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Public Seminar of Physics PhD Candidate
posted by Department of Physics for HKU and Public
Event Type: Public Lecture/Forum/Seminar/Workshop/Conference/Symposium
Event Nature: Science & Technology

Event Details

Public Seminar of Physics PhD Candidate
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Comprehensive Defects Study of Sb Doped ZnO Films: the Insights of Donors and Acceptors

Speaker: Ms. Caiqin LUO

Abstract:

To achieve p-type conductivity, Sb doped ZnO has been studied for several decades. But there are still some bottlenecks to obtain stable and reproducible p-type conductivity, which is limiting the widespread use of Sb doped ZnO material. More importantly, the shallow acceptors that donate holes are not determined till now, and it is essential to study what is favorable condition to form the shallow acceptors.

In the present study, Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by the Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ~8x10^20 cm^-3, the as-grown films grown with appropriate oxygen pressure could be n~4×10^20 cm^-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples lead to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.

Several additional vibration modes, located at 235cm^-1, 511 cm^-1, 534 cm^-1, were observed in the Sb-doped ZnO thin films in addition to the host phonons in undoped ZnO sample. The intensity of these additional peaks correlated with the electron concentration/Fermi level. It is plausible that these additional modes are related with the donor defects in Sb doped ZnO samples.


Anyone interested is welcome to attend.

Date/Time15/11/2017 10:00-10:30
VenueRm 518, 5/F, Chong Yuet Ming Physics Building, HKU
LanguageEnglish

Registration Instruction

Registration is not required.

Contact Information

Should you have any enquiries, please feel free to contact Ms. Eva Wong by email at physdept@hku.hk or by phone at 2859 2360 or by fax at 2559 9152.