The electrochromic switching behavior of amorphous and crystalline WO3 thin films was investigated. The films were deposited on ITO-coated Corning 7059 glass substrates by sputtering. X-ray diffraction showed the crystalline film to have a mixed monoclinic/orthorhombic crystal structure. The coloration mechanisms in the visible and very near infrared were investigated by hydrogen insertion. A numerical fitting scheme allowed the coloration of the films to be expressed by means of the extinction index. As expected, crystalline WO3 exhibited more modulation in the very near infrared. A reversible crystallographic distortion was associated with the coloration of the crystalline WO3 films.

Multilayer structures for electrochromic devices have been produced using vacuum evaporation and electrochemical deposition, and have been optically and electrically characterized by real time measurements. The deposited structures consist of a five layer stack comprising a transparent electrode (indium tin oxide) on glass substrates, an electrochromic active layer (W03), an electrolyte, a complementary electrochromic film (prussian blue) acting as a reservoir for the active layer, and a second transparent or reflecting electrode. In order to determine the process dynamics, real time transmittance and reflectance spectral analysis on the visible range have been performed using a multiple analysis system (OMA), during colorswitching of the device, in coordination with electrical characterizations of the switching process by current and charge transfer measurements. These measurements were performed as a function of time and of the driving voltage, and provide a means of determining the structural parameters of the device through the switching time and the current transient.

Non-stoichiometric perovskites with the general formula SrFeO2.5+x have potential in oxygen sensing applications. Thin films of these compositions have been grown onto various substrates by pulsed laser deposition techniques. At elevated temperatures, (T > 550K), the films react rapidly and reversibly with oxygen and the bulk oxygen content, x, of the films changes. Accompanying the change in oxygen stoichiometry are significant changes in the optical transmittance and reflectance of the films. Transmission spectrophotometry in the uv-vis region has been used to determine the relationship of transmittance with oxygen composition in the gas phase. Spectrophotometric data have been obtained by a batch method and also in-situ in a flow cell at T = 690K. The data show a large variation in transmittance, exceeding 103 for the batch measurements, with SrFeO3 showing the highest opacity. The design of the flow cell is also described.

Polycrystalline aluminum nitride (AIN) thin films have been synthesized by ion-beam assisted deposition method and the effect of ion beam energy on the film structure and optical properties has been studied. The kinetic energy of nitrogen ion beam was varied from 0.05 to 1.5 keV under the constant current density. Microstructure of films was examined by thin film X ray diffraction (TFXRD) and optical transmission spectrum from 220 to 2200 nm was measured by UV-visible spectrometer. The TFXRD studies show that the (00*02) plane of hexagonal AIN grows preferentially with the ion beam energy of 0.05 keV and the intensity of the (10*0) and (10*1) planes becomes strong with increasing the ion beam energy. The optical measurements reveal that the wavy structures due to the interference effect are observed in the transmission spectra and the wavy pattern decreases with increasing the ion beam energy, resulting in the decrease of refractive index.

The size effects were studied by the measurement of optical transmittance, Raman spectra and mechanical dissipation in BaTiO3 films. The variation of energy gap, Raman peaks, Curie temperature with film thickness and grain size was observed and the possible origin was analyzed.

Thin films of tin-doped indium oxide are widely used for transparent conductors. One application of ln203:Sn (ITO) is transparent contacts for electrochromic electrodes. Optical design of electrochromic devices requires knowledge of the optical constants for each layer from the near ultraviolet and visible to the mid infrared. Determination of the optical constants of the electrochromic layer cannot be made in isolation; a complete device or at least a half-cell including a layer of ITO is required to change the optical state of the electrochromic material. Measurements on ITO were made using variable-angle spectral ellipsometry, and spectral transmittance and reflectance. A series of structural models were fit to this data. The problem is complicated because of inhomogeneity in the films, variability in the manufacturing process, and sensitivity to environmental conditions. The spectral dependency was modeled by a single Lorentz oscillator and a Drude free-electron component. This data was then used as the basis for a model to extract the optical constants for a tungsten oxide electrochromic film.

Scanning force microscopy is used to study the structure of various sensing films after chemical and thermal treatments. An example chemical modification of the sensing film can be achieved by heating a Pt/Ti sensing film in an oxygen environment. 1 With Pt acting as a catalyst, the Ti can become partially oxidized, resulting in a Pt/TiOx film which has different electronic properties than a metallic film. By further oxidizing the film, an insulating layer of TiO2 may be achieved. Or as in the case of hydrogen sensing, the Pt/TiOx film may revert to a more metallic state via the reduction of TiOx. The chemical interactions of these sensing films may be associated with large scale microstructural changes. The sensing activity and the structure of Ti, Pt/Ti, and Au/Ti films to gases such as hydrogen, and propylene has been studied. These chemical and morphological changes can be monitored by measuring the resistance of the thin sensing films. Pt/Ti films were found to have the best response to hydrogen (200 ppm) and propylene (150 ppm), while Au/Ti films showed weaker response to propylene (500 ppm) and CO (1000 ppm). The Pt/Ti films also showed shifts in temperature with changing propylene concentration possibly due to catalytic combustion.

