Electrodeposition and characterisation of nickel, germanium and tin thin films

Abstract

The electrodeposition and characterisation of metals, Ni, Ni-B and Sn and a semi-conductor, Ge are the objectives of this study. Electrodeposition is an important metal surface coating technique as it can smoothly coat large and complex objects in a convenient and economically viable way. We are examining the microstructure of the films electrodeposited in this work using a variety of X-ray diffraction techniques, scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy.

Nickel coatings have wide applications in decorative and functional applications as hard, corrosion resistant surfaces. Boron is often incorporated into electrodeposited Ni using the standard Watt’s bath (nickel chloride/nickel sulphate/boric acid) and adding dimethylamine borane as the source of boron, the electrodepositions are achieved by chronopotentiometry.

Germanium is an important semi-conductor, its widest application areas are optoelectronics and photonics. Ge films have been electrodeposited from tetrabutylammonium chlorogermanate [nBu4N][GeCl3] in tetrabutylammonium chloride [nBu4N]Cl dichloromethane solution, using chronoamperometry. The as-deposited Ge is amorphous. High temperature thermal annealing under anaerobic condition is applied to the films to crystallise.

Tin is a soft, pliable and highly crystalline element with wide range of applications including decoration, electronic, and optical areas. Electrodeposition of tin is achieved from an electrolyte containing tetrabutylammonium chlorostannate [nBu4N][SnCl3] and tetrabutylammonium chloride [nBu4N]Cl in dichloromethane solution, using chronoamperometry. Flat tin films on Au sputtered on glass substrates, nanowire tin in phosphonate grafted anodic alumina and un-grafted AAO membranes were produced. Electrodepositions on Au substrate were obtained at various temperatures.

Ni was electrodeposited in a highly crystalline form. The addition of B to the Ni matrix has reduced the degree of crystallinity and raised the amount of stress in the films. These effects were enhanced by increasing the amount of added B. Great influence on the preferred orientation of the Ni crystals was observed with the variations in the thickness and current density. In the Ge electrodeposition, modifications to the electrolyte composition and the substrate resulted in various morphologies and quality of adhesions in the Ge films, which was effective in the adhesion in the films after the annealing. Sn films were produced in a high crystalline form, electrodeposition at various temperature developed effects on the morphology and the texture of the electrodeposited Sn film. Characterisation on the Sn inside the anodic alumina templates indicates various diameter wires grown inside the membranes.

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ORCID for Andrew L. Hector: orcid.org/0000-0002-9964-2163

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