Quasi-static/cyclic loading tests of nanometric SiO2 wires using AFM technique for NEMS designs

This research carried out intermediate temperature quasi-static/cyclic loading tests of nanometric silicon dioxide wires (SiO₂ nano-wires) using AFM, for revealing specimen size and temperature effects on mechanical properties and fatigue lives of the wires. Four kinds of the SiO₂ nano-wires with widths from 230 nm to 800 nm were prepared by a thermal oxidation of nanometric single crystal silicon wires (SCS nano-wires). Quasi-static bending tests using AFM examined Young´s modulus, fracture stress and strain of the wires at temperatures ranging from 295 K to 573 K in high vacuum. All of the SiO₂ nano-wires fractured in a brittle manner at the test temperatures. Young´s moduli of the nano-wires agreed with that of bulk silica, which showed that the modulus had no specimen size effect. However, fracture stress and strain of the SiO₂ nano-wires changed with not only temperature but also specimen size. Cyclic bending tests in AFM using the 230 nm- and 410 nm-wide SiO₂ wires investigated high cycle fatigue lives of the wires at room temperature. The number of cycles to failure of the 230 nm-wide wires was slightly larger than that of the 410 nm-wide wires at the loading frequency of 50 Hz and 450 Hz. This is suggestive of existing of the specimen size effect on the fatigue lives of the SiO₂ nano-wires.