La-doped ZrO2 thin films were grown by O3-based atomic layer deposition on III-V (GaAs, In0.15Ga0.85As) substrates. The direct oxide deposition and the insertion of a Ge passivation layer in between the oxide and the substrate are compared in terms of the resulting density of interface traps. An improved electrical quality of the Ge-passivated interfaces concerning the energy region close to the conduction band edge in the semiconductor band-gap is demonstrated through conductance maps at various temperatures and it is attributed to Ga-related interfacial defects.

Simple alkanedithiols exhibit the same molecular conductance whether measured in air, under vacuum or under liquids of different polarity. Here, we show that the presence of water ‘gates’ the conductance of a family of oligothiophene–containing molecular wires, and that the longer the oligothiophene, the larger is the effect; for the longest example studied, the molecular conductance is over two orders of magnitude larger in the presence of water, an unprecedented result suggesting that ambient water is a crucial factor to be taken into account when measuring single molecule conductances (SMC), or in the design of future molecular electronic devices. Theoretical investigation of electron transport through the molecules, using the ab initio non-equilibrium Green's function (SMEAGOL) method, shows that water molecules interact with the thiophene rings, shifting the transport resonances enough to increase greatly the SMC of the longer, more conjugated examples.

Infrared spectroscopy is used to monitor the evolution of CO2 (2330-2350 cm-1) and CO (2050-2200 cm-1) generated during thermal reduction of graphite oxide. The appearance of CO2 at low temperatures (≤200°C) is associated with oxygen removal in species such as anhydrides, esters, lactols, carboxylic acids and lactones either at the edges or in the distorted basal plane of the GO sheets. At higher temperatures (250°C-750°C), release of CO is observed and may be due to decomposition of CO2 or oxygen-containing species like ethers, carbonyls, phenols or quinones. Observation of these gases is possible in multilayer GO because they are trapped in between the interlayer spacing of GO stacks for a time sufficient for detection.

Incorporation of biophotonic components in artificial devices is an emerging trend in exploring biomimetic approaches for green technologies. In this study, highly efficient, nanoscaled light antenna structures from green photosynthetic bacteria, known as chlorosomes, comprised of bacteriochlorophyll-c pigment arrays that are stable in aqueous environments are studied in an electrochemical environment for their photoelectrogenic capacity. Biohybrid electrochemical cells containing chlorosomes coupled to the native bacterial photosynthetic apparatus have a higher dark charge storage density (at least 10-fold) than electrochemical cells with decoupled chlorosomes. Nevertheless, upon light stimulation, the charge storage density, also known as charge injection capacity, for both electrochemical systems increased the charge stored near the electrode. Decoupled chlorosome-based systems showed a light-intensity dose-dependent response reaching a maximum change of ˜300 nC/cm2 at near sunlight intensities (˜80-100mW/cm2). Chronoamperometric studies under light stimulation conditions confirmed the photo-induced effect. Current studies are focused on optimization of the electrode/chlorosome interfacial properties across various heterogeneous interfaces. Successful implementation of harvesting photo-energy using the chlorosome or its derivatives may lead to substantial innovations in current biophotonic technologies, such as biofuel cells and retinal prosthetics.

In this work we have studied transmission and scattering of light through hexagonally packed circular subwavelength holes in optically thin and thick metallic film. The gold nanohole arrays are fabricated on glass substrate by combining nanosphere lithography with dry-etching technique. We observed that the transmission resonances of the thin films are significantly different than that of the thick films due to the coupling of plasmons at metal/air and metal/glass interfaces. We also investigated the effect of the diameter and the periodicity on the transmission resonance by controlling the dry-etching time and the bead size used in lithography, respectively. Finally, we have looked at the spectral response of the fabricated structures in media with different refractive indexes for bio-sensing application.

