Improved Reliability of 2D-TMDC Dry Transfer via PMMA and Target Substrate Treatments

Abstract

A reliable and scalable transfer of 2D-TMDCs (two-dimensional transition metal dichalcogenides) from the growth substrate to a target substrate with a high reproducibility and yield is a crucial step for device integration. In this work, we introduced a scalable dry-transfer approach for 2D-TMDCs grown by MOCVD (metal–organic chemical vapor deposition) on sapphire. Transfer to a silicon/silicon dioxide (Si/SiO₂) substrate is performed using PMMA (poly(methyl methacrylate)) and TRT (thermal release tape) as sacrificial layer and carrier, respectively. Our proposed method ensures a reproducible peel-off from the growth substrate and better preservation of the 2D-TMDC during PMMA removal in solvent without compromising its adhesion to the target substrate. This is achieved through a PMMA plasma treatment, which mitigates stress release during solvent exposure, and target substrate prewetting enhancing the interfacial adhesion between the 2D material and the target substrate. A comprehensive comparison between the dry method introduced in this work and a standard wet transfer based on potassium hydroxide (KOH) solution shows improvement in terms of cleanliness and structural integrity for the dry-transferred layer, as evidenced by X-ray photoemission and Raman spectroscopy, respectively. Moreover, fabricated field-effect transistors (FETs) demonstrate improvements in subthreshold slope, maximum drain current, and device-to-device variability. The dry-transfer method developed in this work enables large-area integration of 2D-TMDC layers into (opto)electronic components with high reproducibility while better preserving the as-grown properties of the layers.