Carbon nanotube-clamped metal atomic chain

Dai-Ming Tang; Li-Chang Yin; Feng Li; Chang Liu; Wan-Jing Yu; Peng-Xiang Hou; Bo Wu; Young-Hee Lee; Xiu-Liang Ma; Hui-Ming Cheng

doi:10.1073/pnas.0914970107

Edited* by Mildred Dresselhaus, Massachusetts Institute of Technology, Cambridge, MA, and approved March 29, 2010 (received for review December 30, 2009)
↵¹D.M.T. and L.C.Y. contributed equally to this work.

Abstract

Metal atomic chain (MAC) is an ultimate one-dimensional structure with unique physical properties, such as quantized conductance, colossal magnetic anisotropy, and quantized magnetoresistance. Therefore, MACs show great potential as possible components of nanoscale electronic and spintronic devices. However, MACs are usually suspended between two macroscale metallic electrodes; hence obvious technical barriers exist in the interconnection and integration of MACs. Here we report a carbon nanotube (CNT)-clamped MAC, where CNTs play the roles of both nanoconnector and electrodes. This nanostructure is prepared by in situ machining a metal-filled CNT, including peeling off carbon shells by spatially and elementally selective electron beam irradiation and further elongating the exposed metal nanorod. The microstructure and formation process of this CNT-clamped MAC are explored by both transmission electron microscopy observations and theoretical simulations. First-principles calculations indicate that strong covalent bonds are formed between the CNT and MAC. The electrical transport property of the CNT-clamped MAC was experimentally measured, and quantized conductance was observed.

Electron transport across a metal atomic chain (MAC) presents ultimate miniaturization and novel functionality of electronic devices (1–4). Several techniques, including scanning tunneling microscopy (STM) (5), mechanically controlled breaking junction (6), high resolution transmission electron microscopy (HRTEM) (7), self-terminated electrodeposition (8), and controlled electromigration (9), have been developed for the preparation of suspended MACs. However, how to connect and integrate the extremely small MACs remains a challenge, because the fabricated MACs are usually held between two macroscale electrodes. Carbon nanotube (CNT) is a one-dimensional tubular structure with intriguing electronic properties. Various CNT-based electronic devices, such as ballistic wire (10), field effect transistor (11), and logic circuit (12), have been demonstrated. It was recently reported by Rodríguez-Manzo et al. that CNTs can form strong covalent heterojunctions and interconnect with particles of different metals, by theoretical calculations and in situ TEM observation (13–15). Therefore, CNT can be a promising candidate for interconnecting and integrating MACs. Nevertheless, no such CNT-MAC structure is experimentally demonstrated yet.

In this study, we design and fabricate a unique CNT-MAC hybrid structure: CNT-clamped MAC. Our fabrication strategy is to fill a metal nanorod into a CNT, and then peel off the carbon shell surrounding the filled metal nanorod and thin the exposed metal nanorod by strong electron irradiation within a TEM. Finally, a CNT-clamped MAC is formed through further elongation and thinning by the strain existing in the TEM sample or by stretching using a TEM-STM holder.

Results and Discussion

The metal can be Fe, Co, Ni and their alloys that serve as the growth catalyst of CNTs and are encapsulated in situ (16, 17), or a variety of metals that are electrochemically deposited into CNTs by anodic aluminum oxide (AAO) template method (18). As an example, here we present the formation and structure of a CNT-clamped Fe AC. Firstly, Fe-filled CNTs were prepared by floating catalyst chemical vapour deposition (FCCVD) using ferrocene as catalyst precursor and acetylene as carbon source (16). Fig. 1A shows the TEM image of a CNT filled with a Fe nanorod. We can see that the outer and inner diameters of the CNT are about 25 nm and 10 nm, respectively. Selected area electron diffraction pattern (Fig. 1A, Inset) indicates that the filled Fe nanorod is single crystalline and body-center cubic (bcc) structured. When electron beam (with a current density of 100–300 A/cm²) was focused on the carbon shells surrounding the Fe nanorod, the CNT walls were removed element- and site-selectively (Fig. 1B) (19). And then the exposed Fe nanorod was further deformed and thinned, under strong electron irradiation. Because the energy of electron beam in our work (200 and 300 keV) is lower than the threshold energy (higher than 400 keV) for atom displacements from bulk Fe crystal lattices, the deformation and thinning are possibly due to electron irradiation induced surface sputtering effects and resulted surface diffusion (14, 20–22). During the thinning process, the Fe nanorod kept the single crystalline structure, with lattice corresponding to (110) clearly resolved (Fig. 1C). Finally, a CNT-clamped Fe nanorod was produced, as schematically shown in Fig. 1D.

Fig. 1.

Fabrication process of a CNT-clamped Fe nanorod. (A) TEM image of an original Fe-filled CNT. (Inset) Selected area electron diffraction pattern of the filled Fe nanorod. (B) TEM image showing that part of carbon shells surrounding the Fe nanorod are peeled off. (C) HRTEM image of the exposed Fe nanorod. (D) Schematic drawing of the CNT-clamped Fe nanorod.

When the diameter of the Fe nanorod was reduced to approximately 6 nm (Fig. 2 A and B), the intensity of the electron beam was decreased to a level normally used for TEM observations (10–30 A/cm²). The Fe nanorod was elongated and thinned spontaneously, possibly due to the strain existing in the TEM sample (23–25). Atomic steps are observed during the thinning process as marked by arrows in Fig. 2 C and D. Distortion is another deformation manner for the Fe nanorod (marked by dashed lines in Fig. 2 E and F). The fact that the distortion does not cause rupture indicates that the bending energy can be absorbed by the very fine nanorod (24). Fig. 2G shows that an Fe nanorod contains only 3 layers of Fe atoms, and a single-atom wide Fe AC is finally formed in Fig. 2H. This single-atom wide Fe AC is composed of 5 atoms with 3 atoms suspended, as schematically shown in Fig. 2I. The interatom distance at the center of the Fe AC is about 2.2 Å. The larger interatom distance of the Fe AC (compared with the interplane distance of bulk Fe(110) plane) is consistent with previous investigations on elementary (Au) (24, 26) and alloy (Au-Ag) ACs (27).

