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The design, fabrication, and characterization of a low profile shear-force sensor for gait analysis is presented. An analytical model is used to estimate the behavior of the sensor. The sensor response is linear within the modeled range and has a predicted sensitivity of 0.012 pF/N, which is confirmed using a 3D FEM model of the electrical properties of the sensor. The capacitive sensor has a measured sensitivity of 0.0006 pF/N ( ${x}$ -axis) and 0.0003 pF/N ( ${y}$ -axis). When considering the readout electronics, this translates to a voltage/force sensitivity of 9.8 mV/N ( ${x}$ -axis) and 5.2 mV/N ( ${y}$ -axis). The range of the sensor was found to be more than 24 N. The 3D printed sensor is cylindrical with a footprint of ~3 cm2 and a height of just 3.6 mm, making it suitable for in-sole shear-force measurements.

A position sensing glove, called SmartScan, that creates a 3D virtual model of a real object is presented. The data from the glove is processed by a volume minimization algorithm to validate the position sensor data. This allows only data from the object’s surface to be retained. The data validation algorithm allows the user to progressively improve an image by repeatedly moving their hand over the object. In addition, the user can choose their own balance between feature resolution and invalid data rejection. The SmartScan glove is tested on a foot model and is shown to be robust against motion artifacts, and has a mean accuracy of 2.9 mm (compared to a 3D model generated from optical imaging) without calibration.

In this work, a technique for hydrogen diffusion measurements through thin films is proposed and demonstrated. A yttrium film, which changes its refractive index upon hydrogen absorption, is used as an optical sensor to detect hydrogen. The yttrium sensor is coated with a thin (up to 12 nm) layer of test material and exposed to atomic hydrogen. To ensure that the calculated diffusion constant is not artificially changed by surfaces processes, the test layer is coated with palladium. Hydrogen diffusion through test layers of Si, Al, Ag, Ru, Mo, Al2O3 and SiO2 were measured and compared with existing data. The hydrogenation time (time to form YH2) was found to exponentially scale with the enthalpy of hydrogen solution in the test material. Comparison between measured diffusion coefficients for different film thicknesses, as well as previously reported results, highlights the strong dependence of the diffusion constant on sample fabrication conditions, and hydrogen exposure conditions. It is concluded that diffusion through thin films can be reliably compared only when specimen form and exposure conditions are the same. The relevance of this study for applications is discussed.

In this work we expose transferred multi-layer graphene (i.e. graphene separated from the substrate used for graphene growth and placed onto a carrier sample) to Extreme Ultraviolet light and water, in the presence of hydrogen. It is observed that graphene oxidizes by breaking down its aromatic structure into the enol form of 1,3-diketone. Furthermore, this oxidation is compared with studies on as-grown multi-layer graphene samples, which are shown to not oxidize. Our work shows that oxidation is most likely limited to a few layers of graphene at the interface between the graphene and the substrate onto which it is transferred. This is attributed to the presence of water, trapped during the transfer process, which is dissociated by secondary electrons from the substrate.

Yttrium is known to form two hydrides: YH2, a metal, and YH3, which is dielectric. However, the stability of YH3 is not fully understood, especially in the context of thin films, where the yttrium layer must be coated to protect it from oxidation. In this work, we show that the stability of a YH3 thin film depends on the capping layer material. Our investigation reveals that YH3 appears to be stabilized by hydrogen that is adsorbed to the capping layer surface. This is evidenced by the YH3-YH2 transition temperature, which was found to be correlated with the desorption temperature of hydrogen from the surface. We posit that surface-adsorbed hydrogen prevents hydrogen from diffusing out of the thin film, which limits YH3 dissociation to the solubility of hydrogen in the YH2/YH3 thin film.

In this work, we study the reaction of the dissociation products of carbon dioxide on a Ru(0 0 0 1) surface under Extreme Ultraviolet (EUV) light with a partial pressure of hydrogen. Our results show that both amorphous carbon and H2O are the end products of the CO2 dissociation at the Ru surface, and these are produced only in the presence EUV and H2. Partial dissociation of CO2 on the Ru surface is an intermediate step in the overall reaction. Using Reflection Absorption Infrared spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD), only water is detected as molecular reaction product. We further show that this reaction deactivates the Ru surface due to the formation of an amorphous carbon layer, thereby confirming the catalytic role of Ru in the total reaction.

