Deposition Modes of Cobalt from Sulfate-Chloride Solutions

Sard, R.; Schwartz, Cédric; Weil, R.

doi:10.1149/1.2423988

Cited by 30 publications

(25 citation statements)

References 13 publications

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“…Several authors have shown that the electrochemical phase formation in Co-layers is strongly affected by the pH value [5][6][7]. Uhlemann et al [8] have reported that the increase of the pH value at the electrode surface during the electrodeposition of Co is lower in magnetic fields applied parallel to the electrode compared to the case without magnetic field.…”

Section: Introductionmentioning

confidence: 99%

A study of nucleation, growth, texture and phase formation of electrodeposited cobalt layers and the influence of magnetic fields

et al. 2006

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Section: Introductionmentioning

confidence: 99%

A study of nucleation, growth, texture and phase formation of electrodeposited cobalt layers and the influence of magnetic fields

et al. 2006

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“…Several researchers 9,[13][14][15][16][17][18][19][20][21][22] have reported that the pH of the bath solution significantly affects the structure of cobalt formed by electrodeposition. A solution with a low pH (Ͻ2.5) was reported to favor fcc cobalt, 9,[13][14][15][16][17][18][19][20][21][22] whereas a high pH (Ͼ2.5) or a high temperature system favored the formation of hcp cobalt in a sulfate bath with no organic additives.…”

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“…A solution with a low pH (Ͻ2.5) was reported to favor fcc cobalt, 9,[13][14][15][16][17][18][19][20][21][22] whereas a high pH (Ͼ2.5) or a high temperature system favored the formation of hcp cobalt in a sulfate bath with no organic additives. 14 Agitation of a sulfate bath also favored hcp cobalt.…”

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Structure of Electrodeposited Cobalt

Cohen-Hyams

Kaplan

Yahalom

2002

Electrochem. Solid-State Lett.

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The structure of cobalt formed by electrodeposition and the influence of the pH of the plating solution and the cathode potential was studied by potentiodynamic measurements and X-ray diffraction. It was found that the level of overpotential significantly affects the structure of the formed cobalt. When electrodeposition is performed far from equilibrium conditions, i.e., at a high overpotential, face-centered cubic ͑fcc͒ cobalt is deposited while at low overpotential hexagonal close packed Co is formed with a lower rate of hydrogen evolution. A higher overpotential is needed in a neutral compared to acidic solution in order to enhance the evolution of hydrogen that is required for the formation of fcc cobalt.There is a growing interest in magnetic thin films, especially in cobalt films, due to their wide range of application as magnetic data storage devices. 1-5 These films are usually prepared by physical deposition methods which require ultrahigh vacuum techniques. [6][7] An alternative processing technique is electrodeposition. Electrodeposition has several advantages over dry processes. 8 Electrodeposition does not require vacuum technology and consequently is less expensive. It can easily be upscaled for use in large size areas, and it is capable of depositing uniform films on complex surfaces without the shadowing effects often encountered in other deposition methods. The experimental systems used are much simpler than evaporation or sputtering apparatus, and electrodeposition can be a room-temperature technology. However, there are some drawbacks associated with the process, such as the need for a conducting/ semiconducting substrate, the limited number of elements that can be deposited, and the large number of variables that influence this process ͑composition, pH, concentration, current density, temperature, agitation, etc.͒.Hexagonal close packing ͑hcp͒ is the usual structure for electroplated cobalt. It is also known, 9 that face-centered cubic ͑fcc͒ cobalt, which is stable at temperatures above 422°C, can sometimes be obtained from electrodeposition at ambient temperatures. Gelchinski et al. 10 have electroplated, at room temperature, cobalt-chromium alloys containing the cP8 structure type, 11,12 that is stable only at high temperatures, according to the equilibrium phase diagram.Several researchers 9,13-22 have reported that the pH of the bath solution significantly affects the structure of cobalt formed by electrodeposition. A solution with a low pH (Ͻ2.5) was reported to favor fcc cobalt, 9,13-22 whereas a high pH (Ͼ2.5) or a high temperature system favored the formation of hcp cobalt in a sulfate bath with no organic additives. 14 Agitation of a sulfate bath also favored hcp cobalt. A high deposition temperature in a chloride bath also induced the formation of hcp cobalt, 17,18 whereas high current densities in sulfamate solutions were found to favor the cubic structure. 19 In addition, a high degree of preferred orientation has been observed by Sard et al. 18 for cobalt formed in sulfate baths....

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“…In the case of electrodeposited films, the formation of fcc Co depends on pH values of solution. For example, fcc Co formed in electrodeposition from solutions with pHo2.4 whereas hcp Co was produced in electrodeposition from solutions with pH42.9 [1,9]. An earlier model explaining formation of fcc Co was proposed by Nakahara and Mahajan [1].…”

Section: Introductionmentioning

confidence: 99%