Development, fabrication and characterization of graphene and bismuth hall sensors for scanning hall probe microscopy

Official URL: http://risc01.sabanciuniv.edu/record=b1606654 (Table of Contents)

Scanning Hall Probe Microscopy (SHPM) is a powerful magnetic imaging technique which provides high magnetic field and spatial resolution, simultaneously with the topography of magnetic and superconducting materials. It is a quantative method which can be operated under high magnetic fields and a wide temperature range. The Hall sensor which is sensitive to the perpendicular component of the magnetic field emanating from the specimen determines resolution. In this work, single layer Graphene Hall Probes (GHP) were fabricated using Chemical Vapor Deposition (CVD) grown graphene on copper foils, transferred to Silicon wafers. The Hall coefficient and field sensitivity of GPHs were measured to be 0.18 Ω/G and 0.20 G/√Hz, respectively, for a 3 μA drive current at room temperature. For the first time, GHP is successfully used for magnetic imaging in 3–300 K range in SHPM with quartz crystal Atomic Force Microscopy (AFM) feedback. This study has demonstrated that graphene is an alternative material to be used for magnetic imaging in SHPM. Alternatively, Bismuth based Hall probes are also fabricated by advanced lithographic techniques. Since Bismuth is a semimetal with low carrier concentration, it has been considered as a promising Hall sensor material. For the first time, SHPM images of NdFeB demagnetized magnet were acquired using Bi hall sensor fabricated by Electron Beam Lithography (EBL) with quartz crystal AFM feedback.