The adsorption and dissociation of carbon dioxide on a Ru(0001) single crystal surface was investigated by reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) spectroscopy for CO2 adsorbed at 85 K. RAIRS spectroscopy shows that the adsorption of CO2 on a Ru(0001) single crystal is partially dissociative, resulting in CO2 and CO. The CO vibrational mode was also observed to split into two distinct modes, indicating two general populations of CO present at the surface. Furthermore, a time-dependent blue-shift is observed, which is characteristic of increasing CO surface coverage. TPD showed that coverages of up to 0.3 ML were obtained, and no evidence for chemisorption of oxygen on ruthenium was found.

The structural changes in Ru-coated Y films during hydrogenation were studied in this work. In situ XRD data were used to show that the Y to YH2 transition requires significant hydrogen loading of the Y lattice. By comparing the XRD data with the in situ spectroscopic ellipsometry data, an effective medium model for the transition was obtained. This model describes the Y to YH2 transition well. The YH2 to YH3 transition is also described by an effective medium model, however, with reduced accuracy around the midpoint of the transition. By comparing the YH2 and YH3 crystal sizes, we show that these deviations may be due to a surface plasmon resonance. The improved understanding of the ellipsometry measurements is important for optical hydrogen sensing applications.

In this work, the authors expose transferred multilayer graphene on a yttrium based hydrogen sensor. Using spectroscopic ellipsometry, they show that graphene, as well as amorphous carbon reference films, reduce diffusion of hydrogen to the underlying Y layer. Graphene and C are both etched due to exposure to atomic H, eventually leading to hydrogenation of the Y to YH2 and YH3. Multilayer graphene, even with defects originating from manufacturing and transfer, showed a higher resistance against atomic H etching compared to amorphous carbon films of a similar thickness.

Background: The secondary electron yield (SEY) of materials is important for topics as nanoparticle photoresists and extreme ultraviolet (EUV) optics contamination. Aim: Experimentally measure SEY and secondary electron energy distributions for Ru, Sn, and Hf oxide. Approach: The SEY and energy distribution resulting from 65 to 112 eV EUV radiation are measured for thin-film oxides or films with native oxide. Results: The total SEY can be explained by EUV absorption in the topmost nanometer of (native) oxide of the investigated materials. Conclusions: Although the relative SEY of Ru and Sn is well-explained by the difference in EUV absorption properties, the SEY of HfO2 is almost a factor 2 higher than expected. Based on the energy distribution of secondary electrons, this may be related to a lower barrier for secondary electron emission.

We demonstrate supercontinuum generation in stoichiometric silicon nitride (Sisub3/subNsub4/subin SiOsub2/sub) integrated optical waveguides, pumped at telecommunication wavelengths. The pump laser is a mode-locked erbium fiber laser at a wavelength of 1.56 µm with a pulse duration of 120 fs. With a waveguide-internal pulse energy of 1.4 nJ and a waveguide with 1.0 µm × 0.9 µm cross section, designed for anomalous dispersion across the 1500 nm telecommunication range, the output spectrum extends from the visible, at around 526 nm, up to the mid-infrared, at least to 2.6 µm, the instrumental limit of our detection. This output spans more than 2.2 octaves (454 THz at the -30 dB level). The measured output spectra agree well with theoretical modeling based on the generalized nonlinear Schrödinger equation. The infrared part of the supercontinuum spectra shifts progressively towards the mid-infrared, well beyond 2.6 µm, by increasing the width of the waveguides.

The RAIRS spectra of water adsorbed on Ru(0001) at 85 K are recorded from 600 cm−1 to 4000 cm−1. Measured at water coverages from 0.13 ML to 2.0 ML, the RAIRS spectra suggest that chemisorption of water on Ru(0001) depends on coverage. Water adsorbs on a clean Ru surface as chemisorbed ice-like clusters (likely through an O–Ru bond) up to 0.33 ML. Above this coverage, the chemisorbed layer saturates. Upon more exposure, water adsorbs as a liquid-like H-bonded layer without bonding to the Ru substrate. The chemisorbed water absorbs 7 times less IR per molecule than the liquid-like structure, which indicates that the orientation of the chemisorbed water is more parallel to the surface. Additionally, the influence of water–Ru bonding on H-bonding is reflected in the OH symmetric stretching mode. Under perturbation from water–Ru bonding, a large red shift (40 cm−1) in the free OH stretching frequency is observed in the chemisorbed clusters. By deconvoluting the main H-bonded OH stretching peak into five Gaussian sub-bands at 2945 ± 5 cm−1, 3210 ± 5 cm−1, 3300 ± 15 cm−1, 3430 ± 5 cm−1 and 3570 ± 10 cm−1, changes in the H-bonding network are rationalized in terms of H-bonding motifs. The donor–acceptor–acceptor motif is significant only in the chemisorbed clusters. On the other hand, the donor–acceptor motif dominates in the liquid-like structure, which increases the disorder present in the adlayer. Although chemisorption is suppressed above 0.33 ML, no structural changes in the ice-like clusters are observed up to multilayer coverage. Therefore, ice-like and liquid-like water coexist in a meta-stable state at 85 K.

