This PDF file contains the front matter associated with SPIE Proceedings Volume 11086, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Due to its high sensitivity and selectivity, UV resonance Raman (UVRR) spectroscopy has a number of scientific and industrial applications. Deep UVRR excited within explosive absorption bands (200 – 230 nm) enables trace explosive detection at a distance due to the resonance enhancement of Raman band intensities, stronger light scattering at short wavelengths, as well as negligible florescence interference. We are developing deep UVRR detection methodologies by investigating resonance enhancement of explosives excited in the deep UV, determining the optimal excitation wavelengths, investigating explosive UV-photochemistry, characterizing explosive UV photoproducts, and measuring UVRR spectral evolution during explosive photolysis. We are also developing state-of-the-art UVRR instrumentation by designing and manufacturing high efficiency, high throughput standoff UVRR spectrometers, co-developing new compact solid state deep UV lasers, and designing novel deep UV optical diffracting devices.

Electronic states of graphene have received much interest for the last two decades or so. The interesting properties of graphene are strongly concerned with its specific electronic structure containing conjugated π system. Therefore, an extensive amount of information about graphene has been collected with significant contributions from theoretical and computational investigations.　We measured the electronic spectra of graphene nanostructures (flakes and platelets) extending into the far-ultraviolet (FUV) region by attenuated total reflection far- and deep-ultraviolet (ATR−FUV−DUV) spectroscopy in the region of 2.76−8.55 eV (450−145 nm). Besides a major absorption of graphene appearing in the DUV region (4.7 eV), we observed a new peak in the FUV region, visible clearly in the case of flakes at 7.5−7.7 eV (165−161 nm) and less pronounced in the spectrum of the platelets at 6.6−6.7 eV (188−185 nm). Quantum chemical calculations were applied to several molecular models incorporating the expected principal structural features of graphene nanostructures. On the basis of the results of time-dependent density functional theory and Zerner’s intermediate neglect of differential overlap (ZINDO) calculations, it was possible to consistently reproduce the experimental spectral variations in terms of both band positions and intensities. The spectral differences result from the differences in the die area, ordering and the number of layers, and structural factors which separate nanoflakes and nanoplatelets. These results provide insights into the probable origins of the spectral variability of graphene nanostructures as well as the molecular orbitals involved in a FUV π−π* transition of graphene nanostructures.

Recently, ionic liquids faced on electrodes have been intensively studied because they have been expected as novel electrolytes having high safety and functions. In this study, we constructed an attenuated total reflectance spectroscopic system which worked under electrochemical environments, and investigated electronic states of the ionic liquids near the electrode surface. In accordance with an applied voltage, electronic transition spectra in 150-450 nm range of an ionic liquid consisted of imidazolium cation and iodine anion varied. In particular, absorption due to a charge transfer from the anion to the cation drastically increased at positive potentials. The amount of spectral change and the contact area between the electrode and the ionic liquid were in a positive relationship, and thus, the spectral variations reflected the behavior of the interfacial ionic liquid on the electrode. Time dependence and hysteresis were also discussed. The newly developed system will be applied not only for the ionic liquids but also for various electrochemical materials such as organic semiconductors.

Deep-UV Raman spectroscopy is a promising method for the analysis of nitrates and nitrites in water at ppm (mg/l) concentrations. In addition to the high sensitivity, the tunability of the laser source allows to deeper investigate the photoinduced reactions taking place under deep-UV illumination. Under these conditions, nitrate ions decompose into oxygen and nitrite through different reaction pathways. Analysis of the evolution of nitrate and nitrite Raman modes as a function of the excitation wavelength allows for estimating the photo-energy dependent quantum yield of the photolysis process. The results highlight the limits and capabilities of deep UV Raman as a on-line nitrate and nitrite monitoring method.

There is a growing interest in UV plasmonics due to its potential applications in biomedical field. Native fluorescent of biomolecules reside in the ultraviolet range of the spectrum. However, small quantum yield and poor photo-stability are hindering the development of biosensors based on native fluorescence. UV plasmonics have been shown to improve the quantum yield and photo-stability of biomolecules. In this talk, I will discuss our efforts in studies of UV plasmonic material and nanostructure geometries to engineer the fluorescent properties of biomolecules. UV resonant enhanced Raman holds promise in label free probing of molecule structures. In this talk, I will discuss using resonant enhanced Raman spectroscopy for detecting biomolecules. I will also discuss our efforts in exploring active UV plasmonic material that can enable multiplexed biosensing.

