Supporting Information
Functionalized Graphitic Carbon Nitride for Metal-free, Flexible and Rewritable
Nonvolatile Memory Device via Direct Laser-Writing
Fei Zhao, Huhu Cheng, Yue Hu, Long Song, Zhipan Zhang, Lan Jiang, and Liangti
Qu*
Fitting Model and Method.
To examine the carrier transport in the fabricated rGO/g-C3N4-NSs/rGO device,
the current-voltage curve was analyzed by four basic mechanisms which are shown
below:
Thermionic emission, Equation S1,
Trapped-charge-limited current (TCLC), Equation S2,
Space-charge-limited current (SCLC), Equation S3,
Fowler–Nordheim
tunneling current (FNTC), Equation S4,
where I and V are the device current and applied voltage, respectively; n and nt are the
free carrier concentration and the concentration of trapped charge, respectively; A, T,
k, 𝜙 , q, d, 𝜟Eae ,π and 𝜀 are the Richardson constant, temperature, Boltzmann
constant, Schottky energy barrier, electron charge, thickness of active layer, the
activation energy of electron, ratio of circumference to diameter and electric constant,
respectively.
If the charges are tunneling through a triangular barrier at the oxygen partition as we
expected, the constant Kd in Equation S2 is given by Equation S5:
Where theφis the barrier height and m* is the effective mass of the electrons,
indicating that the value of Kd is proportional with barrier height.
Figure S1. TEM images of (A) bulk g-C3N4, (B) intercalated g-C3N4 and (C)
exfoliated g-C3N4 with size of about 200 nm, 80 nm and 40 nm, respectively. SAED
patten of (D) bulk g-C3N4, (E) intercalated g-C3N4 and (F) exfoliated g-C3N4.
Figure S2. AFM images and the height profile along the lines of the (A) bulk g-C3N4,
(B) intercalated g-C3N4 and (C) exfoliated g-C3N4 with thickness of about 100 nm,
4 nm and 0.4 nm, respectively.
Figure S3. High resolution XPS of (A) C 1s, (B) N 1s, (C) O 1s and (D) S 2p. The N
1s and O1s spectra were deconvoluted into Gaussian–Lorenzian peaks corresponding
to N=C (398.5 eV), N-C (399.8 eV), HN-C (401.0 eV) and O=C (531.6 eV), O-C
(532.3 eV), O-S (534.0 eV),[S1] matching the intrinsic structure of g-C3N4 and
verifying the oxygen functional groups, respectively. In addition, the high resolution S
2p confirmed the absence of S-C bonds (163.9 eV).[S2]
Figure S4. The (ahv)2 versus photon-energy plots of bulk g-C3N4 and g-C3N4-NSs.
Figure S5. Photograph of the preparation of GO film (accordingly to Figure 2A, 2).
The liquid membrane of GO aqueous solution was held with a ring of stannum wire.
The diameter of the ring is about 2 cm. With the evaporation of water, the liquid
membrane will transform to a dried GO film.
Figure S6. AFM image of the as-prepared GO film on PET substrate.
Figure S7. AFM images of (A) rGO sheet and (B) g-C3N4-NSs coated on GO after
laser irradiation flatted on the Si substrate. A 30 nm increase of thickness was
observed.
Figure S8. C 1s XPS peaks of initial GO and laser induced rGO film
Figure S9. C 1s XPS peaks of g-C3N4-NSs after laser irradiation
Figure S10.
Photographs of the repeated extending (A) and bending (B) states of
rGO/g-C3N4-NSs/rGO on PET substrate with a bending radius of 8 mm. Scale bars: 2
cm.
Figure S11. Experimental data with fitted lines of the I-V characteristics in
thermionic emission model.
Figure S12. Experimental data and fitted lines of the I-V characteristics in three linear
relation region. The plots of ln (I) vs. ln (V) with slopes of 0.99 and 1.96 in the
voltage range -0.71 to -1.76 V and -1.76 to -4.35 V were fitted with
trapped-charge-limited current model (TCLC, Equation S2) and space-charge-limited
current model (SCLC, Equation S3), respectively.
Figure S13. Experimental data with fitted lines of the I-V characteristics in F-N
tunneling model.
Figure S14. (A) and (B) Schematic illustration of the fabrication of patterned
rGO/g-C3N4-NSs (1) and rGO (2) by laser irradiation on GO films, respectively. (C)
is the assembly process of crossbar devices (D).
Figure S15. The I-V characteristics of the g-C3N4-NSs based crossbar memory
device.
Figure S16. The I-V characteristics of the memory device in controlled experiment,
i.e. with a structure of rGO/rGO (without the g-C3N4-NSs layer).
The crossbar device showed similar memory effect with the directly laser-write one,
indicating that the accordingly I-V characteristics only relied on the functional
structure of rGO/g-C3N4-NSs/rGO. Furthermore, the controlled experiment of
rGO/rGO device showed I-V characteristics as a resistance, which confirmed that the
memory effect only relied on the functional g-C3N4-NSs layer in the structure of
rGO/g-C3N4-NSs/rGO.
Table S1. The ON/OFF ratios of flexible memory diodes reported previously.
Rewritability
ON/OFF ratio [orders]
Structure
Categorya)
Reference
Rewritable
3
G/SiOx/G
MF
S3
Rewritable
1
rGO/ABC10 SAM/rGO
MF
S4
Unrewritable
3
MWCNT/GO/MWCNT
MF
S5
Unrewritable
2
rGO/lrGO/GO
MF
S6
Rewritable
5
Al/PMMA/UGS/PMMA/ITO
ME
S7
Rewritable
5
Al/PS-b-P4VP/ITO
ME
S8
Rewritable
4
Al/PFT-PI/Al
ME
S9
Rewritable
4
Ti/Au/Al/PI:PCBM/Al
ME
S10
Rewritable
4
Si/a-Si/Ag
ME
S11
Rewritable
3
Al/GO/ITO
ME
S12
Rewritable
3
Al/PMMA:GQDs/ITO
ME
S13
Rewritable
2
Al/PI:PCBM/Au
ME
S14
Rewritable
2
Al/BCNT:NCNT/Al
ME
S15
Rewritable
2
Al/G-O/Al
ME
S16
Unrewritable
6
G/PI:PCBM/Al
ME
S17
Unrewritable
4
rGO/P3HT:PCBM/Al
ME
S18
Unrewritable
2
polypyrrole/P6FBEu/Au
ME
S19
Rewritable
6
Ag/ZnO:Mn/Pt
MB
S20
Rewritable
5
Ni/GeOx/HfON
MB
S21
Rewritable
4
Ag/Ag2Se/Au
MB
S22
Rewritable
4
Al/AlxOy/Al
MB
S23
Rewritable
4
Al/sol-gel ZnO/Al
MB
S24
Rewritable
3
Al/TiO2/Al
MB
S25
Rewritable
3
Al/polyaniline:Au/Al
MB
S26
Rewritable
3
Al/a-TiO2/Al
MB
S27
Rewritable
2
Al/CdSe:ZnS:PVK/ITO
MB
S28
Rewritable
2
Au/ZnO/stainless steel
MB
S29
Unrewritable
3
Ti/NiO/Cu
MB
S30
a)
The devices constructed with nonmetal electrodes and insulator layer (Metal-free,
marked as MF), metal electrode and nonmetal insulator layer (Metal electrode,
marked as ME), metal-containing electrodes and insulator layer (Metal-based, marked
as MB)
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