Band gap engineering in Al, Cu, N and Al/Cu Co-doped ZnO thin films: experimental study and quantum machine learning prediction.

This study investigates RF magnetron sputtered ZnO thin films doped with Al, Cu, N and co-doped with Al/Cu, followed by post deposition annealing at 300-600 °C. Structural and compositional characterization was performed by X ray diffraction (XRD) and energy dispersive spectroscopy (EDS), while surface morphology and roughness were assessed by atomic force microscopy (AFM). Optical band gaps were extracted experimentally from UV-Vis spectra using Tauc analysis and Urbach energy evaluation. Key descriptors, lattice constants, crystallite size, root mean square (RMS) roughness, and Urbach energy were used as input features for a data driven quantum machine learning model. A variational quantum regression (VQR) model trained on these structural and processing descriptors achieved a mean squared error (MSE) of 0.0576 eV in predicting band gap values, accurately capturing trends induced by dopant type and annealing temperature. By combining systematic experimental tuning with quantumn enhanced predictive modeling, the work provides an integrated framework for accelerated band gap engineering of ZnO thin films, with direct implications for optimizing transparent conductive oxides and other optoelectronic materials.