The high-temperature performance of electronics packages was studied at 180°C, 200°C and 240°C for 3,000h. The structure tested consisted of a fairly large silicon chip attached with anisotropic conductive adhesive (ACA) onto an adhesiveless PI substrate. These structures showed good electrical reliability at 180°C. Several early failures were seen at the other temperatures. However, only 23% of the test samples failed at 200°C, while considerably more failures were seen at 240°C. The results showed that good high-temperature reliability can be achieved with polymer interconnections. However, the exposure time should be limited, especially at very high temperatures, to avoid failures caused by the materials becoming brittle.

Nanocrystalline cellulose (NCC) is an emerging renewable nanomaterial that ispromising for many diverse applications. As a renewable material, NCC and itsderivatives have been widely studied, focusing on their biological, chemical, aswell as mechanical properties. The electro-optical properties of NCC, however,remain relatively under explored. Birefringence is one of the importantproperties that make the NCC very attractive for photonic applications. Therode-like NCC fibers dispersed in certain solutions exhibit a specific preferredorientation which depends on their electrical charge, physical dimensions andthe type of solutions used to disperse NCC fibers. In a recent study ofKerr-effect in functionalized NCC solutions, we demonstrated that it is possibleto control the orientation of NCC fibers under an applied electric field.NCC-based spatial light modulator devices were fabricated and characterized.Results showed that the transmittance of the device can be controlled throughfrequency modulation of the applied electric field. In this paper we present thefabrication and electro-optical characterization of the device and discuss therelevant properties of NCC and future approaches to optimize and improve theircharacteristics and performance.

Presbyopia is a ubiquitous age-related disability of the eye, affecting an estimated 1.04 billion people worldwide, reducing their ability to focus on nearby objects. The various solutions to this inevitable vision deterioration are not compromise-free, with a growing need for approaches beyond conventional spectacles. The research motivation for this work is the unique solution offered by liquid crystal (LC) contact lenses to create compromise-free vision across the whole field of view. The distinctive property of LC lenses is that they are switchable, with the application of a voltage activating the lens. The change in focal power is facilitated via a voltage-dependent change in refractive index of the LC. We have successfully demonstrated several versions of electrically switchable LC contact lenses with variable additional optical power of up to +3.00 D, ideal for the correction of presbyopia.

This paper offers a review of the optical and electro-optical performance recently demonstrated for the different modes of operation realized in nematic systems, including planar (homogeneous) and vertically aligned (homeotropic) aligned devices. The change in optical power obtained depends on the choice of geometry and LC material. A material with higher birefringence allows a thinner LC-lens layer to achieve a particular focal power. In the homeotropic geometry, the refractive index of the LC layer is a minimum in the ‘off’ state (ordinary refractive index, no) and the mode is polarization-independent, offering a significant advantage over planar lens designs. The construction is also simplified as only one alignment layer needs to be rubbed. Depending on the geometry used, continuously variable changes in focal power of up to +3.00D have been achieved. The response time of the lenses can be better than half a second, achieved with small applied voltages of ~7Vrms.

A further important stage in the optimization of the contact lenses is the inclusion of graphene as the electrodes. Conventional ITO electrodes are too brittle for these flexible optical systems. The paper also reviews the successful incorporation of graphene into the lenses, with excellent optical and electro-optical results. The device demonstrates the huge potential of graphene in an unconventional liquid crystal device geometry that includes curvature over a relatively large area.

New material phases formed under non-equilibrium conditions at pressures above 100 GPa and temperatures exceeding 104K, the conditions of the warm dense matter (WDM), have become accessible using micro-explosions triggered by ultra-short sub-1 ps pulses tightly focused into micro-volume with cross sections comparable with the wavelength of light. Laser-induced micro-explosions convert a material in a focal volume into a non-equilibrium disordered plasma state confined inside the bulk of pristine crystal. Ultra-high quenching rates overcome kinetic barriers to the formation of new metastable high pressure phases, which are preserved in the surrounding pristine crystal for following recovery and exploitation. Direct laser writing was used to pattern large areas by closely packed arrays of the microexplosion modified sites for structural characterisation of the minute volumes of nano-materials with transmission electron microscopy, diffraction and synchrotron X-ray diffraction. The method of ultrafast-laser induced confined microexplosion is demonstrated for modification and creation of new phases in case of bcc-Al inside sapphire, valence change of Fe-ions in olivine, formation of new tetragonal bt8 and st12 phases of silicon, Ge and O separation in GeO2 glass and molecular oxygen formation inside voids at the site of microexplosion inside glasses.

