Surface-Energy-Assisted Perfect Transfer of Centimeter-Scale Monolayer and Few-Layer MoS₂ Films onto Arbitrary Substrates

Abstract

The transfer of synthesized 2D MoS2 films is important for fundamental and applied research. However, it is problematic to translate the well-established transfer processes for graphene to MoS2 due to different growth mechanisms and surface properties. Here we demonstrate a surface-energy-assisted process that can perfectly transfer centimeter-scale monolayer and few-layer MoS2 films from original growth substrates onto arbitrary substrates with no observable wrinkles, cracks, and polymer residues. The unique strategies used in this process include leveraging the penetration of water between hydrophobic MoS2 films and hydrophilic growth substrates to lift off the films and dry transferring the film after the lift off. This is in stark contrast with the previous transfer process for synthesized MoS2 films, which explores the etching of the growth substrate by hot base solutions to lift off the films. Our transfer process can effectively eliminate the mechanical force caused by bubble generations, the attacks from chemical etchants, and the capillary force induced when transferring the film outside solutions as in the previous transfer process, which consists of the major causes for the previous unsatisfactory transfer. Our transfer process also benefits from using polystyrene (PS), instead of poly(methyl methacrylate) (PMMA) that was widely used previously, as the carrier polymer. PS can form more intimate interaction with MoS2 films than PMMA and is important for maintaining the integrity of the film during the transfer process. This surface-energy-assisted approach can be generally applied to the transfer of other 2D materials, such as WS2.

Top‐Down Integration of Molybdenum Disulfide Transistors with Wafer‐Scale Uniformity and Layer Controllability

“…Table S1 (Supporting Information) compares the elec tron mobility and On/Off current ratio between our ALD based MoS 2 device and previously reported MoS 2 FETs. The mobility of our 4L MoS 2 are comparable or even higher than those of previously reported CVD samples on SiO 2 /Si with a SiO 2 gate oxide or on sapphire substrate, [14,22,23,33,36,37] and is highest among all the published ALD based MoS 2 device research. [5,6] …”

“…The extracted mobility is much higher than the previously reported value for a CVD MoS 2 FET (≈0.12 cm 2 V −1 s −1 ). [22] The On/Off current ratio was 10 4 , which is sufficient large for electronic device applications. Figure 3c depicts the linear I d -V ds char acteristics at small V ds level, indicating good Ohmic contacts at source/drain and absence of significant charge injec tion barriers at room temperature.…”

“…Based on the transfer free and top down fabrication process, the electrical performance of the MoS 2 top gated transistors are comparable to the previously reported monolayer and few layer CVD MoS 2 FET devices. [22,23] …”

In Situ Monitoring of the Thermal-Annealing Effect in a Monolayer of MoS2

“…31 The astransferred film exhibits weak bonding with the substrate. 5 Figure 1a shows the optical image of a transferred MoS2 film on which spatially resolved Raman and PL measurements were performed in a marked area of 20 μm × 20 μm.…”

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…CVD‐grown graphene has made great breakthrough in the growth of large‐area graphene 17, 155, 156, 157, 158, 159, 160. Recently, the synthesis of 2DLMs via CVD methods has been illustrated in many reports especially for MoS 2 ,30, 31, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185 which also shows promising applications in electronics and optoelectronics. Up to now, there are several reports on synthesizing 2D GIVMCs nanoflakes via CVD method, which is still at the initial stage.…”