Catalyst free growth of highly crystalline ZnO nanopillars on c-GaN/sapphire templates by chemical vapor deposition technique

Abstract

The catalyst free growth of a large density of highly oriented ZnO nanopillars on c-GaN/sapphire templates has been demonstrated through a chemical vapor deposition route. The pillars are found to have a narrow distribution of height and diameter. It has been observed that the morphology of the growth can be varied from entirely continuous epitaxial layer to oriented nanopillars by controlling the growth temperature and growth duration. These parameters can also be adjusted to control the average diameter and height of these pillars. The authors attribute the formation of nanopillars to a two dimension to three dimension transition of the growth mode as a result of an abrupt change of Zn to oxygen flux ratio upon the closure of oxygen flow into the reactor at the end of the growth.