Optimizing Transfer Processes and Strain Engineering for Scalable Fabrication of TMDs

Abstract

Thin-film semiconductors have been essential to modern technologies. But as devices become smaller and demand more power, traditional materials like silicon (Si) are no longer sufficient. Two-dimensional (2D) semiconductors, especially transition metal dichalcogenides (TMDs), are gaining interest. TMDs have a direct bandgap as monolayers, and past research shows that strain can shift this bandgap. Stacking TMDs also enables complex structures for advanced device applications. This work focuses on producing clean, intrinsic TMD films for 3D structures and introducing engineered strain. WS2 was grown, and various topographies were etched into SiO2. Two transfer methods were tested: traditional exfoliation and a cyclododecane-based approach. Raman spectroscopy, photoluminescence, SEM, and AFM were used to study the resulting devices. The CDD-based transfer showed higher yield and more consistent results than exfoliation. Drying the TMD before transfer reduced strain after placement on the patterned substrate. CDD was also tested to improve coupling between multiple layers of TMDs. While some transfers succeeded, reproducibility is still uncertain. CDD was further used to roll TMD flakes by placing it between the flakes and substrate. Future work will explore using CDD to fabricate suspended films and improve interfaces between stacked TMD layers.