We have developed a photolithographic technique of patterning a pentacene layer with low damage using a SiNx/poly(vinyl alcohol) (PVA) photoresist multi-layer mask. We used a hexavalent chromium-free PVAphotoresist. By inserting a SiNx buffer layer between the pentacene layer and the PVAphotoresist layer, we could suppress an increase in off current caused by interaction between pentacene and the photosensitive functional group in the PVA photoresist. In the patterning process, we found that carriers generated by O2-plasma doped into the pentacene layer and the off current of the pentacene thin-film transistor (TFT) increased.We also found that successive annealing caused de-doping of the pentacene layer and reduced off current of the pentacene TFT.We investigated the density of doped carriers using a simplemodel of a planer pentacene diode aswell as a pentaceneTFT.

A method for depositing large grained polycrystalline GaAs on lattice mismatched substrates through controlled nucleation and selective growth is presented. The process was developed on Si wafers. Nucleation site formation began with nanolithography to create submicron holes in photoresist on Si. Ga metal was electrochemically deposited into the holes. Subsequent arsine anneals converted the gallium deposits into GaAs. Photoluminescence and electron diffraction verified conversion to GaAs. Metal-Organic Chemical Vapor Deposition (MOCVD) enlarged the seed crystals to coalescence without creating additional nucleation sites within the patterned field. Having successfully demonstrated the approach, subsequent work has been directed at lower cost, alternative ways to define initial nucleation sites, such as, microcontact lithography and direct decomposition of triethyl gallium to Ga metal in the MOCVD chamber.

In this work, we report on high-performance low voltage pentacene Organic Thin-Film Transistors (OTFT's) and circuits. Inverters and ring oscillators have been designed and fabricated. At 15 V supply voltage, we have observed invertors showing a voltage gain of 9 and an output swing of more than 13 V. As for the ring oscillators, oscillations started at supply voltages as low as 8.5 V. At a supply voltage of only 15 V, a stage delay time of 3.3 νs is calculated from experimental results.

We believe that these results show for the first time a high speed ring oscillator at relatively low supply voltages. The required supply voltages can be obtained by rectification using an organic (pentacene) diode. These results may have an important impact on the realization of RF-ID tags: by integrating our circuits with an organic diode, the fabrication of organic RF-ID tags comes closer.

Optical fiber sensors have many attractive attributes including high sensitivity, environmental robustness, immunity to electromagnetic interference, and the ability to be remotely interrogated. Furthermore, by incorporating optical fibers into woven and nonwoven fabrics these sensors can be distributed across large areas. In woven optical fibers, microscopic bending is an issue due to the fibers going over and under the yarns. Microscopic and macroscopic bending losses are quantified by placing optical fibers on frames of different radii of curvature and measuring the loss of transmitted light. As an example of the non-woven process, electrospinning was used to overlay a net of sub-micron diameter fibers over the optical fibers. This protects the optical fiber, holds it in place, while still permitting flexibility. To form chemical sensors, standard telecommunications grade optical fibers were tapered such that the evanescent wave extended into the environment. Coating the fibers with a thin layer of gold then permits surface plasmon sensors to be formed. However, the resulting sensors were very fragile and hard to place into fabrics. As a result alternative processes were developed that form fiber structures that are robust enough to withstand textile manufacturing processes yet still allow interaction with the environment.

This paper reports the electrical properties of thin-film transistors with pentacene active layers used in a bottom contact transistor geometry utilizing solution processed poly-4-vinylphenol (PVP) as the gate dielectric processed on a polyethylene napthalate (PEN) substrate. The transistors sometimes exhibit mobilities in excess of 1cm2/Vs. The effect of various surface treatments of the gate insulator, on the electrical properties of these transistors discussed. The development of photolithographically defined 2νm channel length bottom contact transistors is emphasized as the speed of circuit elements such as the rectifier scale inversely as the square of the channel length of the transistors. Surface cleaning and semiconductor deposition techniques that improve transistor characteristics and reduce hysteresis are evaluated and the variation of the ION/IOFF ratios with the different surface treatments is noted.

We have fabricated TFTs of nanocrystalline silicon (nc-Si) at 150°C on clear polymer substrates (coefficients of thermal expansion, α∼45 to 55ppm/K), on Kapton® 200E (α=17ppm/K), and on Corning 1737 glass (α=3ppm//K) for comparison. Because thermally stable polymers, such as Kapton® 200E polyimide, have glass transition temperatures as high as 325°C, they are candidates for direct substitution of display glass. The stresses developed in the substrate and device layers, due to à, are reduced by decreasing the thickness of the active layers, by cutting the layers into islands separated by exposed substrate, and by designing stresses, via plasma conditions, into the SiNx passivating layers. By using these three techniques we have made nc-Si TFTs on high Tg, and high α, clear polymer foils with electron mobilities of up to 18cm2/Vs. When integrated with bottom-emitting organic light emitting diodes, such devices will allow for a 10x reduction in pixel TFT areas, compared to TFTs of amorphous silicon.

Large-area deposition of thin-film amorphous silicon alloy triple-junction solar cells on lightweight and flexible stainless steel substrate is described. The proprietary roll-to-roll operation enables continuous depositions of sophisticated multi-layer structures. The deposition methods include sputtering and plasma-enhanced chemical vapor depositions. Spectrumsplitting triple-junction solar cell design, manufacturing processes, and product applications are presented.

