Fabrication of homoepitaxial ZnO films by low-temperature liquid-phase epitaxy

Highly crystalline undoped ZnO films were grown by liquid-phase epitaxy on (0 0 0 1) ZnO substrates with a misorientation of 0. 5 degrees toward (10 <(1over bar > 0). ZnO was continuously formed by the chemical reaction of ZnCl(2)and K2CO3 Films of thickness <= 4 mu m were grown in the temperature range 630-640 degrees C, resulting in step-flow growth as observed by differential interference microscopy and scanning electron microscopy. An interstep distance of 2 +/- 0.5 mu m and step height 0.5 nm corresponding to one monolayer was observed by atomic force microscopy. Measurement of the (0 0 0 2) reflection of the X-ray rocking curve revealed the high quality of the ZnO films with a full-width half-maximum of 31 arcsec. The photoluminescence spectrum obtained at 4K is dominated by emission from the band edge at 3.36 eV with a sharp splitting of the free exciton emission. A damaged surface layer in the ZnO substrate due to machining was revealed by radioluminescence at 80 K. (c) 2005 Elsevier B.V. All rights reserved.