Chemical bath-deposited (CBD) thin film CdS has been widely used as a buffer and n-type window layer in CdS/CIGS and CdS/CdTe thin film solar cells. Annealing of CBD CdS assigns to the layers required concentration and mobility of electrons, crystallinity, structural stability and perfect Ohmic front contact in TCO/CdS interface. But always annealing reduces band gap (Eg) of solution-deposited CdS and lowers current density of the CdS/CdTe PV device due to optical absorption within the CdS layer.

We have studied systematically dynamics of changes in CBD CdS/glass thin film structural, optical and electrical properties in annealing process in H2 ambient at normal pressure in pre-heated ceramic tubular furnace. Here we’ll present electrical, characterization results of annealed CBD CdS/glass thin films, 300 nm thick. The films were deposited with thiourea from ammoniacal 1 mM dilute solution of CdSO4 and 0.001 at. % of NH4Cl relative to Cd for Cl doping.

We found high concentration of electrons 1-4 E19 cm-3 in the layers annealed at 200–450 °C, while for 200 °C the long time of annealing over 60 min is needed, but for high temperature region 350–450 °C only for short 10 min annealing this concentration region of electrons was achieved. In the high temperature region rapid decrease of electron concentration and conductivity will go on with increasing annealing temperature and time. Mobility of electrons will decrease from 9 to 5 cm2/V·s in the annealing region 200–350 °C, which is probably connected with disordering of lattice. On the basis of acquired results we propose an hypothesis about substitutional incorporation of OH group on S site in CdS lattice in deposition process and that (OH)s complex defect acts as a donor defect like Cl and we believe that the both defects are responsible for changes of thin film CdS electrical, optical and structural properties in the annealing process. Thermal annealing in hydrogen atmosphere is a convenient and appropriate method for precise control of CdS thin film electrical properties, and also for creation of n/n+ CdS window layers in the substrate configuration of a solar cell.

The effect of pH was investigated on the morphological and spectroscopic properties of PANI thin films on PET. PANI/PET strips were prepared by a pattern-printing technique and coated with a thin film of polyaniline in situ emeraldine oxidation state, doped with HCl (PANI-HCl), obtained by in situ polymerization. AFM, UV-VIS-NIR and FTIR/ATR spectroscopic results showed that pH has a great influence on the polymer layer morphology of the coating layers, while the intensity of vibrational bands decreases with rising pH, increase due to changes in the H-bonded structure in the polymer chain.

The change in phase stability of Group-VB (V, Nb, and Ta) transition metals due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy that correlates well with the position of the Kohn anomaly in the transverse acoustic phonon mode. The predicted position of the Kohn anomaly in V, Nb, and Ta is found to be in a good agreement with data from the inelastic x-ray or neutron scattering measurements. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the body-centered-cubic phase. The opposite effect (destabilization) happens when Nb or Ta is alloyed with neighbors of the 3d-transition series.

A systematic study was carried out to determine the effects of composition and grain size on the structural, optical and magnetic properties of pure ZnO and vanadium-doped ZnO nanocrystalline powders and films in the 0.0 at.% V - 6 at.% V range. The powders and films were synthesized via a sol-gel approach, where ethanolamine was used to increase the viscosity of the precursor solutions and promote the adhesion of the films onto quartz substrates. Powder X-ray diffraction confirmed the formation of ZnO (host oxide) after annealing of the precursors in air. The average grain size in the thin films ranged from 11 nm to 23 nm when the samples were annealed in air for one hour between 450ºC and 550ºC. UV-vis and photoluminescence confirmed the formation of the host oxide. Also, the photoluminescence intensity was found to be strongly dependent on the amount vanadium. Furthermore, it was found that the vanadium concentration and the annealing temperature play an important role in the ferromagnetic behavior of the material.

Thermochromic materials have temperature-dependent optical properties. This paper discusses the limitations of thermochromic VO2 films for energy efficient fenestration and shows from calculations that nanocomposites containing VO2 can have superior properties and display high luminous transmittance and large temperature-dependent solar transmittance modulation. Even better results may be found for nanoparticles of VO2:Mg.

