physical principles of nanoelectromechanical devices robert shekhter university of gothenburg,...
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Physical Principles of Nanoelectromechanical Devices
Robert Shekhter
University of Gothenburg, Sweden
William Gilbert Born on May 24, 1544, in
Colchester, England Died on Dec. 10, 1603, in London
The electroscope was an early scientific instrument used to detect the presence and magnitude of electric charge on a body.
Electromechanics and Charge Metrology
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 2/35
Downsizing of Electro-Mechanical DevicesMacroscopic 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.
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 3/35
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
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)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS)
Why NEMS? Fabrication methods Actuation and detection methods
Outline
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 7/35
Part 1Why NEMS?
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.
MEMS – already a mature technology
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 8/35
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.
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 9/35
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
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 10/35
New Functionality and Possible Applications of Nanoscale
Electromechanics
Resonant Mass Sensors(mass sensing on the level of single molecules)
Roukes’ group (Caltech): Nature Nanotechn 4, 445 2009 (Roukes)Sensitivity: 100 zepto-gramsK.L.Ekinci et al. APL 64, 4469 (2004)
200 Dalton=3.6 10-22 g
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 11/35
low M , high 0 , high Q
See review in Nature Nanotech. 4, 445 (2009)[Roukes’ group (Caltech)]
Sensitivity: ~200 DaNature Nanotech. 3, 533 (2008);Nano Lett. 8, 4342 (2008)
Mmin ≈ M/Q
Biomolecular RecognitionSurface stress changes the nanomechanical response of cantilevers. Bending of cantilevers detected by an optical deflection technique.
J. Fritz et al., Science 288, 316 (2000)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 12/35
MEMS/NEMS Devices as Electrometers
NEMS analogue of Coulomb’s 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
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 13/35
A.N. Cleland and M.L. Roukes, Nature 392, 160 (1998)
Detection of Nanomechanical Displacements
Tuning band gap with strainPRL 90, 156401 (McEuen)
Blurring in STM from thermalvibrations, Nano Lett. 3, 1577(2003) (Schönenberger, Basel)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 14/35
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)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 15/35
Nature 407, 57 (2000) (P.L. McEuen, Cornell)
gate voltage
Nanomechanical Single-Electron Transistor
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 16/35
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)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 17/35
Nanoelectromechanics of the Breaking of an Atomic Gold Wire
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 18/35
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 19/35
Part 2Fabrication methods
Top-Down – Semiconducting Suspended Nanowires
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 20/35
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
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 21/35
Molecular Junctions
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 22/35
Methods to fabricate molecular junctions
Electrical – heteroconducting
Mechanical - heteroelastic
Quantum coherence
Coulomb correlations
11 12 11/ , 1, 10 10R M R MRC s
Electromechanical coupling
Basic Characteristics Self-Assembled Materials
Materials properties Electronic properties
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 23/35
Suspended CNTs
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 24/35
Suspended CNTs
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 25/35
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 26/35
Part 3Actuation and detection
methods
Methods of Actuation and Detection
a) STM detectionb) Capacitive actuation and detectionc) Magnetomotive methodd) Tunnel spectroscopy and point-contact spectroscopy of NEM vibrationsa) Mechanically assisted transport of electrons
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 27/35
• Capacitive coupling
• Tunneling coupling
• Shuttle coupling
• Inductive coupling
C(x)
R(x)
C(x) R(x)
Lorentz forcefor given I
Electromotive force at I = 0for given v
I
FL
E
v
H .
Different Types of NEM CouplingLecture 1: Introduction to nanoelectromechanical systems (NEMS) 28/35
Electrostatic Actuation and Detection
V. Sazonova et al., Nature 431, 284 (2004)
Au/Cr electrodes (Au/Cr) are shown in yellow, and the silicon oxide surface in grey. The sides of the trench, typically 1.2–1.5 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
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 29/35
( )g g g g g gq C V C V V C
Intrinsic Thermal Vibrations of Single-Wall Carbon Nanotubes Imaged by a Scanning Electron Microscope
(SEM)
Babic et al., Nano Letters 3, 1577 (2003)
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 30/35
Magnetomotive Actuation and Detection
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 31/35
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 32/35
Magnetomotive Method: Pt Nanowire
Magnetomotive Method: Breaking the GHz Barrier
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 33/35
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 34/35
Measuring Eigenfrequencies: Phonon Assisted Tunneling
Point Contact Spectroscopy in a H2 Molecule
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 35/35
Lecture 1: Introduction to nanoelectromechanical systems (NEMS) 36/35
Vibration Modes for Deuterium, Pt-D2-Pt