Journal of Nanomedicine & Nanotechnology

Hardness of the Fe81Ga19/Si(100) film measured by the nanoindentation method

3^rd International Conference on Nanotek & Expo

December 02-04, 2013 Hampton Inn Tropicana, Las Vegas, NV, USA

Shien-Uang Jen

Scientific Tracks Abstracts: J Nanomed Nanotechnol

Abstract:

Fe81Ga19 alloy is an auxetic material, which means that its Poisson?s ratio along the [110] direction, V [110] , is negative. When this alloy is deposited on a single-crystal Si(100) wafer, the film is highly (110) textured. Thus, if we indent the film plane with a Berkovich indenter vertically, the apparent hardness obtained with the parameter V ef f = V [110] =-0.55 < 0 should be larger than that with V eff = V [110] =+0.30. This is reasonable, because if V eff is negative, the deformed material under the pressing indenter tends to push the tip slightly upward (or backward). As a result, the measured depth of circle of contact, hp, of this auxetic film is smaller than it should be under a fixed force, F, and, moreover, since the hardness H ≡ F/[24.5(hp)2], the apparent (measured) hardness must be larger. We have made a series of (Fe100-xCox) 81 Ga 19 /Si(100) films, and measured their hardness. The results indicate that: [1] when 0≤x<7 at %Co, the films (or alloys) are auxetic ( V eff <0); [2] when 7≤x≤11 at %Co, they are critical (V eff =0); and [3] when 11 0). Each point on the loading or un-loading curve was analyzed by the finite element analysis to show the side-view of the shear-stress (τ) distributions in the film, film/substrate, and substrate regions, respectively. We can study (or outline) the plastic-flow zone beneath the indenter by adopting the Tresca criterion: τ ≥ H/6

Biography :

Shien-Uang Jen has completed his Ph.D. at the age of 29 from the Physics Department of Carnegie-Mellon University. He is now a senior research fellow of the Institute of Physics, Academia Sinica. He has published more than 123 papers in reputed journals.