High Photoresponsivity in Ultrathin 2D Lateral Graphene:WS₂:Graphene Photodetectors Using Direct CVD Growth

Abstract

We show that reducing the degree of van der Waals overlapping in all 2D ultrathin lateral devices composed of graphene:WS2:graphene leads to significant increase in photodetector responsivity. This is achieved by directly growing WS2 using chemical vapor deposition (CVD) in prepatterned graphene gaps to create epitaxial interfaces. Direct-CVD-grown graphene:WS2:graphene lateral photodetecting transistors exhibit high photoresponsivities reaching 121 A/W under 2.7 × 105 mW/cm2 532 nm illumination, which is around 2 orders of magnitude higher than similar devices made by the layer-by-layer transfer method. The photoresponsivity of our direct-CVD-grown device shows negative correlation with illumination power under different gate voltages, which is different from similar devices made by the transfer method. We show that the high photoresponsivity is due to the lowering of effective Schottky barrier height by improving the contact between graphene and WS2. Furthermore, the direct CVD growth reduces overlapping sections of WS2:Gr and leads to more uniform lateral systems. This approach provides insights into scalable manufacturing of high-quality 2D lateral electronic and optoelectronic devices.

Recent Advances in 2D Lateral Heterostructures

“…The optoelectronic properties of lateral heterostructure devices have been investigated intensively. Some optoelectronic devices exhibit superior optical performance [127][128][129][130]. In lateral graphene-TMDC heterostructures, photons excite electron-hole pairs from the TMDC and rapidly transfer the electrons to the graphene in the Schottky junction, which provides a good photoresponse property.…”

Heterostructures formed through abraded van der Waals materials

“…This is supported by comparing in and out of plane resistivities of our TMDC films with bulk, exfoliated and LPE crystals. We quantitatively find that our TMDC films display similar resistivity to exfoliated 48,66 , CVD 67 or bulk 68 materials, while LPE films display resistivities several orders of magnitude higher than our devices 5,37,38 , see Supplementary Table 3.…”

Metallic 1T Phase Tungsten Disulfide Microflowers for Trace Level Detection of Hg2+ Ions

“…[ 13 ] WS 2 is one of the emerging TMDs, where W layers are sandwiched between two atomic layers of S to form S–W–S structures. [ 14 ] To date, WS 2 has been synthesized using several methods including mechanical exfoliation, [ 15 ] atomic layer deposition, [ 16 ] chemical vapor deposition, [ 17 ] solvothermal, [ 18 ] lithium‐based intercalation, [ 19 ] electrochemical depositions, [ 20 ] and hydrothermal synthesis. [ 14 ] Likewise, various morphologies of WS 2 such as nanoribbons, [ 41 ] nanoflakes, [ 19 ] nanosheets, [ 21,35 ] and nanospheres [ 22 ] have been synthesized.…”