Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C. This journal is © The Royal Society of Chemistry 2015
Electronic Supplementary Information (ESI)
Enhanced device performances of WSe2/MoS2 van der Waals junction p-n diode by fluoropolymer encapsulation
Pyo Jin Jeon,‡a Sung-Wook Min,‡a Jin Sung Kim,a Syed Raza Ali Raza,a Kyunghee Choi,a Hee Sung Lee,a Young Tack Lee,b Do Kyung Hwang,b Hyoung Joon Choi,a and Seongil Im*a
a
Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea. Fax:
82-2-392-1592; Tel:82-2-2123-2842; *E-mail:
[email protected]. b
Interface Control Research Center, Future Convergence Research Technology Division,
Korea Institute of Science and Technology (KIST), Hwarangno 14 gil 5, Seoul 136-791, Korea.
‡Pyo Jin Jeon and Sung-Wook Min contributed equally to this work.
Supplementary Information 1
(b) 10-4
Pristine Diode #1 10-5 Diode #2 -6 10 Diode #3 Diode #4 10-7
10-8 10-9 10-10 10-11 10-12 10-13 -30
-20
-10 0 10 20 Applied Voltage (V)
Current (A)
Current (A)
(a) 10-4
30
Al2O3 Encapsulation Diode #1 (Encap.) Diode #2 (Encap.)
10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 -30
-20
-10 0 10 20 Applied Voltage (V)
30
Fig. S1 The current-voltage curves of two sets of WSe2/MoS2 heterojunction p-n diode on SiO2/p+-Si. (a) Pristine 1, 2, 3, and 4 diodes show non-ideal bad I-V properties, and (b) the pristine diodes (1,2) gets more degraded with Al2O3 showing higher reverse current.
Current (A)
Supplementary Information 2 10-3 CYTOP Encapsulation 10-4 Diode #3 (Pristine) Diode #3 (Encap.) 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 -30 -20 -10 0 10 20 Applied Voltage (V)
30
Fig. S2 The current-voltage curves of another set of WSe2/MoS2 heterojunction p-n diode on SiO2/p+-Si. We performed this measurement to see the reproducibility of the effects of CYTOP encapsulation on property enhancement.
Supplementary Information 3
-4
(a) 10
WSe2 FET VDS=-1 V
-6
10-8 10-10 10-12 -14
10
-30
-6
10 Current (A)
Current (A)
10
-4 (b) 10
Pristine CYTOP Encapsulation
-20
-10 0 10 20 Applied Voltage (V)
MoS2 FET VDS=1 V
10-8 10-10 10-12
Pristine CYTOP Encapsulation
-14
30
10
-30
-20
-10 0 10 20 Applied Voltage (V)
30
Fig. S3 The current-voltage curves of another back gate (a) p-WSe2 and (b) n-MoS2 FETs on SiO2/p+-Si. We performed this measurement to see the reproducibility of the effects of CYTOP encapsulation on property enhancement (hole current increase in WSe2 but electron current decrease in MoS2 channel).
Supplementary Information 4
Fig. S4 Our p-n diode circuit in a schematic illustration (top) and an equivalent circuit diagram (bottom) where the parasitic capacitors (C1 and C2) are induced by the large overlapped area between electrodes (Pt, Ti) and heavily doped p+-Si substrate. Thus these capacitors are connected parallel with our p-n diode and also connected with the external resistor in series. In the initial short moment of any fast switching, some displacement current can be caused through the C1 and C2 overriding the current through the diode. As a result, overshoot/undershoot behavior can be observed during the dynamics using VA=±5 V.
Supplementary Information 5
Fig. S5 (a) Photo-induced I-V curves obtained from a pristine heterojunction p-n diode under R, G, and B LED lights. (The inset shows linear scale photo I-V curves in reverse bias regime.) Time dependent photocurrent responses (I-t) were also obtained at a reverse bias of VIN=-10 V, at light pulse frequencies of (b) 2 Hz. Response time was ~more than 60 ms (even at -10 V), which is three times slower than that of CYTOP-encapsulated device. This may indicate that the junction or surface trap density in CYTOP-encapsulated diode is much lower than that of pristine device as we discussed in the main text with Fig. 5 and 6.
Supplementary Information 6
Fig. S6 Aging degradation of CYTOP-capped 2D p-n diode was not found for more than 8 days in air ambient of 40% relative humidity at room temperature, which indicates that our encapsulated diode is very stable in ambient.
