Sub-100 nm Feature Definition Optimization using Cold Cs Beam Exposed Self-Assembled Monolayers on Au

The results of a study into the dependency of SAM coverage, subsequent post-etch pattern definition and minimum feature size on the quality of the Au substrate used in both physical mask and optical mask atomic nanolithographic experiments are presented in this paper. In comparison, sputtered Au substrates yield much smoother surfaces and a higher density of {111} oriented grains than evaporated Au surfaces. Phase imaging with an atomic force microscope shows that the quality and percentage coverage of uniform alkanethiol monolayer adsorption was much greater for sputtered Au surfaces. Exposure of the monolayer with a laser-cooled Cs beam allowed determination of the minimum Cs dose (2 monolayers) to expose the SAM with lateral force microscopy. Suitable wet-etching, with etch rates of 2.2 nm min-1, results in optimized pattern definition. Utilizing these optimizations, features as small as 50 nm were achieved using both a sub-100 nm physical mask and optical standing wave mask

Adsorption of alkanethiol self-assembled monolayers on sputtered gold substrates for atomic nanolithography applications

A detailed study of the self-assembly and coverage by 1-nonanethiol of sputtered Au surfaces using molecular resolution atomic force microscopy (AFM) and scanning tunneling microscopy (STM) is presented. The monolayer self-assembles on a smooth Au surface composed predominantly of {111} oriented grains. The domains of the alkanethiol monolayer are observed with sizes typically of 5-25 nm, and multiple molecular domains can exist within one Au grain. STM imaging shows that the (4 × 2) superlattice structure is observed as a (3 × 2√3) structure when imaged under noncontact AFM conditions. The 1-nonanethiol molecules reside in the threefold hollow sites of the Au{111} lattice and aligned along its [112] lattice vectors. The self-assembled monolayer (SAM) contains many nonuniformities such as pinholes, domain boundaries, and monatomic depressions which are present in the Au surface prior to SAM adsorption. The detailed observations demonstrate limitations to the application of 1-nonanethiol as a resist in atomic nanolithography experiments to feature sizes of ~20 nm

Color-coded batteries – electro-photonic inverse opal materials for enhanced electrochemical energy storage and optically encoded diagnostics

For consumer electronic devices, long-life, stable, and reasonably fast charging Li-ion batteries with good stable capacities are a necessity. For exciting and important advances in the materials that drive innovations in electrochemical energy storage (EES), modular thin-film solar cells, and wearable, flexible technology of the future, real-time analysis and indication of battery performance and health is crucial. Here, developments in color-coded assessment of battery material performance and diagnostics are described, and a vision for using electro-photonic inverse opal materials and all-optical probes to assess, characterize, and monitor the processes non-destructively in real time are outlined. By structuring any cathode or anode material in the form of a photonic crystal or as a 3D macroporous inverse opal, color-coded “chameleon” battery-strip electrodes may provide an amenable way to distinguish the type of process, the voltage, material and chemical phase changes, remaining capacity, cycle health, and state of charge or discharge of either existing or new materials in Li-ion or emerging alternative battery types, simply by monitoring its color change

STM observation of sulfur dimerization in alkanethiol self-assembled monolayers on Au{111}

We present for the first time, direct microscopical observation by STM of sulfur dimer formation on alkanethiol self-assembled monolayers (SAM) on sputtered Au substrates. The sulfur dimers are observed when imaging at a bias where the tip-molecule interaction occurs, and are formed by displacement of sulfur atoms from their normal three-fold hollow site residence of the (4 × 2) superlattice to nearest-neighbor bridge-site residence between two Au atoms. The displacement is believed to occur due to defects induced in the alkyl chain of the monolayer due to the proximity of the STM tip. Only one of the sulfur atoms forming the dimer is bound to the surface and they are commensurate with the Au{111} adlattice along its [112] directions

Solution processable metal oxide thin film deposition and material growth for electronic and photonic devices

