Study On High-aspect-ratio Gold Nano Structures Electrochemical Deposition Based On A Pulse Reverse Function

Gold nano-and micro-structures formed by electrochemical deposition are widely used in a variety of research fields including Microelectronics,MEMS and Optoelectronics.However,gold electrochemical deposition is still challenging due to toxicity and disposal concerns of cyanide electrolyte,which has been banned in many countries.In comparison,the non-toxic gold sulfite plating solution is considered to be the most potential plating solution because of its high dispersion and high quality.Nevertheless,there are still some problems in its research,such as poor stability and unclear mechanism of nucleation and growth.Herein,in sulfite electrolyte system a novel square pulse reverse function of current source will be utilized which plays a critical role in formation and growth of nuclei in forward pulse and the dissolution in reversal pulse.Larger positive pulses were used to promote the rate of nucleation and further growth,and reverse pulses were used to inhibit excessive growth of grains and etch the surface protrusion of coatings,which were added to the diffusion layer to improve the uniformity of ion distribution.To investigate the effect of a new square wave pulse reversal function on nucleation formation and competitive growth during electrochemical deposition.The nucleation and growth rate of nucleus in non-toxic sulfite plating bath were adjusted by tuning pulse current density,and the growth direction of Au microstructure was controlled.On the other hand,the effect of pulse reverse current on the morphology and atomic arrangement of gold films was studied.Firstly,to more clearly understand the mechanism of deposition with pulse reverse function,SEM,AFM,XRD,TEM and TKD will be used to characterize the nuclei creation and competitive growth.Secondly,through the analysis of the characterization results,the nucleus are rapidly uniformly distributed on the cathode and grow preferentially to single crystals with certain defects along the<111>direction,when the optimum forward current density is 8.9 mA/cm2.Going on above results,the higher ion dispersion of the diffusion layer after introducing the best reverse current of 0.4 mA can basically eliminate defects and mixed crystals and obtain standard single crystalline.Based on above results,the high aspect ratio structures with more dense microstructures,lower roughness and height difference were obtained.Finally,the high aspect ratio gold structures with 100 nm lateral resolution and more than 0.9 ? m height will be formed by optimized electrochemical deposition method.