Zinc Oxide (ZnO), II-VI compound semiconductor, is a promising material for ultraviolet (UV) photon sensor applications due to its attractive properties such as good photoconductivity, ease processing at low temperatures and excellent radiation hardness. The rf magnetron sputtering is a suitable deposition technique due to better control over stoichiometry and deposition of uniform film. Studies have shown that the presence of surface defects in ZnO and subsequently their passivation are crucial for enhanced photo-response characteristics, and to obtain the fast response speed. Worldwide efforts are continuing to develop good quality ZnO thin films with novel design structures for realization of an efficient UV photon sensor. In the present work, UV photon sensor is fabricated using a ZnO thin films deposited by rf magnetron sputtering on the corning glass substrate. Photo-response, (Ion/Ioff) of as-grown ZnO film of thickness 100 nm is found to be 3×103 with response time of 90 ms for UV intensity of 140 μW/cm2 (λ = 365 nm). With irradiation on ZnO thin film by pulsed Nd:YAG laser (forth harmonics 266 nm), the sensitivity of the UV sensor is found to enhance. The photo-response increases after laser irradiation to 4x104 with a fast response speed of 35 ms and attributed to the change in surface states and the native defects in the ZnO thin film. Further, enhancement in the ultraviolet (UV) photo-response (8×104) of detector was observed after integrating the nano-scale islands of Sn metal on the surface of laser irradiated ZnO thin film.

In this work, thin films of Bi2Te3 and Sb2Te3 were synthesized by the nanoalloying approach: Nanoscale layers of the elements Element nanoscale layers of Bi, Sb and Te are stoichiometrically deposited on a cold substrate using a MBE setup and subjected to an annealing process in which a solid state reaction yielding Bi2Te3 and Sb2Te3 takes place. Besides the two binary compounds, nanoscale multilayer (ML) stacks of 9 nm Bi2Te3/9 nm Sb2Te3 were created. The electrical transport properties of the binary compounds were determined in dependence of composition. Compound formation was directly observed in temperature-dependent in-situ XRD scans and was found to start at ∼100 °C. The stability of the Bi2Te3/Sb2Te3 ML nanostructure against temperature-driven interdiffusion during annealing was examined by SIMS and TEM for an annealing temperature of 150 and 250 °C, respectively. A comparative TEM study of the as grown and annealed state is presented.

Detecting gamma-ray emission from radionuclides hidden within containers is a significant concern to national security and can be accomplished with scintillating materials such as NaI:Tl, LaBr3:Ce crystals. However, the use of these high quality crystals limits the functionality of the detectors due to their high cost and scalability issues. Therefore the development of more durable, more easily manufactured, and more cost effective scintillating materials is desired. The incorporation of nanophosphors or Quantum Dots (QDs) into a polymer matrix to produce a transparent nanocomposite could potentially provide an alternative method to fabricate scintillating detectors. Embedded in a suitable polymer matrix, nanocomposite detectors may be easily made suitably large for portal monitors. Also, preparation of suitable particle sizes and/or compositions permits selection of a photon wavelength that optimally matches the photodetector response curve to increase the number of photons collected per pulse. In this paper a series of LaF3:Ce nanophosphors with varying doping concentrations (1–30mol%Ce) were synthesized using a chemical precipitation method. Photoluminescence and photoluminescence excitation characterizations indicated that the highest luminescent intensity was obtained from the 20%Ce doped sample with a peak emission at 325 nm. The refractive indices of the nanoparticles were identified by index matching measurements. Then an index matched epoxy was selected for incorporation of these nanoparticles to prepare transparent nanocomposite scintillators. In addition, colloidal solutions of CdTe QDs with various emitting colors were synthesized and incorporated into a Polymethyl-methacrylate (PMMA) matrix to make transparent nanocomposites. An initial evaluation of the scintillation behavior of these nanocomposites was evaluated by exposure to gamma rays.

We describe the fabrication and structure of nanoscale thin films of β phase shape memory alloys with the nominal atomic stoichiometry Au7Cu5Al4 (corresponding to 5.8 wt% Al). These alloys possess properties that suggest they could be used in nanoscale actuators. The films described here are between 20 and 50 nm thick which is below the thickness at which some other shape memory alloys cease to transform. However, microstructural and X-ray studies confirm that the coatings still exhibit the displacive transformations that are a prerequisite for the shape memory effect.

The authors describe an energy harvester circuit fabricated with integrated thin ferroelectric film capacitors on a silicon substrate. The harvesting mechanism is a folded double-beam cantilever with proof masses at both end points. Interdigitated electrode capacitors are located at the three points on the folded cantilever that are expected to experience maximum bending moment and should produce up to 5V as a function of external vibration. The die has the dimensions of 1.6mm on a side and is designed to be mounted in a TO-18 package transistor-style package. Due to its small size, the self-contained piezoelectric MEMs device should produce 50 picowatts in a 1g vibration environment while occupying little space.

