Atomically thin transition-metal dichalcogenides (TMD) hold promise for making ultrathin-film photovoltaic devices with a combination of excellent photo-absorption and mechanical flexibility. However, reported absorption for photovoltaic cells based on TMD materials is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we discuss that taking advantage of the mechanical flexibility of two dimensional (2D) materials by rolling their Van der Waal heterostructures such as molybdenum disulfide (MoS2)/graphene (Gr)/hexagonal boron nitride (hBN) to a spiral solar cell, leads to strong light matter interaction allowing for solar absorptions up to 90%. The optical absorption of a 1 µm-long hetero-material spiral cell consisting of the aforementioned hetero stacks is about 50% stronger compared to a planar MoS2 cell of the same thickness; although the volumetric absorbing material ratio is only 6%. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.

Ethylene-vinyl acetate (EVA) is the most commonly used photovoltaic (PV) encapsulant material. As such, it is exposed to UV, thermal cycles, temperature gradients between the glass side and the silicon wafer side, and moisture ingress. The combined effect of all these may lead to different physical and chemical changes of EVA including polymer chain alignment, crystallinity, and crosslinking density, as well as the mechanical stresses resulting from coefficient of thermal expansion (CTE) and aging, thus, reducing the adhesion of EVA and eventually lead to failure of the encapsulation. Measuring the effects of UV exposure on EVA can help in understanding the failure mechanism of PV modules. In this work, we suggest a novel and non-destructive way to measure EVA degradation after UV exposure by using Raman spectroscopy (RS). Samples were exposed to NIST SPHERE with UV irradiation, moisture, and elevated temperatures. The physical and chemical changes as well as the internal stresses were monitored by RS, and the intensities of the corresponding Raman peaks ratio were analyzed. The results have indicated that Raman scattering is a sensitive tool to study EVA encapsulant degradation.

In this study, the wetting behaviors of an underwater oil droplet on structured surfaces were investigated using molecular dynamics simulations and experiments. The wetting states and contact angles of the underwater oil droplet on different hydrophobic surfaces were simulated. The simulation results showed that there were three kinds of equilibrium states on the pillar surfaces: the Wenzel, cross, and Cassie states. Moreover, the equilibrium state of the underwater oil droplet transformed from a Wenzel to Cassie state when the water contact angle decreased. The contact angle of the underwater oil droplet increased as the water contact angle decreased. Furthermore, the wetting behaviors of the underwater oil droplet on rough polytetrafluoroethylene and silicon surfaces were studied in experiments. The experimental results also indicated that the contact angle of the underwater oil droplet increased as the water contact angle decreased, which corresponded well with the simulation results.

Under high burnup UO2 fuel pellets can experience high burnup structure (HBS) at the rim also known as rim effect. The HBS is exceptionally porous with fine grain sizes. HBS increases the swelling further than it would have achieved at a larger grain size. A theoretical swelling model is used in conjunction with a grain subdivision simulation to calculate the swelling of UO2. In UO2 the nucleation sites are at vacancies and the bubbles are concentrated at grain boundaries. Vacancies are created due to irradiation and gas diffusion is dependent on vacancy migration. In addition to intragranular bubbles, there are intergranular bubbles at the grain boundaries. Over time as intragranular bubbles and gas atoms accumulate on the grain boundaries, the intergranular bubbles grow and cover the grain faces. Eventually they grow into voids and interconnect along the grain boundaries, which can lead to fission gas release when the interconnection reaches the surface. This is known as the saturation point. While the swelling model used does not originally incorporate a changing grain size, the simulation allows for more accurate swelling calculations by introducing a fractional HBS based on the temperature and burnup of the pellet. The fractional HBS is introduced with a varying grain size. Our simulations determine the level of swelling and saturation as a function of burnup by combining an independent model and simulation to obtain a more comprehensive model.

