A system combining photovoltaic (PV) and solar thermal approaches is designed to convert solar energy to electricity with high efficiency across the full solar spectrum. Concentrated solar spectrum is split into two parts: PV and thermal. The PV part of the spectrum is further split into several subbands directed to bandgap appropriate solar cells on an inexpensive Si substrate. Epitaxial Ge on Si is used as a virtual substrate for III-V semiconductor growth. At long and very short wavelengths where PV efficiency is low, solar radiation is directed to a high temperature thermal storage tank for electricity generation using heat engines. The potential of using PV waste heat due to thermalization of high energy photoelectrons for electricity generation is also investigated. Detailed optical and thermal analysis show that with optimized design and neglecting optical component loss, system power conversion efficiency can reach 56%, including more than 16% absolute contribution from thermal storage.

A low thermal budget process for back-end compatible PCMO based RRAM cell is essential for 3D stacked memory. In this paper, we investigate two strategies to engineer low thermal budget processing for bipolar switching - (i) deposition engineering i.e. based on deposition temperature and oxygen partial pressure, (ii) post deposition anneal i.e. based on inert anneal of room temperature deposited PCMO film.. We demonstrate that both deposition and anneal shows a transition temperature above which bipolar switching is realized. Oxygen partial pressure is a key deposition process parameter. As oxygen partial pressure is reduced memory window increases, however beyond an optimal O2 partial pressure, unipolar switching is observed. Inert anneal is more effective in thermal budget reduction as N2/550°C/2min anneal has same memory performance as 650°C/2hour deposition process.

Recent developments on the use of the piezoelectric effect in ZnO nanorod-based p-n junctions for energy harvesting applications are presented. Two types of junctions are used. The first is a hybrid p-n device combining the semiconducting polymer poly(3,4-ethylene-dioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) with ZnO nanorods. The second type of junction is an all-inorganic junction between n-type ZnO nanorods and p-type CuSCN. It is shown that both these diodes can be produced on flexible plastic substrates, which generate a voltage output when bent. The voltage output of the ZnO/PEDOT:PSS diodes are measured across a range of resistive loads while bending to find a maximum power point of 12 μWcm-2 at 4 kΩ. It is shown that a voltage output is also generated when this structure is vibrated acoustically. The ZnO/CuSCN diode is sensitized to sunlight with a Ru-based dye to form a photovoltaic device. It is shown that the device efficiency can be increased by application of acoustic vibrations. This is attributed to the electric field generated by the piezoelectric effect in ZnO affecting the charge-carrier recombination at the ZnO surface.

Gold (Au) nanoparticles were synthesized and deposited on the perovskite SrTiO3 (STO) via a one-step solution plasma sputter deposition (SPSD) without any reducing reagents at ambient condition. Good dispersion of the Au nanoparticles deposited on the STO surface was clearly observed. The synthesized Au nanoparticles were well-crystallized with a spherical shape and preferably exhibited multiply twinned structure. An average diameter of Au nanoparicles was estimated to be 6.1 ± 1.4 nm by transmission electron microscopy. Enhanced photocatalytic activity was found for the Au-STO when compared to the pure STO, as investigated from the degradation of methylene blue solution under ultraviolet and visible light irradiation. The SPSD seems to be a rapid and facile approach to prepare the Au nanoparticles supported on the metal oxide for photocatalytic applications.

Visible-light photocatalytic property of TiO2 / WO3 / FTO multi-layer structure was investigated. In this structure, the visible-light absorption takes place in the WO3 layer, and generated electrons and holes diffuse into the FTO and TiO2 layers, respectively. The holes diffused into the valence band of the TiO2 layer produce the hydroxyl radicals due to oxidation of H2O and/or OH− adsorbed on the TiO2 surface. The FTO bottom layer, which acts as a scavenger of electrons, contributes to an effective charge separation. As a result, the visible-light photocatalysis is enhanced in this structure.

The effect of Re addition on microstructure and hardness of the Ni3Al (L12) and Ni3V (D022) dual two-phase intermetallic alloys was investigated as functions of alloying (substituting) method of Re and aging condition (temperature and time). Re was added to the base alloy composition by three methods: Re was substituted for Ni, Al and V, respectively. The Re-added alloys were solution-treated at 1553 K and then aged at lower temperatures of 1123 K-1248 K. Apparent age hardening occurred in the alloy where Re was substituted for Ni while no age hardening was observed in the alloys where Re was substituted for Al or V. In the case of the latter two alloys, the hardness was unchanged or reduced with a progression of aging time. These results were discussed in terms of phase separation and ordering in the channel region, and hardening due to Re-rich phase precipitation.

