Physics of Nanotechnologies

Class(es): BS 8th, MSc 4th

Course Code(s): PHYS-412, PHYS-6133

Credit Hours: 3

Introduction:

Technology has to do with the application of scientific knowledge to the economic (profitable) production of goods and services. This course is concerned with the size or scale of working machines and devices in different forms of technology. It is particularly concerned with the smallest devices that are possible, and equally with the appropriate laws of nanometer-scale physics: “nanophysics ”, which are available to accurately predict behaviour of matter on this invisible scale. Physical behaviour at the nanometer scale is predicted accurately by quantum mechanics, represented by Schrodinger’s equation. Schrodinger’s equation provides a quantitative understanding of the structure and properties of atoms. Chemical matter, molecules, and even the cells of biology, being made of atoms, are therefore, in principle, accurately described (given enough computing power) by this well tested formulation of nanophysics.

There are often advantages in making devices smaller, as in modern semiconductor electronics. What are the limits to miniaturization, how small a device can be made? Any device must be composed of atoms, whose sizes are the order of 0.1 nanometer. Here the word “nanotechnology” will be associated with human designed working devices in which some essential element or elements, produced in a controlled fashion, have sizes of 0.1nm to thousands of nanometers, or, one Angstrom to one micron. There is thus an overlap with “microtechnology” at the micrometer size scale. Microelectronics is the most advanced present technology, apart from biology, whose complex operating units are on a scale as small as micrometers.

Although the literature of nanotechnology may refer to nanoscale machines, even “self-replicating machines built at the atomic level”, it is admitted that an “assembler breakthrough” will be required for this to happen, and no nanoscale machines presently exist. In fact, scarcely any micrometer mm scale machines exist either, and it seems that the smallest mechanical machines readily available in a wide variety of forms are really on the millimeter scale, as in conventional wristwatches.

The reader may correctly infer that Nanotechnology is presently more concept than fact, although it is certainly a media and funding reality. That the concept has great potential for technology, is the message to read from the funding and media attention to this topic.

The idea of the limiting size scale of a miniaturized technology is fundamentally interesting for several reasons. As sizes approach the atomic scale, the relevant physical laws change from the classical to the quantum-mechanical laws of nanophysics. The changes in behaviour from classical, to “mesoscopic”, to atomic scale, are broadly understood in contemporary physics, but the details in specific cases are complex and need to be worked out. While the changes from classical physics to nanophysics may mean that some existing devices will fail, the same changes open up possibilities for new devices.

A primary interest in the concept of nanotechnology comes from its connections with biology. The smallest forms of life, bacteria, cells, and the active components of living cells of biology, have sizes in the nanometer range. In fact, it may turn out that the only possibility for a viable complex nanotechnology is that represented by biology. Certainly, the present understanding of molecular biology has been seen as an existence proof for “nanotechnology” by its pioneers and enthusiasts. In molecular biology, the “self replicating machines at the atomic level” are guided by DNA, replicated by RNA, specific molecules are “assembled” by enzymes and cells are replete with molecular scale motors, of which kinesin is one example. Ion channels, which allow (or block) specific ions (e.g., potassium or calcium) to enter a cell through its lipid wall, seem to be exquisitely engineered molecular scale devices where distinct conformations of protein molecules define an open channel vs. a closed channel.

Biological sensors such as the rods and cones of the retina and the nanoscale magnets found in magnetotactic bacteria appear to operate at the quantum limit of sensitivity. Understanding the operation of these sensors doubtless requires application of nanophysics. One might say that Darwinian evolution, a matter of odds of survival, has mastered the laws of quantum nanophysics, which are famously probabilistic in their nature. Understanding the role of quantum nanophysics entailed in the molecular building blocks of nature may inform the design of man-made sensors, motors, and perhaps much more, with expected advances in experimental and engineering techniques for nanotechnology.

In the improbable event, that engineering, in the traditional sense, of molecular scale machines becomes possible, the most optimistic observers note that these invisible machines could be engineered to match the size scale of the molecules of biology. Medical nanomachines might then be possible, which could be directed to correct defects in cells, to kill dangerous cells, such as cancer cells, or even, most fancifully, to repair cell damage present after thawing of biological tissue, frozen as a means of preservation.

Course Outline:

Introduction: The Importance of Nanoscale, Moore's law, Nanotechnology/Top down and bottom up approaches of nanofabrication, Advances in Nanotechnology, Advantages of nanotechnology, Future prospects in nanoscience and nanotechnology, Societal impact of nanotechnology, Two Dimensional Nanomaterials Growth: Thin film growth, Epitaxial growth modes, Thin film growth techniques : Pulsed laser deposition (PLD), Molecular beam epitaxy (MBE), Sputter deposition, Chemical vapour deposition (CVD), Electron beam evaporation (EBE) etc. Zero & One Dimensional Nanostructures Fabrication Techniques: Lithography : Mask lithography : Optical lithography, Nanoimprint, Maskless lithography : Scanning electron beam lithography, Focussed ion beam lithography, Nanostructures characterization techniques: Surface analysis by microscopy techniques : Optical microscopy (Conventional light microscopy, Fluorescence microscopy etc.), Electron microscopy (Scanning electron microscopy, Transmission electron microscopy, Focus ion beam microscopy etc.), Scanning probe microscopy (Scanning tunneling microscopy, Atomic force microscopy, Near-field scanning optical microscopy), Elemental Composition/Structural analysis : Electron techniques (Reflection high energy electron diffraction, Low energy electron diffraction, Auger electron spectroscopy etc.) and X-ray techniques (X-ray diffraction, X-ray reflectivity, X-ray photoelectron spectroscopy etc.).

Recommended Books:

Edward L. Wolf: Nanophysics and Nanotechnology, An introduction to Modern Concept in Nanoscience, Wiley VCH, 2004.
Par Mark A. Ratner, Daniel Ratner, Nanotechnology: A Gentle Introduction to the Next Big Idea, Prentice Hall Professional, 2003.
J I Goldstein et al, Scanning Electron Microscopy and X-ray Microanalysis,Kluwer Academic/Plenum Publishers, 2003.
David B. Williams and C. Barry Carter, Transmission electron microscopy : a textbook for materials science, Springer US, 2nd Edition 2009.
Andrew Zangwil, Physics at surfaces, Cambridge University Press, NY, 1988.