What would cause sudden change in evaporation chamber behavior?

In summary, the speaker has been using an evaporation chamber in their lab to deposit substances onto a substrate. They typically use 175A to achieve a deposition rate of 1 angstrom/sec, but suddenly the deposition is not happening even when they increase the current to 200A. They have checked the electrodes and ruled out any physical or connection issues. They have also ruled out a faulty rate monitor. The speaker asks for help from anyone with experience in evaporation chambers. Another person suggests checking the vacuum for leaks or a bad pump. The speaker then reveals that the problem was actually due to the electrodes being too tight, and loosening them resulted in better performance.
  • #1
warfreak131
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Hello all,

I use an evaporation chamber at my lab every day. Basically, put some substance in the chamber, close it, bring it down to vacuum, and pump enough current through it to vaporize it where it deposits on a substrate.

I've been using 175A to create a deposition rate of about 1 angstrom/sec. All of a sudden, a few days ago, 175A doesn't generate any deposition. Even if I bring it up to 200A, there is almost no deposition taking place. I've checked the electrodes both physically and with a DMM to the best of my abilities, and there doesn't appear to be any loose connections or damage. I've also ruled out the possibility of the rate monitor being faulty.

Does anyone have experience with evaporation chambers who could help me out?
 
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  • #2
Have you checked your vacuum? There might be a leak or a bad pump.
 
  • #3
Did the evaporator once have a DC voltage bias applied to encourage the flow of positive ions away from the charge and towards the deposition surface?
 
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  • #4
I actually figured out the problem. The electrodes were too tight when securing the evaporator boat. I don't know why this happens, I'd figure better electrical contact would mean better performance, but no. I loosened them significantly to the point where I can still shimmy the boat around in the electrodes and I'm getting better performance than I ever have in the past.
 
  • #5


There are a few potential factors that could cause sudden changes in evaporation chamber behavior. One possibility could be contamination of the chamber or the electrodes, which could affect the conductivity and therefore the current needed for vaporization. Another possibility could be a malfunction or damage to the power supply or control system, which could impact the amount of current being delivered to the chamber. It is also possible that there is an issue with the substrate or the material being used for deposition, which could affect the vaporization process. I would recommend thoroughly cleaning and inspecting the chamber and electrodes, as well as checking all components of the power supply and control system. If the issue persists, it may be helpful to consult with other scientists who have experience with evaporation chambers or seek assistance from the manufacturer.
 

1. What factors can cause sudden changes in evaporation chamber behavior?

There are several factors that can cause sudden changes in evaporation chamber behavior, such as changes in temperature, pressure, humidity, or the composition of the substance being evaporated. Mechanical issues, such as clogs or leaks, can also lead to sudden changes in behavior.

2. How can changes in temperature affect evaporation chamber behavior?

Temperature plays a critical role in the process of evaporation. Higher temperatures can increase the rate of evaporation, while lower temperatures can decrease it. Sudden changes in temperature can also cause changes in the vapor pressure of the substance being evaporated, which can affect the behavior of the chamber.

3. Can changes in pressure impact evaporation chamber behavior?

Yes, changes in pressure can impact the behavior of an evaporation chamber. If the pressure inside the chamber increases, it can lead to faster evaporation. Conversely, a decrease in pressure can cause the rate of evaporation to slow down. Sudden changes in pressure can also affect the boiling point of the substance being evaporated, which can impact the behavior of the chamber.

4. What role does humidity play in evaporation chamber behavior?

Humidity refers to the amount of water vapor present in the air. This can have a significant impact on evaporation, as higher humidity can slow down the rate of evaporation. Sudden changes in humidity can affect the vapor pressure of the substance being evaporated, which can lead to changes in the behavior of the chamber.

5. How can I troubleshoot sudden changes in evaporation chamber behavior?

If you are experiencing sudden changes in evaporation chamber behavior, there are a few steps you can take to troubleshoot the issue. First, check for any mechanical issues, such as clogs or leaks, that may be affecting the chamber. Next, examine the temperature, pressure, and humidity levels to see if there have been any sudden changes. It can also be helpful to review the composition of the substance being evaporated to ensure it is consistent. If the issue persists, consult a professional for further assistance.

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