Highly efficient water purification by WO3-based homo/heterojunction photocatalyst under visible light

Normally Off WSe2 Nanosheet-Based Field-Effect Transistors with Self-Aligned Contact Doping

“…38 The WO X layer makes the underlying WSe 2 electrondeficient via the charge transfer owing to its high electron affinity (electron affinity of WSe 2 : ∼3.7 eV, WO X : ∼5.3 eV). 39,40 The WO X layer can also act as the diffusion barrier that protects the underlying WSe 2 from ambient air or oxygen, improving air stability. 38 The use of the native oxide in WSe 2 is advantageous over other TMD semiconductors, which generally require plasma-enhanced chemical vapor deposition or atomic layer deposition to deposit the passivation layer, including Al 2 O 3 , SiO 2 , or SiN X .…”

Correlation between Thickness and Optical Properties in Nanocrystalline γ-Monoclinic WO3 Thin Films

“…The smaller optical indirect band gap obtained for the thinner 42 nm film could be attributed to two main aspects: (1) the presence of structural defects such as oxygen vacancies [60] and (2) the influence of crystallite size. Recent reports [61] suggest that the oxygen vacancies, in combination with W 5+ species, induce the formation of energy states within the forbidden band gap range. This condition results in the narrowing of the band gap [62].…”

Carrier Transport Properties in Few-Layer WS0.3Se1.7/(WOx)WS0.3Se1.7 Lateral p+–n Junctions Using a Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET) Structure

“…For several few-layer WS 0.3 Se 1.7 samples, the oxidized WO x layer was formed selectively in a specific area using a metal mask by plasma irradiation, followed by laser irradiation with oscillation wavelengths of 420, 532, and 650 nm (0.1 mW) for 60 s. The plasma treatment of the few-layer WS 0.3 Se 1.7 was performed between source and drain (S/D) electrodes with half the area of the 1 × 1 cm 2 sized device using atmospheric pressure O 2 /He plasma (or jet) excited by 10 kHz and 10 kV for 60 s and subsequent laser irradiation (spot diameter of approximately 4.0 mm). This treatment generated sulfur and selenium vacancies in the WS 0.3 Se 1.7 and promoted hole injection (chemical doping) from the high electron affinity (3.2–5.3 eV) top oxidized layer of WO x to the lower few-layer pristine WS 0.3 Se 1.7 . − Finally, gold and platinum electrodes were used to straddle the p + –n junction interface. Platinum and gold electrodes with ∼5.0 mm length ( L av ) and ∼0.45 mm width ( W av ) were formed in the (WO x )­WS 0.3 Se 1.7 and WS 0.3 Se 1.7 regions, respectively, as S/D electrodes with a distance ( d av ) of ∼0.85 mm using UV photolithography, sputtering, and standard lift-off process.…”

“…Although atomically thin TMDC-based van der Waals (vdW) p – n junctions facilitate area-effective light absorption and exciton separation, they suffer from low efficiency owing to complex processing, such as accurate alignment and localization on a flake during device fabrication, multitransfer technology, and critical recombination. − Contrastingly, in-plane (lateral) p – n junctions enable spatial modulations of optoelectronic properties, facilitating the fabrication of atomically thin and tunable subnanometer TMDCs-based device architectures . In addition, sharp in-plane homojunctions can be fabricated by locally tuning the photoelectronic properties of few-layer TMDCs with WO 3 and MoO 3 , where transition-metal oxide layers such as WO 3 and MoO 3 (with high electron affinities in the range of 3.2–6.7 eV) promote the injection of charges (holes) into the valence band as well as reduce the barrier height of metal contact–semiconductor interface. − Additionally, light-trapping structures including back reflectors, metal texturing, Fabry–Perot cavity using dielectric mirrors, and antireflection (AR) layer as used in conventional Si-based p–n and p–i–n junctions are critical for increasing light absorption in thin lateral junction optoelectronic devices. ,,− A strong light-trapping structure can significantly enhance photoresponsivity and speed reducing reflection in atomically thin and few-layer photonic devices. − …”