We report the growth of single crystals by a flux method in ambient pressure and tri-axial orientation under modulated rotation magnetic fields (MRFs) on REBa2Cu4O8 (RE124, RE; rare earth elements) compounds. RE124 crystals were grown for RE = Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Yb through appropriate choice of source compounds. All the obtained RE124 powders were tri-axially aligned in MRF of 10T, whereas magnetization axes depended on the type of RE. Moreover, it was found from the changes in the degrees of c-axis and inplane orientation that tri-axial magnetic anisotropies of RE124 also depended on the type of RE. This indicates that it appropriate choice of RE is important for the fabrication of tri-axial oriented ceramics in lower magnetic field conditions.

The development of a novel multidisciplinary Nanoscience Concentration Certificate Program (NCCP) at University of Texas at Brownsville (UTB) is reported. The NCCP intended to prepare undergraduate students to emerging nanotechnology markets, industry trends, cutting edge research and technology developments. The rationale for the NCCP is to integrate and expand nanotechnology-relevant courses within a comprehensive curriculum. The established certificate program includes the following seven new upper level undergraduate courses: (i) Introduction to Nanoscience, (ii) Engineering of Nanomaterials, (iii) Nanofabrication and Nanoelectronics, (iv) Introduction to Bio-Nanotechnology, (v) Environmental Nanotechnology, (vi) NanoOptics, (vii) Capstone Design. This program is designed to address the needs for a multidisciplinary undergraduate education at the UTB, which extends beyond traditional courses within science and engineering disciplines. The designed courses will expose students to the nanotechnology areas as part of integration of nanoscience in UTB’s undergraduate programs. To complete the NCCP and receive a Certificate in Nanoscience and Nanotechnology, students must complete 12 credit-hours of NCCP courses. Our ultimate goal is to establish and maintain at UTB a practical, modular, scalable, transferrable and implementable educational STEM platform in nano-sciences, engineering and nanotechnology. The goal of this paper is to examine an instructional technique for Introduction to Nanoscience course as an example for promoting student understanding of scientific concepts and explanations by using combines teaching learning activities and research oriented strategies.

The motivation of this study is to provide answers to questions rising with 3D stacking of semiconductor chips. This includes the development and validation of concepts for 1) Through Silicon Via (TSV) formation, 2) metal layer build-up, 3) various types of assembly and packaging concepts and methods, as well as 4) process characterization.

The investigations discussed here have been conducted on test wafer (ATEC2) developed by Fraunhofer IZM-ASSID. This design contains dedicated test structures which have been implemented to enable different unit processes and allows easy physical analysis. One of those test structures has been used to study the impact of the TSV density on the stress generation after TSV fill, anneal and CMP (chemical mechanical planarization) including copper protrusion and planarization behaviour. First results of the interaction between different TSV plating bath chemicals, anneal procedures and wafer bow obtained using test wafer ATEC1 were already presented during ICPT 2011.

The process flow applied in this investigation was (1) TSV filling by electro-plating, (2) anneal, and (3) CMP. Physical analysis including inline metrology has been conducted between all process steps.

The test wafers processed were divided into two groups according to the utilized copper plating bath chemistries. The copper TSV metallization was carried out by electro-chemical deposition in plating bath chemicals from two different suppliers. 3D microscope inspection was conducted for surface analysis. After TSV filling the copper surface shows protrusion on top of the TSVs and ring-shaped non-uniformities around the filled TSV. These structures were analysed after each step of the process flow.

An anneal process was conducted after TSV plating. The annealing temperature was varied to investigate its influence on the material properties (protrusion caused by copper recrystallization) and the dip behaviour. The experiments were accomplished at 250 degree Celsius and above.

Afterwards all test samples were processed by CMP with different selective slurries and analysed by AFM (atomic force microscopy) and optical methods. Bow and warpage measurements of the test wafers taken after each process step have been analysed.

Our investigation has demonstrated the influence of the additives on the behaviour of different plating bath chemistries during temperature treatment (copper recrystallization) and therefore also the planarization behaviour after CMP.

We report the demonstration of low power phase change memory (PCM) by forming thin self-assembled SiOx nanostructures between Ge2Sb2Te5 (GST) and a TiN heater layer utilizing a block copolymer (BCP) self-assembly technology. The reset current was decreased about three-fold as fill factor, which is the occupying area fraction of self-assembled SiOx nanostructures on a TiN heater layer, increased to 75.3%. The electro-thermal simulation shows the better heat efficiency due to the nano-patterned insulating oxide.

