This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Article Cite This: ACS Omega 2018, 3, 5125−5130
Coherent Resonant Electron Tunneling at 9 and 300 K through a 4.5 nm Long, Rigid, Planar Organic Molecular Wire Chun Ouyang,†,‡ Kohei Hashimoto,§ Hayato Tsuji,*,§,∥ Eiichi Nakamura,*,§ and Yutaka Majima*,† †
Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan Surface and Interface Science Laboratory, RIKEN, Saitama 351-0198, Japan § Department of Chemistry, School of Science, University of Tokyo, Tokyo 113-0033, Japan ∥ Department of Chemistry, Faculty of Science, Kanagawa University, Hiratsuka 259-1293, Japan ‡
S Supporting Information *
ABSTRACT: Organic molecular wires that operate stably at ambient temperatures are a necessary first step toward practical and useful molecularscale electronic devices, which have thus far been hampered by many factors, including the structural and electron configurational instability of organic molecules. We report here that a single disulfanyl carbon-bridged oligo(phenylenevinylene) (COPV6) molecule embedded between thermally stable electroless Au-plated electrodes of a 4 nm nanogap undergoes coherent resonant tunneling at both 9 and 300 K and functions even after storage in air at room temperature. Such enormous stability is ascribed to the unique structural characteristics of COPV6, that is, rigidity, planarity, thermal stability, resistivity against oxidation and reduction, and an organic insulating sheath that protects the π-system. When sandwiched between the gaps without pinning, this molecule behaves as a Coulomb island with sequential single-electron tunneling at 9 K that disappears at 300 K while maintaining a stable electron flow.
1. INTRODUCTION The size limits of the conventional top-down fabrication of integrated circuits have spurred research on molecular-scale electronics.1−13 However, to date, organic molecular electronic devices have shown optimal performance only under cryogenic conditions6,14 owing to thermal fluctuation of both the organic structures and the metal electrodes. The development of selfterminating electroless Au-plated (ELGP) nanogap electrodes has provided a solution to the latter problem because of the thermal stability of the nanogap up to 443 K (Figures 1b, S1.1, and S1.2).15−17 The former issue, however, awaits development of new classes of molecular wires. To this end, we focused on a 4.5 nm long disulfanyl carbon-bridged oligo(phenylenevinylene)18−20 (COPV6(SH)2) (Figure 1a), in which six phenylenevinylene units (thus called COPV6) are connected by carbon bridges (blue). This molecule, which has a molecular weight of 2674, resembles a spindle (Figure 1c), in which the center of the rigid π-conjugated system is spatially and electronically isolated from its surroundings by four 4octylphenyl groups, whereas the SH terminals are less hindered to contact the gold surface. When all of these groups are made of the bulky 4-octylphenyl groups, no sign of bonding to the electrodes can be found. The parent COPV6 scaffold is exceptionally stable, thermally (up to 623 K), under laser irradiation, and even in its tetra-cationic forms.18−22 We report here that the chemical binding of a single COPV6(SH)2 © 2018 American Chemical Society
molecule to an ELGP nanogap of an average 4 nm gap length creates a device referred to as SAuSH (Figure 1c) that exhibits coherent resonant electron tunneling transportation (hereafter, coherent tunneling) both at 9 and at 300 K, with conductance greater than 2 nS. Although such temperature independence is a typical property of electron tunneling, it has not been seen for flexible organic molecular wires. The SAuSH device stored in air at ambient temperature for 3 months showed the same electronic characteristics, attesting to the unprecedented stability of the molecule and nanogap. Another type of device (SH)2 (Figure 1c) was found and underwent sequential singleelectron tunneling (hereafter, sequential tunneling) at 9 K.
2. RESULTS AND DISCUSSION The self-terminating ELGP method15−17 produces 80 electrodes at once with an average 4 nm nanogap in 90% yield in two steps (Figure 1b).16 First, we made electrodes with an Au/Ti initial nanogap of approximately 20 nm on SiO2/Si (Figure S1.1) and then narrowed the gap to 4 nm by ELGP using an aqueous solution of ascorbic acid and Au(I) ion (Figure S1.2). The electrodes were immersed in a 0.5 mM toluene solution of COPV6(SH)2 for 3 h at 353 K, rinsed twice with acetone and Received: March 24, 2018 Accepted: April 27, 2018 Published: May 10, 2018 5125
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
Article
ACS Omega
Figure 1. Molecular wire and nanogap. (a) Structure of COPV6(SH)2. (b) scanning electron microscopy and transmission electron microscopy images of top view of device #1 and typical cross-sectional view of ELGP nanogaps, respectively. The red circle indicates the 4 nm wide nanogap. (c) Three modes of embedding in the ELGP nanogap, showing a model where the π-system and side chains are color-coded differently in red and green, respectively.
