Tunable Spatial Resolution of a Scanning Probe Microscopy (SPM) by an Efficient Cryosorption Pump

Scanning probe microscopy (SPM) is a useful instrument to study the surface topography of the sample at an atomic resolution. SPM system is sensitive to vibration and contamination on the surface, and therefore a vibration-free and clean environment are required to improve spatial resolution in Z-height. In this article, a detailed new design of stand-alone cost-effective, vibration-free activated carbon-based cryosorption pump integrated and its detailed integration with the SPM system is discussed. The efficiency of cryosorption pump depends on the radial temperature distribution, which was analyzed using transient thermal analysis in Ansys software. The temperature profile obtained from the thermal simulation results reveals that a spiral wound copper mesh-based partition surrounding the activated carbon in the cryosorption pump improves the temperature distribution in the radial direction. The pump can operate with a maximum of 25 L of liquid nitrogen consumption and 4.5 h of continuous operation. The activated carbon was used as an adsorbent showed a hexagonal crystal structure from the X-ray diffraction (XRD) studies and its average pore size was obtained from by Brunauer-Emmett-Teller (BET) analysis was 0.34 nm. These tests were conducted to determine the effect on the pump-down characteristics of the developed cryosorption pump. The improvement in spatial resolution was studied through detailed experimental analysis in conductive atomic force microscopy (CAFM) by piezo force microscopy (PFM) which showed a 50% decrease of the current when imaged in a vacuum environment, phase and magnitude images showed less distorted and clear visibility of the piezo domains. The magnetic interaction by magnetic force microscopy (MFM) Q-factor was studied at the resonance frequency of 61.5 kHz. MFM showed that the Q-factor improved from 20 to 500 at 1E-3 mbar operating pressure. The drift of the MFM tip with respect to holding time showed a saturated Q-factor at 500. Noncontact mode by atomic force microscopy (AFM) showed a spatial resolution enhancement of 0.89 nm.