Despite of increasing understandings of UV plasmonic materials, materials that can enable active tuning of UV plasmonic resonance has not been reported. Here, we demonstrate a modification of UV SPR on an aluminum (Al) hole-array by coupling Graphene π plasmon resonance with Al SPR. Graphene monolayer exhibits an abnormal absorption peak in the UV region (270-290nm) due to π plasmon resonance. The location and intensity of the absorption peak depend on the position of Fermi-level, which can be adjusted by electric or chemical doping. Al SPR is shown here to be modified by coupling Graphene π plasmon resonance with Al SPR. FDTD simulation shows the modification of Al hole-array transmission by adding a single layer of Graphene on top. The shifts of transmission dips after adding a Graphene layer shows a distinct transition at around the Graphene π plasmon position. For transmission dips that are located at shorter wavelength compared to Graphene π plasmon, up to 8nm blue shifts occur after adding Graphene. On the other hand, up to 20nm redshifts occur for transmission dips that are at a longer wavelength relative to Graphene π plasmon. This change in the sign of shifts of transmission dips corresponds to the change in the sign of the real permittivity of Graphene. The amount of shifts diminishes as the transmission dip moves further away from Graphene π plasmon resonance into the visible spectrum. Experimentally we have observed redshifts of SPR dips but not blue shifts possibly due to the poor light collection below 250nm.

We report the current progress of our development of near-ultraviolet (NUV) III-nitride vertical-cavity LED emitters and avalanche photodetectors grown by metalorganic chemical vapor deposition (MOCVD). The III-N emitters are designed to be UV vertical-cavity surface-emitting lasers operating at 369.5nm. We describe the development of the growth and processing of an air-gap/AlGaN distributed Bragg reflector (DBR) consisting of five-pairs of quarter-wavelength layers of Al_0.12Ga_0.88N and air-gap regions created by selective chemical etching. A 4-6λ cavity was employed in the laser structure. We also report on the electrical and optical emission characteristics of these microcavity emitters. The photodetectors are GaN- and AlGaN-based p-i-n avalanche photodiodes (APDs) designed for front-side illumination. We report on the electrical and optical detection characteristics of these photodetectors.

Plasmonic phenomena have greatly contributed to nanooptics and nanophotonics owing to their features such as light localization and high sensitivity to the surrounding environment. The nanoparticles of poor metals (e.g. Al) exhibit plasmonic properties in the UV range (240-350 nm) where many organic molecules and semiconductors absorb light, which was recently confirmed and utilized in enhanced Raman spectroscopy and UV photocatalysis. The present study demonstrates the efficient TiO2 photocatalysis with indium nanostructures resonant in the near-UV range. Indium (In) nanograins were densely distributed on a TiO2 thin film, where methylene blue (MB) was applied to test the photocatalytic activity. The photocatalytic reaction was initiated by irradiating the samples with UV light, and the time-dependent decay of the MB absorbance was observed. A reaction rate was found to increase by factors as high as 7 while the enhancement of photocatalysis shows particle size dependence. The increase and downward trend in the enhancement shows a good agreement with that in the field intensity simulated by the discrete dipole approximation (DDA). Simulation results also suggest that the largest enhancement of photocatalysis be obtained with In nanograins whose resonance is close to the bandgap of TiO2. It is expected that the light at the absorption edge wavelength confined at plasmonic nanostructures effectively for the photocatalytic reaction.

Photolithographic techniques capable of producing sub-micron scale features typically involve laser or electron beam sources and chemical development of an exposed photoresist. We report here a novel, low cost photolithographic process utilizing flat, efficient lamps emitting at 172 nm. Recently developed 10 cm x 10 cm lamps, for example, produce more than 25 W of average power at 172 nm which enables the precise and fast patterning of most polymers, including those normally employed as e-beam resists and photoresists. Recent experiments demonstrate that PMMA films less than 100 nm in thickness are patterned in less than 20 s through a contact mask with high contrast resolution of 500 nm features. The ultimate resolution limit is expected to be ≤ 300 nm for a contact method. Electroplating technique was further used to deposit 500 nm gold features on a silicon substrate. The reported process does not require a photoresist development step and is performed in nitrogen atmosphere at atmospheric pressure which make it fast and affordable for fabrication facilities that have no access to high-tech photolithography equipment. Samples as large as 76 mm (3”) in diameter may be exposed with a single lamp in one step and areas of 1 m2 and above may be processed with tiled arrays of lamps. Patterning of bulk polymers (acrylic sheets, for example) through a photomask and subsequent formation of sub-micron features has also been demonstrated.

