The nanocrystalline ITO embedded Zr-doped HfO2 high-k dielectric thin film has been made into MOS capacitors for nonvolatile memory studies. The devices showed large charge storage densities, large memory windows, and long charge retention times. In this paper, authors investigated the temperature effect on the charge transport and reliability of this kind of device in the range of 25°C to 125°C. The memory window increased with the increase of the temperature. The temperature influenced the trap and detrap of not only the deeply-trapped but also the loosely-trapped charges. The device lost its charge retention capability with the increase of the temperature. The Schottky emission relationship fitted the device in the positive gate voltage region. However, the Frenkel-Poole mechanism was suitable in the negative gate voltage region.

“Label-free” biomolecule sensors for detection of inflammatory cardiovascular biomarker associated with vulnerable coronary vascular plaque were designed and fabricated using micro and nano-textured polystyrene structures that functioned as sensing elements coupled with electronic measurement equipment. We demonstrated that scaling down the surface texturing from the micro to the nanoscale enhances the amplitude of the measured signal strength. We believe that the nanoscale fiber morphology provides size matched spaces for trapping and immobilizing the protein biomolecules resulting in enhanced detection and signal strength. We selected polystyrene as the model system and demonstrated the detection of human serum C-reactive protein (hs-CRP). We employed these findings in designing a platform “lab-on-a-chip” protein sensor. Comparative studies were performed on two different polystyrene textured surfaces: a polystyrene microsphere mat, and an electrospun polystyrene nanofiber matrix.

Measuring residual-stresses at the micron scale in glassy materials imposes experimental challenges, particularly when using diffraction, or other conventional laboratory methods, e.g., optical non-contact methods, grid methods, etc. In this short paper, a technique for mapping residual-stress profiles in amorphous materials with high spatial definition is used to measure residual-stresses in a laser-peened and fatigued bulk-metallic glass - Vit-105. The method involves local deposition of nano Pt dots patterns on the mapped region of the specimen and milling of a series of micro-slots of size 15 × 2 × 0.4 μm3 using the focused ion beam of a dual beam Field Emission Gun Scanning Electron Microscope / Focused Ion Gun (FEGSEM/FIB) instrument. The deformation fields in the vicinity of slots are reconstructed by the digital image correlation analyses (DICA) of FEGSEM images recorded during milling. The residual-stresses are inferred by fitting a reference displacement field obtained from finite-element analyses (FEA) with the recorded displacement field. In this way, residual-stress distributions have been characterized as a function of the distance from the laser-peened surface to a depth of 1,200 microns with a spatial resolution of 30 μm. The influence of fatigue loading on the compressive residual-stresses spatial distribution is studied and discussed. It was found that the fatigue loading significantly changes the compressive residual-stress spatial distribution in the laser-peened layer.

Discrete nanoscale tubular architectures have received significant attention during the past decade because of their potential role in electronic and photonic devices, sensors, liquid crystals, artificial channel systems and biomedical engineering [1-2]. Our research group has reported the synthesis and characterization of the bicyclic G∧C motif, a self complementary DNA base analogue, which undergoes hierarchical self-assembly to form Rosette Nanotubes (RNTs) [3]. The stability of this system depends however, on functional group density (sterics) and net charge (electrostatics) on the RNT surface [5c]. To this end, we have synthesized several G∧C modules bearing oligopeptides with different lengths and net charge and investigated their self-assembling properties.

One of the primary objectives of the global photovoltaic research community is to effect significant manufacturing cost reductions, either by reducing material and processing costs or by increasing solar cell efficiency. One very promising technology for achieving both of these goals is Sliver technology, which offers potential for a 10- to 20-fold reduction in the consumption of purified silicon, while at the same time achieving very high cell efficiencies by fully exploiting the advantages of mono-crystalline silicon.

