Structural, optical, and electrical properties of conducting p-type transparent Cu–Cr–O thin films

• Published in: Ceramics international 2016-09, Vol.42 (12), p.13697-13703
• Main Authors: Sun, Chung.-Hsing, Tsai, Du.-Cheng, Chang, Zue.-Chin, Chen, Erh.-Chiang, Shieu, Fuh.-Sheng
• Format: Article
• Language: English
• Subjects: Copper chromium oxide; Delafossite; Optoelectronic properties; Transparent conducting oxide
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2016.05.168

Cu–Cr–O films were prepared by DC magnetron co-sputtering using Cu and Cr targets on quartz substrates. The films were then annealed at temperatures ranging from 400°C to 900°C for 2h under a controlled Ar atmosphere. The as-deposited and 400°C-annealed films were amorphous, semi-transparent, and insulated. After annealing at 500°C, the Cu–Cr–O films contained a mixture of monoclinic CuO and spinel CuCr2O4 phases. Annealing at 600°C led to the formation of delafossite CuCrO2 phases. When the annealing was further increased to temperatures above 700°C, the films exhibited a pure delafossite CuCrO2 phase. The crystallinity and grain size also increased with the annealing temperature. The formation of the delafossite CuCrO2 phase during post-annealing processing was in good agreement with thermodynamics. The optimum conductivity and transparency were achieved for the film annealed at approximately 700°C with a figure of merit of 1.51×10−8Ω−1 (i.e., electrical resistivity of up to 5.13Ω-cm and visible light transmittance of up to 58.3%). The lower formation temperature and superior properties of CuCrO2 found in this study indicated the higher potential of this material for practical applications compared to CuAlO2.