We report a facile process to fabricate cuprous thin films by thermal oxidation of copper substrates. Structure and phase identification were studied by X-ray diffraction measurement and Raman spectroscopy. Scanning electron microscopy was utilized to study surface morphology of the as-fabricated thin films and optical properties of the samples were investigated by diffused reflectance spectroscopy. | VNU Journal of Science Mathematics Physics Vol. 36 No. 2 2020 31-36 Original Article Effect of Annealing Temperature on Cu2O Thin Films Prepared by Thermal Oxidation Method Tran Thi Ha1 2 Nguyen Thi Huyen Trang2 Bach Thanh Cong2 Nguyen Thi Dieu Thu1 Nguyen Thanh Binh2 NguyenViet Tuyen2 Pham Nguyen Hai2 1 Faculty of Basic Science University of Mining and Geology Duc Thang Tu Liem Hanoi Vietnam 2 Faculty of Physics VNU University of Science Vietnam National University Hanoi 334 Nguyen Trai Thanh Xuan Hanoi Received 29 October 2019 Revised 27 November 2019 Accepted 28 November 2019 Abstract We report a facile process to fabricate cuprous thin films by thermal oxidation of copper substrates. Structure and phase identification were studied by X-ray diffraction measurement and Raman spectroscopy. Scanning electron microscopy was utilized to study surface morphology of the as-fabricated thin films and optical properties of the samples were investigated by diffused reflectance spectroscopy. The study shows that cuprous thin films could be obtained by controlling annealing temperature in the region of 200-300 oC. Keywords Copper oxide thin films thermal oxidation Raman. 1. Introduction Cuprous oxide Cu2O is a semiconductor with bandgap of around 1-2 eV 1 which finds many applications in fields of sensor photocatalyst and especially photovotaics 2 8 thanks to their interesting properties such as earth abundant composition environment friendly high absorption coefficient in visible region p type conduction. Even though the efficiencies of solar cell based on copper oxide is often quite low of around 1 to 2 the ratio of efficiency to cost of Cu2O is still very competitive to other materials. Hence preparation of Cu2O thin film is an interesting topic for study in view of both fundamental and application. ____ Corresponding author. Email address phamnguyenhai@ https 2588-1124 31 32 . Ha et al. VNU Journal of Science Mathematics .