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Procedure for Organic Single Crystal Growth:
For reviews see:
1. R. W. I. de Boer, M. E. Gershenson, A. F. Morpurgo and V. Podzorov, “Organic single-crystal field-effect transistors”,
Phys. Stat. Solidi 201, 1302 (2004);
2. V. Podzorov "Charge carrier transport in single-crystal organic field-effect transistors", in Organic Field-Effect Transistors
(Ed. Z. Bao and J. Locklin, pp. 27-72 (Taylor & Francis, 2007)).
The corresponding diagrams and photographs of the Rutgers growth system are in the end of this file
Pre-growth cleaning procedure (everything is done wearing powder-free gloves):
1. Clean up the bench top with tissue and acetone and cover it with clean sheets of paper to prevent further contamination; place
about one foot long sheet of Al foil on the paper; perform all work with rubrene powder and quartz tubes on this sheet.
2. Thoroughly clean all tools involved in the procedure (spatula, stoppers, etc.) with acetone and tissue; Also clean the inlet and outlet
gas stoppers of the furnace with tissue and acetone.
3. Clean the inner surface of the outer (big) growth tube with acetone by blocking one end of the tube with a silicone stopper, inserting
a tissue ball and pouring some acetone in the tube, then closing off the other end with another stopper. Shake the tube with
considerable force so the tissue ball passes through the tube back and forth and cleans off any residue; discard the used acetone into a
collection container (a round Pyrex jar with a red lid - this jar is used only for accumulating rubrene waste).
4. Repeat the above step twice (or, until you see no residue in the tube) using a low grade acetone (large wash bottle). Useful way to
tell if the tube is clean is to look through the tube at the ceiling lights. After this, remove the stoppers and flow some high purity
acetone (small wash bottle) through the tube by sprinkling acetone from the wash bottle into one end of the tube and allowing it to
flow freely through and out of the tube (into the collection container); rotate the tube slowly while doing this. This step helps to get rid
of any fibers, lint, particles or crystals loosely attached to the inner walls of the quartz tube. Wipe the outer surface of the tube with
tissue soaked in acetone and then leave to dry. Nitrogen gun can also be used for drying but may sometimes leave residue.
5. Next we clean the inner growth (small) tube. First, hold the tube by one end and gently flow acetone on the inner surface of the
tube to pre-clean it. The acetone will partially dissolve the crystalline rubrene deposit and wash away loosely attached crystals. This
acetone should be allowed to flow out of the tube and into the collection container. Second, wrap the spatula with a piece of tissue
small enough to be inserted into the inner tube. Soak the tissue with acetone and wipe the inner surface of the tube. Repeat this until
you can see absolutely no red residue on the inner surface of the small tube. Wipe the outer surface of the small tube with tissue
soaked in acetone until no trace of rubrene can be seen. Hold the tube by one end, avoid as much contact as possible, again run
acetone down both the inner AND outer surfaces of the small tube. Do this several times until the tube is completely clean. Place the
tube under light and look to make sure that there is no more residue on the tube. Cleanness is very important in each step of crystal
growth, especially when dealing with the inner growth tube. Leave the small tube on the Al foil to dry, could also be blown dry with a
nitrogen gun.
Growth procedure (Starting the growth):
1. Load rubrene powder into one end (close to the opening) of the inner growth tube with a clean spatula.
Around 2 spoonfuls for a medium size growth;
2. Mark the outer growth tube at 5.5 inches from the left end (this end is marked with a letter “R” scratched out on quartz).
3. Turn the inner tube with a rubrene load and insert it into the left end of the outer tube (insert it in a way that the end
WITHOUT the rubrene powder goes in first). Push the small tube in using the spatula (without disturbing the rubrene powder
too much), until the center of the load reaches the 5.5-in mark on the outer tube.
4. Now carefully place the whole two-tube assembly into the furnace with the end containing the load on the left.
5. Connect the cleaned inlet and outlet gas stoppers of the furnace to the outer quartz tube by inserting them into the tube gently,
but with a certain force, until you see a clear section of a good contact between the silicone stoppers and the outer tube.
While doing this, it is important to minimize shaking the tube to prevent the loaded powder from spreading.
6. There is a visible mark at the center of the furnace’s heater indicating the maximum temperature point on the temperature profile
along the furnace. Adjust the horizontal position of the growth tube until the left end of the tube is 5.5 inches from that mark
(use a ruler to precisely measure this). This ensures that the load is positioned at the maximum on the temperature profile.
