Common Types of Chemical Deposition Techniques used in UK Research Organisations

Chemical deposition techniques are essential in numerous industries, including electronics, materials science, and nanotechnology. Below, we will list the most commonly used chemical deposition techniques in today's industrial landscape, each with its unique process and applications.

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1. Chemical Vapor Deposition (CVD)

Chemical Vapor Deposition (CVD) is a widely utilised technique, especially in semiconductor manufacturing. In CVD, a gaseous precursor chemically reacts on a heated substrate, causing the material to deposit as a solid film. This method can be performed under varying temperature and pressure conditions, depending on the material being deposited.

• Applications: Semiconductor fabrication, tool coatings, solar cell production, and gas separation membranes.
• Variants:
• Low Pressure CVD (LPCVD): Used for depositing high-quality films at lower pressures.
• Plasma-Enhanced CVD (PECVD): Uses plasma to accelerate the deposition process, enabling deposition at lower temperatures.
• Metal-Organic CVD (MOCVD): Ideal for depositing compound semiconductors such as gallium nitride (GaN).

2. Physical Vapor Deposition (PVD)

Physical Vapor Deposition (PVD) involves vaporising a solid material in a vacuum environment and allowing the vapor to condense onto a substrate, forming a thin film. Unlike CVD, PVD generally does not involve chemical reactions to form the deposited material.

• Applications: Tool coatings, optical coatings, microelectronics, and decorative finishes.
• Variants:
• Evaporation Deposition: A solid material is heated in a vacuum, turning it into vapor, which then condenses onto the substrate.
• Sputtering: Ions bombard a target material, causing atoms to be ejected and deposit onto the substrate.

3. Electrochemical Deposition (Electroplating)

Electrochemical deposition involves reducing metal cations from a solution onto a substrate by applying an electric current. The metal is deposited as a thin film, and its thickness can be controlled by adjusting parameters such as current density and bath composition.

• Applications: Plating metals such as gold, silver, copper, and chromium onto various materials for electrical conductivity, corrosion resistance, and aesthetic purposes.
• Variants:
• Electroplating: A thin metal layer is deposited onto a substrate via electrochemical processes.
• Electroless Plating: Similar to electroplating but occurs without the use of an external current, often applied to non-conductive substrates.

4. Sol-Gel Deposition

Sol-gel deposition is a method used to create thin films from a precursor sol, which is a colloidal suspension of fine particles in a solvent. The sol is applied to a substrate, and through chemical reactions such as hydrolysis and condensation, it forms a gel. The gel is then dried and heated to produce a solid film.

• Applications: Optical coatings, protective coatings, ceramic thin films, and sensor technologies.
• Advantages: Low processing temperatures and the ability to control porosity and composition of the films.
• Variants:
• Dip Coating: The substrate is dipped into the sol and withdrawn to form a uniform film.
• Spin Coating: A small amount of sol is applied to the substrate, and spinning spreads the liquid into a thin, uniform film.

5. Atomic Layer Deposition (ALD)

Atomic Layer Deposition (ALD) is a precise method for creating uniform films one atomic layer at a time. By relying on self-limiting chemical reactions between gaseous precursors, ALD offers extremely fine control over the thickness and uniformity of the films, making it ideal for applications that require atomic-level precision.

• Applications: Semiconductor manufacturing, high-k dielectric films, catalysis, and conformal coatings on nanostructures.
• Advantages: Atomic-level thickness control, excellent uniformity, and conformity to complex surface geometries.
• Variants:
• Plasma-Enhanced ALD (PEALD): Uses plasma to activate the precursor, allowing deposition at lower temperatures.

6. Spray Pyrolysis

Spray pyrolysis involves atomising a precursor solution into droplets and then heating them in a furnace or oven. The precursor decomposes and forms a thin film as it condenses onto the substrate.

• Applications: Coatings for solar cells, gas sensors, and optoelectronics.
• Advantages: High deposition rates, low cost, and scalability for large-area coatings.

7. Molecular Beam Epitaxy (MBE)

Molecular Beam Epitaxy (MBE) is a high-precision method for depositing thin films by directing a molecular or atomic beam onto a heated substrate under ultra-high vacuum conditions. The material is deposited one atomic layer at a time, enabling the creation of smooth, controlled films.

• Applications: Semiconductor device fabrication, quantum dot production, and advanced research in nanotechnology.
• Advantages: Atomic-scale control of film thickness and composition.

8. Chemical Bath Deposition (CBD)

Chemical Bath Deposition (CBD) involves immersing a substrate in a solution containing metal salts and other chemicals. A chemical reaction occurs in the bath, resulting in the reduction of metal ions and their deposition onto the substrate as a thin film.

• Applications: Deposition of cadmium telluride for solar cells, zinc oxide for transparent conductive layers, and copper for photovoltaic devices.
• Advantages: Low temperature, simple equipment, and cost-effective for large-area coatings.

9. Laser Ablation Deposition

Laser Ablation Deposition uses high-intensity laser beams to vaporise a target material, and the vapor then condenses onto a substrate to form a thin film. This method is often used in industries requiring the deposition of complex materials.

• Applications: Deposition of superconducting films, thin films for microelectronics, and optical coatings.
• Advantages: Precise control over film composition and the ability to deposit complex materials.

Comparison Table: Common Types of Chemical Deposition Techniques

For more information, please visit Stanford Advanced Materials (SAM).

Conclusion

Chemical deposition techniques are indispensable for producing thin films and coatings in various applications, from semiconductor manufacturing to energy production. Each method offers unique advantages tailored to specific materials and applications. Whether it is the precision of ALD, the speed of spray pyrolysis, or the uniformity of CVD, understanding the characteristics and variants of these deposition techniques is essential for selecting the best approach to meet industrial needs.

Reference:

[1] Ali Akbar Firoozi, Ali Asghar Firoozi, Taoufik Saidani, Advancing durability in the energy sector: Novel high-temperature resistant coatings and their challenges, Ain Shams Engineering Journal, Volume 16, Issue 7.

[2] Ngqoloda, Siphelo & Ngwenya, Thelma & Raphulu, Mpfunzeni. (2025). Recent Advances on the Deposition of Thin Film Solar Cells. 10.5772/intechopen.1008691.