Investigating Ohmic contacts in PtSe2-based electronics

Transition metal dichalcogenides (TMDs) hold significant promise for next-generation electronic devices due to their unique electrical and structural properties. However, the performance of TMD-based devices is strongly influenced by the nature of the metal–semiconductor contacts. Achieving low-resistance, stable, and efficient contacts remains a key challenge and a crucial factor in fully realizing the potential of TMD materials in practical applications. In particular, platinum diselenide (PtSe₂) has emerged as a compelling candidate due to its tunable electronic properties and suitability for scalable synthesis. Advanced fabrication and precise contact engineering are key to minimizing interfacial degradation and maximizing device performance.

In this study, epitaxial PtSe₂ layers were synthesized on c-plane sapphire, providing an ideal platform for scalable device fabrication. PtSe₂-based electronic structures were fabricated by a two-resist lift-off technique combined with a one-zone chalcogenization approach.

We have focused on the systematical contact engineering investigation by evaluating nickel (Ni) and platinum (Pt) as source/drain electrodes. Electrical characterization showed a threefold reduction in Pt contact resistance as compared to Ni. Correlative scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDX) confirm that Pt diffuses toward the substrate without disrupting the PtSe₂ layers, whereas Ni induces severe top-layer degradation.

To investigate the impact of thickness on device performance, we gradually reduced the thickness of few-layer PtSe₂ in Transfer Length Method (TLM) structures with Pt/Au contacts. The films maintained continuous morphology and stable electrical behavior down to 1.5 nm, while further reduction led to increased surface roughness, void formation, and a notable rise in sheet and contact resistance.

These findings highlight the critical role of contact engineering and interface quality in preserving film integrity and optimizing device performance. Moreover, the results offer a scalable fabrication pathway for integrating PtSe₂ and related TMDs into high-performance electronic applications.