We prepared samples by electron beam physical vapor deposition EB-PVD followed by ion bombardment. The samples were than characterized by photoluminescence (PL), x-ray photoelectron spectroscopy (XPS). PL was used to characterize the available energy states. XPS was used to determine the binding energies. The ML’s are comprised of 100 alternating layers of SiO2/SiO2+Cu.

A recurrent problem in the synthesis of hexagonal boron nitride (h-BN) is contamination with oxygen and carbon, leading to possible detrimental effects on optical and electronic properties. Here it is shown that the addition of H2 to the N2/Ar mixture used during the deposition process, clearly suppresses the incorporation of these elements, reducing their combined level below 5 %. The surface morphology, assessed with scanning electron microscopy (SEM), revealed the presence of h-BN nanowalls, i.e. vertically positioned 2D structures consisting out of several h-BN sheets. While Fourier transform infrared (FTIR) spectroscopy revealed the sp2 nature of the bonds, confirming the hexagonal nature of the nanowalls, the quasi-perfect stoichiometry of the material was evidenced by combining energy dispersive X-ray analysis (EDX) and Rutherford backscattering spectroscopy (RBS). The dimensions and density of these walls are clearly film thickness dependent and cross-sectional TEM images confirmed the increasing level of porosity with film thickness. A dense layer of material is present at the substrate-film interface, which gradually evolves into the 2D nanowall structures.

In this study, platinum was electroplated onto bare Ti substrates (Pt black) and through a porous AAO membrane (Pt nanowires). The morphology of the deposits was observed by scanning electron microscopy. Preferential orientation along the (100) direction into the bulk material was evidenced through XRD analysis, as well as at the nanowire surface by using electrochemical characterization. These highly oriented Pt nanowires exhibited an increased activity for the electrocatalytic oxidation of hydrazine oxidation, as compared to Pt black.

Bending tests of Diamond-Like Carbon (DLC) nanopillars fabricated by Focused Ion-Beam assisted Chemical Vapor Deposition (FIB-CVD) were carried out in a scanning electron microscope (SEM) to investigate their mechanical behavior. Special attention was paid on the effect of the specimen size. The nanopillars with nano-sized diameter and micro-sized length were grown using spot irradiation without scanning FIB. The diameter of the nanopillars was changed in the range of 100 ~ 1000 nm by changing the magnitude of defocusing FIB.

In the bending tests, brittle fracture was observed for the nanopillars with diameter of 1000 nm. On the contrary, large deformation without brittle fracture was confirmed in the specimens with diameter of 300 nm. In addition, the pillar recovered its original shape after unloading without any permanent deformation even after the large deformation.

Transmission electron microscope (TEM) analysis revealed that the pillars had uniform amorphous structures regardless of the diameters if the FIB was defocused during processing. In addition, similar gallium (Ga) content and sp2/sp3 fraction were observed in both specimens. These results indicate that difference in microstructures cannot be the reason for that in mechanical behavior. In other words, it must be caused by the intrinsic size effect on the mechanical properties of DLC fabricated by FIB-CVD process.

We examined LEDs as a cheap and test lamp source to simulate monochromatic laser radiation to help us cost out optics while evaluating materials for renewable fuels. The light source spectrum was recorded using a fiber optic spectrophotometer and a calibrated silicon photodiode was used to determine the intensity. Photon flux from the LEDs was recorded using actinometry. We chose CdS and Fe3O4 as photocatalysts. The as-prepared and annealed samples were characterised using X-Ray Diffraction, UV-Visible spectroscopy, UV-Visible Diffuse reflectance spectroscopy, Fourier Transform Infra-red spectroscopy, Attenuated Total Reluctance -FTIR spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). CdS and Fe3O4 were evaluated for hydrogen evolution using DI water, sacrificial agents and an electron donor (methyl viologen) using three light sources (LEDs, sunlight and mercury vapour lamp). Products were collected by an inverted burette (Generation1), balloons with a B-14 adapter (Generation2) and septum cells (Generation3). Developing an analytical technique to quantify products continues to remain a challenge.

Recently, the concept of creating a boron doped nanocrystalline diamond (B-NCD) based temperature regulator for bio-sensing applications was proven. In this work, the next step is taken, i.e. one device working simultaneously as thermistor and heater. In combination with a PID-control., it is possible to create a temperature control, with possible set points going from room temperature till 70°C, with an accuracy exceeding a maximum temperature variation of 0.2 °C. Parallel with steering the temperature by varying the current through the B-NCD film, its resistance is measured with a 4-point measurement from which the temperature can be derived using a calibration curve. This value is the feedback for the PID-control to steer the current used for the regulation.

Well-aligned, 1D CdSe quantum dot (QD) fibers (0.3μm to 2.5μm) containing up to 20wt% fluorescent quantum dots (QDs) were prepared by near-field electrospinning (NFES) process. Electrospun solutions were prepared using PVAc as the matrix polymer, dimethyl formamide (DMF) solvent and colloidal QDs in chloroform (CHCl3). The diameter of the fibers decreased as the ratio of DMF/CHCl3 is varied. QDs showed good dispersion and a linear relationship between QD loading and fiber diameter, as determined by the morphology measurements taken using TEM and SEM, respectively. Fluorescence microscopy shows that there is light attenuation throughout the fibers. Results also show that the NFES process may be used as a method to create aligned, 1D fibers of QDs and potentially other nanofibers.

