This study presents the fabrication of highly photosensitive undoped zinc oxide (ZnO) thin films for vacuum ultraviolet (VUV) radiation detection, covering the wavelength range of 100-200 nm. ZnO films were deposited using hybrid pulsed reactive magnetron sputtering, assisted by ECWR (electron cyclotron wave resonance) plasma. Control of the ECWR power (PECWR), ranging from 0 to 380 W, played a crucial role in enhancing the films' photoconductive properties. At PECWR = 200 W, the photosensitivity increased by 8 orders of magnitude compared to films deposited without ECWR assistance. This improvement was attributed to a sharp reduction in dark current due to lower defect density. Photoluminescence and cathodoluminescence spectra revealed a significant reduction in defect-related emissions for films deposited at PECWR = 200 W, confirming fewer intrinsic defects. Raman spectroscopy also showed a decrease in defect-related vibrational modes in the same films. Time-Resolved Microwave Conductivity (TRMC) measurements further supported these findings, demonstrating rapid recombination of charge carriers at 200 W, indicative of low trap densities. These results suggest that precise control of ECWR power allows for optimization of the defect concentration and crystallinity in ZnO films, paving the way for the development of high-sensitivity VUV photodetectors.

Biomedical Engineering Unit Department of Physiology Faculty of Medicine Kuwait University P O Box 24923 Safat 13110 Kuwait

Department of Mathematics and Natural Sciences Gulf University for Science and Technology Hawally Kuwait

Department of Physical Science and Engineering Nagoya Institute of Technology Gokiso cho Showa ku Nagoya 466 8555 Japan

Institute of Laser Engineering Osaka University 2 6 Yamadaoka Suita 565 0871 Osaka Japan

Institute of Physics of the Czech Academy of Sciences Na Slovance 2 Prague 8 182 00 Czech Republic

Joint Laboratory of Optics Palacký University Olomouc Av 17 listopadu 50A Olomouc 77207 Czech Republic

New Industry Creation Hatchery Center Tohoku University Sendai 980 8579 Japan

Unitec Institute of Technology 139 Carrington Road Mt Albert Auckland 1025 New Zealand

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Optical and Transport Properties of ZnO Thin Films Prepared by Reactive Pulsed Mid-Frequency Sputtering Combined with RF ECWR Plasma