The Study Of Transient Surface Photovoltic And Gas Sensing Properties On ZnSe Nanocrystals

The study on mechanism of action between Zn Se surface adsorbed by oxygen, carbon monoxide and carbon dioxidemolecules is significant for improving the semiconductor’s function in the field of gas sensitive material and catalysis. Both adsorption behaviors of oxygen, carbon monoxide and carbon dioxidemolecules on nonpolar(110) face of Zn Se and process of catalytic oxidation CO on the lattice plane adsorbed oxygen were simulated by periodic slab model based on density functional theory.The photoexcited carriers’ transport behaviors of Zn Se QDs with core-shell structure are prepared and studied because of its unique photoelectronic characteristics. A series of good surface photovoltaic properties of the self-assembled Zn Se/Zn S/L-Cys core-shell QDs prepared were probed via the EFISPV and the TPV technology, supplemented by FT-IR spectrum, laser Raman, and UV-VIS absorption and PL spectrum.The results showed that the surface energy of Zn Se(110) face is the smallest among all the three concerned surfaces which indicate that Zn Se(110) is the most stable surface. Oxygen, carbon monoxide and carbon dioxidemoleculescan interact with the surface by chemical adsorption, the adsorption energy are 0.455, 0.296 and 0.326 e V, respectively.O atom and C atom play an important roll on the adsorpting of above gases. The catalytic oxidation reaction of CO is more likely to happen when oxygen adsorption prior to carbon monoxide on the surface. Oxygen molecules were preferably adsorbed on Se vacancies of the(110) face, and the produced excited O22- ions can greatly increase the oxidizability of the face, resulting in an obvious influence of the catalytic oxidation reaction of CO on the Zn Se(110) surface.The Zn Se QDs with p-type SPV characteristic showed wider and stronger SPV response at whole illumination range of UV to NIR than other core/shell QDs in same group. The dependency relationship between the SPV phase value and the external bias was revealed by the SPV phase spectrum of the QDs. The wide transient PV response region of 3.3×10-8 to 2×10-3 s was closely related to the elongated diffusion distance of photoexcited FCCs in the interface SCR of the QDs. The strong SPV response corresponding to the core-Zn Se mainly benefited from obvious quantum tunnel effect in the QDs..