INFORMATION ON NEW CONCLUSIONS OF DOCTORAL THESIS
Name of thesis: Synthesis and investigation on ZnS/ZnO phase transition in one-dimensional ZnS
Specialization: Optic, Optoelectronic and Photonic Material
Code No: 62440127
Name of PhD. Student: Do QuangTrung
1. Assoc. Prof. Dr. Pham Thanh Huy
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
Assoc. Prof. Dr. Pham Thanh Huy
Ha Noi, March 03rd, 2014
Do Quang Trung