Effect of Deposition Time and Current Density on Kinetic Roughening of Electrodeposited Pt Thin Films

摘要

Electrodeposition is an inexpensive and versatile method of preparing thin metal films that, unlike most alternatives, does not require a vacuum system. In these techniques a material (metal, alloy or semiconductor) is evaporated or sputtered and deposited on a substrate to form a thin film. However, the required equipment is complicated and expensive. Electrodeposition as an alternative deposition technique is economically important because of its low cost and flexibility. Although electrodeposition of thin films first found widespread applications in decorative and protective coatings, it now plays an important role in producing microelectronic devices in the electronics industry. Electrodeposition usually refers to deposition of a metal or an alloy from an electrolyte by passing a charge between the two electrodes located in the electrolyte. If an external power supply drives a current through the cell, metal ions are reduced to metal atoms at one of the electrodes known as the cathode.The deposition rate for a given electrode depends on the current density (or cathode potential), so that the more negative the current density (or cathode potential), the faster the electrochemical reaction and, therefore the higher the deposition rate.Despite the simplicity in experimental set up and low cost, the phenomenon of electrodeposition is very complex, since it is typically a non-equilibrium growth process and it involves so many variables, such as electrolyte pH and concentration, cation diffusion, and type of substrate. Films grown under non-equilibrium conditions are expected to develop self-affine surfaces (1), whose RMS roughness (defined as Eq. 1) varies as a function of film thickness according to Eqs. 2 and Egs. 3.