Synthesis of α-Bi/SrTiO3 heterostructure through the Eu-induced reduction of Bi2O2Se/SrTiO3

Thin Bi films, especially noncentrosymmetric alpha-phase Bi films (alpha-Bi), have attracted considerable attention in recent years due to their intriguing physical properties such as ferroelectricity, nonlinear optical response, and coherent spin transport. However, the current experimental preparation of alpha-Bi films still presents substantial challenges, resulting in only isolated alpha-Bi islands being achieved. In this study, alpha-Bi/SrTiO3 (alpha-Bi/STO) was synthesized from a Bi2O2Se/STO (BOS/STO) heterostructure by depositing a Eu layer and reducing a BOS film. The so-formed alpha-Bi/STO interface features metallic conductivity with electron mobility of 7.7 x 10(4) cm(2)/V s and ultralow resistivity of 1 n Omega cm at 2 K, as well as high residual resistance ratios R-300 K/R-2 K up to 2353. Furthermore, we observed a complex weak antilocalization-weak localization-weak antilocalization crossover with increasing magnetic field at temperatures below 10 K. Our work presents the synthesis of alpha-Bi films, which could potentially serve as a valuable platform for experimental validation of diverse theoretical predictions associated with alpha-Bi heterostructures. Furthermore, this special synthesis method provides valuable insights into the preparation of other metastable films.