Low-temperature atomic layer deposition of ZnO thin films: Control of crystallinity and orientation

Low-temperature atomic layer deposition (ALD) processes are intensely looked for to extend the usability of the technique to applications where sensitive substrates such as polymers or biological materials need to be coated by high-quality thin films. A preferred film orientation, on the other hand, is often required to enhance the desired film properties. Here we demonstrate that smooth, crystalline ZnO thin films can be deposited from diethylzinc and water by ALD even at room temperature. The depositions were carried out on Si(100) substrates in the temperature range from 23 to 140 degrees C. Highly c-axis-oriented films were realized at temperatures below similar to 80 degrees C. The film crystallinity could be further enhanced by post-deposition annealing under O-2 or N-2 atmosphere at 400-600 degrees C while keeping the original film orientation intact. (C) 2011 Elsevier B.V. All rights reserved.