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  • 1
    Electronic Resource
    Electronic Resource
    Contour temperature programmed desorption for monitoring multiple chemical reaction products (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3719-3722 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple method for obtaining a comprehensive overview of major compounds desorbing from the surface during temperature programmed desorption (TPD) experiments is outlined. Standard commercially available equipment is used to perform the experiment. The method is particularly valuable when high molecular mass compounds are being studied. The acquisition of contour temperature programmed desorption (CTPD) spectra, sampling 50-dalton mass ranges at a time in the thermal desorption experiments, is described and demonstrated for the interaction of benzotriazole adsorbed on a Ni(111) surface. Conventional two-dimensional TPD spectra can be extracted from the CTPD by taking vertical slices of the contour. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149983
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Chevron structures in surface-stabilized ferroelectric liquid crystals (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3023-3028 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The computation of director profiles and energy parameters in surface-stabilized ferroelectric liquid crystal structures requires the evaluation of many terms accounting for different contributions to the general solution. This evaluation is usually performed using several simplifications and assumptions adapted to the specific phenomenon under study. In this work, a comprehensive expression including all possible terms not avoiding a computable solution is presented. The effect of every term on the general expression is analyzed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358651
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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Two new potentials for the free particle model (1999)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 5555-5564 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this work, is proposed a very simple method for obtaining the generalized potential associated with a known standard potential. The procedure is straightforward because it only uses two Ricatti-type relationships as enough condition to find a generalized potential; one particular equation is needed to identify the specific potential under study and one general Ricatti relationship is used to find the corresponding generalized potential. Moreover, the method is completely general due to the fact that an arbitrary potential has been considered in its development for which the procedure can also be used to find new potentials which could be needed in the modeling of important quantum interactions. The usefulness of the proposed approach, is shown with the treatment of the three- and one-dimensional potential for the free particle model. This work example leads to two new potentials whose Hamiltonians are isospectral when they are compared with the former Hamiltonian. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.533045
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  • 10
    Electronic Resource
    Electronic Resource
    Generalization of the Darboux transform (2001)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 42 (2001), S. 966-975 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: This article presents a generalization of the standard Darboux transform applied to Sturm–Liouville differential equations. This is achieved with the aid of an ansatz as a particular solution for the Riccati relationship involved, which in turn led us to obtain its generalized Darboux solution that contains, as a particular case, the standard Darboux transform. The proposed generalized Darboux transform (GDT), applied to the quantum mechanical field, gives the opportunity to prove the existence of standard and generalized Darboux potentials that match with the so-called isospectral potentials. This is exemplified by obtaining, through the GDT, a set of standard and generalized Darboux potentials that form the partner of the one-dimensional harmonic oscillator model for any quantum principal number. The worked example indicates how the GDT can be used to obtain the isospectral potentials associated to any known specific potential. We consider also the application of our method as proposed to the theory of solitons in order to show why the GDT will be important in other fields of application where the standard Darboux transform is usually concerned. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1334904
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