Extrinsic p-type doping of few layered WS2 films with niobium by pulsed laser deposition

Abstract

Doping of few layered 2H WS2 films with Nb by pulsed laser deposition (PLD) using ablation targets fabricated from WS2, S and Nb powders is reported. The undoped controls were n-type, exhibited a Hall mobility of 0.4 cm2/Vs, and characterized by a Fermi level at 1.41 eV from the valence band edge. The latter was determined using ultraviolet photoelectron spectroscopy. Films doped at 0.5 and 1.1 atomic percentages niobium were p-type, and characterized by Fermi levels at 0.31 eV and 0.18 eV from the valence band edge. X-ray photoelectron spectroscopy indicates that Nb substitutes on W lattice sites. With increased Nb doping, the hole sheet concentration increased from 3.9 × 1012 to 8.6 × 1013 cm−2, while the mobility decreased from 7.2 to 2.6 cm2/Vs, presumably due to increased ionized impurity scattering. The approach demonstrates the potential of PLD for controlled doping of transition metal dichalcogenides.

Substitutional transition metal doping in MoS2: a first-principles study

“…Enhanced carrier concentrations have also been demonstrated with both Nbdoped and Re-doped WSe 2 [25]. Recently, pulsed laser deposition has been used to produce p-type Nb-doped WS 2 at concentrations of 0.5%-1.1%, which could allow for spatial control of doping concentrations [26]. These results suggest that transition metal doping is a viable method for production of p-n junctions, and thus, for device engineering.…”

Controllable Thin‐Film Approaches for Doping and Alloying Transition Metal Dichalcogenides Monolayers

“…Reproduced with permission. [ 106 ] Copyright 2018, AIP Publishing. c) Valence band edge of undoped WS 2 , and 0.5 and 1.1 at% Nb‐doped WS 2 film with respect to Fermi level indicates the Fermi level shifts toward the valance band edge with the increased Nb incorporation.…”

“…The XPS experiment confirmed the compositions in as-grown Nb doped WS 2 are close to stoichiometry, especially the improved W/S ratios due to the extra sulfur in the target (Figure 7b). [106] Ultraviolet photoemission spectroscopy was used to determine the Fermi level position from the valence band www.advancedsciencenews.com www.advancedscience.com (VB) edges of the undoped and doped films. The Fermi level of PLD-grown undoped WS 2 film is at 1.41 eV from its VB edge.…”

Efficient control of emission and carrier polarity in WS2 monolayer by indium doping

“…For instance, electron-donating sulfur vacancies in WS 2 and MoS 2 monolayers are often present in large quantities during growth, making these 2D TMDs heavily n-doped in nature and thus difficult to achieve p-type conductivity. Pulsed laser deposition has been employed to achieve p-type conductivity in Nb-doped WS 2 bulk crystal [23], while there are limited reports on the direct growth of p-type monolayer TMDs by chemical vapor deposition (CVD). CVD is popular for manufacturing 2D materials because of its high level for controllable growth and largescale production [24,25].…”