A 2D analytic result is presented for the penetration distance P of grain boundary grooves as a function of time t during heating and straining of polycrystalline multilayer thin films with immiscible phases. These grooves can ultimately pinch off individual layers. The result shows that P ∼ t0.25 initially and P ∼ t at longer time. This new analysis contrasts single- versus multilayer thin film response.

Integration of epitaxical and colloidal semiconductor nanostructures into hybrid structures can potentially open unprecedented functionalities and applications. We present here some results of a study of the structural and optical nature of adsorbed InAs nanocrystal quantum dots (NCQDs) on GaAs(001) substrates containing buried nanostructures, providing the first evidence of excitation transfer from NCQDs to the substrate. Results are also presented for the overgrowth of GaAs on the InAs NCQDs, addressing the all important issue of approach to removal of the chemical contamination left behind by the solvent during adsorption of the NCQDS. It is shown that high structural and optical quality buried integrated structures are feasible, thus opening a new field of investigation.

Uncooled cantilever-based microbolometer arrays received more attention recently due to high sensitivity and low cost. The central idea is built on the deflection of a bilayer SiNx/Al material upon the temperature change. The thermal-mechanical behavior of the bilayer is significant for the performance of the microbolometers. In this paper, we perform thermal cyclings to aluminum and SiNx films. The CTEs and the stress evolutions were measured using a curvature measurement system. The curvature profile of a SiNx/Al/Si component was predicted using an extension of Stoney's formula, well agreeing with the experimental results. This work demonstrates fundamental mechanics issues in bilayer SiNx/Al components, which have a great potential for the use in uncooled microbolometer applications.

This paper reports an experimental work using an electric field to induce morphological patterns in a thin polymer film. The film was spin-coated onto a glass wafer, and subsequently heated to above its glass transition temperature to allow viscous flow. An electric field was applied by two parallel electrodes spacing 10 mm apart. The initially flat polymer/air interface evolves into islands. The self-assembled islands exhibited a narrow size distribution and demonstrated spatial ordering. We attribute the pattern formation to the minimization of combined interface energy and electrostatic energy.

AgxNi1−x (x=0.0–1.0) films were grown on Cu substrates by electrodeposition method. The films were found to be a nanocrystalline mixture of pure silver and nickel. The grain sizes were determined by X-ray diffraction and electron microscopy techniques. The minimal value was 3.3 nm for the alloy with 70 wt% Ni concentration. The stability of the grown films upon heating in air and in vacuum was examined. An increase in the grain size was found to begin at 150 °C.

Au/Cr/Si microcantilevers were studied in their as-deposited condition and annealed state, with emphasis on a thermal treatment of 225 °C for 24 hours. Change in beam curvature was monitored during isothermal hold as a function of time. Secondary grain growth was observed in the gold, which contained non-uniformly distributed twins and dislocation defects. Diffusional transport of the chromium layer was observed during annealing. Nodules arranged in the “rolling hill” topography were observed at the free surface, both before and after annealing. Nanometer thick coatings of alumina grown by atomic layer deposition improved the uniformity of both microstructure evolution and curvature evolution during high-temperature annealing.

Nanocrystalline hard films have attracted increasing interest for wear-resistant applications. Especially, films within the system Ti-B-N with its numerous different phases are ideal candidates for materials science based studies on the nanoscale. In physical vapor deposited Ti-B-N films the nanostructure arises during growth by segregation-driven renucleation resulting in 2–3 nm sized TiN and TiB2 crystals. These films exhibit a hardness of ∼ 42 GPa in the as-deposited state which increases to ∼ 52 GPa during thermal annealing in vacuum. Here we show, that as-deposited films have a remarkable fraction of disordered regions surrounding TiN and TiB2 nanocrystals. During thermal annealing, the structural rearrangement causes the formation of compact boundary areas, leading to a hardness increase. At temperatures higher than 900 °C, the occurring B-loss, grain-growth, and recrystallization cause the hardness to decrease.

