Aluminium doped zinc oxide thin films (ZnO:Al) have been deposited on polyester (Mylar type D, 100 μm thickness) substrates at room temperature by r.f. magnetron sputtering. The structural, morphological, optical and electrical properties of the deposited films have been studied. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface. The ZnO:Al thin films with 85% transmittance in the visible and infra-red region and a resistivity as low as 3.6×10−2 ωcm have been obtained, as deposited. The obtained results are comparable to those ones obtained on glass substrates, opening a new field of low cost, light weight, small volume, flexible and unbreakable large area optoelectronic devices.

We suggest to enhance the performance of image acquisition systems based on large area amorphous silicon based sensors by optimizing the readout parameters such as the intensity and cross-section of scanner beam, acquisition time and bias conditions. The main output device characteristics as image responsivity, signal to noise ratio and spatial resolution were analyzed in open circuit, short circuit and photodiode modes. The result show that the highest signal to noise ratio and best dark to bright ratio can be achieved in short circuit mode.

It was shown that the sensor resolution is related to the basic device parameters and, in practice, limited by the acquisition time and scanning beam properties. The scanning beam spot size limits the resolution due to the overlapping of dark and illuminated zones leading to a blurring effect on the final image and a consequent degradation in the resolution.

We investigate the microstructure of polycrystalline silicon films (grain size, texture and grain boundary population) on glass substrates. These films are produced from amorphous silicon precursor layers by scanning the raw beam of a continuous wave Ar+- ion laser operated at a wavelength of 514 nm over the amorphous silicon thereby crystallizing it. The materials applicability for devices in large area electronics strongly depends on the orientation of the surface normal, the average grain size and the defect density and population. Transmission electron microscopy together with electron back-scattering diffraction analysis of the crystallized layers reveal grain widths of about 10μm and grain lengths of several 10 μm. Under certain procesing conditions a preferred (001)-surface normal orientation (texture) forms. The grain boundary population is dominated in the textured films by coincidence boundaries, essentially twin boundaries of first and second order as well as Σ=5 boundaries.

Poly-Si TFT-LCD has begun its way to an advanced display by integrating the driver circuits onto the glass substrate. Improvement of poly-Si TFT is essential in order to achieve value-added display where circuits for various functions are integrated on one substrate. This report the concept of poly-Si TFT display from present state to future scope, and required technologies for each generation. It will also focus on technologies such as crystallization and gate insulator formation at low temperature process.

In order to understand the occurrence and development of inhomogeneous poly-Si texture in the polycrystallization process of poly-SiTFT fabrication, we have simulated 1) the influence of pulse energy (PE) and optical axis (OA) fluctuations on the texture of poly-Si films and 2) the interference between both fluctuations, under the single-pulsed XeCl laser irradiation at the overlapping ratio 98%. The frequency of fatal irregular pulses in the PE fluctuation is much more than that in the OA fluctuation (pointing stability). Once the poly-Si texture suffers a fatal irregular pulse over the complete melting (CM) point, the inhomogeneous texture caused is never recovered by the following overlapping irradiation and no columnar structure is formed. However, when no irregular pulses exceed the CM point, the partial inhomogeneous texture caused in the poly-Si films is recovered by the thinning out of small Si grains in the texture and a columnar structure is formed. The key to the issue of fatal irregular pulses should be not only the reduction of PE and OA fluctuations but also the optimum selection of pulse energy not over the CM point.

Field emission displays can be seriously limited by the rapid current degradation of Mo field emitter arrays primarily due to poor vacuum conditions inside their thin vacuum packages. There have been a number of studies to understand the interaction mechanisms. However, we find that models that have been proposed so far are not consistent with observed device behavior in a variety of gas ambients including inert gases and hydrogen. In this paper, we present a summary of our results on residual gases inside a large number of field emission displays, and the effects of these gases on emission behavior. We describe how these issues and the inter-electrode spacing leading to local pressure buildup impact device life. We present an alternate model based on shallow ion implant to explain the observed device behavior.

MgO and Mg1-xTixO thin films were deposited by the electrostatic spray deposition method using Mg(tmhd)2 and Ti(OiPr)2(tmhd)2 as source materials and tetrahydrofuran and 1-octyl alcohol as solvents. The refractive index of the films shows a strong change from 1.73 for MgO to 2.39 for TiO2. The optical band gap energy values are 3.83 eV for TiO2 film and higher than 5.1 eV for films of Mg/(Mg+Ti) > 0.67. The discharge voltage and current increased with a content of Ti in Mg1-xTixO films. All these changes are closely associated with different Mg/(Mg+Ti) ratios of the films.

Pulsed Excimer-Laser Annealing (ELA) has become an important technology to produce high performance, poly-Si Thin Film Transistors (TFTs) for large area electronics. The much-improved performance of these poly-Si TFTs over the conventional hydrogenated amorphous Si TFTs enables the possibility of building next generation flat panel imagers with higher-level integration and better noise performance. Both the on-glass integration of peripheral driver electronics to reduce the cost of interconnection and the integration of a pixel level amplifier to improve the noise performance of large area imagers have been demonstrated and are discussed in this paper.