Fig. 2.

Formation of a single-atom wide Fe AC. (A)–(H) High resolution TEM images showing the formation process of the Fe AC. Atomic steps can be observed at the surface [marked by arrows in (C) and (D)]. Distortion along (110) is marked with dotted lines in (E). The scale bar is 2 nm. (I) Schematic drawing of the Fe AC shown in (H); the projected interatom distances are marked in Å.

First-principles calculation is effective in investigating the formation mechanism and physical properties of MACs (28–31). We used this method to simulate the formation process of Fe ACs and to explore the electronic structure of CNT-clamped Fe ACs. Our simulations start from a Fe nanorod oriented along [110] direction (Fig. 3AI), based on the results of the above HRTEM characterizations. This nanorod is elongated gradually along the axis direction with a step of 0.4 Å. Along with the elongation, the center atoms in the second and fourth layer extrude out (Fig. 3 A II–III). Then, the nanorod shows obvious distortion perpendicular to the [110] direction (Fig. 3 A III–IV), consistent with the experimentally observed slip of Fe (110) planes. The nanorod is elongated continuously and an AC emerges (Fig. 3 V–VI). The AC is stretched further as the elongation continues, and finally a single-atom wide Fe AC composed of 4 atoms forms (Fig. 3AVII) before rupture (Fig. 3AVIII). The interatom distances of the Fe AC were calculated to be 2.27, 2.24, and 2.30 Å, which are larger than the interplane distance of bulk Fe (110) plane, coinciding well with the TEM observations. Along with the structural evolution, we calculated the total binding energy of the Fe nanorod as a function of its length, and the results are shown in Fig. 3B. There are two abrupt drops in the total energy, corresponding to the slip along (110) and the final rupture. By slipping, stress can be released and the total energy is decreased. Therefore, both HRTEM observations and theoretical simulations indicate that the slip is an important deformation mode in the formation of a Fe AC.

Fig. 3.

DFT calculations on the formation process of Fe AC and electronic properties of CNT-clamped Fe AC. (A) Simulation on the structural evolution of the Fe AC. (I) The original [110] oriented Fe nanorod. (II) and (III) The center atoms in the second and fourth layer extruded out. (IV) Distortion along (110) occurs. (V)–(VII) Further elongation and formation of the single-atom wide Fe AC. (VIII) Rupture of the Fe AC. (B) The calculated total energy as a function of the nanorod length. The interatom distances and lengths of the nanorod are marked in Å. (C) Simulated structural model and the calculated density of states of the CNT-clamped Fe AC. (I) Fully relaxed ball-and-stick model of a CNT-clamped Fe AC. Carbon and iron atoms are marked in gray and blue, respectively. (II) Spin resolved total DOS for the CNT-clamped Fe AC. (III) and (IV) Spin resolved local DOS of the Fe AC and CNT. The red and blue lines denote the majority and minority states, respectively. And the Fermi energy (EF) is set to zero. (D) Charge density of two slices cut along the x and y axes. Strong covalent bonding is shown at the interface of the Fe AC and CNT.

To explore the electronic structure of CNT-clamped Fe ACs, we construct a (5, 5) single-walled carbon nanotube (SWCNT)-clamped Fe AC (the configuration of the Fe AC is determined from the simulated elongation of Fe nanorod as shown in Fig. 3AIII), and its fully relaxed structural model is shown in Fig. 3CI. The calculated total densities of states (DOS) (Fig. 3CII) indicate that the SWCNT-clamped Fe AC is metallic with an asymmetric distribution for majority and minority states near the Fermi energy (E_F) level. Fig. 3 CIII and 3CIV show the calculated local DOS for an Fe AC and SWCNT, respectively. The Fe AC behaves as a metal for majority states whereas it shows a band-gap of approximately 0.50 eV for its minority states. The local DOS of SWCNT shows symmetrical distribution for the majority and minority spin near the E_F. The charge densities of two slices along the x and y axes are plotted in Fig. 3D. Covalent bonding is clearly present at the interface between the SWCNT and Fe AC, which is consistent with the calculations and observations of the electronic structure of the junction between CNTs and metal particles (13). The average Fe-C bond length was calculated to be 2.06 Å, which is comparable to that of bulk Fe₃C (ranging from 1.90 to 2.06 Å) (32), indicating a strong connection between the SWCNT and Fe AC. To investigate the structure and electronic properties of an Fe AC clamped by larger CNTs with > 1 shells, we constructed and studied a double-walled carbon nanotube (DWCNT)-clamped Fe AC (Fig. S1). Covalent bonding was established at the interface of the Fe AC and the inner layer of DWCNT, with no obvious interaction between the Fe AC and the outer shell of DWCNT. In addition, spin resolved local DOS calculations found that the Fe AC is also half metallic. Therefore, our density functional theory (DFT) studies show that, after the hybridization and connection, the Fe AC forms a strong bonding with the inner layer of a CNT and retains its half-metallicity feature.

