Exploring sulphur substitution in CuCrO2 as p-type transparent conducting materials for optoelectronics applications

• Main Author: Fan, Yang
• Other Authors: Lydia Helena Wong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/176050
• Institution: Nanyang Technological University

Realizing fully transparent electronic devices necessitates the advancement of high- performance p-type transparent conducting oxides. However, attaining this goal poses challenges rooted in the inherent limitations of metal oxides. Their poor p-type conductivity arises from the strong localization of oxygen, giving rise to a significant hole effective mass and, consequently, a reduction in mobility. With its distinctive layered crystal structure, the copper chromium delafossite (CuCrO2) emerges as a promising solution to tackle this challenge, providing a combination of hole mobility and optical transparency. However, it’s performance are still subpar to the n-type counterpart. This project delves into improving CuCrO2 thin films by incorporating sulphur substitution to enhance conductivity. The first strategy is by annealing the CuCrO2 thin film in a sulphur atmosphere led to the formation of conductive CuS, significantly elevating conductivity, resulting in a sheet resistance value of 0.339 KΩ, an optical transparency of 39.3% in the visible spectrum, and a bandgap of 2.97 eV. The second strategy through thiourea addition yielded non-conductive films with bandgaps ranging from 3.14 to 3.19 eV. However, further optimization studies are conducted by varying the annealing temperature at 400°C, 500°C, and 600°C, which shows decrease in conductivity as the temperature increased. Optimal performance was observed at 400°C, exhibiting a sheet resistance of 7.86 MΩ, an optical transparency of 85.4% in the visible spectrum, bandgap of 3.97 eV, yielding FOMH and FOMG values of 2.61 x 10-2 (1/MΩ) and 0.8 (1/MΩ), respectively. This study has shown the effect of sulphur substitution on CuCrO2 thin film through sulphur annealing and thiourea addition.