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  • 1
    Electronic Resource
    Electronic Resource
    Microwave-mixing scanning capacitance microscopy of pn junctions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 7094-7099 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe an approach to scanning capacitance microscopy. A mixing technique is employed for imaging local capacitance variations simultaneously with the sample topography using an atomic force microscope (AFM) with a conductive tip. A SiO2/Si sample with lateral pn junctions formed by ion implantation has been investigated. Microwave signals incident on the metal–oxide–semiconductor (MOS) structure formed by the AFM tip and the sample give rise to mixing signals due to the nonlinear voltage dependence of the space charge capacitance in the Si. In our experiments two microwave input signals with frequencies f1 and f2 and a variable dc bias voltage were applied to the tip-sample MOS structure. The dependence of the generated sum frequency and third harmonic signals on the dc sample voltage shows that the f1+f2 and 3 f signals are proportional to dC/dV and d2C/dV2, respectively. Images of the sum frequency and third harmonic signals delineating the pn junctions on our model sample are presented and the dc bias voltage dependence of the images is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371797
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic reversal of tapered permalloy bars with holes in the center (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4601-4603 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic reversal mechanism of tapered permalloy bars with holes in the center was studied using a Magnetic Force Microscope with in situ magnetic field capability. The samples studied were lithographically patterned from a 20-nm-thick NiFe film using a subtractive process to create tapered bars 18 wide×348 μm long. The easy axis of the permalloy is parallel to the long axis of the bar. In the center of the tapered bar was either a 10, 5, or 3 μm diameter hole. The remnant state after saturation parallel to the long axis of the bar is a large domain magnetized along the saturating field direction except near the hole. The magnetization at the edge of the hole can be explained by considering edge pinning and the last direction of a saturating magnetic field. An inplane magnetic field parallel to the long axis of the bar reverses the magnetization by domain nucleation at the edge of the hole. After the bar has reversed, the same type of wall structure is seen as in the remnant state. As the magnetic field is increased further, the magnetization rotates away from parallel to the edge of the hole, as seen by the emergence of surface poles along the hole edge. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370421
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  • 3
    Electronic Resource
    Electronic Resource
    Microwave-frequency alternating current scanning tunneling microscopy by difference frequency detection: Atomic resolution imaging on graphite (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3377-3380 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a detailed description of an experimental setup for alternating current scanning tunneling microscopy, in which two slightly detuned high frequency signals are mixed at the tunneling junction and the resulting difference frequency signal is amplified using conventional scanning tunneling microscope electronics. This signal is used to control the distance between the microscope tip and the sample. With graphite as a model surface atomic resolution images have been obtained. It is demonstrated that the origin of the generated signal on graphite is the nonlinearity of the static current–voltage characteristics. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149922
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  • 4
    Electronic Resource
    Electronic Resource
    An insert for single-molecule magnetic-resonance spectroscopy in an external magnetic field (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4853-4856 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an insert for optical and magnetic-resonance experiments on single molecules in a solid matrix at liquid-helium temperatures. The experimental arrangement allows in situ adjustment of the focusing lens and of the sample. A parabolic mirror serves to collect the fluorescence emission and to direct the light onto a photodetector. Microwaves can be irradiated through a coil around the sample while a superconducting magnet provides the possibility of a stationary magnetic field. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146164
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  • 5
    Electronic Resource
    Electronic Resource
    Compact ultrahigh vacuum sample exchange device with wide temperature range (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 313-314 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design and performance of a compact ultrahigh vacuum sample holder, which allows (1) sample transfer, (2) liquid-nitrogen cooling, (3) heating by electron bombardment, and (4) temperature measurement in direct proximity to the sample. The device operates from close to liquid-nitrogen temperatures up to temperatures of 800–900 K in the steady-state regime with peak temperatures in excess of 1700 K and allows easy and reliable sample transfer. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148526
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  • 6
    Electronic Resource
    Electronic Resource
