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  • 1
    Electronic Resource
    Electronic Resource
    Heavily doped CdTe films grown by close-spaced vapor transport technique combined with free evaporation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 184-187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Very heavily doped n-type polycrystalline CdTe films doped with metallic cadmium were prepared by using close-spaced vapor transport technique combined with free evaporation and the electrical, structural, and morphological properties were investigated. Cadmium was introduced as a dopant by evaporation during films preparation. The highest dark conductivity at room temperature of the films obtained was 1.18×104 S cm−1. The dark conductivity decreased with the increase of the ambient temperature. The highest dark electron concentration obtained was 1.59×1022 cm−3 and increased with the temperature. The mobility decreased with the temperature. The film was a polycrystalline cubic phase. We show the surface topography of the film using scanning electron microscope and scanning tunneling microscopy techniques, in order to see the growth patterns. The crystallite size was very uniform of a few μm, and the growth patterns on the grain surface were in form of terraces. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360929
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  • 2
    Electronic Resource
    Electronic Resource
    Electrochemical preparation of tungsten tips for a scanning tunneling microscope (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1917-1921 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present experimental results obtained during the electrochemical preparation of tungsten tips for a scanning tunneling microscope. Experiments were done with direct current and two kinds of electrolytes widely reported in the literature: KOH and NaOH. We report the effects of the applied voltage, time of etching, tip length, electrolyte concentration, wire diameter, and immersed portion as relevant parameters in the process. From the images obtained by a metallurgical microscope and a scanning electron microscope as well as from Auger and electron diffraction x-ray analysis the best conditions for W tip preparation were obtained. We found that KOH is better than NaOH as an electrolyte to prepare tips for scanning tunneling microscopy and that tip quality increases as the wire diameter and the immersed portion increases. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146996
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  • 3
    Electronic Resource
    Electronic Resource
    Simple rough approach system for scanning tunneling microscope (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2157-2159 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple rough approach system for a scanning tunneling microscope (STM) is presented. The system uses a commercial low velocity washing machine timer motor working at 127 VAC, 60 Hz in a continuous rotation. The motor moves a differential screw system and is controlled by an electronic circuit to stop its rotation when a preset value of tunnel current is detected. This rough approach system is simpler and less expensive than a stepping motor and does not use high voltage amplifiers. This mechanism can be easily adapted to STMs with mechanical approach systems because it consists of only a few simple components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144720
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  • 4
    Electronic Resource
    Electronic Resource
    Vibration isolation analysis for a scanning tunneling microscope (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3326-3329 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We analyze the efficiency of a vibration isolation system (VIS) for a scanning tunneling microscope as a function of the different parameters involved. The VIS consists of a stack of several metallic plates, separated by rubber elements with known properties. We show three-dimensional graphs obtained for different values of parameters such as rigidity (spring) constant (K), damping constant (C), mass (M), and the number of stages (n). Analyzing the K dependence of the position of the main peaks, we find a parabolic behavior when the damping constant is small, with a slight deviation for larger values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142547
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of scanning tunneling microscopy feedback system: Experimental determination of parameters (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 2947-2952 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the experimental work necessary on a scanning tunneling microscopy (STM) system to obtain some important feedback parameters—to have stability and good imaging conditions—such as the mechanical resonance frequency ω0, the delay time τ, and the damping factor ζ. We study and analyze each one of the main components involved on the STM such as the feedback system, the piezoelectric elements, the rigidity of the mechanical structure (the mechanical resonance), and its relation with the scanning rate for imaging. We conclude that it is necessary to obtain these parameters with the STM in tunnel conditions, in order to consider the effects of the tip, surface contamination, and tip sample interaction. We also conclude that tripod based STM can be better than STM based on piezo tubes scanners. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147077
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  • 6
