Initial growth behavior and resulting microstructural properties of heteroepitaxial ZnO thin films on sapphire (0001) substrates

摘要

We have investigated the initial growth behavior and resultingmicrostructural properties of heteroepitaxial ZnO thin films prepared by pulsedlaser deposition on sapphire (0001) substrates. High-resolution x-raydiffraction and transmission electron microscopy studies revealed that theinitial growth behavior and the microstructure of the films significantlydepend on the growth parameters. ZnO films grown at 700 oC with 20 mTorr O2partial pressure initiated with a columnar growth mode and contained two kindsof domains. These domains were in-plane orientated eitherZnO[112-0]//Al2O3[101-0] or ZnO[101-0]//Al2O3[101-0], and were surrounded byhighly defective domain boundaries with threading dislocations. The films grownat 800 oC with 1 mTorr O2 showed 2-dimensional layered growth with only onein-plane epitaxial relationship, ZnO[112-0]//Al2O3[101-0]. Most of the defectsin the layered grown films were basal plane stacking faults near the interfacebetween ZnO and the substrate. The formation mechanism of the 30o-twisteddomains with the in-plane orientation of ZnO[101-0]//Al2O3[101-0] is discussed.