What's a Nanometer? A nanometer is one billionth of a meter (a meter is approximately 3 feet). Another way to think about this is in terms of relative sizes. Starting at the human scale, shrinking things by 1000X brings you to the size of a fruit fly (millimeters). Shrinking another 1000X brings you to the size of a bacteria (microns). Shrinking yet another 1000X gets you to the nano scale.
Atoms, which are the basic building blocks of materials, are on the order of 0.1 to 0.5 nm in size. Structures at the nanometer scale are therefore composed of relatively small groups of atoms. For example, the simple organic molecule shown in the figure below is composed of 8 carbon atoms (blue), 8 hydrogen atoms (white) and two sulphur atoms (yellow). Biological systems utilize structures from the nanometer to micron scale. A single turn of the DNA double helix is about 3.4 nanometers. Proteins are on the order of 10 nanometers and cells are in the range of 10 microns.
What is it good for? Some of you may recall President Clinton's last State of the Union address, where he announced the National Nanotechnology Initiative. His speech talked of nano-robots that could run through your blood stream and monitor/fix medical conditions. This may eventually happen, but is probably a long way off. In the short term, I think that nanotechnology will be incorporated into existing products in a relatively transparent way. One early application will be in new materials. Think of what happened when the materials used for tennis rackets and golf clubs changed from wood to steel, then to carbon composite. The result was lighter, more powerful equipment. My friends in chemical engineering point out that automobile tires already are made with nanoscale bits of carbon (carbon black) incorporated into the rubber. While carbon black is not controlled with the precision of the type typically described in nanotechnology, it does make your tires perform better. Nanotechnology can also play a significant role in the near future in the areas of medicine and environmental sensing. As mentioned earlier, the molecular scale processes that lead to normal metabolic functions, and to various medical conditions, are now known. Nanostructured elements may allow us to selectively find and destroy cancer cells, toxins, etc. Since molecules interact very specifically with other molecules, it should be possible to develop novel gas sensors by connecting a molecular-level event to an external circuit. My group is currently involved in developing chemical sensors based on these ideas. As I mentioned earlier, silicon microelectronics is already a nano-scale technology. I think that other nano-structured elements will be added to the microelectronic &quot;toolbox&quot; in the relatively near future -- the expanded capabilities may include optical devices for displays or interconnects, high density memories and biologically-inspired circuits.
What makes it a technology? In my opinion, nanotechnology represents the convergence of several technologies, which collectively provide the capabilities to build, characterize and assemble structures at the nanometer scale (See figure below). 1) The first technology involves chemical and biological assemblies, e.g. molecules. Chemists have know for many years how to synthesize molecules and determine their composition and structure. Simple molecules such as sugar, caffeine and aspirin are nano-scale &quot;things&quot;. Biologists and medical researchers now understand molecular-level events that are responsible for many biological processes. It is now possible to &quot;self-assemble&quot; structures of reasonable complexity using chemical affinities or selective DNA recognition. 2) The second technology involves the ability to image and manipulate matter at the atomic/molecular scale. Breakthroughs such a scanning probe microscopes provide the ability to actually image atoms on surfaces. Using such techniques, scientists and engineers have studied the electrical, mechanical, structural and heat-transfer properties of structures at the nanometer scale (and, in some cases, the properties of individual atoms). 3) The third technology is the micro/nano fabrication processing used by the semiconductor industry to create integrated circuits for computers, cell phones, memory, etc. The primary factor that allows continuous improvements in speed, cost and size is the relentless downscaling of the minimum feature sizes of the transistor (the basic building block of an integrated circuit). We have now reached the point where the minimum feature size of a MOSFET transistor is below 100 nanometers, and the gate oxide thickness in these devices is below 5 nanometers. In a very real sense, the chips in the computer you are currently using represent a form of nanotechnology. The lithographic processes (comparable to transferring a picture from a negative to a paper print) allow literally billions of transistors to be formed on a silicon wafer: quickly, cheaply and very uniformly. These capabilities provide a platform on which we can build interesting structures in a variety of areas.
070701-1 What is Nanotechnology Part I.ppt
What is “Nano-scale Science and Technology”? Yonhua Tzeng, Professor Electrical and Computer Engineering Auburn University, Alabama USA July 7, 2003
X 10 -8 X 10 -8 End Cap The Earth Soccer Ball STM Image of C60 STM image of a carbon nanotube http://www.wtec.org/loyola/nano/IWGN.Public.Brochure/IWGN.Nanotechnology.Brochure.pdf What is “Nanotechnology”?
