Thickness-Dependent Structural and Electrical Properties of WS₂ Nanosheets Obtained via the ALD-Grown WO₃ Sulfurization Technique as a Channel Material for Field-Effect Transistors.

ABSTRACT: Ultrathin WS₂ films are promising functional materials for electronic and optoelectronic devices. Therefore, their synthesis over a large area, allowing control over their thickness and structure, is an essential task. In this work, we investigated the influence of atomic layer deposition (ALD)-grown WO₃ seed-film thickness on the structural and electrical properties of WS₂ nanosheets obtained via a sulfurization technique. Transmission electron microscopy indicated that the thinnest (1.9 nm) film contains rather big (up to 50 nm) WS₂ grains in the amorphous matrix. The signs of incomplete sulfurization, namely, oxysulfide phase presence, were found by X-ray photoemission spectroscopy analysis. The increase in the seed-film thickness of up to 4.7 nm resulted in a visible grain size decrease down to 15-20 nm, which was accompanied by defect suppression. The observed structural evolution affected the film resistivity, which was found to decrease from ∼10⁶ to 10³ (μΩ·cm) within the investigated thickness range. These results show that the thickness of the ALD-grown seed layer may strongly affect the resultant WS₂ structure and properties. Most valuably, it was shown that the growth of the thinnest WS₂ film (3-4 monolayers) is most challenging due to the amorphous intergrain phase formation, and further investigations focused on preventing the intergrain phase formation should be conducted.

SUBMITTER: Romanov RI 

PROVIDER: S-EPMC8697369 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature