Over the past three decades, ultrashort laser pulses have been demonstrated to be a very powerful tool to investigate materials properties at the nanoscale. A key driving force is the high-time resolution required to study heat transfer across interfaces and in thin films. The Time-Domain Thermoreflectance (TDTR) is now widely used. This optical technique offers an interesting alternative to electrical approaches such as the 3ω method. We present a complete study of the TDTR signals. We investigate the influence of the modulation frequency on the measured signals and we show how this experimental parameter could be set to enhance or reduce the sensitivity to a specific thermal parameter. The dependence of the measured “apparent” thermal conductivity of the thin film as a function of the modulation frequency is discussed. Results are applied to investigate thermal properties of a series of InGaAs samples with embedded ErAs nanoparticles.

PbZr0.53Ti0.47O3 (PZT) ferroelectric thin films were deposited on LaNiO3 (LNO) buffered stainless steel (SS) substrates by sol-gel method. The effect of LNO buffer layer on the orientation and electric properties of PZT thin films for different thicknesses were studied. X-ray diffraction (XRD) results indicated that PZT thin films on SS substrates exhibit the (100) preferred orientation with the LNO buffer layers. Scanning electron microscope (SEM) images show that PZT thin films were well crystallized with grain size of about 100 nm. PZT thin films deposited on SS maintain the excellent ferroelectric properties with remnant polarization of about 20 μC/cm2.

We made an amorphous-silicon (a-Si) solar cell with a nanowire-array structure on stainless steel(SS) by plasma enhanced chemical vapor (PECVD) deposition. This nanowire structure has an n-type Si nanowire array in which a-Si intrinsic layer and p type layer are sequentially grown on the surface of the nanowire. The highest open-circuit voltage (Voc) and short-circuit current density (Jsc) for AM 1.5 illumination were 620 mV and 13.4 mA/cm2, respectively at a maximum power conversion efficiency of 3.57%.

We investigated the process of the hole inlet closure in surface-diffusion-driven transformation of arrays of high-aspect-ratio holes on Si(001) substrates. The inlet gradually shrinks while keeping the circular shape because of lateral bulging of the inlet surface. We observed complicated top view morphologies reflecting the four-fold symmetry of the Si(001) surface on the inlet surface. Large {111} and {113} facets are formed in the four equivalent azimuths of the [110], while corrugated patterns arise in the four equivalent azimuths of the [100]. Atomic force microscopy observations reveal that the corrugated pattern is composed of three types of small facets, namely, {110} and two {113} in relation of the mirror symmetry. The corrugated pattern formation is due to the geometrical restriction that there is no stable facet between (001) and (010) in the [010] azimuth. The observed morphological evolution is interpreted as surface-diffusion-driven transformation under constraint of the anisotropic surface energy of Si.

A non-equilibrium Cu-Zr-Ag alloy was designed for the development of an alternative electric connector to Cu-Be alloys. This work aims at producing a Cu-Zr-Ag sheet using a hot-powder-rolling (HPR) process. The sheets were produced by a sequential process of HPR, pre-annealing, and cold rolling, using Cu93.5Zr5.5Ag1 (at.%) alloy powder produced by an argon gas atomization method. The Cu93.5Zr5.5Ag1 alloy sheet has a tensile strength of 1188 MPa and a conductivity of 33.2% IACS, which are similar values to those of Cu-Be alloys. In this paper, we optimize the conditions of the HPR process and reveal the correlation between the microstructure and properties of the Cu-Zr-Ag sheet produced by the HPR process. In addition, we discuss the alloy’s applicability for use as a connecter material.

Lithium ion conducting argyrodite-type Li6PS5X (X = Cl, Br, I) compounds were prepared using mechanical milling followed by annealing. XRD characterization reveals the formation and growth of Li6PS5X crystals in samples under varying annealing conditions. Temperature dependent XRD data showed the monotonic increase of lattice constant within the range of study. For Li6PS5Cl and Li6PS5Br an ionic conductivity of the order of 10-3 S/cm is reached at room temperature, which is close to the Li mobility in conventional liquid electrolytes and well suitable for all-solid-state safe electrochemical energy storage devices. Bond valence analysis of Li ion migration paths for the argyrodites showed the formation of low energy pathway cages around halide ion for Li6PS5Cl, around the sulfide ion for Li6PS5I. For higher activation energies these cages are interconnected to form a 3-D pathway network. In the case of Li6PS5Br cages around Cl and Br require about the same activation energy.

