Tailoring band offset dynamics in WSe2/In2Se3 van der waals heterointerfaces by X-ray photoelectron spectroscopy

초록

Ferroelectric optoelectronic devices have attracted growing interest for self-powered photodetection owing to their intrinsic polarization, which can provide a built-in electric field without external bias or chemical doping. However, conventional ferroelectric oxides suffer from wide bandgaps and critical thickness limitations, restricting their applicability in ultrathin, broadband optoelectronic devices. In this work, we construct a van der Waals (vdW) heterointerface composed of p-type tungsten diselenide (WSe2) and ferroelectric alpha-phase indium (III) selenide (alpha-In2Se3), and systematically investigate its interfacial band alignment using X-ray photoelectron spectroscopy technique. Raman measurement and X-ray diffraction analyses were used to confirm the vibrational properties and crystalline phases of WSe2 and alpha-In2Se3, respectively. Quantitative band alignment analysis reveals band offset of 0.83 +/- 0.05 eV and 0.55 +/- 0.05 eV for valence and conduction bands, respectively, establishing a type-II staggered band alignment accompanied by pronounced band bending induced by interfacial dipoles and charge redistribution. Exploiting the established type-II band alignment, a WSe2/In2Se3 pn heterojunction photodetector is designed, exhibiting efficient photovoltaic effect and broadband photoresponse. These results highlight the critical role of interfacial band offset engineering in vdW heterostructures and demonstrate the strong potential of WSe2/In2Se3 vdW heterointerfaces for future self-powered photodetecting devices.

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