Concept/Principle/Structure/Characteristics of Scanning Probe Microscope
Scanning probe microscope is a general term for various new probe microscopes (atomic force microscope, electrostatic force microscope, magnetic force microscope, scanning ion conductance microscope, scanning electrochemical microscope, etc.) developed on the basis of scanning tunneling microscope. Developed surface analysis instruments.
Principle and Structure of Scanning Probe Microscope
The basic working principle of the scanning probe microscope is to use the interaction between the probe and the surface atoms and molecules of the sample, that is, the physical fields of various interactions formed when the probe and the sample surface are close to the nanoscale, and obtained by detecting the corresponding physical quantities Sample surface morphology. The scanning probe microscope is mainly composed of five parts: probe, scanner, displacement sensor, controller, detection system and image system.
The controller moves the sample in the vertical direction through the scanner so that the distance between the probe and the sample (or the physical quantity of interaction) is stabilized at a fixed value; at the same time, the sample is moved in the x-y horizontal plane so that the probe follows the scanning The path scans the sample surface. In scanning probe microscopy, when the distance between the probe and the sample is stable, the detection system detects the relevant physical quantity signal of the interaction between the probe and the sample; when the physical quantity of the interaction is stable, it is detected by the displacement sensor through the vertical direction The distance between the probe and the sample. The image system performs image processing such as imaging on the surface of the sample according to the detection signal (or the distance between the probe and the sample).
Scanning probe microscopes are divided into different series of microscopes according to the different physical fields of the interaction between the probe and the sample. Among them, scanning tunneling microscope (STM) and atomic force microscope (AFM) are two types of scanning probe microscopes that are more commonly used. The scanning tunneling microscope detects the surface structure of the sample by detecting the size of the tunnel current between the probe and the sample to be tested. The atomic force microscope detects the surface of the sample by detecting the deformation of the micro-cantilever caused by the interaction force between the tip and the sample (which may be attractive or repulsive) by a photoelectric displacement sensor.
Features of Scanning Probe Microscopes
Scanning probe microscopy is the third microscope for observing the structure of matter at the atomic scale after field ion microscopy and high-resolution transmission electron microscopy. Taking Scanning Tunneling Microscope (STM) as an example, its lateral resolution is 0.1~0.2nm, and its vertical depth resolution is 0.01nm. Such resolution can clearly observe single atoms or molecules distributed on the surface of the sample. At the same time, the scanning probe microscope can also conduct observation research in air, other gases or liquid environments.
Scanning probe microscopes have the characteristics of atomic resolution, atomic transport, and nano-microprocessing. However, due to the different working principles of various scanning microscopes in detail, the information on the surface of the sample reflected by the results obtained by them is very different. Scanning tunneling microscopy measures the distribution information of electron stations on the surface of the sample, which has atomic-level resolution but still cannot obtain the true structure of the sample. The atomic microscope detects the interaction information between atoms, so the arrangement information of the atomic distribution on the sample surface can be obtained, that is, the real structure of the sample. But on the other hand, the atomic force microscope cannot measure the electronic state information that can be compared with the theory, so the two have their own advantages and disadvantages.
