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17 Mar 1986

Volume 48, Issue 11, pp. 683-741


All‐optical power limiting of CO2 laser pulses using cascaded optical bistable elements

A. C. Walker, A. K. Kar, Wei Ji, U. Keller, and S. D. Smith

Appl. Phys. Lett. 48, 683 (1986); http://dx.doi.org/10.1063/1.96742 (3 pages) | Cited 11 times

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We report the first all‐optical power limiter based on cascaded InSb étalons. The power limiting effect is due to a dispersive nonlinearity in InSb at room temperature as a result of generation of free carriers through two‐photon absorption of 10 μm radiation. The efficiency and dynamic range of this all‐optical circuit are discussed.
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42.79.-e Optical elements, devices, and systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Generation of soft x rays using a rare gas‐hydrogen plasma focus and its application to x‐ray lithography

Y. Kato and S. H. Be

Appl. Phys. Lett. 48, 686 (1986); http://dx.doi.org/10.1063/1.96743 (3 pages) | Cited 64 times

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A conventional plasma focus device was used to produce a hot, dense plasma which emits radiation strongly in the soft x‐ray region. We showed experimentally that a plasma produced from a mixture of hydrogen and a rare gas such as neon, argon, or krypton is an effective source of a characteristic x ray of the rare gas. Resist exposures and pattern printings were made to evaluate the feasibility of this device as a source for soft x‐ray lithography.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.85.-m X- and γ-ray instruments
81.65.-b Surface treatments
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Significant enhancement of XeCl(B, C) and XeF(B, C) formation rate constants in reactions of Xe(5p56p) atoms with halogen donors

J. K. Ku and D. W. Setser

Appl. Phys. Lett. 48, 689 (1986); http://dx.doi.org/10.1063/1.96744 (3 pages) | Cited 36 times

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The quenching rate constants for Xe(6p) atoms by several halogens and halogen‐containing molecules have been measured and they are substantially larger than for reactions of Xe(6s) metastable atoms. The effect is largest for molecules with small Xe(6s 3P2) quenching rate constants and the Xe(6p) rate constants for NF3 are 5–20 times larger. Moreover, the branching fractions for XeCl(B, C) and XeF(B, C) formation are also larger for Xe(6p) atoms than for Xe(6s 3P2) atoms; the branching fractions for HCl are enhanced by more than an order of magnitude. These findings may have important implications for the operation and modeling of rare gas halide lasers and other gas discharge devices.
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34.50.Lf Chemical reactions
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
78.60.Ps Chemiluminescence
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Fast imaging of tokamak plasmas with integrated photodiode arrays

J. Castracane and Y. Demers

Appl. Phys. Lett. 48, 692 (1986); http://dx.doi.org/10.1063/1.96745 (3 pages)

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Images with high temporal and spatial resolution of the resurrector tokamak plasma were obtained. The plasma cross section was focused onto a commercially available 128 pixel photodiode array (active area: 2.5×3.2 mm2). Specially designed data acquisition electronics allowed rapid readout for the observation of the spatial profile of visible emissions with 150 μs time resolution. The breakdown and subsequent evolution of the discharge was monitored to allow improvement of the plasma parameters.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

Enhancement of the plasma density and deposition rate in rf discharges

L. J. Overzet and J. T. Verdeyen

Appl. Phys. Lett. 48, 695 (1986); http://dx.doi.org/10.1063/1.96746 (3 pages) | Cited 44 times

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The peak and time averaged electron density in rf excited silane‐helium mixtures increased significantly above the cw value by square wave modulating the source. The deposition rate of amorphous hydrogenated silicon films is also enhanced and apparently follows the electron density. Attachment to the discharge products appears to be responsible.
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52.80.Pi High-frequency and RF discharges
52.80.Vp Discharge in vacuum
52.70.Gw Radio-frequency and microwave measurements
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

A method of poling LiNbO3 and LiTaO3 below Tc

P. W. Haycock and P. D. Townsend

Appl. Phys. Lett. 48, 698 (1986); http://dx.doi.org/10.1063/1.96747 (3 pages) | Cited 24 times

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A method of poling LiNbO3 and LiTaO3 significantly below their Curie temperatures is proposed and results are presented. The technique involves excitation of the crystal lattice by an energetic beam of electrons while applying an electron field along the c axis. The lowest temperatures and fields successfully used so far are 600 °C with 10 V cm−1 for LiNbO3 and 400 °C with 900 V cm−1 for LiTaO3. These do not necessarily define lower limits for the process.
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77.22.Ej Polarization and depolarization
81.40.Rs Electrical and magnetic properties related to treatment conditions
78.20.Jq Electro-optical effects
61.80.Fe Electron and positron radiation effects