A Mo/Si multilayer film may blister under hydrogen exposure. In this paper, we investigate the impact of intrinsic stress on blister formation in multilayers by varying the Si thickness between 3.4-11 nm and changing the hydrogen ion exposure conditions. Increasing the thickness of a-Si is found to introduce a higher average compressive stress in the multilayer film. Measurements of the average film stress before and after hydrogen exposure did not reveal a correlation between stress relaxation and the observation of surface blisters. Comparing the experimentally observed blister size distribution to that predicted by elastic models of blistering due to pressure, and thin film buckling showed that increasing hydrogen pressure under the blister cap is the main cause of the observed blisters. It is also shown that hydrogen diffusion plays an essential role in the blister formation process as sufficient hydrogen is required to pressurize the blister.

The extreme ultraviolet (EUV, λ = 13.5 nm) induced dissociation of water layers on Ru(0001) was investigated. We irradiated amorphous and crystalline water layers on a Ru crystal with EUV light, and measured the surface coverage of remaining water and oxygen as a function of radiation dose by temperature programmed desorption (TPD). The main reaction products are OH and H with a fraction of oxygen from fully dissociated water. TPD spectra from a series of exposures reveal that EUV promotes formation of the partially dissociated water overlayer on Ru. Furthermore, loss of water due to desorption and dissociation is also observed. The water loss cross sections for amorphous and crystalline water are measured at 9 ± 2 × 10− 19 cm2 and 5 ± 1 × 10− 19 cm2, respectively. Comparison between the two cross sections suggests that crystalline water is more stable against EUV induced desorption/dissociation. The dissociation products can oxidize the Ru surface. For this early stage of oxidation, we measured a smaller (compared to water loss) cross section at 2 × 10− 20 cm2, which is 2 orders of magnitude smaller than the photon absorption cross section (at 92 eV) of gas phase water. The secondary electron (SE) contributions to the cross sections are also estimated. From our estimation, SE only forms a small part (20–25%) of the observed photon cross section.

In this paper we study the reaction of water and graphene under Extreme Ultraviolet (EUV) irradiation and in the presence of hydrogen. In this work, single layer graphene (SLG) on amorphous Si as an underlying substrate was dosed with water (0.75 mL) and exposed to EUV ( λ = 13.5 nm, 92 eV) with partial pressures of H 2 in the background. The results show that the aromatic structure of graphene, when exposed to EUV and H 2 , breaks down into aryl ketones and enols of 1,3 di-ketone. Infrared (IR) spectroscopy shows that SLG oxidizes, with increasing H 2 pressure leading to the grain boundary edges of graphene forming ketones and carboxylic acids. In situ and post exposure analyses also reveal that EUV exposure reduces the sp 2 content of the graphene layer, with the sp 3 content increasing, resulting in a more defective graphene layer.

The absorption of electromagnetic radiation by a planar structure, consisting of a three-layer dielectric-metal-dielectric coating on a metal backreflector, is analyzed. The conditions for total absorption are derived. Our analysis shows that, in contrast with bi-layer structures, the calculated layer thicknesses are feasible to fabricate for any metal. The proposed absorber design is of potential use in infrared, terahertz, and longer wavelength detectors and for radiant energy harvesting devices.

The role of oxide on Sn adhesion to Sc surfaces was studied with in-situ ellipsometry, X-ray photoelectron spectroscopy and secondary electron microscopy. Sn etching with hydrogen radicals was performed on metallic Sc, metallic Sc with a native oxide, and a fully oxidized Sc layer. The results show that Sn adsorbs rather weakly to a non-oxidized Sc surface, and is etched relatively easily by atomic hydrogen. In contrast, the presence of native oxide on Sc allows Sn to adsorb more strongly to the surface, slowing the etching. Furthermore, thinner layers of scandium oxide result in weaker Sn adsorption, indicating that the layer beneath the oxide plays a significant role in determining the adsorption strength. Unexpectedly, for Sn on Sc2O3, and, to a lesser extent, for Sn on Sc, the etch rate shows a variation over time, which is explained by surface restructuring, temperature change, and hydrogen adsorption saturation.