Having realized the connection of CNT and Fe AC, we further investigated the electronic conductance of the obtained CNT-clamped Fe AC in situ by using a TEM-STM holder. The experimental configurations of the fabrication and measurements are schematically shown in Fig. 4A. The detailed experimental procedure can be found in Materials and Methods. Briefly, an Fe-filled CNT is suspended between a gold STM tip and a gold wire. Then, strong electron beam is used to peel off the carbon shells and to thin the exposed Fe nanorod of the Fe-filled CNT. When the diameter of the Fe nanorod reaches several nanometers, the electron beam is reduced to a level for normal TEM observations and a tensile force is applied by retracting the STM tip gently with a speed of approximately 0.1 nm/s to form an Fe AC. Electrical conductance is measured at a constant bias of 12 mV simultaneously, along with the elongation, thinning and rupture of the Fe AC, with a recorded curve of conductance versus time shown in Fig. 4B. We can see that the conductance decreases in a stepwise way, and the conductance plateaus are found to be near integral multiples of 0.5G₀ (conductance quantum, which is 2e²/h ∼ (13 kΩ)^-1). The last plateau is about 2G₀, because the Fe nanorod ruptured before single-atom wide AC formed. Then, we reconnected the ruptured Fe nanorod and stretched it more slowly. In this case, stepwise-decreasing plateaus were also recorded, and the last plateau is around 0.5G₀, as shown in Fig. 4C. Quantized conductance for metal atomic contacts has been intensively studied (33). The conductance can be interpreted with the Landauer formula (G = G₀ΣT_i, where G₀ = 2e²/h, T_i is the transmission probability for the ith conductance channel) (34). For ferromagnetic metals, the conductance peaks are around integral multiples of 0.5G₀, rather than G₀ for nonmagnetic metals such as gold (1, 2) and alkali metals (35), due to the lack of spin degeneracy (3, 8, 36, 37). Therefore, the conductance plateaus in our work can be interpreted as quantized conductance of ferromagnetic metal (Fe), and the conductance steps are ascribed to structural rearrangements during elongation. The plateaus are not always at the integral multiples of 0.5G₀, which was also found previously for other metals, and this can be understood because the transmission probability is not always one for one conductance channel (33, 37). The plateaus last at a time scale of several seconds, therefore the current dependence on bias voltage (I–V characteristic) could be measured when suspending the elongation process, as shown in Fig. S2. When the contact is about 0.75 nm in width, corresponding to 3 to 4 Fe atomic layers, the I–V curve is almost linear within the measurement voltage range (-0.5 to 0.5 V), with a calculated conductance of about 1.5G₀. Previous studies have shown that contamination of gas adsorption may lead to nonlinear behavior for metal nanocontacts (38), so the linear behavior observed in this study indicates that the conductance is Ohmic (37) and the contact is clean (8). The above results show that after the connection and assembly with CNT, the MACs could well retain their unique electrical transport properties, such as quantized conductance.

Fig. 4.

In situ electrical transport measurements of a CNT-clamped Fe AC. (A) Schematic diagram of the experimental process. (B) and (C) Conductance changes as a function of time for two formation and thinning processes of Fe ACs at a constant bias of 12 mV, where the contact ruptured comparatively abruptly in (B) and smoothly in (C).

In addition to the CNT-clamped Fe AC, we also applied the above fabrication philosophy to other metals and alloys. For example, Pt-filled CNTs and Fe-Ni alloy-filled CNTs were produced by an AAO template and chlorine-promoted FCCVD method, respectively. CNT-clamped Pt and Fe-Ni alloy ACs were successfully fabricated by an approach similar to the fabrication of the Fe AC as described above (Fig. S3, Fig. S4, Fig. S5, and Fig. S6). DFT calculations also confirmed that both the Pt and Co ACs can form strong connection with CNTs (Fig. S7 and Fig. S8). Therefore, a variety of metals are applicable for the fabrication of CNT-clamped MACs.

To sum up, we design and fabricate CNT-clamped MACs, which can provide a general approach for the interconnection and integration of MACs with CNTs. The formation process of CNT-clamped MACs was explored by both in situ TEM observations and first-principles calculations. Electronic structure calculations indicate that strong covalent bonds are formed at the CNT/MAC interface. The intriguing properties of Fe ACs, such as half-metallicity and quantized conductance, are retained after the combination of Fe ACs and CNTs. The strategy we proposed is effective in fabricating a variety of MACs and in situ connecting these MACs with CNTs, thus it may find potential applications in the assembly of nano/subnano devices.

Materials and Methods

1 Synthesis of Metal-Filled CNTs.

Fe and Fe alloy-filled CNTs were produced by FCCVD method (16, 17). Pt-filled CNTs were produced by AAO template method. More details can be found in the SI Text.

2 Fabrication of CNT-Clamped MACs.

Two methods were used for the fabrication of CNT-clamped MACs. The first one is HRTEM method developed by Kondo et al. (7). It was done under Tecnai G² F30 or F20 TEMs, using metal nanorod-filled CNTs as starting materials. Focused electron beam was used to peel off the carbon shells by knocking-on effects (19) and to deform and thin the exposed metal nanorod by surface sputtering and diffusion effects (14, 20–22) in the initial stage. When the diameter of the nanorod was reduced to approximately 6 nm, the electron beam density was decreased to normal level for HRTEM observations. The nanorod was elongated and thinned gradually by the strain in the TEM sample grid (23–25) to form CNT-clamped MACs. The images were taken by using CCD camera (Gatan Ultrascan 894) with an exposure time of 0.5 s.

