Surface morphologies of homoepitaxial ZnO thin films on non-miscut ZnO substrates

ZnO thin films were grown on Zn-polar non-miscut ZnO substrates by plasma-assisted molecular beam epitaxy (PAMBE). With an electrostatic ion trap applied to the oxygen plasma source, the etching effect by plasma was significantly reduced. Atomically flat surfaces with one monolayer step height along the [0 0 0 1] direction were achieved at a low growth temperature of 610 °C. Good surface morphology with root mean square (RMS) roughness as small as 0.16 nm was achieved. High oxygen plasma power and low Zn flux were necessary to achieve a step-flow growth mode with a homogeneous surface morphology. It was found that the growth rate and surface RMS roughness decreased with increased growth temperature.