Abstract
Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials1,2,3. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility4,5,6,7,8. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures9,10,11 but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures12,13,14, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Novoselov, K. S ., Mishchenko, A ., Carvalho, A. & Neto, A. H. C. 2D materials and van der Waals heterostructures. Science 353, aac9439 (2016)
Liu, Y . et al. Van der Waals heterostructures and devices. Nat. Rev. Mater. 1, 16042 (2016)
Jariwala, D ., Marks, T. J. & Hersam, M. C. Mixed-dimensional van der Waals heterostructures. Nat. Mater. 16, 170–181 (2017)
Haigh, S. J . et al. Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices. Nat. Mater. 11, 764–767 (2012)
Yu, W. J . et al. Vertically stacked multi-heterostructures of layered materials for logic transistors and complementary inverters. Nat. Mater. 12, 246–252 (2013)
Cheng, R . et al. Electroluminescence and photocurrent generation from atomically sharp WSe2/MoS2 heterojunction p–n diodes. Nano Lett. 14, 5590–5597 (2014)
Lee, C. H . et al. Atomically thin p–n junctions with van der Waals heterointerfaces. Nat. Nanotech. 9, 676–681 (2014)
Withers, F . et al. Light-emitting diodes by band-structure engineering in van der Waals heterostructures. Nat. Mater. 14, 301–306 (2015)
Gong, Y . et al. Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nat. Mater. 13, 1135–1142 (2014)
Li, M.-Y . et al. Epitaxial growth of a monolayer WSe2–MoS2 lateral p–n junction with an atomically sharp interface. Science 349, 524–528 (2015)
Duan, X . et al. Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions. Nat. Nanotech. 9, 1024–1030 (2014)
Bao, W . et al. Approaching the limits of transparency and conductivity in graphitic materials through lithium intercalation. Nat. Commun. 5, 4224 (2014)
Yu, Y. J . et al. Gate-tunable phase transitions in thin flakes of 1T-TaS2 . Nat. Nanotech. 10, 270–276 (2015)
Xiong, F . et al. Li intercalation in MoS2: in situ observation of its dynamics and tuning optical and electrical properties. Nano Lett. 15, 6777–6784 (2015)
Li, L. K . et al. Black phosphorus field-effect transistors. Nat. Nanotech. 9, 372–377 (2014)
Perello, D. J ., Chae, S. H ., Song, S. & Lee, Y. H. High-performance n-type black phosphorus transistors with type control via thickness and contact-metal engineering. Nat. Commun. 6, 7809 (2015)
Yuan, H . et al. Polarization-sensitive broadband photodetector using a black phosphorus vertical p–n junction. Nat. Nanotech. 10, 707–713 (2015)
Pei, J . et al. Producing air-stable monolayers of phosphorene and their defect engineering. Nat. Commun. 7, 10450 (2016)
Ryder, C. R . et al. Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry. Nat. Chem. 8, 597–602 (2016)
Liu, H . et al. Phosphorene: an unexplored 2D semiconductor with a high hole mobility. ACS Nano 8, 4033–4041 (2014)
Li, L . et al. Direct observation of the layer-dependent electronic structure in phosphorene. Nat. Nanotech. 12, 21–25 (2016)
Castellanos-Gomez, A. Black phosphorus: narrow gap, wide applications. J. Phys. Chem. Lett. 6, 4280–4291 (2015)
Guan, J ., Song, W. S ., Yang, L. & Tomanek, D. Strain-controlled fundamental gap and structure of bulk black phosphorus. Phys. Rev. B 94, 045414 (2016)
Liu, Y ., Merinov, B. V. & Goddard, W. A. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals. Proc. Natl Acad. Sci. USA 113, 3735–3739 (2016)
Rudenko, A. N ., Brener, S. & Katsnelson, M. I. Intrinsic charge carrier mobility in single-layer black phosphorus. Phys. Rev. Lett. 116, 246401 (2016)
Chen, X. L . et al. High-quality sandwiched black phosphorus heterostructure and its quantum oscillations. Nat. Commun. 6, 7315 (2015)
Doganov, R. A . et al. Transport properties of pristine few-layer black phosphorus by van der Waals passivation in an inert atmosphere. Nat. Commun. 6, 6647 (2015)