UV Resonance Raman (UVRR) scattering offers several advantages with respect to spontaneous Raman one, such as the significant increment of the detection limit and the selectivity needed to incisively monitor specific chromospheres within the sample. Here we present a synchrotron-based Resonance Raman instrument that exploits the wide and continuously tunable UV emission provided by the synchrotron source. As an example, we discuss the solvation dynamics of two model peptides, N-acetyl-leucine-methylamide (NALMA) and N-acetyl-glycine-methylamide (NAGMA), by putting in evidence on the advantages of the use of SR-based UVRR. The experimental results evidence that the fine tuning of the excitation wavelength allows to choose the best working conditions that ensure to reliably detect the spectral changes of the amide signals, as function of concentration and temperature of peptide. The analysis of the spectra provides new insights on the hydrogen-bond interactions at the peptides backbone.

Far-ultraviolet (FUV) spectroscopy holds great potential in revealing electronic transitions and structure of a wide range of molecules in condensed phases. FUV spectroscopy in the 145-200 nm regions has recently been a matter of intense interest because many kinds of organic and inorganic materials in the condensed phase show bands coming from electronic transitions in the FUV region. Since the molar absorption coefficient is very high (~105 mol-1 dm3 cm-1) in the FUV region, the electronic states and structure mainly for gas molecules has been investigated for a long time. On the other hand, as to molecules in the condensed phase transmittance spectra could not measure because of high molecular density, and reflection spectroscopy has been used to observe spectra of solid samples in the FUV region. Accordingly, electronic spectroscopy for molecules of sigma orbital has been a relatively undeveloped research area. To solve the above difficulties of FUV spectroscopy we have recently developed a totally new UV spectrometer based on attenuated total reflection (ATR) that enables us to measure spectra of liquid and solid samples in the 140–300 nm region. Liquid n- and branched alkanes were studied using ATR-FUV. FUV spectra of these molecules can be explained by quantum chemical calculation and almost similar to those in the gas phase. However, FUV spectra of solid alkanes show drastic alternations from those in the liquid phase. Changes in the orbital of alkanes in the solid phase were related to abnormal phase behavior of these molecules

In this study, we notice on Alkali metal complex. They are composites from alkali metal salt and ether molecules. These complexes are very fascinate materials because they are one of the functional material. They have ion transportation ability and low vapor pressure etc. Many researches were reported, for example, Li+/Glyme　as solvation ionic liquid and Li+/PEG as solid or gel electrolyte for Li+　ion batteries. They form complex between oxygen atom and Li+. However, electronic states about the complex which should reflect strength of coordinate bonding in them did not get clear　in detail. We have investigated about changes in electronic transitions of these composite from PEG and Li by forming complex.　Using Attenuated total reflectance spectroscopic in Far Ultra-violet region (ATR-FUV), electronic transitions in 140-200nm (FUV) can be observed easily. Electronic states of PEG were already studied by ATR-FUV. PEGs have 3 transitions about n – Rydberg transitions, 153nm, 163nm and 175nm were assigned to n (OH) – 3p Ryd, n (COC) – 3p and n (COC) – 3s Ryd respectively3. In this study, PEG and Lithium Bis (trifluoromethane sulfonyl) imide (LiTFSI) were investigated in wide range of concentration and also used various samples, for example cations (Li+, Na+, K+) and anions (BF4, PF6, NO3-, and trifluoromethane sulfonyl family etc.). Furthermore, simulation spectra from quantum calculation spectra by time dependent-density　function theory (TD-DFT, cam-b3lyp/6-311++g (2d, p)) were investigated. Experimental　and calculation results were compared to discuss changes in electronic states and these result.

