Conduction Band

When a solid is formed, the energy levels of the atoms broaden and form bands with forbidden gaps between them. The electrons can have energy values that exist within one of the bands, but cannot have energies corresponding to values in the gaps between the bands. The lower energy bands due to the inner atomic levels are narrower and are all full of electrons, so they do not contribute to the electronic properties of a material...........The outer or valence electrons that bind the crystal together occupy a valence band, which for an insulating material, is full of electrons that cannot move since they are fixed in position in chemical bonds. There are no delocalised electrons to carry current, sothe material is an insulator. The conduction band is far above the valence band in energy, so it is not thermally accessible, and remains essentially empty. In other words, the heat content of the insulating material at room temperatur T=300 K is not sufficient to raise an appreciable number of electrons from the valence band to the conduction band, so the number in the conduction band is negligible. Another way to express this is to say that the value of the gap energy En far exceeds the value k T of the thermal energy, where k is Boltzmann's constant.


Owens, The Physics and Chemistry of Nanosolids, p 26



In the recent studies on the optical manipulation, one of major interests is how we can manipulate the nanoscale objects with condensed matter whose size is between that of an atom and that of a micrometer object. For metallic substances, the trapping of a single 36-nm-diameter gold particle has been achieved [1]. On the other hand, as for nonmetallic particles, submicron-sized (∼220 nm) polystyrene latex particles with fluorescent dye have been trapped, gathered and fixed onto the substrate with a strongly focused laser beam [2]. However, if the particle is much smaller than the wavelength for the usual laser frequency region (diameter < 100 nm, for example), the induced polarization becomes too small and hence, the light-matter interaction becomes too weak to cause sufficiently strong force under the electronically non-resonant condition.

Takuya Iida, Optical Manipulation of Nano Materials under Quantum Mechanical Resonance Conditions; 2005; http: //ietele.oxfordjournals.org

[1] K. Svoboda and S.M. Block, “Optical trapping of metallic Rayleigh particles,” Opt. Lett., vol.19, no.13, pp.930–932 July 1994.

[2] S. Ito, H. Yoshikawa, and H.Masuhara, “Optical patterning and photochemical fixation of polymer nanoparticles on glass substrates,” Appl. Phys. Lett., vol.78, pp.2566–2568, April




Alloy-based nano-crystal texture and method of preparing same


Abstract:
To provide a very tough material at a low manufacturing cost, the present invention provides an alloy-based nano-crystal texture in which, in an alloy system having a composition deviating from the stoichiometric composition, and capable of forming an amorphous state, nano-scale crystals are arranged in an identical crystal orientation.

http://www.freepatentsonline.com/y2005/0126665.html