The oriented growth of ZnO films on NaCl substrates by pulsed laser ablation

The structure of ZnO thin films grown by 193-nm pulsed laser ablation (PLA) of a ZnO target in a low background pressure of O2 on (001) NaCl substrates was examined using selected-area electron diffraction (SAED) in a transmission electron microscope (TEM). Samples were grown at different substrate temperatures in the range 20–300 °C. All samples were polycrystalline with the wurtzite crystal structure. Samples deposited at 20 °C had a polar (0002) texture. At higher substrate temperatures oriented growth was observed with diffraction patterns showing four-fold symmetry. These patterns can be explained by a combination of - and -oriented grains, the alignment of which can be rationalised in terms of epitaxy with the surface of the NaCl substrate.