We report the fabrication and characterization of a low temperature (200°C-400°C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.

In this paper, we discuss changes in the phase diagram of hydrogen in both bilayer (i.e. 200–2000 Å Nb/ 100 Å Pd on glass) and multilayer configurations. In fact, it is the changes in this phase diagram, in addition to the Pd coating, that makes theses bilayer systems useful for hydrogen gas sensors. Comparison of x-ray diffraction, electrical resistivity and volumetric measurements of the films before and after hydrogen charging indicate that the phase equilibria between a correlated (high concentration) and a dilute phase of hydrogen in Nb is not sensitive to the number of layers in the films. On the other hand, the experimental methods show different behavior for 200 Å thick Nb films and thicker (>400 Å) Nb layers. Diffraction results showing unisotropic lattice expansion will also be discussed..

Structural studies have been carried out on SnO2 multilayer thin film grown by the Rheotaxial Growth and Thermal Oxidation method on A120 3 substrates. A preliminary analysis of the X-ray diffraction patterns shows that, in addition to the Sn0 2 cassiterite phase, a strong contribution from an orthorhombic Sn02 phase is present.

In the case of the 3-layer film, the orthorhombic phase is structurally and microstructurally stable after an annealing up to 32 h at 400 'C. The cation coordination is similar to that found in cassiterite, but the chains of edge-sharing [SnO6]8- octahedra run in a zig-zag fashion along the [100] direction, each straight unit containing four octahedra. The relationship between the two phases is discussed on the basis of structural simulations including twinning planes in the crystal structure.

The morphology and domain structure of unsupported PbTiO3 thin films with fine grains (>200 nm) were investigated by TEM technique. The unsupported PbTiO3 thin films were successfully prepared by sol-gel process onto NaCI substrates and followed by dissolving away the substrates. Electron diffiraction patterns showed that the unsupported PbTiO3 thin films had slight <110> preferred orientation perpendicular to the film surfaces. Grain size and morphology vary significantly with the thickness of the films or the annealing temperatures. Even though the grain size is rather small (40–180 nm), the domains are clearly visible. Most of the grains show single domain, while some irregular and curved domain walls appear only in a small portion of the fine grains. The number of single-domained grains increases with decreasing grain size. Almost all domain walls observed are 90° walls.

Composition control in lead or bismuth based ferroelectric thin films was studied for rf magnetron, dc magnetron and ion beam sputter depositions with metal or oxide targets. For room temperature depositions, (1) control of the target surfaces, (2) suppression of harmful effects from negative ions and (3) control of oxygen content in the films were significant. The surface of the lead target gradually degrades and alters the lead flux extracted from the target. At low pressures resputtering from the film occurs by negative oxygen ions. It is necessary to put more oxygen into the films in the sputter depositions with metal targets and the ion beam sputter depositions. For high temperature depositions, a composition self control was observed for films deposited in excess lead environments.

Strain sensors based on thin films of indium tin oxide (ITO) have been developed for a variety of applications, where the measurement of both static and dynamic strain are required at elevated temperatures. ITO thin films were prepared by rf reactive sputtering in Ar:02 mixtures from high density, electrically conductive targets having a nominal composition of 90% In203 and 10% Sn02. The resulting ITO films exhibited room temperature resistivities between 2x10−2 and 2x102 ω cm, an optical bandgap of 3.5 ev and tested “n” type by hot probe. These same films exhibited large negative gage factors (G=δρ/ ρδε) when tested at room temperature and a relatively low temperature coefficient of resistance when tested at elevated temperature in air. Specifically, gage factors approaching -100 with little hysteresis were observed for strains up to 700 μin/in and TCR's as low as 195 ppm/°C have been measured for the sputtered ITO films. In addition, these films were electrically stable and readily formed ohmic contacts with platinum at temperatures up to 1180°C. In this paper, we report on the electrical properties and piezoresistive properties of ITO based strain gages at temperatures up to 1180°C. Prospects of using ITO thin films as the active strain elements in high temperature strain gages and the characteristics of strain sensors based on ITO are discussed.

Ferroelectric relaxor thin films of lead lanthanide zirconate titanate (PLZT) (9.5/ 65/35) have been deposited by the laser ablation technique onto metallized silicon and lanthanum aluminate substrates. The dielectric and pyroelectric properties of PLZT films and their temperature dependencies have been investigated in some detail in an evaluation of their potential as prospective pyroelectric infrared (IR) detector materials. The temperature at which the dielectric constant of a PLZT film reaches its peak is different from that for the peak pyroelectric coefficient. A lower dielectric constant at which the pyroelectric peak appears contributes to a high figure of merit for PLZT films, so that it is competitive with its ceramic counterpart, as well as with Pb(Mg1/3Nb2/3)O3 (PMN) relaxor ferroelectric ceramic.