We have modified and stabilized the ruthenium surface by depositing a self-assembled monolayer (SAM) of 1-hexadecanethiol on a polycrystalline ruthenium thin film. The growth mechanism, dynamics, and stability of these monolayers were studied. SAMs, deposited under ambient conditions, on piranha-cleaned and piranha + H2SO4 cleaned substrates were compared to monolayers formed on H-radical-cleaned Ru surfaces. We found that alkanethiols on H-radical-cleaned Ru formed densely packed monolayers that remained stable when kept in a nitrogen atmosphere. X-ray photoelectron spectroscopy (XPS) shows a distinct sulfur peak (BE = 162.3 eV), corresponding to metal–sulfur bonding. When exposed to ambient conditions, the SAM decayed over a period of hours.

We study extreme ultraviolet (EUV) radiation induced defects in single-layer graphene. Two mechanisms for inducing defects in graphene were separately investigated: photon induced chemical reactions between graphene and background residual gases, and breaking sp(2) bonds, due to photon and/or photoelectrons induced bond cleaving. Raman spectroscopy shows that D peak intensities grow after EUV irradiation with increasing water partial pressure in the exposure chamber. Temperature-programmed desorption (TPD) experiments prove that EUV radiation results in water dissociation on the graphene surface. The oxidation of graphene, caused by water dissociation, is triggered by photon and/or photoelectron induced dissociation of water. Our studies show that the EUV photons break the sp(2) bonds, forming sp(3) bonds, leading to defects in graphene. (C) 2014 Elsevier B.V. All rights reserved.

The influence of a thin film substrate material on the etching of a thin layer of deposited tin (Sn) by hydrogen radicals was studied. The amount of remaining Sn was quantified for materials that cover a range of electronegativities. We show that, for metals, etching depends on the relative electronegativity of the surface material and Sn. Tin is chemically etched from surfaces with an electronegativity smaller than Sn, while incomplete Sn etching is observed for materials with an electronegativity larger than Sn. Furthermore, the amount of remaining Sn increases as the electronegativity of the surface material increases. We speculate, that, due to Fermi level differences in the material’s electronic structure, the energy of the two conduction bands shift such that the availability of electrons for binding with hydrogen is significantly reduced.

We review two approaches to achieving sub-diffraction-limited resolution coherent anti-Stokes Raman scattering (CARS) microscopy (Beeker et al., Opt. Express, 2009, 17, 22632 and Beeker et al., J. Herek, Phys. Rev. A, 2010, 81, 012507). We performed a numerical investigation, based on the density matrix model, of the CARS emission process and identified two modified CARS experiments that lead to sub-diffraction-limited resolution images. At the heart of both processes is the spatial manipulation of the coherence between the ground state and the vibrational state being probed by the CARS process via a control state and a control laser that is resonant with the ground state to control state transition. We find two possible regimes of operation: in the first regime, the control and vibrational states are coupled via incoherent processes so that the populations of the two states reach equilibrium very quickly compared to the relevant coherence times. Under these conditions, pre-populating the control state provides a saturable suppression of the coherence between the ground state and the vibrational state, suppressing CARS emission. By using a donut mode to pre-populate the control state, CARS is suppressed everywhere but the central node, allowing sub-diffraction-limited resolution imaging. In the second regime, the control state has a rather long coherence lifetime, and the resonant laser drives Rabi oscillations that periodically deplete the ground state. As a result, the CARS emission process is amplitude-modulated, which appear as sidebands on the CARS spectrum. By a process of spectral resolution and trilateration, sub-diffraction-limited resolution images can be obtained.

Carbon contamination on extreme ultraviolet (EUV) optics has been observed in EUV lithography. In this paper, we performed in situ monitoring of the build-up and removal of carbon contamination on Mo/Si EUV multilayers by measuring the secondary electron yield as a function of primary electron energy. An electron beam with an energy of 2 keV was used to simulate the EUV radiation induced carbon contamination. For a clean EUV multilayer, the maximum secondary electron yield is about 1.5 electrons per primary electron at a primary electron energy of 467 eV. The maximum yield reduced to about 1.05 at a primary electron energy of 322 eV when the surface was covered by a non-uniform carbon layer with a maximum thickness of 7.7 nm. By analyzing the change in the maximum secondary electron yield with the final carbon layer thickness, the limit of detection was estimated to be less than 0.1 nm. (C) 2010 Elsevier B. V. All rights reserved.

