Although metal/semiconductor and oxide/semiconductor junctions have long been studied in the areas of microelectronics, new phenomena and interests arise from time to time. In particular, in the realm of nanotechnology where materials are shrunk at a length scale of nanometers, the role of heterojunctions in controlling the overall characteristics of the system will become more and more important. In this paper, we will show our recent results on the light emission and charge transport properties of metal/ZnO and oxide/ZnO system at different dimensionalities. On one hand, it is found that by capping metal on ZnO, it is possible to excite the surface plasmon polaritorn at the metal/ZnO interface and resonantly couple it with the spontaneous recombination of ZnO. This results in a significant enhancement of emission efficiency of ZnO. On the other hand, providing an oxidic overlayer (AlOx) is present on ZnO, a focused electron beam can be used to locally modify optical and electrical properties of ZnO. Under electron bombardment, we find the emission profile of ZnO gradually changes from green-yellow emitting into ultra-violet emitting while the conductivity decreases by more than two orders of magnitude at the same time. Well-defined sub-micron patterns with tunable optical and electrical properties can be fabricated on 2-D ZnO films and 1-D nanoribbons by carefully controlling the dose and energy density of the electron beam. Since ZnO is a versatile material, we believe our studies will shed light on the further use of ZnO in frontier technologies such as gas sensing, display technology, catalysis, spintronics, etc.