No 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.

No abstract

electric properties, superconductors, semiconductors D 8000 -008Highly Textured Films of Layered Metal Disulfide 2H-WS2.-Title films consisting of up to 4 µm thick WS2 layers are prepared by solid state reaction of electron-beam evaporated WO3 with gaseous sulfur in the presence of H2 using substrates exhibiting comparable expansion coefficients. Best results are obtained at reaction temperatures in the range 973-1173 K with oriented sapphire substrates coated with a 5 nm thick Ni layer. Films oriented with their hexagonal basal plane parallel to the substrate exhibit a p-type conductivity of 0.1-3 Ω-1cm-1 and a room temperature lateral mobility of 105 cm2V-1s-1. With an exfoliated WS2 layer a photovoltage of 100 mV and a photocurrent of 5 mA/cm2 is obtained for the first time in an electrochemical cell. -(MATTHAEUS, A.; ENNAOUI, A.; FIECHTER, S.; TIEFENBACHER, S.; KIESEWETTER, T.; DIESNER, K.; SIEBER, I.; JAEGERMANN, W.; TSIRLINA, T.; TENNE, R.; J.

No abstract