| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 105 === Recently, two-dimension semiconducting transition metal dichalcogenides (TMDs) have attracted wide interest because of their potential applications in new electronic and optoelectronic devices. Monolayer TMD lateral heterojunctions have been demonstrated to exhibit p-n junction characteristics, which could be a fundamental building block for future atomically-thin electronics and optoelectronics. In this work, we first use atomic force microscopy (AFM) to measure the surface morphology of WSe2-MoSe2 heterostructures, demonstrating the monolayer structure. In addition, the boundary of WSe2-MoSe2 interface can be clearly identified by the phase mode. Besides the higher spatial resolution compared to optical microscopy (OM) images, the phase shift further demonstrates the different surface energies between WSe2 and MoSe2. Next, we have investigated the surface potential of the lateral heterojunction between monolayer WSe2 and MoSe2 by scanning Kelvin probe microscopy (SKPM). The monolayer WSe2-MoSe2 lateral heterojunctions were grown on sapphire substrates by chemical vapor deposition (CVD) and transferred onto highly oriented pyrolytic graphite (HOPG) substrates. We observed variations in surface potential of the heterojunction caused by the charge transfer between TMD and HOPG. SKPM mapping also resolves the depletion width of the lateral heterojunction. We found the measured band offset and depletion width for WSe2-MoSe2 lateral heterojunctions are in consistent with past literature reports.
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