Highly Textured Films of Layered Metal Disulfide 2H‐  WS 2 : Preparation and Optoelectronic Properties

Abstract

Highly textured films of 2H‐ WS2 can be obtained by sulfurization of up to 4 μm thick WO3 layers in the presence of hydrogen using amorphous (quartz glass, glassy carbon) or crystalline (sapphire, muscovite, highly oriented pyrolytic graphite) substrates. Best conditions have been found employing (00.1) oriented sapphire substrates with a 5 nm thick nickel layer interposed between substrate and oxide film (0.5 to 4 μm thickness) and a reaction temperature ranging from 973 to 1173 K. Depending on time the crystallites, oriented with their hexagonal basal planes parallel to the substrate, exhibited a lateral extension of up to 20 μm and a thickness of ⩽300 nm. Conductivity measurements of the films showed a p‐type conductivity in the range from 0.1 to 3 Ω−1 cm−1 and a lateral mobility as high as 105 cm2 V−1 s−1 at room temperature. The conductivity type has been confirmed by ultraviolet photoelectron and x‐ray photoelectron spectroscopy which were compared with n‐type single crystals. A freestanding film pealed off from a Pt coated quartz substrate and mounted on a brass holder was investigated photoelectrochemically. Using a 0.2 M Fe2+/Fe3+ redox electrolyte in 0.5 M H2SO4 an open‐circuit voltage of ≈100 mV and a short‐circuit current of 5 mA/cm2 has been detected for the first time.

Quantum spin Hall states in graphene interacting with WS2 or WSe2

“…19 and the references therein, as WS 2 is widely utilized for n/pdoped field effect transistors, for example. 20 Experimentally, synthesis and characterization of graphene on WS 2 have been reported in Ref. 4, claiming that a device based on this system can operate at room temperature with good current modulating capacity.…”

Reactive magnetron sputtering of tungsten disulfide (WS2−x) films: Influence of deposition parameters on texture, microstructure, and stoichiometry

“…[16][17][18][19] Often some kind of surfactant or crystallization promoter, such as sodium, nickel, or cobalt, was used to improve the crystallographic quality and hence the photosensitivity of these films. [19][20][21][22][23] Such promoters were investigated especially with respect to its ability to induce a pronounced ͑001͒-textured film growth, i.e., with the van der Waals planes parallel to the substrate surface. The role of nickel for the crystal growth promotion was demonstrated by Regula et al, 22 who showed that liquid NiS x droplets dissolve WS 2 and form a supersaturated solution for the liquid-phase growth of large ͑001͒-oriented WS 2 crystallites.…”

Ultrahigh power factors in P-type 1T-ZrX2 (X = S, Se) single layers

“…Inside TMDCs, the bondings are a combination of intralayer covalent-ionic bonds and the much weaker van der Waals interactions between intersandwiched layers [10]. Hence, because their structure is similar to that of graphite, TMDCs can potentially form a variety of low-dimensional structures, such as 1-D nanotubes [11,12] and 2-D graphene-like sheets [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

“…In the past decade, 2-D MX 2 layers have aroused broad interest because of their many promising applications in the fields of electronics [13][14][15], optoelectronics [16], thermoelectrics [17][18][19], ferroelectrics [20], photodetectors [24], and photocatalysis [25,26]. Except for Group VB dichalcogenides [14], most TMDC single layers are semiconductors, with sizable band gaps in the range of the visible or infrared light regime, making them promising candidates for solar cells [21].…”