  Two-dimensional (2D) layered semiconductors, with their ultimate atomic
thickness, have shown promise to scale down transistors for modern integrated
circuitry. However, the electrical contacts that connect these materials with
external bulky metals are usually unsatisfactory, which limits the transistor
performance. Recently, contacting 2D semiconductors using coplanar 2D
conductors has shown promise in reducing the problematic high resistance
contacts. However, many of these methods are not ideal for scaled production.
Here, we report on the large-scale, spatially controlled chemical assembly of
the integrated 2H-MoTe2 field-effect transistors (FETs) with coplanar metallic
1T' MoTe2 contacts via phase engineered approaches. We demonstrate that the
heterophase FETs exhibit ohmic contact behavior with low contact resistance,
resulting from the coplanar seamless contact between 2H and 1T' MoTe2 confirmed
by transmission electron microscopy characterizations. The average mobility of
the heterophase FETs was measured to be as high as 23 cm2 V-1 s-1 (comparable
with those of exfoliated single crystals), due to the large 2H MoTe2
single-crystalline domain (486{\mu}m). By developing a patterned growth method,
we realize the 1T' MoTe2 gated heterophase FET array whose components of
channel, gate, and contacts are all 2D materials. Finally, we transfer the
heterophase device array onto a flexible substrate and demonstrate the
near-infrared photoresponse with high photoresponsivity (~1.02 A/W). Our study
provides a basis for the large-scale application of phase-engineered coplanar
MoTe2 semiconductors-meter structure in advanced electronics and
optoelectronics.