Directed self-assembly (DSA) of block copolymers is a promising alternative nanolithographic technology aimed at producing sub-40 nm patterns. One important opportunity for DSA is the creation of periodic arrays of lines and spaces. The two most common methods for line-space applications are chemoepitaxy (typically using a lamella-forming PS-b-PMMA diblock) and graphoepitaxy (typically using cylinder-forming block copolymers with a Si-containing minority block). Mesoscale modeling, such as Self-Consistent Field Theory (SCFT), has by now become an important tool in formulation screening and predicting polymer morphologies and defect types and probabilities. Here, we use SCFT to study the morphology of cylinder-forming PS-b-PDMS diblocks in rectangular trenches with grafted PS-brushes. The targeted morphology is 2 cylinders per trench (3X multiplication). We compute phase diagrams and determine equilibrium morphologies as a function of brush thickness and guiding weir height. Using those equilibrium morphologies as starting points, we also compute structures and free energies of typical defects, including dislocation and disclination dipoles, broken lines, and bridges. The predicted defect structures and probabilities are in a reasonable qualitative agreement with recent experimental results.

In this work we explore the mechanisms responsible for Random Telegraph Noise(RTN) fluctuations in HfOx Resistive Random Access Memory (RRAM)devices. The statistical properties of the RTN are analyzed in many operatingconditions exploiting the Factorial Hidden Markov Model (FHMM) to decompose themultilevel RTN traces in a superposition of two-level fluctuations. This allowsthe simultaneous characterization of individual defects contributing to the RTN.Results, together with multi-scale physics-based simulations, allows thoroughlyinvestigating the physical mechanisms which could be responsible for the RTNcurrent fluctuations in the two resistive states of these devices, includingalso the charge transport features in a comprehensive framework. We consider twopossible options, which are the Coulomb blockade effect and the possibleexistence of metastable states for the defects assisting charge transport.Results indicate that both options may be responsible for RTN currentfluctuations in HRS, while RTN in LRS is attributed to the temporary screeningeffect of the charge trapped at defect sites around the conductive filament.

Germanene, the 2D graphene-like Ge nanosheet, has been recently the subject of many theoretical studies and experimental attempts to synthesize it on Ag(111), Au(111) and Pt(111) surfaces. The experimental and theoretical evidences of germanene show a 2D continuous honeycomb layer with a buckled conformation. Density functional theory (DFT) calculations have predicted a larger buckling for germanene than silicene whose origin is also associated with a pseudo Jahn–Teller (PJT) effect. In this work we show that despite the fact that both, silicene and germanene possess a buckled conformation with a PJT origin, their vibronic coupling have different origins. The analysis is based on the PJT puckering instability of the hexagermabenzene molecule, the single hexagonal unit of germanene. This is done through the linear vibronic coupling model between the ground and the lowest excited states, which leads to a puckering distortion of the more symmetric cluster. We study both, the multilevel superposition vibronic model and possible mixing of excited states of different irreducible representations, which have been used to show the origin of similar structural transitions in hexagonal silicon and gold ring systems respectively. We show that contrary to other cases with one six-member rings, for the hexagermabenzene molecule a mixture of both the multilevel PJT and a ground state coupling with two quasi-degenerate excited states is necessary for a satisfactory explanation of puckering. Our model allows a determination of the coupling constants and predicts simultaneously the Adiabatic Potential Energy Surface (APES) behavior for the ground and excited states around the maximum symmetry point. The analysis is based on a scalar relativistic DFT and time-dependent DFT (TD-DFT) calculations in the Zero Order Regular Approximation (ZORA) using the B3LYP hybrid functional.

Silicon nanocrystals (SiNCs) are quantum dots that do not contain toxic metals and exhibit a photoluminescent response that may be tailored via changes in particle dimension as well as surface chemistry. Herein, we present a promising hybrid nanomaterial that combines the favourable properties (e.g., photoluminescence, biocompatibility, and surface chemistry) of SiNCs with the magnetic characteristics of Fe3O4 nanoparticles (NPs). Linking these two complementary nanomaterials via DCC coupling has yielded a new advanced hybrid material that possesses the characteristics of its constituents and affords a photoluminescent system that responds to permanent magnets.

