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Title: The metal photodissolution effect in spin-coated As-S films and its application in grating fabrication
Author: Hajto, Eva
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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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 As15S85-As40S60 was investigated. Infrared transmittance measurements show that the main structural unit of the spin-coated films is the AsS3 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 AsS3 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, Eo, and the oscillator dispersion energy, Ed, 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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available