Mass-Analysis Scanning Force Microscopy with Electrostatic Switching Mechanism

A time-of-flight scanning force microscope (SFM) probe with an ability to switch the measurement mode using the electrostatically switching mechanism is designed, fabricated and demonstrated the performance of it. In order to achieve surface observation and chemical analysis simultaneously for imaging the chemical property of a material surface, this probe can switch the positions of the cantilever between SFM mode and time-of-flight mass analysis (TOF-MA) mode by integrating a couple of electrostatic actuator with curved electrode. This mechanism will be applied to pick up an atom or molecule under SFM mode, then emits them to TOF mass analyzer using field evaporation for analyzing its mass in TOF-MA mode. To switch the cantilever position at TOF-MA mode, the fabricated probe generated the 255 mum of maximum displacement at the end of cantilever at an actuation voltage of 180 V. The cantilever is attracted with the electrode according to the curved shape using electrostatically pull-in effect. The front edge of the cantilever was aligned in front of integrated extraction electrode for emitting chemical species. In SFM mode, the cantilever was also attracted to another electrode. The fundamental resonant frequency of the cantilever is increased from 1.8 kHz to 6.8 kHz before and after actuation. A calculated spring constant is changed from 0.05 N/m to 0.34 N/m.