Lewis acid-doped transition metal dichalcogenides for ultraviolet–visible photodetectors

Ultraviolet photodetectors(UV PDs)are widely used in civilian,scientific,and military fields due to their high sensitivity and low false alarm rates.We present a temperature-dependent Lewis acid p-type doping method for transition metal dichalcogenides(TMDs),which can effectively be used to extend the optical response range.The p-type doping based on surface charge transfer involves the chemical adsorption of the Lewis acid SnCl_(4)as a light absorption layer on the surface of WS_(2),significantly enhancing its UV photodetection performance.Under 365 nm laser irradiation,WS_(2)PDs exhibit response speed of 24 ms/20 ms,responsivity of 660 mA/W,detectivity of 3.3×10^(11)Jones,and external quantum efficiency of 226%.Moreover,we successfully apply this doping method to other TMDs materials(such as MoS_(2),MoSe_(2),and WSe_(2))and fabricate WS_(2) lateral p–n heterojunction PDs.

Spatially selective p-type doping for constructing lateral WS_(2) p-n homojunction via low-energy nitrogen ion implantation

The construction of lateral p-n junctions is very important and challenging in two-dimensional(2D)semiconductor manufacturing process.Previous researches have demonstrated that vertical p-n junction can be prepared simply by vertical stacking of 2D materials.However,interface pollution and large area scalability are challenges that are difficult to overcome with vertical stacking technology.Constructing 2D lateral p-n homojunction is an effective strategy to address these issues.Spatially selective p-type doping of 2D semiconductors is expected to construct lateral p-n homojunction.In this work,we have developed a low-energy ion implantation system that reduces the implanted energy to 300 eV.Low-energy implantation can form a shallow implantation depth,which is more suitable for modulating the electrical and optical properties of 2D materials.Hence,we utilize low-energy ion implantation to directly dope nitrogen ions into few-layer WS_(2) and successfully realize a precise regulation for WS_(2) with its conductivity type transforming from n-type to bipolar or even p-type conduction.Furthermore,the universality of this method is demonstrated by extending it to other 2D semiconductors,including WSe_(2),SnS_(2) and MoS_(2).Based on this method,a lateral WS_(2) p-n homojunction is fabricated,which exhibits significant rectification characteristics.A photodetector based on p-n junction with photovoltaic effect is also prepared,and the open circuit voltage can reach to 0.39 V.This work provides an effective way for controllable doping of 2D semiconductors.