Physical Principles of Nanoelectromechanical Devices

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Physical Principles of Nanoelectromechanical
Devices
Robert Shekhter
University of Gothenburg, Sweden
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Lecture 1 Introduction to nanoelectromechanical
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Electromechanics and Charge Metrology
The electroscope was an early scientific
instrument used to detect the presence and
magnitude of electric charge on a body.
William Gilbert Born on May 24, 1544, in
Colchester, England Died on Dec. 10, 1603, in
London
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Lecture 1 Introduction to nanoelectromechanical
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Downsizing of Electro-Mechanical Devices
Macroscopic Electromechanical Device
Micro-Electromechanical Accelerometer (Airbag
Sensor) A small integrated circuit with
integrated micro mechanical elements, which move
in response to rapid deceleration. This motion
causes a change in capacitance, which is detected
by the electronics on the chip that then sends a
signal to fire the airbag.
Nano-Electromechanical Machinery in the Living
Cell Ion channels make it possible for cells to
generate and transmit electrical signals, and are
the basic molecular building blocks in the
nervous system. Rapid transport, ion selectivity,
and electrically controlled channel gating are
central to their functionality.
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Five-Lecture Course on the Basic Physics of
Nanoelectromechanical Devices

• Lecture 1 Introduction to nanoelectromechanical
  systems (NEMS)
• Lecture 2 Electronics and mechanics on the
• nanometer scale
• Lecture 3 Mechanically assisted
  single-electronics
• Lecture 4 Quantum nano-electro-mechanics
• Lecture 5 Superconducting NEM devices

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References

•  Book Andrew N. Cleland, Foundation of
  Nanomechanics
• Springer,2003 (Chapter7,esp.7.1.4, Chapter 8,9)
• Reviews R.Shekhter et al. Low.Tepmp.Phys. 35,
  662 (2009)
• 
  J.Phys. Cond.Mat. 15, R 441 (2003)
• J.
  Comp.Theor.Nanosc., 4, 860 (2007)
•  

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Lecture 1 Introduction to nanoelectromechanical
systems (NEMS)
Outline

• Why NEMS?
• Fabrication methods
• Actuation and detection methods

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Part 1Why NEMS?
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MEMS already a mature technology
MEMS applications can be found in the information
technology, transport industry, medicine and many
other fields totalling more than1000 million
dollars of revenues per year.
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Device applications

• Smaller, cheaper, faster, lower power
• consumption
• Phones of the future. NEM-devices are
• in the right frequency range (1-5 GHz) to
• replace elements in cell phones
• Better frequency selectivity (higher Q),
• lower power consumption
• New sensor applications
• Needed High Q, high frequency

and interesting cutting edge physics.
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New Functionality and Possible Applications of
Nanoscale Electromechanics

• NEM sensing (sensing of mass, displacements and
  forces on an atomic scale)
• Mechanical control and mechanically assisted
  transportation of single electrons
• Mechanically controllable quantum point contacts

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Resonant Mass Sensors (mass sensing on the level
of single molecules)
dMmin M/Q
low M , high w0 , high Q
See review in Nature Nanotech. 4, 445
(2009) Roukes group (Caltech) Sensitivity
200 Da Nature Nanotech. 3, 533 (2008) Nano
Lett. 8, 4342 (2008)
Roukes group (Caltech) Nature Nanotechn 4,
445 2009 (Roukes) Sensitivity 100
zepto-grams K.L.Ekinci et al. APL 64, 4469 (2004)
200 Dalton3.6 10-22 g
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Biomolecular Recognition
Surface stress changes the nanomechanical
response of cantilevers. Bending of cantilevers
detected by an optical deflection technique.
J. Fritz et al., Science 288, 316 (2000)
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MEMS/NEMS Devices as Electrometers
NEMS analogue of Coulombs torsional
electrometer from 1784. A charge on the gate
affects the resonance frequency.

• measured sensitivity (300 K) 0.1eHz-1/2
• ultimate sens. (300 K) 2 10-5 eHz-1/2

A.N. Cleland and M.L. Roukes, Nature 392, 160
(1998)
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Detection of Nanomechanical Displacements
Blurring in STM from thermal vibrations, Nano
Lett. 3, 1577 (2003) (Schönenberger, Basel)
Tuning band gap with strain PRL 90, 156401
(McEuen)
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Nanomechanical Manipulation (Nanotweezer)
Left A nanotweezer made of two isolated CNTs is
opened and closed by applying a bias voltage.
Top Optical micrographs showing the sequential
process of nano-tweezer manipulation of
polystyrene nanoclusters containing fluorescent
dye molecules. P. Kim and C.M. Lieber, Science
286, 2148 (1999)
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Nanomechanical Single-Electron Transistor
bias volatge
gate voltage
Nature 407, 57 (2000) (P.L. McEuen, Cornell)
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Mechanical Sharpening of Quantum Point Contact
Top left Top and side view of a mechanically
controlled break junction, with notched wire (1),
two fixed counter supports (2), bending beam (3),
drops of epoxy adhesive (4) and stacked piezo
element (5). Top right Electron microscopy
image of a gold break junction on SiO2
cantilvers Right Sharpening of the contact by
mechanical elongation N. Agrait et al., Phys.
Rep. 377, 81 (2003)
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Nanoelectromechanics of the Breaking of an
Atomic Gold Wire
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Part 2Fabrication methods
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Top-Down Semiconducting Suspended Nanowires
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Bottom-Up Self-Assembled Metal-Organic
Composites
Molecular manufacturing a way to design
materials on the nanometer scale.
Encapsulated 4 nm Au particles self-assembled
into a 2D array supported by a thin film, Anders
et al., 1995
Scheme for molecular manufacturing
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Molecular Junctions
Methods to fabricate molecular junctions
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Materials properties
Electronic properties
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Suspended CNTs
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Suspended CNTs
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Part 3Actuation and detection methods
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Methods of Actuation and Detection
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systems (NEMS)
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• STM detection
• Capacitive actuation and detection
• Magnetomotive method
• Tunnel spectroscopy and point-contact
  spectroscopy
• of NEM vibrations
• Mechanically assisted transport of electrons

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Different Types of NEM Coupling
C(x)

• Capacitive coupling
• Tunneling coupling
• Shuttle coupling
• Inductive coupling

R(x)
C(x)
R(x)
I
Lorentz force for given I
FL
H .
Electromotive force at I 0 for given v
E
v
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Electrostatic Actuation and Detection
Au/Cr electrodes (Au/Cr) are shown in yellow, and
the silicon oxide surface in grey. The sides of
the trench, typically 1.21.5 µm wide and 500 nm
deep, are marked with dashed lines. A suspended
nanotube can be seen bridging the trench.
300 nm
Non-zero only if beam moves
V. Sazonova et al., Nature 431, 284 (2004)
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Intrinsic Thermal Vibrations of Single-Wall
Carbon Nanotubes Imaged by a Scanning Electron
Microscope (SEM)
Babic et al., Nano Letters 3, 1577 (2003)
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Magnetomotive Actuation and Detection
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Magnetomotive Method Pt Nanowire
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Magnetomotive Method Breaking the GHz Barrier
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Measuring Eigenfrequencies Phonon Assisted
Tunneling
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Point Contact Spectroscopy in a H2 Molecule
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Vibration Modes for Deuterium, Pt-D2-Pt