Scanning Hall probe microscope


Scanning Hall probe microscope is a variety of a scanning probe microscope which incorporates accurate sample approach and positioning of the scanning tunnelling microscope with a semiconductor Hall sensor. This combination allows mapping the magnetic induction associated with a sample. Current state of the art SHPM systems utilize 2D electron gas materials to provide high spatial resolution imaging with high magnetic field sensitivity. Unlike the magnetic force microscope the SHPM provides direct quantitative information on the magnetic state of a material. The SHPM can also image magnetic induction under applied fields up to ~1 tesla and over a wide range of temperatures.
The SHPM can be used to image many types of magnetic structures such as thin films, permanent magnets, MEMS structures, current carrying traces on PCBs, permalloy disks, and recording media

Advantages to other magnetic raster scanning methods

SHPM is a superior magnetic imaging technique due to many reasons. Unlike the MFM technique, the Hall probe exerts negligible force on the underlying magnetic structure and is noninvasive. Unlike the magnetic decoration technique, the same area can be scanned over and over again. The magnetic field caused by hall probe is so minimal it has a negligible effect on sample it is measuring. The sample does not need to be an electrical conductor, unless using STM for height control. The measurement can be performed from 5 – 500 K in ultra high vacuum and is nondestructive to the crystal lattice or structure. Tests requires no special surface preparation or coating. The detectable magnetic field sensitivity, is approximately 0.1 uT – 10 T. SHPM can be combined with other scanning methods such as STM.

Limitations

There are some shortcomings or difficulties when working with an SHPM. High resolution scans become difficult due to the thermal noise of extremely small hall probes. There is a minimum scanning height distance due to the construction of the hall probe.. The scanning height affects obtained image. Scanning large areas takes a significant amount of time. There is a relatively short practical scanning range along any direction. The housing is important to shield electromagnetic noise, acoustic noise, air flow, and static charge on the sample.