Dosing Molybdenum for MoS2

1. Prepare the Evaporator
• Open the turbo corner valve and pump the evaporator with the pump cart. You will have two turbos in series.
• Overnight, bake the evaporator at 70-80 V to reach >100 C. Be careful with the baking tape and make sure to wrap the evaporator with fiber glass.
• The next morning, stop the bake, set up the water cooling lines, and degas the filament for the evaporator. You should go to 5.6 A and 5 V for 15 minutes. At the same time, make sure to watch the temperature and pressure. You do not want to exceed 150 C or overpower the turbos.
2. Dummy Dose
• Insert the thickness monitor so that it is in front of the evaporator. Twist the knob until sleeve reaches the label which marks the correct position. You can double check the location is correct by opening the evaporator valve and looking through the view port on the other side.
• Set the thickness monitor controller to have a density setting at 10.2 and a Z-factor setting at .25. Watch the monitor a bit to check that it is stable.
• Apply the 3kV high voltage power supply. This is an external unit which is home built and directly connected to the evaporator source rod.
• Increase the filament current to around 5 A such that the dosing rate is ~2 angstroms/min. The dosing rate is related to V, I, high voltage (HV), and the Mo rod position, so you can fiddle with all of these.
3. Real Dose
• Quickly take the sample out of the STM chamber and align it visually (using the view port) so that the sample is in front of the evaporator.
• Retracted the thickness monitor.
• Introduce BT at ~3*10^-9 torr (this will not be a very stable value) and at the same time, anneal the sample at 10 W.
• Open the evaporator valve to begin dosing. You will dose for about 1 hour, while keeping an eye on temperature and maintaining dosing with adjustments to rod position and current. Although flux and emission current are imperfect measurements, you would like for them to be somewhat steady values.
• Stop dosing the Mo by closing the evaporator valve. Close the BT leak valve. 
• Anneal the sample at ~20 W. While waiting for good pressure to restore, turn off the evaporator. 
• Let the sample cool before putting back in the STM.