Structure, magnetic and electrical properties of soft magnetic Co–C amorphous thin films

Wang, Hao; Chiah, M.F.; Cheung, W.Y.; Wong, S. P.

doi:10.1016/s0375-9601(03)01135-6

Cited by 15 publications

(9 citation statements)

References 17 publications

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“…1 This is mainly associated with the high surface to volume ratio of the nanometer sized phase resulting in many interfaces between the constituent phases. Alternatively, the carbon matrix can be amorphous, 6,12,18,24 graphitelike with graphene layers curved into a cylindrical shape encapsulating elongated nanoparticles, [6][7][8][9][10][11][12][13]22,24 and fullerenelike with a spherical-like curvature encapsulating globular nanoparticles. 20 The structure of C:TM nanocomposite films consists of metal-rich nanoparticles embedded in a carbon matrix.…”

Section: Introductionmentioning

confidence: 99%

Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

Berndt

Abrasonis

Kovács

et al. 2011

Journal of Applied Physics

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Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputteringThe influence of transition metal (TM ¼ V,Co,Cu) type on the bulk diffusion induced structural changes in carbon:TM nanocomposite films is investigated. The TMs have been incorporated into the carbon matrix via ion beam co-sputtering, and subsequently the films have been vacuum annealed in the temperature range of 300 -700 C. The structure of both the dispersed metal rich and the carbon matrix phases has been determined by a combination of elastic recoil detection analysis, x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-grown films consist of carbidic (V and Co) and metallic (Cu) nanoparticles dispersed in the carbon matrix. Thermal annealing induces surface segregation of Co and Cu starting at ! 500 C, preceded by the carbide-metal transformation of Co-carbide nanoparticles at $ 300 C. No considerable morphological changes occur in C:V films. In contrast to the surface diffusion dominated regime where all the metals enhance the six-fold ring clustering of C, in the bulk diffusion controlled regime only Co acts as a catalyst for the carbon graphitization. These results are consistent with the metal-induced crystallization mechanism in the C:Co films. The results are discussed on the basis of the metal-carbide phase stability, carbon solubility in metals or their carbides, and interface species.

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Section: Introductionmentioning

confidence: 99%

Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

Berndt

Abrasonis

Kovács

et al. 2011

Journal of Applied Physics

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“…Compared to the proposed strong interaction between Co and O atoms [11], our results indicate that both N and O atoms accept charge from Co, but, during the initial deposition of Co, the charge was donated preferentially to N atoms. Up to 7.0 ML Co deposition, the C Is signal displayed as a broad feature at BE 283.0 eV, representing the formation of cobalt carbide [39], shown in Fig. 1(d).…”

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confidence: 97%

Effectiveness of organic molecules for spin filtering in an organic spin valve: Reaction-induced spin polarization for Co atopAlq3

et al. 2015

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The spin polarization of organic-ferromagnetic interfaces in an organic spin valve critically affects the efficiency of spin injection or detection. We examined the chemical and electronic properties of ferromagnetic Co deposited on organic Alq3 and the interfacial spin-polarized capability of the electronic states. Our x-ray photoemission spectra and calculations with density-functional theory indicate a sequential and unequal distribution of charge from Co clusters to N and then to O atoms in Alq3. The preferential orbital hybridization at specific functional sites produces efficient spin polarization of organic molecules. Element-specific measurements of x-ray magnetic circular dichroism demonstrate the preferential spin polarization in the lowest unoccupied molecular orbital state of N atoms at the complex interface for Co atop Alq3, which agrees satisfactorily with calculation. Our results indicate that an induced interfacial spin polarization on engineering the dominant reaction of Co with mainly N and O atoms in Alq3 might pave a way for effective spin filtering in organic spintronics.PACS number(s): 79.60. Fr, 75.70.Cn, 68.35.Fx, 75.76.+j Organic spin valves (OSV) in which an organic semicon ductor (OSC) spacer is sandwiched between two ferromagnetic (FM) electrodes have attracted much attention because of an enduring spin coherence of organic materials via weak spin-orbit coupling [1], Dediu et al. pioneered in achiev ing magnetoresistance (MR) up to 30% near 295 K in a LaovSrojMnOsfLSMOj/sexithiophenefTgj/LSMO OSV, ini tiating a great potential of organic-based spintronics [2], Xiong et al. subsequently made a remarkable observation of a giant MR at 40% at 11 K in a LSMO/Alq3/CoOSV [1], Among the most widely used OSC in OSV, tri(8-hydroxyquinoline) aluminum (Alq3) composed of 7r-conjugated molecules is considered to be a promising material for effective spin transport because of its great spin-relaxation time and unique molecular structure [1,3-6], The combination of Alq3 and d -band FM Co has achieved striking MR values [1,7-12], Although an ill-defined layer between Alq3 and top Co was manifested at an Alq3 thickness greater than 100 nm, it is one of few examples in which an OSV displayed a large MR [1], Such an ill-defined layer is ascribed to the diffusion of metal into a soft organic layer, which might be related to the disputed results of the MR sign and mechanism [1,12-15], To prevent the unexpected interdiffusion and chemical interaction at the interfacial region, a buffer layer inserted between the top Co and Alq3 has improved the device performance [9,16-18]. Although metal interdiffusion is preventable with those meth ods, it might not provide a deep understanding of the lacking essential mechanisms [19][20][21]. Moreover, in the case of an OSV with no buffer layer, a large MR was still achieved [1,8]. Various techniques have been used to engineer, to control, or to detect the efficient spin injection and transport [ 1,4,22,23] 'jenghan @ on traditionally applying a specific bias voltage to...

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“…In this second arrangement, fast rotation of the composite target allowed periodic ablation of the graphite and the metal foil to produce a mixed material. The two metals investigated were Ni and Co, as the incorporation of these elements has been shown to increase the electrical conductivity of a-C [12,13]. Figure 3 shows a series of SEM images of NPC:Ni samples deposited at different P Ar , by ablating the composite target.…”

Section: Resultsmentioning

confidence: 99%

“…The doping of a-C thin films by incorporation of metals has been attempted and it was found that the mechanical, tribological, and electrical properties are all strongly influenced by the metal content in the films [10,11]. For example, electrical conductivity could be increased many orders of magnitude by varying the metal content [11][12][13]. In this paper we investigate the incorporation of metal into the NPC films deposited by PLA of graphite.…”

Section: Introductionmentioning

confidence: 99%

Metal incorporation into nanoporous carbon

et al. 2005

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Nanoporous carbon films were deposited by 248 nm pulsed laser ablation of a graphite target in different background pressures of argon (P Ar ). The morphology changed from smooth, high-density amorphous carbon films at P Ar = 20 mTorr to ultra-low density nanoporous material at P Ar = 380 mTorr. Subsequently, the nanostructural, chemical and electrical properties of metal containing nanoporous carbon samples were investigated by ablating graphite targets containing known contents of Ni and Co. We demonstrate how the ablation plume dynamics affect both the nanostructure of the material and the incorporation of metal atoms. The suitability of these functionalised ultra-low density materials for gas sensing applications is discussed.

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Structure, magnetic and electrical properties of soft magnetic Co–C amorphous thin films

Cited by 15 publications

References 17 publications

Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

Effectiveness of organic molecules for spin filtering in an organic spin valve: Reaction-induced spin polarization for Co atopAlq3

Metal incorporation into nanoporous carbon

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