Temperature-Dependent Raman Scattering Investigation on vdW Epitaxial PbI2/CrOCl Heterostructure

Van der Waals (vdW) epitaxial growth provides an efficient strategy to prepare heterostructures with atomically and electronically sharp interfaces. Herein, PbI2 was in situ thermally deposited onto exfoliated thin-layered CrOCl nanoflakes in high vacuum to fabricate vdW PbI2/CrOCl heterostructures. Optical microscopy, atomic force microscopy, X-ray diffraction, and temperature-dependent Raman spectroscopy were used to investigate the structural properties and phonon behaviors of the heterostructures. The morphology of PbI2 films on the CrOCl substrate obviously depended on the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. In addition, anomalous blueshift of the A(g)(1) and A(u)(2) modes as the temperature increased in PbI2/CrOCl heterostructure was observed for the first time. Our results provide a novel material platform for the vdW heterostructure and a possible method for optimizing heterostructure growth behaviors.

Automated summary

Van der Waals (vdW) epitaxial growth was used to prepare vdW PbI2/CrOCl heterostructures by in situ thermally depositing PbI2 onto exfoliated thin-layered CrOCl nanoflakes in high vacuum. The structural properties and phonon behaviors of the heterostructures were investigated using optical microscopy, atomic force microscopy, X-ray diffraction, and temperature-dependent Raman spectroscopy. The morphology of PbI2 films on the CrOCl substrate varied with the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. An anomalous blueshift of the A(g)(1) and A(u)(2) mode in the PbI2/CrOCl heterostructure with increasing temperature was observed for the first time. The results provide a new material platform for vdW heterostructures and a potential method for optimizing heterostructure growth behaviors.