Temperature dependence of microscale adhesion force between solid surfaces using an AFM

The adhesion force between two solid surfaces is of great interest with the rapid development of micro–nanodevices and instruments. The effect of temperature on the microscale adhesion force has been studied by recording force–displacement curves with an atomic force microscope. A flat tip with a diameter ~1.73 μm was used to prevent wear. The adhesion force measurements were carried out under ambient conditions and in a nitrogen-filled glove box. The substrate temperature was varied between 30 and 200 °C. The results show that when the temperature is <200 °C, the influence of temperature on the normal spring constant of the cantilever can be ignored. In this temperature range, the adhesion force distribution for each temperature exhibits a Gaussian-like distribution under both situations. Under ambient conditions, the mean adhesion force first increases with the increase in temperature and reaches the maximum at ~100 °C. Then the adhesion force begins to decline slightly. At about 150 °C, the adhesion force decreases dramatically, and remains relatively stable at high temperatures. The increase in adhesion force is associated with the capillary force. The elevated temperature leads to larger and more numerous liquid bridges. The capillary nucleation, the diffusion of water molecules, and the flow of thin water film are all enhanced with the elevated temperature. However, in dry nitrogen, the mean adhesion force decreases with the increase in temperature. This trend is attributed to the broken van der Waals bonds.