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

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

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

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

Characteristics of participants by nail selenium quartile groups.

<p>* Characteristics were described as mean ± SD or percentages.</p><p>Characteristics of participants by nail selenium quartile groups.</p

Multivariable-adjusted odds ratios for four types of dyslipidemia by nail selenium quartile groups.

<p>Model 1: Logistic regression model adjusted for age, gender and <i>APOEε</i>4 genotype. Age was classified into two groups, the cutoff value was 75. The reported parameter estimates were odds ratios. Model 2: Additionally adjusted for BMI, smoking, alcohol consumption, physical activity and medication use for cardiovascular diseases. BMI was classified into three groups, the cutoff values were 18.5 and 25.</p><p>Multivariable-adjusted odds ratios for four types of dyslipidemia by nail selenium quartile groups.</p

Rates of four types of dyslipidemia by <i>APOE</i> genotype and by nail selenium quartile groups.

<p>Rates of four types of dyslipidemia by <i>APOE</i> genotype and by nail selenium quartile groups.</p