In the dId/dVd diagram of device #1 (Figure 2b; bottom), the first negative (−1.16 V) and first positive peaks (1.19 V) differ by 2.35 V, that is, close to the photoluminescence energy of 2.3 eV,18 and the overall peak voltage differences (0.26, 2.35, and 0.23 V) agree in their relative magnitude with the calculated EHOMO−1 − EHOMO, EHOMO − ELUMO, and ELUMO − ELUMO+1 energy gaps of 0.35, 2.74, and 0.29 eV, respectively (Figure 3a). As illustrated by the model in Figure 1c, the molecule in the SAuSH device is pinned only at the drain Au electrode by S− Au bond formation. A band diagram of the coherent tunneling is shown in Figure 3, where the Fermi level of the source electrode moves with the bias voltage because of van der Waals contact of the free HS side of the molecule to this electrode. The drain current is enhanced by the coherent tunneling process when the Fermi level of the Au source electrode coincides with the molecular orbital energy levels of COPV6(SH)2. A similar diagram was previously proposed for a onesided pinning structure of the tip/vacuum/tribenzosubporphine/C7S mixed SAM/Au(111) system.10 Most remarkably, the SAuSH device sustains thermal cycling at 9 and 300 K. The Id−Vd characteristics of device #1 at 300 K still shows coherent tunneling behavior (Figure 2e), whereas the no-current bias voltage region is nearly half, reflecting thermal broadening of molecular resonant tunneling phenomena (Figure 2b). The temperature insensitivity is a signature of electron tunneling, as found previously for photoexcited electron tunneling through shorter COPV nanowires.19 A comparison of the dId−dVd diagrams for device #1 at 9 K (Figure 2b) and 300 K (Figure 2e) indicates that the first negative and positive peaks derived from highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) at 300 K broke down to multiple peaks, whereas the peaks derived from HOMO − 1 and LUMO + 1 remained largely unchanged. We suggest that the temperature insensitivity of the latter stems from the presence of a node in
ethanol to remove any weakly adsorbed molecules, and then subjected to electrical characterization at 9 and 300 K. Before COPV6(SH)2 impregnation, none of the few hundred nanogaps showed conduction (Figure 2a). After impregnation, we found five functioning devicesthree SAuSH (devices #1− 3) and two (SH)2 (devices #4 and 5), whereas none of the remaining gaps showed any current. Notably, we did not find any device that shows the Id−Vd characteristics expected for the structurally symmetric COPV6(SAu)2 device formed in the nanogap. All three SAuSH devices, #1, 2, and 3 (Figure 2b−d), exhibited Id−Vd characteristics at 9 K typical of a coherent tunneling molecular wire. For all three devices, bidirectional sweeps of the drain bias voltage from −1.5 to 1.5 V (solid black line; top) and from 1.5 to −1.5 V (red dashed line) matched perfectly, indicating the stability of the device at 9 K. The logarithmic plot of |Id| illustrates that the no-current bias voltage region extended between −1.08 and 1.11 V (middle), and the dId/dVd diagram (bottom) numerically calculated from the Id−Vd data shows four well-defined dId/dVd peaks, that is, on device #1, at Vd = −1.41, −1.16, 1.19, and 1.41 V. This Id− Vd characteristic represents unprecedented long-range (4.5 nm) and stable coherent tunneling, ascribable to the stability of both the wire and the ELGP nanogap. A slight variation in the Vd values among the three devices reflected the difference in the local physicochemical configuration of the molecular wire. The differential conductance peaks shown in the dId/dVd diagram (Figure 2b−d; bottom) were larger than 4 nS, a very large value for such a long organic nanowire, owing to the effective electron conjugation over the entire COPV6 framework. Previously studied flexible oligophenylenevinylene and oligophenyleneethynylene molecules exhibited coherent tunneling behavior only for those shorter than 2 nm.14,21,23−30 5126
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
Article
ACS Omega
Figure 2. Id−Vd characteristics of the nanogap and SAuSH devices. The forward drain bias voltage scan is shown as a solid black line, and the reverse scan is shown as a red dashed line. (a) Nonfunctioning nanogap before (top) and after (bottom) immersion in COPV6(SH)2 solution. (b−d) Three devices (#1, 2, and 3) at 9 K. Top: Id−Vd, middle: logarithmic plot of |Id|, and bottom: differential conductance (dId/dVd−Vd). (e) Device #1 at 300 K. (f) Device #1 after storage in air for 3 months, measured at 9 K. Four well-defined dId/dVd peaks appear at Vd = −1.41, −1.16, 1.19, and 1.41 V on device #1.