The second method is in situ TEM-STM developed by Ohnishi et al. (1) using a Nanofactory holder. Metal-filled CNTs were adhered to a gold wire of 0.25 mm in diameter by simply touching the samples with a cleanly cut edge. To avoid organic contaminations, no conductive clue was used. A gold STM tip, prepared by electrochemical etching, was manipulated by a piezo-electric tube to touch the metal-filled CNTs. Then a bias was applied between the STM tip and the CNT to anneal the sample. The purpose of the annealing is to desorb possible adsorbed gases and get Ohmic contact between the CNT and the STM tip. The current was controlled to be around 10 μA, by tuning the bias. Current voltage characteristics of the system at different stages are shown in Fig. S9. When the STM tip just touches the sample, only noise current < 2 nA can be measured, due to a thin inert layer on the tip. During the annealing process, a nonlinear behavior is revealed and can be ascribed to the Schottky barrier between the tip and the CNT. After annealing, an almost linear behavior is demonstrated, and the conductance is around 1G₀ after annealing, which is used as the resistance for correction, when the conductance of the CNT-clamped MAC is calculated. Simultaneously, it is found that the CNT is welded to the STM tip. The bias is also calibrated after the annealing process. It was found that for our electronics, the zero potential corresponds to about 18 mV. Therefore, when calculating conductance, the bias should be corrected, accordingly. After that, similar to the HRTEM method, strong electron irradiation was used to peel off the carbon shells, by focusing the electron beam probe to be around 100 nm and swiping around the targeted area. To avoid high temperature reactions and unwanted phase transitions, the bias was set to be zero. Electron beam was also used to thin the exposed Fe nanorod, similar to the first fabrication method. When the Fe nanorod was thinned to be around 6 nm, the electron beam intensity was reduced to normal level for HRTEM observations. The Fe nanorod got further elongated and thinned until breaking, by retracting the STM tip gently at a speed of about 0.1 nm/s. After the first rupture, the broken nanorod could be reconnected and subjected to the second elongation and thinning. Along with the fabrication of the Fe ACs by retraction, the conductance was recorded with a constant bias.

3 In situ electronic conductance measurement.

The conductance change against the time was measured along with the retraction of the STM tip. The bias was set to be a constant of 12 mV (after calibration), and the sampling rate was 2 kHz. The conductance dependence on bias voltage was measured when suspending the elongation process. The conductance of the CNT-clamped MAC was calculated with correction using the resistance after the structure annealing, using the following formula where G is the conductance with a unit of G₀ (conductance quantum), V and I are bias applied and current measured, V₀ (18 mV for our system) is the calibrated zero bias point, R₀ is the resistance of the system after annealing, and (13 kΩ)^-1 corresponding to one conductance quantum.

4 First-principles calculations and simulation methods.

We used the accurate frozen-core full-potential projector augmented-wave method (39), implemented in the Vienna ab initio simulation package (40). The calculations were based on DFT with the electronic exchange and correlation effects described by the generalized gradient approximation (41). We adopted periodic boundary conditions and placed a bcc Fe [110] oriented nanorod consisting of 5 atomic layers involving 22 atoms in a 12 Å × 11 Å × 16 Å supercell. To improve convergence in the case of partially occupied eigenstates at the Fermi level, a modest Gaussian smearing of σ = 0.05 eV was used. We used an energy cutoff of 350 eV for the plane-wave basis set and a cutoff of 1000 eV for the augmentation charges. The binding energies were computed by taking an isolated spherical atom as a reference with a total magnetic moment of according to Hund’s rule. For bulk bcc Fe, the lattice constant and total magnetic moment were calculated to be 2.83 Å and , respectively, close to the corresponding experimental values of 2.87 Å and .

To simulate the formation process of the Fe AC, the nanorod was elongated along [110] direction by a step of 0.4 Å, meanwhile, the super cell was prolonged by the same step in [110] direction to keep the separate distance between the periodic images. At each step, symmetry-unrestricted geometry and spin optimizations were performed using conjugated gradient and quasi-Newtonian methods, except for the 8 Fe atoms located at the two end layers of the nanorod, of which the coordinates along the [110] axis are fixed, until all the force components except for those constrained ones were less than a threshold value of 0.01 eV/Å.

A periodic geometry, which was constructed by connecting a (5, 5) SWCNT composed of 160 carbon atoms with a fully optimized Fe AC obtained during above elongation process in a 15 Å × 15 Å × 29.6 Å supercell, was adopted to investigate the atomic and electronic structure of CNT-clamped Fe AC. A fully geometry relaxation was performed at the Γ-point only by minimizing the Hellmann–Feynman forces on the atoms and stresses on the supercell, until all the forces on each atom were smaller than 0.05 eV/Å.

Pt or Co AC was obtained by using the same elongation process as that for Fe AC with the initial Pt (Co) nanorod along [111] ([001]). The initial Pt (Co) nanorod consists of 123 (96) atoms. Locally stable Pt (28.4 Å) and Co (24.2 Å) ACs obtained during the elongation were selected to connect with a (8, 8) and (6, 6) SWCNT, respectively. CNT-clamped Pt (Co) AC was obtained after geometry optimization. The charge density plots of these two CNT-clamped MACs presented covalent bonding at the interface between CNT and Pt (Co) AC with an average bonding length of 2.00 (1.96) Å.

Acknowledgments

We acknowledge helpful discussions with Prof. Zhong Lin Wang, Prof. R. Saito, Dr. Oleg Lourie, Dr. Kui Du, Dr. Cheng-Hua Sun, and Prof. Wei Liu. We thank Dr. Rui-Tao Lv, Dr. Qing-Feng Liu, and Ms. Chun-Xiang Shi for providing Fe- and alloy-filled CNT samples. We thank Dr. Chuan-Bin Jiang for TEM support. H.M.C. and C.L. acknowledge financial support from Ministry of Science and Technology of China Grants 2008DFA51400, 2006CB932701, and 2006CB932703, and National Natural Science Foundation of China Grants 90606008, 50672103, and 50921004. F.L. and L.C.Y. acknowledge support from the Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences. Y.H.L. acknowledges support from the STAR faculty project and World Class University program through the National Research Foundation funded by the Ministry of Education, Science, and Technology of Korea (R31-2008-000-10029-0).