Pulsed excimer laser projection irradiation has been successfully applied to completely melt and resolidify encapsulated elemental metal films of Au, Cu, Cr, and Ni directly on amorphous SiO2 substrates. A combination of narrow irradiated lines and appropriate SiO2 capping layers was used to obtain films that do not dewet when fully melted. Detailed processing maps were generated for Au and Ni, while equivalent trends for Cu and Cr were also noted. These systems were analyzed for common behaviors, and from these the principle factors, a basic process map is proposed to describe adequately these four systems. Experimental parameters and sample preparation criteria are presented to realize such resolidification studies in other metal systems.

Direct measurements of Mode-I critical stress intensity factor and crack tip displacements were conducted in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS using our in situ Atomic Force Microscopy (AFM)/Digital Image Correlation (DIC) method. The average Mode-I critical stress intensity factor for various fabrication runs was 1.00 ± 0.1 MPa√m. The experimental crack tip displacement fields were in very good agreement with linear elastic fracture mechanics solutions. By means of an AFM, direct experimental evidence of incremental crack growth in polycrystalline silicon was obtained for the first time via spatially resolved crack growth measurements. The incremental crack growth in brittle polysilicon is attributed to its locally anisotropic polycrystalline structure which also results in different local and macroscopic (apparent) stress intensity factors.

This paper presents the stress stability of thin films for MEMS structural and sacrificial layers. The average residual stresses of the thin films were monitored via wafer curvature measurement over a long period of time. Poly-Si, poly-SiGe, poly-Ge and thermally growth SiO2 films are found to be stable in humid environments. Moisture makes LPCVD and TEOS-based PECVD SiO2 films more compressive over time. Multi-layer thin film stress is modeled with the same methodology used to derive the Stoney Equation [1].

We present quasi-particle (QP) corrections to the electronic energies for small GaP fullerenes, a new class of nanoscaled materials predicted to be stable and to show spontaneous formation. Using Time-Dependent Density Functional Theory we also computed the optical absorption spectra. The comparison between single-particle and optical absorption spectra yields strong excitonic effects with bonding energy up to 3.5 eV. The QP corrected HOMO-LUMO energy gaps confirm the high stability predicted for such molecules using ground-state computational schemes. The present results can be useful to identify the successful synthesis of these systems via optical absorption and QP spectra.

Optical thin films with SiO2-TiO2 stack were prepared by the technology of electron beam (e-beam) evaporation with ion beam assistant deposition (IBAD). The mechanical (stress) and optical properties of as-deposited thin films were studied as a function of exposure time in the atmospheric environment. Exposing to the air at the ambient temperature causes incremental compressive stress and spectrum profile changes, which is related to the absorption of water moisture into the films. Making a dense film is, therefore, a practical approach to improve structural stability of thin films and then the performance of optical devices.

We have previously shown that 25nm thick gold stripes on 1mm thick silicone membrane retain electrical conduction when stretched up to 100% along their long dimension. To function as electrical interconnects in conformable integrated circuits, the metallization must be stretchable in arbitrary directions. Therefore we have made and tested the mechanical and electrical properties of complex conductor patterns including X and Y oriented lines and cross junctions. We find that the metal patterns continue to conduct under uniaxial stretching in the X or Y direction and under radial, biaxial stretching.

WC nanoparticles where synthesized using various Physical Vapor Deposition (PVD) methods such as reactive sputtering and Pulsed Laser Deposition (PLD). In both the methods the metal flux obtained is condensed in the presence of He gas. The structural properties of the samples where investigated using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The feasibility of using nano-WC as an alternative catalyst for Pt is determined. A comparative study on two sample of WC, as-prepared and carburized W, was done. The samples were used to check for the reduction of NOx in a simple reactor. The carburized W shows activity at temperatures around 400°C whereas the as-prepared WC shows activity towards NOx reduction at a slightly higher temperature. The stability of both the sample was studied by performing the same experiment at a fixed temperature for an extended period of time. XPS and XRD confirm the formation of oxide phase after de-NOx experiments.

