Browsing by Subject "Scanning Hall Probe Microscopy"

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Open Access
Development of nano hall sensors for high resolution scanning hall probe microscopy
(2008-09) Dede, Münir
Scanning Hall Probe Microscopy (SHPM) is a quantitative and non invasive method of local magnetic field measurement for magnetic and uperconducting materials with high spatial and field resolution. Since its demonstration in 1992, it is used widely among the scientific community and has already commercialized. In this thesis, fabrication, characterization and SHPM imaging of different nano-Hall sensors produced from heterostructure semiconductors and Bismuth thin films with effective physical probe sizes ranging between 50nm‐1000nm, in a wide temperature range starting from 4.2K up to 425K is presented. Quartz crystal tuning fork AFM feedback is demonstrated for the first time for SHPM over a large temperature range. Its performance has been analyzed in detail and experiments carried with 1×1μm Hall probes has been successfully shown for a hard disk sample in the temperature range of 4.2K to 425K. Other samples, NdFeB demagnetized magnet, Bi substituted iron garnet and, single crystal BSCCO(2212) High Temperature superconductor were also imaged with this method to show the applicability of the method over a wide range of specimens. By this method, complex production steps proposed in the literature to inspect the non‐conductive samples were avoided. A novel Scanning Hall probe gradiometer has also been developed and a new method to image x, y & z components of the magnetic field on the sample surface has been demonstrated for the first time with 1μm resolution. 3D field distribution of a Hard Disk sample is successfully measured at 77K using this novel approach to prove the concept.
Open Access
Fabrication and characterization of GaAs and InAs hall sensors
(2004) Özdemir, Serdar
Scanning Hall Probe Microscopy has become a widely used method for magnetic field measurements in the last decade. For Scanning Hall Probe Microscopy, low noise Hall sensors are fabricated from GaAs and InAs structures using optical lithography techniques. Noise analysis of both types of sensors are done at 77 K and 300 K for various Hall currents. Minimum detectable magnetic fields are calculated from these noise measurements. The range of the Hall currents that makes the sensors work most efficiently are also calculated.
Open Access
Scanning hall probe microscopy (SHPM) using quartz crystal AFM feedback
(2005) Ürkmen, Koray
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 ~50nm & 7mG/ Hz at room temperature. In the SHPM technique, Scanning Tunneling Microscope (STM) or Atomic Force Microscope (AFM) feedback is usually used for bringing the Hall sensor into close proximity of the sample. In the latter, the Hall probe has to be integrated with an AFM cantilever in a complicated microfabrication process. In this work, we have eliminated the difficult cantileverHall probe integration process; a Hall sensor is simply glued at the end of Quartz crystals, which are used as a force sensor. The sensor assembly is dithered at the resonance frequency and the quartz force sensor output is detected with a Lock-in and PLL system. SHPM electronics is modified to detect AFM topography and the phase, along with the magnetic field image. NIST MIRS (Magnetic Referance Sample) (Hard Disk) sample, 100 MB high capacity zip disk and Garnet sample are imaged with the Quartz Crystal AFM feedback and the performance is found to be comparable with the SHPM using STM feedback. Quartz Crystal AFM feedback offers a very simple sensor fabrication and operation in SHPM. This method eliminates the necessity of conducting samples for SHPM.