Footnotes

²To whom correspondence may be addressed. E-mail: cliu{at}imr.ac.cn or cheng{at}imr.ac.cn.
Author contributions: D.-M.T., L.-C.Y., F.L., C.L., and H.-M.C. designed research; D.-M.T. and L.-C.Y. performed research; W.-J.Y., P.-X.H., and B.W. contributed new reagents/analytic tools; D.-M.T., L.-C.Y., F.L., C.L., Y.H.L., X.-L.M., and H.-M.C. analyzed data; and D.-M.T., L.-C.Y., F.L., C.L., and H.-M.C. wrote the paper.
The authors declare no conflict of interest.
*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.0914970107/-/DCSupplemental.

References

↵
1. Ohnishi H,
2. Kondo Y,
3. Takayanagi K
(1998) Quantized conductance through individual rows of suspended gold atoms. Nature 395:780–783.
OpenUrl CrossRef
↵
1. Yanson AI,
2. Bollinger GR,
3. van den Brom HE,
4. Agrait N,
5. van Ruitenbeek JM
(1998) Formation and manipulation of a metallic wire of single gold atoms. Nature 395:783–785.
OpenUrl CrossRef
↵
1. Sokolov A,
2. Zhang CJ,
3. Tsymbal EY,
4. Redepenning J,
5. Doudin B
(2007) Quantized magnetoresistance in atomic-size contacts. Nat Nanotechnol 2:171–175.
OpenUrl CrossRef PubMed
↵
1. Smogunov A,
2. Dal Corso A,
3. Delin A,
4. Weht R,
5. Tosatti E
(2008) Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires. Nat Nanotechnol 3:22–25.
OpenUrl CrossRef PubMed
↵
1. Agrait N,
2. Rodrigo JG,
3. Vieira S
(1993) Conductance steps and quantization in atomic-size contacts. Phys Rev B 47:12345–12348.
OpenUrl CrossRef
↵
1. Muller CJ,
2. Vanruitenbeek JM,
3. Dejongh LJ
(1992) Conductance and supercurrent discontinuities in atomic-scale metallic constrictions of variable width. Phys Rev Lett 69:140–143.
OpenUrl CrossRef PubMed
↵
1. Kondo Y,
2. Takayanagi K
(1997) Gold nanobridge stabilized by surface structure. Phys Rev Lett 79:3455–3458.
OpenUrl CrossRef
↵
1. Chopra HD,
2. Sullivan MR,
3. Armstrong JN,
4. Hua SZ
(2005) The quantum spin-valve in cobalt atomic point contacts. Nat Mater 4:832–837.
OpenUrl CrossRef
↵
1. Bolotin KI,
2. Kuemmeth F,
3. Ralph DC
(2006) Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions. Phys Rev Lett 97:127202.
OpenUrl CrossRef PubMed
↵
1. White CT,
2. Todorov TN
(1998) Carbon nanotubes as long ballistic conductors. Nature 393:240–242.
OpenUrl CrossRef
↵
1. Tans SJ,
2. Verschueren ARM,
3. Dekker C
(1998) Room-temperature transistor based on a single carbon nanotube. Nature 393:49–52.
OpenUrl CrossRef
↵
1. Bachtold A,
2. Hadley P,
3. Nakanishi T,
4. Dekker C
(2001) Logic circuits with carbon nanotube transistors. Science 294:1317–1320.
OpenUrl Abstract/FREE Full Text
↵
1. Rodríguez-Manzo JA,
2. et al.
(2009) Heterojunctions between metals and carbon nanotubes as ultimate nanocontacts. Proc Natl Acad Sci USA 106:4591–4595.
OpenUrl Abstract/FREE Full Text
↵
1. Rodriguez-Manzo JA,
2. et al.
(2009) Growth of single-walled carbon nanotubes from sharp metal tips. Small 5:2710–2715.
OpenUrl CrossRef PubMed
↵
1. Rodriguez-Manzo JA,
2. Wang MS,
3. Banhart F,
4. Bando Y,
5. Golberg D
(2009) Multibranched junctions of carbon nanotubes via cobalt particles. Adv Mater 21:4477–4482.
OpenUrl CrossRef
↵
1. Cheng HM,
2. et al.
(1998) Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons. Appl Phys Lett 72:3282–3284.
OpenUrl CrossRef
↵
1. Lv RT,
2. et al.
(2007) Effect of using chlorine-containing precursors in the synthesis of feni-filled carbon nanotubes. Carbon 45:1433–1438.
OpenUrl CrossRef
↵
1. Kyotani T,
2. Pradhan BK,
3. Tomita A
(1999) Synthesis of carbon nanotube composites in nanochannels of an anodic aluminum oxide film. Bull Chem Soc Jpn 72:1957–1970.
OpenUrl CrossRef
↵
1. Banhart F
(1999) Irradiation effects in carbon nanostructures. Rep Prog Phys 62:1181–1221.
OpenUrl CrossRef
↵
1. Egerton RF,
2. Li P,
3. Malac M
(2004) Radiation damage in the TEM and SEM. Micron 35:399–409.
OpenUrl CrossRef PubMed
↵
1. Egerton RF,
2. Wang F,
3. Crozier PA
(2006) Beam-induced damage to thin specimens in an intense electron probe. Microsc Microanal 12:65–71.
OpenUrl CrossRef PubMed
↵
1. Williams DB,
2. Carter CB
(2009) Transmission Electron Microscopy a Textbook for Materials Science (Springer, US), 2 Ed.
↵
1. Rodrigues V,
2. Fuhrer T,
3. Ugarte D
(2000) Signature of atomic structure in the quantum conductance of gold nanowires. Phys Rev Lett 85:4124–4127.
OpenUrl CrossRef PubMed
↵
1. Rodrigues V,
2. Ugarte D
(2001) Real-time imaging of atomistic process in one-atom-thick metal junctions. Phys Rev B 63:073405.
OpenUrl CrossRef
↵
1. Rego LGC,
2. Rocha AR,
3. Rodrigues V,
4. Ugarte D
(2003) Role of structural evolution in the quantum conductance behavior of gold nanowires during stretching. Phys Rev B 67:045412.
OpenUrl CrossRef
↵
1. Bahn SR,
2. Jacobsen KW
(2001) Chain formation of metal atoms. Phys Rev Lett 87:266101.
OpenUrl CrossRef PubMed
↵
1. Bettini J,
2. et al.
(2006) Experimental realization of suspended atomic chains composed of different atomic species. Nat Nanotechnol 1:182–185.
OpenUrl CrossRef PubMed
↵
1. Delin A,
2. Tosatti E
(2004) The electronic structure of 4d transition-metal monatomic wires. J Phys-Condens Mat 16:8061–8074.
OpenUrl
↵
1. Delin A,
2. Tosatti E
(2003) Magnetic phenomena in 5d transition metal nanowires. Phys Rev B 68:144434.
OpenUrl CrossRef
↵
1. Tung JC,
2. Guo GY
(2007) Systematic ab initio study of the magnetic and electronic properties of all 3d transition metal linear and zigzag nanowires. Phys Rev B 76:094413.
OpenUrl CrossRef
↵
1. Lucignano P,
2. Mazzarello R,
3. Smogunov A,
4. Fabrizio M,
5. Tosatti E
(2009) Kondo conductance in an atomic nanocontact from first principles. Nat Mater 8:563–567.
OpenUrl CrossRef PubMed
↵
1. Wood IG,
2. et al.
(2004) Thermal expansion and crystal structure of cementite, fe3c, between 4 and 600 k determined by time-of-flight neutron powder diffraction. J Appl Crystallogr 37:82–90.
OpenUrl CrossRef
↵
1. Agraït N,
2. Yeyati AL,
3. van Ruitenbeek JM
(2003) Quantum properties of atomic-sized conductors. Phys Rep 377:81–279.
OpenUrl CrossRef
↵
1. Landauer R
(1970) Electrical resistance of disordered one-dimensional lattices. Philos Mag 21:863–867.
OpenUrl
↵
1. Krans JM,
2. Vanruitenbeek JM,
3. Fisun VV,
4. Yanson IK,
5. Dejongh LJ
(1995) The signature of conductance quantization in metallic point contacts. Nature 375:767–769.
OpenUrl CrossRef
↵
1. Rodrigues V,
2. Bettini J,
3. Silva PC,
4. Ugarte D
(2003) Evidence for spontaneous spin-polarized transport in magnetic nanowires. Phys Rev Lett 91:096801.
OpenUrl CrossRef PubMed
↵
1. Komori F,
2. Nakatsuji K
(1999) Quantized conductance through atomic-sized iron contacts at 4.2 k. J Phys Soc Jpn 68:3786–3789.
OpenUrl CrossRef
↵
1. Mehrez H,
2. et al.
(2002) I-V characteristics and differential conductance fluctuations of au nanowires. Phys Rev B 65:195419.
OpenUrl CrossRef
↵
1. Blöchl PE
(1994) Projector augmented-wave method. Phys Rev B 50:17953.
OpenUrl CrossRef
↵
1. Kresse G,
2. Furthmüllerr J
(1996) Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys Rev B 54:11169.
OpenUrl CrossRef
↵
1. Wang Y,
2. Perdew JP
(1991) Correlation hole of the spin-polarized electron gas, with exact small-wave-vector and high-density scaling. Phys Rev B 44:13298.
OpenUrl CrossRef

