Anyone who can add a recipe to this list, please do so. - Melina
For additional recipes see: other recipes
For the group furnace schedule, go here.
For information on evaporating Fe catalyst, see the Nanofabrication page: recipes.
(The following is from the Minot group wiki):
Thermal evaporation or sputtering of Fe Clean the oxide surface (McEuen group uses an Oxygen plasma, acid cleaning is also effective) Evaporate 0.2 nm layer of Fe (it is invisible when you inspect the chip) The Fe layer will bead up on oxide surface at high temperature and give tube diameters < 3 nm. It may help to have an under layer of Aluminum. The Aluminum will naturally oxidize and people hypothesis that an Aluminum oxide surface will help produce small beads of Fe. Matt has a reference.
Alumina supported catalyst The advantage of alumina supported catalyst is the high surface area of the alumina. The high surface area leads to more nanotube nucleation sites. A disadvantage is that alumina nanoparticles, together with sticky nanotube grass, stick to the AFM tip during imaging (it is best to avoid imaging directly over the alumina!). The original recipe for this catalyst was published in Nature in 1998 (Kong et al.). Kong used 45 mL of IPA instead of 45 mL of DI water, but IPA is not compatible with photoresist patterning (IPA is only compatible with ebeam resist). The original recipe from Kong et al. also has an additional baking step after solution deposition. Here is the updated recipe developed in the McEuen group. The Dekker group still uses the IPA solvent: 60 mg Fe(NO3)3•9H2O * see the suggestion below 15 mg MoO2(acac)2 * see the suggestion below 45 mg Al2O3 (Alumina) 45 mL DI water Stir (10 min with magnetic stir rod) and then sonicate several hours when first made, should look red () * Suggestion Our current formula has four times as much Iron Nitrate and Molybdenum Acetate as the preceding formula. This was done to increase our return on the number of nanotubes. We know the new formula does grow tubes, but it does not look like it makes more tubes than the recipe at lower concentrations like we hoped. Another potentially important difference is that we are using Mo(acetate)2. Where Mo is in the 2nd oxidation state. The MoO2(acetate)2 is in the 6th oxidation state. We tried growing tubes using a solution made exclusively of of Mo(acetate)2 and alumina. We did not find any tubes grown using this solution. So it looks like all tube growth (so far) is due to either Fe or an FeMo alloy.
Iron nitrate solution Mix 60 mg Fe(NO3)3•9H2O, clean with 45 mL DI or IPA
Ferritin solution Always keep bulk supply of Ferritin in the fridge at ~ 4deg C Dilute bulk supply at least 1:100 in DI water (Josh has details) To get a reliable and uniform distribution of Ferritin the solution should be spun onto the chip and the chip should be pre-treated to get a hydrophilic surface.
Depositing water-based catalyst We had trouble getting alumina to stick to brand new silicon oxide wafers. Fresh silicon oxide is so hydrophillic that the alumina has no reason to deposit (it just stays dissolved in the water). Ironically, the sticking procses is aided by photoresist residue, or the residue deposited by a gelpak. Sonicate iron nitrate based catalysts 30-60 min (Ferritin should not be sonicated) Stir until ready to use Add catalyst to chips in large mound, wait 2-10 minutes, rinse with DI water If you are using a photoresist mask, you will now have to remove the photoresist (5 minute soak in acetone) Rinse with acetone and then IPA, dry with N2 Check with optical microscope in Janet Tate's lab. Growth may be better if you do it within 3 hours of depositing the catalyst.
The CVD furnace uses quartz tubing to contain the gas flow while everything (chip, catalyst, gas) is heated to high temperature. We have spare quartz tubes in case the tube becomes contaminated. Any leak in the system will stop nanotube growth. We leak check using the standard “soapy-water” technique (buy a bottle from home depot). If we see bubbles at any connector, it must be unfastened and refitted (threaded connectors we use teflon tape). Even though the furnace operates slightly higher than 1 atmosphere, a gas leak will cause an exchange of gases both ways (between the room and the growth region). We believe that the O2 leaks from the room into the growth region are enough to stop nanotube growth. A brand new quartz tube is never a bad idea. Especially if you suspect contamination (for example, some annealed gold at high temp in the previous quartz tube).
