Carbon-based nanodevices for sensors, actuators and electronics

Carbon-based Nanodevices for Sensors, Actuators and Electronics

E. H. Yanga*, S. Straufa, F. Fishera, and D. S. Choib

aStevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ, USA, 07030-5991;

bUniversity of Idaho, 875 Perimeter Drive, Moscow, ID, USA, 83844-2282

ABSTRACT

We are pursuing several projects aimed at developing carbon-based nanodevices for sensing, actuation, and nanoelectronics applications. In one project, we are seeking to fabricate and characterize carbon nanotube quantum dots (CNT-QDs) with potential application as future electronic memories with high-performance, bandwidth, and throughput. In a second effort, we have used pulsed laser deposition (PLD) to create thermal bimorph nanoactuators based on multi-wall nano tubes (MWNTs) coated on one side with a thin metal film. Lastly, graphene materials are being studied to investigate its field emission properties for vacuum electronics and to exploit its differential conductivity. These devices have potential in a wide range of applications including sensors, detectors, system-on-a-chip, system-in-a-package, programmable logic controls, energy storage systems and all-electronic systems.

INTRODUCTION

In the future, information processing will require the handling of orders of magnitude more data at several hundred times higher throughput than currently possible with state-of-the-art microelectronics systems. New analog and digital electronic devices operating at the level of single electrons are considered strong candidates to replace or complement silicon transistors in future ultra-dense, low-power, high-speed electronics. For example, the ability to process, analyze, distribute, and act upon sensors and other information data at very high speed will be necessary to realize the full benefit of distributed smart sensor networks in numerous civilian and military applications. Future high-throughput processors will provide high speed computing power such as survivability processors, which integrate, manage, deploy, or apply the other subsystems and perform threat identification and characterization, saliency, immediacy, and response/consequence assessment calculations. For example, Unmanned Aerial Vehicles (UAVs) and bio-chemical-radiation sensors will demand very high-speed processing of complex sensor signals with low

* Contact and lead author

Invited Paper

Micro- and Nanotechnology Sensors, Systems, and Applications, edited by Thomas George, M. Saif Islam, Achyut K. Dutta,Proc. of SPIE Vol. 7318, 731813 · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.817758

Proc. of SPIE Vol. 7318 731813-1

power consumption and small size, which will benefit from the integration of nanometer-sized sensing elements coupled to nanoelectronics with very high-speed processing capability. Such future computing requirements need the development of orders of magnitude faster processors, memory storages and communication bandwidths, and distributed command and control algorithms. While recent advances in materials and processing methods have led to the development of faster processors and high-speed memories, it is anticipated that future technological breakthroughs in these areas will increasingly be driven by technological advances in Nanoelectronics.

Progress in the fabrication, assembly, manipulation, and characterization of carbon nanotube and graphene-based nanodevices hold promise in applications such as sensors, detectors, system-on-a-chip, energy storage systems, and high-speed electronics. Next generation electronics will significantly increase the capabilities of high-throughput information systems, while simultaneously decreasing their size, weight, cost, and assembly complexity. The outstanding electrical properties of both carbon nanotubes (CNTs) [1] and graphene [2] make them exceptional candidates for the development of novel devices with orders-of-magnitude increases in functionality and efficiency in comparison to the current state-of-the-art. While CNTs possess superior properties in comparison to Si-based structures, another extraordinary carbon nanomaterial, graphene, also has superior electronic properties with enormous potential to facilitate new nanoelectronic devices operating at a level of individual electrons. In addition, graphene has enormous potential as a chemical sensor, capable of detecting minute concentrations (1 part per billion) of various active gases, allowing for the detection of individual events. Importantly, the planar form of Graphene allows for top-down CMOS compatible process flows, an advantage for potential industrial fabrication of electronic devices. Graphene has already been used in laboratory demonstrations of a spin valve, an electromechanical resonator, a quantum interference device, and, significantly, a field-effect transistor (FET). However, despite the promise of vastly superior performance of CNT and graphene-based devices, several fundamental issues in the fabrication and characterization of such devices need to be resolved to realize their full potential. In this regard we are investigating nanodevices based on CNT and graphene nanostructures aimed at developing nanoelectronic devices, nanoactuator systems and nanosensors for cross-disciplinary applications.

CARBON NANOTUBE QUANTUM DOTS

For example, we are pursuing nano-segmented, in-plane grown CNT structures and investigating their quantized electron energy properties for nanoelectronics applications. The inexorable scaling trend in electronics has resulted in the number of electrons participating in device operations being continuously reduced, which will ultimately require single-electron device operation. Foreseeing this trend towards single electron operation, Averin and Likharev proposed a three-terminal, single-electron tunneling structure, consisting of just one small conducting island separated from two larger electrodes (electron sources) by two quantum-mechanical tunneling barriers [3]. Electrons at the Fermi energy level can tunnel from the leads onto the islands even though in classical terms their energy would be too low to overcome the potential barrier. In contrast to earlier studies of individual tunnel junctions allowing single electron tunneling processes, the double barriers described by Averin and Likharev form a QD-like nanostructure with distinct internal energy states. Since the number of electrons on the island is a function of the applied gate voltage,