In present work we propose a theoretical model for investigation of the exchange bias effect in Ni50Mn37.5Sb12.5 alloy. In the model, we use a three-dimensional cubic lattice with periodic boundary conditions. Also we take into account the magnetic interactions between atoms in 1st, 2nd and 3rd coordination spheres and the ferromagnetic and antiferromagnetic anisotropy terms. It is shown that the obtained theoretical temperature dependence of the exchange bias field for Ni50Mn37.5Sb12.5 alloy is close to the experimental data.

The formation of metal silicide plays important role in deciding the nature of the contact on silicon.Due to their chemically neautral nature,Au and Ag are used as contact metals in various devices.In particular the role of silicides is known to be crucial in defining the behavior of the electrical contact. The interaction of these metals with silicon at cluster level is still under the study.For naoscale devices, the nature at such interaction carries lot more inportance. Bulk Gold silicide(Cohesive energy ~ 3.81eV/atom) shows higher stability compared to silver silicide(Cohesive enrgy ~ 2.95 eV/atom). In the present work we show computational results based on Density Functional Theory(DFT) of Si cluster adsorption on Ag(111) surface and compare with the results of Si adsorption on Au(111). These results bring out the difference in Si cluster-metal surface interactions at the nanoscale. In particular the Si island-metal surface interaction shows island size dependence. We have presented results for most stable orientations only.

Sillenite Bi25FeO40 crystallites have been fabricated via a sol-gel approach. X-ray diffraction results show that single-phase Bi25FeO40 can be synthesized at the annealing temperature of 600 o C with the help of PEG additive. The amount of additives and the annealing temperature has great effects on the formation of phase pure Bi25FeO40 crystallites. The morphologies of Bi25FeO40 crystallites were observed by SEM techniques. UV-vis diffuse reflectance spectroscopy indicated the good visible light absorption of Bi25FeO40 crystallites. The photo-catalytic activity of Bi25FeO40 powders was evaluated by the degradation of methyl orange solution assisted by H2O2 under UV-Vis light and Vis-only light irradiation, which suggested that Bi25FeO40 crystallites are potential photocatalytic materials.

We show that the average parameters of conductive filaments and the related characteristics of threshold switches can be described thermodynamically based on the system free energy. In particular, we derive analytical expressions for the filament radius as a function of applied bias, and its current-voltage characteristics, the observations of which have remained without mathematical description for about 30 years. Our theory is extendible to filament transients and allows for efficient numerical simulations of arbitrary switching structures. This new understanding may be important in the advancement of novel technologies that combine threshold switches with phase change memory, such as 3D architectures.

The fabrication of nanoporous aluminum oxide (Al2O3) membranes for large scale production of nanowires is performed at room temperature by a two-step anodization of commercially available aluminum foil tapes. During the anodization process, an oxide barrier layer is formed at the interface with aluminum. In the present work, the removal of the barrier is performed by (i) ramping down the voltage with a rate in the range of 0.5 V per 60s to 2 V per 60s and (ii) immersing the substrate in 50% phosphoric acid for up to 5 minutes. Depending on the removal conditions, several morphologies at the oxide-aluminum interface are observed by Scanning Electron Microscopy (SEM). Ramping down the voltage at less than 0.3 V per 15s combined by immersion in 50% phosphoric acid for less than 3 minutes is found to open the barrier layer of the nanopores. The pores have root-like structure with branches as small as few nanometers due to the slow voltage ramping. Several amorphous anodized Al2O3 (AAO) templates with pore diameter ranging from 30 to 40 nm and with length up to 25 μm were prepared by two-step anodization for the cathodic electrodeposition of photoactive nanowire semiconductors such as copper indium diselenide and cadmium sulfide.

