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31 Mar 1986

Volume 48, Issue 13, pp. 817-880


Design of a Bragg cavity for a millimeter wave free‐electron laser

M. C. Wang, V. L. Granatstein, and R. A. Kehs

Appl. Phys. Lett. 48, 817 (1986); http://dx.doi.org/10.1063/1.97019 (3 pages) | Cited 18 times

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This letter concerns a design of a Bragg cavity for TM modes that can be used with a free‐electron laser (FEL) or other electron beam generator. If the corrugated wall in the FEL section meets the Bragg condition, the distributed feedback mechanism can function like mirrors in the usual laser cavity; however, the Bragg cavity eliminates the dead space between the interaction region and the reflectors so that it is a preferred design where the pulse duration of the electron beam is limited. The calculations indicate that high reflection coefficients that correspond to high cavity Q factor can be obtained if we carefully choose the parameters of the corrugated wall, such as period, amplitude, and length. Finally, we discuss factors to be considered in the design of a Bragg cavity for a FEL based on an intense relativistic electron beam and an electromagnetic pump wave.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
41.60.Cr Free-electron lasers
41.75.Ht Relativistic electron and positron beams
41.60.-m Radiation by moving charges

Optimum overlap of electric and optical fields in semiconductor waveguide devices

M. J. Adams, S. Ritchie, and M. J. Robertson

Appl. Phys. Lett. 48, 820 (1986); http://dx.doi.org/10.1063/1.96678 (3 pages) | Cited 4 times

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The effect of an applied field on the propagation constant of a mode in a semiconductor slab waveguide is examined theoretically. A figure of merit defined as the change of propagation constant with voltage is related to the relative widths of the electrical and optical fields. It is shown that the figure of merit is maximized when the region over which the electric field is applied is minimized, rather than when the two fields have similar profiles. The constraint of electrical breakdown is also discussed with respect to the maximum change in propagation constant.
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42.79.Gn Optical waveguides and couplers
78.20.Jq Electro-optical effects
42.82.-m Integrated optics

Simultaneous optical pulse compression and wing reduction

N. J. Halas and D. Grischkowsky

Appl. Phys. Lett. 48, 823 (1986); http://dx.doi.org/10.1063/1.96679 (3 pages) | Cited 12 times

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We report the compression of picosecond optical pulses with a simultaneous reduction of the pulse wings by using a combination of both the self‐phase modulation and nonlinear birefringence effects in a modified optical‐fiber pulse compressor.
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42.81.Dp Propagation, scattering, and losses; solitons
42.81.Wg Other fiber-optical devices
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers

Stability of nonlinear stationary waves guided by a thin film bounded by nonlinear media

J. V. Moloney, J. Ariyasu, C. T. Seaton, and G. I. Stegeman

Appl. Phys. Lett. 48, 826 (1986); http://dx.doi.org/10.1063/1.96680 (3 pages) | Cited 30 times

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The stability of stationary, TE0‐type, nonlinear, thin‐film guided waves was investigated numerically for both symmetric and asymmetric planar waveguides with nonlinear cladding and substrate layers. It is found that large regions of the dispersion curves are unstable at high powers.
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42.79.Gn Optical waveguides and couplers
78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Effect of pulse sharpening on imploding neon Z‐pinch plasmas

S. J. Stephanakis, J. P. Apruzese, P. G. Burkhalter, J. Davis, R. A. Meger, S. W. McDonald, G. Mehlman, P. F. Ottinger, and F. C. Young

Appl. Phys. Lett. 48, 829 (1986); http://dx.doi.org/10.1063/1.96681 (3 pages) | Cited 26 times

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The radial implosion of hollow, cylindrical neon gas columns, driven by currents of up to 1.45 MA, produces a linear Z pinch with over 70% of the radiation in neon K lines. A plasma erosion opening switch (PEOS) is used to eliminate prepulse and to reduce the current rise time from ∼60 to ∼20 ns. Incorporation of the PEOS improves the uniformity of the Z pinch and increases the radiation yield.
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52.55.Ez Theta pinch
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Lp Plasma production and heating by shock waves and compression
52.59.Px Hard X-ray sources