Boron doped CVD diamond has been extensively studied in bulk form but little has been published regarding the effects that the initial seeding and growth conditions can have on the characteristics of the initial layer of diamond. This can have a dramatic effect on the performance of the film in applications ranging from AFM probe tips to electrodes used for water purification and other applications. This paper will examine how initial growth conditions and seeding methods can affect the film interface characteristics of doped diamond grown in hot filament CVD reactors.

The effects of substitute side chain were investigated using donor-acceptor (D-A) conjugated copolymers consisting of a cyclopentadithiophene (CPDT) derivative and dithienyl-benzothiadiazole (DTBT). The intrinsic properties of the copolymers were significantly altered by perturbations of the intramolecular charge transfer (ICT). The absorption of PCPDT-ttOTBTOT (P2), which assumed a tail-tail configuration, tended to blue-shift relative to the absorption of PCPDT-TBTT (P1). The absorption of PCPDT-hhOTBTOT (P3), which assumed a head-head configuration, was blue-shifted relative to that of P2. The electrical transport properties of field-effect transistors (FETs) were sensitive to the side chain position. The field-effect mobility in P2 (μ2=1.8×10–3 cm2/V·s) was slightly lower that in P1 (μ1=4.9×10–3 cm2/V·s). The mobility of P3, however, was very low (μ3=3.8×10–6 cm2/V·s). Photoexcitation spectroscopy showed that the charge generation efficiency (shown in transient absorption spectra) and polaron pair mobility in P1 and P2 were higher than in P3, yielding P1 and P2 device performances that were better than the performance of devices based on P3.

Small size CdS QDs were synthesized by (i) the single source precursormethodology and by (ii) the microwave synthetic route. The consequences ofCdS QD direct exposure to air for a period of 7 days were investigated byfollowing the evolution of the photoluminescence (PL) and absortion spectra.For QDs obtained by (i), the excitonic emission band (3.0 ‑ 3.1 eV)decreases in intensity, relatively to the low energy one (2.2 ‑ 2.5 eV)tentatively associated to midgap surface states. This suggests arising ofnew recombination path(s) associated to degradations during aging, possiblyan oxidative formation of a CdO surface layer. On the other hand, nosignificant change is observed in the absorption spectra. For QDs obtainedby (ii), no degradation is revealed by the PL spectra which remainunchanged. On the other hand, the absorption spectra are dominated by anunexplained broad band around 3.6 eV which tends to hide the fundamentalexcitonic transition one and increases in intensity with aging.

SiC nanowires were produced from carbon nanotubes and nanosize silicon powder in a tube furnace at temperatures between 1100°C and 1350°C. SiC nanowires had average diameter of 30 nm and very narrow size distribution. The surface of the SiC nanowires is covered by an amorphous layer composed of amorphous SiC and various carbon and silicon compounds. The objective of the research was to modify the surface structure of the SiC nanowires, a step necessary for future surface functionalization. The acid etched nanowires were analyzed using FTIR, TEM, x-ray diffraction, and photoluminescence. The concentration of Si-Ox groups in untreated specimens was estimated to account for 1% of the total mass of a 2 nm thick amorphous layer wrapping around all structures. After treatment in HF this concentration was negligibly small. TEM images show that after treatment the amorphous layer was removed but the diameter of the core remained unchanged. The surface was roughened and multiple pits formed on that surface. X-ray line broadening analysis indicates a significant contribution due to stress caused by dislocations and planar faults. After acid etching line narrowing was observed and attributed to stress reduction and elimination of the smallest wires. The photoluminescence signal from as received samples was very weak but increased greatly after acid treatment, indicating that the signal is related to surface defects. Measurements at low temperatures, 8 K, showed peaks due to point and planar defects.

Monolayers of cobalt phthalocyanine (CoPc) and fluorinated cobalt phthalocyanine (F16CoPc) on silver (111) and on highly (0001) oriented pyrolytic graphite (HOPG) were imaged with a scanning tunneling microscope (STM) at cryogenic temperatures (around 30 K) at Chemnitz University of Technology. Domains of regular arrays with periodicity in two dimensions (2D) and a variety of plane symmetries were observed. Crystallographic image processing (CIP) was used to quantify deviations from the plane symmetry groups and to obtain symmetrized versions of the content of the average unit cells of some of these arrays. Conclusions on the point symmetry of the CoPc and F16CoPc molecules within the arrays were drawn.

Polyaniline nanofibres (PAni) can be surface modified to improve electroactivity over a broader pH range. The technique we describe here can be used to attach carboxylic acid terminated substituents. Modified nanofibres maintain their high surface area, and ability to switch between different redox states. These properties make the material suitable for sensing applications. Unlike unmodified PAni, the functionalised material is self-doping and hence more stable in higher pH solutions. Here we demonstrate how modified PAni fibres can be used for the detection of ascorbic acid.