Fabrication of Diamond-Like Carbon Nanosprings by Focused-Ion-Beam Chemical Vapor Deposition and Evaluation of Their Mechanical Characteristics

Abstract

Our investigation of diamond-like carbon (DLC) nanosprings with a 130 nm spring-section diameter, which were fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD), showed for the first time that nanosprings can be stretched. We observed large displacements of the FIB-CVD nanosprings using in situ optical microscopy; in other words, the nanosprings showed behavior similar to that of macroscale springs. In addition, we investigated the dependence of the spring constant of DLC nanosprings on spring diameter. The spring constants, measured using commercially available cantilevers, ranged from 0.47 to 0.07 N/m. The diameter dependence of spring constant can be accurately expressed by the conventional formula for a coil spring. The estimated shear modulus of the DLC nano-springs was about 70 GPa. This value is very close to the value of conventional coil springs made of steel. Furthermore, we measured the stiffness of a DLC nanospring annealed at 1000◦C in vacuum. The stiffness was decreased to approximately half of the stiffness of the nanospring without annealing. key words: nanospring, diamond-like carbon, focused ion beam, chemical vapor deposition, mechanical characteristics