Molecular dynamics methods have been used to study the conformation of ds-DNA on a gold surface for low surface coverage at the atomistic level. Each ds-DNA strand, which is attached to the [111] surface of gold with a -S(CH2)6- linker, is found to be nearly perpendicular to the surface and maintaining the Watson-Crick B-DNA conformation. The tilt angle between the ds-DNA and an axis normal to the gold surface is 7.3 (+/-) 2.2 degree. The concentration of counterions around the ds-DNA is increased by a factor of 1.8 relative to the bulk, which is significantly lower than in our previous simulations of ds-DNA at high surface coverage.

Fe0.1Sc0.9N with a thickness of ˜ 380 nm was grown on top of a ScN(001) buffer layer of ˜ 50 nm, grown on MgO(001) substrate by radio-frequency N-plasma molecular beam epitaxy (rf-MBE). The buffer layer was grown at TS ˜ 800 oC, whereas the Fe0.1Sc0.9N film was grown at TS ˜ 420 oC. In-situ reflection high-energy electron diffraction measurements show that the Fe0.1Sc0.9N film growth starts with a combination of spotty and streaky pattern [indicative of a combination of smooth and rough surface]. After ˜ 10 minutes of growth, the pattern converts to a spotty one [indicative of a rough surface]. Towards the end of the Fe0.1Sc0.9N film growth, the spotty patterns transform into even spottier, but also ring-like indicating a polycrystalline behavior. Superconducting quantum interference device magnetic measurements show a ferromagnetic to paramagnetic transition of TC ˜ 370 – 380 K. We calculated a magnetic moment per atom of μ(Fe0.1Sc0.9N) = 0.037 Bohr magneton/ Mn-atom. Based on the carrier concentration measurements (nS (Fe0.1Sc0.9N) = 2.086 × 1019 /cm3), we find that iron behaves as an acceptor. Comparisons are made with similar MnScN (001)/ScN(001)/MgO(001) system.

Going from a small scale laboratory invention or discovery to a large scale application is not a trivial task and incorporating them into a product for a viable business is even more difficult. As technologies approach final products and applications, the number of criteria it must meet increases exponentially. Economics of the manufacturing process, environmental issues, intellectual property management, etc. needs to be assessed and monitored carefully. Bridging the gap from research to business not only needs multi-disciplinary understanding of the various aspects of the technology, but also how and what it could potentially enable or replace in current technologies and how to go about it through partnerships with global business entities. Especially with new materials, such as nano-scale materials, technology push needs to be rigorous and often the end results are uncertain. One needs to start from a large number of end user applications and narrow down to 1-2 high value-add or high volume opportunities. This process also requires constant development of the existing products to meet the exact needs for the high opportunity end markets. Timing for such efforts is crucial and the resources needed for such activities are often under-estimated by small start-up firms. Even for materials with well understood end products and established markets, significant market pull requires huge investments in product reliability demonstrations, cost of manufacturing, etc. Innovation, flexibility, change, educated risk, adaptability, focus and excellence are all key drivers and necessary ingredients for a successful and sustainable start-up venture. While scientific and engineering innovations are absolutely necessary, the metric for success for any business is revenue generation. Finding the right mechanisms for closing this gap (so-called the valley of death) is where the innovations of entrepreneurs lies. In this paper, I will share some of my personal learning experiences through the start-up company Applied Nanoworks Inc., (now Auterra Inc.).

Infrared absorbance and visible/near-IR excited plasmon resonances are investigated in gold-black, a porous nano-structured conducting film. Polymer infusion (for hardening) generally reduced absorbance in the long wave IR but has little effect at THz wavelengths. The characteristic length scales of the structured films vary considerably as a function of deposition parameters, but the absorbance is found to be only weakly correlated with these distributions. Initial investigations of gold-black by photoelectron emission microscopy (PEEM) reveal plasmon resonances, which have potential to enhance the efficiency of thin film solar cells. For films with different characteristic length scales, the plasmon resonances appear in structures with similar length scales.