Incorporating nanotechnology processes and techniques to Li ion batteries has helped to improve the cycling capabilities and overall performance of several lithium ion battery chemistries. Nanostructuring a lithium ion battery’s anode and cathode, allows for extremely high surface area electrodes to be produced and utilized in many of these battery systems. Using a nanoporous Anodized Aluminum Oxide (AAO) membrane with nanopores of 200nm in diameter as a template, high surface area nanostructured electrode materials can be synthesized and utilized in a lithium ion cell. Through the use of RF magnetron sputter coating, these nanoporous AAO templates can be sputter coated with a thin film of active anode or cathode materials. The anode and cathode material in this research are SnO2 and LiCoO2, respectively. Nanostructured SnO2 has been investigated as an alternative high capacity anode to replace the more commonly used carbon based anodes of current lithium ion batteries. A novel nanostructured SnO2/LiCoO2 cell can be fabricated in a liquid electrolyte. The galvanostatic cell cycling performance will be discussed. Nanostructuring both electrode materials as well as the electrolyte can lead to a novel all-solid-state Li ion battery. Nanostructured SnO2 anode and LiCoO2 electrodes have been generated along with a polyethylene-oxide (PEO) based electrolyte nanoconfined in an AAO membrane, to generate a functioning nanostructured all-solid-state cell. The cell was investigated using AC impedance spectroscopy and galvanostatic cell cycling. The cycling results of both SnO2/LiCoO2 cell systems will be discussed.

The liquidus temperature (TL) of rare earth (RE) was determined for alumino-borosilicate glasses for treating americium and curium that have been studied previously. Their work covers a wide range of glass composition with various crystalline phases as primary phase. Present work is aimed at understanding the effect of glass composition on TL for waste glasses designed for vitrifying RE oxides wastes. In a sufficiently narrow composition region, this effect can be represented by a first-order model fitted measured TL versus composition data. Test glasses were formulated by varying of component fractions one-at-a-time. The glasses contained SiO2, B2O3, and Al2O3 as glass formers and Nd2O3 with CeO2 as simulated RE waste. Twenty glasses were made to investigate crystallization as a function of temperature and glass composition. The primary crystalline phase was Ce-borosilicate (Ce3BSi2O10), secondary phases were Al-containing crystals (Al2O3 and Al10Si2O19), and crystalline CeO2. A first-order model was fitted to crystal fraction versus glass composition data. Generally, SiO2 and B2O3 tend to suppress crystallization, Al2O3 has little effect, and, as expected, RE components (Nd2O3 and CeO2) promote it. The correlation coefficient, R2, was 0.89 for the primary crystalline phase TL as a linear function of composition.

Preparation of three-dimensionally architectured porous biomaterials can be achieved in a one-step process by stabilizing gelatin with L-lysine diisocyanate ethyl ester (LDI) in water. The reaction of gelatin with LDI in presence of water leads to the formation of oligourea bridges between gelatin molecules and oligourea chains grafted on gelatin. The number and the length of the bridges, as well as of the grafted chains strongly depend on the concentration of the LDI used for the stabilization, and this has huge influence on the mechanical properties of the material on different hierarchical levels. Higher LDI concentrations yield materials with increased deformation resistance in tensile tests due to the higher number of covalent and physical netpoints in the material. However, mechanical properties determined on the micro-level by AFM indentation showed the opposite trend, i.e. a decrease of Young’s modulus with increasing LDI content. This was interpreted by a decreasing number of shorter oligourea bridges between gelatin chains with decreasing LDI content.

Atomic force microscopy (AFM) is used to measure local electrical conductivity of HPHT nanodiamonds (NDs) dispersed on Au substrate in the as-received state and after thermal or plasma treatments. Oxygen-treated NDs are highly electrically resistive, whereas on hydrogen-treated NDs electric current around -200 pA at -2 V is detected. The as-received NDs as well as NDs after an underwater radio-frequency (RF) plasma or laser irradiation (LI) treatments contain both electrically conductive (two types: highly and weakly conductive) and highly resistive particles. The higher conductivity is attributed to H-terminated (RF) or graphitized (LI) NDs. The lower conductivity is attributed to NDs with hydrogenated amorphous carbon shell.