An experimental study of oxide reduction at the surface of ruthenium layers on top of multilayer mirrors and thin Ru/Si films is presented. Oxidation and reduction processes were observed under conditions close to those relevant for extreme ultraviolet lithography. The oxidized ruthenium surface was exposed to a low-temperature hydrogen plasma, similar to the plasma induced by extreme ultraviolet radiation. The experiments show that hydrogen ions are the main reducing agent. Furthermore, the addition of hydrogen radicals increases the reduction rate beyond that expected from simple flux calculations. We show that low-temperature hydrogen plasmas can be effective for reducing oxidized top surfaces. Our proof-of-concept experiments show that an in situ, EUV-generated plasma cleaning technology is feasible.

The deposition of carbon layers on the surfaces of optics exposed to extreme ultraviolet (EUV) radiation has been observed in EUV lithography. It has become of critical importance to detect the presence of the carbon layer in the order of nanometer thickness due to carbon's extremely strong absorption of EUV radiation. Furthermore, the development of efficient cleaning strategies requires that the nature of these carbon layers is well understood. Here, we present experimental results on the detection and characterization of carbon layers. grown on Mo/Si EUV reflecting optics, by laser-generated surface acoustic waves (LG-SAW). It was found that SAW pulses with a frequency bandwidth of more than 220 MHz can be generated and detected for multilayer mirrors and LG-SAW is sensitive enough to detect EUV induced carbon layers less than 5 nm thick. It was inferred from the low Young's modulus (< 100 GPa) that the carbon layer induced by EUV illumination in these vacuum conditions is mechanically soft and polymeric in nature with a high percentage of hydrogen. (C) 2008 Elsevier B.V. All rights reserved.

We introduce a model for hydrogen induced blister formation in nanometer thick thin films. The model assumes that molecular hydrogen gets trapped under a circular blister cap causing it to deflect elastically outward until a stable blister is formed. In the first part, the energy balance required for a stable blister is calculated. From this model, the adhesion energy of the blister cap, the internal pressure and the critical H-dose for blister formation can be calculated. In the second part, the flux balance required for a blister to grow to a stable size is calculated. The model is applied to blisters formed in a Mo/Si multilayer after being exposed to hydrogen ions. From the model the adhesion energy of the Mo/Si blister cap was calculated to be around 1.05 J/m2 with internal pressures in the range of 175-280 MPa. Based on the model a minimum ion dose for the onset of blister formation was calculated to be d = 4.2*10^18 ions/cm2. From the flux balance equations the diffusion constant for the Mo/Si blister cap was estimated to be D_H2 = (10+-1) *10^18 cm2/s., Comment: 7 pages, 6 figures, 2 tables

Plasmas induced by EUV radiation are unique since they are created without the need of any discharge. Moreover, it is essential to characterize these plasmas to understand and predict their long term impact on highly delicate optics in EUV lithography tools. In this paper we study plasmas induced by 13.5 nm EUV radiation in hydrogen gas. The electron density is measured temporally resolved using a non-invasive technique known as microwave cavity resonance spectroscopy. The influence of the EUV pulse energy and gas pressure on the temporal evolution of the electron density has been explored over a parameter range relevant for industry. Our experimental results show that the maximum electron density is in the order of 1014 m-3 and depends linearly on the EUV pulse energy. Furthermore, the maximum electron density depends quadratically on the pressure; the linear term is caused by photoionization and the quadratic term by subsequent electron impact ionization. The decay of the plasma is governed by ambipolar diffusion and, hence, becomes slower at elevated pressures. Similarities and differences of the same processes in argon are highlighted in this paper.

We used numerical modeling to study the evolution of EUV-induced plasmas in argon and hydrogen. The results of simulations were compared to the electron densities measured by microwave cavity resonance spectroscopy. It was found that the measured electron densities can be used to derive the integral amount of plasma in the cavity. However, in some regimes, the impact of the setup geometry, EUV spectrum, and EUV induced secondary emission should be taken into account. The influence of these parameters on the generated plasma and the measured electron density is discussed.

We demonstrate the generation of ultra-broadband supercontinua in Si 3 N 4 waveguides at a pump wavelength of 1560nm. The supercontinuum extends to beyond 2.6 μm wavelength in the infrared and has a spectral width of more then 453 THz.