the center of HOMO − 1 and LUMO + 1, whereas the sensitivity of the former stems from its absence in HOMO and LUMO (Figure 3b). Of a few hundred devices examined at 9 K, we found two (devices #4 and 5) that showed Id−Vd characteristics of sequential tunneling attributable to the (SH)2 device based on the Coulomb blockade effect at 9 K (Figure 4a,b). At 300 K, the no-current voltage regions disappeared as shown in Figure 4ca typical behavior of sequential single-electron tunneling. Details follow in the next paragraph. By applying consecutive bidirectional sweeps of drain bias voltage from −0.8 to 0.8 V (forward bias sweep; solid black line) and from 0.8 to −0.8 V (backward; red dashed line), we observed stable and reproducible Id−Vd characteristics for both sweep directions. A no-current bias voltage region was observed over a bias voltage range of 280 mV between −0.14 and 0.14 V,
which is about one-eighth of the range of the coherent tunneling scheme at 9 K shown in Figure 2b. The first and second stairs at both positive and negative voltages were observed at 0.22, 0.60, and −0.19 and −0.53 V, respectively. From Figure 4b, we calculated a differential conductance of ca. 20 pS, which is 2 orders of magnitude smaller than that of the coherent tunneling scheme determined from Figure 2b−d. The current flow at 300 K under the application of Vd remained in the same order at 9 K (Figure 4a vs c), attesting to the stability of the COPV6 device at 300 K owing to the thermal stability of the nanogap and the COPV6 system that can form a stable tetra-cation, as examined by cyclic voltammetry at ambient temperature.20 To further probe the origin of the Id−Vd characteristics, we examined an equivalent circuit of double-barrier tunneling junctions (Figure 4d).31−34 From this model, we obtained a 5127
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
Article
ACS Omega
parameters (Figure 4d; Supporting Information section 2.2): resistances and capacitances of both tunneling barriers (R1, R2, C1, and C2) and the fractional electron charge present on the Coulomb island (Q0):29,32,35 R1 = 46.8 GΩ, R2 = 13.6 GΩ, C1 = 0.42 aF, C2 = 0.42 aF, and Q0 = 0.1e for device #4, and R1 = 12.0 GΩ, R2 = 11.0 GΩ, C1 = 0.41 aF, C2 = 0.4 aF, and Q0 = −0.1e for device #5 (where e is the elementary charge). With this agreement between theory and experiments, we concluded that COPV6(SH)2 behaved as a Coulomb island for which we suggest physisorption of the molecule by its hydrocarbon onto the electrode surface [(SH)2 in Figure 1c], where there is no electronic coupling. The estimated tunneling resistances were similar to the physisorbed tunneling resistance previously reported for an Au nanoparticle protected by octanethiol chains embedded between two Au electrodes,36−39 further supporting the (SH)2 device structure. The almost same charging energies Ec = e2/2C in this system were evaluated as 95.3 and 98.3 meV for devices #4 and #5, respectively, a value that is in good agreement with the long, planar, rigid nature of the π-conjugation in the COPV wire, as compared with the shorter and more flexible OPV analogues,14,21 in which the width of the Coulomb diamonds along the Vd axis (ΔVd) reflected the value of Ec as ΔVd = 4Ec.31,40 The calculated charging energies of such short molecular wires based on experimental Coulomb diamonds14,21 are approximately 440 and 110 meV, respectively, and the 95.3 and 98.3 meV values are expectedly smaller.
Figure 3. Orbital properties of COPV6(SH)2 and energy band diagrams. (a) Kohn−Sham orbitals (isovalue of 0.02 e/Å3) of a model compound of COPV6(SH)2 (R1, R2, R3 = CH3) obtained at the B3LYP/6-31G level of theory. (b) Orbital coefficients. The red dotted lines indicate nodes. (c) Energy band diagrams of the Au source electrode/HS-COPV6-S-/Au drain electrode structure (SAuSH device) with various Vd values.
