  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.