Article Alerts

Email Article

Citation Tools

Request Permissions

Article Classifications

Physical Sciences
Engineering

Proceedings of the National Academy of Sciences: 107 (20)

Table of Contents

Submit

[1] ↵
Ohnishi H,
Kondo Y,
Takayanagi K
(1998) Quantized conductance through individual rows of suspended gold atoms. Nature 395:780–783.
OpenUrl CrossRef

[2] Ohnishi H,

[3] Kondo Y,

[4] Takayanagi K

[5] ↵
Yanson AI,
Bollinger GR,
van den Brom HE,
Agrait N,
van Ruitenbeek JM
(1998) Formation and manipulation of a metallic wire of single gold atoms. Nature 395:783–785.
OpenUrl CrossRef

[6] Yanson AI,

[7] Bollinger GR,

[8] van den Brom HE,

[9] Agrait N,

[10] van Ruitenbeek JM

[11] ↵
Sokolov A,
Zhang CJ,
Tsymbal EY,
Redepenning J,
Doudin B
(2007) Quantized magnetoresistance in atomic-size contacts. Nat Nanotechnol 2:171–175.
OpenUrl CrossRef PubMed

[12] Sokolov A,

[13] Zhang CJ,

[14] Tsymbal EY,

[15] Redepenning J,

[16] Doudin B

[17] ↵
Smogunov A,
Dal Corso A,
Delin A,
Weht R,
Tosatti E
(2008) Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires. Nat Nanotechnol 3:22–25.
OpenUrl CrossRef PubMed