    Electronic Resource
    Electronic Resource
    Auger electron spectroscopy study of silver incorporation in epitaxial Y–Ba–Cu–O superconducting films grown on MgO by laser ablation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2078-2080 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied by Auger electron spectroscopy the incorporation of silver in epitaxial YBa2Cu3O7 (YBCO) thin films fabricated by pulsed laser deposition using YBCO+Ag 10% targets. Films were grown on MgO substrates. The silver was found in a thin layer, of approximately 50 nm in depth. X-ray photoelectron spectroscopy confirmed that the Ag is in its metallic form. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115084
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of scanning tunneling microscopy feedback system (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3196-3203 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A theoretical analysis of the feedback system in the scanning tunneling microscope (STM) is presented. The proposed model includes all the elements involved in the STM loop. The knowledge of its behavior allow one to accurately determine the region where the unstable STM operation could affect the measurements, and also to set the optimal working parameters. Each element of the feedback circuitry is analyzed and discussed as well as their mutual interactions. Thus the stability region of a STM has been obtained analytically, using all the possible elements in the feedback loop and without using simplifications or rare models for the system. The mathematical models for each element of the loop has been used and the problem has been solved using control theory. Different working conditions are simulated and analyzed. Some relations for stability conditions, considering the value of each component involved in the feedback loop, are proposed and analyzed. The good agreement between theory and experimentation is shown by comparing images taken under conditions of good stability and of instability. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145551
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  • 8
    Electronic Resource
    Electronic Resource
    Connection between surface magnetism and electronic structure of oxygen on Ni(110) (invited) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3638-3640 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The d-band holes which give rise to ferromagnetism in Ni can be directly observed by spin-polarized inverse photoelectron spectroscopy (SPIPES). Only incident electrons polarized in the minority spin direction can fall into unfilled minority spin states and radiate a detected photon. On dissociative chemisorption of O2 we observe a reduction in the number of minority spin d holes. It is this change in electronic structure which gives rise to a decrease in magnetization. A background of minority and majority spin states remains essentially unchanged. Further exposure to oxygen causes formation of NiO; the surface magnetization goes to zero, and a completely different SPIPES spectrum is observed. The relative importance of d electrons and s, p electrons in chemisorptive bonding on Ni has been much discussed. These data suggest that the d states interact strongly with the oxygen and that this interaction has a profound influence on the surface magnetism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335028
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  • 9
    Electronic Resource
    Electronic Resource
    Sizing particles on substrates. A general method for oblique incidence (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 432-438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed an experimental light-scattering method to size metallic spherical and cylindrical particles on flat substrates using obliquely incident light. We modify an earlier model to include effects such as the shadowing of the incident and scattered beams. We provide empirical expressions for sizing spheres and cylinders on substrates based on the positions of their minima. The results have been experimentally verified for both types of particle. The extension of the method to oblique incidence angles allows an alternative dynamic procedure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369403
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon monoxide hydrogenation over Fe/HZSM-5 catalysts. Effect of SiO2/Al2O3 zeolite ratio (1993)
    Springer
    Catalysis letters 18 (1993), S. 65-71 
    Details
    ISSN: 1572-879X
    Keywords: Fe/HZSM-5 zeolite catalysts ; carbon monoxide hydrogenation ; infrared spectra of chemisorbed pyridine ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Iron catalysts supported on ZSM-5 zeolites of a wide range of silica-to-alumina ratios (29-∞) have been prepared and tested in carbon monoxide hydrogenation. The crystalline phases of the catalysts were characterized by X-ray diffraction and their acidity by infrared spectroscopy of adsorbed pyridine. The catalytic tests were conducted at 533 K, an overall pressure of 21 bar and a feed ratio CO/H2 close to 1. It was found that the selectivity to light olefins (C2–C4) increases in parallel with the increase of the Si/Al ratio of the zeolite. This was explained in terms of the decrease in Brønsted acidity of the catalysts. As a consequence, very high olefin selectivities can be achieved by decreasing the number of strong acid sites in the zeolite structure, but at the expense of high oxygenate formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769499
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