Sputter Coating of Glass Fibers for SEM

Glass fibers are materials composed of many very fine strands of glass, usually with diameters ranging from 3 μm to 20 μm. These fibers are combined with polymers to create reinforced plastics.

Glass-reinforced polymers, also known as fiber-reinforced plastics, are created from plastic that is strengthened by fine glass fibers. Like other composite materials, the two components work together to compensate for each other's weaknesses.

Plastic resins perform well under compressive forces but have relatively low tensile strength, while glass fibers exhibit high tensile strength but do not handle compression as well. Combining the two results in glass-reinforced polymer, a material that effectively withstands both compressive and tensile stresses.

Image Credit: Luxor

Image Credit: Luxor

Depending on the intended use, glass fibers can be manufactured from various types of glass. Common applications for regular glass fiber include mats and textiles for thermal and electrical insulation, soundproofing, high-strength fabrics, and heat- and corrosion-resistant materials.

They are also employed to reinforce a variety of products, including tent poles, translucent roofing, vehicle bodies, boat hulls, and paper honeycomb structures.

Why is SEM Imaging Used for Glass Fibers?

SEM (scanning electron microscopy) imaging serves as an effective method for examining the uniformity and distribution of glass fibers within a polymer matrix. This technique can also detect defects such as inadequate adhesion of fibers to the polymer matrix, indicated by clean fibers.

Combining chemical microanalysis methods (EDS) with scanning electron microscopy provides additional insights into the composition of the fibers.

As aforementioned, glass fibers and polymers are excellent thermal and electrical insulators. Therefore, when they are scanned by an electron beam in a microscope, sample charging may take place.

Image Credit: Luxor

What is Sample Charging?

SEM images are formed by directing an electron beam across a sample, which essentially adds electrons to the material. Sample charging occurs when the materials lack sufficient electrical conductivity, which stops electrons from flowing from the sample surface to the sample holder.

This can cause issues such as drift, blurring, and reduced contrast, resulting in distorted, unclear images.

To alleviate sample charging, a very thin conductive layer of metal, such as gold (Au) or platinum (Pt), can be applied to the specimen's surface, in a method known as metal or sputter coating.

This allows electrons to move freely from the sample surface to the sample holder, thus preventing charging. Sputter coating also results in improved secondary electron emission, decreased beam penetration with enhanced edge resolution, and better protection for samples sensitive to electron beams.

LUXOR metal coaters are designed to automatically apply a uniform, thin metal layer to SEM samples, effectively counteracting any charging effects and improving image resolution in electron microscopy.

Image Credit: Luxor

Uncoated glass fiber at 2000 x magnification. Image Credit: Luxor

Glass fiber coated in a 10 nm gold layer at 2000 x magnification. Image Credit: Luxor

Why Choose LUXOR?

A² Technology: Precision Coating for High-Resolution Imaging

LUXOR’s A² technology generates a highly stable and precisely controlled plasma, enabling the deposition of thin, uniform coatings. The process starts by evacuating the chamber to create a vacuum, after which a proces gas or air is injected and a high voltage is applied to ionize the gas, initiating the plasma and the coating curent.

To maintain process stability, the coating current is continuously regulated through the controlled high-speed injection of small amounts of process gas into the chamber. This dynamic adjustment ensures that the target current is reached quickly and maintained throughout the coating cycle.

What sets LUXOR metal coaters apart from other commercially available systems is their distinctive approach to process monitoring and control, which provides exceptional precision and reproducibility.

For SEM operators, this translates into acquiring more consistent, uniform metal coatings that significantly improve image quality, enhancing both resolution and contrast.

Moreover, the coating process is fully automated, eliminating manual involvement and ensuring a seamless, hassle-free experience.

Image Credit: Luxor

LUXOR follows a "form follows function" design philosophy, which is reflected in the distinctive architecture of its mcoaters. Unlike conventional systems, the samples and are suspended upside down within the coating chamber, while the target is at the bottom. Although this configuration may initially seem unconventional, it offers several significant practical advantages.

• Safety first: The sputter device has all the high voltage and current lines safely stored within the instrument housing, decreasing the risk of electric shock. This safety function enables the machine to operate with total peace of mind.
• Effortless sample handling: The upside-down design allows for easy access to the lid, which also serves as a loading station for samples. This enables the quick application or removal of samples without the use of special tongs or tweezers. This simplicity not only improves usability but also increases productivity by expediting the process.
• Clean coating process: The clean coating procedure removes loose particles, providing maximum protection for the expensive SEM column. This results in more consistent and reliable outcomes.
• 3D coating: 3D coating improves the coating quality by removing the larger particles towards the pump rather then towards the suspended samples by gravity. LUXOR’s A² technology eliminates the need for a rotary or planetary table, making it easier to coat three-dimensional, complex and porous samples.

Fully Automated

The coating process is fully automated. Once the samples have been loaded, simply select the appropriate coating thickness and press the Start button. This user-friendly approach significantly reduces the likelihood of human error, and new operators and lab professionals can learn to use the device after only a few minutes of basic instruction.

This information has been sourced, reviewed and adapted from materials provided by Luxor.

For more information on this source, please visit Luxor.