Study On Growth Of ZnO Film With Two-Dimensional Periodic Structure On Si Substate By Molecular Beam Epitaxy

ZnO is considered as one of the most promising materials in short-wavelength optoelectronic applications for its wide bandgap (3.37eV) and large exiton binding energy(60meV). Formed by materials patterned with a periodicity in dielectric constant, photonic crystals (PCs) have photonic bandgap (PBG) characteristics. In a PC the spontaneous emission (SE) can be delicately controlled, which has been achieved in artificial two-dimensional (2D) PCs. The 2D PC slab structures are able to inhibit the SE in the 2D plane, and redistribute the saved energy to the vertical direction where a 2D PBG does not exist. The ability of PCs to control the SE shows promise in fabrication of light emitting devices, such as low threshold lasers.When in a form of PC structure, ZnO material will find more applications in photonic devices. Therefore, many attempts have been made on developing the growth and fabrication techniques to obtain ZnO PCs, such as electrodeposition method and sol-gel process. However, it is still a challenge to prepare ZnO PCs with high crystal qualities.A two-dimensional single crystalline ZnO film with periodic structure (PS) was fabricated on Si (111) substrate by radio-frequency plasma-assisted molecular beam epitaxy. The influence of substrate orientations and growth temperatures was explored for achieving a periodic structure with good qualities. ZnO film on Si (100) substrate was c-axis oriented with the existence of in-plane rotation domains. In the case of Si (111), however, the rotation domains were effectively suppressed, and the morphological periodicity was greatly improved. It was also found that ZnO PS grown on Si (111) substrate at higher temperature has better morphology as well as crystalline quality, which was confirmed by scanning electron microscopy, reflection high-energy electron diffraction, and x-ray diffraction. The results suggest that our growth method is feasible for fabricating ZnO film with PS and our ZnO PS is promising for applications in new photonic devices.