Preferred Orientation Control of Bi Deposits Using Experimental Strategies

Abstract

Based on the experimental strategy of fractional factorial design (FFD) and path of the steepest descent/ascent (PSD/PSA), the preferred orientation ratio of Bi(110)/Bi(012) facets of Bi deposits electroplated under a direct-current (dc) mode could be precisely controlled and predicted. The intensity ratio of Bi(110)/Bi(012) facets (i.e., the preferred orientation ratio which is denoted as f) was employed as the response variable since this variable was found to be one of the key factors determining the sensitive ability of bismuth-film electrodes (BFEs) to Sn(II). In the FFD study, temperature of the plating bath was identified to be the key factor affecting the preferred orientation ratio of Bi deposits meanwhile f only weakly depended on pH, current density, and stirring rate. From the PSD/PSA study, a simple but reliable model for changing the preferred orientation ratio was constructed and the deposit plated at 28°C and pH = 4.25 showed the highest f value. Moreover, BFEs with various f values could be easily prepared and controlled, meanwhile the morphologies of Bi deposits with different f values were also examined in this work.