The range of polishing-induced subsurface damage remaining in a commercially available production grade 4H-SiC (0001) epi-ready substrate was evaluated by the observation from the (-1100) cleavage plane using two kinds of highly strain-sensitive characterization methods. Firstly, the analysis using electron backscattered diffraction (EBSD) with a submicron spatial resolution was conducted on the exposed cross sectional plane. Then, for the further quantitative evaluation excluding the influence of roughness or contamination of the cleavage plane, a synchrotron X-ray micro-diffraction experiment was carried out. The range of the subsurface damage evaluated in those experiments was ensured by confirming none of additional strain inserted at the cleavage, as compared with the damage-free substrate prepared by high temperature thermal etching. As a result, the depth of the residual strained region below polishing-induced scratches at the surface was estimated to be in the range of a few microns, which is much deeper than the previously reported value of 100 nm by cross-sectional transmission electron microscopy. It suggests a potential of EBSD for the conventional tool to characterize even a small amount of strain in SiC single crystal.

The deposition of PbS thin films by the chemical bath deposition method using sodium citrate as non-toxic complexing agent is presented. As-deposited PbS films and those annealed at 200 and 300 °C in argon atmosphere were formed by tightly compact spherical particles homogeneously distributed along the substrates. The XRD analysis shows that all the films had a galena type cubic crystalline structure. The crystallite size of the as-deposited film was 17 nm which decreased to 14 nm when the film was annealed to 300 °C. Thermal treatments to the films produced a shift of the optical band gap from 1.34 to 1.49 eV. Furthermore, the as-deposited PbS films were photosensitive showing a conductivity of 10-2 Ω-1 cm-1 under illumination. Such a conductivity increased to 10-1 Ω-1 cm-1 with the thermal treatment at 200 °C. The evaluation of the PbS film using a CdS thin film partner as window in the solar cell configuration showed an open circuit voltage of 88 mV and a short current density of 3.5 mA/cm2.

In this paper, the electrical properties of bottom-gate (BG) polycrystalline silicon (poly-Si) thin-film transistors (TFTs) by NiSi2 seed-induced lateral crystallization (SILC) and its applications are presented. Sequential lateral solidification (SLS), which is one of crystallization methods, is known to have poor electrical properties of TFTs with BG structures due to problems induced by laser. Therefore, the laser method cannot be used to well-developed production line of amorphous-Si (a-Si) TFT, resulting in large initial investment cost to change fabrication procedures. On the other hand, the BG poly-Si TFT by SILC (SILC-BGPS TFT) has basically compatible process flows with that of the a-Si TFT. The SILC-BGPS TFT exhibited threshold voltage of -3.9 V, steep subthreshold slope of 130 mV/dec, a high field-effect mobility of 129 cm2/Vs , and Ion/Ioff ratio of ∼106.

Mesoporous zinc oxide nanopowders were synthesized by the homogenous precipitation method. Zinc acetate dissolved in water, at different molar concentrations, was used as Zn precursor, whereas ammonium carbonate ((NH4)2CO3) and ammonium hydroxide (NH4OH) were used to prepare the precipitant solutions. The precipitated powders were dried in a conventional drying chamber at 100°C for 1 h, and then calcined at 400°C during 2 h. Crystal structure of powders was determined by X-ray Diffraction (XRD), and the crystallite sizes were calculated from Scherrer’s formula. Morphological characteristics (size and shape) were analyzed from Scanning Electron Microscopy (SEM). The surface area and the pore volume were obtained from BET analysis. The hexagonal wurtzite phase was corroborated in all synthesized powders, irrespective of the synthesis conditions. From SEM micrographs different structures, depending on the experimental routes, were observed. In order to test the sensing properties of the ZnO nanopowders, 10 mm diameter pellets were manufactured and then measured in a propane (C3H8) atmosphere at different gas concentrations and temperatures. Pellets processed from ZnO powders at 0.05, 0.35, and 0.5 M presented the highest sensitivity, 413, 532, at 300°C and 500 ppm of C3H8.

In the frame of minor actinide recycling, (U,Am)O2 are promising transmutation targets. To assess the thermodynamic properties of the U-Am-O system, it is essential to have a thorough knowledge of the binary phase diagrams, which is difficult due to the lack of thermodynamic data on the Am-O system. Nevertheless, an Am-O phase diagram modelling has been recently proposed by Gotcu. Here, we show a recent investigation of the Am-O system using in-situ High Temperature X-ray Diffraction under controlled atmosphere. By coupling our experimental results with the thermodynamic calculations based on the Gotcu model, we propose for the first time a relation between the lattice parameter and the departure from stoichiometry.

