Microstructure study of ZnO thin films on Si substrate grown by MOCVD

The microstructure of zinc oxide thin films on silicon substrates grown by metalorganic chemical vapour deposition (MOCVD) was characterized. The cross-sectional bright-field transmission electron microscopy (TEM) image showed that small ZnO columnar grains were embedded into large columnar grains, and the selected-area electron diffraction pattern showed that the ZnO/Si thin films were nearly c-axis oriented. The deviation angle along the ZnO ( 0 0 0 1) direction with respect to the growth direction of Si ( 1 0 0) was no more than 5 degrees. The [0001]-tilt grain boundaries in ZnO/Si thin films were investigated symmetrically by plan-view high resolution TEM. The boundaries can be classified into three types: low-angle boundaries described as an irregular array of edge dislocations, boundaries of near 30 degrees angle with (1 0 (1) over bar 0) facet structures and large-angle boundaries with symmetric structure which could be explained by a low Sigma coincident site lattice structure mode. The research was useful to us for finding optimized growth conditions to improve ZnO/Si thin film quality.