Surface morphology and crystalline structure of the anneal-treated LPC and HPC substrates: AFM images of LPC (a) and HPC (b) substrates, respectively. The height profiles at the bottom panel show the height variation of the corresponding substrate surface. The height profiles were measured at the regions marked by the dotted lines in corresponding AFM images. XRD results show the crystallinity of the LPC (c) and HPC substrates (d). Only reflex peaks form (111) plane was obviously revealed for both cases.