    Annealing-induced effects on the stability of hydrogenated amorphous silicon (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5959-5964 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We performed isothermal annealing on a hydrogenated amorphous silicon (a-Si:H) sample deposited at low temperature in a glow discharge reactor. In order to change the hydrogen bonding configuration without affecting the silicon structure we choose a relatively low annealing temperature. We studied the dependence on the annealing time of the dark conductivity, photoconductivity, light-induced degradation of the photoconductivity, optical gap, vibrational spectra, and subgap defect density. As the annealing time increased we found an increase in the dark conductivity activation energy. This shift of the dark Fermi level toward the valence band was correlated with the growth of a peak in the density of states below midgap. From the vibrational spectra we obtained the microstructure parameter, which is indicative of the amount of hydrogen bonded as polihydrides and/or to some sort of internal surface. We used the bond-breaking model to fit photoconductivity decay as a function of illumination time, and we found a correlation between the Staebler–Wronski susceptibility and the microstructure parameter. This would mean that the stability of the material concerning light-induced degradation is related to the way hydrogen is attached in the amorphous network. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360598
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  • 7
    Electronic Resource
    Electronic Resource
    Correlation between giant magnetoresistance and magnetic interactions in a CoAg multilayered/granular system (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2466-2471 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetizing, demagnetizing, and remanent magnetization curves for [Co(12 Å)/Ag(60 Å)]×15 multilayered/granular films thermally treated have been measured. The changes of the giant magnetoresistance and the interaction effects have been explained as a result of the structural, morphological, and magnetic evolution of the samples as a function of the thermal treatment. It has been inferred that for samples annealed at temperatures lower than 360 °C, the changes of the giant magnetoresistance come from the misalignment of the magnetic moments of the Co particles formed during annealing. A strong correlation between the giant magnetoresistance and the magnetic interaction effects has been found for samples annealed at temperatures higher than 360 °C: the giant magnetoresistance is degraded as the demagnetizing interparticle interactions are increased. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366058
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  • 8
    Electronic Resource
    Electronic Resource
    Limitations of the constant photocurrent method: A comprehensive experimental and modeling study (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 339-348 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental and modeling results for the subgap absorption coefficient of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) in order to explore the limitations of the constant photocurrent method (CPM). To properly model the subgap absorption coefficient, we have developed a simulation computer program including all the possible optical and thermal transitions between gap and extended states. Tail states are assumed to be either donor- or acceptorlike and midgap states are assumed to be amphoteric. The defect-pool model is also incorporated in our analysis. We have fitted several experimental dc-CPM spectra by using a standard set of parameters for the density of states. Our analysis demonstrates that in undoped samples the true absorption coefficient and the density of midgap states are underestimated by the CPM measurement. This is due to a nonconstant electron lifetime in the energy range between 0.8 and 1.2 eV. On the other hand, we show that in n-doped or p-doped samples, the CPM provides the correct answer. The energy range for the Fermi level where the CPM fails in a-Si:H is clearly established. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366688
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  • 9
    Electronic Resource
    Electronic Resource
    Negative remanent magnetization of fine particles with competing cubic and uniaxial anisotropies (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1488-1492 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of noninteracting single-domain particles whose anisotropy is made up of a cubic magnetocrystalline and a uniaxial components were investigated. Various directions of the uniaxial anisotropy were considered and the dependencies of the reduced remanence as a function of the ratio between the two anisotropies were obtained. It was found that for sufficiently strong uniaxial anisotropy and random arrangement of the particle orientations, reduced remanence lower than 0.5 is, in general, an intrinsic property of the system due to the negative remanent magnetization of some of the particles. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368214
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  • 10
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance and remanence in granular CoCu codeposited films : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7007-7009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental magnetoresistance, magnetization, and remanence data for CoCu granular films obtained by electron beam codeposition, subsequently submitted to a thermal treatment. The magnetization measurements show coexistence of superparamagnetic and ferromagnetic (or blocked superparamagnetic) Co grains. By modeling the experimental magnetization curves, the distribution function of the superparamagnetic particle size, the volume fraction of the blocked part of the Co particles, and their saturation magnetization are obtained. δM plots are constructed using the remanence curves. A correlation between the changes of the δM parameters and those of the giant magnetoresistance, caused by the annealing, is discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367808
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