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5 Sep 1994

Volume 65, Issue 10, pp. 1205-1323

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Low resistivity cubic phase CdS films by chemical bath deposition technique

O. de Melo, L. Hernández, O. Zelaya‐Angel, R. Lozada‐Morales, M. Becerril, and E. Vasco

Appl. Phys. Lett. 65, 1278 (1994); http://dx.doi.org/10.1063/1.112094 (3 pages) | Cited 7 times

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In this letter we report on cubic CdS thin films with low resistivity by chemical bath deposition (CBD) technique and subsequent annealings in S2 and H2+In. Low temperature photoluminescence, x rays, and transmission spectra support the assumption that S2 annealings contribute to fill the vacancies in the as‐deposited films leading to an enlargement of the CdS cubic cell. This fact is revealed by an increase in interplanar distances, evanescence of the PL red broad band, and decrease in band‐gap energies. Cubic phase remains after H2+In annealing at higher temperatures. A resistivity as low as 11 Ω cm was obtained at an optimum annealing temperature of 350 °C.
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68.55.-a Thin film structure and morphology
84.60.Jt Photoelectric conversion

Γ to Xz electron transfer times in type‐II superlattices due to emission of confined phonons

Ana M. de Paula and Gerald Weber

Appl. Phys. Lett. 65, 1281 (1994); http://dx.doi.org/10.1063/1.112095 (3 pages) | Cited 13 times

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We calculate the Γ→Xz electron transfer times due to the emission of confined longitudinal optical phonons in type‐II GaAs‐AlAs and AlGaAs‐AlAs superlattices. A dielectric continuum model is employed to describe the electron‐confined‐phonon interaction and the electron envelope wave functions are obtained from a Kronig–Penney model. The calculated transfer times compare within order of magnitude, or better, with available experimental results and we obtain a good qualitative description of the transfer time dependence on the layer thicknesses.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Plasma nitrogen doping of ZnTe, Cd1−xZnxTe, and CdTe by molecular beam epitaxy

T. Baron, S. Tatarenko, K. Saminadayar, N. Magnea, and J. Fontenille

Appl. Phys. Lett. 65, 1284 (1994); http://dx.doi.org/10.1063/1.112096 (3 pages) | Cited 22 times

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The p‐type doping of ZnTe, CdTe, and Cd1−xZnxTe (CZT) using a nitrogen dc plasma source during growth by molecular beam epitaxy is demonstrated. For ZnTe, doping levels as high as 1020 cm−3 were achieved. In CZT alloys, a progressive decrease of the maximum doping level is observed for decreasing Zn content. Using pulse doping methods, a doping level of p≊3×1018 cm−3 is obtained for a 12% Zn CZT layer. For CdTe layers, the highest level achieved is p≊1017 cm−3. The progressive acceptor compensation phenomenon is discussed with emphasis on the role of the lattice distortion on the nitrogen incorporation mechanisms.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Rough versus dilute interfaces in semiconductor heterostructures: The role of growth conditions

W. Grieshaber, C. Bodin, J. Cibert, J. Gaj, Y. Merle d’Aubigné, A. Wasiela, and G. Feuillet

Appl. Phys. Lett. 65, 1287 (1994); http://dx.doi.org/10.1063/1.112097 (3 pages) | Cited 11 times

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CdTe‐CdMnTe interfaces grown by molecular beam epitaxy are studied using excitons confined in quantum wells. For increasing growth temperatures Zeeman splittings indicate an enhanced dilution of Mn ions at the interface while the optical linewidths evidence a decreasing roughness. These results directly illustrate the fact that the two methods are sensitive to different scales of interface broadening.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
78.66.Hf II-VI semiconductors

Violet luminescence from anodized microcrystalline silicon

Xinwei Zhao, Olaf Schoenfeld, Yoshinobu Aoyagi, and Takuo Sugano

Appl. Phys. Lett. 65, 1290 (1994); http://dx.doi.org/10.1063/1.112976 (3 pages) | Cited 19 times

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Microcrystalline silicon (μ‐Si) thin films were anodized in dilute HF solutions in the same manner as forming porous materials. It is demonstrated for the first time that the anodized μ‐Si thin films show strong violet luminescence (415 nm) at room temperature. Visible green and red emissions were also observed accompanying the violet luminescence. Structural investigations with scanning electron microscopy indicate that any formation of micrometer‐sized pores which is typical for porous silicon does not exist in the anodized μ‐Si thin films as reported here. This fact is useful for device applications of silicon‐based materials.
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78.55.Hx Other solid inorganic materials
78.66.Db Elemental semiconductors and insulators
68.55.-a Thin film structure and morphology

Interface formation in InAs/AlSb and InAs/AlAs/AlSb quantum wells grown by molecular‐beam epitaxy

J. Wagner, J. Schmitz, D. Behr, J. D. Ralston, and P. Koidl

Appl. Phys. Lett. 65, 1293 (1994); http://dx.doi.org/10.1063/1.112098 (3 pages) | Cited 8 times