the QD structures can be used for controlled storing of information at the level of individual electrons. Further improvement in terms of scalability can be achieved using 1-D arrays of nanoscale QDs [4]. Such an arrangement inherently possesses multiple stable (memory) states within the device, as the quantized charge-transfer onto each conducting island (separated by tunnel barriers) is voltage dependent, and follows the Coulomb staircase behavior [5-10] for single electron devices. This allows precise control of a small number of electrons in the conducting islands, inducing periodic oscillations of the current as a function of the voltage. Thus single electron memory structures, if successfully developed at the device level, can be used to create next generation memories. In addition, a number of novel applications can be conceived using single electron tunneling devices, including displacement sensors [11], superconducting devices with a quantum cooling effect [12], and water pumps using the drag of single electrons without tunneling barriers [13] in addition to their typical applications such as highly sensitive electrometers [14,15].

The first experimental implementation of the single electron tunneling structures was carried out using two layers of aluminum, which were evaporated in situ from two angles through the same suspended mask formed by direct e-beam writing [16]. Since then, several techniques for fabricating single electron memory structures have been reported using a wide variety of device geometries and materials [17-49]. For example, Si powder-based structures were fabricated by embedding several nano Si powders within a thin insulating layer of SiO2 and adding a gate electrode on top of the Si powders [19, 20]. However, a random deposition makes it difficult to precisely fabricate single electron memory structures with reproducible parameters. Single electron devices operational at room temperatures have been reported [18, 21-32], but the fabrication of arrayed structures is still extremely challenging.

While previous work on single electron memory structures using several electronic materials represents a significant first step in the area, CNTs have become attractive candidates for single electron memory applications because of their superior electron transport properties in comparison to Si-based nanostructures [50-57]. It is expected that CNT segments can provide larger electron charging energies EC necessary for potential room temperature applications. For instance, a 30 nm-long SWCNT will possess EC up to 20 times larger than the thermal energy kT at room temperature. In contrast, to achieve a similar EC for silicon one must confine islands down to approximately 1 nm diameter [24], which is extremely difficult to reproduce in a controlled way. Larger islands necessarily limit device operation to low temperatures [33-49].

In our pursuit of CNT-QD-based devices, CNTs are grown via chemical vapor deposition between catalyst patterns and subsequently segmented using a voltage-applied AFM process as highlighted in Figure 1. The “top-level” fabrication process to create in-plane CNT-QDs is shown in Figure 1. First, a V-grooved nano-trench spanning the catalyst tips is generated by e-beam lithography and subsequent shallow reactive ion etching (RIE) or by focused ion beam (FIB) milling. Such a V-grooved nano-trench has been shown in the literature to enhance an aligned growth of CNT due to increased Van der Waals forces along the trench edges [58, 59]. The substrate is subsequently oxidized with a 10 nm thick oxide layer. Next, a 30 nm thick Mo film is deposited and patterned for circuits on the SiO2/Si substrate. The substrate is coated with poly(methylmethacrylate) (PMMA), then patterned by e-beam lithography. An alumina-supported iron catalyst (or Ni, Co, etc.) suspended in methanol is spun onto the substrate followed by a lift off process to


create catalyst islands. Then, a CNT is grown along the catalyst tips using a CVD process. In parallel, we are also investigating alternative post-assembly approaches such as dielectrophoresis (DEP) to position arrays of individual carbon nanotubes between two electrodes. Once located, the CNT is precisely cut by a nanosegmentation process in order to generate the 1-D array of CNT-QDs. During the segmentation process an AFM tip is used to apply a negative voltage of about 5 volts to create gaps at specified locations along the CNT, such that a tunnel barrier for electron transport is formed.

The quantized electronic energy levels of CNT-QDs depend strongly on the dimensions, chirality, and the electron charging energy Ec of the QD (i.e. single electron confinement). A detailed knowledge of these parameters is necessary to understand the single electron transport and storage properties of CNT-QDs, in particularly as a function of the CNT segment length. Several techniques can be combined to determine these properties. The level spacing and charging energies can be determined from the peak spacing of low-temperature differential conductance measurements as a function of gate voltage [8, 50]. Another technique is based on probing for the E11 and E22 energy states of the exciton transitions inside the CNT. This can be either achieved indirectly by photocurrent measurements as a function of the excitation wavelength or directly using optical emission/excitation spectroscopy. Those data can be directly correlated to CNT diameter and chirality (n,m-number) as documented widely in literature [60]. New energy states created when cutting CNT segments and forming quantum dots are expected to appear in the spectra and can be studied as a function of segment length, (n,m)-number, and barrier width/material.

SiO2/Si (a)

CNT

V-grooved trench

Controlled, In-situ nanosegmentation

In-plane, tip-enhanced growth of CNT

Segmented CNT (CNT-QDs)

Oxide

(b)

(c) (d)

Catalyst tip

Figure 1: Schematic diagram of the sequence for nanofabricating the CNT islands: (a) The V-grooved nano-trench is generated. After oxidation, Mo patterns for catalyst patterns are defined in order to grow an individual aligned CNT parallel to the substrate surface. (b) CNT is grown from the catalyst tip along the trench. (c) CNT is segmented by the in-situ nanosegmentation technique. (d) An oxide layer is deposited.


