Tài liệu Tóm tắt luận án nghiên cứu chế tạo và khảo sát quá trình chuyển pha znszno của các cấu trúc nano zns một chiều (tiếng anh)

INFORMATION ON NEW CONCLUSIONS OF DOCTORAL THESIS Name of thesis: Synthesis and investigation on ZnS/ZnO phase transition in one-dimensional ZnS nanostructures Specialization: Optic, Optoelectronic and Photonic Material Code No: 62440127 Name of PhD. Student: Do QuangTrung Advisors: 1. Assoc. Prof. Dr. Pham Thanh Huy 2. Dr. Tran Ngoc Khiem Training Institution: Hanoi University of Science and Technology Summary of new contributions of the Thesis 1. We have successfully synthesized the various 1D ZnS nanostructures including micro/nano-rods, nanobelts, and nanowires by thermal evaporation method. ZnS nanorods and nanobelts with high crystallinity were achieved. Strong NBE emission (~340 nm) at room temperature was observed. 2. ZnS nanowires was completely oxidized into ZnO nanowires at the temperatures in the range of 700-800 C under air ambience. The samples oxidized at 500 C for 1hour under air showed a heterostructure ZnS/ZnO. This artificial material is characterized by a emission band at ~355 nm, between NBE emissions of ZnS and ZnO (340-380 nm). 3. The ZnS nanobelts showed a strong NBE emission peak at ~340 nm at room temperature under the excitation of the pulsed laser (Nd: YAG) with wavelength of 266 nm. Laser power dependence of the photoluminescence from the ZnS nanobelts showed the spontaneous laser emissions at power density of ~476.2 mW/cm2 with peak emission wavelengths at 334, 330, and 328 nm; and the full width at half maximum (FWHM) of only ~0.5-0.7 nm. 4. The phase transition of ZnS into ZnO microrods by oxidizing ZnS in oxygen ambient was studied. The results confirm that ZnS/ZnO heterostructure with emission characteristics of both ZnS and ZnO can be obtained by controlling oxidation conditions. The ZnO microrods obtained by completely oxidizing ZnS show high crystallinity and their shapes are similar to ZnS one. NBE emissions of ZnS and ZnO in the ZnS/ZnO heterostructure were could be controlled by the change of oxidation temperature. The ZnO microrods obtained by oxidizing ZnS show high crystallinity and laser emission at room temperature. It is also demonstrated that Sdoped ZnO microrods with S concentration of about 1 at% (obtained by oxidizing ZnS microrods), which show strong and very broad band visible emission (from 400-700 nm), could be an excellent material for application in fabricating white light emitting diodes. 5. By systematic and comparative studying of the oxidation process of the ZnS microrod and nanowires at different temperatures, a comprehensive interpretation for the origin of the well-known green emission from 1D ZnS has been proposed as due to the formation of a Zn-O-S ternary phase that formed at the imperfect ZnS/ZnO interface in the 1D ZnS nanostructures. 6. Mn-doped 1D ZnS structures were successful fabricated by using two different approaches, namely, Mn post diffusion, and in-situ doping during growth, and by both vapor-solid-liquid (VLS) and vapor-solid growth mechanisms. Advisors (Signature) Assoc. Prof. Dr. Pham Thanh Huy Ha Noi, March 03rd, 2014 PhD. Student (Signature) Do Quang Trung