Keywords: scanning electron microscope SEM、 Surface morphology, energy spectrum analysis, 3D reconstruction

Scanning electron microscope (SEM) scans the surface of a sample with an electron beam to detect secondary or backscattered electron signals, generating high-resolution surface images. Its core advantages include large depth of field, high resolution, and elemental analysis capabilities, which are widely used in materials science, geology, and semiconductor industry.

1、 The core structure and imaging mode of SEM

The SEM system consists of an electron gun, scanning coil, detector, and signal processing unit. The electron beam scans the sample surface point by point, the secondary electron detector collects surface morphology information, and the backscattered electron detector reflects atomic number differences. For example, in metal fracture analysis, secondary electron images can clearly display the dimple structure, while backscattered electron images reveal the distribution of second phase particles.

2、 Energy dispersive spectroscopy (EDS): from morphology to composition

SEM combined with energy dispersive spectroscopy (EDS) can achieve micro elemental analysis. For example, in geological samples, EDS can quickly identify mineral composition; In semiconductor device failure analysis, EDS can locate the source of contaminating elements. The latest generation of silicon drift detectors (SDD) has increased the energy resolution to 125 eV and a detection limit of 0.1 wt%.

3、 3D reconstruction technology: from surface to interior

Traditional SEM only provides two-dimensional surface information. 3D reconstruction technology achieves internal structure visualization through the following methods:

Focused ion beam (FIB) slicing: Cut the sample layer by layer and image it to reconstruct a three-dimensional model.

Dual beam SEM: Combining electron beam and ion beam to achieve nanoscale cutting and imaging.

In the research of battery materials, dual beam SEM can analyze the pore structure and crack propagation path of electrode particles, providing a basis for performance optimization.

4、 Technological Challenges and Future Trends

The current challenges include sample conductivity requirements, charging effects, and radiation damage. Future development directions include:

Low voltage SEM: Reduce the acceleration voltage to below 1 kV to minimize sample damage.

Environmental SEM: Observing moist samples in a gas environment to expand biological applications.

Machine learning assisted analysis: Automatically identify defect types and sizes to improve detection efficiency.