Silicide formation may occur at the interface of metal and a-Si films upon annealing with a pulsed excimer laser (XeCl 308 nm; 30 ns). During laser-induced melting, the melt front reaches the Si/metal interface, where liquid phase kinetics allow reaction to occur to form a silicide, despite the <100 ns time-scale. It is thought that silicide reaction would occur if TM, metal ≍ TM, a-Si (1480 ± 50K). The a-Si/metal film stacks that have been investigated include a-Si/Al/Cr, a-Si/Ti, and a-Si/W on thermally oxidized Si. Samples were laser-annealed at varying energy densities in order to determine the onset of melt, and the fluence at which Si/metal interface reaction and film ablation occurs. Rutherford backscattering (RBS), optical inspection, cross-sectional scanning transmission electron microscopy (STEM), as well as parallel and serial electron energy loss spectroscopy (EELS) were used to analyze the films. For the a-Si/Al/Cr and a-Si/W films, no reaction is observed at the Si/metal interface. With a-Si/Ti, intermixing of Si and Ti at the interface is observed, as indicated by RBS and parallel EELS analysis. Laser annealing at higher fluences and further characterization is needed to determine if this mechanism does allow for silicide reaction to take place.

The nature of the formation of sub-grain boundaries within sequential lateral solidification (SLS) processed thin silicon films has been examined using single crystal Si films as a pre- cursor material. Experimental details include the use of an excimer laser projection system and straight-slit beamlets to produce directionally solidified microstructures. Within the SLS processed silicon-on-insulator (SOI) films, three microstructurally distinct regions are identi-fied: (1) an initial planar defect-free area (the extent of which can depend on laser fluence and orientation); (2) a transitional area within which the sub-grain boundaries appear and propagate in a well-defined direction relative to the crystallographic orientation; and (3) a final area characterized by sub-grain boundaries aligning approximately to the scan direction, and the in-plane texture becoming more random. We discuss the results within the context of a plastic deformation model of sub-grain boundary formation.

This contribution investigates the crystallization behavior of amorphous silicon films on glass by using pulsed lasers with very high repetition rates up to 100 kHz. We determine the influence of the laser repetition rate f and of the film thickness d on the grain width g of the resulting polycrystalline silicon films. Our experimental results indicate a strong dependence of the grain width g on film thickness d as well as on the repetition rate f of the laser. The grain width rises from g = 0.27 µm to g = 3.59 µm if the film thickness increases from d = 50 nm to d= 300 nm and the repetition rate f from f = 20 kHz to 100 kHz. We use a purpose developed two- dimensional finite difference numerical model to calculate the evolution of the temperature in the silicon film and in the glass substrate. An increase of both, the film thickness d, and the repetition rate f decrease the solidification velocity v of the film. A comparison of the solidification velocity vs and the measured grain width g shows a linear correlation.

A high-quality silicon dioxide (SiO2) suitable for a gate oxide on plastic substrates is successfully deposited by e-gun evaporation at room temperature. The e-gun evaporated oxide film is free from troublesome hydrogen atoms and high-energy ion damage, which ensures good electrical characteristics. N2O/N2 plasma post-treatment was effective to reduce the flat band voltage and leakage current of the evaporated oxides due to the passivation of high-energy nitrogen and oxygen radicals. In the SiO2 film treated by N2O/N2 plasma for 1 minute, the flat band voltage has been reduced from −2.5V to about −0.5V and the leakage current has been decreased by more than one order. Our experimental results show that very low temperature SiO2 film suitable for a gate insulator of TFTs on the plastic substrates has been successfully obtained by the e-gun evaporation and N2O/N2 plasma post-treatment.

A simple process sequence for fabrication of low temperature polysilicon (LTPS) TFTs with self-aligned graded LDD structure was demonstrated. The graded LDD structure was self-aligned by side-etch of Al under the photo-resist followed by excimer laser irradiation for dopant activation and laterally diffusion. The graded LDD polysilicon TFTs were suitable for high-speed operation and active matrix switches applications because they possessed low-leakage-current characteristic without sacrificing driving capability significantly and increasing overlap capacitance. The leakage current of graded LDD polysilicon TFTs at Vd = 5V and Vg = −10V could attain to below 1pA/μm without any hygrogenation process, when proper LDD length and laser activation process were applied. The on/off current ratios of these devices were also above 108. Furthermore, due to graded dopant distribution in LDD regions, the drain electric field could be reduced further, and as a result, graded LDD polysilicon TFTs provided high reliability for high voltage operation.

