Microsystems Laboratory UC-Berkeley, ME Dept. 1 Liwei Lin, University of California at Berkeley Introduction to Nanotechnology and Nanoscience – Class#2 Liwei Lin Professor, Dept. of Mechanical Engineering Co-Director, Berkeley Sensor and Actuator Center The University of California, Berkeley, CA94720 e-mail: [email protected]http://www.me.berkeley.edu/~lwlin
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Introduction to Nanotechnology and Nanoscience – Class#2 · 2021. 1. 27. · Microsystems Laboratory UC-Berkeley, ME Dept. Liwei Lin, University of California at Berkeley 1 Introduction
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Microsystems LaboratoryUC-Berkeley, ME Dept.
1Liwei Lin, University of California at Berkeley
Introduction to Nanotechnology and Nanoscience – Class#2
Liwei Lin
Professor, Dept. of Mechanical Engineering Co-Director, Berkeley Sensor and Actuator CenterThe University of California, Berkeley, CA94720
& Bottom-up Processes� (some materials from Professor Lydia Sohn)
Microsystems LaboratoryUC-Berkeley, ME Dept.
4Liwei Lin, University of California at Berkeley
Microsystems LaboratoryUC-Berkeley, ME Dept.
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DNA Detection
Microsystems LaboratoryUC-Berkeley, ME Dept.
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DNA Detection
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Molecular ElectronicsThe Future?
Microsystems LaboratoryUC-Berkeley, ME Dept.
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National Nanotechnology Initiative
Even though nanoscience & nanotechnology had existed for many years, it was Present Bill Clinton in January 2000 who catapulted (for better or for worse) the field into mainstream science & engineering and society—Proposed the NNI which has now become a multibillion dollar investment in the US—see http://www.nano.gov for history and current info. on the NNI
• Estimated world-wide investment on nanotechnology and nanoscience is $8.6B in 2004
Microsystems LaboratoryUC-Berkeley, ME Dept.
9Liwei Lin, University of California at Berkeley
Nanotechnology Explosion
Microsystems LaboratoryUC-Berkeley, ME Dept.
10Liwei Lin, University of California at Berkeley
Some big numbers
Federal 2002 nanofunding $622 millionEstimated nanosales volume in 2015 $1.2 trillionStates with active nanodevelopments 24
Microsystems LaboratoryUC-Berkeley, ME Dept.
Why should I take this course?
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Microsystems LaboratoryUC-Berkeley, ME Dept.
Who is in this class (2015)?
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0 5 10 15 20 25 30
Mechanical Engineering
Materials Science
Chemical Engineering
Chemistry
Bioengineering
Engineering Physics
Chemical Biology
Molecular/Cell Biology
Civil Engineering
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Graduate
Senior
Junior
Sophomore
Who is in this class (2015)?
Microsystems LaboratoryUC-Berkeley, ME Dept.
“Nanoscience & ME”
What does a mechanical engineer do in nanoscience?
Research� Nanoscience is hot!� National labs, academia, industrial research
organizations (IBM, PARC)
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http://www.mrs.org/science-as-art/
“Nano-Explosions”Color-enhanced scanning electron micrograph of an overflowed electrodeposited magnetic nanowire array (CoFeB), where the template has been subsequently completely etched. It’s a reminder that nanoscale research can have unpredicted consequences at a high level.
- Fanny Beron, École Polytechnique de Montréal, Montréal, Canada
Scanning electron microscope image of a copper oxide cluster, 3.5 microns in diameter, prepared by evaporation and condensation over an alumina substrate. The smiley nose and eye are present in the original SEM image, which has only been color-enhanced. - Elisabetta Comini, University of Brescia, Italy
Mechanical Properties� At the nanoscale, surface and interface forces become dominant.� For example,
Adhesion forcesCapillary forcesStrain forces
Surface coatings are extremely important to prevent stickingin nanoscale electro-mechanical systems (NEMS)
Microsystems LaboratoryUC-Berkeley, ME Dept.
29Liwei Lin, University of California at Berkeley
Stiction in Micro/Nano Structures
� Strong capillary forces during the releasing process and pin down the free-standing microstructure
Anchor Micro Beam Structure
Silicon Substrate
Stiction AreaLiquid
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Microstructure Stiction Examples� Shorter beams may survive stiction problems*
*Carlos Mastrangelo, Univ. of Michigan
Mastrangelo et al., “Mechanical Stability and Adhesion of MicrostructuresUnder Capillary Forces,” IEEE/ASME J. of Microelectromechanical Systems,Vol. 2, 44-55, 1993
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Anti-Stiction Coating
� Self-assembled monolayer (SAM) coating by using OTS (octadecyltrichlorosilane) - C18H37SiCl3
hydrophilic0 - 30o
Silicon Substrate
concave
~ 114o
hydrophobicSilicon Substrate
convex
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Melting Temperature
Nanocrystal size decreases
Surface energy increases
Melting point decreases
3 nm CdSe nanocrystal melts at 700 K compared to Bulk CdSe at 1678K
Microsystems LaboratoryUC-Berkeley, ME Dept.
Quantum Mechanics
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vs
5 g/cm3
E ≈ kT
Quantum dot
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Rayleigh Light-Scatteringof Nanocrystals
Shape, Size, and Composition Matter
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Optical Absorption
Microsystems LaboratoryUC-Berkeley, ME Dept.
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Effects of Confinement of Charge Carriers
E
D(E)
3-D 2-D
1-D
ZnO
dCdSe 4.63.63.12.42.1
d (nm)
ddCdSe 4.63.63.12.42.1
d (nm)
(Paul Alivisatos, UCB)
Example: CdSe quantum dotsFluoresces vs. wavelength
(After Arum Majumdar, UCB)
0-D
CdSe
Microsystems LaboratoryUC-Berkeley, ME Dept.
What’s going on here?
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Gold nanoparticles CdSe quantum dots
vs.
Microsystems LaboratoryUC-Berkeley, ME Dept.
Aspect Ratio
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vs
Microsystems LaboratoryUC-Berkeley, ME Dept.
39Liwei Lin, University of California at Berkeley
Electrical Properties: Tunneling Current
� At the nanometer scale, electrical insulators begin to fail to block current flow
� Quantum mechanical effect known as tunneling� Tunneling current increases exponentially as the
thickness of the insulator is decreased� Tunneling is the basis of the scanning tunneling