Solid phase crystallization has the advantages of low cost and excellent uniformity but the crystallization temperature is too high to use glass as a substrate. Using microwave annealing, we crystallized a-Si films at 550 °C within 3 h, which is much shorter than the annealing time at 600 °C of furnace annealing. We fabricated TFTs with poly-Si films crystallized by microwave annealing at low temperature and obtained the characteristics slightly better than or at least comparable to the TFTs by furnace annealing in spite of smaller grain size. This may be due to the improvement of surface roughness of poly-Si film. The poly-Si TFTs with PECVD a-Si film showed better characteristics than the TFTs with LPCVD a-Si film because of larger grain size and smoother Si/SiO2 interface.

A study of an image detector based on µc-Si:H p-i-n structures is presented. The photodetector has a TCO/µc-p-i-n Si:H configuration with two coplanar metallic contacts and a transverse one.

We used a strong spatially fixed light pattern with different intensities to simulate the images and a weak moving light beam to sweep the device in the lateral direction, for its recognition. The sensor surface was scanned row by row and a signal processing procedure was applied to the data after each sweep. It was found that the induced transverse and lateral photovoltages are sensitive to the position and intensity of the image. Through a readout analysis it was possible to recognise, in a continuous way, the image position and relative intensity. The image resolution as a function of the pattern width and intensity is also analysed

A small signal circuit modelling and a simulation consistent with the experimental data are presented and explained. Preliminary tests show that the detector can be used as a two-dimensional image sensor.

Silicon nitride films prepared by low temperatures are widely applicable as gate insulator films of thin film transistors of liquid crystal displays. In this work, silicon nitride films are formed around 300 °C by deposition and direct nitridation methods in a catalytic chemical vapor deposition system. The properties of the silicon nitride films are investigated. It is found that, 1) the breakdown electric field is over 9MV/cm, 2) the surface state density is about 1011cm−2eV−1 are observed in the deposition films. These result shows the usefulness of the catalytic chemical vapor deposition silicon nitride films as gate insulator material for thin film transistors.

Low temperature oxidation is an essential process for thin-film transistors (TFT) used in active-matrix liquid crystal displays (AMLCD). However, low temperature oxidation gives rise to defects at SiO2/poly-SiGe interfaces. We have recently developed a novel plasma oxidation method for poly-SiGe materials. The poly-SiGe wafers are soaked in 0.1 Torr pure oxygen RF (Radio Frequency) plasma and isolated. That is, the sample voltage is the same as the sheath potential of the floating wall, which is always negative since electrons move faster than ions.The defects caused by ion impact can therefore be reduced. No heating is applied during oxidation, as the sample is heated slightly by the plasma. Under our conditions, the temperature is below 100°C even after oxidation for two hours. Depth profiles are acquired by AES and the oxide/substrate interface is examined by XPS. NMOS devices fabricated using this gate oxide show good characteristics.

There have been many reports on the low temperature crystallization of amorphous silicon films by introducing a trace amount of metal impurity for low temperature poly-Si TFTs applications. MIC (Metal Induced Crystallization) uses various metals, to lower crystallization temperature. In this study, a new crystallization method called FALC (Field Aided Lateral Crystallization) in which an electric field is applied during the crystallization was explored. Among possible alloying elements with Si, Ni and Al were selected to compare the effects of these impurities on the FALC.

A trace of Ni lowered the crystallization temperature of a-Si down to 5001C and induced lateral crystal growth along the electric field into the metal free region. But Al exhibited no such effect. A new crystallization method, FALC, showed considerably enhanced speed of lateral crystallization and a strong preferred orientation in crystallized Si-films.

Lowering process temperatures for polysilicon thin-film-transistors (TFTs) has given rise to new worries about the quality of TFT gate oxides. Specifically, presence of large amounts of SiOH bonds in gate oxides has become a matter of concern. We discuss methods for suppressing the formation of Si-OH bonds during chemical vapor deposition (CVD) of low-temperature processed (LTP) gate oxides. The use of remote-plasma CVD and control of the reaction between the silicon source gas and the oxygen source gas are both shown to be effective. We also show that decreased amounts of Si-OH bonds in LTP-CVD gate oxides result in desirable decreases in fixed oxide charge densities.