To this end we have carried out pre-characterization of DEP assembled and in-plane grown CNT arrays. DEP fabricated samples using 140 nm diameter MWCNTs have typically 1-3 tubes aligned between two Au contacts. The source-drain current ISD behaves linearly below about 300 mV with a typical resistance of 30-400 kΩ, and nonlinearly above this value until the device breaks irreversibly at about 5V. Photo-induced conductivity changes have been measured under spectrally filtered CW illumination in the range from 400-800 nm. A pronounced photocurrent of 60 μA is measured at ISD ±200 mV showing a slight wavelength dependence peaking at 700 nm which might be related to resonant absorption in the MWCNTs. In the low bias voltage region we observe distinct steps in the source-drain channel conductance recorded at 80K by applying a voltage Vg to the back gate. This corresponds to a field-effect transistor (FET) behavior. However, the on/off ratio of the FET effect is limited to values of about 2 due to the interplay of several metallic and semiconducting tubes as was found earlier for large MWCNTs [61].

In contrast, the in–plane grown CNTs are typically much smaller reaching into the single-wall regime. We have carried out a detailed study of the FET behavior as a function of the number of CNTs across 2 micron spaced electrodes. At a fixed CNT density, which can be controlled by the CVD growth parameters, we have access to the number of CNTs simply by varying the length of the contact stripes. The combined resistance of the CNT and the contacts increase from 60kΩ for about 100 tubes up to 3.6 MΩ if only 1-2 tubes are bridged. Devices with 12 CNTs show FET on/off ratios of about 2 and a pronounced ambipolar FET behavior. Reducing to 6 bridged CNTs increases the FET on/off ratio to values of about 4. Best results have been achieved with devices where only 1-3 tubes bridging the gap. Here we find either no dependence as a function of gate voltage indicating metallic character of all tubes, or we find a very pronounced on/off ratio up to 370 clearly demonstrating semiconducting behavior.

The demonstrated access to individual CNTs with pronounced semiconducting behavior opens now the possibility to form individual CNT-QDs by creating short segments along the nanowire. As a next step we will characterize those CNT-QDs and their single electron charging properties by low-temperature transport and photoconductance measurements.

FIELD EMISSION FROM GRAPHENE LAYERS

In other work, we are investigating the field emission properties of graphene nanostructures for vacuum electronics applications. Field emission is a quantum mechanical tunneling phenomenon in which electrons escape from a solid surface into vacuum as explained theoretically by R. H. Fowler and L. Nordheim in 1928. Field emission is widely used in many kinds of vacuum electronic applications such as flat panel displays, microwave power tubes, electron sources, and electron-beam lithography. Over the past decade, many research groups throughout the world have shown that CNTs are excellent candidates for electron emission. CNTs have high aspect ratios, small radius of curvature at their tips, high chemical stability, and high mechanical strength. Furthermore, carbon nanotube emitters stably operate at moderate vacuum conditions. However, issues related to the placement and throughput of CNT arrays have hampered the development of such arrays for commercial applications. Here, we use graphene for field emission. Graphene is a two-dimensional honeycomb-structured single crystal showing ballistic transport, zero band gap and electric spin


AccV Spot Magn Dot WD Exp -10-0kv 3-0 7291x SE 17-6 0

transport characteristics. A graphene triode structure can be used as a fundamental unit for vacuum nanoelectronics. This triode has a graphene emission tip and three electrodes as source, drain, and gate on the substrate. Depending on the gate voltage applied, electrons are emitted from the graphene tip creating an electron current which can be modulated on and off. Graphene is expected to show high electron emission efficiency due to its single atomic layer structure.

To measure field emission from graphene, graphene sheets were prepared by mechanical exfoliation and placed on an insulation layer, with the resulting field emission behavior investigated using a Zyvex Nanomanipulator operating inside a scanning electron microscope (SEM) (Figure 2). In the SEM vacuum chamber, two tungsten tips driven by the nanomanipulator were located on the graphene sample. The tips were connected to a Keithley semiconductor measurement system through feed-throughs in the vacuum chamber to apply and sense the electric signal for field emission. The graphene started to emit current at around 20V, which increased exponentially up to 170 nA following the behavior of the Fowler-Nordheim relationship shown below.

VVVI 1))(ln( 2 ∝

The estimated turn on voltages of graphene was 13V. We are further investigating the field emission properties as a function of the number of graphene layers and the directions of the atomic crystal. A triode with a gate electrode will be further studied.

Figure 2. Image of graphene layers being mechanically probed by Zyvex Nanomanipulator system operating within a scanning electron microscope. The tungsten nanomanipulator probes are connected to a Keithley 4200 semiconductor characterization system (SCS) to enable high resolution electrical characterization.

