Scanning probe microscope principle and structure
The basic working principle of scanning probe microscope is to use the interaction between the probe and the sample surface atoms and molecules, that is, when the probe and the sample surface close to the nanometer scale when the formation of a variety of interacting physical fields, through the detection of the corresponding physical quantities and obtain the sample surface topography. Scanning probe microscope is composed of 5 parts: probe, scanner, displacement sensor, controller, detection system and image system.
Controller through the scanner in the vertical from the direction of moving the sample in order to stabilise the distance between the probe and the sample (or the physical quantity of interaction) in a fixed value; at the same time in the x-y horizontal plane to move the sample, so that the probe in accordance with the scanning path to scan the sample surface. Scanning probe microscope in the case of stabilising the distance between the probe and the sample, the detection system detects the signal of the interaction between the probe and the sample; in the case of stabilising the physical quantity of the interaction, the distance between the probe and the sample is detected by the displacement sensor in the vertical direction. The image system is based on the detection signal (or the distance between the probe and the sample) on the surface of the sample for imaging and other image processing.
Depending on the physical field of interaction between the probe and the sample, scanning probe microscopes are divided into different families of microscopes. Two of the more commonly used types of scanning probe microscopes are scanning tunneling microscopes (STM) and atomic force microscopes (AFM). Scanning Tunneling Microscopy is used to examine the surface structure of a sample by detecting the magnitude of the tunneling current between the probe and the sample under test. AFM detects the sample surface by detecting the micro-cantilever deformation caused by the interaction force between the tip of the probe and the sample (either attractive or repulsive) through the use of a photoelectric displacement sensor.
