Measurements of Interface Stress of Silicon Dioxide in Contact with Water-Phenol Mixtures by Bending of Microcantilevers

摘要

We use the bending of silicon microcantilevers to measure changes in mechanical stress at interfaces between phenol-water mixtures and SiO_2.The curvature of the microcantilever is measured by an optical system that combines a rapidly scanning laser beam,a position-sensitive detector,and lock-in detection to achieve a long-time stability on the order of 6 mN m~(-1) over 4 h and a short-time sensitivity of better than 1 mN m~(-1).Thermally oxidized Si shows the smallest changes in interface stress as a function of phenol concentration in water.For hydrophilic SiO_2 prepared by chemical treatment,the change in interface stress at 5 wt % phenol in water is larger than that of thermally oxidized Si by -60 mN m~(-1);for SiO_2 formed by exposure of the silicon microcantilever to ozone,the change in surface stress is larger than that of thermally oxidized Si by -330 mN m~(-1).