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We have used resonant Raman scattering from both longitudinal‐optical phonons and interface modes to study the chemical bonding across the InAs/AlSb interface in InAs/AlSb quantum wells grown by molecular‐beam epitaxy. The effusion cell shutter sequence at the interfaces was selected for the deposition of either one monolayer of InSb or two to three monolayers of AlAs. In all cases an InSb‐like interface mode is observed, indicating the preferential formation of In—Sb interface bonds irrespective of the shutter sequence. The deposition of two or three monolayers of AlAs at the InAs/AlSb interface results in the formation of pseudoternary AlSb1−xAsx barriers rather than binary AlAs interfaces and AlSb barriers, indicating a strong exchange among the group‐V atoms. Normal (AlSb on InAs) and inverted (InAs on AlSb) InAs/AlSb interfaces have also been compared, revealing a much stronger InSb‐like interface mode for the growth of AlSb on InAs than for the case of InAs grown on AlSb.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.Fs III-V and II-VI semiconductors

Superconductivity and valence state of Tb in Lu1−xTbxBa2Cu3O7−δ (0≤x≤0.7)

K. I. Gnanasekar, P. Selvam, H. V. Keer, R. Pinto, S. C. Purandare, A. S. Tamhane, L. C. Gupta, and R. Vijayaraghavan

Appl. Phys. Lett. 65, 1296 (1994); http://dx.doi.org/10.1063/1.112099 (3 pages) | Cited 4 times

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Although both lutetium and terbium do not form superconducting REBa2Cu3O7−δ, we report here the formation of superconducting phase in thin films. Films are highly c‐axis oriented with high current densities (3.0×106 A cm−2 at 77 K) observed in Lu0.5Tb0.5Ba2Cu3O7−δ. X‐ray photoelectron spectroscopic analysis of Tb in the above film indicates that Tb is in a trivalent state. Further, as the redox potential of Tb (Tb4++e−→Tb3+:E0=3.1 V) is close to that of Pr (Pr4++e−→Pr3+:E0=3.2 V), we suggest that Pr also would be in a trivalent state and the mechanism by which the latter depresses Tc must be of trivalent origin.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Synthesis of YNi2B2C thin films by magnetron sputtering

Shunichi Arisawa, Takeshi Hatano, Kazuto Hirata, Takashi Mochiku, Hitoshi Kitaguchi, Hiroki Fujii, Hiroaki Kumakura, Kazuo Kadowaki, Keikichi Nakamura, and Kazumasa Togano

Appl. Phys. Lett. 65, 1299 (1994); http://dx.doi.org/10.1063/1.112100 (3 pages) | Cited 18 times

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Thin films of YNi2B2C superconductor by the magnetron sputtering technique have been synthesized. The YNi2B2C phase was found to crystallize very uniformly after annealing at 1050 °C in vacuum. The structure was investigated and the electric and magnetic properties were characterized. The films were c‐axis oriented and showed a Tc onset of ∼15 K by both magnetization and resistivity measurements. The results of the critical current measurement suggested the existence of anisotropies of pinning force and an upper critical field Bc2.
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74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
81.15.Cd Deposition by sputtering
74.25.-q Properties of superconductors

Dimensionality of flux pinning in (Bi,Pb)2Sr2Ca2Cu3O10+δ Ag tapes with columnar defects—Crossover from two‐dimensional to three‐dimensional behavior

P. Kummeth, C. Struller, H.‐W. Neumüller, and G. Saemann‐Ischenko

Appl. Phys. Lett. 65, 1302 (1994); http://dx.doi.org/10.1063/1.112101 (3 pages) | Cited 10 times

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We introduced columnar defects into (Bi,Pb)2Sr2Ca2Cu3O10+δ Ag tapes by irradiation with 2.65 GeV 197Au ions to investigate the dimensionality of pinning for this compound. Samples were irradiated up to fluences of 3.5×1011 ions/cm2 at a temperature of 100 K. The ion beam was directed both perpendicular and under a tilt angle of −60° to the tape surface. Our samples showed homogeneous columnar line defects throughout the whole thickness of the superconducting core. As a novel result we found evidence for marked deviations from two‐dimensional behavior at elevated temperatures both in magnetic and in transport measurements.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
61.80.Jh Ion radiation effects
74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes

Magnetic resonance of a small platinum particle using an integrated dc SQUID

L. R. Narasimhan, M. Takigawa, and M. B. Ketchen

Appl. Phys. Lett. 65, 1305 (1994); http://dx.doi.org/10.1063/1.112102 (3 pages) | Cited 12 times

