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.

Preparing Sulfur Terminated Copper

1. 2-3 * 10^-7 benzenethiol for 5 minutes.
2. Anneal with 10 W for 10 minutes.
3. Simultaneously anneal at 10 W and dose BT for 10 minutes.
4. You can either conclude here to dose Mo immediately, or you can wait until good pressure (3*10^-9 torr) is restored and anneal at 20 W for 20 min.

Aligning the Sputter Gun on the STM Chamber

1. Position the sample. Watch to make sure you do not hit the mass spec with the transfer arm. To avoid crashing, you will need to move the sample up and away from the mass spec. You should also angle the arm block 45 degrees from horizontal.  The final position should have the sample in from of the mass spec with the fine adjustments set such that the sample is as far down and out (towards the view port) as possible.
2. Close the mid valve (if you haven't already) and the turbo valve.
3. Make sure the ion pump is off by turning off HV1. The controller is on the bottom shelf of the cart and is leftmost. The ensures that you don't pump away the argon you are leaking in. This pump won't be turned back on until the sample is back in the STM chamber.
4. Leak in 1*10^-4 torr Argon (and then close). Switch off the ion gauge (using the back panel switch).
5. Turn on the sputter fun. Increase the filament current to 20 mA and the beam voltage to 3kV.
6. Alight the beam so that you can see a blue spot on the sample. Adjust x, y, and focus to get this to align with your sample as much as possible.
7. Open the valve to the turbo to pump away the Argon.
8. As good pressure is restored, turn off the sputter gun.
9. Let pump until good pressure is achieved and then you can start (probably) sputter/anneal cycles.

Clean the Gas Line

Quick Description: If you have a gas line that you have connected to your system (typically through a leak valve), you want to bake it and make sure it is clean before connecting with your UHV system. Often, you will be using a gas bottle (Ar, H, etc...) and this should be fairly clean but requires a few rounds of flushing to ensure that a pure material leaks into your chamber.

The Point: Pure gas.

Prerequisites: Set up the pump cart.

Notes: 

1. Bake the gas line
• Ensure that the two gas valves are open (one connects the gas bottle to ambient/pumping and the other to the chamber).
• Start the pump cart (see link above).
• Begin the bake. On the STM system, there are two bake plugs attached to the Argon line. On the old XPS, there is only one plug attached to the Argon line. The voltage is ~55V and the time span is about 2 hours (or overnight).
• Turn off baking and let cool for 30 min or so.
2. Flush cycles
• Close the gas valve to the pumping and open the gas bottle. This fills the line with gas.
• Then close the gas bottle and SLOWLY open the gas valve to the pumping. This flushed the gas line. Watch the pressure to make sure that you're not making the turbo struggle too much. It's generally a good idea to stay under 20 W, but this does vary for different pumps.
• Cycle through this about 5-6 times and you should be good.

Pump Cart

Quick Description: For small things that need to be pumped, our lab has a pump cart which includes a rough and turbo pump. Common applications include cleaning out a gas line, freeze/thaw cycles, pumping down a temporary chamber, and more.

The Point: A quick set of pumps to get the job done.

Notes: You may want to check that everything is plugged in and connected. If you are experienced, this should make intuitive sense to you. Otherwise, you can check with a more experienced labmate.

1. Open the turbo/chamber valve. Open the turbo/rough valve. This allows everything to stabilize to the same pressure.
2. Begin rough pump, wait a little bit so that again pressure can stabilize. It should be able to reach at least 10^-2 torr (and for a new, good pump 10^-4 torr), and ideally you can check this with a pirani gauge.
3. Turn on the turbo and wait for it to spin up to full speed and low power. If this does not happen, you may have a leak that needs to be addressed or a problem with your pumps (for example, if your turbo is back by an oil pump, this pump may have spewed a bit of oil).

Mass Spec Procedure

Inficon Mass Spec (from Cindy Merida):

1. To begin, open TWare32 program. Make sure power supply for actual mass spectrometer is connected, and the RS232 cable is connected as well.
2. When program is opened, Sensor1_P1TSP2 will appear green if everything is connected properly, if not, it will appear blue.
3. Click on the Sensor icon, and monitor, to monitor the full mass spectrum.
4. The defaults on the mass spectrum are set at MaxAMU of 70, which can be changed to 100.
5. Make sure both the Emission and Multiplier icons are clicked to have the mass spectrum running properly. If pressure is bad, turn off the multiplier.
6. Also, the range can be changed, to give bigger peaks, adjust to a smaller range and vice versa.
7. When finished running, click stop on the software, and close the window. Unplug or switch off the power supply