Polarized Raman spectroscopy to elucidate the texture of synthesized MoS2.

ABSTRACT

Texture has a significant impact on several key properties of transition-metal dichalcogenides (TMDs) films. Films with in-plane oriented grains have been successfully implemented in nano- and opto-electronic devices, whereas, films with out-of-plane oriented material have shown excellent performance in catalytic applications. It will be demonstrated that the texture of nanocrystalline TMD films can be determined with polarized Raman spectroscopy. A model describing the impact of texture on the Raman response of 2D-TMDs will be presented. For the specific case of MoS2, the model was used to quantify the impact of texture on the relative strength of the A1g and E12g modes in both the unpolarized and polarized Raman configuration. Subsequently, the capability to characterize texture by polarized Raman was demonstrated on various MoS2 films grown by atomic-layer deposition (ALD) and validated by complementary transmission electron microscopy (TEM) and synchrotron based 2D grazing-incidence X-ray diffraction (GIXD) measurements. This also revealed how the texture evolved during ALD growth of MoS2 and subsequent annealing of the films. The insights presented in this work allow a deeper understanding of Raman spectra of nanocrystalline TMDs and enable a rapid and non-destructive method to probe texture.