Force microscopy experiments with ultrasensitive cantilevers
Force microscopy experiments with ultrasensitive cantilevers
复制标题
使用超灵敏悬臂进行力显微镜实验
作者：
S. Rast;U. Gysin;P. Ruff;C. Gerber;Ernst Meyer;Dong
力显微镜实验与摆几何进行attonewton灵敏度（Rugar等2004自然43 329）。在超高真空条件下，对具有亚毫牛顿弹性常数的单晶悬臂梁进行了退火处理。发现在低于500 °C的温度下退火可以将品质因数提高一个数量级。这些超软悬臂梁的高力灵敏度用于表征安装在悬臂梁端部的小磁性和磁性颗粒。它们的磁性分析在磁场中作为温度的函数。超导样品安装在悬臂梁上的过渡是通过检测频率偏移来测量的。在临界温度以下，观察到耗散的增加。铁磁颗粒的磁矩通过具有作为磁场的函数的锁相环（PLL）的真实的时间频率检测来确定。探针和样品之间的耗散是超灵敏力测量的另一个重要因素。据发现，耗散增加在30 nm的分离。人们对这种耗散的起源知之甚少。然而，理论上预测吸附物可以增加该耗散通道（Volokitin和Wellson 2005 Phys.Rev.Lett. 94 086104）。第一个实验是在真空度为100的情况下进行的，以研究这种类型的耗散。长程耗散与长程力密切相关。的接触电位的距离依赖性被发现是一个重要的方面。
Force microscopy experiments with the pendulum geometry are performed with attonewton sensitivity (Rugar et al 2004 Nature 43 329). Single-crystalline cantilevers with sub-millinewton spring constants were annealed under ultrahigh-vacuum conditions. It is found that annealing with temperatures below 500 °C can improve the quality factor by an order of magnitude. The high force sensitivity of these ultrasoft cantilevers is used to characterize small magnetic and superconductive particles, which are mounted on the end of the cantilever. Their magnetic properties are analysed in magnetic fields as a function of temperature. The transition of a superconducting sample mounted on a cantilever is measured by the detection of frequency shifts. An increase of dissipation is observed below the critical temperature. The magnetic moment of ferromagnetic particles is determined by real time frequency detection with a phase-locked loop (PLL) as a function of the magnetic field. The dissipation between the probing tip and the sample is another important ingredient for ultrasensitive force measurements. It is found that dissipation increases at separations of 30 nm. The origins of this type of dissipation are poorly understood. However, it is predicted theoretically that adsorbates can increase this dissipation channel (Volokitin and Persson 2005 Phys. Rev. Lett. 94 086104). First experiments are performed under ultrahigh vacuum to investigate this type of dissipation. Long-range dissipation is closely related to long-range forces. The distance dependence of the contact potential is found to be an important aspect.