Oxygen Effect on Structural and Optical Properties of ZnO Thin Films Deposited by RF Magnetron Sputtering

Abstract

ZnO thin films with wurtzite structure have been grown on Si (100) and glass substrates using radio frequency (rf) magnetron sputtering at room temperature. The ZnO thin films have been characterised by XRD. The (002) orientation is observed at zero Oxygen flow after the (100) developed with increasing oxygen ratio. Usually, this orientation (100) is difficult to obtain. The thickness of ZnO films was confirmed by cross-section SEM, and their stoichiometry was measured by Energy Dispersive X-ray Spectroscopy (EDX) and Rutherford backscattering spectroscopy (RBS). The optical band gaps have been determined using UV spectra and found to be varied from 3.24 to 3.29 eV as a function of the oxygen ratio. Moreover, photoluminescence (PL) spectra showed more defects at higher oxygen flow. The crystalline quality of the deposited film degrades with oxygen enhancements.

Oxygen Reduction Investigation on Sputtered ZnO Layers with Nano‐granular Structure

“…200 nm, prepared by thermal oxidation) [25] compared to native films (several nanometers thin) under droplets of zinc sulfate. [30][31][32][33][34][35][36][37][38] To the best of our knowledge, no synthesis of dense nanogranular ZnO layers using "one-step" sputtering (with no annealing post-treatment) has been reported before. In contrast, Thomas et al evidenced a protective effect of ZnO patinas grown under artificial seawater droplets.…”

“…The authors suggested a greater ability of the thick layers to reduce oxidizing species (such as O 2 molecules). [36][37][38] There seems to be a trend indicating that, when the O 2 partial pressure is increased, more randomly-oriented grains are observed in XRD experiments. [26] The patinas exhibited a significant gradient of porosity with an open structure on the electrolyte side and a compact one close to the zinc substrate.…”

“…[26] Finally, sputtering was chosen for its ability to producing thin oxide films as "model systems" in academic research with a large variety of nanostructures depending on the selected deposition parameters, such as target composition, nature of the reactive gases and power (among others). [30][31][32][33][34][35][36][37][38] To the best of our knowledge, no synthesis of dense nanogranular ZnO layers using "one-step" sputtering (with no annealing post-treatment) has been reported before. To obtain sputtered ZnO films with no preferred orientation, researchers modified the pressure of oxygen on the deposition procedure.…”

“…To obtain sputtered ZnO films with no preferred orientation, researchers modified the pressure of oxygen on the deposition procedure. [36][37][38] There seems to be a trend indicating that, when the O 2 partial pressure is increased, more randomly-oriented grains are observed in XRD experiments. Sasi et al deposited ZnO films on 3 C-SiC-on-Si substrates by using radio-frequency (rf) magnetron sputtering technique with zinc target, changing the O 2 /Ar gas ratio and annealing the layers at different temperatures.…”

“…Abdallah et al prepared ZnO thin films with rf-magnetron sputtering (with zinc oxide target) using glass as substrate and varying the oxygen flow rate. [37] No post-deposition heattreatment was done. They observed that increasing the flux of O 2 resulted in the decrease of the (002) orientation and in the appearing of the (100) reflection.…”