Operation of single crystalline Ca3TaGa3Si2O14 (CTGS) and La3Ga5SiO14 (LGS) bulk acoustic wave resonators is demonstrated up to 1270 °C and 1470 °C, respectively. The mass sensitivity of such devices is about 35 cm2 Hz/μg at 800 °C. Therefore, they are sensitive transducers suited to monitoring, for example, mass deposition processes at high temperatures. The electromechanical loss in CTGS is found to be significantly lower than that in LGS. Platinum coated CTGS samples show a remarkable long-term stability at 1000 °C in air. After an initial period of 300 h, the conductivity is found to remain nearly constant for at least 2400 h. Measurements of resonance frequency of CTGS for 1000 h show a qualitatively similar sequence, with an initial systematic increase followed by nearly constant values. In contrast, measurements on platinum-coated LGS plates show a conductivity decreasing by 15 % over a period of 5000 h.

Eumelanins, the black insoluble pigments of human skin, eyes and substantia nigra (neuromelanin), stand today as a unique source of inspiration for the design and implementation of soft biocompatible multifunctional materials for bio-optoelectronic devices. Interest in eumelanins stems from bioavailability, biocompatibility and a peculiar set of physicochemical properties, i.e. broadband absorption in the UV-visible range, intrinsic free radical character, water-dependent hybrid ionic–electronic conductor behaviour, supporting optimistic feelings about a possible rise of eumelanin-mimics as innovative bioinspired solutions for organic bioelectronics.

However, a number of conceptual and technological gaps still hinder a rapid progress of melanin-based organic electronics and bioelectronics, including in particular the limited contribution of electronic conductivity and current decay with time under biasing. Herein, we provide a concise overview of the structural and optoelectronic properties of melanins with a view to bringing to focus main issues and challenges en route to bioelectronic applications.

Group 6 transition metal oxide thin films are in large demand for photocatalysis, heterogeneous catalysis, fuel cell, battery and electronic applications. Pulsed laser deposition offers an inexpensive method for the preparation of nanostructured thin films that may be suitable for heterogeneous catalysis. We have synthesized molybdenum oxide thin films using two types of pulsed laser deposition (PLD). The first method utilizes femtosecond laser-based PLD (f-PLD) while the second method uses an excimer (nanosecond) laser-based PLD (n-PLD). The PLD films have been deposited using f-PLD and, separately, n-PLD on glass and silicon substrates and subsequently annealed to 450 °C for up to 20 hours in air using a Linkam stage. SEM, XRD and Raman spectroscopic characterization shows that the f-PLD films are substantially more textured and partially crystalline prior to annealing whereas the n-PLD-grown thin films are much smoother and predominantly amorphous. A 3-dimensional nano-crystalline structure is evident in the post-annealed f-PLD synthesized thin films, which is desirable for catalytic applications. XPS elemental analysis shows that the stoichiometry of the f-PLD and n-PLD thin films is consistent with the presence of MoO2 and MoO3. Our results are discussed in terms of thin film growth models suitable for f-PLD vs n-PLD.

Development of transparent electrodynamic screens (EDS) printed on ultrathin flexible glass film substrates for retrofitting on solar panels and solar mirrors to perform self cleaning function is reviewed. Large-scale solar plants are generally installed in semi-arid and desert areas where dust layers build up on solar collectors causes major energy-yield loss. Maintaining designed plant capacities requires more than 90% reflectivity for CSP mirrors and 90% transmission efficiency for PV modules; solar collectors must therefore be cleaned at a frequency depending on the rate of dust deposition. Scarcity of water in these regions requires a cleaning method that drastically reduces or eliminates water and the associated labor costs for high efficiency operation of large-scale solar plants. An EDS film consists of rows of interdigitated, transparent conducting parallel electrodes embedded within a flexible ultrathin glass film and an optically clear adhesive film used for retrofitting the film on the surface of solar collectors. When phased voltage pulses activate the electrodes, the dust particles are first electrostatically charged, then repelled and removed from the surface of the solar collectors by Coulomb force, restoring transmission efficiency greater than 90%. The electrodes of EDS are either made from silver nanowire or another conductive transparent material printed on a highly transparent, ultrathin (100-μm thick), flexible borosilicate glass film. Applications of different conducting transparent electrodes and methods of printing are reviewed for optimizing self-cleaning function of solar panels and mirrors.

