Environmental Scanning Electron Microscopy

The environmental scanning electron microscope is an analytical instrument used in the fields of physics, earth science, and material science. It is an important branch of the scanning electron microscope. The environmental scanning electron microscope is equipped with In high vacuum, in addition to testing conductive and thermally conductive or conductively treated dry solid samples, it can also be used as a low-vacuum scanning electron microscope to directly detect non-conductive and thermally conductive samples without processing, but only backscattered electron images can be obtained in low vacuum.

While electron microscopy (EM) has long been the benchmark for the structural analysis of materials, it is limited to samples that are stable under vacuum. This is often not representative of the conditions experienced by the material in its native operating environment and can limit your understanding of its properties and behavior. Therefore, high-resolution imaging and analysis under multiple experimental and environmental conditions are required to obtain truly relevant observations. It is also best to minimize sample preparation as much as possible to keep the material pristine.

Environmental Scanning Electron Microscopy (ESEM) extends the boundaries of traditional SEM to gain a deeper understanding of all types of samples. ESEM enables the imaging of samples with as little preparation as possible and adds variables such as hydration, thermal cycling, and introduced gases to characterize in situ dynamics. Using the Water Vapor and Temperature Console, it is now easy to characterize some “impossible to image samples”, such as dirty (highly outgassed) and naturally hydrated samples (whose properties will change as they dry).

The air pressure in the sample chamber of the environmental scanning electron microscope can be greater than the saturated vapor pressure of water at normal temperature, and the dynamic process of phase transitions such as dissolution, solidification, and crystallization of the sample can be observed in the range of -20 to +20°C.

The environmental scanning electron microscope can observe the morphology and qualitative and quantitative analysis of various solid and liquid samples, and observe the phase transition process of some solutions.

For biological samples, water-containing samples, and oil-containing samples, neither dehydration nor conductive treatment such as carbon spraying or gold is required, and secondary electron images can be directly observed and elemental components analyzed in a natural state.

It can also analyze biological samples and non-conductive samples (backscattering and secondary electron images), analyze liquid samples, and observe the solid-liquid phase transition process within ± 20 °C.

Environmental Scanning Electron Microscope (ESEM) is a scanning electron microscope that operates under high humidity and high vacuum conditions, and can observe biological samples, atmospheric samples, liquid samples and other samples that are not easy to observe under traditional scanning electron microscopes. Key features of ESEM include:

• 1. Operation under high humidity and high vacuum conditions: ESEM can work under relative humidity up to 100%, so it can observe biological and material samples with high moisture content. At the same time, ESEM can also work under high vacuum to observe samples that are not easy to observe under a conventional scanning electron microscope.
• 2. No need for sample processing: ESEM does not need any processing when observing the sample, so it can avoid the change of the sample during the processing, so as to observe the real situation of the sample more accurately.
• 3. High-resolution imaging: ESEM can provide the same high-resolution imaging as traditional scanning electron microscopes, and can observe details such as surface morphology and microstructure of samples.
• 4. Spectral analysis: ESEM can also perform X-ray energy spectral analysis to obtain information on elements in the sample.
• 5. Adjustable working parameters: ESEM can adjust working parameters, such as electron beam energy, electron beam focus, detector signal amplification, etc., to adapt to different types of samples.

Powder, liquid, film, and block can be tested. The powder sample is about 10mg, and the block sample requires a length and width of less than 1cm and a thickness of less than 1cm.

• For powder samples, conventional powders are directly attached to the conductive adhesive for testing. If you need to test after dispersion, please explain in advance;

• For liquid samples, the test teacher randomly selects and drops them on the conductive glue, silicon wafer or aluminum foil according to the sample requirements and laboratory conditions. If there are any specified requirements, please explain in advance;

• For film or block, please indicate the test surface. If you need to test the cross section, please prepare the cross section by yourself or explain in advance.

It is only for material samples, biological samples and other samples. The samples are required to be non-toxic, non-radioactive, thermally stable, and resistant to electron beam bombardment.

• Is the sample conductive?

For non-conductive or poorly conductive samples, it is recommended to do gold spray treatment (to enhance the conductivity of the sample). The default gold spray time is 50s. If you need to extend the gold spray time or carbon spray, please explain in advance

• Is the sample magnetic?

Magnetic particles are easy to adsorb to the pole piece. In principle, electron microscopes (SEM and TEM) do not take magnetic samples.

According to the experience of different teachers, the acceptance of the magnetic strength of the samples taken is different, so please be sure to fill in the truth whether the sample contains magnetism and the strength of the magnetism.

In order to make it easier for everyone to distinguish between magnetism and strength, the following simple and crude definitions are made: non-magnetic, magnetic (weak magnetic, strong magnetic).

The samples containing iron, cobalt, and nickel are all magnetic samples. If the magnet can be attracted, it is a strong magnetism, and if the magnet cannot be absorbed, it is a weak magnetism.

Remarks: There are hard magnetism and soft magnetism in magnetism. Some materials do not exhibit magnetism to the outside, but are easily magnetized when a magnetic field is applied, and the magnetism increases after heating.

Summary

ESEM is mainly used in biology, material science, environmental science and other fields, and can observe biological tissues, plants, insects, cellulose materials, soil, particles in the air, etc.