Procedure for Organic Single Crystal Growth:

1
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.
2
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 furnaces 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).
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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.
4
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 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)
Thick bulky
Ultrathin flexible (d lt 500 nm)
Podzorov et al., Appl.Phys.Lett. 82, 1739
(2003) Podzorov et al., Appl.Phys.Lett. 83,
3504 (2003)
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Rutgers Physical Vapor Transport (PVT) growth
furnace
2-in OD Ni-plated copper tube
1/4-in Ni-plated copper tube coil soldered to
the main tube (for water cooling)
Quartz fabric belt heater (6-in long winding)
water in/out
TC
gas in
gas out
6 in
19-mm ID quartz tube
holders/clamps
platform
18 in
Power supply (a combination of Omega
T-controller and a solid state relay)
Next page shows just a photo, without labels
6
Unlabeled photo of PVT crystal growth furnace