Carbon nanotube arrays were grown in the presence of an applied mechanical stress (30 min, 60 mN/mm2 mechanical pressure) and dispersed in aqueous solution (0.08 - 2.3 mm2/mL). Optical (450-950 nm) transmission and right angle scattering measurements were performed on these dispersions and on an analogous set of conventional (non-stressed) carbon nanotubes. Results show similar transmission behavior and different right angle scattering dependence on concentration for stress-grown and conventional carbon nanotubes. This investigation provides the first evidence of differentiation between stress-grown and conventional carbon nanotubes in the optical regime, suggesting a point of departure for future applications.

Commercial off-the-shelf (COTS) electronics are generally not specificallydesigned to perform in extremely transient high impact scenarios. This researchfocused on the development of a silver-decorated carbon black-based polymericnanocomposite with properties such as high conductivity, flexibility, and shockabsorbency. Polymeric rubber materials are generally very flexible and shockabsorbing, however, most polymeric materials are electrical insulators. Thedispersion of the silver-decorated carbon black into the polymeric matrix couldsignificantly improve the electrical conductivity. The processing andfabrication of Ag-CB (silver-carbon black)/Epoxy (thermosetting epoxy polymer)and Ag-CB/TPU (thermoplastic polyurethane) will be reported. Both Ag-CB/Epoxyand Ag-CB/TPU mixtures with solvents showed the shear-thinning behavior, whichwas an important characteristic for direct printing of traces and AdditiveManufacturing (AM). The mechanical properties of the nanocomposites weremeasured using Dynamic Mechanical Analysis (DMA) over a wide range oftemperatures. These nanocomposite materials were also successfully used to printflexible circuits using a 3D-printing machine. The electrical resistance changefor the Ag-CB/Epoxy on polydimethylsiloxane (PDMS) and Ag-CB/TPU on PDMS understrain was studied, and the results will be discussed.

Both synthesis and photocatalytic potential of an innovative catalyst-powder type composite material based on the Zn or/and ZnO dispersed in a matrix of amorphous-carbon have been investigated. Zn/ZnO/amorphous-carbon nanostructured-matrix composite was prepared by partial pyrolysis method based on the Pechini method. The amorphous character of composite was characterized X-ray diffraction, while chemical bond investigated by infrared spectroscopy. The photocatalytic activity directed to the degradation of the phenol red dye of small fraction of commercial ZnO, Zn/C and Zn/ZnO/C composites were evaluated as a function of the degradation reaction of the phenol red dye, in the alkaline medium pH = 9. A mass concentration of 1:10,000 was selected being considered 30 and 150 min of reaction A comparison between photocatalytic activity showed that the degradation rate of phenol red dye is more efficient at both ZnO/Zn/C and Zn/C amorphous composites when compared to the pristine ZnO. The efficiency obeys the following order C/Zn ≥ C/ZnO/Zn > commercial ZnO with conversion equal to 70% for C/Zn and C/ZnO/Zn, while for the ZnO is around 55%. The kinetic of degradation is discussed.

Cleanliness is a prerequisite for obtaining economically feasible yield levels in the semiconductor industry. For the next generation of lithographic equipment, EUV lithography, the size of yield-loss inducing particles for the masks will be smaller than 20 nm. Consequently, equipment for handling EUV masks should not add particles larger than 20 nm. Detection methods for 20 nm particles on large area surfaces are needed to qualify the equipment for cleanliness. Detection of 20 nm particles is extremely challenging, not only because of the particle size, but also because of the large surface area and limited available time.

In 2002 TNO developed the RapidNano, a platform that is capable of detecting nanoparticles on flat substrates. Over the last decade, the smallest detectable particle size was decreased while the inspection rate was increased. This effort has led to a stable and affordable detection platform that is capable of inspecting the full surface of a mask blank.

The core of RapidNano is a dark-field imaging technique. Every substrate type has a typical background characteristic, which strongly affects the size of the smallest detectable particle. The noise level is induced by the speckle generated by the surface roughness of the mask. The signal-to-noise ratio can be improved by illuminating the inspection area from nine different angles. This improvement was first shown on test bench level and then applied in the RapidNano3. The RapidNano3 is capable of detecting 42nm latex sphere equivalents (and larger) on silicon surfaces. RapidNano4, the next generation, will use 193 nm light and the same nine angle illumination mode. Camera sensitivity and available laser power determine the achievable throughput. Therefore, special care was given to the optical design, particularly the optical path. With RapidNano4, TNO will push the detection limit of defects on EUV blanks to below 20nm.