A prototype expanded-beam spectroscopic ellipsometer has been developed that uses uncollimated (non-parallel, diffuse) illumination with a detection system consisting of an angle-of-incidence-sensitive pinhole camera for high-speed, large-area imaging/mapping applications. The performance of this novel instrument is being tested for imaging/mapping of mixed-phase hydrogenated silicon films having graded amorphous (a-Si:H) and nanocrystalline (nc-Si:H) components throughout the film depth. The speed of the measurement system makes the instrument suitable for use on production lines. The precision enables detection of subnanometer thicknesses, and refractive index and extinction coefficient changes of 0.01. Angle-of-incidence and mirror calibrations are made via well-known sample structures. Alternative commercial instrumentation for mapping by spectroscopic ellipsometry must translate the sample or ellipsometer in two dimensions. For this instrumentation, even a 15 × 15 cm2 sample with cm2 resolution requires > 200 measurements and at least 15 min. By imaging along one dimension in parallel, the expanded-beam system can measure with similar resolution in < 2 min. The focus of recent instrumentation efforts is on improving the overall system spectral range and its performance.

We present a first principles thermodynamic study of O ad-atom and vacancy formation on the AO- and BO2-terminated (001) surfaces of the PbTiO3 (PTO) and LaMnO3 (LMO) cubic perovskites. Our results show that, owing to the highly energetically unfavorable nature of O vacancy formation on these surfaces, O vacancies appear only at high temperatures and practically irrelevant low pressures on the (T, p) surface phase diagram. In contrast, effortless formation of O ad-atoms on the surfaces is encountered at practically achievable pressures and temperatures. Above room temperature and close to atmospheric pressures, we predict clean PbO and TiO2-terminated (001) PTO surfaces as the stable surface phases while partially or fully O ad-atom covered surfaces are found to be more stable for LMO. These results are consistent with the observation that LMO is far more active towards oxidation catalysis than PTO.

The mechanism of damage production in solids during irradiation is of great practical interest in nuclear technology. The need to increase the life time of current nuclear plants as well as extreme conditions (high temperature and high neutron flux) in new generations of nuclear plants leads to have a deep insight into radiation damage in solids. In fact, the slowing down of particles in solids leads to a non homogeneous distribution of defects in solids, giving rise to complex microstructures with unusual properties. Numerous experiments, Molecular Dynamics (MD) and Monte Carlo (MC) simulations have clearly shown that highly damaged areas called displacement cascades are produced by neutron or impinging ions in solids. It is now clearly established that the number and the distribution of these subcascades dictate the long term evolution of the microstructure under irradiation. In this work, we present a new model to calculate the mean number of displacement cascades produced in a mono-atomic solid by an incident particle within the Binary Collision Approximation framework (BCA) taking into account all information extracted from MD simulations. To reach such a goal, the notion of subcascade threshold energy is introduced and discussed on some examples. Within this formalism, we exhibit a new way to estimate the number of defects created in a displacement cascade integrating results of MD simulations of cascades.

Indium and cerium added cobalt-antimony based skutterudites with different filling fractions were synthesized using different annealing synthesis parameters. Phase homogeneity and microstructure of the resulting as-cast material were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The skutterudite material was further compacted using a current-assisted short-term sintering device. Temperature dependent measurements of the Seebeck coefficient, electrical and thermal conductivity were carried out on the compacted specimens in the temperature range of 350 K-700 K. Results indicate significant differences in the transport properties between the slowly cooled and quenched as‑cast materials and also with different filling fractions. Based on the measured transport properties the dimensionless figure of merit ZT was calculated for different filling fractions of indium and cerium. Among these compositions a ZT max of 1.1 at 700 K was obtained.

The absence of engineering from K-12 curricula and mainstream media often causes students to refer back to historical stereotypes regarding what engineers look like and the type of work they do. Such misconceptions may prevent high school students from pursuing engineering as a field of study and increase the need for engineering educational programs [1]. Nano-Challenge is an outreach program that orients high school students to engineering through a one-year research internship. The program is held at the Center for Nanoscale Chemical, Electrical, Mechanical Manufacturing Systems (Nano-CEMMS) at the University of Illinois at Urbana-Champaign. A major focus of the program is to involve students from groups traditionally underrepresented in STEM fields and inform them about engineering earlier in their careers. An external program evaluation provides anecdotal information about the students’ experiences and gives feedback to inform program improvement.

