Graphite E Beam Crucibles

Overview of High-Purity Graphite Crucibles for E-Beam Evaporation

High-purity graphite crucibles are an integral component of e-beam evaporation systems, offering superior performance and longevity. MetalsTek provides graphite crucibles designed to enhance deposition efficiency and ensure consistent results across multiple evaporation cycles.

Benefits of High-Purity Graphite Crucibles

Thermal Efficiency:
Graphite crucibles act as an effective thermal barrier between the melt and the water-cooled hearth.
- Enhanced Deposition Rates: Deposition rates can increase by up to 400% at the same power level compared to a bare hearth.
- Reduced Power Requirements: For the same deposition rate, power consumption can be reduced to 25% of the bare hearth’s power.
Purity Standards:
Each crucible undergoes rigorous purification to meet exacting purity levels:
- Major contaminants like Fe, Si, Al, and Mg are reduced to less than 5 ppm.
- No detectable levels of 16 other common metals, including Na, K, and Pb, ensuring clean evaporation.
Durability:
Graphite crucibles are built to withstand as many as 400 evaporation cycles, making them a cost-effective choice for high-volume operations.
Material Compatibility:
These crucibles are compatible with a wide range of materials, including:
- Metals: Cr, Cu, In, Mg, Mo, Pt, Ta, Ti, Zn
- Alloys: Al-Ge, Al-Si
- Compounds: CdS, Na₃AlF₆, SiO₂, Y₂O₃
Customization Options:
- Taller crucibles hold more material but are unsuitable for multi-hearth furnaces not designed for their dimensions.
- Model EVCEB-2 includes a top lip and has the same dimensions as EVCEB-4.

Important Note: These ultra-fine-grain, high-density graphite crucibles are distinct from “glassy” or vitreous carbon, which often cracks after just one use.

Common Causes of Crucible Breakage

To maximize the lifespan of your graphite crucible, it is crucial to avoid these common issues:

1. Incorrect Ramp/Soak Settings

E-beam evaporation recipes rely on carefully managed ramp/soak power levels to gradually heat materials to the desired deposition temperature:

Power Control Transition: During deposition, control shifts from ramp/soak settings to a PID loop. This loop manages the e-gun power supply and quartz crystal controller to maintain the deposition rate.
- Oscillating Power Levels: If ramp2/soak2 levels are far from the required deposition power (e.g., 1 Ångström/sec), the PID loop compensates erratically, causing power fluctuations between +90% and 0%. These wild swings rapidly liquefy and condense the material, stressing the crucible and leading to cracks.
- Solution: Ensure ramp2/soak2 levels are close to the deposition power level, reducing PID adjustments and preventing rapid phase changes.

2. Abrupt Power Shutdowns

Handling the power supply improperly after deposition can also damage the crucible:

Rapid Cooling Stress: Turning off the power abruptly or using a short ramp-down period causes the melt to solidify quickly. This rapid solidification induces mechanical stress on the crucible, potentially causing breakage.
- Preventive Measure: Implement a gradual ramp-down process to allow for even cooling, reducing stress on the crucible liner.