Conductance and phase transition of freestanding ZnO nanocrystals under high pressure

Abstract

The electrical resistances of ZnO powder and nanocrystals produced by a microemulsion method were studied under pressure up to 24 GPa in a diamond anvil cell. The experimental data are different from those previously reported using other techniques. The resistance of ZnO powder rises gradually with increasing pressure until 4.8 GPa and then decreases above 4.8 GPa. The transition point pressure (4.8 GPa) is much smaller than that of 9 GPa for the first order structural transition pressure of bulk ZnO. A similar profile of the electrical resistance versus pressure relationship for ZnO nanocrystals (20 nm) occurs at a higher pressure (8.5 GPa) than that determined for ZnO powder. The cause of these phenomena is discussed.