This field emitting nanodevice based on the planar form of graphene potentially allows for top-down CMOS compatible process flows, an advantage for potential industrial fabrication of electronic devices. For applications where high field emission currents or low turn-on voltages are required, nanodevices based on


graphene would inherently provide the necessary alignment based on its crystallographic nature, while CNTs oriented perpendicular to the surface or substrate is challenging. Further, the field emission characteristics from graphene may prove to be more uniform and controllable than field emission from CNTs, which can vary significantly due to geometry variations of the CNTs within a CNT array. Graphene-based electron emission can be used as an electron source for vacuum transistors and field emission displays.

CARBON NANOTUBE-BASED NANOACTUATOR

A nanoscale actuator or an array of such actuators can be used for many potential applications; for example, to investigate how external forces applied to a cell membrane affect mechanisms such as inter-cell signaling, cell growth, and cell adhesion. For such studies it is important to be able to produce a large number of such actuators with repeatable and controllable nanoactuator properties and performance. In the initial stages of this work, we have recently fabricated thermal bimorph nanoactuators based on MWNTs coated with a thin metal film on one side using pulsed laser deposition (PLD). One benefit of such an approach is that a CNT bimorph can act as a very sturdy nanolayer under repeated bending, as MWNTs in particular are well known for mechanical resilience under extreme bending [62]. In addition, MWNTs can be easily synthesized to be microns in length, which would potentially allow tip deflections in the range of hundreds of nanometers. Lastly, at smaller length scales thermal stresses can be a viable means to generate appreciable and controllable forces, and in particular can be advantageous in applications where the generation of relatively large forces is desired. To characterize the CNT bimorph nanoactuators fabricated in this work, Transmission Electron Microscope (TEM) was used to assess the metal film quality, and a thermal stage was designed and operated within a SEM chamber in order to test the thermal actuation characteristics of the fabricated nanoactuators. The force generated from the nanoactuator was measured using a lateral atomic force microscopy (LFM) by applying an external lateral counteracting load with an atomic force microscope (AFM) tip to the middle of the bimorph nanoactuator.

To fabricate the nanoactuators, Chemical Vapor Deposition (CVD)-grown MWNTs (purchased from MER Corp.) were suspended by sodium dodecyl sulphate (SDS) in distilled water [63]. A droplet of the suspension containing the MWNTs was dispensed on a silicon substrate. After drying, the substrate was broken into smaller pieces to find cantilevered MWNTs at the substrate edges. Our first unsuccessful approach to create a bimorph nanostructure utilized thermal evaporation of Al on a cantilevered MWNT at room temperature. However, we found that the metal atoms encapsulated the whole circumference of a MWNT due to the high kinetic energy of metal atoms. In an attempt to eliminate this encapsulation, the sample stage was cooled down to 150 K using liquid nitrogen. However, at such low temperatures metal grains were formed causing a marginal Al film uniformity which hampered consistent actuation performance. In contrast to thermal evaporation, we ultimately found that the PLD process allows deposition of Al on only one side of the MWNT with a precisely controlled thickness and uniformity [24] due to the low kinetic energy of ejected atoms from the target. In this approach, a Nd:YAG (Quanta Ray, DCR2-10) laser was used to deposit Al, with a deposition rate of 0.6 Å per 1 min at 70 mJ/10 ns pulse. Figure 3(a) shows TEM images of a nanoactuator fabricated via the PLD deposition [64].


Given a bimorph structure as shown in Figure 3, a temperature variation ΔT causes an end deflection of the form

1222

464)()(3

−

⎥⎥⎦

⎤

⎢⎢⎣

⎡+⎟⎟

⎠

⎞⎜⎜⎝

⎛+++⎟⎟

⎠

⎞⎜⎜⎝

⎛−Δ−=Δ

Al

MWNT

Al

MWNT

Al

MWNT

MWNT

Al

MWNT

Al

MWNT

Al

MWNTAl

MWNTAlMWNTAl

dd

YY

dd

dd

YY

dd

ddddTL αα

(1)

where d is the layer thickness, Y is the modified Young's modulus Y = E (1−ν) , E is Young’s modulus, ν

is Poisson ratio, and α is the coefficient of thermal expansion (CTE), with subscripts referring to the Al or MWNT layer, respectively [28]. (Note that the analysis assumes a rectangular cross section for each layer.) The thickness of each layer and the device length were measured using SEM and TEM. For the analysis we used the reported CTE and Young’s modulus values of 3×10-6 /K at 1 TPa for MWNT [65], and 23×10-6 /K at 70 GPa for Al bulk values, respectively. The temperature of the sample substrate was measured using a thermocouple at the thermal stage inside the SEM. The bimorph tip generates a bending force against an external load at the tip. The amount of external load required to recover the bimorph to its room temperature geometry can be calculated as

MWNTMWNTAlAl

MWNTAlMWNTAlMWNTAlMWNTAl

YdYdddddYY

LTwF

++Δ−

=)()( αα

(2)

Figure 3: Bimorph nanoactuators consisting of a MWNT covered on one side with a uniform PLD-based Al film [64]. (a) TEM image of MWNT-Al bimorph nanoactuators at a side view angle. (b) SEM image of a nanoactuator from the same PLD batch. A white line indicates the entire length of the bimorph CNT. The image was taken at 690 K in a thermal stage used to control the substrate temperature inside the SEM. Al was deposited from left to right in the image. (c) SEM image taken at 290 K. (d) For comparison, the image (b) is superposed on the image (c).


where w is width (diameter) of the MWNT.

