Alla Zak - Video Lecture

Alla Zak - Video Lecture

IVS-IPSTA 2020 Online Conference December 13, 2020

Nanomaterials, Thin films, and Surface Science
Morning Session

Session chair:
David Zitoun

Bar-Ilan University


Synthetic Route Towards Pure Phase of WS2 & MoS2 Inorganic Nanotubes and their Unusual Properties

Alla Zak

Faculty of Sciences, HIT Holon Institute of Technology, Israel


Abstract


Inorganic nanotubes (INTs) of WS2 and MoS2 demonstrate unique properties due to their nanosize, closed-cage arrangement of the layers into chiral tubes and mechanical strength. An advance in extremely complicated synthesis of INT-MoS2 by vapor-gas-solid reaction of Mo oxides with H2/H2S gases will be presented. Recent discovery of bulk photovoltaic effect (BPVE) in INT-WS2 will be discussed. The photocurrent in the nanotube-based device was orders of magnitude larger than in other BPVE materials. The BPVE does not require p–n junctions of traditional PVE for generation of electric current, and occurs due to the intrinsic properties of INT-WS2: small band gap (1.4-2.1 eV), broken inversion symmetry and polar structure. This progress is particularly important for environmentally benign energy harvesting because the efficiency of PVE has been almost reached the theoretical limit. An exponential increase of the resistivity with tensile strain was demonstrated up to a recorded elongation of 16%, thereby making WS2 NTs suitable for piezoresistive sensor applications. Low temperature CL of single-wall few nm diameter WS2 nanotubes, produced by high-power plasma irradiation of multiwall WS2 INTs, demonstrates blue shift, evidencing quantum confinement and strain effect.