7. Tighten the tube holder on the left side of the furnace to keep the tube in place; make sure that the tube is coaxial with the
furnace (sits at the center) and not touching the inner walls of the furnace. The right end of the quartz tube (near the water coil)
can be slightly raised with the adjustable hook so the entire tube does not touch the furnace during the growth. These adjustments
ensure a uniform temperature gradient during the growth.
8. When everything is placed right, turn the cooling water on just until the teeth of the spinning wheel indicator become invisible.
Turn the gas on to the appropriate flow level by adjusting the black plastic knob on the gas flow meter (the flow should be about
100 cc/min - in our setup this corresponds to the flow meter at a black label) and wait 5-10 minutes for the gas to pass through the
cold tube and expel the air. Note, the compressed gas cylinder main and outlet valves (before and after the regulator) must be
fully opened; the outlet gas pressure must be set to just a few psi in advance by using the gas regulator knob; the flow rate is
to be controlled by the black plastic knob on the gas flow meter.
9. Turn on the furnace temperature controller and set the growth temperature to Tset = 310 oC
(depending on the desired crystal morphology and size, Tset should be adjusted).
10. Once the temperature has reached the set value, double check that the gas and water flows are normal.
11. Growth time depends on the material, set temperature, flow rate and the desired crystal morphology. To achieve robust bulky
rubrene crystals (good for discrete free-standing devices) we grow rubrene at 310 oC for about 48 h (the load size is ~ 300 mg).
Growth procedure (Finishing the growth):
1. After the growth, turn the furnace off by unplugging the power cord of the temperature controller and waiting for 45-60 minutes
for the furnace to cool down without turning off the gas and water. Thoroughly clean the round metal sample container with
tissues and acetone - you will be using it for collecting the crystals.
2. When the furnace completely cools down to room temperature, turn off the gas and water and carefully remove the silicone plugs;
remove the tube from the furnace without disturbing the crystals.
3. Place the tube on the counter and use a spatula to retrieve the small inner tube. Collect the grown crystals into a pre-cleaned
metal box.
4. Scrape off the highly pure crystalline rubrene material deposited on the inner walls of the small tube into another pre-cleaned
metal box for future use (this box must be labeled “pure leftovers for re-growths”).
5. Label the container with collected crystals: this must include information about the material, growth date, major conditions,
such as the set temperature, type and flow rate of gas, growth duration and what material was loaded (see an example below).
Post-growth cleaning:
1. Clean all the tools used in the process, including spatulas and stoppers, and place them into the
appropriate plastic box with a lid.
2. Clean the gas line silicone plugs with tissue and acetone and wrap them in Al foil.
3. Pre-clean both outer and inner quartz tubes with acetone and tissue for future growths and
let them dry on the counter (do not store dirty tubes at an open counter for a long time).
Make sure to collect crystalline material into the round Pyrex jar and close the lid.
When accumulated, this material can be used for re-growths.
4. Dispose of any Al foil left on the table (if it is contaminated) and clean up any rubrene spills.
5. Replace the papers covering on the table once a week (or earlier, if any noticeable contamination occurred).
6. Once a week a thorough clean-up of the room must be performed according to the cleaning schedule posted on our web site.
Physical vapor transport (PVT) crystal growth
PVT crystal growth (in a gas stream)
Possible to grow most of the small
molecules:
rubrene, tetracene, pentacene, TCNQ,
phthalocyanines
Thick & bulky
For reviews see:
1. R. W. I. de Boer, M. E. Gershenson,
A. F. Morpurgo and V. Podzorov,
“Organic single-crystal field-effect
transistors”, Phys. Stat. Solidi 201,
1302 (2004);
2. C. Reese and Z. Bao,
“Organic Single Crystal Field-Effect
Transistors”,
Materials Today 10, 20 (2007)
Ultrathin & flexible
(d < 500 nm)
• Podzorov et al., Appl.Phys.Lett. 82, 1739 (2003)
• Podzorov et al., Appl.Phys.Lett. 83, 3504 (2003)
Rutgers Physical Vapor Transport (PVT) growth furnace
2-in OD Ni-plated copper tube
Quartz fabric belt heater
(6-in long winding)
1/4-in Ni-plated copper
tube coil
soldered to
the main tube
(for water cooling)
water in/out
TC
gas in
gas out
6 in
19-mm ID quartz tube
holders/clamps
platform
18 in
Next page shows just a photo, without labels
Power supply
(a combination of Omega
T-controller and a
solid state relay)
Unlabeled photo of PVT crystal growth furnace