ABSTRACT

The evolution of millimetric-range electrostatic force between a silicon cantilever and a negatively charged dielectric sample was studied by recording “suspended” force curves at a fixed distance on an atomic force microscope (AFM). Results show that the long-range force increases sharply at first with time, then increases moderately until reaching a global maximum, and at last decreases slightly and exponentially. The sharp increase was attributed to carrier drift at a high velocity. Moreover, a repelling electric field due to accumulated charges leads to the moderate increasing trend. In addition, the exponential decrease was attributed to charge decay on the sample surface. With the absence of the sample for a while (absent time) and presence again, the force increases sharply again with a lower value. The longer the absent time, the larger the decreasing rate. This was attributed to carrier diffusion due to the concentration difference. The proposed method can be used to measure millimetric-range electrostatic forces at a fixed distance, and investigate its evolution with time, and study the effect of some factors on the charge dissipation. Furthermore, the outcomes may suggest that charge carriers inside an AFM silicon cantilever play a part in the electrostatic force contribution.

摘要

通过在原子力显微镜 (AFM) 上记录固定距离处的“悬浮”力曲线来研究硅悬臂和带负电的介电样品之间毫米范围静电力的演变。结果表明，长程力随时间先急剧增加，然后适度增加直至达到全局最大值，最后呈指数级小幅减小。急剧增加归因于高速下的载流子漂移。此外，由于累积电荷引起的排斥电场导致适度增加的趋势。此外，指数下降归因于样品表面的电荷衰减。随着样品一段时间不存在（不存在时间）并再次存在，力再次急剧增加，值较低。不在的时间越长，下降率越大。这归因于由于浓度差异引起的载流子扩散。该方法可用于测量固定距离的毫米级静电力，并研究其随时间的演变，并研究某些因素对电荷耗散的影响。此外，结果可能表明 AFM 硅悬臂内的电荷载流子在静电力贡献中起作用。