Abstract
This study demonstrates an improvement in the photodetection response of a Cupric Oxide (CuO) thin film through the annealing process. The CuO thin film was deposited on silicon substrate using DC magnetron sputtering system. Annealing of the as-deposited film was carried out in a muffle furnace at 400 and 500 °C for two hours. X-ray diffraction patterns revealed the formation of a single phase CuO film whose crystallinity was improved with increase of the annealing temperature. The field emission scanning electron microscopy indicated a compact and fine granular structure of the as-deposited film whereas the segregation and agglomeration of grains was observed after the film’s annealing. The photodetection performance of CuO film with Al contacts was investigated under the exposure of visible light. The current–voltage graphs of as-deposited and annealed films displayed Schottky contact between the metal and semiconductor, owing to a lower work function of Al than that of the CuO. The photo-to-dark current ratio of the device was significantly enhanced after the film’s annealing. The increase in photocurrent became more pronounced upon increasing the light intensity from 58 to 511 µW/cm2. The maximum current gain and sensitivity values were found to be 66 and 6500% respectively at 10 V bias for the film annealed at 500 °C. The rise and fall time of the Al/CuO/Al photodetector was decreased after the film’s annealing.
Highlights
Copper oxide is a II-VI semiconductor that is often obtained in two phases named as cupric oxide (CuO) and cuprous oxide (Cu2O)
Copper oxide thin films have been synthesized by using various tecqunqies including thermal evaporation, spray pyrolysis, sol gel, chemical vapor deposition (CVD), molecular beam epitaxy, pulsed laser deposition (PLD) and direct current (DC)/RF magnetron sputtering [6,7,8,9,10,11,12]
The as-prepared copper oxide films often contain cuprous oxide phase that can be changed into the cupric oxide at a certain annealing temperature [13,14]
Summary
Copper oxide is a II-VI semiconductor that is often obtained in two phases named as cupric oxide (CuO) and cuprous oxide (Cu2O). The CuO has a lower band gap (1.2 to 2.1 eV) as compared to the cuprous oxide phase (2.1 to 2.7 eV). The as-prepared copper oxide films often contain cuprous oxide phase that can be changed into the cupric oxide at a certain annealing temperature [13,14]. It has been found that the silicon based visible photodetectors are undesirable in flexible and transparent electronic applications due to their bulky and brittle properties [26,27,28]. Copper oxide is a p-type semiconductor that exhibits band gap wavelength corresponding to the visible region It can be effectively used for the photodetector application. Thin film of CuO has been deposited and characterized for the fabrication of a metal-emicondcutor-metal photodetector and its performance has been improved through the annealing process
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