Imaging in real time with the tunneling microscope

A. Bryant, D. P. E. Smith, and C. F. Quate

Appl. Phys. Lett. 48, 832 (1986); http://dx.doi.org/10.1063/1.96682 (3 pages) | Cited 112 times

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We report the achievement of real‐time video rate images of the atomic surface of graphite using the scanning tunneling microscope (STM). In this high‐speed mode of operation the topographic information is extracted directly from variations in the tunneling current. We find that this high‐speed technique offers the following advantages: the microscope becomes insensitive to most low frequency vibrations; piezoelectric scanner hysteresis appears to be reduced; and the effect of 1/f noise, which is conjectured to arise from diffusion of molecular species, is reduced by shifting the data to higher frequencies. The real‐time technique offers the opportunity to observe dynamic atomic processes which occur on time scales previously incaccessible to the STM.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
73.40.Gk Tunneling
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.-r Electron states at surfaces and interfaces

Amorphous carbon films as resist masks with high reactive ion etching resistance for nanometer lithography

Masami Kakuchi, Makoto Hikita, and Toshiaki Tamamura

Appl. Phys. Lett. 48, 835 (1986); http://dx.doi.org/10.1063/1.96683 (3 pages) | Cited 24 times

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We propose the application of carbon films as resist masks for practical nanometer lithography involving reactive ion etching (RIE). Amorphous carbon films prepared by room‐temperature plasma chemical vapor deposition show a very high resistance against RIE, the etching rates being less than 1/2 of that of a novolak‐based conventional photoresist. The carbon films can be finely patterned by O2 RIE in a bilayer resist process using a high‐resolution silicone‐based negative resist. Nanometer patterns as small as 40 nm are fabricated on a thick solid substrate, and can be transferred into the substrate layer directly by RIE.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Recrystallization of amorphous silicon film by tungsten halogen lamp annealing

Hitoshi Arai, Kenji Nakazawa, and Shigeto Kohda

Appl. Phys. Lett. 48, 838 (1986); http://dx.doi.org/10.1063/1.96684 (2 pages) | Cited 4 times

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The transformation of amorphous silicon films to polycrystalline materials induced by tungsten halogen lamp annealing has been studied by x‐ray diffraction and transmission electron microscopy. Tungsten halogen lamp annealing shortens annealing time, requiring only 1/10– 1/100 the time needed to grow the same size grains as by furnace annealing. Isochronal annealing by a tungsten halogen lamp reveals that the activation energy for grain growth is 0.64 eV, while that by furnace annealing is 0.23 eV. The cause of this difference is not clear; however the nucleation and following recrystallization process at low temperatures are found to depend on the heating rate and annealing time.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
64.70.K- Solid-solid transitions

Photocurrent spectroscopy in GaAs/AlGaAs multiple quantum wells under a high electric field perpendicular to the heterointerface

K. Yamanaka, T. Fukunaga, N. Tsukada, K. L. I. Kobayashi, and M. Ishii

Appl. Phys. Lett. 48, 840 (1986); http://dx.doi.org/10.1063/1.96685 (3 pages) | Cited 55 times

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Photocurrent (PC) spectroscopy under high electric fields perpendicular to the heterointerface has been utilized to characterize subband structures in GaAs/AlGaAs multiple quantum wells (MQW’s). The PC spectra from MQW’s under high electric fields show clear exciton peaks corresponding to forbidden transitions between electron and hole subbands. From PC spectra, we have precisely determined the splitting energies of the two lowest electron and four highest hole subbands in 55‐, 82‐, and 105‐Å‐thick wells. The experimental results indicate that the conduction‐band offset is 60±3% of the band‐gap discontinuity. Our data are also in excellent agreement with finite square well calculations using a heavy‐hole effective mass of 0.34 and a light‐hole effective mass of 0.12.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

In situ investigation of the nucleation of microcrystalline Si

R. W. Collins

Appl. Phys. Lett. 48, 843 (1986); http://dx.doi.org/10.1063/1.96686 (3 pages) | Cited 14 times