Although Deoxyribonucleic acid (DNA) is considered substantially stable in aqueous solution, slow hydrolysis can damage its double-helix structure and cause denaturation when it is stored for several months. Therefore, the design of aqueous solvents that are able to stabilize and maintain DNA conformation is a challenging issue. Ionic liquids (ILs) appear as ideal water co-solvents for DNA biotechnology due to their unique properties. We have investigated the thermal stability of DNA in 1-butyl-3-methylimidazolium aqueous solutions by synchrotron-based UV Resonance Raman (UVRR) spectroscopy with the aim to clarify the role played by concentration of IL in stabilizing the DNA natural conformation. The synchrotron-based UV source for UVRR measurements allows us to enhance specific vibrational signals associated to nitrogenous bases of DNA, through an appropriate tuning of the excitation wavelength. Such approach permits to probe the rearrangements in the local environment around specific nucleotides as a function of thermal conditions.

In extreme ultraviolet laser ablation MSI, bright laser pulses from a compact 46.9-nm-wavelength laser [1] are focused into nanometer size spots to ablate craters a few nanometers deep on selected regions of the sample. Elemental and molecular ions in the laser-created plasma are extracted and identified by their mass-to-charge ratio (m/z) using a time-of-flight mass spectrometer. Analysis of the spatially resolved mass spectra obtained as the sample is displaced with respect to the focused laser beam enables one to construct 3-D composition images with nanoscale resolution [2]. In this talk I will describe recent advances of extreme ultraviolet MSI that show its unique capabilities to identify low concentration of high Z elements into glass matrices, and to map molecular composition of single micro-organisms in 3-D at the nanoscale. [1] S. Heinbuch et al, "Demonstration of a desk-top size high repetition rate soft x-ray laser," Opt. Express vol. 13, 4050-4055 (2005). [2] I. Kuznetsov et al, "Three dimensional nanoscale molecular imaging by extreme ultraviolet laser ablation mass spectrometry, " Nature Communications, vol. 6, Article No. 6944(2015)..

As the modern technology becomes increasingly nanoscale, microscopy and metrology methods relying on visible and UV wavelengths can no longer fully satisfy scientific and industrial needs. Reduction of the working wavelength to the extreme ultraviolet (EUV, 5 to 50 nm) region is a promising way to extend the applicability of optical techniques to cutting-edge nanotechnology. Short wavelengths and efficient interaction of EUV radiation with matter provides spatial and depth resolution on the nanoscale, which enables not only ultra-high-resolution lithography, but also microscopy, high-precision thin film analysis and dimensional metrology of nanostructures. The presentation is focusing on laboratory-based applications of EUV radiation enabled by compact plasma-based EUV radiation sources. The topics of nanoscale imaging, defect detection, thin film analysis and critical dimensions metrology will be discussed. The developed laboratory tools, such as multi-angle spectroscopic EUV reflectometer and EUV dark-field microscope, will be presented together with latest obtained experimental results. Thin film analysis with sub-nm precision will be demonstrated and benchmarked against state-of-the-art X-ray reflectometry. Specific modelling challenges in the EUV region will be outlined and possible solutions and opportunities will be presented. At the end general limits of applicability of the EUV radiation for industrial and scientific metrology will be discussed together with an outlook to potential perspectives of the EUV-based optical metrology.

The scanning electron microscope (SEM) has become the major imaging technique of choice over many fields of science, providing resolution down to a few nanometers. To reduce surface charging, low beam currents and a few-nm-thick highly conductive metal (Au, Pt) coatings are used. The conceptual problem with the metal coating is that it conceals the sample features which it aims to reveal and the characterised samples are altered. A novel approach to control surface charging in SEM via the photoelectric effect is shown. The technique uses deep-UV co-illumination during SEM imaging. Photons of the deep-UV light have sufficient energy to liberate electrons from the sample surface reducing strong charge gradients. In addition, the method provides a new material dependent contrast modality in SEM. Deep-UV illumination also improves nanoscale 3D structuring using focused ion beam milling. Instead of the metal coating for electron/ion imaging, the newly introduced “coating by light” is introduced. Load-lock mountable sample holder with a deep-UV multiwavelength illumination is conceptualised.

