E. Adams

University of Vermont, Burlington, VT, United States

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Publications (14)25.54 Total impact

  • MRS Online Proceeding Library 01/2011; 422.
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    ABSTRACT: Ruthenium oxide nanorods have been grown on Si wafer substrates under a variety of pre-existing surface conditions by reactive radio frequency sputtering in an electron cyclotron resonant plasma process. Nanorod formation by this method is fast relative to that observed in other processes reported in the literature, with nucleation being the rate determining step. Growth in the axial direction is limited by the availability of ruthenium precursors which competes with their consumption in the lateral growth of the nanorods. The availability of Ru precursors at the top of the nanorods can be controlled by surface diffusion and therefore substrate temperature. The ultimate length of the nanorods is determined by the mole fraction of oxygen used in the reactor ambient through the production of mobile Ru hyperoxide precursors. The results of this investigation show the way to develop a process for producing a high density field of nanorods with a specified length.
    Nanotechnology 01/2008; 19(4):045611. · 3.84 Impact Factor
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    ABSTRACT: This paper describes the structural evolution and characterization of heteroepitaxial GaSb thin films on Si(111) substrates. The growth process used a combination of atomic sources which included the rf sputtering of Sb and the thermal effusion of Ga. The formation of crystalline GaSb thin films required that initially a monolayer thick Sb buffer layer be applied directly to a clean H-passivated Si(111) substrate surface. The resulting film was characterized by high resolution x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy, secondary ion mass spectroscopy, and atomic force microscopy (AFM). The AFM images were taken from the material after several periods of growth to determine the evolution of crystal structure with thickness. Atomic force microscopy images of the film surface showed that the heteroepitaxial layers were formed via the Stranski-Krastanov growth mechanism. This result is consistent with the heteroepitaxial growth of systems representing large differences in lattice constant. The hole mobility and carrier concentration in the deposited material were determined by the Hall measurement, performed at room temperature and on a 140 nm thick sample, to be 66 cm2/V sec and 3×1019 cm−3, respectively. The carrier mobility was relatively low as expected for measurements taken at room temperature.
    Journal of Applied Physics 04/2007; 101(7):073707-073707-7. · 2.21 Impact Factor
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    ABSTRACT: The heteroepitaxial growth of GaSb thin films on Si(100) and GaAs(100) substrates is presented. The growth technique involves the use of atomic Ga and Sb species, which are provided by thermal effusion and radio frequency sputtering, respectively. The crystalline quality of the heteroepitaxial GaSb film on the Si substrate is high despite the larger lattice mismatch. Epitaxial quality is determined by high-resolution x-ray diffraction and Rutherford backscatter spectrometry channeling. Atomic-force microscopy is used to monitor the evolution of surface morphology with increasing film thickness. Transmission electron microscopy shows the formation of stacking faults at the Si/GaSb interface and their eventual annihilation with increasing GaSb film thickness. Annihilation of stacking faults occurs when two next-neighbor mounds meet during the overgrowth of a common adjacent mound.
    Journal of Materials Research. 07/2004; 19(08):2315 - 2321.
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    ABSTRACT: The effect of surface preparation on the growth of epitaxial Si films by plasma enhanced chemical vapor deposition was investigated. The surface preparations considered were an ex situ ozone scrub and an in situ Ar/H2-plasma clean. Both methods were found to be effective at removing carbon contamination from the substrate surface which is critical for epitaxial growth. The thin-film quality was determined by Rutherford backscatter spectrometry, high-resolution x-ray diffraction, and transmission electron microscopy. To gain insight into mechanisms controlling the in situ cleaning process, hydrogen was replaced by deuterium in the plasma clean prior to film growth. The film/substrate interface was then analyzed by secondary ion mass spectrometry. Surprisingly, the plasma clean had little influence on the interfacial hydrogen concentration established by the previous hydrofluoric acid dip. It was found that hydrogen remains bound to C and O contaminants at the interface caused by the initial growth surface, and that neither an ex situ process containing an ozone scrub nor an in situ process containing a hydrogen-plasma clean could completely remove them. © 2003 American Vacuum Society.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2003; 21(3). · 1.36 Impact Factor
  • Journal of The Electrochemical Society - J ELECTROCHEM SOC. 01/2000; 147(12).
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    ABSTRACT: The single wafer processing of epitaxial Si films requires that special attention be paid to the design of the substrate heater assembly. This document describes the evolution and testing of an in situ heater used to deposit epitaxial Si films at temperatures as high as 700 °C. One problem encountered was the production of excessive levels of ultraviolet radiation which contributed to the desorption of water vapor from the vacuum chamber walls during the in situ cleaning process. A second problem involved the formation of a molybdenum containing film that poisoned epitaxial growth. A final proven in situ heater design is presented which avoids these problems.
    Review of Scientific Instruments 01/1999; 70:1821-1823. · 1.60 Impact Factor
