Sequentially PVD-Grown Indium and Gallium Selenides Under Compositional and Layer Thickness Variation: Preparation, Structural and Optical Characterization

Group IIIA metal chalcogenides are an auspicious material system due to their variability of properties and hence the multitude of application options, for example, in the fields of optoelectronic, thermoelectric, piezo-, and ferroelectric devices. Indium and gallium selenide films are innovatively grown in a sequential PVD (physical vapor deposition) process starting from metal precursor layers of various thicknesses, which are then subject to chalcogenization in different selenium contents. The resulting thin films are investigated for structural and optical properties by Raman, XRD (X-ray diffraction), and UV-Vis-NIR spectrometry, revealing that all the compounds In2Se3, InSe, In4Se3, Ga2Se3, and GaSe as well as different polytypes can be achieved depending on the metal/chalcogen ratio. Results from Raman and XRD spectroscopy are highly consistent, and also from the optical measurements changes in absorption characteristics can be correlated. The results indicate, that by fine-tuning the selenium content, deliberately growing ultra-thin layers of the different indium and gallium phases will be possible, thus opening up a promising route for 2D material fabrication. Given the scalability of the fabrication method, it is highly promising for large-scale deployment of the materials.