Polymerized dichlorotetramethyldisiloxane (DCTMDS) films deposited by radio frequency pulsed plasma polymerization (PPP) demonstrated very high dielectric constants for an organic-based system, in the range of 7 to 10. The high dielectric constants of PPP DCTMDS films are due to the high polarizability of the DCTMDS monomer. The pulsed plasma duty cycle (ON/OFF) resulted in higher dielectric constant DCTMDS films for higher duty cycles. The variation of dielectric constants does not show any trend with varying film thicknesses, indicating that the thickness of the deposited films is not significant for controlling permittivity. Post-deposition annealing in a certain temperature range improves the electrical integrity of PPP DCTMDS films, but temperatures that are too high induce even higher leakage than the samples with no heat treatment. An optimal annealing temperature was identified to be in the range of 150 °C to 200 °C. Samples annealed within this temperature window have low leakage current densities below 0.1 pA/νm2 at 10 V for film thicknesses about 100 nm. The PPP DCTMDS films are resistant to typical chemical solvents, and have withstood conventional photolithographic processing with no observable film shrinkage, warping or peeling. Film adhesion was excellent and withstood the scotch tape test.

In this work, a PVDF thick film paste was deposited onto interdigitated electrodes to form a capacitor. Two different substrates, alumina and Melinex® were used. Capacitors, fabricated on alumina substrates were tested as strain gauges, and showed a high sensitivity with low hysteresis. Capacitors on Melinex® substrates were tested as pressure sensors by adhering them to planar and cylindrical surfaces and subjecting them to pressures up to 300 kPa. Their sensitivity and hysteresis during cycling were examined and compared. It was found that sensors on cylindrical surfaces showed a higher sensitivity, however the hysteresis was also increased. It is thought that this is due to instabilities in the polymer film, accentuated by stretching of the substrate.

The recently developed physics of thin-film photovoltaics is suggested to be representative of other giant area electronics. We show that (i) giant-area devices are intrinsically nonuniform in the lateral directions, (ii) the nonuniformity spans length scales from millimeters to meters depending on external drivers such as light intensity and bias, and (iii) it significantly impacts the device performance. We derive a fundamental length scale that discriminates between the cases of small and large-area devices, and beyond which a new physics emerges. In addition, we present a practical method of mitigating the nonuniformity effects.

OLEDs are an ideal technology for electronic display applications. They are fabricated by depositing very thin films of organic materials at low temperatures (<100°C) to form bright, vivid power efficient self-emissive light producing elements with fast response times that can be grown on a variety of large area substrates such as glass, plastic or metal foil. These properties make OLEDs ideally suited to enable high information content flexible displays. In particular, the application of phosphorescent OLEDs leads to very low power consumption displays – a key requirement for mobile applications. In this paper we outline our progress towards developing low power consumption, active-matrix flexible OLED (FOLED™) displays. Our work is focused on integrating three critical enabling technologies: high efficiency long-lived top emission phosphorescent OLED (PHOLED™) device technology, flexible active-matrix backplanes, and thin film encapsulation.

Micron-scale lateral patterning of molecular organic thin films is still one of the most challenging issues in the practical fabrication of pixelated organic light emitting device (OLED) displays. In this work we demonstrate organic and metal thin film patterning using a micromachined printhead that modulates the vapor flux of evaporated materials incident on a substrate. The printhead is integrated with an x-y-z manipulator that facilitates patterning within a vacuum environment at pressure of less than 5×10-6 Torr. This printing scheme enables direct, solvent-free and mask-free patterning of organic optoelectronic devices on diverse substrates. As an example we fabricated an OLED array of 30×30 νm Alq3 (tris(8-hydroxyqunolinato) aluminum) pixels. 30 νm wide silver patterns were also directly written using the same technique. The results show that this printing method is capable of patterning molecular organic materials and metals at high resolution (800 dpi).

The focus of this paper is the electrical characterization of coplanar waveguide (CPW) transmission lines that are printed onto nonwoven textile substrates using conductive inks, to determine their suitability for wide-band applications, e.g. digital signaling. The conductive ink line characterization tests included the defining of DC and Time-Domain Reflectometry metrics. The transmission line test samples were screen printed onto two different types of nonwoven textile substrates using two different conductive inks, i.e. inks with different viscosities. Tests showed that the variations in the continuity of the transmission lines varied, giving rise to geometrical variations in the CPW structure; and in the characterization of the same.

Ink jet printheads are now widely used in manufacturing processes that require precise dispensing of materials. In response to requirements for dispensing novel electronic fluids, we are developing next generation jetting technology based on our silicon MEMS technology with a three-dimensional silicon technology and a piezo-based pumping chamber integrated into the chip structure. Examples of opportunities and applications in electronics packaging for MEMSbased ink jet technology will be presented.

A novel patterning technique for high-resolution full-color OLED-displays will be discussed. Currently applied production systems for OLED-displays incorporate a shadow masking system for patterning of single red, green and blue pixels. Due to its limited scalability, alternative techniques, which can be applied to larger substrate sizes, have to be developed. One approach can be the laser induced local transfer of organic materials.

An infrared absorbing substrate (target) is coated with either a red, green or blue light-emitting organic material and placed in a short distance (below 50 νm) of the OLED-substrate onto which the organic material is to be patterned. The laser beam is deflected by a scanner onto the target in single lines. If the scanning speed and the laser power are adjusted properly, the target locally heats up to a temperature at which the organic material sublimes and condenses on the opposing OLED-substrate. By repeating this process for each colour red, green and blue stripes can be deposited. Line widths below 70 νm have been achieved.