Operation of the Edwards Auto 306 Cryo Evaporator
The method described below is for oxygen plasma cleaning and then an ambient temperature deposition of Chromium followed by gold on a rotating substrate. For other methods please contact the SAF prior to attempting the experiment.
The vacuum controller should display Fine Pumping - Chamb 2 x 10-7MB. If it displays Sealed - Chamb 1 x 103MB start at 2 by loading your sample.
1. To vent the chamber, open the nitrogen gas cylinder (set the regulator to 0.5 bar) and line to the evaporator and then press seal wait 10 seconds and then press vent on the pumping system controller. The display will show CHAMBER VENT. The chamber will take about two minutes to vent. Wait until the hissing stops and the pressure is reading 1 x 103 mbar and then attempt to open the chamber by gently lifting the bell jar. If the bell jar is hard to lift, it has not finished venting. Once you have removed the bell jar and placed it inverted on the cork ring, stop the venting process by pressing "seal" on the pumping system controller and then close the nitrogen cylinder.
2. Securely attach your (cleaned and dried) substrates onto the sample holder using the bolts and washers, remember that this holder will be mounted upside down. Bolt the holder onto the bottom of the driven bearing using the bolt provided. Turn the knob fully clockwise on the rotary stage controller and switch it on (using the switch the neon should light). The substrate holder will begin rotating; the speed and direction can be varied with the knob. Check there is sufficient gold in the boat if not contact the SAF.
3. To pump the system down, replace the bell jar and implosion guard. Press cycle on the pumping system controller. The chamber must pump down to below 1 x 10-4 mbar before the plasma processing can be started (Ideally you should wait until it reaches below 5 x 10-7 mbar for the best results).
4. To plasma clean the substrates (if you don’t wish to do this go to step 5) open the oxygen gas cylinder (set the regulator to 0.5 bar) and line to the evaporator. Close the needle valve on the front of the evaporator, loosen the swagelock connector on the evaporator so that any air is purged from the oxygen line then retighten it. Press process on the vacuum controller and the display should read PLASMA PROCESS CHAMB = 0.0 x 10-4 mbar, open the swagelock valve on the oxygen inlet and then open the needle valve about 1/4 of a turn until the pressure reads about 1.4 x 10-1 mbar. Select HT with the right-hand selector switch, then increase the current (using the graduated current control knob) until a blue grey discharge can be seen, vary the current (usually keeping this below 4) and pressure so that this fills the volume below the sample. Time the plasma process for the length of time you want to process the sample for then turn the current down to 0 and switch the right-hand selector switch back to 0. Close the swagelock valve, open the needle valve a couple of turns then press cycle on the vacuum controller and close the oxygen cylinder.
5. To evaporate Chromium (if you don’t wish to do this go to step 6) first check the thickness monitor controller (FTM5) is correctly configured (by cycling through the parameters using the data button): Layer = 1, Density = 7.2 and z-value = 28.9 if these values are not correct change them using the inc/dec buttons. Ensure the pressure is below 5 x 10-7 mbar, if it is not wait ideally until it is at 2 x 10-7 mbar. Open the shutter on the thickness monitor controller (FTM5), select A on the LT selector switch and select LT on the right-hand selector switch. Then slowly increase the current (using the graduated current control knob) while watching the reflection of the Chromium rod in the mirror, it should start to glow initially at the ends, keep the current constant until the glow extends along its length. Limit the current so that the pressure never exceeds 5 x 10-6 mbar (and ideally stays below 1 x 10-6 mbar). Continue to gradually increase the current (so that the rod is glowing evenly) until the thickness monitor displays a rate of 0.1 or 0.2 nm s-1 then wait until the layer is almost (<0.3 nm away) the desired thickness (5nm is recommended for enabling gold to adhere to silica) and turn the current down to zero. Switch the right-hand selector switch back to 0 and close the shutter on the thickness monitor controller (FTM5). Wait for about 5mins for the system to cool down and the pressure to return to 2 x 10-7 mbar.
6. To evaporate Gold first check the thickness monitor controller (FTM5) is correctly configured (by cycling through the parameters using the data button): Layer = 2, Density = 19.3 and z-value = 23.2 if these values are not correct change them using the inc/dec buttons. Ensure the pressure is below 5 x 10-7 mbar, if it is not wait ideally until it is at 2 x 10-7 mbar. Open the shutter on the thickness monitor controller (FTM5), select B on the LT selector switch and select LT on the right-hand selector switch. Then slowly increase the current (using the graduated current control knob) while watching the reflection of the boat containing the gold in the mirror, it should start to glow initially at the ends, keep the current constant until the boat is glowing evenly. Continue to gradually increase the current (so that the boat is glowing evenly) eventually the gold will melt at this point the pressure will rise especially if this is the first time a gold slug is melted. Limit the current so that the pressure never exceeds 5 x 10-6 mbar (and ideally stays below 1 x 10-6 mbar). Once the gold has melted increase the current until the thickness monitor displays a rate of 0.5 to 1 nm s-1 then wait until the layer is almost (<2 nm away) the desired thickness (100nm is recommended a gold mirror) and turn the current down to zero. Switch the right-hand selector switch back to 0 and close the shutter on the thickness monitor controller (FTM5). Wait for about 5 mins for the system to cool down and the pressure to return to 2 x 10-7 mbar.
7. To retrieve your samples, switch the switch on the rotary stage controller to stop the sample stage rotating. Then open the nitrogen gas cylinder (set the regulator to 0.5 bar) and line to the evaporator and then press seal wait 10 seconds and then press vent on the pumping system controller. The display will show CHAMBER VENT. The chamber will take about two minutes to vent. Wait until the hissing stops and the pressure is reading 1 x 103 mbar and then attempt to open the chamber by gently lifting the bell jar. If the bell jar is hard to lift, it has not finished venting. Once you have removed the bell jar and placed it inverted on the cork ring, stop the venting process by pressing "seal" on the pumping system controller and close the nitrogen cylinder. Unbolt the substrate holder from the bottom of the driven bearing and withdraw the holder, replace the bell jar and implosion guard and then press "cycle" on the pumping system controller to pump the system down to keep the inside of the system as clean as possible. Remove your samples from the sample holder and rap it in tin foil and leave it on the evaporator for the next user.
Troubleshooting
Unable to make the pumping system vent or pump down - If the button for the operation you are trying to select is not illuminated, it is not available at this time. Try pressing "seal." This will usually make pumping and venting options available.
The pumping system controller displays HIGH VAC FAIL - Press reset on the pumping system controller, then proceed. If the fault reappears contact the SAF.
The pumping system controller displays HIGH VAC VALVE FAIL - Press reset on the pumping system controller, then proceed. If the fault reappears contact the SAF.
The pumping system controller displays CRYO-OVERTEMP... PRESS RESET TO REGENERATE - The cryo-pump has overheated. Do not press reset. The pump can probably recover without regeneration and regeneration will take several hours. If the display changes to "CRYO RECOVERED" press reset. If the display continues to show "CRYO-OVERTEMP" after you wait fifteen minutes, report the problem to the SAF.
For all other problems contact the SAF.
Back to the surface modification page