Scanning gate microscopy
Encyclopedia
Scanning gate microscopy (SGM) is a scanning probe microscopy
technique with an electrically conductive tip used as a movable gate that couples capacitively to the sample and probes electrical transport on the nanometer scale. Typical samples are mesoscopic devices, often based on semiconductor
heterostructures, such as quantum point contacts or quantum dot
s. Carbon nanotube
s too have been investigated.
In SGM one measures the sample's electrical conductance as a function of tip position and tip potential. This is in contrast to other microscopy techniques where the tip is used as a sensor, e.g., for forces.
SGMs were developed in the late 1990s from atomic force microscope
s. Most importantly, these had to be adapted for use at low temperatures, often 4 kelvin
s or less, as the samples under study do not work at higher temperatures. Today an estimated number of ten research groups worldwide use the technique.
Scanning probe microscopy
Scanning Probe Microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a...
technique with an electrically conductive tip used as a movable gate that couples capacitively to the sample and probes electrical transport on the nanometer scale. Typical samples are mesoscopic devices, often based on semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
heterostructures, such as quantum point contacts or quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
s. Carbon nanotube
Carbon nanotube
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
s too have been investigated.
In SGM one measures the sample's electrical conductance as a function of tip position and tip potential. This is in contrast to other microscopy techniques where the tip is used as a sensor, e.g., for forces.
SGMs were developed in the late 1990s from atomic force microscope
Atomic force microscope
Atomic force microscopy or scanning force microscopy is a very high-resolution type of scanning probe microscopy, with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit...
s. Most importantly, these had to be adapted for use at low temperatures, often 4 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s or less, as the samples under study do not work at higher temperatures. Today an estimated number of ten research groups worldwide use the technique.