ITO samples were sputtered at room temperature by ion assisted dual ion beam sputtering using atomic or molecular oxygen. The electrical properties appear to depend on the oxygen flow rate during deposition and the resistivity decreases for samples sputtered at a higher oxygen flow rate (1-5 sccm). The resistivity is lowest at an oxygen flow rate of 4 sccm. The average absorption in the visible part of the spectrum also decreases as a function of the oxygen flow rate and is lower for samples sputtered with atomic oxygen. The figure of merit, i.e. the ratio of the conductivity versus the average absorption in the visible range, increases for higher oxygen flow rates and is typically 20-60% higher for samples sputtered using an atomic oxygen assist beam.

One of the main problems encountered by curators and conservators in charge of metallic collections from Historical Heritage is related to their long-term conservation, since metallic artifacts undergo corrosion phenomena, which are the result of the interaction between the metal and its environment. The use of rust converters and microcrystalline waxes can be an ecological alternative to the traditional and more aggressive conservation techniques. Although the mechanism of action of these compounds is not clear, it is assumed that they react with iron oxides and generate new compounds that may have a passivation effect on the metallic surface. This paper proposes to show how simple electrochemical techniques can be used as an efficient tool to contribute to the diagnosis of the conservation state of cannon balls and to monitor the restoration treatment. The objective of the present work is to evaluate the effectiveness of a rust converter based on tannins and phosphoric acid, and one microcrystalline wax applied on cannon balls samples exposed to a marine atmosphere. The protection properties of the oxide or conversion layer are evaluated by electrochemical impedance spectroscopy (EIS) technique. The results obtained suggest that the use of the rust converter and microcrystalline wax protects the cannon balls, even though its effect is less evident when the deterioration degree is larger.

Nanoisland films have been grown via incongruent evaporation films. The basis of incongruent evaporation growth method was worked out. Samples surface morphology has been studied by atomic force microscopy. The surface density and characteristic dimensions of the islands have been shown.

Although 3C-SiC has a narrower bandgap than 4H-SiC, it is the only SiC polytype that can be grown directly over large area silicon substrates. It has the potential to provide a more economical choice than 4H-SiC for intermediate power devices, such as inverters for electric vehicles. To fabricate a vertical device on 3C-SiC, the Si substrate is usually removed either by etching or polishing. Neither of these processes is economical nor efficient. In this paper we propose a lateral Schottky diode design for 3C-SiC on Si structure. 2D finite element simulations using ATLAS showed that a breakdown voltage beyond 1200 V can be achieved with a 4 μm thick epilayer. Physical models used for 3C-SiC/Si power devices simulations are introduced. Advantages of lateral 3C-SiC/Si diodes over free standing 3C-SiC are also discussed.

Stress control using AlN/GaN superlattices (SLs) for epitaxy of GaN on 200 mm Si (111) substrates is reported. Crack-free 2 μm GaN layers were grown over structures containing 50 to 100 pairs of 3-5 nm AlN/10-30 nm GaN SLs. Compressive and tensile stress can be precisely adjusted by changing the thickness of the AlN and GaN layers in the SLs. For a constant period thickness, the effects of growth conditions, such as growth rate of GaN, V/III ratio during AlN growth, and growth temperature, on wafer stress were investigated.

This investigation is a comprehensive study of the effect of ammonium acetate on the electrical, optical, morphology and microstructure of CdS thin films grown by Chemical Bath Deposition method (CBD). Two sets of CdS thin films (A and B) were deposited on glass substrates at 60°C for 60 min. The films were deposited using chemical bath solution that consists of cadmium acetate, ammonium hydroxide, and thiourea. However, ammonium acetate was added into the chemical bath used to deposit set (B), where ammonium acetate was eliminated from bath solution used to deposit set (A). The films’ morphology was examined by Field Emission Scanning Electron Microscopy (FE-SEM), whereas, the chemical composition was investigated by Electron Probe Micro-Analyzer (EPMA). The X-Ray Diffraction (XRD) θ/2θ technique was applied to study the structure of the films. Atomic Force Microscopy (AFM) was used to measure the average surface roughness of the films, and Dektak Profilometer was used to determine the CdS films thickness. The optical and electrical properties for the films were determined using UV-Vis-NIR Spectrometer, and the Hall Effect technique, respectively. The highest carrier mobility was obtained for the films deposited in an ammonium acetate free bath. However, both films were polycrystalline with hexagonal structure exhibiting a tendency toward <002> texture, that increase with increasing the pH value of the chemical bath.

