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NSYSU

1. Yang, Kung-Shang. Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique.

Degree: PhD, Physics, 2017, NSYSU

Dilute magnetic semiconductor (DMO) combines spin-polarization and magnetic properties in semiconducting state. One of the compound base on ZnO have potential for application due to it can work at room temperature. Co doped ZnO (CZO) have been reported its ferromagnetic coupling mechanism and including oxygen vacancies can effectively enhance the ferromagnetic coupling. However, itâs rare to mention how the spin-polarized current associate with oxygen vacancies. For this study, we fabricate the CZO films via Zn0.95Co0.05O target and standard sputtering in various mixture atmosphere. (5%, 10%, 20% and 30% H2 partial and Ar atmosphere, and denoted the films as CZO -#%). We use Point-contact Andreev reflection probe various spots of film and obtained conductance(G)-voltage(V) curves and extract the spin polarization values (P) from G-V curves via modified BlonderâTinkhamâKlapwijk (MBTK) model in ballistic and diffusive regime. Considering our present samples accompany relative high resistance which lead to the broadening G-V curves, we include two extra fitting parameters, spreading resistance (Î) and effective temperature (Teff). The simulations indicate the extra parameters are curial for our G-V curves and have better fitting agreement in ballistic limit. The extracted P in ballistic regime are up to 73% and 60% for CZO-30% and CZO-20%, respectively. This result suggests G-V spectra are suppressed as oxygen vacancy concentration increasing and indicates effective percolating paths have been formed as concentration of oxygen vacancies reach to the level as CZO-20% contained. This reinforcement of P is attribute to hopping transport with localized states initiated by part of oxygen vacancies. Advisors/Committee Members: HSIUNG CHOU (committee member), HUA-SHU HSU (chair), CHIEN-CHENG KUO (chair), YUNG-SUNG CHEN (chair), SHIH-CHIEH SUN (chair).

Subjects/Keywords: Oxygen vacancy; Point-contact Andreev reflection; Spin polarization; ZnO; Spin current; dilute Magnetic Oxide; II-VI Compound Semiconductor

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APA (6th Edition):

Yang, K. (2017). Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0102117-141239

Chicago Manual of Style (16th Edition):

Yang, Kung-Shang. “Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique.” 2017. Doctoral Dissertation, NSYSU. Accessed July 22, 2017. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0102117-141239.

MLA Handbook (7th Edition):

Yang, Kung-Shang. “Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique.” 2017. Web. 22 Jul 2017.

Vancouver:

Yang K. Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique. [Internet] [Doctoral dissertation]. NSYSU; 2017. [cited 2017 Jul 22]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0102117-141239.

Council of Science Editors:

Yang K. Probing the spin polarized current in oxygen deficient Co-doped ZnO by Andreev reflection technique. [Doctoral Dissertation]. NSYSU; 2017. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0102117-141239

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