Luminescence and structure of ZnO grown by physical vapor deposition

Nanostructured ZnO was deposited on different substrates (Si, SiO ₂, and Au/SiO₂) by an enhanced physical vapor deposition technique that presents excellent luminescent properties. This technique consists in a horizontal quartz tube reactor that uses ultra-high purity Zn and UHP oxygen as precursors. The morphology and structure of ZnO grown in this work were studied by electron microscopy and X-ray diffraction. The XRD patterns revealed the highly crystalline phase of wurtzite polycrystalline structure, with a preferred (1011) growth direction. Room temperature cathodoluminescence studies revealed two features in the luminescence properties of the ZnO obtained by this technique, first a high-intensity narrow peak centered at 390 nm (3.2 eV) corresponding to a near band-to-band emission, and secondly, a broad peak centered around 517 nm (2.4 eV), the typical green-yellow luminescence, related to an unintentionally doped ZnO.