In the present invention, there are provided self-assembled ZnO nanotips grown on relatively low temperatures on various substrates by metalorganic chemical vapor deposition (MOCVD). The ZnO nanotips are made at relatively low temperatures, giving ZnO a unique advantage over other wide bandgap semiconductors such as GaN and SiC. The nanotips have controlled uniform size, distribution and orientation. These ZnO nanotips are of single crystal quality, show n-type conductivity and have good optical properties. Selective growth of ZnO nanotips also has been realized on patterned (100) silicon on r-sapphire (SOS), and amorphous SiO₂ on r-sapphire substrates. Self-assembled ZnO nanotips can also be selectively grown on patterned layers or islands made of a semiconductor, an insulator or a metal deposited on R-plane (01{overscore (1)}2) Al₂O₃ substrates as long as the ZnO grows in a columnar stucture along the c-axis [0001] of ZnO on these materials. Such self-assembled ZnO nanotips and nanotip arrays are promising for applications in field emission displays and electron emission sources, photonic bandgap devices, near-field microscopy, UV optoelectronics, and bio-chemical sensors.