The lateral force microscopy (LFM) technique was used to measure the actuation force generated from the nanoactuator. The force from the nanoactuator was measured by sweeping an AFM tip laterally at the middle of a bimorph. The thermally generated force twisted the AFM cantilever further, with the resulting force increasing as the temperature was elevated by a thermal stage under the AFM. The total force (reaction with

thermal response) can be calculated using the relationship RLLtwist IckF −= , where ktwist is the torsional

spring constant of the AFM cantilever, cL is the ratio relating the detected voltage as a function of the AFM tip lateral swing (units of nm/mV), and IL-R is the measured voltage in mV. The torsional spring constant ktwist

was calculated using the relationship 23 )1(6 LhwEt ν+ , where E, L, t, w, and h are Young’s modulus,

length, thickness, width of the AFM cantilever, and height of the AFM tip. For the AFM cantilever used in these experiments the torsional spring constant ktwist was found to be 105 nN/nm. The value of cL was calibrated by measuring the voltages generated at the quad-photodiode in the AFM when the tip touched a step edge (0.038 ± 0.002 nm/mV). The measured IL-R was used to calculate the amount of force applied at the AFM tip. The generated force from the nanoactuator was calculated by subtracting IL-R at the low temperature from the IL-R at the high temperature. A saw-tooth feature in the IL-R response (not shown) was indicative of stick-slip behavior as the AFM tip slides along the bimorph before release. Similar behavior was also observed in a bare MWNT cantilever. The LFM measurement was repeated at ΔT = 0 K (298 K), 50 K, 100 K, 130 K, and at 0 K again. For a sample with a measured MWNT diameter of 100± 20 nm, an Al layer thickness of 60± 10 nm, and bimorph length of 5.2± 0.5 μm, a temperature change from 290 K to 690 K caused a deflection which was measured experimentally to 550 ± 200 nm, which compares favorably with the calculated deflection of 430 nm found using equation (1). As shown in Figure 4, the measured forces agree well with the predictions obtained using equation (2) for two different Aluminum layer thicknesses [64].

CONCLUSIONS

We are pursuing the fabrication, assembly and manipulation of carbon nanotube and graphene nanostructures for various nanosensor/actuator and nanoelectronics device applications. Overcoming the technical challenges of scaling up such results, including reliability and repeatability of the assembled structures, will enable one to leverage the outstanding electrical properties of these carbon-based nanomaterials in the development of next-generation devices with unrivaled functionality. Such capabilities show potential widespread application in areas such as sensors, detectors, system-on-a-chip, system-in-a-package, programmable logic controls, energy storage systems and future electronic systems.

ACKNOWLEDGEMENT

This work has been partially supported by Air Force Office for Scientific Research (Award No. FA9550-08-1-0134) and National Science Foundation (Major Research Instrumentation Program, Award No. DMI-0619762).


ci)U

0

1600-

- 1200

0U

U

Al 60 nm

A Al 20 nfl,

1

0300 350 400

Temperature (K)

450

Figure 4. Actuation force versus temperature for two different Al layer thicknesses [64]. The lines represent the prediction from equation (2) based on the measured bimorph geometries. Al thickness was 60 ± 10 nm (red) and 20 ± 5 nm (purple), MWNT diameters were 200 ± 20 nm, and length of the bimorphs were 2.2 ± 0.2 μm. The room temperature measurement for the 60 nm Al layer thickness was done after cooling, with the results indicating residual film stress. The error bars for the measured forces are either the standard deviation of multiple measurements or drift of IL−R, where the larger value was chosen. All measurements were repeated three times at each temperature.

REFERENCES

[1] S. J. Tans, A. R. M. Verschueren and C. Dekker, “Room-temperature transistor based on a single carbon CNT,” Nature, vol. 393, pp. 49-52, May 1998.

[2] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang,Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov “Electric field effect in atomically thin carbon films,” Science, vol. 306, pp. 666-669, 2004.

[3] D. Averin and K. Likharev, “Single electronics: a correlated transfer of single electrons and Copper pairs in systems of small tunnel junctions,” in Mesoscopic Phenomena in Solids, B. L. Altshuler, P. A. Lee, and R. A. Webb Ed., Amsterdam: Elsevier, pp. 173-271, 1991.

[4] S. Mahapatra and A. M. Ionescu, Hyrid CMOS Single-Electron-Transistor Device and Circuit Design, Artech House, Chapter 6, ISBN 1-59693-069-1, 2006.

[5] U. Meirav and E. B. Foxman, “Single-electron phenomena in semiconductors,” Semicond. Sci. Technol., vol. 11, no. 3, pp. 255–284, 1996.

[6] K. K. Likharev, N. S. Bakhvalov, G. S. Kazacha, and S. I. Serdyukova, “Single-electron tunnel junction array: an electrostatic analog of the Josephson transmission line,” IEEE Trans. Magnetics, vol. 25, no. 2, pp. 1436-1439, 1989.

