Preparation of Pristine ZnO Thin Film for UV Photodetector Device Application

¹ School of Physical Sciences, Indian Association for the Cultivation of Science, Kolkata, India, 700032
² Department of Electronics, Bidhan Chandra College, Rishra, Hooghly, West Bengal, India, 712248

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Published online: 29 May 2026

Abstract

Transparent, pure zinc oxide (ZnO) thin films were deposited on corning glass substrates using the pulsed laser deposition (PLD) technique at room temperature. The as-deposited films were annealed in air at 600 °C for 1 h to enhance their optoelectronic properties, making them suitable for UV photodetector applications. Structural, morphological and optical properties of the as-deposited and annealed ZnO thin films were studied comparatively. The ZnO films exhibited hexagonal wurtzite structure with a preferential orientation along the (002) plane, and their crystallinity improved notably after annealing. The surface roughness slightly increased from 0.77 nm to 1.25 nm after annealing, while the optical bandgap decreased from 3.30 eV to 3.18 eV, attributed to grain growth. The photodetector device was fabricated by depositing Ti/Au electrodes on the annealed ZnO film in a parallel-electrode configuration with an inter-electrode spacing of 30 μm. The device performance was evaluated at room temperature under UV illumination (~365 nm) with an intensity of 70 μW/cm². The as-deposited device showed negligible photo-response under UV illumination. In contrast, the annealed device demonstrated pronounced photoconductive behaviour with superior performance metrics, including a sensitivity of 18.54, a normalized sensitivity of 6.18 × 10⁴/cm², and a high responsivity of 86.04 A/W.