With the development of stable, compact and reliable pulsed laser sources the field of characterizing materials through their nonlinear optical response has bloomed. Second harmonic generation by non-centrosymmetric crystal structures has provided a new spectroscopic tool of potentially great utility in the pharmaceutical field. The nonlinear optical response of various materials provides a very sensitive technique for the characterization of pharmaceutically interesting bulk compounds and dispersions, and determining their concentrations. This work has potential application for in-line monitoring and quality control of pharmaceutical manufacturing. In this article we have presented an extensive review of the spectroscopic techniques that make use of the nonlinear optical response of solid media. Also, we have presented the results of our own work in this field.

We report ultra-broadband supercontinuum generation in high-confinement Si3N4 integrated optical waveguides. The spectrum extends through the visible (from 470 nm) to the infrared spectral range (2130 nm) comprising a spectral bandwidth wider than 495 THz, which is the widest supercontinuum spectrum generated on a chip.

An experimental setup that directly reproduces extreme ultraviolet (EUV) lithography relevant conditions for detailed component exposure tests is described. The EUV setup includes a pulsed plasma radiation source, operating at 13.5 nm; a debris mitigation system; collection and filtering optics; and an ultra-high vacuum experimental chamber, equipped with optical and plasma diagnostics. The first results, identifying the physical parameters and evolution of EUV-induced plasmas, are presented. Finally, the applicability and accuracy of the in situ diagnostics is briefly discussed

In this paper, we report improvements to a previously developed method based on optical nonlinearity for characterizing polymorphism and concentration of pharmaceuticals in powdered and tablet form. An apparatus that measures the nonlinear optical response of a sample through second harmonic generation (SHG) is described. The response of several enalapril maleate-polyvinylpyrrolidone (PVP) tablets was measured, the results of which were used to determine the concentration of the drug. The current limit of detection of the apparatus was found to be approximately 1%-2%. Ranitidine hydrochloride (RN) polymorph forms I and II were also characterized using SHG. It was found that pure samples of forms I and II could be clearly and rapidly distinguished. Mixtures consisting of 50% form I and 50% form II were also distinguishable from the respective pure forms. An investigation was performed into the size dependence of the SHG response for crystalline lactose. It was found that the SHG response was a slowly decreasing monotonic function of particle size. Additional investigation into the angular dependence of the scattered SHG light was also undertaken for crystalline lactose. This new technique based on optical nonlinearity offers promise for application in monitoring of pharmaceutical manufacturing processes.

We report on a new method for characterising crystallinity and polymorphism of pharmaceutical drugs and excipients in the solid state. The optical nonlinearity of certain crystalline structures allows under certain circumstances the quantitative determination of polymorphism or crystallinity. An apparatus was set up to measure the second harmonic response of powdered samples when irradiated with a pulsed laser source. Here we present experimental results from various pharmaceutically interesting materials. This rapid, novel technique has potential for industrial monitoring of pharmaceutical manufacturing processes.

Molecular contamination of a grazing incidence collector for extreme ultraviolet (EUV) lithography was experimentally studied. A carbon film was found to have grown under irradiation from a pulsed tin plasma discharge. Our studies show that the film is chemically inert and has characteristics that are typical for a hydrogenated amorphous carbon film. It was experimentally observed that the film consists of carbon (~70 at. %), oxygen (~20 at. %) and hydrogen (bound to oxygen and carbon), along with a few at. % of tin. Most of the oxygen and hydrogen are most likely present as OH groups, chemically bound to carbon, indicating an important role for adsorbed water during the film formation process. It was observed that the film is predominantly sp3 hybridized carbon, as is typical for diamond-like carbon. The Raman spectra of the film, under 514 and 264 nm excitation, are typical for hydrogenated diamond-like carbon. Additionally, the lower etch rate and higher energy threshold in chemical ion sputtering in H2 plasma, compared to magnetron-sputtered carbon films, suggests that the film exhibits diamond-like carbon properties., 18 pages, 10 figures

Here, we propose a comparison-free inspection technique to detect particle contamination on the reticle of extreme ultraviolet (EUV) lithography systems, based on the photoluminescence spectral characteristics of the contaminant particles and their elemental composition. We have analyzed the spectra from different particles found on reticles in EUV lithographic systems and have determined the minimum detectable particle size: 25 nm for organic particles and 100 nm for Al particles. Stainless steel coatings (50 nm thick and 50 × 50 μm(2) in area) exhibit detectable photoluminescence, and the estimated minimum detectable particle is 2 μm.