A comprehensive review of recent advances in solution processing and growth of metal-oxide thin films for electronic and photonic devices is presented, with specific focus on precise solution-based technological coatings for electronics and optics, and new concepts for oxide material growth for electrochemical, catalytic, energy storage and conversion systems, information technology, semiconductor device processing and related devices. Throughout, the nature of the soluble precursors solutions and their relationship to film formation process by various solution coating techniques are collated and compared, highlighting advantages in precursor design for creating complex oxides for devices. Because of the versatility of solution-processable oxides and functional material coating, it is important to capture the advances made in oxide deposition for plastic electronics, see-through and wearable devices, and high-fidelity thin film transistors on curved or flexible displays. Solution processing, even for oxides, allows control over composition, thickness, optical constants, porosity, doping, tunable optical absorbance/transmission, band structure engineering, 3D-substrate coating, complex composite oxide formation and multi-layered oxide systems that are more difficult to achieve using chemical vapor deposition (CVD) or atomic layer deposition (ALD) processes. We also discuss limitations of solution processing for some technologies and comment on the future of solution-based processing of metal-oxide materials for electronics, photonics and other technologies

Effect of annealing on the development of fully transparent ternary V-O-Na-Si mixed metal oxide thin films from polymer-assisted dip-coated V2O5

Both transparent oxides and transparent conductive oxides are of particular research interest for future applications in flexible, optically transparent thin film transistors and luminescent devices. We report the formation of a transparent oxide material based on the interdiffusion of Na-O and Si-O species with dip-coated V2O5 thin films on a borosilicate glass substrate. The deposition process used a facile solution processed dip-coating technique in the high-rate draining regime. Liquid precursors of vanadium alkoxide and alkoxide-polyethylene glycol mixtures were used for thin film deposition. We examine the effect of annealing condition on the phase conversion process, morphology and optical transmittance due to the conversion of the V2O5 films to completely transparent ternary mixed metal oxide thin films. The work also examines the role of polymer-assisted deposition on the development of the V-O-Na-Si transparent thin films during different annealing conditions. Polymer-assisted V2O5 thin films on glass are shown to convert to optically clear thin films during annealing, with a transparency >95% across the visible spectrum, and a blue-shift of the absorption edge to maintain >90% transparency at 380 nm

Electrochemical investigation of the role of MnO2 nanorod catalysts in water containing and anhydrous electrolytes for Li-O2 battery applications

The electrochemical behaviour of MnO2 nanorod and Super P carbon based Li-O2 battery cathodes in water-containing sulfolane and anhydrous DMSO electrolytes are shown to be linked to specific discharge product formation. During discharge, large layered spherical agglomerates of LiOH were characteristically formed on the MnO2 cathodes while smaller, toroidal, spherical Li2O2 particles and films were formed on the Super P cathodes. In an anhydrous DMSO based electrolyte the LiOH structures were also found on cathodes discharged in the anhydrous electrolyte, suggesting that MnO2 initiates electrochemical decomposition of the DMSO electrolyte to form LiOH via H2O reactions with Li2O2. The LiOH crystals are uniquely formed on MnO2, and segregated to this phase even in mixed oxide-carbon cathodes. In contrast, no Li2O2 toroids were noted on Super P cathodes discharged in the DMSO based electrolytes. Instead, the morphology varied from smaller sheets (at high discharge current) to much larger agglomerates (at low discharge currents). In mixed carbon-MnO2 nanorod cathodes, the use of PVDF initiates H2O formation that affects discharge products and an overall mechanism governing phase formation at MnO2 in sulfolane and anhydrous DMSO with and without PVDF binder is presented. This work highlights the importance of careful consideration of electrolyte-cathode material-discharge product interactions in the search for more stable Li-O2 systems

Examining the role of electrolyte and binders in determining discharge product morphology and cycling performance of carbon cathodes in Li-O2 Batteries

In this report we examine the influence of electrode binder and electrolyte solvent on the electrochemical response of carbon based Li-O2 battery cathodes. Much higher discharge capacities were noted for cathodes discharged in DMSO compared to TEGDME. The increased capacities were related to the large spherical discharge products formed in DMSO. Characteristic toroids which have been noted in TEGDME electrolytes previously were not observed due to the low water content of the electrolyte. Linear voltage sweeps were used to investigate ORR in both of the solvents for each of the binder systems (PVDF, PVP, PEO and PTFE) and related to the Li2O2 formed on the cathode surfaces. Galvanostatic tests were also conducted in air as a comparison with the pure O2 environment typically used for Li-O2 battery testing. Interestingly, tests for the two electrolytes showed opposite trends in terms of discharge capacity values with capacities increased in TEGDME (compared to those seen in O2) and decreased in DMSO. The report highlights the key roles of electrolyte and cathode composition in determining the stability of Li-O2 batteries and highlights the importance of identifying more stable electrolyte/cathode pairings