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24 Feb 1992

Volume 60, Issue 8, pp. 921-1029

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Visible luminescence from silicon wafers subjected to stain etches

R. W. Fathauer, T. George, A. Ksendzov, and R. P. Vasquez

Appl. Phys. Lett. 60, 995 (1992); http://dx.doi.org/10.1063/1.106485 (3 pages) | Cited 134 times

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Etching of Si in a variety of solutions is known to cause staining. These stain layers consist of porous material similar to that produced by anodic etching of Si in HF solutions. We have observed photoluminescence peaked in the red from stain‐etched Si wafers of different dopant types, concentrations, and orientations produced in solutions of HF:HNO3:H2O. Luminescence is also observed in stain films produced in solutions of NaNO2 in HF, but not in stain films produced in solutions of CrO3 in HF. The luminescence spectra are similar to those reported recently for porous Si films produced by anodic etching in HF solutions. However, stain films are much easier to produce, requiring no special equipment.
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78.55.Hx Other solid inorganic materials
81.65.-b Surface treatments
68.55.-a Thin film structure and morphology
81.40.Tv Optical and dielectric properties related to treatment conditions

InSb/In1−xAlxSb strained‐layer superlattices grown by magnetron sputter epitaxy

James B. Webb, G. H. Yousefi, and R. Rousina

Appl. Phys. Lett. 60, 998 (1992); http://dx.doi.org/10.1063/1.106457 (3 pages) | Cited 9 times

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The growth of strained‐layer superlattices of InSb/In0.6Al0.4Sb prepared by magnetron sputter epitaxy is reported for the first time. Individually controlled magnetron sputter sources of InSb, Al, and Sb were used to deposit 20‐period superlattices with periods ranging from 76 –154 Å. Layer thicknesses determined from x‐ray and cross‐sectional transmission electron microscopy (TEM) analysis were in close agreement with those predicted on the basis of the growth‐rate/deposition‐time product, indicating a high degree of deposition control. X‐ray and electron‐channeling patterns showed excellent crystallinity. The absence of surface features in the InSb cap layer indicated the layers to be under tensile stress due to the 2.1% lattice mismatch between InSb and InSb/In0.6Al0.4Sb.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Cd Deposition by sputtering

Photoelectrochemical conductivity selective etch stops for SiC

J. S. Shor, R. M. Osgood, and A. D. Kurtz

Appl. Phys. Lett. 60, 1001 (1992); http://dx.doi.org/10.1063/1.106502 (3 pages) | Cited 24 times

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Recent advances in SiC technology have demonstrated that the material is a potentially useful semiconductor for high temperature and high frequency applications. However, unlike silicon and GaAs, SiC is chemically inert, thus limiting the amount of etchants that can be effectively used to pattern devices. In fact, no patterning technique has been reported to date for SiC which shows high selectivity between p‐ and n‐type material. In this letter, we will show how an n‐type SiC epilayer can be patterned using photoelectrochemical etching, while a p‐type substrate underneath acts as an etch stop. This process is useful for the fabrication of electromechanical transducers, mesa structures, and bipolar and CMOS devices in SiC.
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81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer

Electronic structure of light‐emitting porous Si

R. P. Vasquez, R. W. Fathauer, T. George, A. Ksendzov, and T. L. Lin

Appl. Phys. Lett. 60, 1004 (1992); http://dx.doi.org/10.1063/1.106503 (3 pages) | Cited 129 times

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Characterization of light‐emitting porous Si films with x‐ray photoelectron spectroscopy is reported. Only traces of O are detected on HF‐etched samples, in contradiction to an earlier report that oxides are a significant component of porous Si. Si 2p and valence‐band measurements demonstrate that the near‐surface region of high porosity films which exhibit visible luminescence consists of amorphous Si.
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73.20.At Surface states, band structure, electron density of states
78.66.-w Optical properties of specific thin films
81.65.-b Surface treatments

Organometallic vapor phase epitaxial growth and characterization of GaInP/AlInP quantum wells on 10°‐off GaAs substrates using ethyldimethylindium

