Controllable Thermal Oxidation and Photoluminescence Enhancement in Quasi-1D van der Waals ZrS₃ Flakes

Abstract

In this study, we report on the thermal oxidation of few-layer ZrS 3 flakes as a function of temperature and heating time. We characterize the changes to the material crystal structure caused by the thermal treatment using atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and electrical transport measurements and link these results to the observed changes in optical contrast for on-substrate flakes. Importantly, we observe a very strong photoluminescence emission enhancement in the heated samples, with intensities comparable to those of direct-gap monolayer MoS 2 . We attribute this enhancement to mid-gap states in the thermally synthesized oxides of zirconium which form on the flake surface. We show that this emission is isotropic, unlike that of the untreated ZrS 3 , which unlocks an additional degree of freedom to the modulation of the optoelectronic properties of quasi-one-dimensional van der Waals materials.

Anisotropic Mechanics of 2D Materials

“…[66,67] This character endows the TMTCs feasibility to be mechanically exfoliated into 1D nanoribbon with expected atomic smooth edge. [157][158][159][160][161] It would provide a promising avenue for the construction of next-generation electronics based on nanoribbons, as the electronic structure of which can be precisely controlled benefiting from their atomic smooth edge structure.…”

Tunable Layer Orientation and Morphology in Vapor–Liquid–Solid Growth of One-Dimensional GeS van der Waals Nanostructures

“…Recently a particular class of semiconductor nanostructures has emerged1D nanowires of 2D van der Waals crystals, which combine the distinct structure of layered materials, i.e., covalent bonding within the layers and weak van der Waals bonding between them, and 1D confinement achieved in nanowires. This is distinct from efforts of separating quasi-1D nanostructures by exfoliation from bulk materials made possible by the presence of anisotropy in the crystal structure of transition-metal trichalcogenides such as TiS 3 , , TaSe 3 , , ZrSe 3 , NbS 3 , Sb 2 Se 3 , , Ta 2 Pd 3 Se 8 , as well as 1D nanostructures in which the van der Waals units represent true 1D chains (V 2 Se 9 , Nb 2 Se 9 , etc.). It is well established that nanowires of conventional 3D semiconductors grow with a preferred crystal orientation, e.g., with the symmetry axis along the [111] direction for Si and Ge nanowires .…”

Quasi-One-Dimensional ZrS3 Nanoflakes for Broadband and Polarized Photodetection with High Tuning Flexibility

“…The crystals can be easily exfoliated to obtain nanometer thick flakes as previously reported. 33,36 Figure 1c shows the optical image that contains one typical exfoliated flake, showing the same ribbon like geometry as bulk crystals, in consistence with the anisotropic nature of the crystal. Accordingly, the b (a) axis of the crystal can be identified to be parallel (perpendicular) to the long ribbon edge, as indicated by the arrows in the image.…”

“…ZrS 3 crystals were synthesized using the CVT process. 36 Briefly, high-purity zirconium (99.9%) and sulfur (99.9%) powders were mixed at a stoichiometric ratio of 1:3 and sealed in a quartz tube at high vacuum (<10 −4 Torr). The reaction was performed in a two-zone furnace, using iodine as the transport agent, with the hot zone maintained at 800 °C and the cold zone at 700 °C for 7 days.…”