Thermal stimulated current response in cupric oxide single crystal thin films over a wide temperature range

Cupric oxide single crystal thin films were grown by plasma-assisted molecular beam epitaxy. X-ray diffraction, Raman spectrum and in situ reflection high-energy electron diffraction show that the thin films are 2x2 reconstructed with an in-plane compression and out-of-plane stretching. Thermal stimulated current measurement indicates that the electric polarization response presents in the special 2D cupric oxide single crystal thin film over a wide temperature range from 130 K to near-room temperature. We infer that the abnormal electric response involves the changing of phase transition temperature induced by structure distortion, the spin frustration and magnetic fluctuation effect of short-range magnetic order, or the combined action of both two factors mentioned above. This work suggests a promising clue for finding new room temperature single phase multiferroics or tuning phase transition temperature.