Working Principle and Structural Composition of Scanning Probe Microscopy
The basic working principle of a scanning probe microscope is to utilize the interactions between the probe and the atomic molecules on the surface of the sample, that is, the physical fields formed by various interactions when the probe and the sample surface approach the nanoscale, and obtain the surface morphology of the sample by detecting the corresponding physical quantities. The scanning probe microscope consists of five parts: probe, scanner, displacement sensor, controller, detection system, and imaging system.
The controller uses a scanner to move the sample in a vertical direction to stabilize the distance (or physical quantity of interaction) between the probe and the sample at a fixed value; Simultaneously move the sample in the x-y horizontal plane so that the probe scans the surface of the sample along the scanning path. Scanning probe microscope detects the relevant physical quantity signals of the interaction between the probe and the sample in the detection system, while maintaining a stable distance between the probe and the sample; In the case of stable interaction of physical quantities, the distance between the probe and the sample is detected by a displacement sensor in the vertical direction. The imaging system performs image processing on the surface of the sample based on the detection signal (or the distance between the probe and the sample).
Scanning probe microscopes are divided into different series of microscopes based on the different physical fields of interaction between the probes used and the sample. Scanning tunneling microscope (STM) and atomic force microscope (AFM) are two commonly used types of scanning probe microscopes. Scanning tunneling microscope detects the surface structure of a sample by measuring the magnitude of the tunneling current between the probe and the sample being tested. Atomic force microscopy uses a photoelectric displacement sensor to detect the micro cantilever deformation caused by the interaction force between the needle tip and the sample (which may be either attractive or repulsive) to detect the surface of the sample.