[7] L. R. Fonseca, A. N. Korotkov, and K. K. Likharev, “A numerical study of the accuracy of single-electron current standards,” J. Appl. Phys., vol. 79, no. 12, pp. 9155-9165, 1996.

Proc. of SPIE Vol. 7318 731813-10

[8] M. Bockrath, D. H. Cobden, P. L. McEuen, N. G. Chopra, A. Zettl, A. Thess, and R. E. Smalley, “Single-electron transport in ropes of carbon nanotubes,” Science, vol. 275, pp. 1922-1925, 1997.

[9] S. J. Tans, A. R. M. Verschueren and C. Dekker, “Room-temperature transistor based on a single carbon nanotube,” Nature, vol. 393, pp. 49-52, May 1998.

[10] S. Berber, Y. K. Kwon and D. Tománek, “Unusually high thermal conductivity of carbon nanotubes,” Phys. Rev. Lett., vol. 84, no. 20, pp. 4613-4616, May 2000.

[11] R. G. Knobel and A. N. Cleland, “Nanometre-scale displacement sensing using a single electron transistor,” Nature, vol. 424, pp. 291-293, 2003.

[12] A. Naik, O. Buu, M. D. LaHaye, A. D. Armour, A. A. Clerk, M. P. Blencowe and K. C. Schwab, “Cooling a nanomechanical resonator with quantum back-action,” Nature, vol. 443, pp. 193-196, 2006.

[13] K. Likharev, “Dragging single electrons,” Nature, vol. 410, pp. 531-533, 2001. [14] E. G. Emiroglu, Z. A. K. Durrani, D. G. Hasko and D. A. Williams, “Silicon single-electron parametron

cell for solid-state quantum information processing,” Microelectronic Engineering, vol. 67-68, pp. 755-762, June 2003.

[15] K. Matsumoto, Y. Gotoh, T. Maeda, J. A. Dagata and J. S. Harris “Room-temperature single-electron memory made by pulse-mode atomic force microscopy nano oxidation process on atomically flat -alumina substrate,” Appl. Phys. Lett., vol. 6, pp. 239-241, 2000.

[16] T. A. Fulton and G. J. Dolan, “Observation of single-electron charging effects in small tunnel junctions,” Phys. Rev. Lett., vol. 59, no.1, pp. 109-112, 1987.

[17] C. Hines, S. A. McCarthy, J. B. Wang, and P. C. Abbott, “Electronic Structure of Quantum Dots,” Intern. Conf. on Computational Nanoscience and Nanotechnology, pp. 201-204, 2002.

[18] Y. Gotoh, K. Matsumoto, V. Bubanja, F. Vazquez, T. Maeda, and J. S. Harris, “Experimental and simulated results of room temperature single electron transistor formed by atomic force microscopy nano-oxidation process,” Jpn. J. Appl. Phys., vol. 39, pp. 2334-2337, 2000.

[19] A. Dutta, S. P. Lee, Y. Hayafune, S. Hatatani, and S. Oda, “Single-electron tunneling devices based on silicon quantum dots fabricated by plasma process,” Jpn. J. Appl. Phys. vol. 39, pp. 264-267, 2000.

[20] D. L. Klein, P. L. McEuen, J. E. Bowen Katari, R. Roth, and A. P. Alivisatos, “An approach to electrical studies of single nanocrystals,” Appl. Phys. Lett., v68, pp. 2574-2576, 1996.

[21] K. Matsumoto, M. Ishii, K. Segawa, Y. Oka, B. Vartanian, and J. Harris, “Room temperature operation of a single electron transistor made by the scanning tunneling microscope nanooxidation process for the TiOx/Ti system,” Appl. Phys. Lett., vol. 68, pp. 34-36, 1996.

[22] Y. Takahashi, H. Namatsu, K. Kurihara, K. Iwdate, M. Nagase, and K. Murase, “Size dependence of the characteristics of Si silicon-electron transistors on SIMOX substrates,” IEEE Trans. Electron Devices, vol. 43, pp. 1213-1217, 1996.

[23] J. Shirakashi, K. Matsumoto, N. Miura, and M. Konagai, “Single-electron charging effects in Nb/Nb oxide-based single electron transistors at room temperature,” Appl. Phys. Lett., vol. 72, pp. 1893-1895, 1998.

[24] J. U. Kim, and L. B. Kish, “Can single electron logic microprocessors work at room temperature?,” Phys. Lett. A, vol. 323, pp. 16-21, 2004.

[25] Y. M. Wan, K. D. Huang, S. F. Hu, C. L. Sung, and Y. C. Chou, “Coulomb blockade oscillations in ultrathin gate oxide silicon single-electron transistors,” J. Appl. Phys., vol. 97, pp. 116106, 2005.

Proc. of SPIE Vol. 7318 731813-11

[26] P. W. Li, W. M. Liao, David M. T. Kuo, S. W. Lin, P. S. Chen, S. C. Lu, and M. –J. Tsai, “Fabrication of a germanium quantum-dot single-electron transistor with large Coulomb-blockade oscillations at room temperature,” Appl. Phys. Lett., vol. 85, no. 9, pp. 1532-1534, 2004.

