5.2 Silicon
Silicon is one of the most widely used semiconducting materials due to its abundance in nature and its good electrical performance. However, it is not easy to
combine BCP SA with silicon deposition due to the decomposition of polymeric
materials at high temperatures. The typical processing temperature for chemical
vapor deposition of silicon is above 300
C, which is too high for most organic
materials to survive. Thus, nanostructured porous templates prepared from BCP
SA (i.e., from pure organic materials) are considered inappropriate for silicon
deposition. In order to prevent porous template collapse, “hard” porous templates
composed of inorganic materials such as oxides have been used that are durable at
these temperatures.
Arora et al. prepared nanoporous oxide templates via BCP + oxide sol SA and
subsequent thermal removal of polymeric materials [44]. The resulting hard
templates maintained their nanostructure during silicon vapor deposition as well as
subsequent laser annealing for generating single-crystal silicon. This hard template
approach can be generalized, even for other materials that require high temperature
vapor deposition processes, thus being a promising route for fabrication of nextgeneration nanomaterials for electronic and energy-related applications.
5.3 Metals
Recently, nanostructured metals have attracted much attention for a variety of
applications such as metamaterials [15], plasmonics [54], and catalysis. The fabrication of nanostructured metals from BCP SA can be very powerful compared
with other top-down approaches because 3D large-scale fabrication of materials is
possible.
One strategy for formation of nanostructured metals is to utilize BCP + ligandstabilized metal nanoparticle SA (see Fig. 9) [42]. In this way, superstructures
of metal nanoparticles are structure-directed by BCP SA. This approach enables
metal nanostructure control in a one-pot fashion and is thus advantageous
over other approaches that may require multiple tedious steps. However, the high
surface energy of metals renders it very difficult to disperse metal nanoparticles
because, without good passivation, they aggregate to minimize their surface area.
Thus, in order to avoid metal nanoparticle aggregation, organic ligands have been
employed to reduce their surface energy.
Platinum (Pt) nanoparticles were structure-directed by a BCP, resulting in 1D
lamellar and 2D hexagonal superstructures [10, 42]. Such superstructured metal
nanoparticles can be further processed to generate highly ordered mesoporous metals
via pyrolysis. These mesoporous metals are promising for electrocatalysis [42].
This BCP + ligand-stabilized nanoparticle SA can be generalized to other types
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
279
Silicon is one of the most widely used semiconducting materials due to its abundance in nature and its good electrical performance. However, it is not easy to
combine BCP SA with silicon deposition due to the decomposition of polymeric
materials at high temperatures. The typical processing temperature for chemical
vapor deposition of silicon is above 300
C, which is too high for most organic
materials to survive. Thus, nanostructured porous templates prepared from BCP
SA (i.e., from pure organic materials) are considered inappropriate for silicon
deposition. In order to prevent porous template collapse, “hard” porous templates
composed of inorganic materials such as oxides have been used that are durable at
these temperatures.
Arora et al. prepared nanoporous oxide templates via BCP + oxide sol SA and
subsequent thermal removal of polymeric materials [44]. The resulting hard
templates maintained their nanostructure during silicon vapor deposition as well as
subsequent laser annealing for generating single-crystal silicon. This hard template
approach can be generalized, even for other materials that require high temperature
vapor deposition processes, thus being a promising route for fabrication of nextgeneration nanomaterials for electronic and energy-related applications.
5.3 Metals
Recently, nanostructured metals have attracted much attention for a variety of
applications such as metamaterials [15], plasmonics [54], and catalysis. The fabrication of nanostructured metals from BCP SA can be very powerful compared
with other top-down approaches because 3D large-scale fabrication of materials is
possible.
One strategy for formation of nanostructured metals is to utilize BCP + ligandstabilized metal nanoparticle SA (see Fig. 9) [42]. In this way, superstructures
of metal nanoparticles are structure-directed by BCP SA. This approach enables
metal nanostructure control in a one-pot fashion and is thus advantageous
over other approaches that may require multiple tedious steps. However, the high
surface energy of metals renders it very difficult to disperse metal nanoparticles
because, without good passivation, they aggregate to minimize their surface area.
Thus, in order to avoid metal nanoparticle aggregation, organic ligands have been
employed to reduce their surface energy.
Platinum (Pt) nanoparticles were structure-directed by a BCP, resulting in 1D
lamellar and 2D hexagonal superstructures [10, 42]. Such superstructured metal
nanoparticles can be further processed to generate highly ordered mesoporous metals
via pyrolysis. These mesoporous metals are promising for electrocatalysis [42].
This BCP + ligand-stabilized nanoparticle SA can be generalized to other types
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
279