using two vacuum pumps (3000 and 15 000 l/min). It becomes experimentally clear that the laser output power is proportional to the flow velocity and the extractable O2(1Δ) concentration. Output power in excess of 100 W has been extracted efficiently. The maximum overall reaction efficiency of 16.8% with the chlorine flow rate of 413 mmol/min is obtained.
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42.55.Ks Chemical lasers
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.60.Ps Chemiluminescence

Stimulated two‐photon processes: Effects of the radiation frequencies ratio on the gain spectrum induced by a focused pump

Michel Gingras and Marguerite‐Marie Denariez‐Roberge

J. Appl. Phys. 59, 3968 (1986); http://dx.doi.org/10.1063/1.336699 (3 pages)

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It is shown that the calculated gain spectrum of the radiation generated by a two‐photon process, evaluated from a high‐order approximation solution of the wave equation, is larger than the one obtained from a zero‐order approximation. The difference between the two approximations becomes very important when the ratio of the frequency of the generated radiation to that of a focused pump is large and/or when the pump power is low.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Infrared thermal particle detection physics

S. Utterback and R. Melcher

J. Appl. Phys. 59, 3971 (1986); http://dx.doi.org/10.1063/1.336700 (4 pages) | Cited 2 times

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Thermal particle detection is a new approach to the detection of generic particulate contaminants on products. The method takes advantage of the low thermal conductivity of a particle/substrate interface by using rapid thermal heating to raise the particle temperature over the temperature of its surroundings. The perturbed particle is then detected by its subsequent thermal emissions with a highly sensitive IR detector. The physics of particle heating and detection both in vacuum and in air is described.
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44.30.+v Heat flow in porous media
44.10.+i Heat conduction
68.35.Md Surface thermodynamics, surface energies

Detection of surface grooves and subsurface inhomogeneities in metals by transmission correlation photoacoustics

Ryoichi Takaue, Hiroshi Tobimatsu, Morio Matsunaga, and Kunisuke Hosokawa

J. Appl. Phys. 59, 3975 (1986); http://dx.doi.org/10.1063/1.336701 (5 pages)

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Correlation photoacoustics detected from the unilluminated surface of a sample have been studied to detect well‐characterized surface grooves and subsurface inhomogeneities in nickel. The correlation image of a line scan across an opaque sample by transmission technique can present the information on the surface or subsurface characteristics of the sample. This method is especially advantageous to detect subsurface grooves or inhomogeneities which exist anywhere in an optically opaque solid because the photoacoustic signals depend on the thermal and geometrical features in the transmission process of thermal waves. The system developed makes it possible to measure the impulse response of unstable samples because of the short time taken to collect data.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
68.35.B- Structure of clean surfaces (and surface reconstruction)

Calculation of magnetic shielding and ohmic losses from finite thickness Faraday shields used in rf heating of plasmas

D. N. Smithe, R. J. Kashuba, and T. Kammash

J. Appl. Phys. 59, 3980 (1986); http://dx.doi.org/10.1063/1.336702 (10 pages) | Cited 4 times

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Metallic Faraday shields commonly in use in many ion cyclotron resonance heating experiments have been shown to have two adverse effects on the antenna‐plasma coupling properties: magnetic shielding of the antenna current and possibly significant ohmic losses. The purpose of this paper is to investigate these two effects for shields of finite thickness using a detailed analysis of the fringing fields induced by the Faraday shields. Naturally, the extension to finite thickness introduces the question of shield cross‐section shape. Considerable attention is given to this point through two case studies of a square‐edged and a rounded‐edge shield. It is shown that magnetic shielding properties of a given cross section can be characterized by a single parameter, dependent only on cross‐section shape and dimensions. Ohmic losses are seen to be 30%–40% less for a cross section with rounded edges than for the square‐edged cross section. Also of interest is a minimum in the ohmic loss versus thickness relation for the round cross section, indicating the existence of an optimum ohmic loss design with respect to shield thickness.
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52.50.Gj Plasma heating by particle beams
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides

Theoretical analysis of soft x‐ray generation in the plasma of a spherical pinch

P. Savic and E. Panarella

J. Appl. Phys. 59, 3990 (1986); http://dx.doi.org/10.1063/1.336703 (6 pages) | Cited 2 times

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The production of soft x rays in the plasma of a spherical pinch is estimated, using the simple concepts of Bernstein and Comisar. It is shown that a relatively minor modification of the spherical pinch dynamics is required to account for the effect of radiation loss on the behavior of the plasma. The various time constants governing the plasma are examined and it is shown that of these, the confinement or ‘‘bounce’’ time, the radiation decay time, and the electron‐ion equilibration time are the most important. A computer program has been developed which shows that, to retain most of the energy of the discharge in the electrons and thereby maximize the x‐ray exposure, it is important to choose the correct time relationship between the central spark and the peripheral inductive discharge of the pinch.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.55.Ez Theta pinch

Spectroscopic study of the wall corrosion in super high‐pressure sodium discharge lamps

W. Reints Bok

J. Appl. Phys. 59, 3996 (1986); http://dx.doi.org/10.1063/1.336704 (8 pages) | Cited 3 times

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In 30‐W sodium discharge lamps with Na pressures up to 1 atm a chemical reaction takes place between Na and the vessel, consisting of sintered polycrystalline Al2O3 (PCA), leading to the formation of β‐aluminates and Al. From emission measurements at the 396‐nm line the Al pressure in operating lamps is derived. The transmission of the PCA wall and the plasma temperature, which are necessary in the Al pressure derivation, are determined by additional measurements on the 436‐ and 818‐nm emission lines of Hg and Na, respectively. The Al pressure is axially dependent, with a maximum in the center being about 10−6 atm at a lamp power of 32 W. When the lamp power is increased by 25% the central Al pressure increases by a factor of 5. The central Al pressure depends exponentially upon lamp power. The linear shape of the axial pressure profiles near the ends of the lamp indicates that Al production takes place mainly in the center of the lamp. Using a diffusion model the production rate of Al atoms is estimated to be 4×1011 atoms/s at 32 W. The experimentally determined pressures are higher than pressures calculated by equilibrium thermodynamics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
82.60.Hc Chemical equilibria and equilibrium constants

Electron energy distribution functions in molecular nitrogen: The role of superelastic electronic collisions in discharge and postdischarge conditions

F. Paniccia, C. Gorse, J. Bretagne, and M. Capitelli

J. Appl. Phys. 59, 4004 (1986); http://dx.doi.org/10.1063/1.337020 (3 pages) | Cited 29 times

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Electron energy distribution functions (EDF) and related quantities in N2 discharge and postdischarge conditions have been calculated by solving the Boltzmann equation, taking into account both superelastic vibrational (SVC) and electronic (SEC) collisions. These last collisions involve N2(A3Σ+u) and N2(B3Πg) states. The results show a large influence of SEC on EDF at low reduced electric fields (E/N<5×10−16 V cm2), the effects being more evident in the absence of SVC and in the postdischarge regime (E/N=0).
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52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.20.Fs Electron collisions
52.80.Hc Glow; corona

Characteristics of the discharge current in the nanosecond‐pulse breakdown

Takeki Sakurai and Toshimitsu Watanabe

J. Appl. Phys. 59, 4007 (1986); http://dx.doi.org/10.1063/1.336705 (4 pages) | Cited 4 times

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The rise time and the peak of a pulsed discharge current are measured under various experimental conditions such as the change in capacitances of both storage and peaking condensers. It is shown that the peak of the discharge current can be determined by the law of the second voltage‐time area. The relation between the rise time and the peak is also made clear.
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52.80.Dy Low-field and Townsend discharges
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Stability of metallic CsCl‐structured alloys under ion irradiation

M. Nastasi, D. Lilienfeld, H. H. Johnson, and J. W. Mayer

J. Appl. Phys. 59, 4011 (1986); http://dx.doi.org/10.1063/1.336706 (6 pages) | Cited 7 times

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The ion irradiation stability of the CsCl phases CoAl, IrAl, SiRu, and AuZn has been investigated. Thin‐film (∼500‐Å‐thick) transmission electron microscopy samples were irradiated with Xe to a maximum dose of 4×1015 ions/cm2 at room temperature. Irradiation‐induced transformations in the compound samples were examined by transmission electron diffraction. The alloys CoAl, IrAl, and AuZn remained crystalline while SiRu became amorphous. Analysis of our findings and other previously reported experimental results indicate that CsCl compound stability under ion irradiation is strongly correlated with atomic mobilities.
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61.80.Jh Ion radiation effects
68.55.-a Thin film structure and morphology
64.60.My Metastable phases
68.60.Dv Thermal stability; thermal effects

