In‐plane epitaxial growth of 2D CoSe‐WSe2 metal‐semiconductor lateral heterostructures with improved WSe2 transistors performance

The two‐dimensional (2D) in‐plane (lateral) heterostructures have attracted increasing interest for potential applications in the atomically thin electronics and optoelectronics. While most studies focus on semiconductor‐semiconductor lateral heterostructures with highly similar lattice structures between the constituent components, the synthesis of metal‐semiconductor lateral heterostructures is much less explored and usually more challenging due to more distinct lattice structures or chemical properties. Herein, a vapor phase epitaxy growth method of high‐quality metal‐semiconductor lateral heterostructures between tetragonal CoSe and hexagonal WSe2 is reported. The 2D CoSe can selectively nucleate at the edge of pre‐grown WSe2 nanosheets to form CoSe‐WSe2 metal‐semiconductor lateral heterostructures. Optical microscopy (OM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) studies reveal distinct contrast across the heterostructure interface. High‐resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) studies further confirm the microstructure modulation across the heterostructure interface. The field‐effect transistors (FETs) of CoSe‐WSe2 lateral heterostructures show satisfactory Ohmic contacts and considerably better FET performance over those with deposited Cr/Au contacts, suggesting the in‐plane metal‐semiconductor junctions may function as improved contacts for the atomically thin electronics. A two‐step growth approach for controllable synthesis of CoSe‐WSe2 lateral heterostructures on the SiO2/Si substrates by adjusting growth temperature is reported. HRTEM studies reveal a clear distinct interface between CoSe and WSe2. Electrical transport studies show that CoSe‐WSe2 lateral heterostructures show satisfactory Ohmic contacts and considerably higher device performance, suggesting the in‐plane metal‐semiconductor junction may function as improved contacts for the atomically thin transistors.