Electrochemical intercalation and etching in Bi₂Se₃ thin-film ion-gated transistors

Abstract By adjusting the gate voltage and temperature of the ion-gated transistors, the physical properties of channel material can be regulated via electrostatic gating, electrochemical intercalation and electrochemical etching effects. Here, we report the evolution of electrical transport properties of the topological insulator Bi 2 Se 3 -based ion-gated transistor. We observed a large variation in the sheet conductance from 4.9 mS to 9.0 mS and sheet electron density from 3.5 × 10 13 cm −2 to 6.3 × 10 14 cm −2 for 50.9 nm thick films due to the contribution of electrostatic gating and K intercalation. The density of intercalated K was detected as an atomic fraction of 5.1% ± 1.8% by mass spectroscopy. Exceeding the critical cycles of gating, the sheet conductance decreases, signaling the reduction of the thickness of the film due to the occurrence of electrochemical etching. These findings are fundamental knowledge for understanding the operation of Bi 2 Se 3 -based ion-gated transistors.