Frequency and temperature dependence of elastic moduli of polymers

N. Lagakos, J. Jarzynski, J. H. Cole, and J. A. Bucaro

J. Appl. Phys. 59, 4017 (1986); http://dx.doi.org/10.1063/1.336707 (15 pages) | Cited 21 times

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The frequency and temperature dependence of the elastic moduli of a number of commercially available polymers has been studied in the temperature range of 0–35 °C and for frequencies 102–106 Hz. Away from transitions a significant new relationship has been obtained, i.e., the Young’s modulus of these polymers is proportional to log of frequency. Using this relationship, together with the low and high frequency data, transitions in some of the polymers were identified.
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62.20.D- Elasticity
61.41.+e Polymers, elastomers, and plastics
65.40.De Thermal expansion; thermomechanical effects

Doping reaction of PH3 and B2H6 with Si(100)

Ming L. Yu, D. J. Vitkavage, and B. S. Meyerson

J. Appl. Phys. 59, 4032 (1986); http://dx.doi.org/10.1063/1.336708 (6 pages) | Cited 71 times

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The reaction of phosphine PH3 and diborane B2H6 on Si(100) surfaces was studied by surface analytical techniques in relation to the in situ doping process in the chemical vapor deposition of silicon. Phosphine chemisorbs readily either nondissociatively at room temperature or dissociatively with the formation of silicon–hydrogen bonds at higher temperatures. Hydrogen can be desorbed at temperatures above 400 °C to generate a phosphorus layer. Phosphorus is not effective in shifting the Fermi level until the coverage reaches 2×1014/cm2. A maximum shift of 0.45 eV toward the conduction band was observed. In contrast, diborane has a very small sticking coefficient and the way to deposit boron is to decompose diborane directly on the silicon surface at temperatures above 600 °C. Boron at coverages less than 2×1014/cm2 is very effective in shifting the Fermi level toward the valence band and a maximum change of 0.4 eV was observed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Ion beam annealing during high current density implants of phosphorus into silicon

S. Cannavó, A. La Ferla, E. Rimini, G. Ferla, and L. Gandolfi

J. Appl. Phys. 59, 4038 (1986); http://dx.doi.org/10.1063/1.337038 (5 pages) | Cited 5 times

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The damage left by high current density∼10 μA/cm2 implants of 120‐keV P+ into 4‐in. (500‐μm‐thick) and 5‐in. (600‐μm‐thick) Si wafers of 〈100〉 orientation has been measured by 2.0‐MeV He backscattering in combination with the channeling effect technique. The fluences ranged between 1 and 7.5×1015/cm2. The amount of disorder is highest at 1×1015/cm2 and then decreases with fluence. The annealing of the amorphous layer takes place by the movement of two and one amorphous–single crystal interfaces for the 500‐ and 600‐μm‐thick wafers, respectively. The experimental data are compared with a beam annealing model based on the temperature‐rise profile, the amount of point defects generated by the ion in the collision cascade volume, and the assumption of a regrowth process governed by an activation energy of 0.25 eV.
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61.80.Jh Ion radiation effects
61.72.Bb Theories and models of crystal defects
61.72.uf Ge and Si
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Self‐consistent T‐matrix solution and computer‐simulated velocity averaging approaches for the effective elastic constants of monoclinic polycrystals