Effects of substrate preparation conditions on GaAs oval defects grown by molecular beam epitaxy

K. Fujiwara, Y. Nishikawa, Y. Tokuda, and T. Nakayama

Appl. Phys. Lett. 48, 701 (1986); http://dx.doi.org/10.1063/1.96748 (3 pages) | Cited 7 times

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Effects of substrate preparation conditions, i.e., wet chemical and ultrahigh vacuum cleaning preparations, on GaAs oval defects grown by molecular beam epitaxy (MBE) were investigated. It is found that, with our MBE system, the presence of the smaller (<10 μm) ovally shaped defects without macroscopic core particulates can be ascribed to surface microscopic contaminations. Most of the other remaining larger (>10 μm) oval defects with core particulates observed on 1‐μm‐thick GaAs MBE layers are attributed to surface macroscopic contaminations. The total density is reduced to 300 cm−2 without significantly modifying the growth cell parameters.
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68.35.Dv Composition, segregation; defects and impurities
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.-b Surface treatments
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Dopant redistribution in silicon‐on‐sapphire films during thermal annealing

N. E. B. Cowern, K. J. Yallup, and D. J. Godfrey

Appl. Phys. Lett. 48, 704 (1986); http://dx.doi.org/10.1063/1.96695 (3 pages)

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Arsenic depth distributions in silicon‐on‐sapphire films, after annealing at 900 °C for a range of times, have been studied by Rutherford backscattering and spreading resistance techniques. A continuum pipe diffusion model is developed which accounts satisfactorily for the rapid diffusion and segregation effects observed. In addition, the same model predicts two‐dimensional dopant profiles with several novel features relevant to microelectronic device processing.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
66.30.J- Diffusion of impurities
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Amorphous transition phase of NiSi2

D. M. Vanderwalker

Appl. Phys. Lett. 48, 707 (1986); http://dx.doi.org/10.1063/1.96696 (2 pages) | Cited 22 times

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A glass transition phase forms at the Ni‐Si interface as a precursor to NiSi2. The crystalline to amorphous transformation occurs when a sufficient concentration of Ni atoms is present to raise the elastic energy of crystalline Si and lower the energy barrier to the reaction. NiSi2 crystals nucleate in the glass at the interface. The barrier height can depend on properties of the amorphous layer.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
73.40.Ns Metal-nonmetal contacts
68.35.Rh Phase transitions and critical phenomena
64.60.Q- Nucleation

Hydrogen passivation of the oxygen‐related thermal‐donor defect in silicon

N. M. Johnson and S. K. Hahn

Appl. Phys. Lett. 48, 709 (1986); http://dx.doi.org/10.1063/1.96697 (3 pages) | Cited 36 times

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It is demonstrated with both spreading resistance measurements and deep level transient spectroscopy that hydrogenation neutralizes the oxygen‐related thermal‐donor defect in n‐type silicon. Hydrogen neutralization of shallow‐donor dopants (e.g., phosphorus) is also illustrated. A model which accounts for shallow‐donor passivation is applied to explain the interaction between hydrogen and thermal donors.
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78.40.Fy Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
66.30.J- Diffusion of impurities
81.65.-b Surface treatments

First observation of the quantum Hall effect in a Ga0.47In0.53As‐InP heterostructure with three electric subbands

M. Razeghi, J. P. Duchemin, J. C. Portal, L. Dmowski, G. Remeni, R. J. Nicholas, and A. Briggs

Appl. Phys. Lett. 48, 712 (1986); http://dx.doi.org/10.1063/1.96698 (3 pages) | Cited 28 times

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Shubnikov–de Haas and quantum Hall effects have been studied in GaInAs‐InP heterojunctions grown by modified low pressure metalorganic chemical vapor deposition. In contrast to the results reported up till now on GaInAs‐InP heterojunctions with nearly the same channel electron density, not one but three electric subbands, E0, E1, and E2, are occupied in zero magnetic field. Two electric subbands E0 and E1 contribute to the quantum Hall effect. Magnetic depopulation of the higher (E1 and E2) subbands is observed in both perpendicular and tilted magnetic field orientations. This enables a demonstration of the importance of intersubband scattering in resistivity and cyclotron resonance.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Homogeneity qualification of GaAs substrates for large scale integration applications

