We describe probes of a local electric field, which are capable of detecting an electric charge as small as the charge of one electron e, operational under ambient conditions and having a spatial resolution down to 100nm. The submicron-sized probes were made from a high-density high-mobility two-dimensional electron gas, which is sensitive to the presence of electric charges near its surface. We demonstrate the possibility of using such microprobes for life-science applications by measuring an electric response of individual yeast cells to abrupt changes in their environment.

We report on mesoscopic Hall sensors made from various materials and their suitability for accurate magnetization studies of submicron samples over a wide temperature range and, especially, at room temperature. Among the studied devices, the best stability and sensitivity have been found for Hall probes made from a high-concentration two-dimensional electron gas ͑HC-2DEG͒. Even at 300 K, such submicron probes can reliably resolve local changes in dc magnetic field of Ϸ1 G, which corresponds to a flux sensitivity of less than 0.1 0 ( 0 ϭh/e is the flux quantum͒. The resolution increases 100 times at temperatures below 80 K. It is also much higher for the detection of ac magnetic fields because resistance fluctuations limiting the low-frequency stability of the studied devices can be eliminated. Our second choice for room-temperature Hall micromagnetometry is gold Hall probes, which can show a sensitivity of the order of 10 G. The capabilities of HC-2DEG and gold micromagnetometers are demonstrated by measuring nm-scale movements of individual domain walls in a ferromagnet.

No abstract

Articles you may be interested inFrequency response of cantilever beams immersed in compressible fluids with applications to the atomic force microscope J. Appl. Phys. 106, 094904 (2009); 10.1063/1.3254191 Frequency response of cantilever beams immersed in viscous fluids near a solid surface with applications to the atomic force microscope J. Appl. Phys. 98, 114913 (2005); 10.1063/1.2136418Torsional frequency response of cantilever beams immersed in viscous fluids with applications to the atomic force microscope

No abstract