Co-doped ZnO dilute magnetic semiconductor thin films by pulsed laser deposition: Excellent transmittance, low resistivity and high mobility

摘要

The 120-nm-thick Co -doped ZnO (CZO) dilute magnetic semiconductor films were grown by pulsed laser deposition at various substrate temperatures (T-s) of 100-700 degrees C. During the film's growth, Ar or O-2 or Ar/O-2-mixed gas atmosphere was used. Hall measurements indicate the CZO films prepared in Ar atmosphere possess the lower resistivity. Then, the microstructural, optical, electrical and magnetic properties of the CZO films deposited in Ar atmosphere were investigated in detail. For the deposition in Ar atmosphere, the lowest resistivity of 4.30 x 10(-2) Omega-cm appeared in the 400 degrees C -grown CZO film since it had more oxygen vacancies with 0 charge state (Vg). As the T-s was raised to 100-300 degrees C, the CZO films had low mobilities of 5.1-10.7 cm(2)/V. This is attributed to the formation of oxygen vacancies with 2+ charge state (V-O(2+)), resulting from the appearance of lattice distortions in these films. A significant relaxation of lattice distortion occurred in the 400 degrees C -grown CZO film, causing the efficient reduction in the amount of V-O(2+). Therefore, the 400 degrees C -grown film had a relatively high mobility of 21.0 cm(2)/V. With increasing the T-s to 400-700 degrees C, the transmittances (@450 nm) of 84.1%-95.8% were obtained in the CZO films. Furthermore, the saturation magnetization values of 100, 400 and 700 degrees C -grown CZO films were 2.74 x 10(-5), 3.37 x 10(-5) and 5.33 x 10(-5) emu, respectively. These results suggest the CZO films are highly potential for spintronic and optoelectronic applications, especially for the 400 degrees C-grown film. (C) 2015 Published by Elsevier B.V.