Cobalt film

P.N. Bartlett, P.N. Birkin, M.A. Ghanem, P. de Groot, and M. Sawickib, The electrochemical deposition of nanostructured cobalt films from lyotropic liquid crystalline media. J. Electrochem. Soc. 148, Cl 19-023 (2001). 

Lahtinen, J., Anraku, T., and Somotjai, G. A. 1993. Carbon monoxide hydrogenation on cobalt foil and on thin cobalt film model catalysts. J. Catal. 142 206-25. 

Chan YL, Hung YJ, Wang CH, Lin YC, Chiu CY, Lai TL, Chang HT, Lee CH, Hsu YJ, Wei DH (2010) Magnetic response of an ultrathin cobalt film in contact with an organic pentacene layer. Phys Rev Lett 104 177204... 

A point which has not been examined is the nature of the surface during exchange reactions carried out at high temperatures such as those required for the exchange of methane. Surface carbides may be formed under these conditions. The inactivity of iron films and the comparatively small activity of cobalt films at 300° for the exchange of ethane 19) may possibly be due to the tendency of these metals to form not only surface but also bulk carbides. 

Recent interest in cobalt films has been driven by the importance of cobalt oxides as cathode materials in hthium batteries. Many different precursors have been employed for the MOCVD growth of cobalt-containing thin films. Diketonate-based precursors include Co(acac)2, Co(tmhd)2, Co(tmhd)3, Co(hfac)2, Co(tmhd)2(tmeda), Co(hfac)2(H20)2, and Co(hfac)2(H20)2 tetraglyme. Carbonyl-based precnrsors (see Carbonyl Complexes of the Transition Metals) inclnde Co2(CO)g, Co(C5H5)(CO)2, various cobalt carbonyl clnsters, Co(CO)3(NO), and Co(CO)2(NO)L (L = PEts, TeMc2, TeEt2). Other cobalt precursors include CoH(P(OnPr)(OMe)2)4, Co(N03)3, and Co(rBu NC(CH3)NtBu)2. ... 

In these experiments a sample of cobalt/molybdenum disulfide was mounted on the heater ribbon in close proximity to a cobalt/graphite specimen, which was positioned in the path of the electron beam. All specimens were initially treated in 1.0 Torr hydrogen for l.Q hours at 360°C. and under these conditions the cobalt film nucleated to form particles. 2.5 - 5.0 nm diam. on the graphite surface. At the same time these particles were being exposed to hydrogen disulfide produced during the cobalt catalyzed hydrogenation of molybdenum disulfide, a reaction which had been previously found to proceed at appreciable rates at ten ratures above 250°C (ref. 16). 

M.A. (2000) Electrochemical deposition of macroporous platinum, palladium and cobalt films using polystyrene latex sphere templates. Chemical Communications, 1671-1672. 

The results from a careful study (139) of the reactions of a number of polymethylcycloalkanes (10-16) on cobalt films in the presence of deuterium at 100°-215°C may be summarized as follows ... 

Figure 3.36 The chloro(octaethylporphyrin)iron(III) molecule. Calculations and experiment suggest that the chloride may be lost and Fe is present upon surface binding to the nickel or cobalt film...

Barzilai, S, Goldstein, Y, Balberg, I. andHelman, J.S. (1981) Magnetic and transport properties of granular cobalt films. Phys. Rev. B, 23, 1809-1817. 

Figure 7 Kerr hysteresis loop of a cobalt film, electrodeposited from a bath containing 0.104M C0SO4 and 0.5M Na2S04, at -1.15V during 60s.

The similarities between the CO adsorption properties of cobalt and those of iron evaporated metal films have already been mentioned. The calorimetric heat of CO on cobalt films is very close to that on iron 80) as is the surface potential caused by this adsorption 123). The CO uptakes on catalysts of the three metals iron, cobalt, and nickel have also been reported to be very close in value 133), although the group Vlllb and c elements all crystallize normally in face center cubic lattices, unlike the group Villa metals. 