Sliver solar cells are thin, mono-crystalline silicon solar cells fabricated using a combination of micro-machining techniques and standard silicon device fabrication technologies. Rather than fabricating a single solar cell on the surface of a wafer, many hundreds to several thousand individual Sliver solar cells are fabricated within a single wafer. The dimensions of a Sliver cell depend upon wafer size, wafer thickness, and the micro-machining method employed.Cells typically have a length of 5 – 12cm, a width of 0.5 – 2mm, and a thickness of 20 – 60 micron. 20% efficient Sliver solar cells using standard cell processing methods and a robust processing sequence, have been fabricated at ANU. Current research efforts are directed towards developing and establishing new fabrication techniques to further simplify the fabrication sequence and to improve cell efficiency.

This paper presents an overview of Sliver technology. The fabrication method and some key challenges in producing Sliver cells is presented along with the measured performance of cells fabricated in the ANU solar research laboratory.

When comparing large numbers of TEM micrographs of insoluble additives in polymer-based nanocomposite systems, the ability to determine or estimate the dispersion quality (i.e. uniformity of size and/or spatial distribution) is often difficult. The objective of this study was to develop a method to quantify dispersions observed in TEM micrographs that enables both a numerical “ranking” to be assigned to individual dispersions as well as tabulation a multitude of images acquired over time. Several methods were reviewed and applied to a set of TEM dispersion images of an insoluble additive in polystyrene. Projected area diameter, particle area, and Euclidean distance between particle centroids were chosen from all the particle size distribution and spatial distribution parameters present in the literature, but none successfully yielded a quantitative indicator of dispersion quality for the micrographs. In contrast, generating cumulative volume percent curves for each sample appeared to be a preferred method of quantifying and comparing dispersions in TEM micrographs. The volume diameter values obtained by this method can be used for “ranking” and tabulation of dispersion quality and account for both “good” additive dispersions (i.e. those with small domains of a narrow size range around 1 μm or less) and “bad” additive dispersions (i.e. those with non-uniform domains ranging in size by several microns or more). As a result, the numerical values generated by this method can be used to quantitatively determine correlations between the dispersion quality of nanoparticles in polymer-based nanocomposite materials and various macroscale physical and/or performance properties of such materials. This method’s precision was statistically determined to decrease with increasing particle size and be heavily dependent on representative sampling.

Optimum quality polycrystalline AgGaSe2 thin films were deposited on H-terminated n-Si substrates by controlled thermal evaporation method. The film deposition conditions were varied to optimize the structure and optoelectronic properties of AgGaSe2 thin films. X-ray diffraction (XRD) studies showed that all AgGaSe2 films were of chalcopyrite structure and while the films deposited at room temperature (300 K) had random grain orientation, the films deposited at higher substrate temperature (≥ 450K) showed preferred (112) orientation. The composition of the films were analyzed by electron probe microanalysis (EPMA) deposited at different substrate temperatures. The ultraviolet-visible (UV-Vis) spectra showed the optical bandgap of 1.80 eV, with sharper band edge for the films deposited at higher temperature. The films were p-type and the resistivities of the as deposited films at 300 and 650K were ~5×103 and ~200 Ω.cm respectively. p-AgGaSe2/n-Si heterojunction solar cells, having an active area of 0.18 cm2 without any antireflection coating were designed and fabricated. It was observed that the films deposited at 650K produced heterojunctions with significantly improved photovoltaic properties. The evidence of the barrier height modifications have been provided by C-V measurements. Under solar simulator AM1 illumination, the improved junction exhibited an efficiency of 5.2%, whereas the AgGaSe2 films deposited at 300K showed a lower efficiency of 2.1%.

DNA Computing is a rapidly-developing interdisciplinary area which could benefit from more experimental results to solve problems with the current biological tools. In this study, we have integrated microelectronics and molecular biology techniques for showing the feasibility of Hopfield Neural Network using DNA molecules. Adleman’s seminal paper in 1994 showed that DNA strands using specific molecular reactions can be used to solve the Hamiltonian Path Problem. This accomplishment opened the way for possibilities of massively parallel processing power, remarkable energy efficiency and compact data storage ability with DNA. However, in various studies, small departures from the ideal selectivity of DNA hybridization lead to significant undesired pairings of strands and that leads to difficulties in schemes for implementing large Boolean functions using DNA. Therefore, these error prone reactions in the Boolean architecture of the first DNA computers will benefit from fault tolerance or error correction methods and these methods would be essential for large scale applications. In this study, we demonstrate the operation of six dimensional Hopfield associative memory storing various memories as an archetype fault tolerant neural network implemented using DNA molecular reactions. The response of the network suggests that the protocols could be scaled to a network of significantly larger dimensions. In addition the results are read on a Silicon CMOS platform exploiting the semiconductor processing knowledge for fast and accurate hybridization rates.

