ABSTRACT
Three-dimensional molecular dynamics simulations are conducted to study the nanometric cutting of germanium. The phenomena of extrusion, ploughing, and stagnation region are observed from the material flow. The uncut thickness which is defined as the depth from bottom of the tool to the stagnation region is in proportion to the undeformed chip thickness on the scale of our simulation and is almost independent of the machined crystal plane. The cutting resistance on (111) face is greater than that on (010) face due to anisotropy of germanium. During nanometric cutting, both phase transformation from diamond cubic structure to ß-Sn phase and direct amorphization of germanium occur. The machined surface presents amorphous structure.
ABSTRACT
Nanostructure surface composed of tetrapod-like structure with the period of about 2 microm has been made by simple nanoprinted method, the collodion was poured directly on the surface of the template and tore off after it became solidification, and then a layer of gold was sputtered on the collodion surface. The electric field distributions of the tetrapod-like structure with different size and period have been simulated using finite element method. Surface-enhanced Raman spectra mapping image gotten from the substrates illustrated the uniform enhancement property of it. The diluted aqueous solution of Rhodamine 6G (50 nM) was used to test the enhanced property of substrates for trace detection and good quality spectra has been gotten. The spectra of melamine with the concentration of 1 mg/L (7.9 microM) on the substrates were gotten to show the enhanced ability for molecule with small Raman scattering cross section.
