Benefits of Scanning Probe Microscopy that are Particular
The Unique Advantages of Scanning Probe Microscope Preface:
When the history developed to the 1980s, a new type of surface analysis instrument based on physics and integrating a variety of modern technologies - scanning probe microscope (STM) was born. STM not only has a very high spatial resolution (up to O.1nm in the horizontal direction, better than O.01nm in the vertical direction), it can directly observe the atomic structure of the material surface, and it can also manipulate atoms and molecules, so that human Subjective will is imposed on nature. It can be said that the scanning probe microscope is the extension of human eyes and hands, and the crystallization of human wisdom.
The working principle of the scanning probe microscope is based on various physical characteristics in the microscopic or mesoscopic range, and detects the interaction between the two when scanning the surface of the substance to be studied by an atomically thin probe, so as to obtain the To study the surface properties of matter, the main difference between the different types of SPMs is their tip properties and their corresponding ways in which the tip interacts with the sample.
The working principle comes from the tunneling principle in quantum mechanics. Its core is a needle tip that can scan on the surface of the sample, has a certain bias voltage with the sample, and has a diameter of atomic scale. Since the probability of electron tunneling has a negative exponential relationship with the width of the potential barrier V(r), when the distance between the tip and the sample is very close, the potential barrier between them becomes very thin, and the electron clouds overlap each other. When a voltage is applied, electrons can be transferred from the tip to the sample or from the sample to the tip through the tunnel effect, forming a tunnel current. By recording the change of the tunnel current between the needle tip and the sample, the information of the surface topography of the sample can be obtained.
Compared with other surface analysis techniques, SPM has unique advantages:
(1) It has atomic-level high resolution. The resolution of STM in the direction parallel to and perpendicular to the sample surface can reach 0.1nm and 0.01nm, respectively, and single atoms can be resolved.
(2) The three-dimensional image of the surface in real space can be obtained in real time, which can be used for the study of periodic or non-periodic surface structure. This observable performance can be used for the study of dynamic processes such as surface diffusion.
(3) It is possible to observe the local surface structure of a single atomic layer, rather than the individual image or the average properties of the entire surface, so that surface defects, surface reconstruction, the morphology and position of surface adsorbents, and the changes caused by adsorbents can be directly observed. Surface reconstruction, etc.
(4) It can work in different environments such as vacuum, atmosphere, and normal temperature, and even immerse the sample in water and other solutions, without special sample preparation technology, and the detection process will not damage the sample. These features are especially suitable for the study of biological samples and the evaluation of sample surfaces under different experimental conditions, such as monitoring of heterogeneous catalytic mechanisms, superconducting mechanisms, and electrode surface changes during electrochemical reactions.
(5) Cooperating with STS (Scanning Tunneling Spectroscopy), information about the surface electronic structure can be obtained, such as the density of states at different levels of the surface, surface electron wells, changes in surface potential barriers, and energy gap structures.
