Formation of Beta-Indium Selenide Layers Grown Via Selenium Passivation of InP(111)B Substrate

Indium selenide, In2Se3, has recently attracted growing interest due to itsnovel properties, including room temperature ferroelectricity, outstandingphotoresponsivity, and exotic in-plane ferroelectricity, which open up newregimes for next generation electronics. In2Se3 also provides the importantadvantage of tuning the electrical properties of ultra-thin layers with anexternal electrical and magnetic field, making it a potential platform to studynovel two-dimensional physics. Yet, In2Se3 has many different polymorphs, andit has been challenging to synthesize single-phase material, especially usingscalable growth methods, as needed for technological applications. In thispaper, we use aberration-corrected scanning transmission electron microscopy tocharacterize the microstructure of twin-free single-phase ultra-thin layers ofbeta-In2Se3, prepared by a unique molecular beam epitaxy approach. We emphasizefeatures of the In2Se3 layer and In2Se3/InP interface which provide evidencefor understanding the growth mechanism of the single-phase In2Se3. This novelapproach for forming high-quality twin-free single phase two-dimensionalcrystals on InP substrates is likely to be applicable to other technologicallyimportant substrates.