<ul><li>Nanoparticles have been used in our daily life. </li></ul><ul><li>Carbon black ( a nanoscale carbon) is used for writing and painting and is added to rubber to make tires more wear resistance. </li></ul><ul><li>Nano phosphors in CRTs display colors. </li></ul><ul><li>Polishing compounds for smoothing silicon wafers include nanoscale alumina and silica, etc. </li></ul><ul><li>Hard disks in our computers contain nanoscale iron oxide magnetic particles. </li></ul><ul><li>Nanoscale zinc oxide and titania block UV light for sunscreens . </li></ul><ul><li>Nanoscale platinum particles are critical to the operation of catalytic converters. </li></ul><ul><li>Metallic nanoparticles make stained glass and Greek vase colorful. </li></ul><ul><li>Nanoscale thin films have also been the heart of our silicon chips for our computers, digital cameras, and photonic devices for quite a while. </li></ul>
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Atoms, Molecules, And Nano-meter Sized Particles Have Been Around For A Long,Long Time. What is new? What makes it a promising technology? What is it good for?
STM probe images of Fe atoms on Cu from IBM Almaden Research Lab http://www.almaden.ibm.com/vis/stm/atomo.html http://www-inst.eecs.berkeley.edu/~ee143/f2002/Lectures/Lec_28.pdf Small, of course!
http://cache.techtv.com/binaries/2002/smallgear.mpg http://cache.techtv.com/binaries/2002/gearandshaft.mpg How small? Atomic and Molecular Scales!
<ul><li>Definition of Nanotechnology (i): </li></ul><ul><li>The following is excerpted from the National Nanotechnology Initiative: The Initiative and its Implementation Plan (http://www.nano.gov/nni2.htm) </li></ul><ul><li>The essence of nanotechnology is the ability to </li></ul><ul><li>work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization . Compared to the behavior of isolated molecules of about 1 nm (10 -9 m) or of bulk materials, </li></ul><ul><li>behavior of structural features in the range of about 10 -9 to 10 -7 m (1 to 100 nm - a typical dimension of 10 nm is 1,000 times smaller than the diameter of a human hair) exhibit important changes. Nanotechnology is concerned with materials and systems whose structures and components exhibit </li></ul><ul><li>novel and significantly improved physical, chemical, and biological properties, phenomena, and processes due to their nanoscale size. </li></ul>
<ul><li>The goal is to exploit these properties by </li></ul><ul><li>gaining control of structures and devices at atomic, molecular, and supramolecular levels and to learn to efficiently </li></ul><ul><li>manufacture and use these devices. Maintaining the </li></ul><ul><li>stability of interfaces and the </li></ul><ul><li>integration of these "nanostructures" at micron-length and macroscopic scales are all keys to success. </li></ul>Definition of Nanotechnology (ii):
<ul><li>New behavior at the nanoscale is not necessarily predictable from that observed at large size scales. </li></ul><ul><li>The most important changes in behavior are caused not by the order of magnitude size reduction, but by newly observed phenomena intrinsic to or becoming predominant at the nanoscale . </li></ul><ul><li>These phenomena include size confinement , predominance of interfacial phenomena and quantum mechanics . </li></ul>Definition of Nanotechnology (iii):
<ul><li>Once it becomes possible to </li></ul><ul><li>control feature size , it will also become possible to </li></ul><ul><li>enhance material properties and device functions beyond what we currently know how to do or even consider as feasible. </li></ul><ul><li>Being able to </li></ul><ul><li>reduce the dimensions of structures down to the nanoscale leads to the unique properties of carbon nanotubes, quantum wires and dots, thin films, DNA-based structures, and laser emitters. </li></ul><ul><li>Such new forms of materials and devices herald a </li></ul><ul><li>revolutionary age for science and technology, </li></ul><ul><li>provided we can discover and fully utilize the underlying principles. </li></ul>Definition of Nanotechnology (iv):
Fundamental Principles <ul><li>Nanoscale Phenomena </li></ul><ul><li>Size effects </li></ul><ul><li>Confinement </li></ul><ul><li>Interfacial phenomena </li></ul><ul><li>Quantum mechanics </li></ul><ul><li>Biological systems </li></ul>
Size and Shapes : High aspect ratio of carbon nanotubes and Metal-atom filled Nanotubes Nanostructure Science : R&D Status and Trends in Nanoparticles, Nanostructured Materials, and Nanodevices (1998) http:// www.wtec.org/loyola/pdf/nano.pdf and Technology
Properties of the Carbon Nanotubes http://www.bit.ac.at/nmp/AT_F_Kooperation/02_hammel.pdf Molecular Structural Effects
Size Effects Image from Prof. Prorok, Auburn University y ASTM