Infrared studies on evaporated cobalt films 91) show an extreme similarity to the spectra obtained on iron films evaporated under the same conditions. They show a maximum in absorption at 1990 cm with a broad tail extending below 1800 cm when CO is adsorbed at... 

The reaction is carried out at atmospheric pressure using a vapourization temperature of 150°C, a condenser temperature of 170°C, a carrier gas flow-rate of 1.2 to 2.8 1 min 1 and a deposition or substrate temperature of 340°C. These conditions are considered optimum because they produced thin metallic cobalt films having the same magnetic properties as bulk cobalt. A deposition time of 8 - 10 min resulted in films of about 0.6 pm thickness on glass substrates. Cobalt films can also be prepared by pyrolysis of cobalt nitrosyl tricarbonyl ... 

Due to the in-plane surface anisotropy [23] the easy magnetization axis in thin iron films is the in-plane [110] direction being the hard magnetization axis of bulk Fe, switching at a critical thickness to the one of bulk crystals, i.e. the [001] direction. For cobalt films the anisotropy causes the easy magnetization axis to lie in-plane in contrast to bulk-hcp Co with its easy axis perpendicular to the basal plane. Thick rare earth metal films exhibit an easy axis within the surface plane. The shape anisotropy may also change the easy magnetization axis. 

Fig. 5.17 Left part energy dependence of the photoelectron spectra analogously obtained to Fig. 5.16. The islands were created by heating an epitaxial cobalt film to about 1,000 K. From [55], used with permission. Right part for comparison, a fully relativistically calculated band structure for hcp(OOOl) bulk cobalt with in-plane magnetization is displayed. This calculation takes into account both spin-orbit interaction and exchange splitting on the same level of accuracy. The circles in the initial states show two regions where hybridization effects arc present. Reprinted from [28], Copyright (1998), with permission from Elsevier...

In present work we study the magnetic domain structure of cobalt film near SRT and the influence of an external magnetic field on it by MFM. 

Applications in studies of magnetic layers and monolayers have been reported frequently [663, 664]. Ultrathin cobalt film that is deposited under particularly clean conditions has been studied [665]. In ex situ studies of electrochemically deposited mono- and multilayers, SMOKE has been employed [666, 664]. The capability of MOKE to study buried interfaces has been demonstrated [667]. 

Transmission electron micrographs (TEMs) confirmed the porosity of the NiO nanotubes and further revealed their substructure to be nanocrystalline with crystallite sizes ranging from 5 to 10 nm, see Fig. 6.7. The oxidation of nanopatterned cobalt films worked equally well [18]. The gyroid structure was nicely preserved during oxidation. The XRD data present in Fig. 6.8 suggests a complete conversion to C03 O4. Nanostructured cobalt oxide is a battery electrode material, but due to time constrains this was not tested in this study. 

Fig. 6.8 XRD patterns of a bare FTO substrate (a), a DG-structured metaiiic (b) and thennaliy oxidized (c) cobalt film annealed at 600 C for 6h. Cu K radiation was used and the patterns were matched with the corresponding tetragonal SnOi (PDF number 046-1088), cubic Co (PDF number 015-0806), and cubic C03O4 (PDF number 042-1467)...

Fig. 19 Schematic depictions of (a) the preparation of a cobalt pyrite (C0S2) film electrode via the thermal sulfidation of a 100 nm thick cobalt film deposited over a titanium adhesion layer on a roughened borosilicate glass substrate by electron-beam evaporation and (b) the incorporation of an as-synthesized C0S2 film on glass into a CdS/ CdSe-sensitized thin-layer liquid-junction quantum dot-sensitized solar cell (QDSSC) filled with sulfide/polysulfide electrolyte to demonstrate the high QDSSC performance enabled by the C0S2 counter electrode. Reproduced from ref. 167 with permission from the American Chemical Society.

---