Browsing by Author "Ritchie, D."
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Item Open Access Integrated Piezoresistive Sensors for AFM-Guided Scanning Hall Probe Microscopy(American Institute of Physics, 2003) Brook, J.; Bending, S. J.; Pinto, J.; Oral, A.; Ritchie, D.; Beere, H.; Henini, M.; Springthorpe, A.We report the development of an advanced sensor for atomic force-guided scanning Hall probe microscopy whereby both a high mobility heterostructure Hall effect magnetic sensor and an n-Al0.4Ga0.6As piezoresistive displacement sensor have been integrated in a single III-V semiconductor cantilever. This allows simple operation in high-vacuum/variable-temperature environments and enables very high magnetic and topographic resolution to be achieved simultaneously. Scans of magnetic induction and topography of a number of samples are presented to illustrate the sensor performance at 300 and 77 K. (C) 2003 American Institute of Physics.Item Open Access Micromachined III-V cantilevers for AFM-tracking scanning Hall probe microscopy(Institute of Physics, 2003) Brook, A. J.; Bending, S. J.; Pinto, J.; Oral, A.; Ritchie, D.; Beere, H.; Springthorpe, A.; Henini, M.In this paper we report the development of a new III-V cantilever-based atomic force sensor with piezoresistive detection and an integrated Hall probe for scanning Hall probe microscopy. We give detailed descriptions of the fabrication process and characterization of the new integrated sensor, which will allow the investigation of magnetic samples with no sample preparation at both room and cryogenic temperatures. We also introduce a novel piezoresistive material based on the ternary alloy n+-Al0.4Ga0.6As which allows us to achieve a cantilever deflection sensitivity ΔR/(RΔz) = 2 × 10-6 Å-1 at room temperature.Item Open Access Scanning Hall probe microscopy (SHPM) using quartz crystal AFM feedback(American Scientific Publishers, 2007) Dede, Münir; Ürkmen, Koray; Girişen, Ö.; Atabak, Mehrdad; Oral, Ahmet; Farrer, I.; Ritchie, D.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.