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Undoped Zinc oxide (ZnO) was successfully deposited on silicon (100) substrate by femtosecond pulsed laser deposition. A mode-locked femtosecond laser operating at 790 nm wavelength, 100 fs pulse duration and 80 MHz repetition rate was used as an excitation source. The depositions were carried out at vacuum pressures of 10-2-10-6 mbar and oxygen background gas pressures of 10- 2-10-4 mbar. Energy dispersive spectroscopy of samples grown without oxygen background gas shows higher zinc composition on deposited material as compared to oxygen that leads to offstoichiometric ZnO films. Scanning electron microscopy (SEM) images shows that increasing oxygen gas pressure increased the particle size of the deposited ZnO. The material deposited at 2x10-4 mbar oxygen pressure revealed clustering of nanorods forming a flower-like structure that has an average length of 2700 nm and an average diameter of 450 nm. The X-ray diffraction spectra show c-axis orientation of the deposited ZnO with (002) and (110) reflection.
DOI: 10.2961/jlmn.2016.01.0004
Keywords: pulsed laser deposition, deposition growth, laser ablation, femtosecond techniques, film deposition
1. Introduction
For the past years, there has been great interest in the production of transparent conducting oxide (TCO) and transparent oxide semiconductors for optical applications such as surface acoustic wave (SAW), acoustic-optic, and piezo-optic [1, 2]. Zinc oxide (ZnO) is a novel photonic material with properties similar to Gallium nitride (GaN) such as wide direct band gap (3.3eV), large exciton binding energy (60meV) and high melting temperature of 2248K [2, 3]. The fabrication of ZnO films has been employed by various techniques including thermal evaporation, laserassisted ablation, chemical vapor deposition, sputtering, sol-gel, molecular beam epitaxy and pulsed laser deposition (PLD) [3, 4]. Among these techniques, PLD has proved to be a suitable method to produce high quality thin films at relatively lower substrate temperature [3, 5].
PLD is a thin film deposition technique that uses a pulsed laser focused onto target to create plasma. The target material is vaporized by the high laser intensities. This ejected materials travels towards a substrate to form a thin film [6]. PLD has been widely used in production of thin films due to its other inherent advantages which include stoichiometric transfer of material, high deposition rate, high film adherence, simple set up and ability to control film thickness [3,...