ZnO films were produced on the Si(100) and sapphire(0001) wafers by RF magnetron sputtering in terms of processing variables such as substrate temperature and RF power. The stress in films was obtained from the Stoney's formula using a laser scanning device. The stress levels in the films showed the range from ∼40MPa to ∼-1100MPa depending on processing variables.

SEM was employed to characterize the microstructure of the films. As the substrate temperature increased, the film surface became rougher and the films showed coarser grains. The optical property of the films was studied by PL measurements. At the highest substrate temperature 800°C the film exhibited sharper UV peaks unlike other conditions.

Large-scale Molecular Dynamics (MD) studies on heterogeneous, model metal systems subjected to intense shock loading by a flyer plate were carried out. Of interest here is the effect of structural defects on interfacial strength under these extreme conditions. The metal target and flyer were essentially single crystals of Cu, but an interface layer was created by varying the mass of the Cu atoms in part of the sample. Interfacial defects in the form of vacancies, and at different concentrations, were introduced into the interfacial region. In addition to microstructural evolution of damage in this system, the shock induced temperature and pressure changes were also analyzed.

First-principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) <100> nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.

Mode-I fracture toughness studies were conducted on hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS specimens of various thicknesses. Mathematically sharp edge pre-cracks were generated through micro indentation on the Silicon dioxide sacrificial layer. An atomic force microscope (AFM) was employed to measure the precise length and orientation of each pre-crack. Upon wet etching and release the freestanding uniform width and varying thickness MEMS-scale specimens were tested in Mode-I using a custom-made micro-tensile tester. Fracture toughness values were computed from the test data using linear elastic fracture mechanics (LEFM) for a finite width specimen with an edge crack in the fixed grip loading configuration. The average Mode-I fracture toughness for 0.5 micron thick specimens was found to be while the average mode-I fracture toughness for 1 micron specimens was .

Freestanding Al thin film microtensile beams 600 μm long, 100 μm wide, and with thicknesses of 0.25 μm, 0.50 μm, 0.75 μm, and 1.00 μm were tested under uniaxial tension with a custom-built microtensile system. Displacement controlled experiments employing five strain rates between 8.3 × 10−4 s−1 and 8.3 × 10−1 s−1 were performed. Three crosshead displacements of 1.00 μm (0.17% strain), 2.60 μm (0.43%), and 3.60 μm (0.60% strain) were exercised in order to investigate behavior in the elastic, anelastic, and the inelastic sections of the stress/strain curve.

At a 0.17% strain amplitude, the 0.50 μm thick microtensile beams exhibit an effective modulus that increases with increasing strain rate. The 1.00 μm, 0.75 μm, and 0.25 μm microtensile beams do not show a similar trend. The 0.25 μm and the 0.75 μm thick microtensile beams have similar grain sizes and similar moduli; the 0.50 μm and the 1.00 μm microtensile beams have similar but smaller grain sizes and higher effective moduli. This suggests that grain size is more significant than film thickness in determining the effective modulus of freestanding Al thin films. Furthermore, no stress relaxation behavior was identified for any of the films during the hold at the 0.17% strain amplitude.

At a strain amplitude of 0.43%, the effective moduli are very similar to the values measured at a 0.17% strain amplitude; however, the 0.50 μm and 1.00 μm thick microtensile beams show measurable stress relaxation while the 0.25 μm and 0.75 μm microtensile beams do not. This result combined with a lower observed modulus suggests that the particular anelastic mechanisms operating in these films at these time scales activate sooner and provide a faster stress relaxation process in the larger grained films.

We investigate the formation of (In, Ga)As self assembled quantum structures grown on different orientations of a GaAs substrate along one side of the stereographic triangle between (100) and (111)A surfaces. The samples were grown by Molecular Beam Epitaxy, monitored by Reflection High-Energy Electron Diffraction during the growth and characterized by in-situ Scanning Tunneling Microscopy and Atomic Force Microscopy. A systematic transition from zero dimensional (In, Ga)As quantum dots to one dimensional quantum wires was observed as the substrate was varied along the side of the triangle within 25° miscut from the (100) toward (111)A, which includes several high index surfaces. We propose an explanation for the role of the substrate in determining the type of the nanostructure that is formed.