In this study, we have developed ferroelectric data storage test systems based on scanning nonlinear dielectric microscopy (SNDM) to conduct various experiments concerning read/write capability. Nanodomain formation on ferroelectric recording media was studied using the data storage test system. A nanodomain dot array was successfully written on a single-crystal LiTaO3 recording medium. The diameter of the written dot was as small as 7 nm. Epitaxial-thin-film LiTaO3 recording media were also developed. Nanodomain dots with the diameter of 25 nm were written on the thin-film recording medium. In addition, a non-contact probe-height control technique was adopted to solve the problem of tip abrasion using higher-order nonlinear dielectric response detection method. Finally, a hard-disk-drive (HDD)-type ferroelectric data storage test system was developed for conducting read/write tests under conditions close to those of actual operation. Capabilities of reading at the bit rate of 2 Mbps and writing at the bit rate of 20 Mbps were confirmed using the HDD-type data storage test system.

The R & D developments in several aspects of catalysis area require cleaner and clean up technologies. Catalysts are used for energy conversion and to convert environmentally hazardous materials into harmless compounds. This presentation reviews the work currently under exploration at IICT that illustrates the perspective of photocatalyst technologies for solving energy and environmental issues for providing sustainable development. Studies on development of photocatalytic materials for degradation of phenolic wastes, common industrial effluent, H-acid, Calmagite (an azodye), Isopruturon (herbicide) and for E-coli disinfection are highlighted. Materials like Natrotantite, Ce-modified zeolites, Ag2O/TiO2, CuO/TiO2 and C,N-doped TiO2 are designed and evaluated for photocatalytic splitting of water for generation of hydrogen energy. Furthermore, potential applications of photo catalysts in the chemical synthesis of N-containing heterocyclic compounds like pyrazines and piperazines which are useful intermediates in the synthesis of various drugs, perfumes, herbicides and dyes are new interesting aspects in the presentation. Thus the present review describes the emerging trends in using photocatalysts for energy and environmental applications.

Electronic structure properties of a photo-catalyst slab system based on a material YVO4 or InVO4 which is sandwiched by water molecular layers have been investigated by first-principles calculation. As a result, we found the tendency that the band gap of the InVO4 slab system sandwiched by water molecular layers was smaller than that of YVO4 system while the band gap values of the bulk crystals of YVO4 and InVO4 are almost same. This result may provide us a good clue to understand the reason why the InVO4 system can indicate a visible light response in photo-catalysis and the YVO4 system can not.

Using direct photoelectrochemical measurement of the photocurrent obtained from Cu2ZnSnS4 (CZTS) absorber layers made by a two-stage electroplating-sulfurisation process, the influence of processing conditions (temperature, time, and pressure) on material quality was investigated with a view to understanding the long sulfurisation times usually found in the literature. The improvement in photocurrent due to KCN etching was also studied, and seems to be due both to removal of surface phases and also slower etching of the bulk material. The optimum sulfurisation time was found to be around 50 minutes, despite evidence that sulfur incorporation and phase formation are complete within 5 minutes. Slow grain growth was suggested as a rate-limiting factor, and a rate constant was derived based on a simple model.

Zinc oxide layers deposited on quartz substrates by means of RF reactive magnetron sputtering with subsequent RTP annealing in a nitrogen flow at 400°C and in an oxygen flow at 500°C have been investigated in applications to waveguide structures. The ZnO films reveal a highly c-oriented columnar structure with a surface roughness of 4.3 nm. Annealing causes a significant increase of the lattice constant to the value of 5.210±0.001 Å suggesting the relaxation of the stress in the film. The annealing process causes a significant improvement of propagation properties of the fabricated waveguide structures in comparison to structures using as-deposited ZnO films. The minimal attenuation coefficient of the 630 nm thick films was found to be 2.8 and 3.0 dB/cm for TE0 and TM0 modes respectively.