Mala Paul, T. R. Middya, and A. N. Basu

J. Appl. Phys. 59, 4043 (1986); http://dx.doi.org/10.1063/1.336709 (5 pages) | Cited 1 time

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The self‐consistent T‐matrix solution envisaged by the effective‐medium approach [R. Zeller and P. H. Dederichs, Phys. Status Solidi B 55, 831 (1973)] has, in general, led to a considerable clarification of our understanding of the mechanical properties of a variety of disorder systems including polycrystals. Specifically, the relevant formulations have been developed for cubic polycrystals by Zeller and Dederichs, and for hexagonal, tetragonal, trigonal, and orthorhombic polycrystals by T. R. Middya and A. N. Basu [J. Appl. Phys. 59, 2368 (1986)]. The present work on monoclinic polycrystals is a sequel to our previous work. We have developed the complete set of equations within the framework of the effective medium theory which delivers in a self‐consistent manner the effective elastic constants of a monoclinic polycrystal in terms of those of the single crystal data. For comparison we have also evaluated the same quantities for each polycrystal by the computer simulation employing the velocity averaging process developed by T. R. Middya, A. N. Basu, and S. Sengupta [J. Appl. Phys. 57, 1844 (1985)]. Finally the results obtained by the above approaches for eight different polycrystals are compared with each other and also with other existing theoretical calculations.
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62.20.D- Elasticity

Statistics of structure within solid fragments studied by 2D simulation

Z. Jaeger, R. Englman, and A. Sprecher

J. Appl. Phys. 59, 4048 (1986); http://dx.doi.org/10.1063/1.336710 (9 pages) | Cited 6 times

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A strongly fragmented two‐dimensional medium was generated by a large number (103–104) of randomly thrown linear cracks. Various properties of fragments (e.g., number, size, shape, perimeter length, number of sides, and internal structure) were analyzed by computational geometry using a plane sweep algorithm. Asymptotically, for high crack density, the simulated fragment sizes follow the Mott distribution formula (cumulative number decreases exponentially with linear fragment size). Fragment structure, due to dangling or fully internal cracks, is identified with internal damage. The magnitude of damage as function of crack density is obtained by computation and analysis and is shown to reach a constant value asymptotically. By our results, a blasting operation leading to crack growth increases the ratio of small fragments in relation to larger ones.
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62.20.M- Structural failure of materials
47.56.+r Flows through porous media
91.60.Ba Elasticity, fracture, and flow

Variations in the second‐ and third‐order elastic constants in polycrystalline aggregates

George C. Johnson

J. Appl. Phys. 59, 4057 (1986); http://dx.doi.org/10.1063/1.336711 (5 pages) | Cited 2 times

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Expressions for the expected variation in the effective second‐ and third‐order elastic constants of statistically isotropic polycrystalline aggregates with a finite number of crystallites are developed. The analysis is based on the Voigt approach for the effective response of an aggregate and is valid for cubic crystals of the highest symmetry (m3m,432,43m). In this approach, the effective stiffnesses are the averages of the stiffnesses in the constituent crystals. It is shown that the expected variance in the effective elastic stiffness is inversely proportional to the number of crystallites contributing to the average. Numerical evaluations for crystals of various materials show that the variations in the third‐order stiffnesses are substantially larger than the variations in the second‐order stiffnesses.
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62.20.D- Elasticity
62.30.+d Mechanical and elastic waves; vibrations
46.25.Cc Theoretical studies

Microstructural studies of the growth of aluminum films with water contamination

G. J. van der Kolk and M. J. Verkerk

J. Appl. Phys. 59, 4062 (1986); http://dx.doi.org/10.1063/1.336712 (6 pages) | Cited 8 times

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Al films were grown at three different water partial pressures. The structure of the films at various thicknesses was observed with transmission electron microscopy. It was found that all three cases grew initially by island formation. (i) At greater thicknesses the film grown at the lowest pressure has large grains and a uniform thickness. (ii) The medium contaminated film has relatively clean regions with large grains and heavily contaminated regions with small grains. Furthermore, the film is not uniform in thickness; the clean regions are much thicker than the contaminated ones. Contamination of Al nucleates at discontinuous regions. Starting at the boundary Al substrate vacuum the contamination extends up to the Al surface. The contaminant layer prevents coalescence and recrystallization of Al, explaining the small grain size in certain areas. (iii) The heavily contaminated film has small grains and a uniform thickness. It is observed that at relatively small thicknesses (50 nm) the Al surface is already contaminated, preventing the growth of large grains.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

