Low-temperature growth of high-quality ZnO layers by surfactant-mediated molecular-beam epitaxy
ABSTRACT High-quality ZnO layers are grown on Zn-polar ZnO substrates by surfactant-mediated plasma-assisted molecular-beam epitaxy (P-MBE) using atomic hydrogen as a surfactant. Careful investigation with atomic force microscopy (AFM) and reflection high-energy electron diffraction (RHEED) reveals that two-dimensional growth is preserved down to 400 °C by irradiating atomic hydrogen during growth, while the low-temperature limit of two-dimensional growth is 600 °C without atomic hydrogen irradiation. The crystal quality of ZnO layers grown at 400 °C by surfactant-mediated MBE is evaluated to be the same as those grown at 600 °C by conventional MBE in terms of X-ray diffraction and photoluminescence properties.
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ABSTRACT: One-dimensional structure of ZnO nanorod arrays on nanocrystalline TiO2/ITO conductive glass substrates has been fabricated by cathodic reduction electrochemical deposition methods in the three-electrode system, with zinc nitrate aqueous solution as the electrolyte, and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and photoluminescence (PL) spectra. The effects of film substrates, electrolyte concentration, deposition time, and methenamine (HMT) addition on ZnO deposition and its luminescent property were investigated in detail. The results show that, compared with on the ITO glass substrate, ZnO is much easily achieved by electrochemical deposition on the TiO2 nanoparticle thin films. ZnO is hexagonally structured wurtzite with the c-axis preferred growth, and further forms nanorod arrays vertically on the substrates. It is favorable to the growth of ZnO to extend the deposition time, to increase the electrolyte concentration, and to add a certain amount of HMT in the system, consequently improving the crystallinity and orientation of ZnO arrays. It is demonstrated that the obtained ZnO arrays with high crystallinity and good orientation display strong band-edge UV (375 nm) and weak surface-state-related green (520 nm) emission peaks.Science China-Chemistry 01/2010; 53(8):1732-1736. · 1.33 Impact Factor