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Warming up the Substrate Heater from VCT

Written by SDS from email 3/29/2017, added to Wiki by NTS.

Ideally, the Substrate Heater is never left cold during a campaign, except in the following case: when it is cooled down on purpose during a growth, under the watchful eye of the grower, and then re-heated as necessary

However, someone may forget to re-heat the Substrate after a long cold step, such as a long As cap. Or someone may forget to turn the Substrate Eurotherm back to manual after a Block Transfer (when left at 0 power for transfer).

Procedure

Steps taken to warm up the substrate heater from VCT (very cold temperatures):

• Throughout: Monitor the pressure gauges in the MBE chamber. A slight rise in pressure is to be expected due to condensed material desorbing off the CAR as it warms up. This should be less than an order of magnitude or even a factor of 3. Significant changes in pressure should be reported and the situation escalated as appropriate.

1. Check that there is water flow. i.e. ice has not formed in the lines, particularly inside the CAR. This is done by getting up on a ladder and checking the flow controller for the CAR. The indicator should be at the marked level in the water column.

   1. If, after step 1, there is no water flow and ice is suspected in the CAR lines, detach the CAR water supply lines and hook up a light N2 flow into the line.

   2. Check for gas flow out of the other port. If there is a little, keep blowing to melt the ice blockage.

   3. If there is no flow, do the same.

2. After making sure there is water flow, slowly (maybe 0.2 to 0.5 percent per minute) raise the filament output power in manual. There probably will not be much if any temperature rise until about 2 percent.

3. Once warmed up to about 3% and maybe 20ish degrees C, set the ramp rate in Amber to 2-5 degrees per minute, set the target temperature to 200, and switch over to Auto.

4. Once warmed to 200 C, set the ramp rate back to the default value of 60 degrees per minute.