Enhanced UV Photon-response of Tin Nano Cluster Loaded- laser Irradiated ZnO Thin film detector
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Enhanced UV Photon-response of Tin Nano Cluster Loaded- laser Irradiated ZnO Thin film detector Rashmi Menon, K. Sreenivas and Vinay Gupta Electronic Materials and Devices Laboratory, Department of Physics and Astrophysics University of Delhi, Delhi-110007, India ABSTRACT Zinc Oxide (ZnO), II-VI compound semiconductor, is a promising material for ultraviolet (UV) photon sensor applications due to its attractive properties such as good photoconductivity, ease processing at low temperatures and excellent radiation hardness. The rf magnetron sputtering is a suitable deposition technique due to better control over stoichiometry and deposition of uniform film. Studies have shown that the presence of surface defects in ZnO and subsequently their passivation are crucial for enhanced photo-response characteristics, and to obtain the fast response speed. Worldwide efforts are continuing to develop good quality ZnO thin films with novel design structures for realization of an efficient UV photon sensor. In the present work, UV photon sensor is fabricated using a ZnO thin films deposited by rf magnetron sputtering on the corning glass substrate. Photo-response, (Ion/Ioff) of as-grown ZnO film of thickness 100 nm is found to be 3×103 with response time of 90 ms for UV intensity of 140 µW/cm2 ( λ = 365 nm). With irradiation on ZnO thin film by pulsed Nd:YAG laser (forth harmonics 266 nm), the sensitivity of the UV sensor is found to enhance. The photo-response increases after laser irradiation to 4x104 with a fast response speed of 35 ms and attributed to the change in surface states and the native defects in the ZnO thin film. Further, enhancement in the ultraviolet (UV) photo-response (8×104) of detector was observed after integrating the nano-scale islands of Sn metal on the surface of laser irradiated ZnO thin film. INTRODUCTION Zinc oxide (ZnO) is a wide band gap (3.4 eV) semiconductor material attracting attention for application in varistors, high power electronics, surface acoustic wave devices, piezoelectric transducers, gas-sensors, photo-detectors and solar cells [1-9]. ZnO is a promising material, relative to other wide band gap semiconductors, for ultraviolet (UV) photon detector applications due to its attractive properties such as good photoconductivity, easy processing at low temperatures, excellent radiation hardness and the possibility of integrating with existing integrated microelectronics. Sensing of ultra-violet (UV) radiation has potential applications in civil and military areas, high energy flame detection, missile warning, medical sciences, optical communication and astronomical studies. During the last few decades, there has been considerable interest in imaging systems that can record very low light levels in the ultraviolet range. Studies are continuing towards the improvement of the photo-response of ZnO photon sensor. The presence of surface defects in ZnO and subsequently their passivation has been identified as the crucial parameter for the photoresponse characteristics, and determine the respons
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