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  • 1995-1999  (8)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Novel Optical Spectroscopy of Individual Nanostructures: STM Light Emission Spectroscopy (1996)
    Springer
    The chemical educator 1 (1996), S. 1-14 
    Details
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00897960047a
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of molecular orientation of very thin rubbed and unrubbed polyimide films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 431-439 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To determine the molecular orientation of rubbed and unrubbed poly[4,4′-oxydiphenylene- pyromellitimide] (PMDA-ODA) films, we have measured the infrared (IR) absorption spectra of PMDA-ODA films on Si substrates as a function of the incident angle. The molecular orientation was determined by fitting the incident angle dependence and the IR dichroic ratio with the theoretical curves. The IR absorption was calculated by a transfer matrix method to take account of the multiple reflection and refraction at the interfaces. The vibrational response of the polyimide film in the IR region was represented by a Lorentz oscillator model. We found that the molecules in a spin-coated polyimide film are oriented parallel to the substrate surface with a standard deviation of 6.5°. For a rubbed film, the polymer chains are oriented along the rubbing direction and are tilted up on average by 8.5° from the surface plane. We observed a blueshift of the C=O asymmetric stretching band at oblique incidence. The blueshift is explained by anomalous dispersion of the dielectric constant of the polyimide film, and is reproduced by our calculation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362744
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Light emission spectra of AlGaAs/GaAs multiquantum wells induced by scanning tunneling microscope (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1544-1546 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the scanning-tunneling-microscope light emission (STM-LE) spectra of p-Al0.4Ga0.6As/p-GaAs multiquantum wells. The injection current level was kept as low as 0.1–0.5 nA to ensure that the sample is not damaged by the tunneling current. This is the current level ordinarily used for taking STM images. The peak energy of the emission shifts to the high energy side with decreasing well widths. A corresponding peak shift behavior was also observed in the photoluminescence (PL) spectra for the same samples. From comparisons of the STM-LE and the PL spectra, we find that although there is a difference in the excitation process, the final recombination process is identical in both cases. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122200
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation of silver tips for scanning tunneling microscopy imaging (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 4010-4011 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple reliable preparation method of silver tips for scanning tunneling microscopy imaging with atomic resolution is presented. The procedure is based on two-step electrochemical processing; ac electropolishing and subsequent dc electroetching. The quality of the tip is improved by applying high bias voltage pulses while the tip is within tunneling range. This indicates that the end of the tips are sharpened by field evaporation of silver ions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149215
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  • 5
    Electronic Resource
    Electronic Resource
    Light emission spectra of individual GaAs quantum wells induced by scanning tunneling microscope (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2289-2291 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the light emission from individual single GaAs quantum wells of cleaved (110) AlGaAs/GaAs heterostructures, using the scanning tunneling microscope tip as a local injection source of minority carriers. Single emission peaks were observed to shift to the high-energy side with decreasing well width. The emission peaks are assigned to the transition between n=1 single-quantum-well electron and heavy-hole states of the respective wells. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124993
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  • 6
    Electronic Resource
    Electronic Resource
    Surface anisotropy of polyimide film irradiated with linearly polarized ultraviolet light (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1832-1834 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using polarized infrared (IR) absorption, we have investigated the surface anisotropy of a poly [4, 4′-oxydiphenylene-pyromellitimide] (PMDA-ODA) film that arises from anisotropic decomposition of the polyimide chain during irradiation with linearly polarized ultraviolet (LPUV) light. To monitor the surface anisotropy, we designed the sample structure so that the polyimide films decomposed uniformly over the entire film thickness. The surface anisotropy has a maximum at an irradiation energy of 105 J/cm2. For PMDA-ODA, the maximum surface anisotropy is significantly smaller than the surface anisotropy generated by rubbing. By analyzing the irradiation energy dependence of an IR absorption band, we found that the decomposition rate of the polyimide chain oriented parallel to the polarization direction of the LPUV light is greater only by ∼23% than that oriented perpendicular to it. This is the reason for the small surface anisotropy induced by the LPUV light irradiation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121198
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  • 7
    Electronic Resource
    Electronic Resource
    Visible light emission spectra of individual microstructures of porous Si (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2536-2538 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the spectra of visible light emitted from the individual structures of porous Si (PS) below the probe tip of the scanning tunneling microscope (STM), and found that the peak energy of the emission spectrum shifts with the size of nanometer-scale structures on the PS surface. Samples with a PS layer ∼50 nm thick were formed by anodic etching of p+Si(100) substrates (∼0.005 Ω cm). The STM images show that protrusions whose dimensions are 3–10 nm in diameter are distributed on the PS surface. The peak energy of the STM light emission spectrum shifts from ∼1.7 to ∼2.1 eV as the diameter of the structure below the STM tip decreases from ∼9 to ∼3 nm. The measured peak shift with the size of the structure is consistent with the shift of the energy gap predicted on the basis of a quantum confinement model. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114450
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  • 8
    Electronic Resource
    Electronic Resource
    Correlation between the pretilt angle of liquid crystal and the inclination angle of the polyimide backbone structure (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2755-2757 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have determined the inclination angle of the backbone structure of polyimide with alkyl side-chains in rubbed films. Four different polyimides with the same backbone structure but different lengths of alkyl side-chains were used in this study. The inclination angle of the backbone structure increases with the number of carbon atoms in the alkyl side-chains. We found a linear relation between the inclination angle of the backbone structure and the pretilt angle of liquid crystal (LC) that is in contact with the polyimide films. We conclude that the inclination of the polyimide backbone structure determines the pretilt angle of LC. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119566
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