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We report the detection of pulsed nuclear magnetic resonance in a single 50 μm particle of platinum metal at 4 K and in an applied field of 60 G. The flux from the precessing spins is detected directly by an integrated dc SQUID minisusceptometer. The device can operate in applied fields of up to 100 G without degradation of noise performance. The particle contains ≊1015 spin‐active nuclei while the signal intensity corresponds to flux from 2.5×1014 spins all located at the center of the pickup loop. This result represents a significant improvement in the sensitivity of NMR and may be useful in the characterization of materials with small spin populations.  
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76.60.-k Nuclear magnetic resonance and relaxation

Low temperature magnetic force microscope utilizing a piezoresistive cantilever

C. W. Yuan, E. Batalla, M. Zacher, A. L. de Lozanne, M. D. Kirk, and M. Tortonese

Appl. Phys. Lett. 65, 1308 (1994); http://dx.doi.org/10.1063/1.112103 (3 pages) | Cited 33 times

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We have developed a low temperature magnetic force microscope capable of operation down to 6 K in vacuum by using piezoresistive cantilevers. We use the non‐contact frequency modulation technique to detect the magnetic force gradient between an iron‐coated tip and the sample. We demonstrate the operation of this new instrument by obtaining images of magnetic domains in VHS tape at room temperature, 77 and 6 K. This microscope is ideally suited for the characterization of thin films of high temperature superconductors.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.72.-h Cuprate superconductors

Laser induced unzipping: A thermal route to polymer ablation

Graciela B. Blanchet and C. R. Fincher

Appl. Phys. Lett. 65, 1311 (1994); http://dx.doi.org/10.1063/1.112038 (3 pages) | Cited 14 times

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The data presented here show that polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) can be ablated by the evaporation of solid polymer targets with a pulsed ultraviolet laser. In situ measurements of the plume composition show that the products emitted under laser irradiation are primarily monomer and other species resulting from energetic collisions within the plasma. The similarities between the ablative and pyrolisis mass spectra suggest that ablation of PTFE and PMMA occur through a laser induced pyrolitic decomposition.
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81.15.Fg Pulsed laser ablation deposition
82.50.-m Photochemistry

Auger electron spectroscopy study of the interaction of NO2 with Si(100)

M. Bhat, A. Kamath, D. L. Kwong, Y. M. Sun, and J. M. White

Appl. Phys. Lett. 65, 1314 (1994); http://dx.doi.org/10.1063/1.112039 (3 pages) | Cited 1 time

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The nitridation of clean Si(100)‐2×1 with NO2 has been studied using Auger electron spectroscopy (AES). In this letter we demonstrate that the interaction of Si(100) with NO2 leads to the efficient incorporation of nitrogen (N) and oxygen (O) in single crystal Si as opposed to the case of N2O on Si(100). A comparative study of the incorporation efficiency of N and O by the reaction of NO2 and N2O with Si(100) over a wide temperature range has been performed. It is observed that only a few Langmuirs (L) of NO2 is required to saturate the Si surface while reaction with N2O is not as favorable. At temperatures ranging from room temperature to 1000 °C, varying proportions of N and O are incorporated into the Si by NO2. Repeated dosing and annealing cycles indicate that continued incorporation of N and O is possible even through a nitrogen‐rich Si layer.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Intracavity laser spectroscopy of RF plasmas of methane and benzene used in depositing diamondlike carbon films

M. J. Lipp and J. J. O’Brien

Appl. Phys. Lett. 65, 1317 (1994); http://dx.doi.org/10.1063/1.112040 (3 pages) | Cited 2 times

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Spatially resolved concentrations of excited atomic hydrogen (n=2), generated from 13.56 MHz RF hydrocarbon discharges, are determined during film formation using intracavity laser spectroscopy. Self‐bias voltages and pressures of methane (25 and 100 mTorr) and benzene (25 mTorr) are selected so that diamondlike carbon films are deposited. In all cases, the minimum concentration occurs at the power electrode. Benzene produces the least amount of excited atomic hydrogen overall. The results may have implications concerning the proposed impact induced fragmentation of hydrocarbon molecules during film growth.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties
FREE

Comment on ‘‘Time dependence of dopant diffusion in δ‐doped Si films and properties of Si point defects’’ [Appl. Phys. Lett. 64, 312 (1994)]

E. Antoncik

Appl. Phys. Lett. 65, 1320 (1994); http://dx.doi.org/10.1063/1.112041 (2 pages) | Cited 3 times

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Abstract Unavailable
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
FREE

Response to ‘‘Comment on ‘Time dependence of dopant diffusion in δ‐doped Si films and properties of Si point defects’ ’’ [Appl. Phys. Lett. 65, 1320 (1994)]

H.‐J. Gossmann, C. S. Rafferty, A. M. Vredenberg, H. S. Luftman, F. C. Unterwald, D. J. Eaglesham, D. C. Jacobson, T. Boone, and J. M. Poate

Appl. Phys. Lett. 65, 1322 (1994); http://dx.doi.org/10.1063/1.113006 (2 pages) | Cited 1 time

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Abstract Unavailable
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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