Structure, morphology, optical and electrochemical properties of indium- and aluminum-based nitride thin films deposited by plasma-assisted reactive evaporation / Mahdi Alizadeh Kouzeh Rash

Mahdi Alizadeh, Kouzeh Rash (2016) Structure, morphology, optical and electrochemical properties of indium- and aluminum-based nitride thin films deposited by plasma-assisted reactive evaporation / Mahdi Alizadeh Kouzeh Rash. PhD thesis, University of Malaya.

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Abstract

A plasma-assisted reactive evaporation system was developed for the growth of indium- and aluminum-based nitride thin films. The effects of the most influential growth parameters were investigated with respect to the structure, elemental composition, morphology and optical properties of these films. Decreasing the filament-to-substrate distance resulted in AlN thin films with reduced presence of metallic phase. The morphology of the films shifted from cauliflower-like to micro grain structure when the distance was reduced. RF power showed strong influence on the crystallinity, nitrogen incorporation and oxygen contamination in the InN film structure. An optimized RF power resulted in highly crystalline InN thin films with high nitrogen incorporation and lower oxygen contamination. The unavoidable presence of oxygen impurity in the InN film structure resulted in higher band gap energy values of 2.0−2.5 eV for films grown at various RF powers. This value is much higher than reported values of band gap energy for InN films. In-rich and Al-rich AlxIn1-xN films were prepared by simply varying the AC voltage applied to the filament holding the indium wire. The band gap energy of the films increased from 1.08 to 2.50 eV when the Al composition (x) varied from 0.10 to 0.64. Nitrogen flow rate also showed significant influence on the structure, morphology and optical properties of In-rich and Al-rich AlxIn1-xN films. Increasing the nitrogen flow rate resulted in enhancement of the agglomeration of the particles in the film structure. Increasing the nitrogen flow rate also decreased the Al composition in the films and this led to the decrease in the band gap energy of the films. The electrochemical properties of the deposited InN was studied and it was found that the films deposited at lower RF power showed better electrochemical behavior. The photoelectrochemical behavior of AlxIn1-xN thin films was also investigated. Thin films grown at high nitrogen flow rates with Al composition between 0.45 and 0.6 showed good photoelectrochemical behavior.

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