Hi,
I am trying to deposit permalloy using E-beam. The KJLC website recommends use of their fabmate crucible with permalloy pellets but these crucible liners are limited to one time use as the crucible cracks. They also mention direct from hearth deposition but the system I am using is shared and we cannot risk contamination. The other option mentioned is use of copper crucible with permalloy machined into the form of a starter source. The last solution seems ideal but I am left wondering if this is really a solution wouldn't there be a high possibility of copper evaporating as well because copper has a much lower melting point than permalloy. If anyone has any insight I would love to know your suggestions.
Thank you.
The thing is that you have local heating, in which the evaporation temperature is reached at one point, and the rest of the material remains relatively cold. Melting and, especially, evaporation of copper during local heating requires much more energy than evaporation of permalloy. This is explained by the fact that the thermal conductivity of copper (398 W/mK) is 11 times higher than the thermal conductivity of permalloy (34.6 W/mK), which means that heat removal from the heating point in copper occurs 11 times more intense. The lower melting and boiling points of copper are not significant in this case.
Dear friend Alex Paul
For E-beam evaporation of permalloy, the choice of crucible liner is crucial to ensure successful deposition without contamination. While KJLC recommends their fabmate crucible with permalloy pellets, the limitation of one-time use due to cracking poses a challenge.
Regarding the option of using a copper crucible with machined permalloy starter source, it's a viable solution to avoid contamination from shared systems. However, your concern about copper evaporating due to its lower melting point than permalloy is valid.
To address this concern, consider the following factors:
1. **Temperature Control**: Ensure precise control of the evaporation temperature to prevent excessive vaporization of copper.
2. **Optimized Deposition Parameters**: Fine-tune deposition parameters such as beam intensity and deposition rate to minimize copper evaporation while effectively depositing permalloy.
3. **Thermal Insulation**: Implement thermal insulation measures around the crucible to minimize heat transfer to the copper and reduce its vaporization.
4. **Precautionary Measures**: Monitor deposition closely and implement periodic checks to detect any signs of copper contamination or excessive evaporation.
In summary, while using a copper crucible with machined permalloy may pose risks of copper evaporation, careful control of parameters and implementation of preventive measures can mitigate these risks effectively. Experimentation and optimization may be necessary to achieve the desired deposition quality without compromising on material integrity.
First of all, optimise the melting temperature of your material. Slowly increase the power, with controlled amps.
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