In France, nuclear glass canisters arising from spent fuel reprocessing are expected to be disposed in a deep geological repository using a multi-barrier concept (glass/canister/steel overpack and claystone). In this context, glass - iron or corrosion products interactions were investigated in a clayey environment to better understand the mechanisms and driving forces controlling the glass alteration. Integrated experiments involving glass - metallic iron or magnetite - clay stacks were run at laboratory scale in anoxic conditions for two years. The interfaces were characterized by a multiscale approach using SEM, TEM, EDX and STXM at the SLS Synchrotron. Characterization of glass alteration patterns on cross sections revealed various morphologies or microstructures and an increase of the glass alteration with the proximity between the glass and the source of iron (metallic iron or magnetite) due to the consumption of the silica coming from the glass alteration. In case of magnetite, the silica consumption is mainly driven by a sorption of silica onto the magnetite. For experiments containing metallic iron, the silica consumption seems to be strongly driven by silicates precipitation including Fe and Fe/Mg when the Fe is not enough available. Moreover, in addition to Fe-silicates observed at the surface of the gel layers, iron is incorporated within the gel probably as nanosized precipitates of Fe-silicates which could affect its physical and chemical properties. Those results highlighted the impact of the distance between glass and iron source and the nature of the iron source which drive the process consuming the silica coming from the glass alteration.

Our ability to fabricate multipodal and multilayer TiO2 nanotube arrays enables us to increase performance and functionality in light harvesting devices such as excitonic solar cells and photocatalysts. Using a combination of simulations and experiments, we show that multilayer nanotube arrays enable photon management in the active toward enhancing the absorption and utilization of incident light. We show that the simultaneous utilization of TiO2 nanotubes with large (∼450 nm) and small (∼80 nm) diameters in stacked multilayer films increased light absorption and photocurrent in solar cells. Such enhanced light absorption is particularly desirable in the near-infrared region of the solar spectrum in which most excitonic solar cells suffer from poor quantum efficiencies and for blue photons at the TiO2 band-edge where significant room exists for improvement of photocatalytic quantum yields. Under AM 1.5 one sun illumination, multilayer nanotube arrays afforded us an approximately 20% improvement in photocurrent over single layer nanotube array films of the same thickness for N-719 sensitized liquid junction solar cells. Also, the possibility of multipodal TiO2 nanotube growth with different electrolyte recipes is presented.

We present a simple, novel procedure to selectively deposit gold nanoparticles using pure water. It enables patterning of nanoparticle monolayers with a remarkably high degree of selectivity on flat as well as microstructured oxide surfaces. We demonstrate that water molecules form a thin ‘capping’ layer on exposed thiol molecules within the mercaptan self-assembled layer. This reversible capping of water molecules locally ‘deactivates’ the thiol groups, therewith inhibiting the binding of metallic gold nanoparticles to these specific areas. In addition, we show that this amazing role of water molecules can be used to selectively metalize the patterned gold nanoparticle arrays. Employing an electroless seeded growth process, the isolated seeds are enlarged past the percolation threshold to deposit conducting metal layers.

This paper summarizes some recent advances for electrochromic and thermochromic fenestration. For the former application, we consider a polymer-laminated construction and show that the addition of nanoparticles to the electrolyte can enhance its ionic conductivity (with fumed silica) and quench the near-infrared transmittance which transmits solar energy but is not important for visible light (with ITO nanoparticles). Regarding thermochromics, we discuss recent experimental and theoretical work on Mg-doped VO2, where the doping lowers the luminous absorptance, and on measurements applied to Al2O3-coated VO2 with good stability with regard to high-temperature treatment.

III-nitrides (III-Ns) semiconductors and their alloys have shown in the last few years high potential for interesting applications in photonics and electronics. III-Ns based heterostructures (HS) have been under wide investigation for different applications such as high frequency transistors, ultraviolet photodetector, light emitters etc. In the present contribution a III-Ns based heterostructure, in particular the nearly lattice matched Al1-xInxN/AlN/GaN HS will be discussed. The formation of the two dimensional electron gas (2DEG), its origin, its electrical and optical properties, the confined subband states in the well and its effect on the conduction mechanisms have been studied. Moreover, extended defects and their effect on the degradation phenomena of the 2DEG have been analyzed.

The poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based ferroelectric and relaxor materials have been proved to be good electrocaloric (EC) materials. To further enhance the EC effect in ferroelectric relaxor terpolymer poly(vinylidene fluoride–trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), composites such as polymer-polymer blends and nanocomposites filled with inorganic nanoparticles are fabricated and investigated. It is found that the addition of small amount of filler (such as P(VDF-TrFE) or nano-ZrO2) can increase terpolymer’s crystallinity and enhance its relaxor behavior through interface couplings. The increased crystallinity and enhanced relaxor behavior together result in enhanced electrocaloric effect. The results demonstrate the promise of composite approaches in tailoring and enhancing ECE in the relaxor terpolymers.

Isotropic and anisotropic conductive carbon particles, carbon black (CB) and vapor grown carbon fiber (VGCF), were incorporated into a Lithium Titanate (LTO) battery anode material composition, and their effect on conductivity and electrochemical properties investigated. Nanocomposite electrodes comprised of LTO, polyvinyldine floride (PVDF) and as little as 5 wt% VGCF are reported to manifest more than one order of magnitude enhancement in conductivity over their CB counterparts. VGCF-based anodes are also found to exhibit more stable voltage discharge profiles and as much as 20% improvement in capacity retention during extended electrochemical cycling at charge/discharge rates as high as 2.625 A/g (15 C). Remarkably, we find that the benefits of VGCF relative to CB conductivity aids diminish at higher particle loadings and that a LTO anode formulation containing 5 wt% CB | 5 wt% VGCF yields optimal capacity retention. At 5C, this composite system outperformed both the 10 wt% VGCF and 10 wt% CB electrode systems by delivering 20% higher capacity during extended charge/discharge cycling. We explain this finding in terms of two synergetic effects: enhanced electrode conductivity facilitated by incorporation of a percolated network of anisotropic VGCF particles; and shorter transport distances between the insulative LTO and high surface area CB.

Many advances in nanomaterials synthesis have been recorded during the last 30 years. Bacterial cellulose (BC) produced by bacteria belonging to the genera Acetobacter, Rhizobium, Agrobacterium, and Sarcina is acquiring major importance as one of many eco-friendly materials with great potential in the biomedical field. The shape of BC bulk is sensitive to the container shape and incubation conditions such as agitation, carbon source, rate of oxygenation, electromagnetic radiation, temperature, and pH. The challenge is to control the dimension and the final shape of biosynthesized cellulose, by the optimization of culture conditions. The production of 3D structures based on BC is important for many industrial and biomedical applications such as paper and textile industries, biological implants, burn dressing material, and scaffolds for tissue regeneration. In our work, wild strains of Acetobacter spp. were isolated from homemade vinegar then purified and used for cellulose production. Four media of different initial viscosity were used. Cultures were performed under static conditions at 29°C, in darkness. The dimensions and texture of obtained bacterial cellulose nanofibers were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) showed that the biosynthesized material has a cellulose I crystalline phase characterized by three crystal planes. fourrier transform infrared spectroscopy (FTIR) data confirmed the chemical nature of the fibers. Thermo-gravimetric analysis (TGA) showed that BC preserves a relatively superior non-degradable fraction compared to microcrystalline cellulose.

The conventional method to fabricate porous silicon with n-type substrates requires light assisted generation of holes used in the electrochemical reaction. Recently, two different methods have been proposed to fabricate some similar structures: Hall effect [1] and lateral electrical field [2]. Hall effect assisted etching involves the application of a perpendicular electric and magnetic field to achieve the concentration of holes at the HF/silicon interface to assist the electrochemical reaction, while the other involves the application of a lateral electrical field across the silicon wafer. In this work, the electrochemical etching of high resistivity n-type silicon wafers under the combined effect of magnetic and lateral electrical field to produce photoluminescent macroporous structures under dark conditions, is reported. A lateral gradient in pore sizes as well as in light emission is observed. Optical and structural properties were studied for their possible applications as a biosensor.

Most chemical mechanical polishing (CMP) researchers assume that the polishing occurs in the mixed-lubrication regime, where the applied load on the wafer is supported by the hydrodynamic slurry pressure and the contact stress generated during the pad-wafer contact. Consequently, the particle augmented mixed lubrication (PAML) approach has been employed as an extremely high-fidelity asperity-scale mixed-lubrication CMP model in the past. Recently, a more computationally efficient PAML approach, PAML-lite, which considers the slurry’s fluid and particle dynamics, the pad/wafer contact mechanics, and the resulting material removal, was introduced. The current work presents the PAML-lite framework with the isothermal assumption relaxed. As a result, wafer-scale interfacial temperatures during CMP can be predicted by considering asperity heating and dissipation of the heat into the solid and fluid media in the sliding contact.