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Host-guest self-assembly in block copolymer blends.

Park WI, Kim Y, Jeong JW, Kim K, Yoo JK, Hur YH, Kim JM, Thomas EL, Alexander-Katz A, Jung YS - Sci Rep (2013)

Bottom Line: Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology.As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated.These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.

ABSTRACT
Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.

No MeSH data available.


Related in: MedlinePlus

Demonstration of pattern transfer and memory device application.(a) Schematic illustrations and corresponding SEM images of several nanostructures made from the binary BCP self-assembly. Dots-in-pores, nanorings, dots-in-honeycomb, and rings-in-pores are presented. (b) Guided assembly of nanostructure using topographical templates. Because of the affinity of the PS block to the PS brush grafted on the templates, half-cut PS perforations containing PFS spheres align in contact with the side-walls. (c) Self-assembled nanostructures on a GST thin film. (d) Phase-change memory (PCM) nanoring structure fabricated by a metal (Pt) deposition and plasma etch-back process. (e) Schematic illustration of ring-type PCM cell arrays (Pt/GST/TiN/TiW). (f) I-V characteristics of the nanoring PCM structure using C-AFM, showing clear phase-change switching with a very low switching current.
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f7: Demonstration of pattern transfer and memory device application.(a) Schematic illustrations and corresponding SEM images of several nanostructures made from the binary BCP self-assembly. Dots-in-pores, nanorings, dots-in-honeycomb, and rings-in-pores are presented. (b) Guided assembly of nanostructure using topographical templates. Because of the affinity of the PS block to the PS brush grafted on the templates, half-cut PS perforations containing PFS spheres align in contact with the side-walls. (c) Self-assembled nanostructures on a GST thin film. (d) Phase-change memory (PCM) nanoring structure fabricated by a metal (Pt) deposition and plasma etch-back process. (e) Schematic illustration of ring-type PCM cell arrays (Pt/GST/TiN/TiW). (f) I-V characteristics of the nanoring PCM structure using C-AFM, showing clear phase-change switching with a very low switching current.

Mentions: Figure 7a provides a set of the nanoscale geometries that can be obtained through the binary assembly and pattern transfer processes. Structures of dots-in-pores, nanorings, rings-in-pores, and dots-in-honeycomb are demonstrated in Figure 7a with corresponding SEM images. The assembly of these nanostructures can be guided by topographic templates, which control the position and orientation of the microdomain lattice, as presented in Figure 7b. These patterns can also be exploited as useful templates for making functional nanostructures. As an example, Ge2Sb2Te5 (GST) nanorings were fabricated by forming self-assembled structures on GST films (Figure 7c) followed by the use of a Damascene-like pattern reversal process, which was described in detail in Figure S12 and our previous report43. Figure 7d and 7e illustrate a phase-change memory (PCM) cell array with a Pt/GST/TiN nanoring stacking structure with outer and inner diameters of 45 nm and 20 nm, respectively. For measurement of the current-voltage (I-V) characteristics, a conductive atomic force microscope (C-AFM) tip with a radius of 30 nm was used. The results show a clear switching behavior from a high-resistance (amorphous) to a low-resistance (crystalline) state at a threshold voltage of about 3.0 V with a sufficient sensing window (>103 at a read voltage of 2.5 V) (Figure 7f). It is noteworthy that these nanoscale GST rings have a very low switching current of approximately 2 μA, which is close to the lowest programming current ever reported for nanostructures44. This is attributed to the hollow nature combined with the small dimension of the GST nanorings, which significantly shrinks their switching volumes. The nanoring geometry can also be used for the fabrication of multi-bit-storage magnetic memory elements4546 without relying on high-resolution templates. Moreover, the suboxide nanostructures directly prepared from inorganic-containing BCPs without employing pattern-transfer processes can be applied to high-density resistive memory applications, as we reported previously47. This simple demonstration shows the promise of binary BCP blend nanostructures as useful lithographic templates for the fabrication of ordered functional nanostructures.