The diffusion barrier properties of Sc2O3 against metal diffusion were studied. Tin and ruthenium were used as probe materials to study the barrier properties of Sc2O3 in thickness ranges that are of relevance for gate materials. Tin deposition and hydrogen radical etching from Sc2O3 layers of 0.5-1.5 nm thickness, deposited on Ru, show that these Sc2O3 layers effectively block the diffusion of Sn into Ru. We show that Sn adhesion and etching depends strongly on the thickness of the Sc2O3 film. The etch-rate is found to be inversely proportional to the Sc2O3 layer thickness, which we attribute to Sc2O3 becoming a more effective charge transfer barrier at larger thicknesses.

We report on blister formation in nanometer thick Mo/Si multilayer structures due to exposure to hydrogen ion fluxes. The influence of hydrogen flux and ion energy for blister formation have been measured and compared to a blister model. The blister number density increases significantly around 100 eV when increasing the ion energy from 50 to 200 eV. This stepwise behavior could be explained by the fact that for energies >100 eV hydrogen ions could directly penetrate to the depth where delamination takes place. From the blister model also the blisters internal pressure and surface energy was calculated to be around 100-800 MPa and respectively.

We have studied the effect of photoelectrons on defect formation in graphene during extreme ultraviolet (EUV) irradiation. Assuming the major role of these low energy electrons, we have mimicked the process by using low energy primary electrons. Graphene is irradiated by an electron beam with energy lower than 80 eV. After e-beam irradiation, it is found that the D peak, I(D), appears in the Raman spectrum, indicating defect formation in graphene. The evolution of I(D)/I(G) follows the amorphization trajectory with increasing irradiation dose, indicating that graphene goes through a transformation from microcrystalline to nanocrystalline and then further to amorphous carbon. Further, irradiation of graphene with increased water partial pressure does not significantly change the Raman spectra, which suggests that, in the extremely low energy range, e-beam induced chemical reactions between residual water and graphene is not the dominant mechanism driving defect formation in graphene. Single layer graphene, partially suspended over holes was irradiated with EUV radiation. By comparing with the Raman results from e-beam irradiation, it is concluded that the photoelectrons, especially those from the valence band, contribute to defect formation in graphene during irradiation., appears in Journal of Applied Physics 2014

We report the realization of a singly resonant optical parametric oscillator (SRO) that is designed to provide narrow-bandwidth, continuously tunable radiation at a wavelength of 1163 nm for optical cooling of osmium ions. The SRO is based on periodically poled, magnesium-oxide-doped lithium niobate and pumped at 532 nm. The output coupling of the resonant idler wave is adjusted to yield up to 400 mW of 1163 nm radiation, with a bandwidth of a few megahertz. For continuous frequency tuning of the idler wave, the SRO is equipped with an intracavity etalon, and the cavity length is controlled with a piezo-actuated mirror synchronized to the etalon angle.

We describe the wide and rapid wavelength tuning of a continuous-wave master-oscillator power-amplifier system consisting of a semiconductor-amplifier-based oscillator and an ytterbium (Yb)-doped fiber amplifier. The oscillator utilizes an acoustooptic tunable filter and an intracavity etalon to achieve wavelength tuning of 36 nm in 5 ms. The 50-mW output from the master oscillator was amplified to over 9 W in an Yb-doped fiber amplifier.

Cleaning of contamination of optical surfaces by amorphous carbon (a-C) is highly relevant for extreme ultraviolet (EUV) lithography. We have studied the mechanisms for a-C removal from a Si surface. By comparing a-C removal in a surface wave discharge (SWD) plasma and an EUV-induced plasma, the cleaning mechanisms for hydrogen and helium gas environments were determined. The C-atom removal per incident ion was estimated for different sample bias voltages and ion fluxes. It was found that H2 plasmas generally had higher cleaning rates than He plasmas: up to seven times higher for more negatively biased samples in EUV-induced plasma. Moreover, for H2, EUV-induced plasma was found to be 2-3 times more efficient at removing carbon than the SWD plasma. It was observed that carbon removal during exposure to He is due to physical sputtering by He+ ions. In H2, on the other hand, the increase in carbon removal rates is due to chemical sputtering. This is a new C cleaning mechanism for EUV-induced plasma, which we call 'EUV-reactive ion sputtering'. © 2014 IOP Publishing Ltd.

