D.C. Zhang

Electrical and optical properties of ZnO films sequentially implanted with P ions

ZnO thin films deposited on fused silica glass substrates were sequentially implanted with P ions in terms of different energy/fluence combinations, i.e. 150 keV/1.5 × 1015 ions cm−2, 80 keV/5.5 × 1014 ions cm−2 and 35 keV/2.5 × 1014 ions cm−2, or were singly implanted with 150 keV P ions at a fluence of 1.5 × 1015 ions cm−2. X-ray diffraction, photoluminescence, Hall effect and electrical resistivity measurements were performed to characterize the properties of the films. The results show that both the unimplanted and single-P-ion-implanted films exhibit semi-insulating properties, while the sequentially implanted film shows p-type conductivity with a low carrier concentration. After annealing at 500 °C, hole concentration increases distinctly in the sequentially implanted film, and the other films show n-type conductivity. Further increasing annealing temperature to 700 °C, all the films show large resistance. Moreover, structures and optical properties of these films have also been systematically investigated. It seems that P substitutes O (PO) and/or zinc vacancies (VZn) play an important role for p-type conductivity in sequentially implanted films.

Study on Mixing Field of Salt Tolerant Polymer Solution

The salt tolerant polymer (PAM) solution is a kind of viscoelastic fluid. The polymer. whose molecular weight is more than 2.5x107g/mol, is apt to form ultra-molecular structures in solution with pretty high viscoelasticity. These characteristics considerably affect the flow patterns and the mixing process. It is far more difficult to mix viscoelastic fluid homogeneously than Newtonian fluid. Because the molecular diffusion rate of viscoelastic fluid in mixing process is very low, improving the circulating performance of the agitator is the main path to increase the mixing velocity of the viscoelastic fluid. In this study, structure and operation parameters of new type agitator—double helical ribbon screw agitator designed for the salt tolerant polymer are optimized via laboratory experiment. The experiment results show that, compared with the screw propeller, the new type agitator improves circulation of fluid field effectively and increases the homogenized rate. It reduces the mixing time from 4h to 2h. And the viscosity of the polymer solution increases by 10%. However, the energy consumption does not increase.