Reasarch On The Lateral Photovoltaic Effect Of Amorphous WS₂ Thin Film

Tungsten disulfide?WS₂?is a semiconductor material with two-dimensional layered structure similar to graphene,which has good photoelectric properties.However,the size of single crystal WS₂ films prepared in the past is very small,which limits the large-scale application of WS₂-based thin film photoelectric devices.Amorphous WS₂?a-WS₂?film has the characteristics of simple preparation method,large area preparation and stable semiconductor property,so it is very suitable for semiconductor photoelectric devices.Amorphous WS₂ films were prepared on p-si and SiC substrates.The lateral photovoltaic properties of a-WS₂/p-si heterojunction in the visible region and the lateral photovoltaic properties of a-WS₂/SiC heterojunction in the ultraviolet region were studied.The main research contents of this paper are as follows:1.A-WS₂ films were prepared on p-si and 4h-sic substrates by pulsed laser deposition technology.By XRD,Raman and XPS tests,it is proved that high quality a-WS₂ films are obtained.The band gap widths of WS₂ thin film and 4H-SiC substrate are 1.35ev and 3.25ev respectively.The carrier mobility of heterojunction is measur ed by hall effect.Magnetron sputtering technique was used to gold plate electrode on a-WS₂ thin film surface.2.Study the lateral photovoltaic properties of a-WS₂/p-si heterojunction in the visible light range.The longitudinal voltammetry?I-V?curve indicates that the a-WS₂/p-si heterostructure forms an internal electric field.The open circuit voltage of260 mV was obtained by 635 nm laser irradiation.The longitudinal relaxation time of heterojunction is only 300 ns.A position sensitivity of up to 300 mV/mm was obtained under 780 nm laser irradiation.The factors affecting position sensitivity were further investigated and the reasons were analyzed.The transverse relaxation time of heterojunction was only 2.8?s.The transverse relaxation time of the heterojunction does not change with the change of the external shunt resistance.The transverse I-V curve indicates that the a-WS₂/p-si heterojunction interface forms a stable inverse layer structure,and the inverse layer can provide a fast diffusion channel for photogenerated carriers,which are mainly transmitted in the inverse layer.3.The lateral photovoltaic properties of a-WS₂/SiC heterojunction in the range of ultraviolet light were studied.The longitudinal I-V curve indicates that the a-WS₂/SiC heterojunction forms an internal electric field favorable for longitudi nal separation of photogenerated electron-hole pairs.The open circuit voltage of 330 mV was obtained under 266 nm laser irradiation.The longitudinal relaxation time of heterojunction is only 850 ns.In the study of a-WS₂/SiC heterojunction lateral pv,the position sensitivity of 190 mV/mm and 168 mV/mm on the side of a-WS₂ thin film and SiC substrate was obtained,and the lateral photovoltaic value did not reverse.The influence of film thickness on lateral photovoltaic properties was further investigated.Fast lateral relaxation time of 2.9?s was obtained in heterojunction.The transverse I-V curve indicates that carriers are mainly transported in a-WS₂ films.The fast relaxation time of heterojunction is explained by the principle of lateral photovoltaic generation.