Page 59 - 2021電子物理系系刊

2. Dry Transfer
During the process, the flakes produced by mechanical exfoliation are not
exposed or not directly exposed to water, where a polymer layer as the transfer
medium to block wetting. Using this technique, flakes can also be precisely located
at desired positions. However, in our fabrication, the 2D material still unavoidably
comes into contact with the aqueous solution. But we use TRT tape to attach the
PMMA/MoS2 to the substrate. This process can avoid the sample affected by the
surface tension of the water.
(1) Cutting the MoS2/sapphire into appropriate size, generally speaking, we will cut
into 1 cm*1 cm.
(2) First, prepare the top-flake exfoliation substrate by spin-coating a PMMA layer.
After the surface is soft baked for 2 minutes, the PMMA on the edge is removed
with a knife.
(3) Attach the TRT tape to PMMA/MoS2/sapphire.
(4) The TRT/PMMA/MoS2/sapphire is dip-floated in 20% NH4OH(aq) at 80 °C . The
TRT/PMMA/MoS2 is detached and allowed to float in NH4OH(aq), and the
sapphire is sunk.
(5) Put the TRT/PMMA/MoS2 in the glove box and dry it all day.
(6) Attach the TRT/PMMA/MoS2 on the target substrate in the glove box.
(7) Put the TRT/PMMA/MoS2/substrate on the heater at 150 °C for 10 seconds to
remove the TRT tape.
(8) The PMMA/MoS2/substrate is dip-floated in Acetone for 2hours to remove
PMMA.
(9) Use Acetone and IPA( Isopropyl alcohol) to remove organic residues in surface.

3. Vibrat on-assist d Transfer
Most of the time, the transfer efficiency of 2D materials is very low. This
causes great damage to the fabrication. Even if we grow high-quality materials, it is
difficult to apply them to electronic device. So we found that the vibration-assisted
method can improve transfer process.

(1) Cutting the MoS2/sapphire into appropriate size, generally speaking, we will cut
into 1 cm*1 cm.
(2) First, prepare the top-flake exfoliation substrate by spin-coating a PMMA layer.
After the surface is soft baked for 2 minutes, the PMMA on the edge is removed
with a knife.
(3) Attach the TRT tape to PMMA/MoS2/sapphire.
(4) The TRT/PMMA/MoS2/sapphire is dip-floated in 20% NH4OH(aq) at 25 °C. Then
put the whole system into the vibration washing machine for 15 minutes. The
TRT/PMMA/MoS2 is detached and allowed to float in NH4OH(aq), and the
sapphire is sunk.
(5) Put the TRT/PMMA/MoS2 in the glove box and dry it all day.
(6) Attach the TRT/PMMA/MoS2 on the target substrate in the glove box.
(7) Put the TRT/PMMA/MoS2/substrate on the heater at 150 °C for 10 seconds to
remove the TRT tape.
(8) The PMMA/MoS2/substrate is dip-floated in Acetone for 2hours to remove
PMMA.
(9) Use Acetone and IPA( Isopropyl alcohol) to remove organic residues in surface.
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