Mo-Induced Crystallization Control in Si/CuO Heterojunctions Enabling Tunable Electronic Transport and High-Performance Circular Microcavity Antennas

Abstract

Herein, robust crystallization of thermally evaporated CuO on Si is achieved through the application of Mo-nanosheets, with a 20-nm coating being sufficient to induce monoclinic CuO formation and further increases in Mo thickness producing no measurable change in structural order. Mo-induced tuning of band bending and depletion width in SCM-xx devices is demonstrated at 1 MHz. The capacitance-voltage and Mott–Schottky analyses reveal a non-monotonic capacitance response with strong suppression in SCM-20. In addition, the current-voltage characteristics show increasing voltage-dependent asymmetry with Mo nanosheet thickness. Moreover, an engineered capacitively loaded circular microcavity antenna (CL-CMA) based on a vertically integrated Ag/Si/CuO/Mo/Ag heterostructure exhibits excellent resonance at 2.6, 3.07, and 3.20 GHz as a result of the Mo coating on CuO, with return loss exceeding 40 dB at 3.20 GHz and a bandwidth of 2.25 GHz, values that are promising for high-frequency applications. Furthermore, full-wave electromagnetic simulations examining how Mo thickness influences the RF behavior of Si/CuO structures contacted by Ag electrodes, reveal that a 20-nm Mo layer provides the most efficient impedance matching and deepest S₁₁ minimum. The radiation patterns remain largely unchanged across samples. Overall, the features of the devices are promising for advanced electronic applications.