High Purity Pd Nanofilm Deposition Via Cu Incorporation Control in Slrr Process

Abstract

Department of Materials Science & Chemical Engineering, Hanyang University, Ansan 15588, Korea *byyoo@hanyang.ac.kr ABSTRACT The deposition of palladium has been considered in many industrial applications and in fundamental science because of the high catalytic activities. Careful control of smooth and continuous Pd film less than 1nm thickness is critical for achieving highly active catalysts. Furthermore, perspective of cost-effective view, minimum usage of Pd is essential for catalyst while showing maximum activity for catalyst due to its high cost.Electrochemical-atomic layer deposition (E-ALD), can achieve the growth of atomic level of metal film under room temperature and simple condition. E- ALD protocol proceeds using surface limited redox replacement (SLRR). SLRR involves 2 step. First, Au substrate is covered with Cu monolayer, the result of underpotential deposition of Cu (sacrificial element). Underpotential deposition (UPD) is the deposition occurs at more positive potential than equilibrium potential which the potential where deposition actually strats and UPD can limit Cu deposition by atomic layer. Second, Cu atomic layer is replaced by more noble metal (Pd) by galvanic displacement without applying potential. In one cell approach, the concentration ratio of sacrificial metal and noble metal and potential set is carefully set in order to deposit pure noble metal layer. Therefore, precise control of potential and metal concentration is important to execute successful SLRR which prevent Cu incorporation and Pd overpotential deposition upon Cu UPD formation.In this study, pure Pd nanofilm was formed on Au substrate using Cu sacrificial metal by SLRR protocol. Effort of minimizing Cu incorporation was conducted by controlling Pd ion concentration, potential , open circuit potential condition and adding additive. Pd film was characterized by XPS, AFM and open circuit potential was analyzed by potentiostat. By controlling Pd deposition condition, pure Pd film was successfully formed. KEYWORDS Palladium, one-cell, nanofilm, SLRR, Cu UPD