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    ABSTRACT: Epitaxial growth of Er‐doped silicon films has been performed by plasma‐enhanced chemical vapor deposition at low temperature (430 °C) using an electron cyclotron resonance source. The goal was to incorporate an optically active center, erbium surrounded by nitrogen, through the use of the metalorganic compound tris (bis trimethyl silyl amido) erbium. Films were analyzed by Rutherford backscattering spectrometry, secondary ion mass spectroscopy, and high resolution x‐ray diffraction. The characteristic 1.54 μm emission was observed by photoluminescence spectroscopy. Previous attempts to incorporate the complex (ErO 6 ) using tris (2,2,6,6‐tetramethyl‐ 3,5‐heptanedionato) erbium (III) indicated that excessive carbon contamination lowered epitaxial quality and reduced photoluminescent intensity. In this study, chemical analysis of the films also revealed a large carbon concentration, however, the effect on epitaxial quality was much less destructive. A factorial design experiment was performed whose analysis identified the key processing parameters leading to high quality luminescent films. Hydrogen was found to be a major cause of crystal quality degradation in our metalorganic plasma‐enhanced process. © 1996 American Institute of Physics.
    Journal of Applied Physics 08/1996; · 2.21 Impact Factor
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    ABSTRACT: The limiting epitaxial thickness of Si films grown at a low substrate temperature by plasma enhanced chemical vapor deposition has been determined. The specific process used was electron cyclotron resonance plasma deposition. The limiting epitaxial thickness was found to decrease with the ratio of energetic ion‐to‐adatom arrivals on the substrate surface. The measured epitaxial thicknesses are similar to those obtained in previous investigations using molecular beam epitaxy. Hydrogen surface coverage does not appear to be a factor in limiting epitaxial thickness. The maximum epitaxial thickness remains to be determined for this process and substrate temperature range. © 1996 American Institute of Physics.
    Applied Physics Letters 01/1996; 68(3):349-351. · 3.52 Impact Factor
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    ABSTRACT: Epitaxial growth of erbium‐doped silicon films has been performed by plasma‐enhanced chemical vapor deposition using an electron‐cyclotron‐resonance source. The goal was to incorporate erbium as an optically active center (ErO 6 ) through the use of metal‐organic dopant sources. The characteristic 1.5 μm emission was observed by photoluminescence. Chemical analysis of the film revealed, however, that the organic ligands were decomposing and contributing to the carbon contamination of the films. Analysis of the molecular flux to the substrate indicated that the metal‐organic compound used, tris(2,2,6,6‐tetramethyl‐3‐5‐heptanedionato)erbium(III), was most likely to decompose, and supply unbonded atomic erbium and not the optical active species, ErO 6 . Excessive carbon contamination lowered epitaxial quality and reduced the photoluminescent intensity. Photoluminescent intensity was improved by a 600 °C anneal but was strongly quenched by a 900 °C anneal. The low‐temperature anneal improved crystal quality, and the high‐temperature anneal resulted in silicide formation. © 1995 American Institute of Physics.
    Journal of Applied Physics 12/1995; · 2.21 Impact Factor
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    ABSTRACT: Epitaxial Si films have been deposited at low substrate temperatures of 400 and 500 °C, by plasma enhanced chemical vapor deposition using an electron cyclotron resonance source. Samples were analyzed using Rutherford backscatter spectrometry, cross‐sectional transmission electron microscopy, and x‐ray diffraction. The ion‐to‐adatom arrival ratio was found to be an important parameter in determining epitaxial film quality. This ratio was controlled by the SiH4 feed rate, microwave power level, and shape of the magnetic field in the substrate region. Incident ion energy and ion flux were monitored with a gridded energy analyzer located at the substrate location. © 1995 American Institute of Physics.
    Applied Physics Letters 08/1995; 67(7):971-973. · 3.52 Impact Factor
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    ABSTRACT: Epitaxial Si films doped with Er have been grown at low substrate temperatures by plasma enhanced chemical vapor deposition. The Er gas source is a sublimed organometallic compound fed into the process chamber. High doping concentrations without silicide precipitation are possible because of the low deposition temperatures. The process relies on the beneficial effects of low energy ion bombardment to reduce the growth temperature. The ions as well as reactive chemical species are produced by an electron cyclotron resonance plasma stream source. A hydrogen/argon plasma is used to perform an in situ predeposition clean to remove oxide from the Si surface. Film quality and impurity concentration are determined by Rutherford backscattering spectrometry and secondary ion mass spectrometry.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 10/1994; · 1.43 Impact Factor
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    ABSTRACT: Deposition of Y 2 O 3 films on Si is of interest due to its use as a heteroepitaxial dielectric material to obtain Si‐on‐insulator or as an epitaxial buffer layer for the growth of YBa 2 Cu 3 O x , high temperature superconductors on Si. In this investigation, Y 2 O 3 films have been deposited in the downstream location in an electron cyclotron resonance oxygen plasma using an organometallic Y source. The reactor pressure was varied which resulted in changes in the ionic and atomic oxygen flux as well as the energetic ion bombardment of the substrate. The deposited material has been characterized by reflected high‐energy electron diffraction, x‐ray diffraction, Rutherford backscattering spectrometry, and atomic force microscopy. The majority of the films appear to be highly oriented, textured films. Deposition of the (111) phase is preferred, even on the (100) substrate.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 08/1993; · 1.43 Impact Factor
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    ABSTRACT: Thin films of silicon dioxide were deposited at low substrate temperatures (≪375 °C) using electron cyclotron resonance plasma enhanced chemical vapor deposition. The deposition parameters studied included substrate temperature and radio frequency substrate bias. The deposited material was compared to thermally grown SiO 2 , through its etch rate in a buffered hydrofluoric solution, index of refraction, Fourier transform infrared spectroscopy, and Rutherford backscattering spectrometry. Through the application of rf substrate bias the deposited material properties approached that of thermally grown oxide. The feed to the substrate chamber was 40 sccm of a 2.0% silane in He. The large quantity of He in the chamber is credited with making the material more thermal‐like.
    Journal of Applied Physics 09/1992; · 2.21 Impact Factor