[27] Y. T. Tan, T. Kamiya, Z. A. K. Durrani, and H. Ahmed, “Room temperature nanocrystalline silicon single-electron transistors,” J. Appl. Phys., vol. 94, no. 1, pp. 633-637, 2003.

[28] Y. Yang, and M. Nogami, “Room temperature single electron transistor with two-dimensional array of Au-SiO2 core-shell nanoparticles,” Science and Technology of Advanced Materials, vol. 6, pp. 71-75, 2005.

[29] M. Saitoh, H. Harata, and T. Hiramoto, “Room-temperature demonstration of low-voltage and tunable static memory based on negative differential conductance in silicon single-electron transistors,” Appl. Phys. Lett., vol. 85, no. 25, pp. 6233-6235, 2004.

[30] T. Kitade, K. Ohkura, and A. Nakajima, “Room-temperature operation of an exclusive-OR circuit using a highly doped Si single-electron transistor,” Appl. Phys. Lett., vol. 86, 123118, 2005.

[31] W. M. Liao, P. W. Li, David M. T. Kuo, and W. T. Lai, “Room-temperature transient carrier transport in germanium single-hole/electron transistors,” Appl. Phys. Lett., vol. 88, 182109, 2006.

[32] G. Pennelli, M. Piotto, and G. Barillaro, “Silicon single-electron transistor fabricated by anisotropic etch and oxidation,” Microelectronic Engineering, vol. 83, pp. 1710-1713, 2006.

[33] K. Nomoto, R. Ugajin, T. Suzuki and I. Hase, “Novel logic device using coupled quantum dots,” Electron. Lett., vol. 29, no. 15, pp. 1380-1381, Jul. 1993.

[34] S. -H. Kim, G. Markovich, S. H. Choi, K. L. Wang, and J. R. Heath, “Tunnel diodes fabricated from CdSe nanocrystal monolayers,” Appl. Phys. Lett., vol. 74, no. 2, pp. 317-319, 1999.

[35] S. H. Choi, K. L. Wang, M. S. Leung, G. W. Stupian, N. Presser, B. A. Morgan, R. E. Robertson, M. Abraham, E. E. King, M. B. Tueling, S. W. Chung, J. R. Heath, S. L. Cho, and J. B. Ketterson, “Fabrication of bismuth nanowires with a silver nanocrystal shadowmask,” J. Vac. Sci. Tech. A, vol. 18, no. 4, pp. 1326-1328, 2000.

[36] S. J. Tans, M. H. Devoret, H. Dai, A. Thess, R. E. Smalley, L. J. Geerligs, and C. Dekker, “Individual single-wall carbon nanotubes as quantum wires,” Nature, vol. 386, pp. 474-477, 1997.

[37] D. L. Klein, R. Roth, A. K. L. Lim, A. P. Alivisatos, and P. L. McEuen, “A single-electron transistor made from a cadmium selenide nanocrystal,” Nature, vol. 389, pp. 699-701, 1997.

[38] Y. Nakamura, C. D. Chen, and J, S. Tsai, “100-K operation of Al-based single-electron transistors,” Jpn. J. Appl. Phys., vol. 35, pp. L1465-1467, 1996.

[39] D. C. Ralph, C. T. Black, and M. Tinkham, “Gate-voltage studies of discrete electronic states in aluminum nanoparticles,” Phys. Rev. Lett., vol. 78, pp. 4087-4090, 1997.

[40] S. Altmeyer, A. Hamidi, B. Spangenberg, and H. Kurz, “77 K single electron transistors fabricated with 0.1μm technology,” J. Appl. Phys., vol. 81, pp. 8118-8120, 1997.

[41] F. Nakajima, Y. Ogasawara, J. Motohisa, and T. Fukui, “GaAs dot-wire coupled structures grown by selective area metalorganic vapor phase epitaxy and their application to single electron devices,” J. Appl. Phys., vol. 90, pp. 2606-2011, 2001.

[42] G. Johansson, A. Kack and G. Wendin, “Single-shot charge qubit read-out using a single electron transistor: back-action and fidelity,” Physica C, vol. 368, pp. 289-293, 2002.

Proc. of SPIE Vol. 7318 731813-12

[43] S. Kubatkin, A. Danilov, M. Hjort, J. Cornil, J. Bredas, N. Stuhr-Hansen, P. Hedegard, and T. Bjornholm, “Single-electron transistor of a single organic molecule with access to several redox states,” Nature, vol. 425, pp. 698-701, 2003.

[44] R. S. Liu, H. Pettersson, L. Michalak, C. M. Canali, and L. Samuelson “Probing spin accumulation in Ni/Au/Ni single-electron transistors with efficient spin injection and detection electrodes,” Nano Lett., vol. 7, no. 1, pp. 81-85, 2007.

[45] H. T. A. Brenning, S. E. Kubatkin, D. Erts, S. G. Kafanov, T. Bauch, and P. Delsing, “A single electron transistor on an atomic force microscope probe,” Nano Lett., vol. 6, no. 5, pp. 937-941, 2006.

