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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3353-3362 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Clean polyimide films spin-coated onto gold substrate have been fully characterized by high resolution electron energy loss spectroscopy (HREELS): 19 electron-induced vibrational bands could be resolved and assigned by comparison with IR spectroscopy. The attribution of these peaks constitutes a firm and necessary basis for the detailed study of the incipient interface formation with aluminum at room temperature. The metal being evaporated at a low rate from a Knudsen effusion cell, its equivalent coverage on the polymer could be monitored very efficiently and allowed a clear distinction between three reaction steps: (i) at an Al coverage below 4×1014 Al atom/cm2, the aluminum atoms interact only with the C–O carbonyl in the polymer to form a C–O–metal complex; (ii) between 4 and 10×1014 atom/cm2, no further Al "reaction'' occurs, but the appearance of new CH and OH stretching bands is attributed to bond breaking in the polymer and diffusion of the residues towards the surface; (iii) after further metal evaporation, all the peaks reduce in intensity and the observation of a ν(Al–O) [or ν(Al–C) band] testifies the formation of an aluminum oxide (or carbide) at the surface. Although no dedicated theory can be invoked up to now for the interpretation of HREELS data collected with different electron impact energies and under different scattering geometries, the spectra measured from polyimide before and after aluminum condensation are consistent with a modification of the geometry of the polymer monomeric unit after bonding with the metallic atoms. The metallized polymer surface appears with an equal statistical spatial distribution of all the chemical groups.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 253-257 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a valence effective Hamiltonian (VEH) electronic structure calculation on the polyimide poly[N,N'-bis(phenoxyphenyl)-pyromellitimide], also called PMDA (pyromellitic dianhydride)–ODA (oxydianiline). The most important result is that the valence electronic bands are calculated to be very narrow, even though the calculation is performed on a perfectly stereoregular chain. For instance, the highest 35 occupied valence bands (i.e., the electronic bands with binding energies lower than 18 eV) have widths smaller than 0.25 eV. That result implies that even small disorder effects will tend to strongly localize the electronic processes in polyimide. From the band structure, we calculate the density of valence states and produce a theoretical simulation of the UPS spectrum. Good agreement with the recently published UPS experimental spectrum is obtained.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6739-6749 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe high resolution electron energy loss (HREELS) and UV-photoemission (UPS) measurements performed to investigate the vibrational and electronic surface and interfacial properties of thin insulating polymer films. The measurements were performed in ultrahigh vacuum on PMDA–ODA films of thicknesses ∼30–50 and ∼1000 A(ring) which were spun onto silicon or onto metallic substrates and on thin PMMA films deposited on metallic substrates. The general characteristics of our HREELS spectra are weak, diffuse electron scattering and broad vibrational bands which we have assigned by comparison to infrared absorption data. Cooling the polymer films which were spun onto Si substrates to ∼100 K resulted in a uniform reduction of the overall spectral broadening. This additional inelastic scattering contributing to the broadening appears to originate at the PMDA–ODA/Si interface.
    Type of Medium: Electronic Resource
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