Standard Operating Procedure LakeShore PSEUL Laboratory

Lizbeth Rostro, Holly Chan, Martha Hay February 2014

Description of Process The LakeShore in conjunction with a Keithley 2400 allows for current-voltage testing under vacuum with varying temperature (100 °C – 350 °C). Personal Protective Equipment EYE PROTECTION: Safety glasses PROTECTIVE CLOTHING: Nitrile gloves LakeShore Procedure Sample Loading: 1. Make sure the vacuum valve is closed Figure A3 (clockwise). Turn vacuum pump on. (switch is in the back of the pump Figure A1) 2. Refill the LakeShore

a. Turn nitrogen valve on, located to the right of the LakeShore. b. Loosen screws on top cover. (Figure A2) c. Open the valve in front of the LakeShore. (Figure A3)

d. After the chamber is refilled, close the nitrogen valve on LakeShore and close the valve on the nitrogen tank.

3. Remove inside cover (ALWAYS use nitrile gloves when maneuvering inside the LakeShore) by loosening the screws. Be careful to not remove the screws completely. 4. Place sample(s) on gold plate carefully. Note that the probe tips would not be able to reach the full dimensions of the gold plate. 5. Screw inside cover on. 6. Screw outside cover on. 7. Check to make sure that the valve to refill is closed and SLOWLY open the vacuum valve (Figure A3). When opening the valve, open at a rate where the gauge reads OL, initially you will hear a high pitch noise, do NOT open the valve further. Once the pressure falls below 1E-3 torr, open the valve slightly again until the gauge reads OL. Repeat this process until the valve is completely open. Room Temperature Device Testing: 1. Turn Keithley on, by pressing the POWER button (Figure A7). 2. Log into computer: User name: PSEUL and Password: pseul. This is required if you are running a LabView program. 3. Open the desired program. 4. Move the tips over the appropriate metal contact. Use the knobs on the appropriate arm to adjust its location. Do NOT under any circumstance force the knobs, if it becomes difficult to move you are forcing the knob beyond its capability. a. Three knobs are on the probe arms: (Figure A4)

i. Moves in and out of the chamber ii. Moves the probe arm left to right iii. Moves the probe arm up and down

b. The location of the tips can be monitored by looking into the chamber through the watch glass or with the viewing camera.

i. Turn the camera on by turning the knob on the Schott controller (Figure A4). There will be light visible to the eye coming from the camera. ii. Turn on the computer screen by pressing the Power button (Figure A5). iii. Adjust the location of the camera by turning the knob at the top of the camera stand (Figure A6).

5. Once the tips are over the devices, use the “up” knob to lower the tip. The direction to turn up and down is labeled on the arms. Be very careful to not jam the tip into the device (Figure A4).

a. Focus the camera on the surface of the substrate during this step, as the tip is lowered towards the substrate it will become focused. b. Utilize the shadow to determine how far away you are from the surface. c. Pay careful attention to the probe tip, as it should deflect slightly upon contact - stop the tip adjustment at this point

6. Connect the probe tips to the Keithley using the banana plugs. 7. Run the appropriate LabView code. 8. After all tests are finished; follow the steps 1-9 in the sample loading procedure to remove the sample.

a. Make sure to pull vacuum on the chamber after the sample has been removed.

9. Close vacuum valve and turn off pump. 10. Turn off camera light, camera screen, Keithley, and LabView code. 11. Fill out the equipment log and make notes about any abnormal behavior. Temperature Device Testing: 1. At least one day prior to device testing fill liquid nitrogen dewar, located in PSEUL next to the LakeShore.

a. Fill out Form 100 and tape it to the tank. b. Take the dewar down to the liquid nitrogen filling station in the Physics building.

2. Follow the sample loading procedure. 3. Insert liquid nitrogen attachment on top port of the dewar. 4. Open the valve push the attachment in, until it no longer goes in. 5. Slide the liquid nitrogen attachment into the port on the LakeShore. 6. Open the valve on the liquid nitrogen attachment located near the dewar. 7. Turn on LakeShore Temperature controller. The switch is located behind the controller. 8. Set the controller to the desired temperature. 9. Once the system has reached the desired temperature, wait 30 minutes. 10. Follow the Room Temperature Device Testing procedure.

11. Once all current-voltage data is collected, close the valve on the liquid nitrogen attachment near the dewar. 12. Pull the liquid nitrogen attachment out of the LakeShore. 13. Pull the liquid nitrogen attachment out of the dewar and close the valve. Be careful, as the attachment will be very cold.

APPENDIX

Figure A1. Vacuum pump for the LakeShore.

Pressure Gauge

Power Switch

Figure A2. Compressed nitrogen tank located to the right of the LakeShore.

Nitrogen Line Valve

Nitrogen Tank Gauge

Figure A3. Probe arm, outside cover, nitrogen refill valve, and vacuum valve

location.

Nitrogen Refill Valve

Probe Arm 1

Probe Arm 2

Probe Arm 3

Probe Arm 4

Outside Cover

Vacuum Valve

Liquid Nitrogen Port

Figure A4. Location of LakeShore probe arm controllers.

Up/Down Controller

In/Out Controller

Left/Right Controller

In/Out Controller

Figure A4. Camera light intensity controller.

Figure A5. Camera screen, located to the right of the LakeShore.

Light Intensity Controller

Power Button

Figure A6. Camera location controller and focus knob.

Camera Location

Controller

Camera Focus

Knob

Figure A7. Keithley 2400 used for LakeShore current-voltage testing.

Power Button

Banana Plug

Ports

Figure A8. Liquid nitrogen tank for temperature experiments.

Pressure Gauge

Liquid Nitrogen Port