Polycrystalline silicon thin films have been deposited by an inductively coupled plasma chemical vapor deposition using SiH4/H2 mixtures. The quality of poly-Si can be improved by increasing RF power and hydrogen dilution ratio. The poly-Si deposited at a RF power of 1000 W with an addition of H2, showed a Raman polycrystalline volume fraction of 85.7 %, FWHM of 6.4 cm−1, deposition rate of 9.64 Å/s and SEM grain size of ∼3000 Å.

Arrays of p-type silicon micro-emitters have been formed using a subtractive tip fabrication technique. Following fabrication, the emitter surface was coated with GaN nanoparticles and nanocrystalline diamond by a dielectrophoresis deposition technique. The emitters were evaluated and compared before and after the surface treatment using I-V measurements in the diode configuration. The phosphor screen, used as the anode, was spaced nominally about 70 µm from the cathode. The field emission characteristics were measured in a high vacuum chamber at a pressure range between 10−5and 10−8Torr. The results suggest that the emitters benefit from coating the surface with nanocrystalline diamond in terms of reduction in the turn on voltage, GaN coating increase the turn on voltage. Both diamond and GaN improved the emission uniformity in the region of the low voltage operation.

Planar field-emission cathode structures consisting of nanostructured carbon flakes have been investigated as an electron source for flat panel display application.

Layers of nanoflakes were grown on silicon and molybdenum substrates using a high- temperature pyrolitic plasma-assisted CVD method. The result is a vertically oriented nanocluster layer of 1-2 micrometer height chemically bonded with the substrates. Additional orientation of the flakes, occurring during the first activation of the cathodes, was observed.

Field emission properties of the emitters were studied in a vacuum chamber and in sealed flat-panel prototype devices with non-patterned low-voltage phosphor screens. Emitters with an area up to 1 square inch were tested under DC currents up to 100 microamps in diode mode. Anode bias up to 1.5 kV was applied. Current fluctuations of 1-2% were achieved using loading resistor.

The SrTa2O6 (STO) thin films were prepared by plasma enhanced atomic layer deposition (PEALD) with alternating supply of reactant sources, Sr[Ta(C2H5O)5(C4H10NO)]2 {Strontium bis-[tantalum penta-ethoxide dimethyllaminoethoxide]; Sr(Ta(OEt)5▪dmae)2} and O2plasma. It was observed that the uniform and conformal STO thin films were successfully deposited using PEALD and the film thickness per cycle was saturated at about 0.8 nm at 300°C. Electrical properties of SrTa2O6 (STO) thin films prepared on Pt/SiO2/Si substrates with annealing temperatures have been investigated. While the grain size and dielectric constant of STO films increased with increasing annealing temperature, the leakage current characteristics of STO films slightly deteriorated. The leakage current density of a 40nm-STO film was about 5×10−8A/cm2 at 3V.

The effects of a Coulomb-like potential in the Schottky barrier existing between a material-diamond interface is analyzed. The inclusion is intended to mimic the effects of an ionized trap within the barrier, and therefore to account for charge injection into the conduction band of diamond via a Poole-Frenkel transport mechanism. The present treatment is to provide a qualitative account of the increase in current density near the inclusion, which can be substantial. The model is first reduced to an analytically tractable one-dimensional tunneling problem addressable by an Airy Function approach in order to investigate the nature of the effect. A more comprehensive numerical approach is then applied. Finally, statistical arguments are used to estimate emission site densities using the results of the aforementioned analysis.

The electrical and mechanical properties in indium-tin-oxide films deposited on polymer substrate were examined. The materials of substrates are polyethersulfone(PES), polycarbonate(PC), polyethylene terephthalate(PET) which have gas barrier layer and anti-glare coating for plastic-based devices. The experiments were performed by rf-magnetron sputtering using a special instrument and buffer layers. Therefore, we obtained a very flat polymer substrate deposited ITO film and investigated the effects of buffer layers, in addition to the instrument. Moreover, the influences of an oxygen partial pressure and post-deposition annealing in ITO films deposited on polymer substrates were clarified. X-ray diffraction observation, measurement of electrical property, and optical microscope observation were performed for the investigation of micro-structure and electro-mechanical properties. They indicated that as-deposited ITO thin films are amorphous and become quasi-crystalline after adjustment of oxygen partial pressure and thermal annealing above 180 °C. As the results, we obtained 20-25 Ω/ of ITO films with a good transmittance (above 80%) under 0.2 % oxygen contents and vacuum annealing. Furthermore, using organic buffer layer, we obtained ITO films which have rather high electrical resistance (40-45 Ω/ ) but have improved optical (more than 85%) and mechanical characteristics compared to the counterparts.

We studied on the effect of a deposition condition of precursor a-Si thin films on the shape and micro-structure of MILC. The a-Si thin films were prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD) with silane and hydrogen as a source gas and the deposition temperature was varied from 100 to 400∼. The a-Si films deposited at a lower temperature showed a tendency to (111) crystals and leaving some a-Si residues in MILC region, while those with higher deposition temperature tended to be crystallized to (110). These differences were explained in terms of original hydrogen content and following structural changes by the dehydrogenation during annealing.