This work highlights the solder joints reliability issues emerged during the development of a novel compliant contacting technology. The peculiar process in this technology is a mechanical lifting procedure in which a pulling force is exerted onto 63Sn-37Pb (eutectic) solder joints (realized by a flux-less thermo compression process), releasing metal traces from the substrate, to form free standing vertical structures. Since joints mechanical characteristics are critical for the successful fabrication of contacts, different bonding conditions (inert or forming atmosphere, temperature rates) and surface finishing (electroplated gold and preformed solder) have been tested. SEM and EDX analyses have been performed on failing joints to investigate failure causes and classify defect typologies. A constantly higher failure rate (percent number of failing joints) has been observed on gold finished surfaces. Analyses proved that such unusual rate was due to contamination of gold surface left by additives in the plating bath and to the embrittlement caused by gold diffusion into molten solder. Plating additives contamination reduces the wettability of gold surfaces. Concentration values of 3 wt.% for gold, considered safe for surface mount applications, caused embrittlement in solder bumps of 20-40 μm diameters.

We report here molecular dynamics results for boron nitride nanoscroll structures (BNNSs) with relation to their stability and formation mechanisms. We show that, similarly to carbon nanoscrolls, BNNSs are stable due to van der Waals interactions among overlapping layers. The energy balance between losses and gains (due to elastic deformations and van der Waals interactions, respectively) when the structure is rolled up leads to the existence of a critical value of the internal scroll diameter where stable or metastable structures can be formed. The mechanisms of scroll formation and stability as a function of their chirality were also investigated.

The intracellular cargo delivery performed by kinesin motor proteins can be biomimetically employed to engineer tailor-made artificial nanotransport systems. Kinesin (expressed on an Escherichia coli system) and microtubules (obtained from the polymerization of tubulin proteins) were prepared and characterized. We report recent results and explore the aim of the construction of biomotor-based NanoElectroMechanical Systems (NEMS) and their potential applications, e.g. as drug delivery systems.

We report the observation of an ultrafast (~ 430 fs) charge transfer processat the interface between a single-walled carbon nanotube (SWNT) wrapped by asemi-conducting polymer, poly(3-hexylthiophene) (P3HT), creating freepolarons on both materials. The addition of excess P3HT as a surroundingnetwork allows these free polarons to be long-lived at room temperature. Ourresults suggest that SWNT-P3HT blends incorporating only 1% fractions ofSWNTs can achieve a charge separation efficiency comparable to aconventional 60:40 P3HT-fullerene blend, provided small-diameter tubes areembedded in an excess P3HT matrix.

The spreading of a smectic nanodrop (8CB liquid crystal) on a solid surface was investigated by direct and real time imaging using the Surface Enhanced Ellipsometric Contrast (SEEC) microscopy [1-2]. The spreading ends with two molecular terraces (made of one monolayer and a bilayer). Two different behaviors were observed. In the first one the upper layer stays dense while shrinking. At the end of the process, the last molecules to disappear are located at the center of the initial disk. In the second one, nucleation and growth of holes is observed in the upper layer, in addition to shrinking. A model is proposed to describe the time evolution of the late stage structure. This model gives exact solutions of the kinetic equations, it covers strongly layered liquids such as smectic liquid crystals, it introduces the two dimensional Laplace pressure as an essential motor for spreading and it takes into account the liquid/gas transition in the surface layer that was consistently reported in experiments with 8CB. This model is in remarkable agreement with the experimental data and can explain the two observed behaviors [3].

The self-assembled block copolymer films with poly (ethylene oxide) (PEO) and hydrophobic polymetharylate (PMA) with azobenzene mesogen in the side chain, denoted as PEOm-b-PMA(Az)n, were used as the template to prepare hexagonally ordered silica nanorod arrays by immersing the template films in the silicate precursor containing tetraetoxysilane (TEOS). The diameter and the center-to-center distance of the SiO2 nanorod arrays were controlled by selecting the block copolymer with different PEO volume fraction. In addition, the contact angles of different kinds’ solvents for the SiO2 nanorod arrays were characterized. We further found, the diameter and the period distance of silica nanorods are very important factors for controlling the contact angle of different kind’s solvents on the surface of the SiO2 nanorod arrays.

The development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment.