Dry Deposition™ vs. wet dispersion

Carbon nanotubes (CNTs) have emerged as a key ingredient for highly engineered solutions. Yet, conventional methods for carbon nanotube production often involve harsh techniques like wet dispersion and ultrasonication, which can compromise their exceptional properties such as high transmittance, uniformity, and mechanical strength. Ultrasonication and surfactants used in conventional wet dispersion cut and damage CNTs, resulting in significantly reduced tensile strength, lower electrical conductivity, bundling, and decreased electrochemical sensitivity.

Canatu’s patented Dry Deposition™ technology surpasses conventional wet methods, setting a new standard for CNT production. This approach eliminates the need for harsh steps involved in traditional wet dispersion, preserving the exceptional properties of CNTs.

Canatu’s Dry Deposition™ method produces incredibly long and pristine CNTs, offering significant advantages over traditional wet dispersion. While wet dispersion requires multiple complex steps, Dry Deposition™ offers a simpler, faster, and more cost-effective process, yielding high-purity, strong CNTs.

Dry Deposition™ outperforms wet dispersion by simplifying the process, yielding longer and cleaner CNTs, and creating highly uniform CNT networks.

Dry Deposition™ of carbon nanotubes ensures that your products perform precisely as intended. Our method yields longer, cleaner, and nearly defect-free CNTs with superior uniformity, transmittance, conductivity, electrochemical sensitivity, and tensile strength. This is because the electrical conductivity and tensile strength of the tubes increase with their length and purity, thereby enhancing performance across various applications.

For example, semiconductor fabricators can leverage Canatu’s Dry Deposition™ method to produce CNT membranes with exceptional uniformity and high EUV light transmittance, benefiting various applications including EUV pellicles, debris filters, and optical filters. This can lead to a 15% increase in performance (measured in wafers per hour) for EUV pellicle application and substantial cost savings by reducing the need for expensive lithography tools.

Wet dispersion cuts and damages CNTs

Traditional CVD synthesis and the liquid dispersion of CNTs is a complex process with several steps. It starts with CNT powder, which often comes bundled with impurities and has low crystallinity. Ultrasonication cuts the CNTs into pieces. As a result the aspect ratio of CNTs decreases, degrading their properties.

CVD synthesis
First, a catalyst-coated ceramic plate is placed inside the reactor, and carbon-containing gas is introduced. Carbon atoms from the feedstock react with the catalyst, leading to the growth of carbon nanotubes. The CNTs grow vertically from the catalyst particles, forming a forest-like structure.

CNT powder collection
After synthesis, CNTs are collected from the ceramic plate. CNT powder usually comes bundled with impurities and has low crystallinity.

Wet dispersion and ultrasonication
The collected CNT powder is dispersed into the liquid and blended with water using ultrasonication. While this step effectively mixes CNTs with the water, it also results in cutting the CNTs. As a result, the aspect ratio of CNTs decrease, degrading their properties.

Adding surfactants
Surfactants are added to improve the dispersity of CNTs. CNT bundles improve mechanical strength but degrade optical performance causing scattering.

Purification
Next, using thermal or chemical treatment, CNT undergoes purification to remove metallic catalyst residues. Residual metals are particularly undesirable in the EUV applications as they can absorb and scatter the EUV light.

Centrifugation
CNTs are centrifugated and sorted based on their structural properties, such as wall count, bundle size, or electrical conductivity.

Filtration
The sorted CNTs are poured into the water, and the CNTs are filtered onto the filter paper.

Water transfer printing
The CNT network is detached from the filter on the liquid’s surface, making CNT film floating on the surface of the liquid. Then, a frame is pulled through the liquid, attaching the CNT film to create a free-standing membrane.

Washing
Residual surfactants are washed away.

Coating
Coatings can be applied to the CNT membrane to improve its stability in the EUV environment.

Dry Deposition™ simplifies the process

Canatu’s patented Dry Deposition™ method outperforms wet dispersion by simplifying the process and yielding cleaner, longer carbon nanotubes and highly uniform CNT networks, thereby enhancing the performance of end applications. Canatu’s approach eliminates multiple complex process steps that can compromise the quality of CNTs.

FC-CVD synthesis
Canatu synthesizes CNTs using the floating catalyst chemical vapor deposition (FC-CVD) process. Compared to other methods, FC-CVD stands out as a low-cost, highly controllable, and scalable process for creating cutting-edge CNTs for industry-transforming products.

During FC-CVD, CNT growth is initiated by introducing carbon gases into the reactor. The furnace is then heated to vaporize and decompose the carbon gases, leading to catalyst particles forming at the top of the reactor. These particles float down the reactor with a carrier gas toward the collection filter. As they drift down the reactor, CNTs start to grow on the catalyst particles.

Dry Deposition™
The CNTs are dry deposited onto the collection filter under atmospheric conditions.

Transfer
Subsequently, CNTs are transferred from the collection filter onto either a plastic substrate, creating a conductive film, or a frame, creating a membrane.

Post-processing
The membrane goes through post-treatment to further improve its properties.