Probe theories are only applicable in the regime where the probe’s perturbation of the plasma can be neglected. However, it is not always possible to know, a priori , that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas on a similarly short time scale as investigated here. Indeed, in the case studied here, probe measurements would lead to, either a large overestimate, or underestimate of the plasma density, depending on the chosen probe theory. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements. However, limiting cases of probe theories can be used to estimate upper and lower bounds on plasma densities. These theories include and neglect orbital motion, respectively, with different collisional terms leading to intermediate estimates.

Coherent anti-Stokes Raman scattering (CARS) offers label-free detection with chemical selectivity. In order to achieve spectral and therefore chemical resolution two synchronized narrowband pulses have to be provided by an appropriate light source. The often used complex laser systems as well as the more recently introduced all- fiber approaches based on seeded four-wave mixing (FWM) all lack the compatibility with integrated photonics. Here, we present theoretical investigations of a CARS light source based on silicon nitride waveguides, which is compatible, for instance, with integrated microfluidic channels and integrated light sources and therefore is of great interest for analyzing CARS spectra in a lab-on-a-chip setup. Furthermore, the required laser intensities are found to be reduced by one order of magnitude based on the higher efficiency of FWM in silicon nitride waveguides.

Depth-based 3D formats are currently being developed as extensions to both AVC and HEVC standards. The availability of depth information facilitates the generation of intermediate views for advanced 3D applications and displays, and also enables more efficient coding of the multiview input data through view synthesis prediction techniques. This paper outlines several approaches that have been explored to realize view synthesis prediction in modern video coding standards such as AVC and HEVC. The benefits and drawbacks of various architectures are analyzed in terms of performance, complexity, and other design considerations. It is hence concluded that block-based VSP prediction for multiview video signals provides attractive coding gains with comparable complexity as traditional motion/disparity compensation.

The adsorption and reactions of ethanol on Ru(0001) were studied with temperature-programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS). Ethanol was found to adsorb intact onto Ru(0001) below 100 K. From 175 K to 200 K, ethanol is converted into ethoxy groups, which undergo further dehydrogenation, leading to the formation of hydrogen, CO and surface carbon. The absence of aldehydes and methane as desorbing product molecules, as well as the intermediate species observed in the RAIRS spectra, show that the reaction proceeds via β-hydrogen abstraction of the ethoxy groups, resulting in an oxametallacycle reaction intermediate that undergoes decarbonylation to CO, C and hydrogen. The surface carbon, formed by the reaction, decreases the reactivity of the surface in subsequent reaction cycles. The amount of CO produced from a full monolayer of ethanol is limited to about 0.1 ML, because of the competition between ethanol dehydrogenation and desorption. © 2013 Elsevier B.V.

Directed self-assembly (DSA) of block copolymers (BCPs) is a promising technology for advanced patterning at future technology nodes, but significant hurdles remain for commercial implementation. The most widely studied material for DSA is poly(styrene-block-methyl methacrylate) (PS-PMMA), but the relatively weak segregation strength of PSPMMA results in some limitations. This paper reports on these limitations for PS-PMMA and highlights a path to success through use of more strongly segregated “high-χ” block copolymers. In general, stronger segregation is predicted to lower defectivity at equilibrium, but unfortunately, kinetics of self assembly also becomes much slower as segregation strength increases. Recognizing diffusion is much faster for cylinder morphologies than lamellar ones, we have investigated new cylinder-forming BCPs that enable defect elimination with thermal annealing processes. In addition, a formulation strategy is presented that further improves the kinetics of the assembly process, enabling tremendous improvements in defectivity over simple BCP systems. Excitingly, successful chemoepitaxy DSA with a high-χ lamellar BCP is also demonstrated using a thermal annealing process and no top coat. These technologies hold promise to enable DSA with thermal annealing processing across pitches from 40 - 16 nm.

We present a theoretical investigation of stimulated emission pumping to achieve sub-diffraction-limited spatial resolution in coherent anti-Stokes Raman scattering (CARS) microscopy. A pair of control light fields is used to prepopulate the Raman state involved in the CARS process prior to the CARS signal generation. Efficient prepopulation is achieved by employing a path via an electronic or vibrational state. Thereby, the buildup of a coherence between the ground and Raman state during irradiation by the light fields for CARS signal generation is prevented, resulting in the suppression of the CARS intensity by more than 99.8%. Two-dimensional spatial excitation profiles have been calculated using donut-shaped spatial profiles for the control light fields, thus, an intensity-dependent narrowing of the CARS excitation profiles below the diffraction limit. Using computer-generated test images we demonstrate a resolution beyond the diffraction limit for CARS microscopy, which is scalable by the control light field intensity, similar to stimulated emission depletion microscopy.