Ultraviolet and Deep-Ultraviolet Emissions from c-Mg_xZn_1-xO/MgO Ultrathin Multilayer Heterostructures

Cubic phase Mg_xZn_1-xO/MgO multilayer heterostructures (c-Mg_xZn_1-xO/MgO MHs) are grown on Si(100) and quartz substrates by reactive electron beam evaporation at low temperature (250°C). Cross-sectional morphology observations by field-emission scanning electron microscopy show the legible interfaces of c-Mg_xZn_1-xO/MgO MHs. X-ray diffraction demonstrates that c-Mg_xZn_1-xO/MgO MHs are of highly (100)-oriented. Optical transmission investigations of c-Mg_xZn_1-xO/MgO MHs on quartz substrates reveal the coexistence of the two phases, c-Mg_xZn_1-xO and MgO. Photoluminescence examination indicates the emergence of deep-ultraviolet emission centred at about 290nm along with the blue shift of the ultraviolet emission from 405nm to 396nm when the nominal thickness of c-Mg_xZn_1-xO well layers of MHs is diminished to 3nm, which is probably originated from quantum confinement effect.