Contact interface properties are important in determining the performances of devices that are based on atomically thin two-dimensional(2D)materials,especially for those with short channels.Understanding the contact interface is therefore important to design better devices.Herein,we use scanning transmission electron microscopy,electron energy loss spectroscopy,and first-principles calculations to reveal the electronic structures within the metallic(1T')-semiconducting(2H)MoTe2 coplanar phase boundary across a wide spectral range and correlate its properties to atomic structures.We find that the 2H-MoTe2 excitonic peaks cross the phase boundary into the IT'phase within a range of approximately 150 nm.The 1T'-MoTe2 crystal field can penetrate the boundary and extend into the 2H phase by approximately two unit-cells.The plasmonic oscillations exhibit strong angle dependence,that is a red-shift of π+σ(approximately 0.3-1.2 eV)occurs within 4 nm at 1T'/2H-MoTe2 boundaries with large tilt angles,but there is no shift at zero-tilted boundaries.These atomic-scale measurements reveal the structure-property relationships of the 1T'/2H-MoTe2 boundary,providing useful information for phase boundary engineering and device development based on 2D materials.