Abstract
We have used infra-red reflectivity to investigate the nature of the intralayer bonding forces in a variety of layered crystals. Analysis of the reflectance spectra of PbI2, CdI2, SnS2 and SnSe2 indicates significant anisotropies in the frequencies of the long-wave-length TO phonons: the frequency of theA2u mode for out-of-plane atomic displacements (E‖c) is greater than that of theEu mode for in-plane displacements (E⊥c). For CdI2-structured crystals, these frequency differences can be attributed to dipolar interactions and as such provide a measure of the charge localized on the atomic sites. The analysis is extended to the group IVB and VIB transition metal dichalcogenides. The IVB crystals, ZrS2, HfS2, etc., are found to be substantially more ionic,fi∼0.5, than the group VIB crystals, MoS2, WS2, etc.,fi∼0.1.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