The true nature of scientific research, often neglected in science education and pre-service teacher training, is critical to student conceptual understanding of how science works. Many education students leave school with the naive view that science is a collection of facts rather than a dynamic process of inquiring into nature. The ASU Math and Science Teaching Fellows (MSTF) program gives in-service math and science teachers an opportunity to experience scientific research by immersion in active research groups in state-of-the-art laboratories. With a better understanding of what science looks like in actual research laboratories, these teachers implement direct instruction in the Nature of Science in their classrooms. Research that was conducted by teachers in a nanoscience laboratory and how they plan to implement their experiences into their high school classes will be presented.

We report the study of a process which enhances the power conversion efficiency (PCE) of solar cells employing poly(3-hexythiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). In this process, the spin-coated solution of the active material was maintained in the liquid state for a prolonged duration. It was observed that through this process, the PCE of the device was enhanced by 31% for the case of a fast-grown film. It also provided a further 19% enhancement on top of the enhancement obtained by the familiar solvent annealing process. We found that this process depends critically on the presence of a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) buffer layer. It is hypothesized that the action of this enhancement process involves the interfacial interactions between P3HT and PEDOT polymers.

Fabrication of TiO2 nanofibers and their applications as the electron transporting layer for hybrid photovoltaic cells were studied. TiO2 nanofibers were electrospun onto an indium tin oxide (ITO) on glass substrate with a thin TiO2 blocking layer from a precursor solution [polyvinylpyrrolidone (PVP), titanium(IV) butoxide (TiBu), and acetylacetone (ACA)] in methanol. Many sources of precursor for fabrication of the thin TiO2 blocking layer, i.e. sintered TiO2 nanoparticle paste, sintered TiO2 nanoparticle-dispersed solution, TiBu solution with ACS in methanol, and titanium isopropoxide solution in ethanol were studied. The thin TiO2 blocking layer/nanofiber electrode was subjected to calcination at 450 °C for 3 h. The nanofiber electron transporting matrix was penetrated by blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Thermal annealing and deposition of Au electrode were then carried out. After photovoltaic characterizations, it was found that hybrid organic-inorganic photovoltaic cells made of TiO2 nanofibers exhibited remarkable improvement of the cell efficiencies as compared with that of TiO2 flat film. Maximum power conversion efficiency (PCE) of hybrid organic-inorganic photovoltaic cells made of TiO2 nanofibers of 1.11% could be obtained (efficiency of flat TiO2 device = 0.28%).

Several viologen electrochromic devices with different thicknesses on glass substrates were constructed, using a mixture of 4,4’-bipyridine and 1-bromoethane. The thickness of each device was fixed using a thermoplastic spacer. The devices were electrochemically tested with optical and impedance analysis. The range of the transmittance change is highly dependent on thickness. The electrical behavior of the material and the physical and chemical characteristics are derived from the proposed electrical equivalent circuit model. A simple Randles circuit including a Warburg diffusion impedance element, a charge transfer resistance and a double layer capacitive element is proposed for the fittings process. Variations on thickness of internal layer of devices lead to use a short or an open circuit Warburg element. A threshold potential, from which the device is colored, indicates the charge diffusion effects.

We have investigated the stability of nano-amorphous region of Ge2Sb2Te5 (GST), fabricated by Electron Beam Lithography (EBL), dry etching, and ion implantation. Nano-structures, less than 100 nm in diameter and 20 nm thick, were either embedded in a crystalline environment or just isolated. We have observed nano-structure crystallization by in situ Transmission Electron Microscopy (TEM) in the 75°C-150°C temperature range. Re-crystallization of amorphous dots embedded in a crystalline region (either in the cubic or hexagonal phase) occurs by the movement of the interface at relatively low temperature (about 90°C). Instead, in the isolated structures the transition occurs at about 145°C by nucleation and growth. These results might be of relevance for the data retention of sub-50nm devices. Indeed, the more stable amorphous phase in self-standing regions indicates the better retention properties of isolated cells with respect to the traditional mushroom cell configuration.

