Scanning probe microscopy
SPM was founded in 1981, with the invention of the scanning tunneling microscope, an instrument for imaging surfaces at the atomic level.
[citation needed] This is largely because piezoelectric actuators can execute motions with a precision and accuracy at the atomic level or better on electronic command.
These recorded values are displayed as a heat map to produce the final STM images, usually using a black and white or an orange color scale.
Piezoelectric creep can also be a problem, so the microscope often needs time to settle after large movements before constant height imaging can be performed.
Tungsten wires are usually electrochemically etched, following this the oxide layer normally needs to be removed once the tip is in UHV conditions.
The latter is achieved by applying a bias voltage (of order 10V) between the tip and the sample, as this distance is usually 1-3 Angstroms, a very large field is generated.
The resolution of the microscopes is not limited by diffraction, only by the size of the probe-sample interaction volume (i.e., point spread function), which can be as small as a few picometres.
Unlike electron microscope methods, specimens do not require a partial vacuum but can be observed in air at standard temperature and pressure or while submerged in a liquid reaction vessel.
Like all scanning techniques, the embedding of spatial information into a time sequence opens the door to uncertainties in metrology, say of lateral spacings and angles, which arise due to time-domain effects like specimen drift, feedback loop oscillation, and mechanical vibration.
The difference between other SPM techniques and SPCM is, it exploits a focused laser beam as the local excitation source instead of a probe tip.
Techniques that enable spatially resolved optoelectronic measurements provide valuable insights for the enhancement of optical performance.
Scanning electron microscopy (SPCM) has emerged as a powerful technique which can investigate spatially resolved optoelectronic properties in semiconductor nano structures.
In SPCM, a focused laser beam is used to excite the semiconducting material producing excitons (electro-hole pairs).
These excitons undergo different mechanisms and if they can reach the nearby electrodes before the recombination takes place a photocurrent is generated.
