Ferroelectric thin films of the lead zirconate titanate family have been integrated with silicon-based micromachined structures in the fabrication of microelectromechanical devices. Sol-gel deposition techniques have been applied in the formation of ferroelectric thin films with high piezoelectric and pyroelectric coefficients for physical forces sensors and infrared detectors, respectively. Knowledge of both electrical and mechanical properties is important in realizing microelectromechanical devices with predictable performance. This pape reports piezoelectric coefficient, pyroelectric coefficient, dielectric constant, and Young's modulus for lead zirconate titanate and lead titanate thin films.

Smart electroceramics, in the form of ferroelectric thin films show great potential for applications in the field of microelectromechanical systems. Ferroelectric thin films will become a key player due to their optical, mechanical, electrical and thermal sensing with actuating capabilities. Recent results on electromechanical transduction in piezoelectric (e.g. PZT), electrostrictive (e.g. PLZT), and antiferroelectricferroelectric phase switching (e.g. PLZSnT) thin films and their potential applications in smart micromechanical systems are discussed. The possibility of three dimensional structures exists in the emerging technology of ferroelectric fibers. Some exciting applications for these films and fibers include microvalves, ultrasonic micromotors, microrobotic actuators and micropumps.

Ferroelectric ceramics such as PZT, while exhibiting strong piezoelectric effect, have the disadvantages of a high acoustic impedance, difficulty to miniaturize and not being suitable to broad band ultrasonic applications. Polar ferroelectric polymer such as PVDF and its copolymers which can be obtained in thin film form, have low mechanical Q and low acoustical impedance although their piezoelectric coefficients are significantly lower than those of the piezoelectric ceramics. Composites of piezoelectric ceramic powders, such as PZT and Calcium modified Lead Titanate (PT) in a matrix of P(VDF/TrFE) have been fabricated in our laboratory, in order to Investigate whether these materials could have the low acoustic, broad band properties of the polymers whilst retaining the high piezoelectric coefficients of the ceramics. In the present paper the results of a study of the electromechanical coupling factor (kt), the quality factor (Qm) as well as the gh and dh piezoelectric coefficients of these 0-3 composites poled both by corona and by the conventional method are given.

Active and adaptive thin film materials for “smart” materials will likely be a heterostructure of several types of thin films. In this investigation, deposition and processing of thin film Shape Memory Effect TiNi and thin film ferroelectric BaTiO3 and SrTiO3 are discussed. Growth conditions as well as the thermodynamic conditions for thin films are described. It was found that amorphous thin films of TiNi and BaTiO3 can be crystallized simultaneously by air annealing at 600°C.

Experiments have been conducted to study the nonlinear constitutive properties of ferroelectric ceramics for large strain operation applications, where the mechanical behavior of the material dictates the overall electromechanical response of the devices. For this purpose, polarization and strain are measured continuously on a compression cuboid. Severe non-linear and hysteretic behavior is observed in these materials. An empirical formulation has been proposed to model the constitutive laws applicable to this non-linear deformation. Physical mechanism is provided, that is attributed to this constitutive law.

Solid solution compositions of Sr2(NbxTa1−x)2O7 ceramics with Tr ranging from 450°C to 1342°C were fabricated utilizing a hot-forging technique to achieve preffered grain orientation and thus enhance poling. Translucent samples with greater than 99% theoretical density were obtained using this process. Depending on composition, the degree of orientation as determined by x-ray diffraction was found to be 75% to 95%. The thermal expansion, resistivity, and dielectric constant were shown to be very anisotropic. The direction perpendicular to the forging axis proved to be the ferroelectric “easy” direction, exhibiting hysteresis behavior. Piezoactivity in PLS polycrystals was measured for the first time. Hot-forged samples were electrically poled and the electromechanical properties determined using the five different modes of vibration. For Sr2(Nb0.5Ta0.5)2O7: N24=1504 Hz-m, s44=18.2×10-12m2/N, k24=3.0%, d24=2.6 pC/N, g24=6.3×10-3 Vm/N, and Qm=1100. This material was also shown to resist depoling when exposed to temperatures as high as 650°C.