Over the past few years, Motorola, as well as several other companies around the world, have been developing a new type of flat panel display, called the field emission display (FED). The FED combines many of the advantages of its cousin, the cathode ray tube (CRT), including high brightness and contrast, wide angle viewability, and speed in a flat package that is only a few millimeters thick. A 14 cm diagonal FED prototype built at Motorola Flat Panel Display Division is shown below, in Figure 1.

A triode structure of chimney-shaped field emitter arrays is proposed in this article. This triode structure includes the chimney-shaped emitter, thermal oxidation dioxide, and the plateau-shaped singlecrystalline silicon gate electrode. For the application of the matrix-addressable and large area flat panel display, the uniform structure of the emitters and the yield become critical manufacturing issues when attempting to control nano-meter size features. The uniformity and yield of the chimney-shaped emitters are very well controlled. The nano-sized gate-to-emitter separations can be created by the changing thickness of the insulator. The uniformity of the insulator and emitter material can be controlled within 3% which can be obtained by most large area thin film deposition tools, not by photolithography.

It is shown that the facile electron field emission from diamond and diamond-like carbon occurs because surface groups such as C-H can produce large changes in electron affinity, so that electric fields from the anode can be focused towards unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downwards band bending creates very large fields which cause Fowler-Nordheim emission, while not exceeding the breakdown field, which is the highest for any solid.

This study explores the field emission properties of nitrogen doped diamond grown by microwave plasma CVD. Several diamond samples were grown on silicon under varying conditions. With certain process parameters, films can be grown which exhibit photoluminescence bands at 1.945eV and 2.154eV that are attributed to single substitutional nitrogen. Field emission characteristics were measured in ultrahigh vacuum with a position variable anode. For samples grown with gas phase [N]/[C] ratios less than 16, damage from micro-arcs occurred during the field emission measurements. Samples grown at higher [N]/[C] content could be measured without damage. These measurements indicate relatively high threshold fields (>100V/µm) for electron emission. From the data, two possible field emission mechanisms are presented. Conducting defect states in the bandgap of diamond may provide a source of electrons to the emitting diamond surface.

We report the results of junction capacitance measurements on thin tetrahedral amorphous carbon (ta-C) films to deduce their defect densities. We find defect densities in the range 3 - 7 × 1017 cm−3 in the undoped ta-C films, and roughly an order of magnitude larger in the nitrogen doped (n-type) films. In some cases fairly uniform defect profiles were obtained covering a thickness of a couple of hundreds angstroems. We also observed a thermal activation process of carriers from defect states at the ta-C/c-Si interface with an activation energy in the range of 0.4eV to 0.5eV.

Electronic properties of polymer-like hydrogenated amorphous carbon films, grown in a RF-assisted microwave plasma reactor, have been studied using optical absorption and photoluminescence spectroscopies. Using a Forouhi-Bloomer parametrization of π-π* transitions, two regimes are evidenced for increasing C atom density : a decrease of the optical gap Eππ* at constant (H/H+C) content attributed to sp2C clustering, followed by some H elimination with minor changes in Eππ* due to cross-linking of polymer chains. The photoluminescence efficiency in the visible range (peak at ≈ 2.3 eV) is found to decrease over four orders of magnitude at the onset of the cross-linking regime. This quenching is attributed to stress-induced non-radiative centers.

We have printed Metal-Insulator-Metal Diodes onto flexible substrates using hybrid polymer and metal-metal oxide inks. Successful device structures were printed by means of several processes including 1] a two step process of Ta in polymer matrix with thermally grown oxide followed by printed Cr in polymer and 2] a one step process of pre-oxidized Ta microparticles in polymer. Back-to-back diode I-V characteristics were demonstrated with tunable turn-on voltages between 5V and 100V. Coupled with a fully printable bistable, electronically addressable electrophoretic ink which we have developed, such systems open the way for all printed, reflective, bistable electronic displays.

The fabrication of bistable membrane structures with potential application to projection displays has been demonstrated. The use of a thin film in heavy compression combined with a central pivot point enables the fabrication of devices with two mechanically stable orientations. The demonstration structure consisted of a silicon dioxide membrane, a thin silicon nitride fillet pivot and thin aluminum electrodes. Polysilicon was used as the sacrificial material.