Host-guest self-assembly in block copolymer blends.

Park WI, Kim Y, Jeong JW, Kim K, Yoo JK, Hur YH, Kim JM, Thomas EL, Alexander-Katz A, Jung YS - Sci Rep (2013)

Demonstration of pattern transfer and memory device application.(a) Schematic illustrations and corresponding SEM images of several nanostructures made from the binary BCP self-assembly. Dots-in-pores, nanorings, dots-in-honeycomb, and rings-in-pores are presented. (b) Guided assembly of nanostructure using topographical templates. Because of the affinity of the PS block to the PS brush grafted on the templates, half-cut PS perforations containing PFS spheres align in contact with the side-walls. (c) Self-assembled nanostructures on a GST thin film. (d) Phase-change memory (PCM) nanoring structure fabricated by a metal (Pt) deposition and plasma etch-back process. (e) Schematic illustration of ring-type PCM cell arrays (Pt/GST/TiN/TiW). (f) I-V characteristics of the nanoring PCM structure using C-AFM, showing clear phase-change switching with a very low switching current.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824169&req=5

f7: Demonstration of pattern transfer and memory device application.(a) Schematic illustrations and corresponding SEM images of several nanostructures made from the binary BCP self-assembly. Dots-in-pores, nanorings, dots-in-honeycomb, and rings-in-pores are presented. (b) Guided assembly of nanostructure using topographical templates. Because of the affinity of the PS block to the PS brush grafted on the templates, half-cut PS perforations containing PFS spheres align in contact with the side-walls. (c) Self-assembled nanostructures on a GST thin film. (d) Phase-change memory (PCM) nanoring structure fabricated by a metal (Pt) deposition and plasma etch-back process. (e) Schematic illustration of ring-type PCM cell arrays (Pt/GST/TiN/TiW). (f) I-V characteristics of the nanoring PCM structure using C-AFM, showing clear phase-change switching with a very low switching current.
Mentions: Figure 7a provides a set of the nanoscale geometries that can be obtained through the binary assembly and pattern transfer processes. Structures of dots-in-pores, nanorings, rings-in-pores, and dots-in-honeycomb are demonstrated in Figure 7a with corresponding SEM images. The assembly of these nanostructures can be guided by topographic templates, which control the position and orientation of the microdomain lattice, as presented in Figure 7b. These patterns can also be exploited as useful templates for making functional nanostructures. As an example, Ge2Sb2Te5 (GST) nanorings were fabricated by forming self-assembled structures on GST films (Figure 7c) followed by the use of a Damascene-like pattern reversal process, which was described in detail in Figure S12 and our previous report43. Figure 7d and 7e illustrate a phase-change memory (PCM) cell array with a Pt/GST/TiN nanoring stacking structure with outer and inner diameters of 45 nm and 20 nm, respectively. For measurement of the current-voltage (I-V) characteristics, a conductive atomic force microscope (C-AFM) tip with a radius of 30 nm was used. The results show a clear switching behavior from a high-resistance (amorphous) to a low-resistance (crystalline) state at a threshold voltage of about 3.0 V with a sufficient sensing window (>103 at a read voltage of 2.5 V) (Figure 7f). It is noteworthy that these nanoscale GST rings have a very low switching current of approximately 2 μA, which is close to the lowest programming current ever reported for nanostructures44. This is attributed to the hollow nature combined with the small dimension of the GST nanorings, which significantly shrinks their switching volumes. The nanoring geometry can also be used for the fabrication of multi-bit-storage magnetic memory elements4546 without relying on high-resolution templates. Moreover, the suboxide nanostructures directly prepared from inorganic-containing BCPs without employing pattern-transfer processes can be applied to high-density resistive memory applications, as we reported previously47. This simple demonstration shows the promise of binary BCP blend nanostructures as useful lithographic templates for the fabrication of ordered functional nanostructures.

Bottom Line: Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology.As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated.These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.

ABSTRACT
Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs.

No MeSH data available.


Related in: MedlinePlus