In this study, the electrical and optical properties of Zn doped tin oxide films prepared using sol-gel spin coating process have been investigated. The SnO 2 : Zn multi-coating films were deposited at optimum deposition conditions using a hydroalcoholic solution consisting of stannous chloride and zinc chloride. Films with Zn doping levels from 0-10 wt% in solution are developed. The results of electrical measurements indicate that the sheet resistance of the deposited films increases with increasing Zn doping concentration and several superimposed coatings are necessary to reach expected low sheet resistance. Films with three coatings show minimum sheet resistance of 1⋅ ⋅479 kΩ Ω/ in the case of undoped SnO 2 and 77 kΩ Ω/ for 5 wt% Zn doped SnO 2 when coated on glass substrate. In the case of single layer SnO 2 film, absorption edge is 3⋅ ⋅57 eV and when doped with Zn absorption edge shifts towards lower energies (longer wavelengths). The absorption edge lies in the range of 3⋅ ⋅489-3⋅ ⋅557 eV depending upon the Zn doping concentration. The direct and indirect transitions and their dependence on dopant concentration and number of coatings are presented. Keywords. Transparent conducting oxides; electrical and optical properties; tin oxide films; zinc doping; spin coating.

A theory of free carrier absorption is given for GaAs/GaAlAs quantum wells when the carriers are scattered by confined LO phonons. The Huang and Zhu approximation for the confined phonon modes is used. The absorption coefficient is calculated and is found to have, broadly, features similar to the calculations with bulk phonons. The well width dependence of absorption is found to be opposite to that exhibited by scattering rates.

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The effects of electron beam irradiation on the electrical and the optical properties of zinc oxide (ZnO) and aluminum-doped zinc oxide (ZnO:Al) thin films, prepared by the sol-gel technique, were investigated. The grain size, surface morphology, sheet resistance, optical constants, absorption edge, and direct and indirect optical band gaps of these films were analyzed before and after exposure to electron beam. The decrease in the structural homogeneity and the crystallinity of the films after exposure to electron irradiation is observed. The irradiation causes increase in the sheet resistance and blueshift in the absorption edge for both ZnO and ZnO:Al films. The change in carrier concentration due to doping as well as the exposure to electron beam are responsible for the modified electrical and optical properties.

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A theory of phonon-assisted cyclotron resonance in quasi-two-dimensional semiconductor quantum-well structures is given. Using perturbation technique, expressions for absorption coefficients are obtained when the electrons are scattered by acoustic, nonpolar, and polar optical phonons. Extra peaks in the absorption spectrum due to transitions between Landau levels accompanied by emission and absorption of phonons are predicted. Numerical results for the frequency, magnetic field, and temperature dependence are given for parameters characteristic of GaAs.

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Phonon-assisted cyclotron resonance ͑PACR͒ in a free-standing quantum well ͑FSQW͒ structure is studied when electrons are scattered by confined-acoustic modes through deformation potential. Elastic continuum model is employed to describe the confined-acoustic modes, that are classified as shear, dilatational, and flexural waves. Expression for the absorption coefficient is obtained. Numerical results are presented for the frequency, magnetic field, temperature, and well-width dependence of absorption coefficient in GaAs and GaN free-standing quantum well structures. In the extreme quantum limit only dilatational modes contribute for phonon-assisted cyclotron resonance. Results are compared with those based on bulk description of acoustic phonons and significant differences are noted. The calculations demonstrate that phonon-assisted cyclotron resonance studies can lead to a better understanding of confined electron-acoustic phonon interaction in freestanding quantum wells.