biostudies-literatureAthena FFIBM ResearchAir Force Office of Scientific ResearchStanford Precourt Institute for EnergyNational Science Foundatione18784https://www.ebi.ac.uk/biostudies/studies/S-EPMC12904008biostudies-literatureUnknown13(9)Since the initial synthesis of van der Waals 2D indium selenide is first documented in 1957, five distinct polymorphs and their corresponding polytypes are identified. In this study, a unique phase of indium selenide is reported via Scanning Transmission Electron Microscopy (STEM) analysis in the synthesized large-area films - which is named the βp$\ubeta^{\text{p}}$ phase. The quintuple layers of the βp$\ubeta^{\text{p}}$ phase, characterized by a unique zigzag atomic configuration with unequal indium-selenium bond lengths from the middle selenium atom, are distinct from any other previously reported phase of indium selenide. Cross-sectional STEM analysis has revealed that the βp$\ubeta^{\text{p}}$ layers exhibit intralayer shifting. It is found that indium selenide films with βp$\ubeta^{Advanced science (Weinheim, Baden-Wurttemberg, Germany)A Van der Waals Material Exhibiting Room Temperature Broken Inversion Symmetry with Ferroelectricity.PMC12904008ECCS‐1542174IBM PhD FellowshipNNCI‐2025608DMR-2004749FA9550-18-1-0024FA9550‐18‐1‐0024Stanford Energy Postdoctoral FellowshipECCS-1542174DMR‐2004749NNCI-2025608Tian MJeon SWagner BKGoswami AVoigt CAMammo FAthena FFNnaji MToph ECai WVogel EMfalseA Van der Waals Material Exhibiting Room Temperature Broken Inversion Symmetry with Ferroelectricity.Since the initial synthesis of van der Waals 2D indium selenide is first documented in 1957, five distinct polymorphs and their corresponding polytypes are identified. In this study, a unique phase of indium selenide is reported via Scanning Transmission Electron Microscopy (STEM) analysis in the synthesized large-area films - which is named the βp$\ubeta^{\text{p}}$ phase. The quintuple layers of the βp$\ubeta^{\text{p}}$ phase, characterized by a unique zigzag atomic configuration with unequal indium-selenium bond lengths from the middle selenium atom, are distinct from any other previously reported phase of indium selenide. Cross-sectional STEM analysis has revealed that the βp$\ubeta^{\text{p}}$ layers exhibit intralayer shifting. It is found that indium selenide films with βp$\ubeta^{2026-01-01T00:00:00Z2026 Feb2026-07-15T15:36:07.999Z2026-07-06T03:11:00.33ZS-EPMC129040084134767810.1002/advs.202518784