Charge generation and transport in CH3NH3PbI3-xClx based mesostructured solar cells are investigated. Time correlated single photon counting analysis proves highly efficient charge generation and provides insights on the structural properties of perovskite films. Photoinduced absorption and transient photovoltage analyses depict a double charge recombination dynamics suggesting the existence of two complementary paths for electron transport, involving either TiO2 and perovskite matrixes. Stark spectroscopy, a powerful tool allowing interface-sensitive analysis, is employed to prove the existence of oriented permanent dipoles, consistent with the hypothesis of an ordered perovskite layer close to the oxide surface. This evidence is also confirmed by first principle DFT calculations. The existence of a structural order, promoted by specific local interactions, could be one of the decisive reasons for highly efficient carriers transport within perovskite films.

An excellent candidate for an earth abundant absorber material is WSe2 which can be directly grown as a p-type semiconductor with a band gap near 1.4 eV. In this work we present the structural, optical, and electrical properties of thin film WSe2 grown via the selenization of sputter deposited tungsten films. We will show that highly textured films with an optical band gap in range of 1.4 eV, and absorption coefficients greater than 105/cm across the visible spectrum can be easily achieved. In addition we will present Hall Effect and carrier density measurements as well, where will show densities in the 1017cm-3 range and p-type Hall mobilities greater than 10 cm2/V-s range can be obtained. We employ these results to numerically simulate solar cells based on this material, where we will show efficiencies greater than 20% are possible.

Bacteriophytochromes (BphPs) are red-light photoreceptors found in photosynthetic and nonphotosynthetic bacteria that have been recently engineered as infrared fluorescent tissue markers. Light-induced, global structural changes are proposed to originate within their covalently bound biliverdin chromophore and propagate through the protein. Classical BphPs undergo reversible photoconversion between spectrally distinct light absorbing states, red (Pr) and far-red (Pfr), respectively. RpBph3 (P3), from Rhodopseudomonas palustris, photoconverts between a Pr and a unique near-red (Pnr) light-absorbing state. Due to size and photosensitivity of BphPs, structures of the intact proteins have not been resolved by nuclear magnetic resonance and/or X-ray crystallography. Therefore, structural details about the light and dark-adapted structures of the intact BphPs are not well understood at the molecular level. We have utilized fluid cell atomic force microscopy (AFM) to investigate the domain structure of intact P3 in its light-adapted state (Pnr). By varying the concentration of the protein, deposition time, and the ionic strength of the buffer, the aggregation of P3 on a mica surface can be controlled and single dimers may be observed in a biologically relevant media. Domain resolution has been achieved for several orientations of the dimer on the surface. The structural dimensions of the dimer have been compared to a modeled BphP in its intact form generated using PyMOL software. AFM experiments are currently underway to analyze the dark-adapted state (Pr) of P3 in order to observe the anticipated structural changes. Ultimately, the goal is to use AFM and other surface analytical methods such as scanning tunneling microscopy and electron microscopy to gain new insight into the unique photochemistry of P3.

The electromigration lifetimes of a very large quantity of passivated electroplated Au interconnects were measured utilizing high-resolution in-situ resistance monitoring equipment. Application of moderate accelerated stress conditions with current density limited to 2 MA/cm2 and oven temperatures in the range of 300°C to 375°C prevented large Joule-heated temperature gradients and electrical overstress failures. A Joule-heated Au film temperature increase of 10°C on average was determined from measured temperature coefficients of resistance (TCRs). A failure criterion of 50% resistance degradation was selected to avoid thermal runaway and catastrophic open circuit failures. All Au lifetime distributions followed log-normal statistics. An activation energy of 0.80 ± 0.05 eV was measured from constant-current electromigration tests at multiple temperatures. A current density exponent of 1.91 ± 0.03 was extracted from multiple current densities at a single constant temperature.