InGaAsP superlattices grown by liquid‐phase epitaxy

J. L. Benchimol, S. Slempkes, D. C. N’Guyen, G. LeRoux, J. F. Bresse, and J. Primot

J. Appl. Phys. 59, 4068 (1986); http://dx.doi.org/10.1063/1.336713 (5 pages) | Cited 2 times

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The liquid‐phase epitaxy of InGaAsP periodic structures is reported. A conventional horizontal sliding boat or a computer‐controlled rotating crucible was used to grow two types of structures. Stacks of thin layers grown from the same melt showed high‐quality x‐ray diffraction profiles, which are shown to allow a precise determination of layer thickness; supersaturation was found to significantly influence layer thickness for short growth times. In superlattices such as InP/InGaAsP or InGaAsP/InGaAs, good composition and thickness reproductibility throughout the structure was verified by Auger sputtering. The presence of satellite peaks in x‐ray diffraction profiles clearly proved that periodicity was well achieved in these structures. Quantum effects were observed by photoluminescence in sufficiently small wells.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.40.Fy Semiconductors

Growth and properties of Si films on sapphire with predeposited amorphous Si layers

Makoto Ishida, Yukio Yasuda, Hidenori Ohyama, Hidetoshi Wakamatsu, Hiroshi Abe, and Tetsuro Nakamura

J. Appl. Phys. 59, 4073 (1986); http://dx.doi.org/10.1063/1.336714 (6 pages) | Cited 7 times

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Si (001) films of high quality were grown successfully on sapphire substrates with thin predeposited amorphous Si layers, less than 40 Å thick. In order to investigate the growth features and properties of the films, the dependence of the film quality on the growth temperature, growth rate, and predeposited layer thickness were studied by various physical analyses including reflection high‐energy electron diffraction (RHEED), replica electron microscopy, secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES) and electron spectroscopy for chemical analysis (ESCA), and electrical measurements of effective mobilities of metal‐oxide‐semiconductor field effect transistors (MOSFETs). The most remarkable feature of this method is that films with a smooth surface and a high crystalline quality grow even at a slow growth rate, less than 0.1 μm/min and a high growth temperature of about 1000 °C, which are concerned with surface reactions in the initial stage of chemical vapor deposition (CVD). The interface region between the film and the substrate has an abrupt concentration gradient of constituent atoms. The effective mobilities of MOSFETs fabricated on the films do not depend on the growth rate, unlike the case of the usual method, and were 1.5–1.25 times as large as those without predeposited layers. Experimental results indicate that the optimum thickness of the predeposited layer is about 20 Å and that the heat treatment of the layer (∼3 min, 1000 °C) before CVD is important. A model to understand this growth method is proposed.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.30.Tv Field effect devices

Measurement of deep states in undoped amorphous silicon by current transient spectroscopy

H. Kida, K. Hattori, H. Okamoto, and Y. Hamakawa

J. Appl. Phys. 59, 4079 (1986); http://dx.doi.org/10.1063/1.336715 (8 pages) | Cited 12 times

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Localized deep states in undoped a‐Si:H have been investigated by current transient spectroscopy (CTS). After a trap‐filling light pulse, current transients associated with thermal emission of trapped carriers are measured over a wide time range under the isothermal condition. Slow saturation of the CTS signal J×t, with increased filling‐pulse duration is well explained by taking account of spatially and energy dependent carrier capture and emission processes, yielding an estimate of attempt‐to‐escape frequency. The attempt‐to‐escape frequency has been found to be energy dependent and to range from 1012 to 1013 s−1. Detailed analysis of the CTS signal has revealed that deep‐states distribution displays a broad peak locating near the center of the gap and a less pronounced structure at 0.5–0.6 eV below the conduction band edge.
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78.40.Fy Semiconductors
71.20.-b Electron density of states and band structure of crystalline solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ng Disordered solids

A new connection rule of wave functions at a heterointerface and band discontinuity between GaAs and AlGaAs

A. Ishibashi, Y. Mori, K. Kaneko, and N. Watanabe

J. Appl. Phys. 59, 4087 (1986); http://dx.doi.org/10.1063/1.336716 (4 pages) | Cited 11 times

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A new connection rule of wave functions at a heterointerface was developed. This connection rule satisfies the conservation of probability current and contains a nonparabolic effective mass of carriers as a natural consequence of the theory. The subband energies in a GaAs/AlGaAs quantum well calculated using our new connection rule are in excellent conformity with a wide range of experimental results with band discontinuity of 85% and an effective mass for hole of 0.34m0.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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