Safety note about the Moldatherm Insulation (the white, chalky ceramic insulator in the CVD furnace): Avoid breathing the dust, or contact with skin, eyes, and mouth. Full toxicology is only preliminary, but prolonged respiratory exposure has led to cancer in test animals. At temperatures above 980 C, Moldatherm can partially convert into cristobalite. OSHA limits exposure to cristobalite to 0.05 mg/m^3 of respirable dust. No limit has yet been set for breathing Moldatherm dust. Use gloves whenever operating the CVD or handling the quartz tubing. Do not touch skin or wipe eyes until after washing hands. If heated above 980 C, a respiratory filter is recommended while in use.
More recipes can be found on the other recipes page.
Flying catalyst growth
Check that the gas cylinders have plenty of gas (the pressure inside a full cylinders is about 1500 psi).
Open furnace lid. Slide sample into growth tube, and use the long metal stick to push the sample to the center of the tube. Mark the correct final position of the tube by drawing a line at the edge of the furnace. Connect flow channels, and close the furnace.
Open gas cylinders to give the flow controller access. Adjust setpoints for all gases in the controller menu (Ar=0.8 SLM, H2=0.2 SLM, CH4=0.8 SLM, C2H4=5.5 SCCM (NOTE different units)).
Begin flowing Argon, and check that the oil is bubbling and that the controller reads 0.8 SLM in “Act. flow.”
Turn on the furnace, set to 700ºC.
When furnace reaches 700ºC (~5 minutes), turn on H2 at the controller, leaving the Ar on.
Let H2 and Ar flow over sample for 15 minutes.
Slide tube out carefully until your sample rests ~4-5” outside the furnace.
Turn off the flow of H2, leaving the Ar on.
Raise the furnace setpoint to 1040ºC and wait for it to stabilize (~3 minutes).
Turn on all gases (Ar, H2, CH4, and C2H4). Let it flow for 2-4 minutes.
Simultaneously: reduce the temperature setpoint to 915ºC, turn off the Ar, and slide the tube into the marked position. Let it grow for 10 minutes.
Turn on Ar, turn off H2 and CH4 and C2H4. Lower furnace to 0ºC and prop it open with the provided block. At 600ºC you can open the furnace; at 200ºC you can remove your sample.
Turn off Ar and disconnect flow channels.
Close gas tanks.
Aligned array growth
Check that the gas cylinders have plenty of gas (the pressure inside a full cylinders is about 1500 psi).
Open furnace lid. Slide sample into growth tube. Use the long metal stick to push the sample to the center of the furnace (optimized growth location is ~1 inch upstream of the center). Connect flow channels, making sure not to move your sample; close the furnace.
Open gas cylinders to give the flow controller access. Adjust setpoints for all gases in the controller menu (Ar=1 SLM, H2=0.3 SLM, CH4=1.9 SLM).
Begin flowing Argon (1 SLM), and check that the oil is bubbling and that the controller reads 1 SLM in “Act. flow.” Use a bottle of Sneak to check for leaks at both ends of the tube.
Turn on the furnace, set to 900ºC.
When furnace reaches 900ºC (~10 minutes), turn on H2 at the controller, and turn off the Ar.
Let H2 flow over sample for 5 minutes.
Turn on CH4, and let it grow for 1 hour (20 minutes seems to produce the same results and is currently being used).
Turn on Ar, turn off H2 and CH4. Lower furnace to 0ºC and prop it open with the provided block. At 600ºC you can open the furnace; at 200ºC you can remove your sample.
Turn off Ar and disconnect flow channels.
Close gas tanks.
Ethylene growth
Check that the gas cylinders have plenty of gas (the pressure inside a full cylinders is about 1500 psi).
Open furnace lid. Slide sample into growth tube. Use the long metal stick to push the sample to the center of the furnace (optimized growth location is ~1 inch upstream of the center). Connect flow channels, making sure not to move your sample; close the furnace.
Open gas cylinders to give the flow controller access. Adjust setpoints for all gases in the controller menu (Ar=1 SLM, H2=0.2 SLM, C2H4=5.5 SCCM).
Begin flowing Argon (1 SLM), and check that the oil is bubbling and that the controller reads 1 SLM in “Act. flow.”
Turn on the furnace, set to 800ºC.
When furnace reaches 800ºC (~10 minutes), turn on H2 at the controller, and turn off the Ar.
Let H2 flow and butt tail plug over sample for 5 minutes.
Turn on C2H4, and let it grow for 10 minutes.
Turn on Ar, turn off H2 and C2H4. Lower furnace to 0ºC and prop it open with the provided block. At 600ºC you can open the furnace; at 200ºC you can remove your sample.
Turn off Ar and disconnect flow channels.
Close gas tanks.