Intrinsic room temperature ferromagnetism in boron-doped ZnO

Abstract

We report room temperature ferromagnetism in boron-doped ZnO both experimentally and theoretically. The single phase Zn 1-x B x O films deposited under high oxygen pressure by pulsed-laser deposition show ferromagnetic behavior at room temperature. The saturation magnetization increases monotonously from 0 to 1.5 emu/cm 3 with the increasing of B componentx from 0 to 6.8%. The first-principles calculations based on density functional theory demonstrate that the ferromagnetism in B-doped ZnO originates from the induced magnetic moments of oxygen atoms in the nearest neighbor sites to the B-Zn vacancy pair. The calculated total magnetic moment increasing tendency with B component is well consistent with experiments. * To whom correspondence should be addressed. Email: yjiang@ustb.edu.cn 1 Dilute magnetic semiconductors (DMS) are promising candidates for spintronics devices due to their peculiar magnetic and semiconductor properties. In recent years, researchers have made great efforts to design and fabricate DMS, especially those with Curie temperature (T C ) above room temperature. Among all DMS candidates, ZnO has attracted wide interest, since it is predicted to be an ideal room-temperature DMS by Dietl et al. [1]. The magnetic moments of oxygen atoms around Zn vacancy are confirmed to be an origin of the ferromagnetic (FM) property in pure ZnO system [ 2 , 3 ]. However, the density of Zn vacancy is sensitive to experimental conditions and difficult to be controlled. Transition metal (TM) doping is a traditional method to obtain room temperature ferromagnetism in ZnO system [4,5,6,7,8,9,10,11,12]. However, the inconsistent experimental results raise a new problem of explaining the mechanism of ferromagnetism in TM-doped ZnO. Moreover, it is difficult to exclude the possibility that the ferromagnetism might be brought by a secondary phase of TM oxides or TM dopant clusters [13,14,15]. Consequently, many researchers turned their attention to non-TM doped ZnO and tried to provide undisputed intrinsic DMS. Pan et al. [16] theoretically predicted and experimentally realized room temperature ferromagnetism in carbon-doped ZnO films. A further work by Peng et al. [17] demonstrated the hole-induced mechanism in p-group element-doped FM ZnO system, which opens a new way for studying non-TM doped ZnO DMS.In this letter, we report our experimental study on 2p-group element B-doped ZnO system. First-principles calculations based on the density functional theory justify the intrinsic ferromagnetism in the system is induced by oxygen atoms in the nearest neighbor sites to the B-Zn vacancy pair, which is quite different from the origin of the ferromagnetism in carbon-doped ZnO.All the B-doped ZnO thin films were grown by pulsed-laser deposition (PLD) using a KrF 2 excimer laser operating at 300 mJ/pluse and 10 Hz. The targets were prepared by sintering mixed ZnO (99.99%) The most possible site for B should be tetrahedral or octahedral interstice in ZnO, due to the small radius of B. According to our calculation,...

Optical properties and electrical resistivity of boron-doped ZnO thin films grown by sol–gel dip-coating method

“…Furthermore, doping can be used to effectively tune the width of the band gap of ZnO, which will in turn affect the optical properties of ZnO [16][17][18]. Among the various kinds of doped ZnO, B-doped ZnO (BZO) has recently been extensively investigated because of its utilitarian application as a transparent conductive oxide [19] and its ferromagnetic properties [20].…”

Dependence of ferromagnetic properties on growth oxygen partial pressure in boron-doped ZnO thin films

“…In sharp contrast with this, Yi et al [15] reported that the p-type DMSs showed an enhanced magnetic moment when nitrogen was introduced to the C-doped ZnO films. Our earlier theoretical and experimental studies have shown that the nonmagnetic ion B-doped ZnO films have RTFM which appears to be related to the B dopants and the high growth oxygen partial pressure [16]. In this paper, we report our further investigation on the effect of carries type on the magnetic properties of B-doped ZnO films.…”

INTRINSIC ROOM TEMPERATURE FERROMAGNETISM OF SILICON-DOPED ZnO THIN FILMS

“…Recently, FM has been observed in nonmagnetic element doped ZnO films, such as carbon, lithium or boron doped ZnO thin films. [23][24][25] Therefore, "d 0 -element" doping opens a new method to find ZnO DMS. As a tetravalent element, Si is considered to be a suitable d 0 dopant for inducing FM to ZnO system.…”