Avsar, A . et al. Air-stable transport in graphene-contacted, fully encapsulated ultrathin black phosphorus-based field-effect transistors. ACS Nano 9, 4138–4145 (2015)
Acerce, M ., Voiry, D. & Chhowalla, M. Metallic 1T phase MoS2 nanosheets as supercapacitor electrode materials. Nat. Nanotech. 10, 313–318 (2015)
Voiry, D . et al. Covalent functionalization of monolayered transition metal dichalcogenides by phase engineering. Nat. Chem. 7, 45–49 (2015)
Sole, C., Drewett, N. E. & Hardwick, L. J. In situ Raman study of lithium-ion intercalation into microcrystalline graphite. Faraday Discuss. 172, 223–237 (2014)
Hembram, K. P. S. S. et al. A comparative first-principles study of the lithiation, sodiation, and magnesiation of black phosphorus for Li-, Na-, and Mg-ion batteries. Phys. Chem. Chem. Phys. 18, 21391–21397 (2016)
Hembram, K. P. S. S. et al. Unraveling the atomistic sodiation mechanism of black phosphorus for sodium ion batteries by first-principles calculations. J. Phys. Chem. C 119, 15041–15046 (2015)
Fei, R. & Yang, L. Lattice vibrational modes and Raman scattering spectra of strained phosphorene. Appl. Phys. Lett. 105, 083120 (2014)
Xiao, H., Tahir-Kheli, J. & Goddard, W. A. Accurate band gaps for semiconductors from density functional theory. J. Phys. Chem. Lett. 2, 212–217 (2011)
Crowley, J. M., Tahir-Kheli, J. & Goddard, W. A. Resolution of the band gap prediction problem for materials design. J. Phys. Chem. Lett. 7, 1198–1203 (2016)
Cai, J. M. et al. Graphene nanoribbon heterojunctions. Nat. Nanotech. 9, 896–900 (2014)
Yu, W. J., Liao, L., Chae, S. H., Lee, Y. H. & Duan, X. F. Toward tunable band gap and tunable Dirac point in bilayer graphene with molecular doping. Nano Lett. 11, 4759–4763 (2011)
Levendorf, M. P. et al. Graphene and boron nitride lateral heterostructures for atomically thin circuitry. Nature 488, 627–632 (2012)
Cai, Y., Zhang, G. & Zhang, Y.-W. Layer-dependent band alignment and work function of few-layer phosphorene. Sci. Rep. 4, 6677 (2014)
Yang, Z. B. et al. Field-effect transistors based on amorphous black phosphorus ultrathin films by pulsed laser deposition. Adv. Mater. 27, 3748–3754 (2015)
Xia, F., Wang, H. & Jia, Y. Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics. Nat. Commun. 5, 4458 (2014)
Kamalakar, M. V., Madhushankar, B. N., Dankert, A. & Dash, S. P. Low Schottky barrier black phosphorus field-effect devices with ferromagnetic tunnel contacts. Small 11, 2209–2216 (2015)
Miao, J. S., Zhang, S. M., Cai, L., Scherr, M. & Wang, C. Ultrashort channel length black phosphorus field-effect transistors. ACS Nano 9, 9236–9243 (2015)
Youngblood, N., Chen, C., Koester, S. J. & Li, M. Waveguide-integrated black phosphorus photodetector with high responsivity and low dark current. Nat. Photon. 9, 247–252 (2015)
Na, J. et al. Few-layer black phosphorus field-effect transistors with reduced current fluctuation. ACS Nano 8, 11753–11762 (2014)
Wood, J. D. et al. Effective passivation of exfoliated black phosphorus transistors against ambient degradation. Nano Lett. 14, 6964–6970 (2014)
Buscema, M. et al. Fast and broadband photoresponse of few-layer black phosphorus field-effect transistors. Nano Lett. 14, 3347–3352 (2014)
Kim, J. S. et al. Dual gate black phosphorus field effect transistors on glass for nor logic and organic light emitting diode switching. Nano Lett. 15, 5778–5783 (2015)
Hong, T. et al. Polarized photocurrent response in black phosphorus field-effect transistors. Nanoscale 6, 8978–8983 (2014)
Koenig, S. P., Doganov, R. A., Schmidt, H., Neto, A. H. C. & Ozyilmaz, B. Electric field effect in ultrathin black phosphorus. Appl. Phys. Lett. 104, 103106 (2014)
Zhu, W. N. et al. Flexible black phosphorus ambipolar transistors, circuits and AM demodulator. Nano Lett. 15, 1883–1890 (2015)
Wang, H. et al. Black phosphorus radio-frequency transistors. Nano Lett. 14, 6424–6429 (2014)
Kah-Wee, A., Zhi-Peng, L. & Juntao, Z. Next generation field-effect transistors based on 2D black phosphorus crystal. 2015 IEEE Int. Conf. on Digital Signal Processing. 1223–1226 (2015).
