Growth temperature dependent evolutions of microstructural, optical and magnetic properties of Zn0.75Co0.25O films
Qiu Dong-Jiang(邱东江)a)†, Feng Chun-Mu(冯春木)b), Feng Ai-Ming(冯爱明)c), and Wu Hui-Zhen(吴惠桢)a)
aDepartment of Physics, Zhejiang University, Hangzhou 310027, China; bCenter of Analysis & Measurement, Zhejiang University, Hangzhou 310028, China; cCollege of Metrology Engineering, China Institute of Metrology, Hangzhou 310018, China
Abstract Zn0.75Co0.25O films are fabricated via reactive electron beam evaporation. The influence of growth temperature on the microstructural, optical and magnetic properties of Zn0.75Co0.25O films is investigated by using x-ray diffraction, selected area electron diffraction, field emission scanning electron microscope, high resolution transmitting electron microscope, photoluminescence (PL), field dependent and temperature dependent DC magnetization, and x-ray photoelectron spectroscopy (XPS). It is shown that Zn0.75Co0.25OO films grown at low temperatures (250--350℃) are of single-phase wurtzite structure. Films synthesized at 300 or 350℃ reveal room temperature (RT) ferromagnetism (FM), while superparamagnetism for 250℃ fabricated films is found above 56K. PL and XPS investigations show favour towards the perspective that the O-vacancy induced spin-split impurity band mechanism is responsible for the formation of RT FM of Zn0.75Co0.25O film, while the superparamagnetism of 250℃ fabricated film is attributed to the small size effect of nanoparticles in Zn0.75Co0.25O film.
Received: 23 June 2007
Revised: 03 September 2007
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant No 50472058).
Cite this article:
Qiu Dong-Jiang(邱东江), Feng Chun-Mu(冯春木), Feng Ai-Ming(冯爱明), and Wu Hui-Zhen(吴惠桢) Growth temperature dependent evolutions of microstructural, optical and magnetic properties of Zn0.75Co0.25O films 2008 Chin. Phys. B 17 690
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