Nanodomain Swelling Block Copolymer Lithography for Morphology Tunable Metal Nanopatterning

Ordered metal nanopatterns are crucial requirements for electronics, magnetics, catalysts, photonics, and so on. Despite considerable progress in the synthetic route to metal nanostructures, highly ordered metal nanopatterning over a large‐area is still challenging. Nanodomain swelling block copolymer lithography is presented as a general route to the systematic morphology tuning of metal nanopatterns from amphiphilic diblock copolymer self‐assembly. Selective swelling of hydrophilic nanocylinder domains in amphiphilic block copolymer films during metal precursor loading and subsequent oxygen based etching generates diverse shapes of metal nanopatterns, including hexagonal nanoring array and hexagonal nanomesh and double line array in addition to common nanodot and nanowire arrays. Solvent annealing condition of block copolymer templates, selective swelling of hydrophilic cylinder nanodomains, block copolymer template thickness, and oxygen based etching methods are the decisive parameters for systematic morphology evolution. The plasmonic properties of ordered Au nanopatterns are characterized and analyzed with finite differential time domain calculation. This approach offers unprecedented opportunity for diverse metal nanopatterns from commonly used diblock copolymer self‐assembly.     

Fabrication of Ordered Nanostructured Arrays Using Poly(dimethylsiloxane) Replica Molds Based on Three‐Dimensional Colloidal Crystals

Hexagonally arrayed structures of colloidal crystals with uniform surface are a good candidate for master molds to be used in soft lithography. Here, the fabrication of periodically arrayed nanostructures using poly(dimethylsiloxane) (PDMS) molds based on three‐dimensionally (3D) ordered colloidal crystals is reported. A robust, high‐quality 3D colloidal‐crystal master molds is prepared using the colloidal suspension containing a water‐soluble polymer. The surface patterns of the 3D colloidal crystals can then be transferred onto a polymer film via soft lithography, by means of the replication of the surface pattern with PDMS. Various hexagonally arrayed nanostructure patterns can be fabricated, including close‐packed and non‐close‐packed 2D arrays and honeycomb structures by the structural modification of the 3D colloidal‐crystal templates. The replicated hexagonally arrayed structures can also be used as templates for producing colloidal crystals with 2D superlattices.     

Buckling Patterns of Graphene–Boron Nitride Alloy on Ru(0001)

Buckling nanopatterns of monoatomic layer 2D materials on metal substrates attract significant attention due to their rich interface morphology affecting electronic applications. An experimental–theoretical study of a 2D boron–nitrogen–carbon (B _{x /2}N _{x /2}C_1−x ) alloy on a Ru(0001) surface is conducted and a profound relation between the composition x and the degree of buckling is discovered. Experimentally, real carbon–boron–nitrogen alloys on the Ru(0001) surface are demonstrated and various morphologies of pure and mixed compounds are shown. Density functional theory calculations are further carried out using the supercells of graphene, hexagonal boron nitride (h‐BN), and random BNC on Ru(0001), as well as Monte Carlo simulations for elucidating the kinetics of their growth. The results show that unlike pure compounds (h‐BN or C), the carbon–boron–nitrogen mix on Ru(0001) mostly exists in an uncorrugated form, thus greatly improving the interface contact. The likely cause of the diminished corrugation is a softening of bond angular interactions in the alloy relative to the pure phases.     

Analysis of Improved Efficiency of InGaN Light‐Emitting Diode With Bottom Photonic Crystal Fabricated by Anodized Aluminum Oxidxe

The improved performance of a bottom photonic crystal (PC) light‐emitting diode (LED) is analyzed based on internal quantum efficiency (η_int) and light‐extraction efficiency (η_ex). The bottom PC is fabricated by anodized aluminum oxide nanopatterns and InGaN quantum wells (QWs) are grown over it. Transmission electron microscopy images reveal that threading dislocations are blocked at the nanometer‐sized air holes, resulting in improved optical emission efficiency of the QWs. From temperature‐dependent photoluminescence measurements, the enhancement of η_int is estimated to be 12%. Moreover, the enhancement of η_ex is simulated to be 7% by the finite‐difference time‐domain method. The fabricated bottom PC LED shows a 23% higher optical power than a reference, which is close to the summation of enhancements in η_int and η_ex. Therefore, the bottom PC improves LED performance through higher optical quality of QWs as well as increased light extraction.     

Monocrystalline Nanopatterns Made by Nanocube Assembly and Epitaxy

Monocrystalline materials are essential for optoelectronic devices such as solar cells, LEDs, lasers, and transistors to reach the highest performance. Advances in synthetic chemistry now allow for high quality monocrystalline nanomaterials to be grown at low temperature in solution for many materials; however, the realization of extended structures with control over the final 3D geometry still remains elusive. Here, a new paradigm is presented, which relies on epitaxy between monocrystalline nanocube building blocks. The nanocubes are assembled in a predefined pattern and then epitaxially connected at the atomic level by chemical growth in solution, to form monocrystalline nanopatterns on arbitrary substrates. As a first demonstration, it is shown that monocrystalline silver structures obtained with such a process have optical properties and conductivity comparable to single‐crystalline silver. This flexible multiscale process may ultimately enable the implementation of monocrystalline materials in optoelectronic devices, raising performance to the ultimate limit.     

Nanomanufacturing with DNA Origami: Factors Affecting the Kinetics and Yield of Quantum Dot Binding

Molecularly directed self‐assembly has the potential to become a nanomanufacturing technology if the critical factors governing the kinetics and yield of defect‐free self‐assembled structures can be understood and controlled. The kinetics of streptavidin‐functionalized quantum dots binding to biontinylated DNA origami are quantitatively evaluated and to what extent the reaction rate and binding efficiency are controlled by the valency of the binding location, the biotin linker length, and the organization, and spacing of the binding locations on the DNA is shown. Yield improvement is systematically determined as a function of the valency of the binding locations and as a function of the quantum dot spacing. In addition, the kinetic studies show that the binding rate increases with increasing linker length, but that the yield saturates at the same level for long incubation times. The forward and backward reaction rate coefficients are determined using a nonlinear least squares fit to the measured binding kinetics, providing considerable physical insight into the factors governing this type of self‐assembly process. It is found that the value of the dissociation constant, K_d, for the DNA–nanoparticle complex considered here is up to seven orders of magnitude larger than that of the native biotin–streptavidin complex. This difference is attributed to the combined effect that the much larger size of the DNA origami and the quantum dot have on the translational and rotational diffusion constants.