[18] Smogunov A,

[19] Dal Corso A,

[20] Delin A,

[21] Weht R,

[22] Tosatti E

[23] ↵
Agrait N,
Rodrigo JG,
Vieira S
(1993) Conductance steps and quantization in atomic-size contacts. Phys Rev B 47:12345–12348.
OpenUrl CrossRef

[24] Agrait N,

[25] Rodrigo JG,

[26] Vieira S

[27] ↵
Muller CJ,
Vanruitenbeek JM,
Dejongh LJ
(1992) Conductance and supercurrent discontinuities in atomic-scale metallic constrictions of variable width. Phys Rev Lett 69:140–143.
OpenUrl CrossRef PubMed

[28] Muller CJ,

[29] Vanruitenbeek JM,

[30] Dejongh LJ

[31] ↵
Kondo Y,
Takayanagi K
(1997) Gold nanobridge stabilized by surface structure. Phys Rev Lett 79:3455–3458.
OpenUrl CrossRef

[32] Kondo Y,

[33] Takayanagi K

[34] ↵
Chopra HD,
Sullivan MR,
Armstrong JN,
Hua SZ
(2005) The quantum spin-valve in cobalt atomic point contacts. Nat Mater 4:832–837.
OpenUrl CrossRef

[35] Chopra HD,

[36] Sullivan MR,

[37] Armstrong JN,

[38] Hua SZ

[39] ↵
Bolotin KI,
Kuemmeth F,
Ralph DC
(2006) Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions. Phys Rev Lett 97:127202.
OpenUrl CrossRef PubMed

[40] Bolotin KI,

[41] Kuemmeth F,

[42] Ralph DC

[43] ↵
White CT,
Todorov TN
(1998) Carbon nanotubes as long ballistic conductors. Nature 393:240–242.
OpenUrl CrossRef

[44] White CT,

[45] Todorov TN

[46] ↵
Tans SJ,
Verschueren ARM,
Dekker C
(1998) Room-temperature transistor based on a single carbon nanotube. Nature 393:49–52.
OpenUrl CrossRef

[47] Tans SJ,

[48] Verschueren ARM,

[49] Dekker C

[50] ↵
Bachtold A,
Hadley P,
Nakanishi T,
Dekker C
(2001) Logic circuits with carbon nanotube transistors. Science 294:1317–1320.
OpenUrl Abstract/FREE Full Text

[51] Bachtold A,

[52] Hadley P,

[53] Nakanishi T,

[54] Dekker C

[55] ↵
Rodríguez-Manzo JA,
et al.
(2009) Heterojunctions between metals and carbon nanotubes as ultimate nanocontacts. Proc Natl Acad Sci USA 106:4591–4595.
OpenUrl Abstract/FREE Full Text

[56] Rodríguez-Manzo JA,

[57] et al.

[58] ↵
Rodriguez-Manzo JA,
et al.
(2009) Growth of single-walled carbon nanotubes from sharp metal tips. Small 5:2710–2715.
OpenUrl CrossRef PubMed

[59] Rodriguez-Manzo JA,

[60] et al.

[61] ↵
Rodriguez-Manzo JA,
Wang MS,
Banhart F,
Bando Y,
Golberg D
(2009) Multibranched junctions of carbon nanotubes via cobalt particles. Adv Mater 21:4477–4482.
OpenUrl CrossRef

[62] Rodriguez-Manzo JA,

[63] Wang MS,

[64] Banhart F,

[65] Bando Y,

[66] Golberg D

[67] ↵
Cheng HM,
et al.
(1998) Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons. Appl Phys Lett 72:3282–3284.
OpenUrl CrossRef

[68] Cheng HM,

[69] et al.

[70] ↵
Lv RT,
et al.
(2007) Effect of using chlorine-containing precursors in the synthesis of feni-filled carbon nanotubes. Carbon 45:1433–1438.
OpenUrl CrossRef

[71] Lv RT,

[72] et al.

[73] ↵
Kyotani T,
Pradhan BK,
Tomita A
(1999) Synthesis of carbon nanotube composites in nanochannels of an anodic aluminum oxide film. Bull Chem Soc Jpn 72:1957–1970.
OpenUrl CrossRef

[74] Kyotani T,

[75] Pradhan BK,

[76] Tomita A

[77] ↵
Banhart F
(1999) Irradiation effects in carbon nanostructures. Rep Prog Phys 62:1181–1221.
OpenUrl CrossRef

[78] Banhart F

[79] ↵
Egerton RF,
Li P,
Malac M
(2004) Radiation damage in the TEM and SEM. Micron 35:399–409.
OpenUrl CrossRef PubMed

[80] Egerton RF,

[81] Li P,

[82] Malac M

[83] ↵
Egerton RF,
Wang F,
Crozier PA
(2006) Beam-induced damage to thin specimens in an intense electron probe. Microsc Microanal 12:65–71.
OpenUrl CrossRef PubMed

[84] Egerton RF,

[85] Wang F,

[86] Crozier PA

[87] ↵
Williams DB,
Carter CB
(2009) Transmission Electron Microscopy a Textbook for Materials Science (Springer, US), 2 Ed.