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In situ ellipsometry experiments have been used to probe the structural changes that occur in the initial stages of the growth of microcrystalline silicon ( μc‐Si) on single‐crystal Si substrates. The initial nucleation of μc‐Si appears to occur at well‐dispersed sites and ∼100 Å of material with significantly different optical properties than the bulk is buried at the film/substrate interface. The different optical structure of this interface layer is attributed to voids which are trapped when crystalline nuclei merge. These results are contrasted with recent data for hydrogenated amorphous silicon which show that nuclei converge after about 50 Å, leaving material with bulklike optical properties at the substrate interface.
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68.55.-a Thin film structure and morphology
75.20.Ck Nonmetals
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation

Physical processes in degradation of amorphous Si:H

David Redfield

Appl. Phys. Lett. 48, 846 (1986); http://dx.doi.org/10.1063/1.96687 (3 pages) | Cited 18 times

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A critical analysis is given of possible mechanisms of light‐induced degradation in amorphous Si:H (a‐Si:H) and of the constraints imposed on degradation models by recent experimental observations. Using an analogy with processes in recombination‐enhanced degradation of GaAs, it is shown that current intrinsic models for a‐Si:H are deficient in two significant respects. It is also found that these intrinsic models cannot explain several important observations. An alternative extrinsic model is shown to be free of these deficiencies.
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71.23.-k Electronic structure of disordered solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
72.40.+w Photoconduction and photovoltaic effects

Selectively buried epitaxial growth of GaAs by metalorganic chemical vapor deposition

Kotaro Okamoto and Ko‐ichi Yamaguchi

Appl. Phys. Lett. 48, 849 (1986); http://dx.doi.org/10.1063/1.96688 (3 pages) | Cited 4 times

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Selectively buried epitaxial growth of GaAs was attempted by metalorganic chemical vapor deposition using SiO2 films and W/SiO2 films as mask materials. Lateral supply of reactant species from mask areas to grooves occurred, which brought about the dependences of growth rate upon the width and the depth of grooves and produced swells near the groove edges. By use of W/SiO2 masks patterned narrower than 40 μm, grooves were selectively buried by epitaxial layers without accompanying polycrystal deposition on the masks.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.-b Surface treatments

Hg content of anodic oxide films on Hg1−xCdxTe after heat treatment as measured by 40 MeV‐O5+ ion backscattering

K. Takita, T. Ippōshi, K. Murakami, K. Masuda, H. Kudo, and S. Seki

Appl. Phys. Lett. 48, 852 (1986); http://dx.doi.org/10.1063/1.96689 (3 pages) | Cited 4 times

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The Hg concentration of anodic oxide films on Hg1−xCdxTe and its change after heat treatment were investigated by using 40 MeV‐O5+ backscattering. Heat treatment in a vacuum for 60 min was performed at various temperatures up to 350 and 400 °C, respectively, for the samples with x=0.19 and x=0.32. A significant Hg content in the as‐grown anodic oxide was found in accordance with the recent result of C. M. Stahle, D. J. Thomson, C. R. Helms, C. H. Becker, and A. Simmons [Appl. Phys. Lett. 47, 521 (1985)]. The Hg in the film gradually decreased with increasing heat treatment temperature up to about 290 °C and rapidly disappeared above 290 °C for both x=0.19 and x=0.32.
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68.55.Nq Composition and phase identification
81.65.-b Surface treatments
81.40.Gh Other heat and thermomechanical treatments
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Thermal detection of electron spin resonance in the persistent photoconductive state of semi‐insulating GaAs crystals grown from pyrolytic BN crucibles

K. W. Blazey and J. Schneider

Appl. Phys. Lett. 48, 855 (1986); http://dx.doi.org/10.1063/1.96690 (3 pages) | Cited 2 times

