Using extreme ultraviolet interference lithography, we demonstrate patterning of different inorganic photoresists, reaching the highest reported photolithography resolution of 7 nm half-pitch.
Surface plasmon resonance (SPR) was observed when a planar close-packed assembly of gold nanoparticles (Au NPs) is adsorbed at the water|1,2-dichloroethane interface. Aqueous gold nanoparticles, 13 or 16 nm in diameter, are deposited at the interface by adding methanol to form a close-packed film with a visible gold mirror reflectance. By total internal reflection of a light beam on the interface, the angular dependence of the interfacial reflectivity was measured in a pseudo-Kretschmann configuration and compared to Fresnel simulations for a homogeneous gold film. The experimental angles for minimum reflectivity were found to match the simulated values. Then, the fluorescence of dye molecules co-adsorbed within 13 and 16 nm gold nanoparticles assemblies at the liquid|liquid interface was measured. The fluorescence intensity under SPR is revealed to be much greater than under total internal reflection conditions, yielding an enhancement factor of approximately 30 and 50 for 13 and 16 nm Au NPs assemblies, respectively. Also, the fluorescence lifetime was found to decrease under SPR conditions.
H2 may be evolved biphasically using a polarised liquid|liquid interface, acting as a "proton pump", in combination with organic soluble metallocenes as electron donors. Sustainable H2 production requires methodologies to recycle the oxidised donor. Herein, the photo-recycling of decamethylferrocenium cations (DcMFc+ ) using aqueous core-shell semiconductor CdSe@CdS nanoparticles is presented. Negative polarisation of the liquid|liquid interface is required to extract DcMFc+ to the aqueous phase. This facilitates the efficient capture of electrons by DcMFc+ on the surface of the photo-excited CdSe@CdS nanoparticles, with hydrophobic DcMFc subsequently partitioning back to the organic phase and resetting the system. TiO2 (P25) and CdSe semiconductor nanoparticles failed to recycle DcMFc+ due to their lower conduction band energy levels. During photo-recycling, CdS (on CdSe) may be self-oxidised and photo-corrode, instead of water acting as the hole scavenger.
Self-assembly in the bulk of a series of hybrid triblock copolymers formed by a poly(9,9-dihexylfluorene-2,7-diyl) (PHF) middle block and two poly(γ-benzyl-l-glutamate) (PBLG) end blocks has been studied. Since the α-helical secondary structure of the PBLG block may be either maintained or suppressed depending on the solvent casting history, the PBLG−PHF−PBLG copolymers exhibit two different conformations: a rod−rod−rod or coil−rod−coil configuration, respectively. In order to provide insight into the influence of conformation on self-aggregation of these systems, three copolymers with different block ratio were investigated in both conformations using small- and wide-angle scattering techniques and transmission electron microscopy. Time-resolved photoluminescence measurements were performed on the same samples to explore the effect of morphology on photophysical properties. The observed photoluminescence spectra and dominant excited lifetimes of the poly(9,9-dihexylfluorene-2,7-diyl) block were found to differ markedly in rod−rod−rod and coil−rod−coil configurations and were correlated to the morphology of the self-assembled triblock copolymers.
Capacitance measurements of a polarised liquid|liquid interface show that the capacitance of the interface increases in the presence of an adsorbed monolayer of citrate-coated gold nanoparticles. This unusual observation can be explained by an increase of the interfacial charge density or by an increase of the interfacial corrugation. This study shows that capacitance measurements provide a method to monitor metallic film formation at ITIES.
We present fabrication and characterization of high-resolution and nearly amorphous Mo1 − xNx transmission gratings and their use as masks for extreme ultraviolet (EUV) interference lithography. During sputter deposition of Mo, nitrogen is incorporated into the film by addition of N2 to the Ar sputter gas, leading to suppression of Mo grain growth and resulting in smooth and homogeneous thin films with a negligible grain size. The obtained Mo0.8N0.2 thin films, as determined by x-ray photoelectron spectroscopy, are characterized to be nearly amorphous using x-ray diffraction. We demonstrate a greatly reduced Mo0.8N0.2 grating line edge roughness compared with pure Mo grating structures after e-beam lithography and plasma dry etching. The amorphous Mo0.8N0.2 thin films retain, to a large extent, the benefits of Mo as a phase grating material for EUV wavelengths, providing great advantages for fabrication of highly efficient diffraction gratings with extremely low roughness. Using these grating masks, well-resolved dense lines down to 8 nm half-pitch are fabricated with EUV interference lithography.
The authors demonstrate generation of high-resolution nanostructures using achromatic spatial frequency multiplication in the extreme ultraviolet wavelength region. The technique based on the achromatic Talbot effect is used for periodic transmission gratings under wideband illumination, enabling one- and two-dimensional nanopatterns with sub-20 nm feature sizes. The transmission masks with desired properties are fabricated with electron-beam lithography followed by electroplating of gold. Features sizes down to 12 nm are obtained. The presented technique provides high-throughput and large-area nanopatterning with great flexibility in tuning pattern parameters such as linewidth and dot size.
Circular dichroism in optical second harmonic generation (CD-SHG) is studied in planar symmetrical arrays of G-shaped and mirror-G-shaped nanostructures. Anisotropic CD-SHG measurements demonstrate a strong dependence of the value and the sign of the CD effect on the angle of incidence of the fundamental radiation. We show that both dipole and higher order multipole components of the second order susceptibility are responsible for the CD response from G-shaped nanostructures.
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