Preparing method of two-dimensional materials with controlled number of layers
View Patent ↗The present disclosure relates to a preparing method of two-dimensional materials with a controlled number of layer including depositing a metal thin film on a surface of a bulk material; exfoliating a two-dimensional material from the surface of the bulk material together with the metal thin film; and transferring the two-dimensional material onto a substrate, in which the number of layers of the two-dimensional material to be exploited is controlled by controlling an internal stress of the metal thin film.
1 . A preparing method of a two-dimensional material with a controlled number of layers comprising:
depositing a metal thin film on a surface of a bulk material;
exfoliating a two-dimensional material from the surface of the bulk material together with the metal thin film; and
transferring the two-dimensional material onto a substrate,
wherein the number of layers of the two-dimensional material to be exfoliated is controlled by controlling an internal stress of the metal thin film,
wherein the internal stress σ f of the metal thin film is represented by the following Equation 1 and when a total accumulated strain energy U Total represented by the following Equation 2 reaches a binding energy γ between the two-dimensional materials, the two-dimensional material is exfoliated,
σ
f
=
γ
U
Total
[
Equation
1
]
wherein in Equation 1, γ is a binding energy of a two-dimensional material and U Total is a total accumulated strain energy,
U
Total
=
(
1
-
v
f
)
2
Y
f
t
f
σ
f
2
+
(
1
-
v
s
)
2
Y
s
t
f
2
t
s
σ
f
2
[
12
(
d
spall
t
s
)
3
-
24
(
d
spall
t
s
)
2
+
16
(
d
spall
t
s
)
]
[
Equation
2
]
wherein in Equation 2, v s and v f are Poisson's ratios of a bulk material and a metal thin film, respectively, Y s and Y f are Young's modulus of a bulk material and a metal thin film, respectively, t s and t f are thicknesses of a bulk material and a metal thin film, respectively, and d spall is a spall depth.
2 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , wherein as the internal stress of the metal thin film is reduced, the number of layers of the two-dimensional material to be exfoliated is increased.
3 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , further comprising:
removing the metal thin film.
4 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 3 , wherein the removing of the metal thin film is performed by impregnating the metal thin film into a metal etchant.
5 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , wherein the depositing of the metal thin film is performed by a method selected from the group consisting of E-beam evaporation, thermal evaporation, vacuum thermal evaporation, plasma deposition, sputtering, atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), and combinations thereof.
6 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , wherein the metal includes one selected from the group consisting of Ag, Au, Cu, Pd, and combinations thereof.
7 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , wherein the two-dimensional material includes one selected from the group consisting of transition metal chalcogenide, graphene, fluorographene, graphene oxide, hexagonal boron nitride (h-BN), boron carbon nitride (BCN), black phosphorus, and combinations thereof.
8 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 7 , wherein the transition metal chalcogenide includes a material denoted by the following Chemical Formula 1,
MX 2 [Chemical Formula 1]
wherein in the above Chemical Formula 1, M is a transition metal selected from Mo, W, Te, Re, V, Nb, Ta, Ti, Zr, Hf, Co, Rh, Ir, Ni, Pd, or Pt and X is a chalcogenide element selected from S, Se, or Te.
9 . The preparing method of a two-dimensional material with a controlled number of layers according to claim 1 , wherein the exfoliation is performed using a thermal release tape (TRT).