Solar thermophotovoltaic (STPV) systems convert sunlight into electricity via thermal radiation. The efficiency of this process depends critically on both the selective absorber and the selective emitter, which are controlled by both the materials and the photonic design. For high concentration solar TPV applications, 2D photonic crystals (PhCs) made of refractory metals such as tungsten have demonstrated promising results. For even higher performance, we propose two photonic crystal-based designs to both collect solar heat and reradiate above-gap photons. First, a PhC selective structure (IPSS), which combines 2D photonic crystals and filters into a single device. Second, an Er-Yb-Tm co-doped fused silica coated with a 17-bilayer structure also offers significant selectivity with greater ease of fabrication. Finite difference time domain (FDTD) and rigorous coupled wave analysis (RCWA) simulations show that both can significantly suppress sub-bandgap photons. This increases sunlight-to-electricity conversion for photonic crystal-based emitters above 24.3% at 100 suns concentration or 27% at 1000 suns concentration using a Ga0.42In0.58As PV diode with a bandgap of 0.7 eV (nearly lattice-matched to InP).

In this manuscript a simple approach is discussed to fabricate uniform periodic surface structures on semiconductor surfaces by femtosecond laser irradiation for surface-enhanced Raman spectroscopy (SERS) applications. Gold films having different thickness are first deposited on semiconductor silicon (Si) surfaces and then periodic surface structures are fabricated by femtosecond laser irradiation. The periodic structures are observed to be uniform over a large area with chain type structure formation of gold and Si. We have studied the formation of these surface structures on Si surface by having different thickness gold films deposited on Si substrates. This approach of the fabrication of surface structures with the assistance of gold film is found to help in local field enhancement and hence work as suitable substrate for the SERS experiments. The conditions for achieving high enhancement factor in SERS with different gold film thicknesses are explored in detail. We also present here the formation of low frequency ripples on Silicon (Si) and high frequency as well as low frequency ripples on titanium (Ti) surface in air and water environments by irradiation with fs laser pulses. Different morphologies were observed on Ti surface depending upon the laser irradiation parameters and the surrounding dielectric medium.

AlN thin film structures have many useful and practical piezoelectric and pyroelectric properties. The potential enhancement of the AlN piezo- and pyroelectric constants allows it to compete with more commonly used materials. For example, combination of AlN with ScN leads to new structural, electronic, and mechanical characteristics, which have been reported to substantially enhance the piezoelectric coefficients in solid-solution AlN-ScN compounds, compared to a pure AlN-phase material.

In our work, we demonstrate that an analogous alloying approach results in considerable enhancement of the pyroelectric properties of AlN - ScN composites. Thin films of ScN, AlN and Al1-x ScxN (x = 0 – 1.0) were deposited on silicon (004) substrates using dual reactive sputtering in Ar/N2 atmosphere from Sc and Al targets. The deposited films were studied and compared using x-ray diffraction, XPS, SEM, and pyroelectric characterization. An up to 25% enhancement was observed in the pyroelectric coefficient (Pc = 0.9 µC /m2K) for Sc1-x Alx N thin films structures in comparison to pure AlN thin films (Pc = 0.71 µC/m2K). The obtained results suggest that Al1-x ScxN films could be a promising novel pyroelectric material and might be suitable for use in uncooled IR detectors.

By reducing the number of dimensions that light can propagate in from three down to two, one may gain control over the characteristics of propagation. This control can allow for “Stopped Light” (SL), where wavepackets of light are slowed down to a zero group velocity. This is achieved by designing planar metal-dielectric structures that are stacked in one dimension allowing for waveguide modes in the other two, and engineering the dispersion relation of these structures. Stopped light structures can be further optimized to reduce their dispersion and increase the number of spatial frequencies supported, which allows for confinement of electromagnetic energy over volumes smaller than the diffraction limit over fixed regions in space. If this electromagnetic energy is confined over a region that provides gain, the question arises, can amplification of this light energy occur? and indeed can a regime of lasing be entered into? We show that stopped light lasing is indeed possible, despite there being no resonant cavity in 2d to confine the light, and explore the properties of this new type of laser.