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Thermally detected electron spin resonance (TDESR) has been applied to paramagnetic defects characteristic of semi‐insulating (SI) GaAs crystals grown from pyrolytic boron nitride (pBN) crucibles. A strong isotropic TDESR signal near g=2.2 and two anisotropic lines at higher fields were observed at T=4.2 K and 13 GHz after in situ optical excitation. Spin‐dependent scattering of electrons, in their persistent photoconducting state, by paramagnetic defects is discussed as a possible cause of these resonances. Unsuccessful searches for this TDESR signal in semi‐insulating GaAs crystals grown under non‐pBN ambient conditions point to paramagnetic defects owing to the inclusion of some crucible material, e.g., nitrogen, as the source of the TDESR spectrum in pBN‐GaAs.
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76.30.Mi Color centers and other defects
72.40.+w Photoconduction and photovoltaic effects
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.72.J- Point defects and defect clusters

Comparison of buried oxide in silicon by oxygen implantation made by wafer and beam scanning

A. Mogro‐Campero, R. P. Love, N. Lewis, E. L. Hall, and M. D. McConnell

Appl. Phys. Lett. 48, 858 (1986); http://dx.doi.org/10.1063/1.96691 (3 pages) | Cited 5 times

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Buried oxide in silicon was formed by high dose oxygen implantation using either slow mechanical wafer scanning or the usual rapid beam scanning. Transmission electron microscopy and Auger depth profiling were used to characterize the samples after high‐temperature annealing: 1150 °C for 2 h, followed by 1210 °C for 6 h. Oxygen‐denuded zones of single crystal silicon are formed for both types of samples in the upper region of the top silicon layer (for the wafer‐scanned samples, an oxygen‐denuded zone had not formed after the usual 1150 °C anneal for 2 h). The dislocation density in the top silicon layer was much lower (<107 cm−2) for wafer‐scanned samples than for beam‐scanned samples (2×109 cm−2). The density of oxide precipitates in the top silicon layer and of silicon ‘‘islands’’ within the buried oxide was greater for wafer‐scanned samples. These microstructural differences may produce differences in electrical properties.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
81.40.Rs Electrical and magnetic properties related to treatment conditions

Stacking and layer disordering of AlxGa1−xAs‐GaAs quantum well heterostructures

K. Meehan, K. C. Hsieh, G. Costrini, R. W. Kaliski, N. Holonyak, and J. J. Coleman

Appl. Phys. Lett. 48, 861 (1986); http://dx.doi.org/10.1063/1.96692 (3 pages) | Cited 2 times

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Data are presented showing that an AlxGa1−x As‐GaAs quantum well heterostructure (QWH) or superlattice (SL) can be selectively disordered into higher gap bulk crystal by impurity (Si) diffusion and then have grown epitaxially on it (‘‘stacked’’ on it) another SL (or QWH), which can be subjected to further impurity‐induced layer disordering in a patterned form. The resulting three‐dimensional array can be operated as a photopumped laser.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
42.55.Px Semiconductor lasers; laser diodes

Subpicosecond excitonic electroabsorption in room‐temperature quantum wells

W. H. Knox, D. A. B. Miller, T. C. Damen, D. S. Chemla, C. V. Shank, and A. C. Gossard

Appl. Phys. Lett. 48, 864 (1986); http://dx.doi.org/10.1063/1.96693 (3 pages) | Cited 10 times

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We investigate the dynamics of excitonic optical absorption in room‐temperature GaAs quantum wells during the application of a rapidly changing electric field in the plane of the quantum well layers. We obtain electroabsorptive modulation with a response time constant of 330 fs, which is the fastest ever reported in a semiconductor.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.20.Jq Electro-optical effects
72.30.+q High-frequency effects; plasma effects
71.35.-y Excitons and related phenomena

Photochemical organometallic vapor phase epitaxy of mercury cadmium telluride

B. J. Morris

Appl. Phys. Lett. 48, 867 (1986); http://dx.doi.org/10.1063/1.96694 (3 pages) | Cited 22 times

