Supporting Information

Transcription

1 Supporting Information High-Performance MoS 2 /CuO Nanosheet-on-1D Heterojunction Photodetectors Doo-Seung Um, Youngsu Lee, Seongdong Lim, Seungyoung Park, Hochan Lee, and Hyunhyub Ko * School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan , Korea hyunhko@unist.ac.kr S-1

2 Table S1. Comparison of electrical and optical performances of MoS 2 -based photodetectors. Type Rectification Ratio Dark Current Photoresponsivity Photoresponse Speed Ref. MoS 2 /CuO (PN a ) ±2 V ~38 -2 V ~ nm 34.6 ms (R b ) / 51.9 ms (F c ) This work Single Layer MoS 2 (MSM d ) nm & 50 V G 50 ms (R) / 50ms (F) 1 Monolayer MoS 2 (MSM) - 2 pa nm 4 s (R) / 0.6 s (F) 2 Multi-layer MoS 2 (MSM) - 1 V nm - 3 MoS 2 HJ by thickness modulation (PN) - ~5 1 V & 30 V G nm - 4 MoS 2 /n-si (NN e ) - ~ 20 pa nm - 5 Bulk MoS 2 /p-si (PN) ±0.5 V ms (R) / 40 ms(f) 6 MoS 2 /BP (PN) nm & 40 V G - 7 MoS 2 /ReSe 2 (PN) nm > 40 s 8 a PN: PN junction photodiode; b R: rise time; c F: falling time (decay time); d MSM: metal-semiconductor-metal photodetector; e NN: NN junction photodiode. S-2

3 Figure S1. a) and b) Tilted-view and c) and d) top-view SEM images of vertically grown CuO nanowires. S-3

4 Figure S2. Schematic illustration of wet-transfer printing process for the transfer-printing of MoS 2 nanosheet on top of CuO nanowire. S-4

5 Figure S3. Encapsulation of CuO NW with MoS 2 nanosheet during the wet-transfer process of MoS 2 nanosheet onto CuO nanowire. a) the exfoliated MoS 2 sheet on the PDMS stamp is covered on top of the CuO NWs/Si substrate. b) Conformal contact between the MoS 2 nanosheet and the CuO NW on Si substrate due to the liquid evaporation. c) As the liquid further evaporates, the MoS 2 sheets uniformly encapsulate the cylindrical CuO NW on the Si substrate, resulting in the tight bonding interface between MoS 2 and CuO NW. S-5

6 Figure S4. Magnified a) SEM and b) AFM images of CuO NW covered with MoS 2 nanosheet after the wet-transfer of MoS 2 nanosheet onto the CuO NW. The inset AFM analysis indicates the thickness of MoS 2 nanosheet. S-6

7 Figure S5. Raman spectra of the transferred MoS 2 nanosheet showing two distinctive peaks of MoS 2 for in-plane E 1 2g (382.9 cm -1 ) and out-of-plane A 1g (408.4 cm -1 ) vibration modes. The spacing of ~25.5 cm -1 between E 1 2g and A 1g modes, which indicates the multilayer structure of transferred MoS 2 nanosheet. S-7

8 Figure S6. Band diagrams of the MoS 2 /CuO NW heterojunction p-n diode a) before and b) after the contact between MoS 2 nanosheet and CuO nanowire. c) Band diagram under the reverse bias of heterojunction p-n diode. When the light is illuminated, the electron-hole pair is generated from the MoS 2 /CuO interface region. S-8

9 Figure S7. a, b) SEM images of photodiode based on the heterojunction of CuO NW above the MoS 2 nanosheet (CuO/MoS 2 1D-on-nanosheet heterojunction). S-9

10 Figure S8. The light absorption area of MoS 2 /CuO nanosheet-on-1d heterojunction photodetectors. The absorption area is defined as the junction area between CuO NW and MoS 2 nanosheet, which can be obtained by multiplying the arc length (l arc ) and the length of junction between CuO NW and MoS 2 nanosheet (l nanowire ). S-10

11 a) b) c) Anode current (na) MoS 2 /CuO Heterojunction Dark current Photocurrent Anode voltage (V) Anode current (na) CuO MSM Anode voltage (V) Dark current Photocurrent Anode current (na) MoS 2 MSM Dark current Photocurrent Anode voltage (V) Figure S9. Dark and photocurrent comparison of a) MoS 2 sheet/cuo nanowire heterojunction p- n diode, b) CuO MSM photodetector, and c) MoS 2 MSM photodetector in dark state and under the 570 nm LED light. S-11

12 Figure S10. Photo-switching behavior of a) CuO MSM photodetector and b) MoS 2 MSM photodetector under the pulsed 570 nm LED light. S-12

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