Challenges in Nano technology: BACK
Although many of the fundamentals have long been established in different fields such as in physics, chemistry, materials science and device science and technology, and research on nano technology is based on these established fundamentals and technologies, researchers in the field face many new challenges that are unique to nanostructures and nano materials. Challenges in nano technology include the integration of nano structures and nano materials into or with macroscopic systems that can interface with people.
Challenges include the building and demonstration of novel tools to study at the nanometer level what is being manifested at the macro level. The small size and complexity of nanoscale structures make the development of new measurement technologies more challenging than ever. New measurement techniques need to be developed at the nanometer scale and may require new innovations in metrological technology. Measurements of physical properties of nanomaterials require extremely sensitive instrumentation, while the noise level must be kept very low. Although material properties such as electrical conductivity, dielectric constant, tensile strength, are independent of dimensions and weight of the material in question, in practice, system properties are measured experimentally. For example, electrical conductance, capacitance and tensile stress are measured and used to calculate electrical conductivity, dielectric constant and tensile strength. As the dimensions of materials shrink from centimeter or millimeter scale to nanometer scale, the system properties would change accordingly, and mostly decrease with the reducing dimensions of the sample materials. Such a decrease can easily be as much as 6 orders of magnitude as sample size reduces from centimeter to nanometer scale.
Other challenges arise in the nanometer scale, but are not found in the macro level. For example, doping in semiconductors has been a very well established process. However, random doping fluctuations become extremely important at nanometer scale, since the fluctuation of doping concentration would be no longer tolerable in the nanometer scale. With a typical doping concentration of 1018/ cm3, there will be just one dopant atom in a device of 10x10x10nm3 in size. Any distribution fluctuation of dopants will result in a totally different functionality of device in such a size range. Making the situation further complicated is the location of the dopant atoms. Surface atom would certainly behave differently from the centered atom. The challenge will be not only to achieve reproducible and uniform distribution of dopant atoms in the nanometer scale, but also to precisely control the location of dopant atoms. To meet such a challenge, the ability to monitor and manipulate the material processing in the atomic level is crucial. Furthermore, doping itself also imposes another challenge in nanotechnology, since the self purification of nanomaterials makes doping very difficult. One more challenge faced by researchers is “all the mathematical models available for macro materials are not applicable to nanoscale materials. They must be developed to predict the behaviour of nano materials.”
For the fabrication and processing of nanomaterials and nanostructures, the following challenges must be met:
1) Overcome the huge surface energy, a result of enormous surface area or large surface area to volume ratio.
2) Ensure all nanomaterials with desired size, uniform size distribution, morphology, crystallinity, chemical composition, and microstructure,that altogether result in desired physical properties.
3) Prevent nanomaterials and nanostructures from coarsening through either Ostwald ripening or agglomeration as time evolutes.