Leveraging past research activities in orientation control of lead zirconate titanate (PZT) thin films [1,2], this work attempts to optimize those research results using the fabrication equipment at the U.S. Army Research Laboratory so as to achieve a high degree of {001}- texture and improved piezoelectric properties. Initial experiments examined the influence of Ti/Pt and TiO2/Pt thins films used as the base-electrode for chemical solution deposition PZT thin film growth. In all cases, the starting silicon substrates used a 500 nm thermally grown silicon dioxide. The Pt films were sputter deposited onto highly textured titanium dioxide films grown by a thermal oxidation process of a sputtered Ti film [3]. The second objective targeted was to achieve highly {001}-textured PZT using a seed layer of PbTiO3 (PT). A comparative study was performed between Ti/Pt and TiO2/Pt bottom electrodes. The results indicate that the use of a highly oriented TiO2 led to highly {111}-textured Pt, which in turn improved both the PT and PZT orientations. Both PZT (52/48) and (45/55) thin films with and without PT seed layers were deposited and examined via x-ray diffraction methods (XRD) as a function of annealing temperature. As expected, the PT seed layer provides significant improvement in the PZT {001}-texture while suppressing the {111}-texture of the PZT. Improvements in the Lotgering factor (f) were observed upon comparison of the original Ti/Pt/PZT process (f=0.66) with samples using the PT seed layer as a template, Ti/Pt/PT/PZT (f=0.87), and with films deposited onto the improved Pt electrodes, TiO2/Pt/PT/PZT (f=0.96).

The Cultural Heritage Science (CHS, formerly SCIART) Program seeks to enhance opportunities for chemistry and materials research at the interface between science and art. The objective is to promote collaboration between cultural heritage scientists, mainly located in US museums and chemists and/or materials scientists in US academic institutions to address grand challenges in the science of cultural heritage. Through the first competition, eight projects, two to three years in duration, were funded at $270,000 to 495,000 each. Every successful proposal demonstrated a clear need for collaboration with good synergy between the collaborating groups, and provided plans for meaningful training experiences for students and/or postdoctoral researchers in the field of cultural heritage science. It is anticipated that the CHS Program will continue for two additional years in a similar fashion. During this period, researchers should be able to more easily identify the disciplinary programs in materials research or chemistry relevant to their work, and their proposals will be reviewed together in panels. Proposals falling outside of the CHS specifications may be submitted directly to the relevant program/s of interest at the National Science Foundation (NSF) as unsolicited proposals. After the CHS Program ends, unsolicited proposals will remain the key mechanism for obtaining NSF funding in this research area.

Resistance switching in metal – insulator - metal (MIM) structures with transition metal oxides as the insulator material is a promising concept for upcoming non-volatile memories. The electronic properties of transition metal oxides can be tailored in a wide range by doping and external fields. In this study SrTiO3 single crystals are subjected to high temperature vacuum annealing. The vacuum annealing introduces oxygen vacancies, which act as donor centers. MIM stacks are produced by physical vapor deposition of Au and Ti contacts on the front and rear face of the SrTiO3 crystal. The time dependent forming of the MIM stacks under an external voltage is investigated for crystals with varying bulk conductivities. For continued formation, the resistivity increases up to failure of the system where no current can be measured anymore and switching becomes impossible.

Effect of surfactants present in alkaline solutions on the capacitance of carbon electrodes has been studied. Different types of surfactants have been selected for this target. Concentration of these electrolyte additives was 0.005 mol L-1. Decreasing the surface tension in the electrode/electrolyte interface allows better penetration of electrolyte into the pores. Detailed analysis of capacitance versus current load, frequency dependence as well as self-discharge, cyclability and behaviour in wider voltage window proved a useful effect of Triton X-100 on capacitor operating in alkaline solution. Influence of surfactant concentration has also been investigated.

Concerns about the availability and long-term supply of petroleum-derived fuels have caused the search for alternative sources of energy. Liquid fuels will for some applications be necessary for an indefinite period of time. Therefore, defining relevant feedstocks, producing fuels from these feedstocks and the properties of these fuels are critical issues. Fuels powering compression-ignition (diesel) and turbine (jet) engines are among these liquid energy sources. Biodiesel, defined as the mono-alkyl esters of vegetable oils, animal fats or other triacylglycerol-based feedstocks plays a prominent role in this connection as alternative to petrodiesel fuels. Important issues facing biodiesel are feedstock supply as not enough vegetable oil is available to replace the whole petrodiesel market and the issue of fuel properties, especially cold flow and oxidative stability. The search for additional feedstocks coupled with the food vs fuel issue has increased interest in inedible oils derived from sources such as used cooking oils, jatropha and algae. However, biodiesel from these sources, as biodiesel derived from classical sources such as commodity vegetable oils, must meet performance criteria and this is not necessarily the case. Therefore, modifying the composition of biodiesel, i.e., its fatty ester profile, is a critical issue to enhance its use in the marketplace. Esters of specific fatty acids impart improved properties to biodiesel with esters of decanoic and palmitoleic acid displaying favorable properties for enrichment in biodiesel feedstocks. Renewable diesel is another fuel that can be obtained from triacylglycerol-based feedstocks. In its composition, i.e. alkane-type hydrocarbons, it more closely resembles petrodiesel fuel. While biodiesel is obtained from triacylglycerol-based feedstocks via a transesterification reaction using an alcohol in presence of a catalyst under mild conditions, renewable diesel can be obtained from such feedstocks via a hydrodeoxygenation reaction using hydrogen in presence of a catalyst under more severe conditions. Biodiesel and renewable diesel are compared regarding their production and properties and it is suggested that each fuel has a role to play in an alternative energy mix based on its properties.