Millions of medical implants and devices (e.g., screws, plates, and pins) are used each year worldwide in surgery, and traditionally the components have been limited to permanent metals (e.g., stainless steel, titanium alloys) and polyester-based absorbable polymers. Because of clinical problems associated with these traditional materials, a novel class of biodegradable metallic materials, i.e., magnesium-based alloys, attracted great attention and clinical interests. Magnesium (Mg) is particularly attractive for load-bearing orthopedic applications because it has comparable modulus and strength to cortical bone. Controlling the interface of Mg with the biological environment, however, is the key challenge that currently limits this biodegradable metal for broad applications in medical devices and implants. This paper will particularly focus on creating nanostructured interface between the biodegradable metallic implant and surrounding tissue for the dual purposes of (1) mediating the degradation of the metallic implants and (2) simultaneously enhancing bone tissue regeneration and integration. Nanophase hydroxyapatite (nHA) is an excellent candidate as a coating material due to its osteoconductivity that has been widely reported. Applying nHA coatings or nHA containing composite coatings on Mg alloys is therefore promising in serving the needed dual functions. The composite of nHA and poly(lactic-co-glycolic acid) (PLGA) as a dual functional interface provides additional benefits for medical implant applications. Specifically, the polymer phase promotes interfacial adhesion between the nHA and Mg, and the degradation products of PLGA and Mg neutralize each other. Our results indicate that nHA and nHA/PLGA coatings slow down Mg degradation rate and enhance adhesion of bone marrow stromal cells, thus promising as the next-generation multifunctional implant materials. Further optimization of the coatings and their interfacial properties are still needed to bring them into clinical applications.

Dielectrophoresis (DEP) approach was employed to achieve highly aligned multi-walled carbon nanotubes (MWCNTs) within the gelatin methacrylate (GelMA) hydrogels in a facile, rapid, inexpensive, and reproducible manner. This approach enabled us to make different CNTs alignments (e.g., vertical or horizontal alignments) within the GelMA hydrogel using different electrode designs or configurations. Anisotropically aligned GelMA-CNTs hydrogels showed considerably higher conductivity compared to randomly distributed CNTs dispersed in the GelMA hydrogel and the pristine and non-conductive GelMA hydrogel. Adding 0.3 mg/mL CNTs to the GelMA hydrogel led to a slight increase in the mechanical properties of the GelMA and made it to behave as a viscoelastic material. Therefore, it can be used as a suitable scaffold for soft tissues, such as skeletal muscle tissue. 3D microarrays of skeletal muscle myofibers were then fabricated based on the GelMA and GelMA-CNTs hydrogels and they were characterized in terms of gene expressions related to the muscle cell differentiation and contraction. Owing to high electrical conductivity of aligned GelMA-CNTs hydrogels, the engineered muscle tissues cultivated on these materials demonstrated superior maturation and functionality particularly after applying the electrical stimulation (voltage 8 V, frequency 1 Hz, and duration 10 ms for 2 days) compared to the corresponding tissues obtained on the pristine GelMA and randomly distributed CNTs within the GelMA hydrogel.

Single crystals of semiorganic nonlinear optical material Triglycine Sodium Halides(TGSH) have been grown from aqueous solution by slow evaporation technique at constant temperature. The powder X-ray diffraction of the grown crystals is recorded and indexed. Functional groups present in the samples are identified by FTIR spectral analysis. The optical absorption studies shows that the UV cut off wavelength is around 300nm and has a wide transparency window. The powder second harmonic generation efficiency of the crystals is measured by Kurtz and Perry powder technique using Nd:YAG laser and it is 1.5 times for Triglycine Sodium Chloride, 1.2 times for Triglycine Sodium Bromide and 1.4 times for Triglycine potassium Iodide crystals that of the standard KDP crystals. Triglycine Sodium halide crystals show very good stability under laser irradiation with no signs of decomposition. Laser damage threshold energy density of Triglycine Sodium Iodide is found to be 857 MW/cm2 and 540MW/cm2 for Triglycine Sodium Chloride crystals.

Recent discoveries have shown the presence of several shipwrecks and historical pieces submerged in the seacoast of the Yucatan Peninsula of Mexico. Within these remains, it is common to found objects manufactured in copper alloys that were part of the construction system of the vessel. For the present study, different surface analysis techniques were applied to tubular copper alloy objects collected in the wreck “El Tejas”. The metallographic study allowed us to know not only the microstructure but also features over its manufacturing technique, as an example of nineteenth-century handmade production. SEM, EDX and XRF techniques allowed us know the elemental composition and establish the mechanisms of degradation of the different copper alloys in the seabed and evaluated a preservation method that consist on removing chlorine compounds by cleaning with pressure steam of distilled water.

