Epitaxial growth of ferromagnetic Co:TiO2 thin films by co-sputtering

Han, Gang; Wu, Yihong; Tay, M.; Li, K.B.; Zhong, Guo; Chong, Tow Chong

doi:10.1016/s0304-8853(03)00492-x

Cited by 17 publications

(7 citation statements)

References 15 publications

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“…Medvedkin et al [26] [94]. In a very recent report Han et al [90] report ferromagnetism in crystalline Co-TiO 2 grown by co-sputtering, Tc being higher than 400 K. Despite all this work, the key question still remains to be answered is that if Co is indeed substitutional or forms clusters to form ferromagnetic regions within the films.…”

Section: (Cdmn)gepmentioning

confidence: 99%

Novel room temperature ferromagnetic semiconductors

Gupta

2004

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In today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will be higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO,and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in ■ ZnO:Mn (paper in Nature Materials, Oct issue, 2003) ■ ZnO doped with Cu (containing no magnetic elements in it!) ■ GaP doped with Cu (again containing no magnetic elements in it!) ■ Enhancement of Magnetization by Cu co-doping in ZnO:Mn ■ CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 µm thick transparent pulsed laser deposited films of the Mn (< 4 at.%) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous distribution of Mn substituting for Zn a 2 + state in the ZnO lattice. Ferromagnetic Resonance (FMR) technique is used to confirm the existence of ferromagnetic ordering at temperatures as high as 425K. The ab initio calculations were found to be consistent with the observation of ferromagnetism arising from fully polarized Mn 2 + state. The key to observed room temperature ferromagnetism in this system is the low temperature processing, which prevents formation of clusters, secondary phases and the host ZnO from becoming n-type. The electronic structure of the same Mn doped ZnO thin films studied using XAS, XES and RIXS. revealed a strong hybridization between Mn 3d and O 2p states, which is an important characterstic of a Dilute magnetic Semiconductor (DMS). It is shown that the various processing conditions like sintering temperature, dopant concentration and the properties of precursors used for making of DMS have a great influence on the final properties. Use of various experimental techniques to verify the physical properties, and to understand the mechanism involved to give rise to ferromagnetism ...

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Section: (Cdmn)gepmentioning

confidence: 99%

Novel room temperature ferromagnetic semiconductors

Gupta

2004

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“…DMSs exploit the spin and the charge of the carries, which raises the possibility of spintronic applications [2,3]. In recent years, it has been reported that Co-doped TiO 2 , for both anatase and rutile phases, can exhibit room-temperature ferromagnetism (RTFM) [4][5][6][7][8][9][10][11][12]. This has attracted much attention to the development of oxide-based DMSs.…”

Section: Introductionmentioning

confidence: 99%

“…This has attracted much attention to the development of oxide-based DMSs. RTFM was reported by different groups in Co-doped TiO 2 films grown by pulsed laser deposition, molecular beam epitaxy and cosputtering [4][5][6][7]. However, the mechanism on the origin of RTFM in the Co-doped TiO 2 has not been definitely confirmed.…”

Section: Introductionmentioning

confidence: 99%

The influence of hydrogen annealing on magnetism of Co-doped TiO2 films prepared by sol–gel method

Liu

Kang

Wang

et al. 2007

Journal of Magnetism and Magnetic Materials

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“…They are wide band gap semiconductors. Anatase TiO 2 has high mobility of n-type charge carriers [89,90]. [94].…”

Section: Tio 2 Based Dmsmentioning

confidence: 99%

“…[94]. In a very recent report Han et al [90] report ferromagnetism in crystalline Co-TiO 2 grown by co-sputtering, Tc being higher than 400 K. Despite all this work, the key question still remains to be answered is that if Co is indeed substitutional or forms clusters to form ferromagnetic regions within the films.…”

Section: Tio 2 Based Dmsmentioning

confidence: 99%

Resonant soft X-ray emission spectroscopy of vanadium oxides andrelated compounds

Schmitt

2004

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Epitaxial growth of ferromagnetic Co:TiO2 thin films by co-sputtering

Cited by 17 publications

References 15 publications

Novel room temperature ferromagnetic semiconductors

Novel room temperature ferromagnetic semiconductors

The influence of hydrogen annealing on magnetism of Co-doped TiO2 films prepared by sol–gel method

Resonant soft X-ray emission spectroscopy of vanadium oxides andrelated compounds

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