[88] Williams DB,

[89] Carter CB

[90] ↵
Rodrigues V,
Fuhrer T,
Ugarte D
(2000) Signature of atomic structure in the quantum conductance of gold nanowires. Phys Rev Lett 85:4124–4127.
OpenUrl CrossRef PubMed

[91] Rodrigues V,

[92] Fuhrer T,

[93] Ugarte D

[94] ↵
Rodrigues V,
Ugarte D
(2001) Real-time imaging of atomistic process in one-atom-thick metal junctions. Phys Rev B 63:073405.
OpenUrl CrossRef

[95] Rodrigues V,

[96] Ugarte D

[97] ↵
Rego LGC,
Rocha AR,
Rodrigues V,
Ugarte D
(2003) Role of structural evolution in the quantum conductance behavior of gold nanowires during stretching. Phys Rev B 67:045412.
OpenUrl CrossRef

[98] Rego LGC,

[99] Rocha AR,

[100] Rodrigues V,

[101] Ugarte D

[102] ↵
Bahn SR,
Jacobsen KW
(2001) Chain formation of metal atoms. Phys Rev Lett 87:266101.
OpenUrl CrossRef PubMed

[103] Bahn SR,

[104] Jacobsen KW

[105] ↵
Bettini J,
et al.
(2006) Experimental realization of suspended atomic chains composed of different atomic species. Nat Nanotechnol 1:182–185.
OpenUrl CrossRef PubMed

[106] Bettini J,

[107] et al.

[108] ↵
Delin A,
Tosatti E
(2004) The electronic structure of 4d transition-metal monatomic wires. J Phys-Condens Mat 16:8061–8074.
OpenUrl

[109] Delin A,

[110] Tosatti E

[111] ↵
Delin A,
Tosatti E
(2003) Magnetic phenomena in 5d transition metal nanowires. Phys Rev B 68:144434.
OpenUrl CrossRef

[112] Delin A,

[113] Tosatti E

[114] ↵
Tung JC,
Guo GY
(2007) Systematic ab initio study of the magnetic and electronic properties of all 3d transition metal linear and zigzag nanowires. Phys Rev B 76:094413.
OpenUrl CrossRef

[115] Tung JC,

[116] Guo GY

[117] ↵
Lucignano P,
Mazzarello R,
Smogunov A,
Fabrizio M,
Tosatti E
(2009) Kondo conductance in an atomic nanocontact from first principles. Nat Mater 8:563–567.
OpenUrl CrossRef PubMed

[118] Lucignano P,

[119] Mazzarello R,

[120] Smogunov A,

[121] Fabrizio M,

[122] Tosatti E

[123] ↵
Wood IG,
et al.
(2004) Thermal expansion and crystal structure of cementite, fe3c, between 4 and 600 k determined by time-of-flight neutron powder diffraction. J Appl Crystallogr 37:82–90.
OpenUrl CrossRef

[124] Wood IG,

[125] et al.

[126] ↵
Agraït N,
Yeyati AL,
van Ruitenbeek JM
(2003) Quantum properties of atomic-sized conductors. Phys Rep 377:81–279.
OpenUrl CrossRef

[127] Agraït N,

[128] Yeyati AL,

[129] van Ruitenbeek JM

[130] ↵
Landauer R
(1970) Electrical resistance of disordered one-dimensional lattices. Philos Mag 21:863–867.
OpenUrl

[131] Landauer R

[132] ↵
Krans JM,
Vanruitenbeek JM,
Fisun VV,
Yanson IK,
Dejongh LJ
(1995) The signature of conductance quantization in metallic point contacts. Nature 375:767–769.
OpenUrl CrossRef

[133] Krans JM,

[134] Vanruitenbeek JM,

[135] Fisun VV,

[136] Yanson IK,

[137] Dejongh LJ

[138] ↵
Rodrigues V,
Bettini J,
Silva PC,
Ugarte D
(2003) Evidence for spontaneous spin-polarized transport in magnetic nanowires. Phys Rev Lett 91:096801.
OpenUrl CrossRef PubMed

[139] Rodrigues V,

[140] Bettini J,

[141] Silva PC,

[142] Ugarte D

[143] ↵
Komori F,
Nakatsuji K
(1999) Quantized conductance through atomic-sized iron contacts at 4.2 k. J Phys Soc Jpn 68:3786–3789.
OpenUrl CrossRef

[144] Komori F,

[145] Nakatsuji K

[146] ↵
Mehrez H,
et al.
(2002) I-V characteristics and differential conductance fluctuations of au nanowires. Phys Rev B 65:195419.
OpenUrl CrossRef

[147] Mehrez H,

[148] et al.

[149] ↵
Blöchl PE
(1994) Projector augmented-wave method. Phys Rev B 50:17953.
OpenUrl CrossRef

[150] Blöchl PE

[151] ↵
Kresse G,
Furthmüllerr J
(1996) Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys Rev B 54:11169.
OpenUrl CrossRef

[152] Kresse G,

[153] Furthmüllerr J

[154] ↵
Wang Y,
Perdew JP
(1991) Correlation hole of the spin-polarized electron gas, with exact small-wave-vector and high-density scaling. Phys Rev B 44:13298.
OpenUrl CrossRef

[155] Wang Y,

[156] Perdew JP

Main menu

User menu

Search

Carbon nanotube-clamped metal atomic chain

Abstract

Results and Discussion

Materials and Methods

1 Synthesis of Metal-Filled CNTs.

2 Fabrication of CNT-Clamped MACs.

3 In situ electronic conductance measurement.

4 First-principles calculations and simulation methods.

Acknowledgments

Footnotes

References

Citation Manager Formats

Article Classifications

You May Also be Interested in

Similar Articles

Articles

PNAS Portals

Information

Main menu

User menu

Search

Abstract

Results and Discussion

Materials and Methods

1 Synthesis of Metal-Filled CNTs.

2 Fabrication of CNT-Clamped MACs.

3 In situ electronic conductance measurement.

4 First-principles calculations and simulation methods.

Acknowledgments

Footnotes

References

Citation Manager Formats

Article Classifications

Sign up for Article Alerts

Jump to section

You May Also be Interested in

Similar Articles

Articles

PNAS Portals

Information