We have developed new polarizing coating materials and processes which enable the fabrication of polarizers for large-area liquid-crystal displays. The polarizing materials are novel discotic surfactants which self-assemble in aqueous solutions to provide a stable liquid-crystalline phase within a wide range of concentrations and temperatures. These lyotropic liquid crystals in an aqueous medium can be spread on a substrate surface by a variety of techniques including a knife-like doctor blade, a rolling cylinder, or a roll-to-roll method. Under the shearing force applied during deposition, the liquid crystals align on the substrate forming a dichroic polarizer. This alignment process allows continuous production of large-area polarizing films at low cost compared with the current technology that requires stretching of the films. Thin coatings can be applied to flexible plastic films, glass, or rigid plastic substrates. Direct coating of the polarizing material on glass eliminates several process steps in liquid-crystal display production since lamination of the polarizing film is no longer required. These new polarizing films have a high optical performance including a polarizing efficiency of above 98% and a dichroic ratio as high as 7.7.

UV-light effects on the polyimide films have been studied by characterizing the film property changes and by measuring the liquid crystal pretilt angle. Infrared, UV-visible and X-ray photoelectron spectroscopy measurements indicate that bond-breaking and oxidation occur during broadband UV-illumination of the film in the air. Free radicals are formed during UV-illumination as evidenced by the analysis of electron spin resonance spectra. Surface tension and polarity are increased after UV-illumination based on the contact angle measurements. While the pretilt angle on the rubbed polyimide film is decreased after nonpolarized UV-illumination, polarized UV-light generates a relatively small pretilt angle on a nonrubbed surface.

Both steady-state current and dielectric-loss measurements were performed on a liquid-crystalline material, 4-(trans-4-pentylcyclohexyl)benzonitryl, in an isotropic liquid phase, which provide information on generation and behavior of ions, dominating DC and AC conductivity, respectively. The frequency dependence measurements of dielectric-loss can successfully estimate such characteristics of ions as total quantity of electricity, diffusion constant (mobility), and the size. With help of chemical analysis like ion chromatography and semi-empirical quantum chemical computation, the majority of ions, especially dominating AC conductivity, were estimated to be inorganic cations with Stokes' radius of around 2 × 10−8(cm), either naked or hydrated, and solvated ions with Stokes' radius of around 5 × 10−8(cm), most probably with the liquid-crystalline molecules at the solvation number of 1.2 in average. The present microscopic investigation of conduction mechanism is of great help for development of liquid-crystalline materials, especially for use in sophisticated displays with excellent picture quality.

Conjugated polymers and polymer blends were developed for photosensing applications. Large size photosensors fabricated in ITO/polymer/metal configuration show high photosensitivity, 0.1-0.4 A/Watt in visible and near UV, as good as that made with inorganic semiconductors. The processability of the polymeric materials allows these photosensors be made in large size, onto substrates in desire shape, or even in flexible form, hybridized or integrated with optical devices or electronic devices. Large area, full-color, digital image sensing is demonstrated using photodiode arrays made from semiconducting polymers. The photodiode arrays, fabricated by casting the semiconducting polymer from solution at room temperature, have high photosensitivity, low dark current and large dynamic range. Photo-detection with desired spectral response or multi-band selection are also demonstrated.

This paper will review the electrical and optical properties of both monochrome and color electroluminescent (EL) displays. A simple electrical model for thin film electroluminescent (TFEL) device operation will be presented and used to describe the luminance and power consumption of TFEL devices. The basic material characteristics desirable for EL phosphors will be described. Progress in the development of monochrome and color EL displays will be presented including TFEL and Active Matrix EL devices and phosphors.

The change in cathodoluminescence (CL) brightness and changes in surface chemistry of the thin film phosphor, SrS:Ce, have been investigated using a scanning Auger electron spectrometer and an Oriel optical spectrometer. The data for SrS:Ce were compared to ZnS:Cu, Al, Au and Y2O2S:Eu powders all collected in a stainless steel UHV chamber with gas pressures of 10−6 Torr O2. In the presence of a 2kV primary electron beam, the amounts of C and S on the surface decreased while the oxygen concentration increased. As a result, ZnO, Y2O3 and presumably SrOx formed. This change in surface chemistry coincided with a decrease in CL brightness. SrS degraded much faster than ZnS or Y2O2S. The model for this degradation process suggests that the primary electron beam dissociated physisorbed molecules to reactive atomic species. These atomic species reacted with surface S and C, carrying them away and leaving behind an increasingly more impenetrable layer. Threshold voltage experiments were conducted to reveal where it becomes possible to measure the CL. This threshold voltage should be affected by the oxide layer discussed above. The implications for vacuums in an FED FPD will be discussed.