Precision Control\nof Amphoteric Doping in Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3</sub> Nanoplates

Copper-doped Bi<sub>2</sub>Se<sub>3</sub> (Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3</sub>) is of considerable\ninterest for\ntailoring its electronic properties and inducing exotic charge correlations\nwhile retaining the unique Dirac surface states. However, the copper\ndopants in Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3</sub> display complex electronic behaviors and may function as either\nelectron donors or acceptors depending on their concentration and\natomic sites within the Bi<sub>2</sub>Se<sub>3</sub> crystal lattice.\nThus, a precise understanding and control of the doping concentration\nand sites is of both fundamental and practical significance. Herein,\nwe report a solution-based one-pot synthesis of Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3</sub> nanoplates with systematically\ntunable Cu doping concentrations and doping sites. Our studies reveal\na gradual evolution from intercalative sites to substitutional sites\nwith increasing Cu concentrations. The Cu atoms at intercalative sites\nfunction as electron donors while those at the substitutional sites\nfunction as electron acceptors, producing distinct effects on the\nelectronic properties of the resulting materials. We further show\nthat Cu<sub>0.18</sub>Bi<sub>2</sub>Se<sub>3</sub> exhibits superconducting\nbehavior, which is not present in Bi<sub>2</sub>Se<sub>3</sub>, highlighting\nthe essential role of Cu doping in tailoring exotic quantum properties.\nThis study establishes an efficient methodology for precise synthesis\nof Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3</sub> with\ntailored doping concentrations, doping sites, and electronic properties.