In the KBS-3 repository concept and safety analysis, the copper container with a cast iron insert plays a central role in assuring isolation of the waste from the surrounding during long periods of time. All processes that affect its stability are thoroughly analysed, including potential detrimental processes inside the canister. For this reason, an estimation of the helium produced during the long term decay of alpha emitters in the spent fuel is necessary to evaluate if the pressures generated inside can have consequences for the canister.

The spent nuclear fuel to be disposed of in Sweden is mainly LWR fuel. The maximum burn-up expected is 60 MWd/kg U for BWR and PWR. A small quantity of BWR MOX is expected to be stored with a maximum burn-up of 50 MWd/kg U.

This work has focused on carrying out calculations of the amounts of He generated during more than 1 million years in Swedish spent nuclear fuels with a benchmarking exercise by using both codes AMBER and Origen-ARP. The performance and agreement of the codes in the He generation from α-decay have been checked and validated against data reported in literature [1].

In the calculation of the maximal pressure inside the canister, the quantity of helium used to pre-pressurise the fuel rods has been accounted for. The pressure inside the canister due to He generation is at all times much lower than the hydrostatic pressure and/or the bentonite swelling pressure outside the canister.

The microwave-induced magnetoresistance oscillations are exhibited by the GaAs/AlGaAs two dimensional electron system (2DES) under microwave and terahertz photo-excitation at liquid helium temperatures. Such oscillations are presently understood in terms of various theories. In order to identify the relative physical contributions, we have concurrently examined magnetotransport and microwave reflection from the 2DES. For the reflection measurements, a sensitive microwave detector was assimilated into the standard experimental setup. Here, we correlate changes in reflection with the concurrent transport response of the photo-excited 2DES.

The understanding of the physical properties of hydrogels has been controversial because hydrogels inherently have a substantial amount of heterogeneities in their structures. In this study, we focused on one of the simplest heterogeneities, heterogeneous distribution of strand length, and investigated its influence on physical properties. We prepared Tetra-PEG gels with bimodal distribution in strand length (Tetra-PEG bimodal gels) by combining Tetra-PEG prepolymers with different molecular weights and measured the physical properties including elastic modulus and ultimate deformation ratio. The physical properties of Tetra-PEG bimodal gels were well described by the models for conventional Tetra-PEG gels with the average polymerization degrees between cross-links. We conclude that the mechanical properties of hydrogels that have heterogeneous distribution in strand length can be predicted from those of hydrogels with the average strand length in the range tested in this study.

As the conventional atomic force microscopy (AFM) uses a Cartesian coordinate system to scan sample and the probe has different characteristics in each direction, it is impossible to scan in arbitrary direction. Therefore, we present the AFM which is able to rotate its probe. The deflection of cantilever was measured using optical pickup head of DVD drive. For verifying the system feasibility, the multidirectional scanning of the standard sample was carried out. Also we presented the modified structure which includes aligner and mirror to enhance the performance.

Single-walled carbon nanotubes (SWCNTs) have attracted significant attention as building blocks for future nanoscale electronics due to their small size and unique electronic properties. However, current SWCNT production techniques generate a mixture of two types of nanotubes with divergent electrical behaviors due to structural variations. Some of the nanotubes act as metallic materials while others display semiconducting properties. This random mixture has prevented the realization of functional carbon nanotube-based nanoelectronics. Here, a method of purifying a continuous flow of semiconducting nanotubes from an initially random mixture of both metallic and semiconducting SWCNTs in suspension is presented. This purification uses A/C dielectrophoresis (DEP), and takes advantage of the large difference of the relative dielectric constants between metallic and semiconducting SWCNTs. Because of a difference in magnitude and opposite directions of a dielectrophoretic force imposed on the random SWCNT solution, metallic SWCNTs deposit onto an electrode while semiconducting SWCNTs remain in suspension [3]. A discussion of these techniques is presented, along with a dielectrophoretic force-utilized microfluidic lab-on-a-chip device that can accomplish purification of semiconducting nanoparticles at high processing rates. The effectiveness of the device is characterized using Raman spectroscopy analysis on separated samples.