J. Maluenda, G. M. Martin, H. Schink, and G. Packeiser

Appl. Phys. Lett. 48, 715 (1986); http://dx.doi.org/10.1063/1.96699 (3 pages) | Cited 8 times

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A novel procedure is used to qualify the homogeneity of GaAs substrates for large scale integration (LSI) circuit applications. This procedure is particularly well adapted for assessing the electrical variations of densely packed field‐effect transistors (FET’s) used in GaAs LSI circuits. Threshold voltage nonuniformity due to crystal inhomogeneity and surface effects is measured for both conventional and In‐alloyed, dislocation‐free, slightly Cr‐doped, semi‐insulating liquid encapsulated Czochralski substrates. The average value of the threshold voltage standard deviation of about 300 dense rows over a 2‐in.‐diam wafer (30 FET’s over 300 μm for each row) is 20 mV using dislocation‐free substrates which is much smaller than in conventional substrates (50–100 mV). These data show the importance of this qualification test with the highest ever reported resolution of 10 μm suitable for the evaluation of fabrication yield of LSI circuits.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
85.30.Tv Field effect devices
78.40.Fy Semiconductors
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Studies of atomic and molecular fluorine reactions on silicon surfaces

C. D. Stinespring and A. Freedman

Appl. Phys. Lett. 48, 718 (1986); http://dx.doi.org/10.1063/1.96700 (3 pages) | Cited 39 times

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X‐ray photoelectron spectroscopy (XPS) and an ultrahigh vacuum compatible microwave discharge effusive beam source have been used to study the reactions of atomic and molecular fluorine on Si(111) surfaces. Fluorine uptake and changes in binding energy and peak shape for the Si 2p and F 1s XPS peaks have been measured as functions of fluorine exposure. The results indicate that molecular fluorine is dissociatively chemisorbed to form an SiF2‐like surface species. This reaction saturates at approximately one monolayer surface coverage. In contrast, atomic fluorine uptake extends well beyond the monolayer regime to include several Si layers. Additionally, as the uptake increases, the reaction product becomes SiF4‐like. These findings are compared with previously reported results for XeF2 adsorption.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Recombination mechanisms in Si and Si thin films determined by picosecond reflectivity measurements near Brewster’s angle

P. M. Fauchet and W. L. Nighan

Appl. Phys. Lett. 48, 721 (1986); http://dx.doi.org/10.1063/1.96701 (3 pages) | Cited 15 times

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A sensitive pump and probe method for measuring the transient carrier density in semiconductors is proposed and demonstrated in silicon. It relies on the magnified reflectivity changes when the picosecond probe laser is incident close to Brewster’s angle. We have measured the Auger recombination coefficient γ=2×10−31 cm6 s−1 and, in microcrystalline silicon films on insulator, the effective lifetime due to grain boundaries τ≂100 ps. Additionally, at much higher pump energies, upon melting, the reflectivity jumps by nearly one order of magnitude.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
75.20.Ck Nonmetals
79.20.Ds Laser-beam impact phenomena

Spatial location of electron trapping defects on silicon by scanning tunneling microscopy

M. E. Welland and R. H. Koch

Appl. Phys. Lett. 48, 724 (1986); http://dx.doi.org/10.1063/1.96702 (3 pages) | Cited 52 times

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Individual electron trapping sites in thermally oxidized silicon substrates have been observed using a scanning tunneling microscope (STM). The excellent spatial resolution of the STM allows single defects to be identified and located on the surface. The tunneling current near single trapping sites was observed to switch between two well defined values as the site occupation changed. The magnitude of the change in the current and spatial extent of the current fluctuations, typically 3 nm, is consistent with the calculated change in tunneling current from a single electron being trapped in the oxide.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
73.20.-r Electron states at surfaces and interfaces

Excitonic photoluminescence linewidths in AlGaAs grown by molecular beam epitaxy

D. C. Reynolds, K. K. Bajaj, C. W. Litton, P. W. Yu, J. Klem, C. K. Peng, H. Morkoç, and Jasprit Singh

Appl. Phys. Lett. 48, 727 (1986); http://dx.doi.org/10.1063/1.96703 (3 pages) | Cited 18 times