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Mercury cadmium telluride has been successfully grown by the photolysis of dimethylmercury, dimethylcadmium, and dimethyltelluride, using an ArF excimer laser operating at 193 nm as the radiation source. Growths were accomplished on CdTe substrates at a temperature of 150 °C, with a growth rate of 4 μm per hour. Films are shiny, and x‐ray diffraction indicates epitaxial growth. Secondary ion mass spectroscopy and infrared transmission measurements indicate that the composition of the initial films is Hg0.2Cd0.8Te. Details of the growth apparatus and additional data is presented.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Nq Composition and phase identification

Growth of GaN single crystal films using electron cyclotron resonance plasma excited metalorganic vapor phase epitaxy

Sakae Zembutsu and Toru Sasaki

Appl. Phys. Lett. 48, 870 (1986); http://dx.doi.org/10.1063/1.96643 (3 pages) | Cited 18 times

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A low‐temperature growth technique for GaN single crystal films has been developed utilizing electron cyclotron resonance (ECR) plasma excitation. The GaN film has been grown in a low pressure metalorganic vapor phase epitaxy (MOVPE) system using the reaction of trimethylgallium with highly activated nitrogen extracted from the ECR plasma chamber. Growth conditions of GaN single crystal films have been clarified by examining reflection high‐energy electron diffraction patterns. The surface morphology of the GaN single crystal film is very smooth and electrical properties are comparable to those of a MOVPE technique at high growth temperatures.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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

High efficiency polycrystalline silicon solar cells using phosphorus pretreatment

S. Narayanan, S. R. Wenham, and M. A. Green

Appl. Phys. Lett. 48, 873 (1986); http://dx.doi.org/10.1063/1.96644 (3 pages) | Cited 19 times

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Recent improvements in crystalline silicon solar cell energy conversion efficiency to beyond 20% have been obtained by combining surface oxide passivation with high quality, low resistivity substrates. The objective of the present work was to evaluate the effectiveness of these techniques in improving efficiency on lower quality cast polycrystalline silicon. Due to the poorer crystallographic quality and higher levels of secondary impurities, an additional phosphorus pretreatment was found to reliably improve the performance of the polycrystalline cells above those fabricated without this pretreatment. Cell energy conversion efficiencies were notably higher than previously reported for the present material with values in the 15.3–16.0% range obtained for p‐type substrates of 0.1–1 Ω cm resistivity.
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
85.30.De Semiconductor-device characterization, design, and modeling
81.40.Rs Electrical and magnetic properties related to treatment conditions

Enhancement of sliding life of MoS2 films deposited by combining sputtering and high‐energy ion implantation

Jacques Chevallier, Svend Olesen, Gunnar Sørensen, and Balkishan Gupta

Appl. Phys. Lett. 48, 876 (1986); http://dx.doi.org/10.1063/1.96645 (2 pages) | Cited 14 times

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Solid lubricant films of MoS2 with improved adhesion to a stainless‐steel substrate have been deposited by a combination of rf sputtering and ion implantation with inert gas ions in the 100‐keV region. When the sputter film had obtained a thickness of 500 Å, it was subjected to the ionic bombardment prior to completion of the sputter deposition. Dependent on the ion dose an adhesion improvement and a sliding life enhancement of approximately a factor of 2 were obtained for the solid lubricant film.
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68.60.Bs Mechanical and acoustical properties
81.15.Cd Deposition by sputtering
81.40.Pq Friction, lubrication, and wear
61.80.Jh Ion radiation effects

Excimer lasers in cardiovascular surgery: Ablation products and photoacoustic spectrum of the arterial wall

D. L. Singleton, G. Paraskevopoulos, G. S. Jolly, R. S. Irwin, D. J. McKenney, W. S. Nip, E. M. Farrell, and L. A. J. Higginson

Appl. Phys. Lett. 48, 878 (1986); http://dx.doi.org/10.1063/1.96646 (3 pages) | Cited 22 times

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Photoacoustic spectra of normal artery wall and of atherosclerotic plaque are reported. Threshold fluences for ablative formation of gaseous products for each excimer laser line were calculated from the photoacoustic spectrum and the measured threshold for the KrF laser.
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87.50.S- Radiofrequency/microwave fields effects
87.50.W- Optical/infrared radiation effects
79.20.Ds Laser-beam impact phenomena
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