Large-scale vertical 1T′/2H MoTe₂ nanosheet-based heterostructures for low contact resistance transistors

Because of atomic thickness and non-zero band gap, two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have become promising candidates for post-silicon nanoelectronic materials. In the process of realizing 2D electronic devices for scaling down modern integrated circuitry, contact engineering suitable for large-scale manufacturing is crucial, but it remains elusive. Here, we demonstrated the large-scale chemical assembly of van der Waals heterostructures, with metallic 1T′-MoTe₂ on top of semiconducting 2H-MoTe₂, via a spatial-controlled phase-engineered growth method. Based on the heterophase structure, a large-scale field-effect transistor (FET) array was fabricated, in which 1T′-MoTe₂ was used as the contact electrode and 2H-MoTe₂ was used as the semiconducting channel. The vertical nanosheet-based heterophase FET exhibits ohmic contact behavior with distinctively low contact resistance. A total of 120 FETs were measured, and the measured average field-effect mobility was as high as 15 cm² V⁻¹ s⁻¹ (comparable to that of exfoliated single-crystalline 2H-MoTe₂). The superior electrical properties are attributed to the atomic clean interface that leads to an ideal contact between top 1T′- and bottom 2H-MoTe_2. This spatially controlled large-scale chemical assembly of vertical 2D metal− semiconductor heterostructures with low contact resistance provides a new route toward the practical application of high-performance electronic and optoelectronic devices based on the atomically thin TMDCs.