Viti, L. et al. Efficient terahertz detection in black-phosphorus nano-transistors with selective and controllable plasma-wave, bolometric and thermoelectric response. Sci. Rep. 6, 20474 (2016)
Wan, B. S . et al. Enhanced stability of black phosphorus field-effect transistors with SiO2 passivation. Nanotechnology 26, 435702 (2015)
Acknowledgements
The authors acknowledge the Electron Imaging Center for NanoMachines (EICN) at California NanoSystem Institute (CNSI) and Nanoelectronic Research Facility (NRF) at UCLA for technical support. Xiangfeng D. acknowledges support by National Science Foundation DMR1508144 (materials synthesis) and Office of Naval Research through grant number N00014-15-1-2368 (device fabrications). Y.H. acknowledges support by National Science Foundation EFRI-1433541. Y.L. was supported by a Resnick Prize Postdoctoral Fellowship at Caltech. L.L. acknowledges support through the 973 grant of MOST (No. 2013CBA01604). X.H.C. acknowledges support from the National Natural Science Foundation of China (Grant No. 11534010). W.A.G. and Y.L. were also supported by DOE DE-SC0014607. W.A.G acknowledges the Extreme Science and Engineering Discovery Environment (XSEDE) supported by National Science Foundation grant ACI-1053575. Y.L. acknowledges the computational resources sponsored by the DOE’s Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory, and the Texas Advanced Computing Center (TACC). I.S. thanks the Deanship of Scientific Research at King Saud University for its funding of this research through grant PEJP-17-01.
Author information
Authors and Affiliations
Contributions
Xiangfeng D., Y.H. and C.W. co-designed the research. C.W. conducted device fabrication, electrical properties measurements and data analysis. C.W., Q.H. and U.H. conducted the intercalation experiments. C.W., U.H., Z.L. and Z.F. conducted structural and optical characterizations. Y.L., H.X. and W.A.G. contributed to the superlattice atomic and electronic structure calculations. E.Z. conducted the TEM studies. Q.H., Xidong D., Y.-C.H., H.W., H.-C.C., I.S. and L.L. contributed to the initial measurement system set-up, preparation of 2D materials and data analysis. R.C. contributed to the initial BP property characterization. N.O.W. contributed to the schematic drawing. G.J.Y. and X.H.C. prepared the initial BP material. Y.H. and Xiangfeng D. supervised the research. Xiangfeng D. and C.W. co-wrote the manuscript. All authors discussed the results and commented on the manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Additional information
Reviewer Information Nature thanks N. Guisinger, K. Loh and Q. Xiong for their contribution to the peer review of this work.
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Figure 1 Stepwise reaction mechanism and its partition map.
First derivative of the electrochemical gate current in Fig. 2a. By analysing the original current curve and local minimum of the first derivative, the stepwise reaction can be clearly identified: that is, no major intercalation for 0–1.0 V (over-potential for Br− sub-reaction), 1.0–1.4 V for major bulk intercalation, 1.4–2.0 V for few-layer BP formation, 2.0–2.5 V for trilayer BP formation, 2.5–3.0 V for bilayer BP formation and beyond 3.0 V for MPMS formation, which is also consistent with bandgap evolution from bulk, few, trilayer and bilayer to monolayer phosphorene.
Extended Data Figure 2 TEM EDX spectra of BP and MPMS.
a, b, Spectra of BP and MPMS, showing the existence of Br and N after intercalation. Three average spectra gave an atomic ratio of P:N:Br as 33.2:1.2:1.0.
Extended Data Figure 3 Raman spectra characterization of BP and MPMS.
a, Raman spectra to compare the relative peak intensity and full-width at half-maximum evolution from pristine BP (black) to MPMS (red). The MPMS spectrum is multiplied by 20 for easy comparison. b–d, Ag1, B2g and Ag2 mode comparison between pristine BP and MPMS to show redshift, blueshift and blueshift after MPMS formation, respectively. Insets: schematic illustration of atomic motion of each vibration modes.
Extended Data Figure 4 The calculated electronic band structure evolution from BP to MPMS.
a, b, Electronic structure of monolayer phosphorene (a) and MPMS (b), demonstrating the enlarged bandgap from 1.94 eV in monolayer phosphorene to 2.13 eV in MPMS, as determined by the transition from VBM-1 (green) and CBM (red). The newly introduced bands of MPMS marked as grey dotted lines are mainly from bromine atomic p orbitals. The orange VBM-0 band is mainly (about 90%) from phosphorus, but those orbitals contribute little to the optical transition, owing to very small overlap with the CBM. c, d, e, Monolayer phosphorene charge-density distribution of CBM (red in a), VBM-0 (orange in a) and VBM-1 (green in a), showing the transition bandgap determined by CBM and VMB-0/VMB-1 (very close in energy). f, g, h, MPMS charge-density distribution of CBM (red in b), VBM-0 (orange in b) and VBM-1 (green in b), showing the transition bandgap determined by VBM-1 and CBM due to large overlap of charge density.
