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Etching of high-quality ZnO layers grown by molecular-beam epitaxy was examined by using electron-cyclotron-resonance plasma etching. Etching rates of ZnO layers were larger using CH4 than CF4, and four times more enhanced by using a mixture of the two gases. For a ZnO surface covered with photoresist layers by the plasma-etching procedure, degradation was mostly recovered by thermal annealing in an O2 atmosphere at the proper temperatures. This was found to be effective for the recovery of the layers.

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It has been difficult to obtain single crystalline ZnO films on Si substrates due to the oxidation of Si surface during initial ZnO growth. In this letter, we report the growth of single crystalline ZnO films on Si (111) substrates using a buffer layer of CaF2. The films were grown by radical source molecular beam epitaxy, and revealed by x-ray diffraction to be in the c-axis orientation without in-plane rotational domains. An ultraviolet photoluminescence corresponding to the bandgap energy was dominant for the films even at room temperature. It is indicated by the results that the use of CaF2 buffer layer is promising for the growth of high-quality ZnO (0001) films on Si (111) substrates .