Synthesis, microstructure, and properties of Ge_1-xCo_x diluted magnetic semiconductor films

¹ College of Materials Science and Technology, Qingdao University of Science and Technology, 53 Zheng-zhou Road, Qingdao, 266042, P.R. China
² National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu-tian Road, Shanghai, 200083, P.R. China
³ Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, 500 Dong-Chuan Road, Shanghai, 200241, P.R. China

Corresponding author: jingchengbin0028@sina.com

Received: 11 January 2010
Revised: 10 June 2010
Accepted: 16 November 2010
Published online: 28 January 2011

Abstract

Co-doped GeO₂ ceramic films were prepared via a liquid phase co-deposition (LPCD) process. The oxide samples were transformed into Ge_1-xCo_x films (x = 0.75, 3.2 and 11.5%) after annealing under hydrogen atmosphere. The crystallinity of Ge_1-xCo_x film decreases with increasing Co content. The Ge_1-xCo_x films are p-type (hole density 10²⁰ ~ 10²¹ cm^-3). The 3.2% film has higher electrical conductivity and hole density compared with the other two samples. The 0.75% film is superparamagnetic at 300 K while the 3.2% and 11.5% films exhibit blocked superparamagnetic behaviors. Hysteresis loops can be observed in the magnetization curves of the 3.2 and 11.5% samples. The observed ferromagnetisms are on only a local (a few nanometers) scale, which most likely arise from different size and chemical distribution in every sample.