Electrochemical aspects of the formation of Bi2Te3 thin film via the route of ECALE

A Bi2Te3 VA-VIA group compound thin film was prepared via the route of electrochemical atomic layer epitaxy in this paper. The dependence of thin film formation on the electrochemical conditions (such as deposition potential control, supporting electrolyte and substrate) was studied, and the formation process of Bi2Te3 film was determined. The results show that Bi upd on Pt occurs at more negative potential in a HNO3 supporting electrolyte than in a HClO4 supporting electrolyte, and the Te upd peak moves to a more negative potential in HClO4 supporting electrolyte solution than that in HNO3 solution; Both Te and Bi upd on an Ag substrate occur at more negative potentials than that on a Pt substrate. In order to reach steady state deposition, a potential adjustment is necessary for the first 30 or more cycles of each component. After deposition of this initial 'buffer layer', the potentials can be kept constant for the remaining cycles. The effect of the slope of the shift of potential used to deposit the first 30 atomic layers of Bi and Te on the deposit has also been investigated. The deposit exhibits a two phase mixture of excess elemental Bi and Bi2Te3 compound when the slope is larger than −4 mV/p (p indicates per cycle); a single-phase Bi2Te3 compound was obtained at a slope of −6 mV/p, and Bi4Te3 compound also appears in the deposit along with Bi2Te3 when the slope is decreased to a more negative value of −10 mV/p.