Nickel Target vs. Chromium Target in Magnetron Sputtering: A Complete Guide from Material Properties to Process Selection

In physical vapor deposition (PVD) magnetron sputtering, the choice of target material is a critical factor determining film performance, process stability, and production cost. Nickel (Ni) targets and chromium (Cr) targets are two of the most commonly used metal targets. However, they differ significantly in magnetic properties, sputtering behavior, film characteristics, and application scenarios. Many practitioners confuse their roles—some even mistakenly believe they can be used interchangeably.

This article provides a systematic, engineering-focused comparison between nickel and chromium targets in magnetron sputtering, along with clear selection recommendations.

1. The Most Critical Underlying Difference: Magnetic Properties

Although nickel and chromium are adjacent in the periodic table, they belong to different worlds in terms of magnetic behavior.

What does this mean in practice?

In a conventional DC magnetron sputtering system, a chromium target can be installed and used directly—ignition is easy and deposition rates are stable. A nickel target, due to its ferromagnetism, significantly weakens the horizontal magnetic field at the target surface, leading to:

Difficulty igniting the plasma or even inability to strike a discharge

Deposition rate dropping by more than 50%

Reduced target utilization

Poor process repeatability

Solutions: When using a nickel target, you typically need:

Ultra‑thin targets (thickness ≤3 mm)

Unbalanced magnetron sputtering sources

Strong magnetic targets (high‑coercivity magnets)

If your equipment uses a conventional planar target, a chromium target is the safer and more economical choice.

2. Comprehensive Comparison of Film Properties

Even when deposition is successful, the physical and chemical properties of nickel and chromium films are completely different.

Summary:

Chromium film: Hard, wear‑resistant, scratch‑resistant – suitable as a protective top layer.

Nickel film: Softer, tougher, excellent adhesion, alkali‑resistant – suitable as an interlayer or adhesion layer.

3. Typical Application Scenarios

Typical Applications of Nickel Targets

1. Adhesion/Underlayer in Multilayer Films
   Nickel has excellent adhesion to glass, ceramics, and polymers. In optical or electronic coatings, a very thin nickel layer (1–5 nm) is often deposited first, followed by functional layers such as gold, silver, or copper, to prevent delamination.
2. Corrosion‑Resistant Coatings
   In alkaline environments or marine atmospheres, nickel films perform better than chromium films. Some chemical valves and fasteners use nickel coatings for corrosion protection.
3. Electromagnetic Shielding
   Nickel has good magnetic permeability and electrical conductivity, making it suitable for electromagnetic shielding layers inside electronic devices.
4. Thin Film Resistors
   Pure nickel films can be used to prepare thin‑film resistors with moderate resistance values.

Typical Applications of Chromium Targets

1. Decorative and Wear‑Resistant Topcoats
   The silver‑white “chrome color” on faucets, bathroom fittings, automotive wheels, and eyeglass frames comes from chromium films. Their high hardness effectively resists everyday scratching.
2. Mold and Tool Coatings
   Chromium coatings on injection molds, stamping dies, and cutting tools significantly increase service life.
3. High‑Temperature Oxidation‑Resistant Coatings
   Chromium forms a dense chromium oxide (Cr₂O₃) layer at high temperatures, withstanding air environments up to ~700°C. It is used in some engine components.
4. Precision Thin‑Film Resistors
   Chromium films have moderate resistivity and a low temperature coefficient of resistance (TCR), suitable for high‑precision thin‑film resistors.

4. Selection Decision Table

Use the following table to make a quick decision based on your specific needs:

5. Common Questions and Misconceptions

Misconception 1: “Nickel and chromium targets can be freely substituted for each other.”

False. Their magnetic properties are fundamentally different. Replacing a chromium target with a nickel target may prevent plasma ignition. Film properties are also completely different, so they cannot be swapped arbitrarily.

Misconception 2: “Nickel films are not corrosion resistant.”

Fact: Nickel has excellent corrosion resistance in alkaline media and marine environments. It is only vulnerable to strong acids, especially oxidizing acids like concentrated nitric acid.

Misconception 3: “Chromium films are wear resistant under all conditions.”

Fact: Chromium films have high hardness and excellent resistance to abrasive wear and scratching. However, under high impact or counter‑body wear conditions, their low toughness can lead to brittle spalling.

Misconception 4: “Any magnetron sputtering system can deposit nickel.”

Fact: Sputtering ferromagnetic materials (nickel, iron, cobalt) with a conventional DC planar target is very difficult. Special high‑strength magnetic targets or thin‑target designs are required. Always verify equipment compatibility before purchasing a nickel target.

6. Process Operating Recommendations

Using a Chromium Target (Standard Process)

• Sputtering pressure: 0.3–0.8 Pa (Ar)
• Power density: 3–8 W/cm²
• Deposition rate: typically 10–30 nm/min (depending on equipment)
• Power supply: DC or medium frequency (MF) power supply recommended

Using a Nickel Target (Special Considerations)

• Target thickness: recommended ≤3 mm
• Magnet selection: use strong neodymium magnets or an unbalanced magnetic field structure
• Operating pressure: can be increased to 0.8–1.5 Pa to enhance ionization
• Ignition technique: ignite at high pressure (~2 Pa), then adjust to operating pressure
• Power supply: MF or pulsed DC is more stable than DC

7. Summary and One‑Sentence Recommendation

Final advice: If you have only a standard magnetron sputtering system without a high‑strength magnetic target configuration, chromium is the safer, day‑to‑day choice. Nickel targets are suitable for specialized production lines or R&D platforms capable of handling ferromagnetic materials.

Before full‑scale production, always perform trial runs with small samples to verify film properties and process stability—this is an essential step that no target selection can bypass.