Tuning The Optoelectronic Properties Of One Dimensionalâ…¡-â…¥ Semiconductor Nanostructures For Device Aplications

One dimensional semiconductor nanostructures have attracted extensive attention, due to their excellent and unique optical, electrical and mechanical properties compared to their thin films or bulk counterparts. O ne dimensional II-VI semiconductor(such as ZnO, ZnSe, CdS), with a wide and direct band gap, has been considered as a promising material for constructing high-performance nano-electronic and nano-optoelectronic devices. Rational modulating the conductive type and conductive ability of semiconductor is the precondition of their applications in optoelectronic devices. However, it remains a challenge to tuning the electrical properties of II-VI semiconductors by means of traditional bulk doping method, due to the strong self-complementary effect, which blocks the applications of II-VI semiconductor nanostructures in photoelectric devices. Above all, it is very necessary to realize controllable preparation of II-VI semiconductor nanostructures and effective control their photoelectric properties, which is of great significance to their application in the field of optoelectronic devices.In this thesis, we have successfully prepared one dimensional II-VI semiconductor nanostructures with high quality and realized effective control of their conductive ability or conductive type by doping. Combined with micro-nano processing technology, high-performance optoelectronic device based on one dimensional II-VI semiconductor nanostructures were fabricated and their photoelectric properties were studied systematically. The thesis includes the following sections:(1) One dimensional II-VI semiconductor nanostructures with high quality have been prepared by chemical vapor deposition(CVD) method. The conduction type of ZnSe nanoribbons is successfully transformed from n-type to p-type by the means of surface charge transfer doping with MoO3 nanodots. The doping effect is confirmed by single ZnSe nanoribbon bottom- gate field effect transistor with high hole mobility of 48.17 cm2V-1s-1 and hole concentration of 1.26 1019 cm-3. The mechanism of surface charge transfer doping of ZnSe nanoribbons by the adsorption of MoO3 nanodots was studied. Due to the charge transfer between ZnSe nanoribbon and MoO 3 nanodots, the conductivity of ZnSe nanoribbon increases with the concentrations of MoO3 solution. The conductivity of the doped ZnSe nanoribbon increases drastically by more than 7 orders of magnitude compared to the intrinsic ZnSe nanoribbon. Via the surface charge transfer doping method, single ZnSe nanoribbons homojunction photovoltaic device and p-ZnSe/n-Si heterojunction device are fabricated and their photoelectric performance are studied. The photovoltaic devices possess a high photoelectric conversion efficiency of 1.84%, resulting from the unique doping method and high quality homojunction configuration. Because of the heterostructure structure, p-ZnSe/n-Si heterojunction devices show clear light response not only to white light, but also to ultraviolet light and deep ultraviolet light. Besides, we also try to modulate the conductive type and conductive ability of other II-VI semiconductor nanostructures(such as CdSe and ZnTe) by means of surface charge transfer doping.(2) O ne dimensional CdS:Mo-CdMoO4 core-shell nanoribbons with high quality have been prepared by thermal evaporated doping process. In the evaporation process, not only doping effect is achieved, but also an amorphous shell and a polycrystalline CdMoO4 shell is formed on the surface of CdS nanoribbons. Due to the unique structure of CdS:Mo-CdMoO4 core-shell nanoribbon, we successfully constructed high-performance nonvolatile memory with back gate field effect transistor configuration based on single nanoribbon by one-step method. Under the premise of achieving high device performance compared with other similar devices, our device fabrication strategy have advantages of simple construction process and easy operation.