T. Y. Wang, D. F. Welch, D. R. Scifres, D. W. Treat, R. D. Bringans, R. A. Street, and G. B. Anderson

Appl. Phys. Lett. 60, 1007 (1992); http://dx.doi.org/10.1063/1.106504 (3 pages) | Cited 5 times

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GaInP/AlInP quantum wells (QWs) have been grown on (100) and 10°‐off (100) GaAs substrates in an organometallic vapor phase epitaxy (OMVPE) reactor at reduced pressure. Photoluminescence (PL) studies revealed an increase in peak energy and narrowing in linewidth for the 10°‐off QWs, due to the suppression of the formation of ordered microstructures during the OMVPE process. Low temperature PL results of GaInP/AlInP QWs as thin as 13 Å are presented for the first time. The 10°‐off QW showed a dominant peak at 551 nm, the shortest wavelength ever reported in GaInP/AlInP QWs. The origin of PL for the 13‐Å QWs is, however, different from that for thicker QWs as a result of the transfer of electrons to localized states in the barrier layer.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Microstructure of biepitaxial grain boundary junctions in YBa2Cu3O7

S. J. Rosner, K. Char, and G. Zaharchuk

Appl. Phys. Lett. 60, 1010 (1992); http://dx.doi.org/10.1063/1.106505 (3 pages) | Cited 19 times

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The microstructure of photolithographically defined 45° biepitaxial grain boundary junctions in YBa2Cu3O7 (YBCO) have been investigated by transmission electron microscopy. The junctions have been formed by growing YBCO and a buffer layer on a patterned MgO seed layer previously grown on r‐plane sapphire or SrTiO3 coated (through the use of suitable buffer layers) (100) yttrium‐stabilized‐zirconia substrates. SrTiO3 or CeO2 buffer layers grown on these patterned MgO substrates reproduced the pattern with two variants crystallographically rotated 45° with respect to each other about the surface normal. The morphology of the YBa2Cu3O7 grown on these differently oriented patterned regions show marked differences; in particular, the ion milling damage to the sapphire surface during patterning causes the formation of low angle grain boundaries. The locations of the weak link grain boundaries with respect to the patterning in the MgO seed layer have been identified using electron diffraction.
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68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects

Fabrication of TlCaBaCuO step‐edge Josephson junctions with hysteretic behavior

J. S. Martens, V. M. Hietala, T. E. Zipperian, G. A. Vawter, D. S. Ginley, C. P. Tigges, T. A. Plut, and G. K. G. Hohenwarter

Appl. Phys. Lett. 60, 1013 (1992); http://dx.doi.org/10.1063/1.106506 (3 pages) | Cited 12 times

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One way to create hysteretic Josephson junctions from the currently available nonhysteretic high temperature superconducting junctions is to artificially add capacitance. We have adapted a multilayer technique for artificial capacitance addition/grain boundary modification to produce TlCaBaCuO step‐edge junctions exhibiting large amounts of hysteresis at 77 K. A gaplike structure is present at 32–36 mV that has a temperature dependence that does not contradict that predicted by the Bardeen‐Cooper‐Schrieffer theory. In addition, the junctions show fast switching times, less than a fixture limited 20 ps, and Fraunhofer‐like dependence of critical current on magnetic field.
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85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates

Identification of epitaxial Y2O3 inclusions in sputtered YBa2Cu3O7 films: Impact on film growth

A. Catana, R. F. Broom, J. G. Bednorz, J. Mannhart, and D. G. Schlom

Appl. Phys. Lett. 60, 1016 (1992); http://dx.doi.org/10.1063/1.106507 (3 pages) | Cited 50 times

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Y2O3 inclusions with typical sizes between 100 and 300 nm3, densely distributed (1016 cm−3) in sputtered YBa2Cu3O7 (YBCO) films on SrTiO3 substrates, have been identified by high‐resolution electron microscopy. The precipitates exhibit either cuboid or needlelike shapes and grow epitaxially within and on top of YBCO. The dominant orientation relationship corresponds to a situation where the two‐dimensional lattices are nearly coincident in the interfacial (001) plane. These precipitates may contribute to the generation of screw and edge dislocations. In addition, they provide a large number of potential pinning sites for magnetic flux lines, which may contribute to the observed high critical current densities.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification

High critical‐current densities in (Tl0.5Pb0.5)Sr2Ca2Cu3O9 with Tc up to 115 K

R. S. Liu, D. N. Zheng, J. W. Loram, K. A. Mirza, A. M. Campbell, and P. P. Edwards

Appl. Phys. Lett. 60, 1019 (1992); http://dx.doi.org/10.1063/1.106508 (3 pages) | Cited 41 times

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A high critical‐current density was observed in the material (Tl0.5Pb0.5)Sr2Ca2Cu3O9. Based on magnetic‐hysteresis measurements, this single (insulating) Tl‐O layer material has a Jc value of 1.24×105 A/cm2 when measured at a temperature of 77 K and a field of 1 T. This value of Jc is comparable to that measured here for YBa2Cu3O7 (1.04×105 A/cm2), having single‐conducting Cu‐O chains, but considerably greater than the value for the material Tl2Ba2Ca2Cu3O10 with double (insulating) Tl‐O layers in which no hysteresis was observed under these same conditions. Our results from specific heat measurements indicate that the (Tl0.5Pb0.5)Sr2Ca2Cu3O9 compound has a three‐dimensional character due to the enhancement of the superconducting coupling along the c axis between the Cu‐O planes and thus results in an increase in Jc compared to the two‐dimensional Bi‐ and Tl‐2212 and 2223 [e.g., (Bi or Tl)2(Sr or Ba)2CaCu2O8 and (Bi or Tl)2(Sr or Ba)2Ca2Cu3O10, respectively] compounds. We believe that the high Jc is associated with an increase in the irreversibility field, rather than an increase in pinning centers.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents

Electrical characteristics of paraelectric lead lanthanum zirconium titanate thin films for dynamic random access memory applications

R. E. Jones, P. D. Maniar, J. O. Olowolafe, A. C. Campbell, and C. J. Mogab

Appl. Phys. Lett. 60, 1022 (1992); http://dx.doi.org/10.1063/1.106486 (3 pages) | Cited 26 times

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Paraelectric lead lanthanum zirconium titanate (PLZT) films, 150 nm thick, were deposited using a spin‐coat, sol‐gel process followed by a 650 °C oxygen anneal. X‐ray diffraction indicated complete conversion to the perovskite phase. Sputter‐deposited platinum electrodes were employed with the PLZT films to form thin‐film capacitors with the best combination of high charge storage density (26.1 μC/cm2 at 3 V and 36.4 μC/cm2 at 5 V) and leakage current density (0.2 μA/cm2 at 3 V and 0.5 μA/cm2 at 5 V ) reported to date. The electrical characteristics of these thin‐film capacitors meet the requirements for a planar bit cell capacitor for 64‐Mbit dynamic random access memories.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
84.32.Tt Capacitors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Generation of the pretilt angles in nematic liquid crystal (5CB) aligned on the rubbed polypyrrole films

Dae‐Shik Seo, Shunsuke Kobayashi, and Akihiro Mochizuki

Appl. Phys. Lett. 60, 1025 (1992); http://dx.doi.org/10.1063/1.106487 (2 pages) | Cited 21 times

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We have investigated the pretilt angles generated in the nematic liquid crystal 5CB media, aligned on polypyrrole (PP) films through rubbing. It is shown that the PP films may be synthesized with two kinds of counter ionic atomic groups, i.e., rheonium oxide (ReO−4) which can generate about 5° pretilt angles and bromide (Br−) where no pretilt angle is observed.
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61.30.-v Liquid crystals
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Using light as a stencil

M. Prentiss, G. Timp, N. Bigelow, R. E. Behringer, and J. E. Cunningham

Appl. Phys. Lett. 60, 1027 (1992); http://dx.doi.org/10.1063/1.106488 (3 pages) | Cited 31 times

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A new method for laterally manipulating the morphology of a thin film is presented, which uses the force exerted by light to deflect neutral atoms in an atomic beam during deposition. We have evaluated the dependence of the thickness of a thin metal film on the frequency, intensity, and the spatial structure of the light field, and find that the stimulated component of the force is suitable for laterally organizing atoms from centimeter to submicron dimensions.
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68.55.-a Thin film structure and morphology
37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
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