SPIN-COATED AMORPHOUS CHALCOGENIDE FILMS
A number of amorphous chalcogenides have been successfully deposited as technologically useful thin films by the technique of spin-coating from solution. The resulting materials are amorphous and generally microstructure free retaining many of the properties of the starting solute. Amorphous chalcogenides such as As(,2)S(,3), As(,2)S(,2), and GeSe have been solubilized and deposited from solution. X-ray and electron diffraction have shown the materials to be amorphous; UV-visible transmission spectra of the materials have shown high absorption coefficients (-10('5) cm('-1)) at photon energies higher the optical energy gap(-2.5 eV).^ The chemical structure of these spin-coated materials has been investigated by nuclear magnetic resonance, infrared (IR) absorption, elemental analysis and transmission electron microscopy. A structural model is suggested based on As(,2)S(,3) clusters surrounded by amine as an amine salt. We call these new compounds alkyl ammonium arsenic sulfide or alkyl ammonium germanium chalcogenide. The proposed dissolution mechanism for chalcogenide in amine involves nitrogen lone pair donor electron transfer to an arsenic acceptor followed by proton transfer and formation of amine salt.^ The influence of annealing on solvent-cast arsenic sulfide films has been studied using IR spectrometry, mass spectrometry, thermogravimetric analysis, scanning calorimetry, transmission electron microscopy, X-ray diffractometry, UV-visible spectrometry, density measurement and elemental analysis. Results have shown that the materials undergo loss of amine and H(,2)S to cause densification in the materials during heating. H(,2)S removal is believed to be acompanied by cross-linking of glass domains resulting in a network glass containing only arsenic sulfur.^ Photoeffects on spin-coated arsenic sulfide have also been investigated. Silver photodoping has been observed and quantified. The edge sharpening effect in photolithography using silver doping of As(,2)S(,3) was observed. Photo-decomposition, crystallization and oxidation are believed to be responsible for the observed photobleaching effect.^ A detailed investigation using IR transmission spectroscopy as a tool has shown that a number of the arsenic and germanium chalcogenides react with a range of amines to form amine salts. The organic content of these amine salts can be removed with thermal annealing. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI ^
Engineering, Electronics and Electrical
GEENG-CHUAN MICHAEL CHERN,
"SPIN-COATED AMORPHOUS CHALCOGENIDE FILMS"
(January 1, 1984).
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