Nanostructure fabrication on germanium and silicon by nanocoining imprint technique

Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si.