[46] A. Vijayaraghavan, K. Kanzaki, S. Suzuki, Y. Kobayashi, H. Inokawa, Y. Ono, S. Kar, and P. M Ajayan “Metal-semiconductor transition in single-walled carbon nanotubes Induced by low-energy electron irradiation,” Nano Lett., vol. 5, no. 8, pp. 1575-1579, 2005.

[47] Y. Cui, U. Banin, M. T. Björk, and A. P. Alivisatos, “Electrical transport through a single nanoscale semiconductor branch point,” Nano Lett., vol. 5, no. 7, pp. 1519-1523, 2005.

[48] M. T. Björk, C. Thelander, A. E. Hansen, L. E. Jensen, M. W. Larsson, L. R. Wallenberg, and L. Samuelson, “Few-electron quantum dots in nanowires,” Nano Lett., vol. 4, no. 9, pp. 1621-1625, 2004.

[49] D. Hu. Chae, J. F. Berry, S. Jung, F. A. Cotton, C. A. Murillo, and Z. Yao, “Vibrational excitations in single trimetal-molecule transistors,” Nano Lett., vol. 6, no. 2, pp. 165-168, 2006.

[50] H. W. C. Postma, T. Teepen, Z. Yao, M. Grifoni, and G. Dekker, “Carbon nanotube single-electron transistors at room temperature,” Science, vol. 293, pp. 76-79, 2001.

[51] L. Guo, E. Leobandung, S. Y. Chou, “A silicon single-electron transistor memory operating at room Temperature,” Science, vol. 275, pp. 649-651, 1997.

[52] M. A. Kastner, “The single electron transistor and artificial atoms,” Annals of Physics, vol. 9, no. 11-12, pp. 885–894, 2000.

[53] K. Matsuoka, H. Kataura, and M. Shiraishi, “Ambipolar single electron transistors using side-contacted single-walled carbon nanotubes,” Chemical Physics Letters, vol. 417, pp. 540-544, 2006.

[54] D. Tsuya, M. Suzuki, Y. Aoyagi, and K. Ishibashi, “Exclusive-OR gate using a two-input single-electron transistor in single-wall carbon nanotubes,” Appl. Phys. Lett., vol 87, pp.153101, 2005.

[55] D. Tsuya, K. Ishibashi, M. Suzuki, and Y. Aoyagi, “Local Ar beam irradiation for making tunneling barriers and its application to single electron inverter in multi-wall carbon nanotubes,” Physica E, vol. 19, pp. 157-160, 2003.

[56] Aravind Vijayaraghavan, Kenichi Kanzaki, Saturo Suzuki, Yoshihiro Kobayashi, Hiroshi Inokawa, Yukinori Ono, Swastik Kar, and Pulickel M Ajayan, “Metal-Semiconductor Transition in Single-Walled Carbon Nanotubes Induced by Low-Energy Electron Irradiation,” Nano Letters, vol. 5, no. 8, pp. 1575-1579, 2005.

[57] L. Roschier, J. Penttila, M. Martin, P. Hakonen, M. Paalanen, U. Tapper, E. I. Kauppinen, C. Journet, and P. Bernier, “Single-electron transistor made of multiwalled carbon nanotube using scanning probe manipulation,” Appl. Phys. Lett., vol. 75, no. 5, pp. 728-730, 1999.

[58] A. Nojeh, A. Ural, R. F. Pease, and H. Dai,“Electric-field-directed growth of carbon nanotubes in two dimensions,” J. Vac. Sci. Technol. vol. B 22, pp. 3421-3425, 2004.

Proc. of SPIE Vol. 7318 731813-13

[59] Y. Zhang, A. Chang, J. Cao, Q. Wang, W. Kim, Y. Li, N. Morris, J. Kong, and H. Dai, “Electric-field-directed growth of aligned single-walled carbon nanotubes,” Appl. Phys. Lett., vol. 79, no. 19, pp. 3155-3157, 2001.

[60] S. M. Bachilo et al., Science 298, 2361 (2002) and E.H. Haroz, et al, Phys. Rev. B, 77, 125405, 2008. [61] R. Martel, T. Schmidt, H.R. Shea, T. Hertel, and Ph. Avouris, “Single- and multi-wall carbon nanotube

field-effect transistors” Appl. Phys. Lett. vol 73, pp. 2447-2449, 1998. [62] Falvo M and Superfine R 2000 J. of Nanoparticle Research 2 237-248 [63] Lewenstein J C, Burgin T P, Ribayrol T P, Nagahara L A and Tsui R K 2002 Nano Lett. 2 443-446 [64] O. Sul and E. H. Yang, “Multi-Walled Carbon Nanotube-Aluminum Bimorph Nanoactuator,” IOP

Nanotechnology, vol. 20, 095502, 2009. [65] Treacy M M J, Ebbesen T W, and Gibson J M 1996 Nature 381 678-680

Proc. of SPIE Vol. 7318 731813-14

Documents

Carbon-based nanodevices for sensors, actuators and electronics