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The linewidths of excitonic transitions were measured in AlxGa1−xAs, grown by molecular beam epitaxy as a function of alloy composition x for values of x≲0.43 using high resolution photoluminescence spectroscopy at liquid helium temperature. The values of the linewidths thus measured are compared with the results of several theoretical calculations in which the dominant broadening mechanism is assumed to be the statistical potential fluctuations caused by the components of the alloy. An increase in the linewidth as a function of x is observed which is in essential agreement with the prediction of the various theoretical calculations. The linewidths of the excitonic transitions in AlxGa1−xAs observed in the present work are the narrowest ever reported in the literature, for example σ=2.1 meV for x=0.36, thus indicating very high quality material.
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71.35.-y Excitons and related phenomena
78.40.Fy Semiconductors

Magnetic anisotropy in dc diode getter sputtered GdCo films—How important is the argon content in the films?

D. D. Bacon, M. Hong, E. M. Gyorgy, P. K. Gallagher, S. Nakahara, and L. C. Feldman

Appl. Phys. Lett. 48, 730 (1986); http://dx.doi.org/10.1063/1.97020 (3 pages) | Cited 2 times

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Amorphous magnetic GdCo films were prepared by a dc diode getter sputtering technique with no bias field applied to the substrate during the film growth. Films (type I) obtained using 1.0 kV and 60 mTorr Ar during the sputtering show perpendicular anisotropy with Keffu =1.5×105 erg/cm3. Films (type II) deposited at 2.0 kV and 28 mTorr Ar exhibit magnetic isotropy with Kinu≊0. However, the actual argon content in the type II films is three times of that in the type I films. Nevertheless, the argon impurity in both the type I and type II films is ≤1.0 at. %, which is far less than those obtained in the biased rf diode sputtered GdCo films. Also, the distribution of argon is uniform in the film as observed from the Rutherford backscattering spectrometry.
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75.30.Gw Magnetic anisotropy
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.50.Kj Amorphous and quasicrystalline magnetic materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Microstructure, domain walls, and magnetization reversal in hot‐pressed Nd‐Fe‐B magnets

Raja K. Mishra and Robert W. Lee

Appl. Phys. Lett. 48, 733 (1986); http://dx.doi.org/10.1063/1.96704 (3 pages) | Cited 44 times

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Transmission electron microscopy study of hot‐pressed and hot‐deformed Nd0.14(Fe0.94B0.06)0.86 magnets shows that the magnetic alignment is achieved by the formation of a microstructure consisting of platelets of Nd2Fe14B grains with the c axis normal to the platelet surface and parallel to the press direction. Magnetic domain walls, lying parallel to the c axis, run through many grains and are pinned at the intergranular phases that are produced during processing. Magnetization reversal occurs by domain wall motion.
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75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys
07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
61.66.Dk Alloys

Laser etching of 0.4 μm structures in CdTe by dynamic light guiding

C. Arnone, M. Rothschild, and D. J. Ehrlich

Appl. Phys. Lett. 48, 736 (1986); http://dx.doi.org/10.1063/1.96705 (3 pages) | Cited 13 times

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CdTe single crystals have been etched by photosublimation with a cw visible laser. Structures with lateral widths comparable to the laser wavelength (∼0.5 μm) and depths exceeding 10 μm were obtained using a moderately focused beam. The formation of these structures is highly nonlinear with respect to laser power and is analyzed in terms of the dynamic interaction of the beam with the induced microstructure. Once initiated, deep structures are formed via laser‐induced tellurium enrichment of CdTe surface layers and the consequent enhanced waveguiding properties of these surfaces. The mechanism of etching has been studied by mass spectrometer and light scattering experiments.
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81.65.-b Surface treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
64.70.Hz Solid-vapor transitions
42.79.Gn Optical waveguides and couplers

Generation of highly monochromatic positrons using cold moderators

B. L. Brown, W. S. Crane, and A. P. Mills

Appl. Phys. Lett. 48, 739 (1986); http://dx.doi.org/10.1063/1.96706 (3 pages) | Cited 16 times

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Slow positron beams generally employ a radioactive  β+ emitter with a crystal moderator in which the positrons thermalize. A small fraction of the thermalized positrons are desorbed at low (1–3 eV) energy, characteristic of the positron work function in the crystal. The energy width of the emitted positrons from W(110) and Ni(111) moderators can be narrowed significantly by cooling to liquid N2 temperatures. A practical configuration for a cooled moderator positron gun is presented which produces a narrow energy positron beam with good efficiency.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
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