The pulsed laser deposition of zinc oxide films (ZnO) has been studied as a function of laser wavelength, and substrate temperature. The deposited films were characterized by x-ray diffractometry, Auger electron spectroscopy, and scanning electron microscopy. Highly textured (002) ZnO films have been deposited at substrate temperatures of 300 C with laser wavelengths of 532 nm and 248 nm. However, the energy fluence of 248 nm radiation controls the degree of texturing, allowing highly textured films to be deposited at room temperature.

Smart structures based on embedded, textured ZnO coated fibers, and wires exhibit excellent piezoelectric response to external stress.

This paper gives an overview of the recent developments in impact, friction, and wear testing of polycrystalline silicon (polysilicon) based micro electromechanical structures. Impact-friction actuated micromechanisms form a new type of actuators. In this type of actuators, lateral resonant structures are retracted by electrostatic comb drives and are propelled forward toward the actuated micromechanism by elastic forces generated by folded beam flexures at frequencies ranging from 10 kHz to 20 kHz. This sequence generates normal impact and tangential friction contact between the two microstructures, raising wear concerns. Two sorts of impact test structures are introduced in this paper, One with a resonant micro impact bumper (MIB) striking a stationary impact wall anchored ofn the substrate. Another is a testing of two MIBs driven to impact each other. Two types of impact actuators are also described, an impact actuated micro angular oscillator (MAO) and a polysilicon micro vibromotor. The vibromotor is a rotor driven by oblique impact on the rim by a converter pointer tip attached to a lateral resonator. Some initial results of impact wear testing as well as static and dynamic friction done by researchers in the field are also described in the paper. Finally, many areas where material scientists can contribute to this field are suggested.

The research presented here is an investigation of the effects of phosphorus doping on residual stresses and microstructure in polycrystalline silicon. Undoped polycrystalline silicon films were deposited on phosphosilicate glass layers and annealed at 1050 °C for 5 to 60 minutes. The stress gradient through the film thickness was measured from wafer curvature, and microstructure was examined with cross-sectional TEM. A 20 minute anneal is sufficient for stress relief in initially tensile films and produces a uniform microstructure consisting of 0.1-0.2 µm equi-axed grains.

Measurements of the residual stress in polysilicon films made by Low Pressure Chemical Vapor Deposition (LPCVD) at different deposition pressures and temperatures are reported. The stress behavior of phosphorus (P)-ion implanted/annealed polysilicon films is also reported. Within the temperature range of deposition, 580 °C to 650 °C, the stress vs deposition temperature plot exhibits a transition region in which the stress of the film changes from highly compressive to highly tensile and back to highly compressive as the deposition temperature increases. This behavior was observed in films that were made by the LPCVD process at reduced pressures of 210 and 320 mTORR. At deposition temperatures below 590 °C the deposit is predominantly amorphous, and the film is highly compressive; at temperatures above 610 °C (110) oriented polycrystalline silicon is formed exhibiting high compressive residual stress.

This paper discusses a deterministic approach to the stress and deformation analysis of miniaturized structures. Analytical Voigt-Reuss-Hill averages for the elements of the fourth-ranked elasticity tensor representing a polycrystal are evaluated for a planar problem and the variations of elastic moduli with respect to the degree of anisotropy and the mean and coefficient of variation of the preferred orientation direction are studied. The applicability of the averaging methods to the characterization of materials used in micro-electro-mechanical systems are then assessed.

This paper reports on detailed approaches to the probabilistic modelling and analysis of multicrystalline microfabricated beams in the context of micro-electromechanical systems (mems) using simulation techniques. Random, textured multicrystalline beam structures are simulated and analyzed using the finite element method, employing randomly oriented orthotropic material properties to model each individual crystal grain.

The simulation studies are used to assess the influence of size effects and texture on overall beam characteristics, such as stiffness. Results of these studies are then compared with the current approaches based on deterministic analysis and employing simplifying assumptions such as homogeneous, isotropic material properties, and with results obtained from the homogenization approach of Part I.