The concept of using nanocomposite thermoelectric materials in bulk form for practical applications is presented. Laboratory studies have shown the possibilities of nanostructures to yield large reductions in the thermal conductivity while at the same time increasing the power factor. Theoretical studies have suggested that structural ordering in nano-systems is not necessary for the enhancement of ZT, leading to the idea of using nanocomposites as a practical scale-up technology for making bulk thermoelectric materials with enhanced ZT values. Specific examples are presented of nanocomposite thermoelectric materials developed by our group based on the familiar silicon germanium system, showing enhanced thermoelectric performance through nano-structuring.

Cadmium telluride (CdTe) is a leading thin film photovoltaic (PV) material due to its near ideal band gap of 1.45 eV and its high optical absorption coefficient. The typical CdTe thin film solar cell is of the superstrate configuration where a window layer (CdS), the absorber (CdTe), and a back contact are deposited onto a glass slide coated with a transparent electrode. Substrate CdTe solar cells where the above listed films are deposited in reverse order are not common. In this study, the growth of CdTe thin films deposited on foil substrates by the close-spaced sublimation (CSS) has been investigated for the purpose of fabricating substrate based CdTe solar cells. The CdTe films were deposited at substrate temperatures (TSUB) in the range of 300 to 600°C, and source temperatures (TSRC) in the 600 to 650°C range. The effect of the substrate-source temperature variations on the growth rate, film structure and morphology were studied using XRD and SEM. It was found that for low substrate temperature and as the growth rate increases, grain size was the same but the films appeared to be more uniform and more densely packed with less or no pinholes. The growth rate increased as the source temperature increased. The substrate temperature clearly influences the grain growth and the preferred orientation. As the substrate temperature increased the growth rate decreased and the grain size varied from 2 to 6 μm. XRD analysis showed that with the increase in substrate temperature film orientation changes from preferential along the (111) direction to a mix of (111) (220) and (311).

We present a detailed study of the angular dependence of the magnetization reversal at room temperature of well characterized epitaxial La0.7Sr0.3MnO3 (001) thin films grown onto SrTiO3 (001) vicinal substrates. The step edges at the substrate surface promote a topological modulation of the films along the step direction, breaking the four-fold magneto crystalline symmetry and favoring a two-fold magnetic anisotropy term. The competition between the biaxial and uniaxial anisotropy is depicted within the framework of the current theory, resulting in a vanishing biaxial contribution. The films hence show the magnetization easy (hard) direction parallel (perpendicular) to the steps direction. The thickness-dependent of both anisotropy and magnetization reversal are discussed in terms of topographic changes.

The metallurgical industry of ferrous and non-ferrous metals produce huge amount of wastes. In Slovakia, the factory for nickel production was closed in 1993, but around 5.5 kt of wastes remain in a dump. This waste was used as a model sorbent of heavy metals (Cu, Cd, Co) from wastewater treatments. The TCLP (Toxicity Characteristic Leaching Procedure) test of precipitated heavy metals on waste materials has confirmed the necessity of waste stabilization. The microwave vitrification was applied because of a high content of iron in waste. After vitrification, the chemical durability and microhardness by indentation have been tested in the glassy and glassceramics obtained.

Within materials science and engineering industries there exists a need for continual professional development and lifelong learning. University materials science and engineering departments and materials related centers have highly qualified instructional faculty, and course management infrastructure that can be utilized to deliver needed continuing education to working professionals via distance learning. This work examines the development and first year delivery results of an online graduate certificate in modern materials characterization techniques for working scientists and engineers.

We characterized the optical nonlinearities of CdSe nanocrystals surrounded by rod-like CdS shells with ultrafast measurements of time-resolved photoluminescence. We measured the exciton-exciton interaction to be, depending on structure details, attractive or repulsive, by as much as 29 meV, due to the unique band alignment in the CdSe/CdS. This feature makes CdSe/CdS dot/rods promising gain media for solution-processable lasers, as it appears combined with 80% photoluminescence quantum yield, narrow size and shape distributions and the antenna effect of the CdS rod shell enhancing optical absorption by more than a factor 50 with respect to bare dots.