Silver nanostructures are directly grown on the apex of commercially available silicon AFM probes using our area-selective electroless deposition: the apex of a silicon AFM probe is irradiated using a focused ion beam (FIB), and then the FIB-irradiated AFM probe is exposed to a pure AgNO3 aqueous solution. With this method, a silver nanostructure selectively grows on the tip apex where the native oxide layer has been removed in response to FIB irradiation. Silver ions are reduced by the electrons flowing from the silicon probes into the solution through the FIB-irradiated area owing to the difference in Fermi energy between silicon and the solution. The morphology of the growing silver depends on the concentration of both AgNO3 and the electrons. The growth of a gold nanoflower is also demonstrated on the apex of a silicon AFM probe.

Graphenic carbon (GC) x-ray transmission windows for EDX and XRF applications with a high transparency for x-rays below 2.5 keV have been fabricated on 6 inch wafers with a CMOS-compatible CVD process. GC windows with an open diameter of 7.4 mm and a thickness of 770 nm withstand up to 6.5 bars of differential pressure. A high transmissivity of 40 % for fluorine Kα (0.677 keV) radiation is demonstrated for a GC thickness of 650 nm. The GC membranes outperform beryllium (Be) windows, in terms of higher x-ray transmission and better mechanical stability while avoiding the toxicity of Be. Optical profilometry has been employed to visualize a large deformation of the GC layer during the window fabrication. This seems to limit the thickness of the GC windows that can currently be fabricated. A two-step growth process can overcome these limitations and windows with a thickness of up to 6 µm have been realized.

The room temperature electronic characteristics of resonant tunneling diodes (RTDs) containing AlAs/InGaAs quantum wells are studied. Differences in the peak current and voltages, associated with device-to-device variations in the structure and width of the quantum well are analyzed. A method to use these differences between devices is introduced and shown to uniquely identify each of the individual devices under test. This investigation shows that quantum confinement in RTDs allows them to operate as physical unclonable functions.

Titania nanotubes were prepared by anodic oxidation of Ti. The titania surfaces were partially coated with Zn by reacting zinc acetate with the nanotubes and then annealed. [1] An annealed nanotube cluster was placed carefully on a silicon wafer using tweezers. Secondary electron images were acquired by bombarding with Cs+ and observing the ejected OZn- and OTi- respectively. The SIMS analysis was done in ultra-high vacuum (∼ 10-10 Torr). The location of before and after the SIMS analysis was confirmed by scanning electron microscopy (SEM). Specific areas with various orientations (vertical and horizontal orientations) of the nanotubes were selected for the NanoSIMS 50L analysis. The NanoSIMS 50L is made by Ametek Cameca, Gennevillieres, France and is capable of doing in situ isotopic analysis of surfaces at high spatial resolution (25 nm2). The average ZnO/TiO was ∼1.8%, confirming the actual content of Zn used during synthesis of the nanotubes. Qualitatively, the TiO/ZnO ratio increased with increasing depth implying that ZnO concentration was decreasing as we probed into the nanotubes.

In this study, we successfully demonstrate a carrier-injection InGaAsP variable optical attenuator (VOA) with a lateral P-I-N junction formed by Ni-InGaAsP alloy and Zn diffusion on a III-V on insulator (III-V-OI) wafer. The Ni-InGaAsP alloy for the n+ junction is formed by direct reaction between Ni and InGaAsP after annealing at 350°C. The p+ junction is formed by the Zn diffusion at 500°C using Zn doped spin-on glass (SOG). By both techniques, we successfully reduce the sheet and contact resistivity in the lateral P-I-N junction even with the relatively low-temperature process as compared with the P-I-N junction formed by conventional Si and Be ion implantation. By injecting carriers into the InGaAsP waveguide through the lateral P-I-N junction, we achieve the optical attenuation of -40 dB/mm with an injection current density of 40 mA/mm at a 1.55 μm wavelength.