SEM Coaters | Coating Techniques for SEM

SEM Coaters | Coating Techniques for SEM

SEM Coaters

Imaging samples by the scanning electron microscopy (SEM) typically requires coating a conductive thin film on the sample as a preparation step. Vac Coat Ltd. offers different SEM coater systems based on PVD techniques working at low or high vacuum conditions.

Why SEM Samples Should be Coated?

Scanning electron microscopy (SEM) is a versatile technique for imaging micro or nano-sized structures employing a beam of energetic electrons. The samples to be studied by SEM imaging should be conductive to prevent damage to the sample by electrons build-up on its surface, resulting in charging and heating it up. Therefore, coating the scanning electron microscope samples’ surface with a thin conductive film is a crucial step in the SEM sample preparation procedure. This nanometer-sized conductive thin layer can be deposited through physical vapor deposition (PVD) methods, such as sputtering and thermal evaporation techniques, as in Vac Coat SEM coaters.

Common Coating Techniques for SEM Sample Preparation

Common Coating Techniques for SEM Sample Preparation: Sputtering
Common Coating Techniques for SEM Sample Preparation: Thermal Evaporation
Common Coating Techniques for SEM Sample Preparation: Carbon Coating

1- Sputtering for SEM Coaters: SEM Sputter Coaters

Sputtering deposition is a physical vapor deposition method in which high-energy plasma particles, ions, and electrons, eject the molecules/atoms from the target material surface, which are then accumulated on the substrate to form a thin layer of the target atoms (You can read about Vacuum Plasma Treatment hear).

Vac Coat ion sputtering coaters for SEM sample preparation work under low and high-vacuum conditions for deposition of oxidizing and non-oxidizing materials. Low vacuum magnetron SEM sputter coaters are suitable to produce the common gold coatings for scanning electron microscopy and also are the right choice for the deposition of other non-oxidizing metals such as platinum (pt). Vac Coat magnetron desk sputter coater DSR1 is an ideal choice when a low-vacuum scanning electron microscopy coating is required.

However, high vacuum turbo-pumped SEM coaters provide the proper conditions for the deposition of oxidizing metals, like tungsten, iridium, and chromium. Also, sputter coating for SEM samples at higher vacuum levels results in forming a layer with a finer grain size, which is ideal for FESEM imaging (Read more here).

Vac Coat DST1-170 and DST1-300 with a small and large chamber, respectively, are capable of high-vacuum sputtering deposition of a wide range of materials and producing fine-grain-sized FESEM coatings.

2- Thermal Evaporation in SEM Coaters

Thermal evaporation of various conductive materials and deposition of the vaporized source on the sample is a well-known method for SEM sample coating. In this way, different sources like metals and carbon are resistively heated and vaporized to form a conductive coating on the SEM sample.

Sputtering of SEM Samples vs Thermal Evaporation

The deposition process in this method takes more time and requires high-vacuum conditions compared to the sputter coating of SEM samples, whereas a more uniform coating that can penetrate a porous sample is provided. DTE and DTT are two Vac Coat desktop high-vacuum deposition systems with small and large chambers, respectively, suitable for thermal evaporation of different material sources.

3- Carbon Coating for Electron Microscopy: SEM Carbon Coaters

Carbon coating for SEM samples is another option for making a conductive layer over the insulating surfaces. Deposition of carbon results in an amorphous layer on the sample which is also perfect for EDX analysis. 

TEM grids also need carbon layer deposition as a highly conductive layer with negligible imaging interference. Since different coating conditions like chamber pressure affect the resulting layer (Read more about it here). Vac Coat SEM carbon coaters are presented as DCR and DCT, working at low and high-vacuum respectively.

4- Hybrid SEM Coaters (SEM Sputter Coater + Carbon Coater)

Vac Coat Ltd. also offers SEM coaters that can deposit thin films through sputtering (SEM sputter coater) or coat carbon films (SEM carbon coater) in a single desktop coating system. The DSCR and DSCT, low and high-vacuum sputter coating/carbon coating systems, gather the merits of different SEM coating techniques in one machine.

Moreover, DSCR-300 and DSCT-300 are featured with a larger chamber, compared to DSCR and DSCT, which makes them suitable for long-lasting depositions. Furthermore, the DSCT-T sputter and carbon coater system also includes a thermal evaporation source to enable thin film deposition through the thermal evaporation procedure. In other words, DSCT-T is a compact triple coater.

2 thoughts on “SEM Coaters | Coating Techniques for SEM

    • Vac Coat

      The best sputter coating thickness and time for imaging bacteria in FESEM characterization strongly depends on the type of bacteria under study, the desired resolution, as well as the sputter coater model. To find the optimum caoting parameters, one can start with sputter coating a film with a thickness of 5-10 nm in about 30-60 seconds. A power of 20-30 mA and an Ar gas pressure of 0.2-0.5 mTorr are typically used for gold coating, whereas lower amounts work for platinum coating.

Leave a Reply

Your email address will not be published. Required fields are marked *