The deposition of chalcogenides from their solutions using the spin-coating technique offers a new possibility for preparing technologically useful thin films in an easier way than the conventional vacuum techniques. This study descibes the use of the spin-coating technique to prepare chalcogenic thin films from their propylamine solutions. The composition range As<SUB>15</SUB>S<SUB>85</SUB>-As<SUB>40</SUB>S<SUB>60</SUB> was investigated. Infrared transmittance measurements show that the main structural unit of the spin-coated films is the AsS<SUB>3</SUB> pyramid. IR Spectroscopy also indicates that the amine group of the solvent propylamine molecule plays the dominant role in the dissolution process. The solvent/chalcogenide interaction was found to occur at the S-sites of the AsS<SUB>3</SUB> structural units of the chalcogenide. The dispersion of the refractive index, n(λ), for undoped and Ag-doped spin-coated As-S films was measured and shows that these films are transparent in the λchar61 1-10 μm spectral region. The refractive index values were fitted with the single oscillator expression and the oscillator energy, E<SUB>o</SUB>, and the oscillator dispersion energy, E<SUB>d</SUB>, for spin-coated films were determined. These values provide further information about the structure of these films. The values of the absorption coefficient, α, for a range of compositions of spin-coated As-S films and also for silver photodoped spin-coated As-S films at the optical absorption edge were calculated, and the band gap energy, E_g, for these films determined. The compositional dependence of E_g is explained by the bond strengths of the different bonds in the films. The preparation of holographic diffraction gratings in spin-coated As-S films by silver photodissolution and subsequent selective etching using CF_4 plasma is described. The diffraction efficiency of the surface relief gratings yielded a similar value to that for gratings prepared in vacuum-evaporated films.
|University of Edinburgh
|Electronic Thesis or Dissertation
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