Microstructures, surface bonding states and room temperature ferromagnetisms of Zn0.95Co0.05O thin films doped with copper
✍ Scribed by Zuci Quan; Dan Li; Bobby Sebo; Wei Liu; Shishang Guo; Sheng Xu; Huiming Huang; Guojia Fang; Meiya Li; Xingzhong Zhao
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 686 KB
- Volume
- 256
- Category
- Article
- ISSN
- 0169-4332
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✦ Synopsis
ZnO-related DMS was sparked by a theoretical prediction raised by Dietl et al.,. Subsequently, several research groups reported the RTFMs of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sn-doped ZnO films and (P, Mn), (Al, Mn), (Mn, Cu), (Mn, Sn), (Fe, Cu), (Cu, Ga), (Li, Co), (N, Co), (Al, Co), (Fe, Co) and (Co, Cu)-codoped ZnO films [3][4][5][6][7][8]10,11]. Among these doped ZnO films, Zn 0.95 Co 0.05 O films are particularly intriguing because Co provides an opportunity to realize RTFM in ZnO via high-spin Co 2+ (3d 7 4s 0 , 4 F 9/2 , S = 3/2) and/or Co 3+ (3d 6 4s 0 , 5 D 4 , S = 2) for which the net superexchange coupling is ferromagnetic at room temperature, based on its high T C of up to 427 8C, the reversible cycling of ferromagnetic ordering and excellent ferromagnetic transport properties [3,4,6,8,12]. Nevertheless, Sluiter et al. reported that except the ferromagnetic exchange interaction between substituted Co 2+ for Zn 2+ in the ZnO matrix, there exists an antiferromagnetic exchange interaction between some of neighbouring Co 2+ cations, and the RTFMs of Co-doped ZnO films depend strongly on dopants, experimental methods and conditions used in the preparation processes [4,7]. Meanwhile, issues of the ferromagnetisms still remain controversial. Additionally, p-type Cu-doped ZnO films are also attractive because the Cu-doped ZnO matrix possesses a ferromagnetic ground state deduced from first principles, and Cu cations have no clustering tendency to overcome the problem of magnetic precipitates in the 13,14]. Therefore, it is conceivable that Co and Cu are promising candidates as codopants for ZnO films based on matching ionic radii [4]. According to first principles calculations based upon the density functional theory with Perdew-Burke-Enzerh generalized gradient approximation, the electrons with Applied Surface Science 256 (2010) 3669-3675