Extended Data Figure 5 The on/off ratio and mobility of the MPMS devices and the recently reported few-layer and thin BP devices.
Six MPMS devices (red star) show an average mobility of 270 cm2 V−1 s−1 and averaged on/off ratio of 8.6 × 106. For comparison, we list recent studies of few-layer BP (less than 5 nm, marked as the blue triangle) and thin BP (5 nm to 15 nm, marked as the black square) devices. The MPMS devices outperform the best few-layer BP devices in both mobility and on/off ratio, and show comparable mobility but much higher on/off ratio than thin BP devices. Data points indexed are taken from the following: data 1 from ref. 41, data 2 from ref. 28, data 3 from ref. 42, data 4 from ref. 43, data 5 from ref. 27, data 6 from ref. 42, data 7 from ref. 20, data 8 from ref. 44, data 9 from ref. 42, data 10 from ref. 45, data 11 from ref. 46, data 12 from ref. 47, data 13 from ref. 48, data 14 from ref. 49, data 15 from ref. 50, data 16 from ref. 46, data 17 from ref. 19, data 18 from ref. 46, data 19 from ref. 51, data 20 from ref. 52, data 21 from ref. 53, data 22 from ref. 54, data 23 from ref. 55, data 24 from ref. 56, data 25 from ref. 15, data 26 from ref. 26.
Extended Data Figure 6 Lateral BP–MPMS heterojunction.
a, Photoluminescence mapping (at 553 nm) of a lateral BP–MPMS heterostructure to highlight the MPMS part. Scale bar: 3 μm. The signal in the electrode area is due to a scattering-induced background. b, The corresponding Raman spectral mapping centred at 438 cm−1 to show the main BP region with stronger Raman signal. Scale bar: 3 μm. c, SEM image to show the lateral BP–MPMS heterojunction device. Scale bar: 3 μm. d, Schematic illustration of a lateral BP–MPMS heterojunction. e, Band diagram of the BP–MPMS heterojunction. f, The typical diode characteristics of a lateral BP–MPMS heterojunction; inset: optical microscope image of the corresponding BP–MPMS heterojunction. Scale bar: 3 μm.
Extended Data Figure 7 XRD patterns of MACMS obtained from six additional 2DACs.
a, XRD pattern of WSe2 and WSe2/CTAB superlattice verifying the interlayer distance expansion from 6.43 Å (13.76°) of WSe2 (002) peak (black) to 15.20 Å (5.81°) of WSe2/CTAB superlattice (002) peak (red). b, XRD pattern of SnSe and SnSe/CTAB superlattice demonstrating the interlayer distance expansion from 5.74 Å (31.16°) of SnSe (004) peak (black) to 15.62 Å (5.65°) of SnSe/CTAB superlattice (002) peak (red). c, XRD pattern of GeS and GeS/CTAB superlattice showing the interlayer distance expansion from 5.18 Å (34.58°) of GeS (004) peak (black) to 15.76 Å (5.60°) of GeS/CTAB superlattice (002) peak (red). d, XRD pattern of NbSe2 and NbSe2/CTAB superlattice revealing the interlayer distance expansion from 6.18 Å (14.31°) of NbSe2 (002) peak (black) to 14.85 Å (5.95°) of NbSe2/CTAB superlattice (002) peak (red). e, XRD pattern of Bi2Se3 and Bi2Se/CTAB superlattice exhibiting the interlayer distance expansion from 14.16 Å (18.78°) of Bi2Se3 (006) peak (black) to 23.07 Å (11.49°) of Bi2Se3/CTAB superlattice (006) peak (red). f, XRD pattern of In2Se3 and In2Se3/CTAB superlattice indicating the interlayer distance expansion from 9.50 Å (18.67°) of the In2Se3 (004) peak (black) to 15.40 Å (11.48°) of the In2Se3/CTAB superlattice (004) peak (red).
Rights and permissions
About this article
Cite this article
Wang, C., He, Q., Halim, U. et al. Monolayer atomic crystal molecular superlattices. Nature 555, 231–236 (2018). https://doi.org/10.1038/nature25774
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nature25774
This article is cited by
-
Precise control of van der Waals gaps
Nature Nanotechnology (2024)
-
Emerging probing perspective of two-dimensional materials physics: terahertz emission spectroscopy
Light: Science & Applications (2024)
-
Intercalation in 2D materials and in situ studies
Nature Reviews Chemistry (2024)
-
Superlattice cathodes endow cation and anion co-intercalation for high-energy-density aluminium batteries
Nature Communications (2024)
-
Controllable van der Waals gaps by water adsorption
Nature Nanotechnology (2024)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.
