Nano Tech Lecture1 Dr. A.Waheed Anwar

Nano Tech Lecture1 Dr. A.Waheed Anwar

• 1.
  An Introduction toNano-Science & Nano-Technology Dr. Abdul Waheed Anwar Nanotechnology Research Center Department of Physics UET Lahore
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  What Is Nano? • In 1959, a physicist named Richard Feynman shared his vision that how very small things would look like and how they would behave. • In a speech at the California Institute of Technology titled “There’s Plenty of Room at the Bottom,” Feynman gave the first hint about what we now know as “nanoscience” [1] • “The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom.” [1] http://www.zyvex.com/nanotech/feynman.html
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  What Is Nano? Nanometer10-9 meter 0.000000001 meter [1 nm] One nanometer is one billionth of a meter, or the length of 10 hydrogen atoms lined up So Nanoscience and Nanotechnolgy are the science and technology of things that are 10-9 to 10-7 meters in size [1-100 nm]. Comparisons & Scaling: Biggest 1000 m = 103 m Height of tallest building Everyday Things 1 m = 100 m Height of people 0.001 m = 10-3 m size of a pinhead, smallest machined parts (currently) [visible to naked eye] 0.000001 m = 10-6 m (electronic “micro” circuitry) Small 10-7 m (bacteria) 10-8 m (viruses) 10-9 m 10-10 m diameters of atoms
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  Nano-Science & Nano-Technology Isit science? Is it technology? Nanoscience is the study of nano-materials, their properties and related phenomena. Nanotechnology is the application of nanoscience to produce devices and products.
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  What is theDifferent About Nanoscience? Just a bunch of really small things? What makes the science at the nano scale special ?  At such a small scale, all physical laws affect the behavior of matter.  Different laws dominate over those that we experience in our everyday lives. For example:  Gold (Au) has a nice yellowish-brown color to it—the color we know as “gold.”  However, if only 100 gold atoms are arranged in a cube, color would be much more red.  Color is just one property (optical) that is different at the nano scale. Other properties, such a flexibility/strength (mechanical) and conductivity (electrical) are often very different at the nano scale as well.
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  Very Large SurfaceArea Size Volume Surface Area Skyscraper (102 m)(102 m)(103 m) 2 (100 m 100 m) + 4 (100 m 1000 m) = 107 m3 = 4.2 105 m2 Person (10-1 m)(10-1 m)(1 m) 2 (0.1 m 0.1 m) + 4 (0.1 m 1 m) = 10-2 m3 = 0.42 m2 Small machine (10-3 m)(10-3 m)(10-3 m) 6 (0.001 m 0.001 m) part = 10-9 m3 = 6.0 10-6 m2 Nano-cube 10-27 m3 6 (10-9 m 10-9 m) = 6.0 10-18 m2
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  Very Large Surfaceto Volume Ratio Look at the ratio of surface area (SA) to volume (V) SA/V [m-1] Skyscraper 4.2 10-2 Person 42 Small Machine part 6000 Nano-cube 6 109 Surface Area becomes relatively more important (compared to Volume) when the things become smaller!
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  Bulk Sample In termsof the number of atoms in objects (bulk and nano), For example, the number of atoms in a micro-cube (10-6 m on an edge) 3 10-6 m = 1012 atoms 10-10 m Enough atoms to behave like a “bulk” sample. Bulk behavior = physical character of a macroscopic sample (electrical, chemical, thermal, optical properties).
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  Nano Sample Atomsin a nano-cube (10-9 m on an edge) 3 10-9 m = 103 or 1000 atoms, with about 600 at the surface! 10-10 m Not enough atoms to preserve bulk behavior. Melting, heat conduction, electrical conductivity, chemical reactivity, color, other optical properties,…all can change as we move into the nano-world. BUT does the science needed (chemistry, physics, biology) change as we approach the nano-world?
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  Nano World Quantum World Nano World Micro World Everyday World Atoms Molecules Classical Physics & Chemistry 0.1 nm 0.2 – 100 nm 103 nm 103 – 109 nm The Nano World—its science and technology—is at the boundary between the everyday world of classical science and the unusual world of Quantum Mechanics. Some Nano aspects can be handled with everyday physics & chemistry, and some nano devices can only be understood with quantum concepts.
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  Small Devices 1965, GordonE. Moore (co-founder of Intel) : number of transistors squeezed onto a computer chip roughly doubles every 18 months. This is known as “Moore’s Law.” The more transistors on a chip, the smaller their size and closer their spacing . This is why computers of room size in the 1950s now fit on your lap.
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  Nanostructures Two interesting structuresthat have been constructed and fall into the nanoscale range are carbon nanotubes and buckyballs. in Nature
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  How to “See”Nano Structures STM: Scanning Tunneling Microscope which was developed in 1981. The very end of the tip of this microscope is one atom in size.  The “tunneling” of electrons (quantum tunneling) between the tip and the substance being viewed creates a current (flow of electrons). The strength of the current and how it changes over time can be used to create an image of the surface of the substance. Today’s scanning microscopes can do much more than just see. Among other things, they can be used to move atoms around and arrange them in a preferred order.
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  How to “See”Nano Structures STM tip Surface atoms Battery powered circuit
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  How to “See”Nano Structures A different type of microscope, the atomic force microscope (AFM), uses a tiny tip that moves in response to the electromagnetic forces between the atoms of the surface and the tip. As the tip moves up and down, the motion is recorded and an electronic image of the atomic surface is formed
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  How to “See”Nano Structures As the AFM tip is attracted to the surface (causing the cantilever to bend), a laser beam bounces off the end of the cantilever—allowing the tip’s movement to be tracked. Laser ~1 m (1000 nm) The cantilever is visible to the naked eye but the AFM tip is too small to see without magnification.
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  How to “See”Nano Structures AFM tip Surface of sample The attractive van der Waals interaction acts at a molecular and atomic level, between the AFM tip and the local atoms at the sample’s surface.