Simultaneous epitaxial growth of Cu2O/ZnO heterostructure thin film on MgO (0 0 1) substrate by dynamic aurora PLD technique for room temperature NO2 gas sensing

High-quality pristine ZnO and (1-x)Cu2O/xZnO heterostructure epitaxial thin films with varying molar ratios (x = 0.1, 0.3, and 0.5) were fabricated using the dynamic aurora pulsed laser deposition method. The structural analysis via 2θ/ω scans and pole figure measurements reveals that pristine ZnO exhibits a single out-of-plane of ZnO (10 1 ¯ 0) ‖ MgO (001) orientation with four in-plane domains and Cu2O exhibits the out-of-plane orientation of Cu2O (011) ‖ MgO (001) with two in-plane domains. In contrast, (1-x)Cu2O/x(ZnO) heterostructure thin films demonstrated distinct crystallographic behaviors: Cu2O grain regions exhibited a single out-of-plane orientation of Cu2O (011) with two in-plane domains, while ZnO grain regions displayed two out-of-plane orientations, such as ZnO (0001) and ZnO (10 1 ¯ 1). The ZnO (0001) oriented grains possessed two in-plane domains, whereas ZnO (10 1 ¯ 1) oriented grains exhibited four in-plane domains. Dynamic force microscopy revealed maze-like grain growth in pristine Cu2O and tiny grain formation in pristine ZnO. In the case of (1-x)Cu2O/x(ZnO) heterostructure thin films, both the maze-like morphology corresponding to cubic Cu2O and the small grains associated with hexagonal ZnO were observed. The as-fabricated epitaxial thin films were employed in the development of a low-cost, energy-efficient, and stable gas sensor for room-temperature NO2 detection.