Heavily boron-doped (4×1019 < [B] >1021 cm-3) polycrystalline silicon thin films on oxidized silicon cantilevers were studied by FTIR spectroscopy. The experimental reflectance spectra (400–7000 cm-l) were compared to those expected for a poly-Si/SiO2/c-Si/SiO2 multilayer where the doped layer is described by a simple Drude model. The resulting free carrier concentration and conductivity were checked against electrical measurements.

The optical response of the polycrystalline layer in the medium infrared range (400–3000 cmn−1) was shown to be affected by a static uniaxial stress applied along the film plane by a four point bending mechanical device. The resulting microscopic piezoresistivity longitudinal gauge factors in the 15 - 25 range are in close agreement with those deduced from conventional electrical piezoresistivity measurements on sub-millimeter size patterns. The effective range of applicability of this contactless method and the potential application of such layers to temperature-independent miniature pressure sensors are discussed

The effect of microstructure, including average grain size, grain size distribution, precipitate distribution and crystallographic texture, on the reliability of Al and Al-alloys is well documented. In this paper, the various x-ray methods available for measuring preferred orientation in blanket films are compared and contrasted in an effort to find the fastest, most accurate method to acquire crystallographic texture information. I(111)/I(200) ratios from Bragg-Brentano scans (θ/2θ), rocking curves, and complete pole figures (fiber plots) were compared for four Ti/AlCu films having greatly different crystallographic texture components. The results show that it matters how texture is measured in a thin film; only pole figures (fiber plots) are unambiguous. In addition, the local texture in a series of stress-voided 0.48 um wide Ti/AICuSi/TiN lines was measured using Backscattered Kikuchi Diffraction (BKD). Samples were chosen from two sets of identically prepared wafers (processed at different times) showing large differences in stress-voiding driven resistance versus time behavior. The more strongly textured (111 ) films had decreased stress-voiding lifetimes and tended to have smaller average grain sizes with slightly larger grain size distributions. This is in apparent contradiction with previous results in Al films, where improved stress-voiding and electromigration behavior were found in those films with the strongest (111 ) texture.

A simplified microstructural model of an interconnect is considered in order to develop a criterion for failure due to void production induced by electromigration. The kinetics of growth of individual voids at grain triple junctions are calculated and the time dependence of the change in conductance of an interconnect estimated from the time dependence of the total volume of voids produced. It is found that the time to failure increases with increasing grain size, i.e., decreasing density of sites for flux divergence, consistent with observations.

In principle, the resistivity of bulk FCC cubic materials should not depend on the orientation due to the fact that the conductivity tensor is single valued. However, we show that this conclusion is not valid for thin films. Deposition of highly oriented Al, Ag, and Cu films on amorphous substrates using the partially ionized beam (PIB) technique exhibit a resistivity which is strongly correlated with the texture, i.e., the tighter the texture, the lower the film resistivity. We model the film as an array of grains whose grain boundaries can be considered as delta function potentials for electron scattering and the strength of the potentials can be calculated from the measured resistivity of the films. On the other hand, the fiber texture distribution of the the films is obtained from X-ray pole figure measurements, and Monte-Carlo simulations are then performed using this data to determine the average dislocation density at the grain boundaries due to the grain to grain crystallographic mismatch. We show that the transmittance coefficient for electron scattering, and therefore the film resistivity, is a monotonically increasing function of the average dislocation density. We therefore conclude that the structure of grain boundaries in a thin film provides the necessary mechanism by which the resistivity of an FCC cubic metal can depend on the texture.

Passivated Cu lines deposited by CVD, electroplating, and sputter-reflow were investigated using x-ray diffraction. Blanket films of the three types were measured for strain and texture post-deposition and after an anneal step to mimic the passivation temperature step. Texture in the CVD films was random, while the electroplated and sputtered films showed a strong {111} texture. Lines were then measured of each type. The measured strain was modeled using finite element calculations. While the strain in Cu was high compared to Al lines of similar geometry, no stress voiding was observed using high voltage scanning electron microscopy.

The addition of La and Pr to Al thin films markedly decreases the grain size of the Al matrix and largely suppresses growth of thermal defects of hillocks and whiskers at high temperatures (350°C – 450°C). A large number of fine metallic compounds of Al11RE3 and/or Al3RE (RE = La and Pr) were segregated in an Al matrix, mostly at grain boundaries, after annealing at 350°C. The resistivities of the films after annealing at the above temperatures show very low values of less than 6 μωcm, without the salient formation of hillocks or whiskers on the film surfaces.