Synthesis, structural, X-ray photoelectron spectroscopy (XPS) studies and IR induced anisotropy of Tl₄HgI₆ single crystals

In the present work, we report on the synthesis and structural properties including X-ray protoelectron spectroscopy (XPS) analysis of Tl₄HgI₆ crystals that were grown by Bridgman-Stockbarger method up to 80 mm in length and 18 mm in diameter. The existence of the ternary compound Tl₄HgI₆ that melts incongruently at 641 K was confirmed. Phase equilibria and structural properties for the TlI–HgI₂ system were investigated by differential thermal analysis (DTA) and X-ray diffraction (XRD) methods. X-ray photoelectron spectra were measured for both pristine and Ar⁺ ion-bombarded Tl₄HgI₆ single crystal surfaces. The data reveal that the Tl₄HgI₆ single crystal is sensitive with respect to Ar⁺ ion-bombardment as 3.0 keV Ar⁺ irradiation over 5 min at an ion current density 14 μA/cm² induces changes to the elemental stoichiometry of the Tl₄HgI₆ surface, leading to a decrease of the mercury content in the topmost surface layers. X-ray photoelectron spectroscopy (XPS) measurements indicate very low hygroscopic nature of the Tl₄HgI₆ single crystal surface. The IR coherent bicolor laser treatment at wavelengths 10.6/5.3 μm has shown an occurrence of anisotropy at wavelengths 1540 nm of Er:glass laser. This may open the applications of Tl₄HgI₆ as a material for IR laser triggering. - Highlights: • Phase diagram of the HgI₂–TlI system was built. • Tl₄HgI₆ single crystals were grown by Bridgman Stockbarger method. • XRD, XPS analysis was done. • Ir induced anisotropy was established. • The compounds may be proposed as Ir laser operated polarizers.