Organically doped sol-gel glasses are investigated by optical absorption and time-resolved fluorescence depolarization measurements. Silicate and aluminosilicate glasses have been doped with quinizarin (Q) and aluminum phthalocyanine chloride (CAP). The structure and bonding in these inorganic sol-gel solids is different from that in frozen liquids and organic polymers, and the unique dynamics of these systems are a motivation for this study. Both rotational dynamics and optical energy transfer of doped chromophores in sol-gel glasses are investigated by time-resolved fluorescence depolarization measurements. Since the dipole-dipole energy transfer rate is very sensitive to transfer distance, these measurements are used to probe the spatial distribution of dopant molecules within these solids. We also present photochromic results on aluminum phthalocyanine chloride doped silicate sol-gel glasses and discuss possible uses as an optical power limiting material.

Plasma impulse CVD deposited titania thin films, deposited at low substrate temperatures, exhibit low volume losses of < 0.2 dB/cm and high environmental stability. Their use in novel concepts for integrated optical immunosensors is discussed.

All solid state electrochromic smart windows with the configuration glass/ITO/WO3/electrolyte/TiO2-CeO2/ITO/glass have been realized. These devices have potential applications in architectural and automotive fields to regulate the transmission and reflection of the radiant energy. The ion storage electrode TiO2–CeO2 have been realized by sol-gel process and its electrochemical properties are studied as a function of various parameters (thickness, heat treatment, etc.). The electrochemical and optical performances of two cells are reported.

The selective and alienable deposition of patterned thin film epitaxial GaAs/GaAlAs and InP/InGaAsP devices onto host substrates such as silicon for low cost hybrid integrated micro-opto-electronic systems is reported. Using a combination of semiconductor etch layers and selective etches, the epilayers can be separated from the growth substrate. We use a thin polyimide diaphragm as the transparent transfer medium for these epitaxial materials and devices. Each of these thin film devices or a group of these devices on the polyimide is optically aligned and selectively deposited onto the host substrate. Using this technique, GaAs and InP-based light emitting diodes and optical detectors which are microns thick were grown on lattice matched GaAs and InP substrates, lifted off, aligned and selectively deposited onto a silicon host substrate. The devices were then electrically contacted and tested using standard microelectronic fabrication and testing techniques. This method also enables the manufacturable, sparse distribution of costly photonic devices or the deposition of aligned arrays of devices to fabricate larger arrays. The integration of these light weight devices with microsensors and microactuators will foster micro-opto-electro-mechanical integration.

The microstructure found at the surfaces and interfaces of active sensing materials can strongly affect the performance of solid state chemical sensors. This paper desribes research efforts aimed at improving oxide semiconductor-based gas sensors which utilize changes in conductance and diode current-voltage measurements as detection schemes. Studies of oxide surface modification and the formation of Pd/SnO2(110) and Pd/TiO2(110) interfaces are discussed as are the electrical changes for these systems induced by H2 or O2 adsorption. The fabrication of heteroepitaxial SnO2 films for use in planar sensing arrays is also reported and the expected advantages of these highly-ordered, uniform films for simplifying the transducing process are described.

Thin film shape memory alloy has been integrated with silicon in a new actuation mechanism for micro-electro-mechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy micro-actuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.

A new actuator for silicon micro-valves has been developed and tested. A thin film shape memory alloy provides for large deflections with high speed, low power, and small size. The actuator is batch fabricated with planar processes.

Reversible TiNi (= RTiNi) alloy thin film actuator has many advantages for micro sized robot. That is. a micro arm could be fabricated easily on silicon wafer because RTiNi alloy thin film has 3 functions. 1) a frame of the arm, 2) a joint of the arm and 3) an actuator of the arm. and moreover, this film could actuates the arm without friction. A micron sized flexible arm using RTiNi alloy thin film was designed on silicon wafer. IC process for fabricating this arm on silicon wafer was designed. The fabricating process for this arm and its heat treatment process for the RTiNi are presented.