ZnO growth by chemical vapour transport

With the intention of achieving growth at moderate temperature, chemical vapour transport using chlorine and carbon as transporting agents is studied for the growth of ZnO crystals. A chemical vapour transport process in which carbon is the essential transport agent is suggested. Crystals of size 1 cm(3) are obtained after 40 days of using a source temperature of 1000 degrees C and a source temperature-growth temperature difference Delta T of similar to 30 degrees C. Rocking-curve FWHM in the 30 arcsec range are measured and well-resolved pseudo Kikuchi lines observed on (0 0 0 1) planes by electron scanning microscopy. The residual concentration of chlorine atoms in the crystals is estimated from XPS measurements to be about 0.05%. The electron concentration of the crystals at room temperature reaches values as high as 3 x 10(19) cm(-3). The ionisation energy of the residual donor (chlorine?) in ZnO is found close to 23 meV. (C) 1999 Elsevier Science B.V. All rights reserved.