Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of ∼50 nm and 7 mG/Hz 1/2 at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.

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In this work, the authors report on a quantitative investigation of lateral-force gradient and lateral force between a tungsten tip and Si (111) - (7×7) surface using combined noncontact lateral-force microscopy and scanning tunneling microscopy. Simultaneous lateral-force gradient and scanning tunneling microscopy images of single and multiatomic step are obtained. In our measurement, tunnel current is used as feedback. The lateral-stiffness contrast has been observed to be 2.5 Nm at a single atomic step, in contrast to 13 Nm at a multiatomic step on Si (111) surface. They also carried out a series of lateral stiffness-distance spectroscopy, which show a sharp increase in tip-surface interaction stiffness as the sample is approached toward the surface. © 2009 American Vacuum Society

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Energy dissipation plays an important role in non-contact atomic force microscopy (nc-AFM), atomic manipulation and friction. In this work, we studied atomic scale energy dissipation between a tungsten tip and Si(1 0 0)-(2 Â 1) surface. Dissipation measurements are performed with a high sensitivity nc-AFM using sub-Å ngström oscillation amplitudes below resonance. We observed an increase in the dissipation as the tip is approached closer to the surface, followed by an unexpected decrease as we pass the inflection point in the energy-distance curve. This dissipation is most probably due to transformation of the kinetic energy of the tip into phonons and heat. #