In-depth understanding of the band alignment and interface states scenario in Bi2O2Se/SrTiO3 ultrathin heterojunction

AbstractBismuth oxyselenide (Bi2O2Se), a novel quasi-two-dimensional charge-carrying semiconductor, is recognized as one of the most promising emerging platforms for next-generation semiconductor devices. Recent advancements in the development of diverse Bi2O2Se heterojunctions have unveiled extensive potential applications in both electronics and optoelectronics. However, achieving an in-depth understanding of band alignment and particularly interface dynamics remains a significant challenge. In this study, we conduct a comprehensive experimental investigation into band alignment utilizing high-resolution X-ray photoelectron spectroscopy (HRXPS), while also thoroughly discussing the properties of interface states. Our findings reveal that ultrathin films of Bi2O2Se grown on SrTiO3 (with TiO2 (001) termination) exhibit Type-I (straddling gap) band alignment characterized by a valence band offset (VBO) of approximately 1.77 +/- 0.04 eV and a conduction band offset (CBO) around 0.68 +/- 0.04 eV. Notably, when accounting for the influence of interface states, the bands at the interface display a herringbone configuration due to substantial built-in electric fields, which markedly deviate from conventional band alignments. Thus, our results provide valuable insights for advancing high-efficiency electronic and optoelectronic devices, particularly those where charge transfer is highly sensitive to interface states. (sic)(sic)(sic)(sic)(sic) (Bi2O2Se), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).Bi2O2Se(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)X(sic)(sic)(sic)(sic)(sic)(sic)(sic) (HRXPS) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic), (sic)SrTiO3(TiO2(001) (sic)) (sic)(sic)(sic)(sic)(sic)(sic)Bi2O2Se(sic)(sic)(sic)(sic)(sic)(sic)(sic)I ((sic)(sic)) (sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic) (VBO) (sic)(sic)1.77 +/- 0.04 eV, (sic)(sic)(sic)(sic) (CBO) (sic)(sic)0.68 +/- 0.04 eV.(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).