|Title:||Optical absorption of dual-ion-beam deposited silicon nitride films|
Hong Kong Polytechnic University -- Dissertations
Department of Applied Physics
|Pages:||iv, 46 leaves : ill. ; 30 cm|
|Abstract:||The optical absorption of amorphous silicon nitride (SiNx) films with x varying from 0 to 1.36 were investigated. The films were prepared by sputtering a Si target with concurrent N2+ beam assist. The composition and structure of the films were investigated by X-ray photoelectron spectroscopy (XPS) and infrared absorption (IR). The optical absorption spectra of the films were measured by a double-beam spectrophotometer ranging from 1.4 to 5.0 eV and the results were expressed in Tauc plots. An optical absorption model was used to fit the Tauc plots. All types of electron transitions from occupied initial states and empty final states were considered, including those between two localized states. In order to have good fittings, band tails and Gaussian-band were added. By adjusting the parameters used in the optical absorption fitting model, the DOS of the films were established. The following were the major findings in this study. As x increases from 0 to 1.36, the optical band gap increases from 1.1 to 3.9 eV, the band tails increases from 3.0 x1020 to 4.3 x1020 eV-1cm-3, the Gaussian peak drops from 3.0x1020 to l.2x1020 eV-1cm-3, the Gaussian width increases from 0.02 to 0.50 eV and density of electron states (DOS) at the mid-gap drops from 4.9x1020 to l.2x1020 eV-1cm-3.|
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