3. CONCLUSIONS In summary, we have shown that the SAuSH device exhibited the archetypal behaviors of coherent tunneling devices, including tolerance to thermal cycling between low and high temperatures, which we had hoped to see for practical and useful organic molecular wires. Such stability is distinct from that of devices using flexible organic molecular wires. Given the many possible variations available for the COPV class of molecules, as well as for the ELGP nanogap configurations, we expect that the selective formation of either SAuSH or (SH)2 type device can be controlled by synthetic modifications and adjustments of gap separation and molecular length, and that the data reported here will provide a solid foundation for exploring new directions of molecular-scale electronic research in the future.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b00559. SEM Images; Id−Vd characteristics; back gate current− drain bias voltage characteristics; synthesis of COPV6(SH)2; and fabrication of the devices (PDF)
■
Figure 4. Characteristics of (SH)2 devices (#4 and 5). (a,b) Current− voltage (Id−Vd) and differential conductance (dId/dVd−Vd) characteristics at 9 K. (c) Id data at 300 K. (d) Equivalent circuits of a doublebarrier tunneling junction system. (e) Schematic energy band diagram at zero bias and positive bias V = e/C.
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (Y.M.). *E-mail:
[email protected] (H.T.). *E-mail:
[email protected] (E.N.). ORCID
theoretical Id−Vd curve that fits very well with the experimental one (Figure 4a,b; blue dashed-dotted line), using five
Hayato Tsuji: 0000-0001-7663-5879 Eiichi Nakamura: 0000-0002-4192-1741 5128
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
Article
ACS Omega Notes
(17) Serdio, V. M.; Muraki, T.; Takeshita, S.; Hurtado, S. D. E.; Kano, S.; Teranishi, T.; Majima, Y. Gap separation-controlled nanogap electrodes by molecular ruler electroless gold plating. RSC Adv. 2015, 5, 22160. (18) Zhu, X.; Tsuji, H.; Navarrete, J. T. L.; Casado, J.; Nakamura, E. Carbon-bridged oligo(phenylenevinylene)s: stable π-systems with high responsiveness to doping and excitation. J. Am. Chem. Soc. 2012, 134, 19254. (19) Sukegawa, J.; Schubert, C.; Zhu, X.; Tsuji, H.; Guldi, D. M.; Nakamura, E. Electron transfer through rigid organic molecular wires enhanced by electronic and electron−vibration coupling. Nat. Chem. 2014, 6, 899. (20) Burrezo, P. M.; Zhu, X.; Zhu, S.-F.; Yan, Q.; Navarrete, J. T. L.; Tsuji, H.; Nakamura, E.; Casado, J. Planarization, fusion, and strain of carbon-bridged phenylenevinylene oligomers enhance π-electron and charge conjugation: a dissectional vibrational Raman study. J. Am. Chem. Soc. 2015, 137, 3834. (21) Danilov, A.; Kubatkin, S.; Kafanov, S.; Hedegård, P.; StuhrHansen, N.; Moth-Poulsen, K.; Bjørnholm, T. Electronic transport in single molecule junctions: control of the molecule-electrode coupling through intramolecular tunneling barriers. Nano Lett. 2008, 8, 1. (22) Burrezo, P. M.; Lin, N.-T.; Nakabayashi, K.; Ohkoshi, S.-i.; Calzado, E. M.; Boj, P. G.; Díaz García, M. A.; Franco, C.; Rovira, C.; Veciana, J.; Moos, M.; Lambert, C.; López Navarrete, J. T.; Tsuji, H.; Nakamura, E.; Casado, J. Bis(aminoaryl) carbon-bridged oligo(phenylenevinylene)s expand the limits of electronic couplings. Angew. Chem., Int. Ed. 2017, 56, 2898. (23) Choi, S. H.; Kim, B.; Frisbie, C. D. Electrical resistance of long conjugated molecular wires. Science 2008, 320, 1482. (24) Yamada, R.; Kumazawa, H.; Tanaka, S.; Tada, H. Electrical resistance of long oligothiophene molecules. Appl. Phys. Express 2009, 2, 