Study of the Optical Properties of Silicon Dioxide Thin Films Prepared by Nd: YAG Pulsed Laser Deposition

Abstract

The field of this research is thin films fabrication using pulse laser deposition technique. The main objectives of this work were to fabricate some oxide (such as SiO2) thin films using pulsed laser deposition technique (PLD) and to study the optical properties of the fabricated thin films. Also this research aimed to study the effect of laser parameters (properties) mainly the laser pulse energy and pulse repetition rate on the optical properties at certain wavelengths (transmission spectra, refractive indices and absorption coefficients) of the fabricated thin films. In this research silicon dioxide (SiO2) thin films were deposited on glass substrate from SiO2 solid disk using pulsed laser deposition technique. In this technique a Q-Switch Nd: YAG laser emitting the fundamental wavelength 1064 nm with pulse duration of 10 nanosecond was used to produce nine samples of SiO2 thin films, five of them were fabricated by changing the pulse energy and the four samples were deposited by varying the pulse repetition rate. The fabricated SiO2 thin films were inspected and each film thickness was measured using scanning electron microscope MIRA3 type. Then the transmission spectrum at certain wavelengths from different monochromatic light sources for each film was recorded. SiO2 thin films transmission data and the measured films thicknesses were used to deduce their optical properties. The results showed that increasing the laser pulse energy results in an increase of the film thickness from 0.39 μm when the laser pulse energy was 100 mj to 0.71 μm when the laser pulse energy was 250 mj, and the morphology of the films becomes more dense and non-smooth at higher pulse energy, also the optical properties showed to be affected by the thickness variation and hence by the laser pulse energy. The results also showed that V increasing the pulse repetition rate results in an increase of the film thickness from 0.39 μm at 2 Hz repetition rate to 1.04 μm when the pulse repetition rate was 5 Hz and it was noticed that increasing the pulse repetition rate results in more dense and non-smooth film morphology. Also the optical properties of the produced films were found to be highly dependent on the film thickness and hence on the pulse repetition rate used in fabrication of films. The results showed that the transmission spectra of the samples were in the range from (0.85 to 0.97) %. And The optical absorption coefficients of the samples were varied from 38.461*103 cm-1 and 12.250 *103 cm-1 depending on the thickness of the thin film, and the refractive indices were found to be varied from 1.43 to 1.67 with the wavelengths from 532 nm to 915 nm, and the optical properties (transmission spectra, refractive indices, and the absorption coefficients) of the SiO2 thin films were in good agreement with literature.