Wide-band gap semiconductor nanoparticles has been the focus of interest recently, due to their validity for energy creations, decomposition of harmful substances, boosting useful chemical reactions etc. In this work, we will evaluate optical characteristics of a single semiconductor nanoparticle via broadband-UV Rayleigh scattering spectroscopy and photoluminescence (PL) spectroscopy. Rayleigh scattering spectroscopy reveal the bandgap energies while PL spectroscopy provide the information on exciton generation efficiencies as well as existence of surface defects. In our microscopy setup, a broadband white light source (LDLS) was collimated and obliquely illuminated on the sample to realize dark-field illumination to distinguish the position of individual particles in the microscopic image. Scattering from a single nanocrystal was collected by an reflection-type objective lens (NA0.5) and introduced to a spectrometer and detected by an EMCCD camera. The spectrometer was designed specifically for UV-DUV broadband spectroscopy and imaging. For photoluminescence (PL) measurements, we introduce 320 nm (CW) laser for excitation. The sample is enclosed in a temperature-controlled cell ranging from room temperature to 77K. We especially focus on titanium dioxide (TiO2), a typical photocatalyst, and tangusten trioxide (WO3) which is one of the candidate for decomposition of water into oxygen and hydrogen by a visible or longer wavelength light. The band structure of nano-particles is changed when the size is smaller than several tens of nanometers, due to crystallinity and quantum size effects. PL of single zinc oxide (ZnO) nanoparticles were also measured together with the temperature effects. The spectra obtained from a single nanoparticle is different from aggregates both for exciton PL and defects PL.

Recently, several alternative materials and geometries, including multiphase core-shell nanostructures also coupled to semiconducting plasmonic materials and emerging 2D materials have arisen as interesting plasmonic competitors to noble metals, such as gold and silver. The interest is driven by the attempts to implement the plasmonic functionality with additional functions of phase change, active plasmonics, photocatalysis, etc. Several advantages have been found for nanostructures based on Ga, such as wide tunability of the resonance energy from the ultraviolet (UV) to infrared (IR) spectral region, simplicity of the preparation methods, high sensitivity to the polarization of incident light. This contribution will provide an insight into the preparation, modelling and applications tailored by the control of interplay between light and chemistry in interface phenomena of multiphase (core-shell and nanoalloys) plasmonic nanostructures based on Ga, Mg, Al, Rh, coupled to a variety of materials including dielectric oxides, semiconductors, organic/plastic materials and graphene. A critical assessment of advantages and disadvantages, considering the system reactivity and stability, of various plasmonic nanostructures will be given, focusing mainly on the UV spectral region. Implications of the interface reactivity of core-shell structure and nanoalloys based on Ga, Mg, Al, Ag, Pd, and Pt on the potential exploitation in phase change photonics, UV photocatalysis and hydrogen storage will be discussed.

A sensitive 1D single crystal ZnO nanostructure gas sensor decorated with Pt nanoparticles was prepared to detect low concentrations of toxic gases at room temperature under UV-LED irradiation. The developed UV-LED activated sensors have a variety of advantages, compared to the traditional high temperature chemi-resistive metal oxide semiconductor (MOS) sensors, such as higher stability, smaller size, lower preparation time, and the ability to safely detect flammable gases. The developed sensing materials were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analyses. To obtain a visual evidence of Pt nanoparticles on the surface of ZnO nanowires, high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field (HAADF) STEM were employed. The gas sensing results indicated a significant increase (an order of magnitude) in sensor response toward NO2 as a model gas, compared to pristine ZnO sample mainly due to charge carrier enhancement. The effect of UV irradiance was found to play an important role with respect to the sensor response and detection speed.

The combination of resonance Raman with deep UV excitation, DUVRR, gives greater selectivity and eliminates background fluorescence, enabling sensitive detection of UV absorbing nucleotide bases and amino acids. We demonstrate this combination with our 3D nanopore structure design. Resonance Raman is specific to a molecule absorbing at the excitation, while plasmon resonance of a small, shape-, index- and size- tuned metal dramatically increases the electric field strength in the active region. The 3D nanostructure exploits nanopores that retain the advantages of small-gap antennas but increases the ease of fabrication, availability, and detection volume compared to conventional plasmon-based designs, such as gaps between two particles, by being inherently single particle, with edge enhancement open to diffusion, and by possessing a large number of pores per particle. We show the large local field enhancement (hot spots) of the pores. Comparisons with an Al and silica coated/uncoated microsphere template with/without nanopores clearly show a significant blue shift of the 280 nm peak to (the more useful) 265 nm, in the presence of a hollow sphere with nanopores. Raman measurement of Tryptophan on an aluminum nanopore structure with excitation from our tunable OPO system in the visible and deep UV region indicate visible excitation causes more fluorescence and is less specific for the tryptophan, even displaying a Raman peak at the silicon substrate, while the deep-UV Raman spectra, at an energy close to the nanopore resonance, shows no substrate signal and peaks with close correlation to the known tryptophan vibrations.