Control of a- and c-plane preferential orientations of ZnO thin films

초록

We report orientation-controllable growth of ZnO thin films and their orientation-dependent electrical characteristics. ZnO thin films were deposited on single-crystalline (1 0 0) LaAlO3 and (1 0 0) SrTiO3 substrates using pulsed laser deposition (PLD) at different substrate temperatures (400-800 degrees C). It was found that the orientation of ZnO films could be controlled by using different substrates of single-crystalline (1 0 0) LaAlO3 and (1 0 0) SrTiO3. The a-plane (1 1 2(-) 0) and c-plane (0 0 0 2) oriented ZnO films are formed on LaAlO3 and SrTiO3, respectively. In both cases, the degree orientation increased with increasing deposition temperature T-s. Both the surface free energy and the degree of lattice mismatch are ascribed to play an important role for the orientation-controllable growth. Further characterization show that the grain size of the films with both orientations increases for a substrate temperature increase (i.e. from T-s = 400 degrees C to T-s = 800 degrees C), whereas the electrical properties of ZnO thin films depend upon their crystalline orientation, showing lower electrical resistivity values for a-plane oriented ZnO films. (C) 2008 Elsevier B.V. All rights reserved.

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