A process optimization has been developed for obtaining nanocrystalline cellulose (NCC) by acid hydrolysis of commercially available microcrystalline cellulose (MCC) in high yield (~ 40-50%). This method was based on control of key parameters such as the rate of addition of sulfuric acid solution to the MCC/water suspension, the mixing speed, the volume of collected NCC suspensions and the volume ratio of NCC suspension to water during dialysis. The resulting NCC products were characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental analysis (EA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electron microscopy results showed that the rod-shaped NCC had lengths and widths of about 40-400 nm and 5-40 nm, respectively.

Reorganization energy is one of the important factors to decide the rate ofelectron transfer according to the Marcus theory. Small reorganizationenergy is highly desirable in design of optoelectronic and electronicdevices like as organic light emitting diode. For this reason,reorganization energy of aromatic diamine derivatives, N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) and 4,4′-diphenyl-N,N,N′,N′-tetraphenylbenzidine (DTPB) havebeen studied theoretically by self-exchange electron transfer theory. Byexecuting the Gaussian 03 calculation we can easily figure out theoptimization point which needed for calculation of the inner reorganizationenergy (λ) of self-exchange electron transfer reaction. Also ionizationpotential and electron affinities of these molecules can be calculated atthe density functional theory level with basis set 6-31G** and 6-31G* using Gaussian 03 software on the basis of ab initio method. It gives possibility to develop asemi-empirical model for the observed absorption and photoluminescencespectrum.

Different nanoclay mixing strategies using a three-roll mill and ultrasonication is proposed to obtain the desired polyester/nanoclay dispersion, intercalation, and exfoliation. The dispersion states of the modified nanoclay in polymer with 2, 4 and 6 wt% loading were characterized with X-ray diffraction, scanning electron microscopy (SEM), and low and high magnification transmission electron microscopy (TEM). The mechanical properties of the clay-reinforced polyester nanocomposites were a function of the nature and the content of the clay in the matrix. The nanocomposite containing 4 wt% modified Cloisite® 15A exhibits excellent improvement in modulus (by ~51%) and tensile strength (by ~12%) with a decrease in fracture strain (by ~26%) and fracture energy (by ~17%). These mechanical characteristic changes can be attributed to the dispersion, intercalation, and exfoliation of the nanoclays inside the polyester matrix.

We have investigated the current-voltage characteristics of themulti-layered photovoltaic devices consisting of ITO/oxide /p-type(donor)/fullerene/ bathocuproine (BCP)/ Al structures. We chose variousp-type (donors) small molecules and polymers in order to tune the values ofionization potential (IP) of donor molecules. The open-circuit voltage (Voc)increases with the increment of IP of donor materials. However, VOC was limited at ~0.6-0.7V for the devices without oxidelayer. On the other hand, the VOC increases up to 0.9V for thedevices with NiO and to ~ 1.1V for the devices with MoOX as ahole extraction buffer layer, respectively. We also estimated thework-function differences between Al and the oxide as 0.7, 0.9-1.0, and1.2-1.3 eV for the device without oxide, with NiO, and with MoOX,respectively. We therefore concluded the value of VOC is limitedby the lower part of VOC and energy difference between the LUMOof fullerene and the HOMO of donor ΔE.

Mechanical behavior of ultra-fine grained (UFG) steel fabricated by high pressure torsion (HPT) was investigated by micro-sized compression test of a micro-sized pillar with uniform dimensions (non-tapered, non-filleted) carefully fabricated by FIB milling. After HPT process, grains were elongated to shear direction and its grain size was decreased down to 300 nm in diameter with increasing strain amount. Compression test confirmed that the uniform elongations of ultra-fine grained materials were lower than 3% and do not depend on the grain size.