Transport properties of fullerene‐like WS₂ nanoparticles

Abstract

Electrical resistivity and Hall effect measurements of pellets compacted from fullerene-like WS 2 nanoparticles (IF-WS 2 ) and bulk 2H-WS 2 powder were carried out using the van der Pauw method over a wide temperature range. In addition IF-WS 2 pellets were annealed at elevated temperatures under vacuum in a specially designed system. Arrhenius plots for the conductivities of the WS 2 samples (2H, IF and IF+annealing) exhibit marked uprise of ∂ ln (s T -1 )/∂T -1 with temperature. The resistivity of the nonannealed IF-WS 2 pellets is higher by 2 -8 orders of magnitude than that of 2H-WS 2 pellets, whereas the resistivity of the annealed IF pellets is higher than that of the non-annealed ones. Hall Effect measurements at 300 K show p-type conductivity and similar carrier concentration for both types of materials. The carrier mobility of 2H-WS 2 platelets is found to be in the range of the reported values. However, IF-WS 2 pellets have shown an unusually low mobility for a semiconducting material. The experimental data was found to be in a good agreement with a model used for analyzing the conductivity of polycrystalline semiconductors, which takes into consideration fluctuations of the barrier heights among the different nanoparticles as well as within a single nanoparticle boundary.

X‐ray photoelectron spectroscopy and tribology studies of annealed fullerene‐like WS2 nanoparticles

“…3 Results and discussion 3.1 XPS Figure 1 The tungsten and sulphur line shifts towards higher energies are in agreement with the previous DC electrical measurements [14], where the resistivity of the pristine IF samples was found to be higher than that of the 2H-WS 2 ones, and furthermore the annealed IF samples had higher resistivity than the non-annealed ones. Four probe electrical measurements on IF pellets [14] showed that after the annealing there was a marked increase in the DC resistivity: at 298 K ρ (annealed) = 912 Ω cm, while ρ (pristine) = 346 Ω cm.…”

“…Four probe electrical measurements on IF pellets [14] showed that after the annealing there was a marked increase in the DC resistivity: at 298 K ρ (annealed) = 912 Ω cm, while ρ (pristine) = 346 Ω cm. The chemically resolved electrical measurements (CREM) revealed that under a current of 50 nA of the electron flood gun, the induced potential increased from 10 mV for the non-annealed sample to 140 mV for the annealed one, indicating that the annealed sample was more resistive than the pristine sample.…”

“…A dedicated vacuum-annealing set-up was assembled in order to extract the remnant water molecules produced during the synthesis or adsorbed onto the nanoparticles surface afterwards. Sequential van der Pauw transport measurements [14] of the IF-WS 2 pellets showed that the vacuum annealed samples demonstrated higher resistivity than the non-annealed ones. A systematic X-ray photoelectron spectroscopy (XPS) study of the IF-MX 2 structures, apart from preliminary experiments [15], was not carried out so far.…”

Controlled Doping of MS2 (M=W, Mo) Nanotubes and Fullerene‐like Nanoparticles

“…[9] For all the IF/ INT the resistivity increases with decreasing temperatures, which reflects their semiconductor behavior. Nonetheless, the doping of the IF and INT leads to a remarkable drop in their resistivity as compared to the undoped NP.…”

New Deposition Technique for Metal Films Containing Inorganic Fullerene‐Like (IF) Nanoparticles

“…Initially the films contained substantial amounts of titanium oxide in the form of Ti 2 O. The inadvertent oxidation of the Ti film is likely to emanate from either inadequate purging of the vacuum chamber, or from residual water which was adsorbed to the IF nanoparticles [7] and reacted with the hot Ti atoms, or from the native SiO 2 film covering the Si substrate. Both Ti (PDF-4 + 2011 #5-0682; space group P-3m1 (164)) and Ti 2 O (PDF-4 + 2011 #97-002-3574; space group P63/mmc (194)) films are crystalline (hexagonal) with predominantly [001] orientation of the crystallites.…”