Preparation And Characterization Of ZnO Thin Films And ZnO/MgO Multi-quantum Wells

ZnO is a new wide band-gap semiconductor with a hexagonal wurtzite structure. Its band gap energy is 3.37eV at 300K with a large exciton binding energy (60meV), which makes it the promising materials for UV light-emitting devices. ZnO films also have some other potential applications such as surface acoustic wave device, transparent conductors, UV photodetectors, piezoelectric devices and gas sensors, etc. The renewed interest of ZnO film is fueled since room temperature lasing was reported by Tang et al.In this thesis, we deposite ZnO thin films and ZnO multiple quantum wells by radio-frequency magnetron sputtering technique. The results are summarized as follow:Ⅰ. ZnO/MgO multi-quantum wells with modulation structure are grown on oxidated Al2O3(0001) substrates using radio-frequency reactive magnetron sputtering method. The XRD scan and phi-scan results show the films are highly (001) textured and have epitaxial relationship with the substrates. The width of quantum well is determined to be between 8.38nm and 21.78nm by XRR and EPMA. The AFM results show that the RMS roughness of the MQWs increases from 6.4nm to 21.2nm with the decrease of period thickness. Low temperature PL spectrum shows the peak can be assigned to the radiative recombination of bound excitons, and the activation energy is estimated to be about 30meV.Ⅱ. ZnO thin films are grown on Si(111) and YSZ(111) substrates by radio-frequency magnetron sputtering method. The XRD scan results reveal that ZnO/YSZ has better crystalline quality than ZnO/Si(111), the full-width-at-half-maximum(FWHM) of ZnO(002) peak for ZnO/YSZ are 0.16°(forθ-2θpatterns) and 0.58°(for Rocking Curve patterns). XRD phi scan results of ZnO thin film deposited on YSZ(111) show ZnO film has epitaxial relationship with the YSZ substrates. The AFM results show greater grain size and larger surface roughness for ZnO/YSZ films. The room temperature photoluminescence spectrums give UV peak at 378nm for both two samples, and the intensity for ZnO/YSZ doesn't show enhancement in comparison to ZnO/Si.