This paper reviews our works about the development of thin composite film based on aligned carbon nanotubes (CNT) forest, embedded in epoxy or PMMA polymer matrix, in order to fabricate membranes dedicated to water purification issue. Indeed, the small internal radius of nanotubes, the smoothness of their inner core and the hydrophobic properties of its interna surface induce remarkable flowing properties for water molecules. In this article, thinnin technology process is investigated to obtain composite film with opened CNT. Different etching techniques as grinding, Chemical Mechanical Polishing (CMP) and isotropic plasma O2ar investigated in term of etching rate and membrane roughness, using AFM and SEM characterizations. Results show CMP process in lapping configuration permits to obtain agreement between high etching rate and membrane roughness. Moreover, to improve water flowing through membrane, O2plasma treatment is used to remove polymer residue spread over CNT. Joint use of lapping and plasma treatment permits to obtain 35μm-thick nanoporous membrane with well-opened protruding nanotubes.

Operations on biological living cells and molecular devices have drivenresearch towards implementation of high-aspect-ratio nano-needles. However,current nano-needle fabrication is complicated to control the sizes andangles. In this work, we develop a simple method to fabricate repeatable andintegrated circuit (IC)-compatible sharp silicon nano-needles based on boronetch-stop in tetramethyl ammonium hydroxide (TMAH) solutions, and the needleangles can be accurately controlled. An analytical model is proposed toefficiently predict the needle sizes and explain the etching evolution ofsilicon nano-needles.

Ambipolar organic transistors are technologically interesting because oftheir potential applications in light-emitting field-effect transistors [1]and complementary-metal-oxide-semiconductor (CMOS) devices by providing easeof design, low cost of fabrication, and flexibility [2]. Although commonorganic semiconductors show either n- or p-type charge transportcharacteristic, organic transistors with ambipolar characteristics have beenreported recently. In this work, we show that ambipolar transport can beachieved within a single transistor channel using LiF gate dielectric in thetransistors with pentacene active layer. This ambipolar behavior can becontrolled by the applied source-drain and gate biases. It was found that atlow source-drain biases multistep hopping is the dominant conductionmechanism, while in high voltage regimes I-V data fits in Fowler-Nordheim(F-N) tunneling model. From the slope of the F-N plots, the dependencybetween field enhancement factor and the transition point in conductionmechanism upon gate bias has been extracted. The transition points show moredependency on gate voltage for negative biases compared to the positivebiases. While sweeping negative gate voltages from -5 to -20 V, thesource-drain voltages change from about 27 to 17 V. On the other hand, forpositive gate voltages from 5 to 20 V, the value of the transition pointstays at approximately 36 V. In order to further understand the transportmechanisms, new structures with an interface layer between dielectric andactive layer have been fabricated and characterized. As expected, asignificant decrease in the amount of the source-drain current has beenobserved after introducing the interface layer.

The U. S. Department of Energy’s Ames Laboratory in Ames, Iowa was a coalition partner for outreach activities connected with NOVA’s Making Stuff television series on PBS. Volunteers affiliated with the Ames Laboratory and Iowa State University, with backgrounds in materials science, took part in activities including a science-themed Family Night at a local mall, Science Cafés at the Science Center of Iowa, teacher workshops, demonstrations at science nights in elementary and middle schools, and various other events. We describe a selection of the activities and present a summary of their outcomes and extent of their impact on Ames, Des Moines and the surrounding communities in Iowa.

In Part 2, results of a volunteer attitude survey are presented, which shed some light on the volunteer experience and show how the volunteers’ participation in outreach activities has affected their views of materials education.