025002. (25) Huber, R.; González, M. T.; Wu, S.; Langer, M.; Grunder, S.; Horhoiu, V.; Mayor, M.; Bryce, M. R.; Wang, C.; Jitchati, R.; Schönenberger, C.; Calame, M. Electrical conductance of conjugated oligomers at the single molecule level. J. Am. Chem. Soc. 2008, 130, 1080. (26) Lu, Q.; Liu, K.; Zhang, H.; Du, Z.; Wang, X.; Wang, F. From tunneling to hopping: a comprehensive investigation of charge transport mechanism in molecular junctions based on oligo(pphenylene ethynylene)s. ACS Nano 2009, 3, 3861. (27) de la Torre, G.; Giacalone, F.; Segura, J. L.; Martín, N.; Guldi, D. M. Electronic communication through π-conjugated wires in covalently linked porphyrin/C60 ensembles. Chem.Eur. J. 2005, 11, 1267. (28) Ricks, A. B.; Brown, K. E.; Wenninger, M.; Karlen, S. D.; Berlin, Y. A.; Co, D. T.; Wasielewski, M. R. Exponential distance dependence of photoinitiated stepwise electron transfer in donor−bridge−acceptor molecules: Implications for wirelike behavior. J. Am. Chem. Soc. 2012, 134, 4581. (29) Frisch, M. J.; et al. Gaussian 09, Revision A. 02; Gaussian, Inc.: Wallingford CT, 2009 (full citations of authors in Supporting Information section 2.4). (30) Zhao, X.; Huang, C.; Gulcur, M.; Batsanov, A.; Baghernejad, M.; Hong, W.; Bryce, M.; Wandlowski, T. Oligo(aryleneethynylene)s with terminal pyridyl groups: Synthesis and length dependence of the tunneling-to-hopping transition of single-molecule conductances. Chem. Mater. 2013, 25, 4340. (31) Kano, S.; Tanaka, D.; Sakamoto, M.; Teranishi, T.; Majima, Y. Control of charging energy in chemically assembled nanoparticle single-electron transistors. Nanotechnology 2015, 26, 045702. (32) Zhang, H.; Yasutake, Y.; Shichibu, Y.; Teranishi, T.; Majima, Y. Tunneling resistance of double-barrier tunneling structures with an alkanethiol-protected Au nanoparticle. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 205441. (33) Li, X.; Yasutake, Y.; Kono, K.; Kanehara, M.; Teranishi, T.; Majima, Y. Au nanoparticles chemisorbed by dithiol molecules inserted in alkanethiol self-assembled monolayers characterized by scanning tunneling microscopy. Jpn. J. Appl. Phys. 2009, 48, 04C180.
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors thank Dr. N. Umezawa (MANA, NIMS), Dr. M. Araidai (Nagoya University), and Dr. D. Lungerich (Tokyo) for fruitful discussions. This study was partially supported by MEXT Elements Strategy Initiative to Form Core Research Centers; the Collaborative Research Project of the Laboratory for Materials and Structures, Tokyo Institute of Technology; the BK Plus program, Basic Science Research program (NRF2014R1A6A1030419); and Grants-in-Aid for scientific research (15H05754 to E.N. and 16H04106 to H.T.).
■
REFERENCES
(1) Aviram, A.; Ratner, M. A. Molecular rectifier. Chem. Phys. Lett. 1974, 29, 277. (2) Nitzan, A.; Ratner, M. A. Electron transport in molecular wire junctions. Science 2003, 300, 1384. (3) Moth-Poulsen, K.; Bjørnholm, T. Molecular electronics with single molecules in solid-state devices. Nat. Nanotechnol. 2009, 4, 551. (4) Wu, S.; González, M. T.; Huber, R.; Grunder, S.; Mayor, M.; Schönenberger, C.; Calame, M. Molecular junctions based on aromatic coupling. Nat. Nanotechnol. 2008, 3, 569. (5) Tao, N. J. Electron transport in molecular junctions. Nat. Nanotechnol. 