WSe2 Lateral Heterostructure

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UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and. Technology (UNIST), Ulsan 44919, South Korea. * E-mail: ...
Supporting Information Growth and Simultaneous Valleys Manipulation of Two-Dimensional MoSe2WSe2 Lateral Heterostructure Farman Ullah,† Yumin Sim,‡ Chinh Tam Le,† Maeng-Je Seong, ‡ Joon I. Jang,*,§ Sonny H. Rhim,† Bien Cuong Tran Khac,¶ Koo-Hyun Chung,¶ Kibog Park,∥Yangjin Lee,# Kwanpyo Kim,# Hu Young Jeong,& and Yong Soo Kim*,† †

Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan

44610, South Korea ‡

Department of Physics, Chung-Ang University, Seoul 06794, South Korea

§

Department of Physics, Sogang University, Seoul 04107, South Korea



School of Mechanical Engineering, University of Ulsan, Ulsan 44610, South Korea



Department of Physics and School of Electrical and Computer Engineering, Ulsan National

Institute of Science and Technology(UNIST), Ulsan 44919, South Korea #

Department of Physics, Ulsan National Institute of Science and Technology(UNIST), Ulsan

44919, South Korea &

UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and

Technology (UNIST), Ulsan 44919, South Korea

* E-mail: [email protected] (J. I. Jang) and [email protected] (Y. S. Kim)

S1 OM images of lateral and vertical heterostructures

Figure S1. OM images of in-plane MoSe2–WSe2 lateral and vertical heterostructures grown by the pulsed-laser-deposition-assisted method. (a) Isolated flakes, (b) continuous film-like lateral HSs, and (c-d) irregular vertical HSs locally formed over the lateral HS flakes.

S2 Experimental setup for polarization-sensitive PL measurements The 633nm line from a He-Ne laser was used as an excitation source for the polarizationresolved photoluminescence (PL) measurements. The right (left) circularly polarized light, marked as σ+ (σ-) was focused onto the sample, using a ×50 objective lens , located in a cryostat, held at temperatures below 50K. The laser beam area on the sample was ~1µm2. Either σ+ or σpolarized PL was selected and measured using a single-grating spectrometer with a focal length

of 50 cm coupled to a liquid-nitrogen-cooled charge-couple device (CCD) detector. The linearly polarized incident light was reflected by a beam splitter and then passed through a quarter-wave plate, resulting in the circularly polarized light σ+ (σ-), as shown in Fig. S2. The PL signal went through the same quarter-wave plate. Either σ+ or σ- polarized PL was selected by setting the linear polarizer #2 to either vertical or horizontal direction, respectively. In order to make sure that the linearly polarized light entering the spectrometer is the same polarization direction for both σ+ and σ- polarized PL, we changed the half-wave plate setting appropriately; this is required because the efficiency of the detection system itself has some polarization dependence.

Figure S2. Schematic illustration of the experimental setup for polarization-resolved PL measurements

S3 Room-temperature valley polarization

Figure S3. Polarization-sensitive PL measurements on pristine MoSe2, WSe2 and the interface MoSe2-WSe2 regions of the lateral HS at room temperature, signifying no essential valley polarization.