2006, 1, 173. (6) Park, J.; Pasupathy, A. N.; Goldsmith, J. I.; Chang, C.; Yaish, Y.; Petta, J. R.; Rinkoski, M.; Sethna, J. P.; Abruña, H. D.; McEuen, P. L.; Ralph, D. C. Coulomb blockade and the Kondo effect in single-atom transistors. Nature 2002, 417, 722. (7) Park, H.; Park, J.; Lim, A. K. L.; Anderson, E. H.; Alivisatos, A. P.; McEuen, P. L. Nanomechanical oscillations in a single-C60 transistor. Nature 2000, 407, 57. (8) Song, H.; Kim, Y.; Jang, Y. H.; Jeong, H.; Reed, M. A.; Lee, T. Observation of molecular orbital gating. Nature 2009, 462, 1039. (9) Sun, L.; Diaz-Fernandez, Y. A.; Gschneidtner, T. A.; Westerlund, F.; Lara-Avila, S.; Moth-Poulsen, K. Single-molecule electronics: from chemical design to functional devices. Chem. Soc. Rev. 2014, 43, 7378. (10) Majima, Y.; Ogawa, D.; Iwamoto, M.; Azuma, Y.; Tsurumaki, E.; Osuka, A. Negative differential resistance by molecular resonant tunneling between neutral tribenzosubporphine anchored to a Au(111) surface and tribenzosubporphine cation adsorbed on to a tungsten tip. J. Am. Chem. Soc. 2013, 135, 14159. (11) Lörtscher, E.; Cho, C. J.; Mayor, M.; Tschudy, M.; Rettner, C.; Riel, H. Influence of the anchor group on charge transport through single-molecule junctions. ChemPhysChem 2011, 12, 1677. (12) Chen, F.; Li, X.; Hihath, J.; Huang, Z.; Tao, N. Effect of anchoring groups on single-molecule conductance: comparative study of thiol-, amine-, and carboxylic-acid-terminated molecules. J. Am. Chem. Soc. 2006, 128, 15874. (13) Jia, C.; Migliore, A.; Xin, N.; Huang, S.; Wang, J.; Yang, Q.; Wang, S.; Chen, H.; Wang, D.; Feng, B.; Liu, Z.; Zhang, G.; Qu, D.-H.; Tian, H.; Ratner, M. A.; Xu, H. Q.; Nitzan, A.; Guo, X. Covalently bonded single-molecule junctions with stable and reversible photoswitched conductivity. Science 2016, 352, 1443. (14) Kubatkin, S.; Danilov, A.; Hjort, M.; Cornil, J.; Brédas, J.-L.; Stuhr-Hansen, N.; Hedegård, P.; Bjørnholm, T. Single-electron transistor of a single organic molecule with access to several redox states. Nature 2003, 425, 698. (15) Yasutake, Y.; Kono, K.; Kanehara, M.; Teranishi, T.; Buitelaar, M. R.; Smith, C. G.; Majima, Y. Simultaneous fabrication of nanogap gold electrodes by electroless gold plating using a common medical liquid. Appl. Phys. Lett. 2007, 91, 203107. (16) Serdio, V. M.; Azuma, Y.; Takeshita, S.; Muraki, T.; Teranishi, T.; Majima, Y. Robust nanogap electrodes by self-terminating electroless gold plating. Nanoscale 2012, 4, 7161. 5129
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
Article
ACS Omega (34) Okabayashi, N.; Maeda, K.; Muraki, T.; Tanaka, D.; Sakamoto, M.; Teranishi, T.; Majima, Y. Uniform charging energy of singleelectron transistors by using size-controlled Au nanoparticles. Appl. Phys. Lett. 2012, 100, 033101. (35) Hanna, A. E.; Tinkham, M. Variation of the Coulomb staircase in a two-junction system by fractional electron charge. Phys. Rev. B: Condens. Matter Mater. Phys. 1991, 44, 5919. (36) Maeda, K.; Okabayashi, N.; Kano, S.; Takeshita, S.; Tanaka, D.; Sakamoto, M.; Teranishi, T.; Majima, Y. Logic operations of chemically assembled single-electron transistor. ACS Nano 2012, 6, 2798. (37) Azuma, Y.; Onuma, Y.; Sakamoto, M.; Teranishi, T.; Majima, Y. Rhombic Coulomb diamonds in a single-electron transistor based on an Au nanoparticle chemically anchored at both ends. Nanoscale 2016, 8, 4720. (38) Azuma, Y.; Yasutake, Y.; Kono, K.; Kanehara, M.; Teranishi, T.; Majima, Y. Single-electron transistor fabricated by two bottom-up processes of electroless Au plating and chemisorption of Au nanoparticle. Jpn. J. Appl. Phys. 2010, 49, 090206. (39) Majima, Y.; Hackenberger, G.; Azuma, Y.; Kano, S.; Matsuzaki, K.; Susaki, T.; Sakamoto, M.; Teranishi, T. Three-input gate logic circuits on chemically assembled single-electron transistors with organic and inorganic hybrid passivation layers. Sci. Technol. Adv. Mater. 2017, 18, 374. (40) Kano, S.; Tada, T.; Majima, Y. Nanoparticle characterization based on STM and STS. Chem. Soc. Rev. 2014, 44, 970.
5130
DOI: 10.1021/acsomega.8b00559 ACS Omega 2018, 3, 5125−5130
