Cb Thomas

Modeling the fluorescent lifetime of Y2O3:Eu

Phosphor thermography, relying on the temperature dependence of the decay time of photoluminescence from suitable phosphors, provides remote measurement of the temperature of components. Such a phosphor is yttrium oxide doped with europium (Y2O3:Eu). Associated with this phosphor is also a rise time. Demonstrated is that the rise time is also temperature dependent, as a result of known electronic transitions within the Eu ions. For the phosphor Y2O3:Eu (3.4 at.%), the rise time is an activated process in the temperature region between 25 and 850u2009°C. Faster than the decay time, the rise time offers the opportunity for measurement of higher velocity components.

A thin film coating for phosphor thermography

Phosphor thermography is a laser-induced fluorescence method utilized for the temperature sensing of rotating components within inhospitable environments. Results presented here show that thin film coatings for thermographic sensors have a much higher durability than conventional thick film coatings. Room-temperature measurements demonstrate that the intensity of the luminescent emission from thin films is equivalent to that from thick films. Lifetime measurements carried out at C show that thin films survived for up to ten hours, whereas thick film samples survived for less than one. More importantly, post-run measurements of thin films indicate little degradation in the intensity of the fluorescent signal. This illustrates the capability of thin film sensors for remote temperature sensing.

Characterisation of the BaTiO3/p-Si interface and applications

Barium titanate (BaTiO3), because of its high dielectric constant ( er), has proven to be a very promising candidate for use as dielectric layer in ac thin film electroluminescent (ACTFEL) devices and for use in thin film hybrid and integrated circuits. In the present work, BaTiO3 films were deposited on p-Si (100) substrates by rf-magnetron sputtering at a base temperature of 200°C. The electronic properties of the BaTiO3/p-Si interface were examined by means of admittance spectroscopy on metal–insulator–semiconductor (MIS) devices fabricated by thermal evaporation of Al. The density of interface states (Dit) was calculated by both the capacitive and the conductive response of the traps; values of the order of 1012 eV−1 cm−2 were obtained for the Dit and values of 10−5 s were calculated for the relevant time constants of the traps. These values, together with the dielectric constant of the films ranging between 40 and 60, show that the deposited films were suitable for use as cladding insulators in ACTFEL devices.

Properties of barium titanate (BaTiO3) thin films grown on silicon by rf magnetron sputtering

Abstract Thin films of BaTiO3 were deposited on p-Si substrates by rf magnetron sputtering in order to investigate their suitability for use in ac thin film electroluminescent (ACTFEL) devices and dynamic RAM (DRAM) applications. Post-growth annealing at 700°C and the subseauent deposition of Al contacts resulted in the creation of Al/BaTiO3/p-Si metal-insulator-semiconductor devices. The electronic and structural properties of the films were examined by admittance spectroscopy, current-voltage and transient current measurements, and X-ray diffraction (XRD) characterization. Analysis of the XRD spectra showed the polycrystalline nature of the films but also the presence of an amorphous phase. The electrical measurements revealed a high dielectric constant, around 60, a charge storage capacity exceeding 3 μC cm−2 and a total charge trapped inside the oxide of around 50 nC cm−2 while the density of traps at the BaTiO3/p-Si interface was found to be as high as 1 × 1012 cm−2 eV−1. These results indicate that the films are suitable for both DRAM and ACTFEL applications.

Characterization of BaTiO3 thin films on p-Si

Abstract Polycrystalline BaTiO3 thin films grown on p-Si (1xa00xa00) substrates by RF sputtering and subjected to a post-thermal annealing at 700°C, were characterized for potential applications as cladding insulators in AC thin-film electroluminescent devices. Building such a device requires the study of an insulator/semiconductor and an insulator/phosphor interface. The study of the BaTiO3 surface in the present work provides information on the creation of defects due to the deposition process. Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy were used to investigate the surface and bulk created defects. They showed the existence of Ba and Ti oxides formed on the surface probably due to the post thermal annealing. These oxides may be responsible for the creation of interface states between the BaTiO3 film and the subsequent deposited ZnS films in order to build an AC thin-film electroluminescent device.

P-169: Optimization of the Electrical and Optical Properties of Ink-Jet-Printed SnO(2):Sb using Thermal Annealing and Excimer-Laser Processing

Sb doped SnO2 has been formulated and inkjet printed onto borosilicate glass substrates. The resultant films have been post processed using traditional thermal annealing up to 440°C and laser processing with a KrF excimer laser (λ = 248nm). Sheet resistance values of 700Ω/□ have been achieved with thermal annealing, whilst transparency remains >85% in the visible region. As a result of laser processing significant decreases in sheet resistance of the inkjet printed layers have been demonstrated indicating the viability of inkjet printing onto flexible substrates. The optical transmittance of the laser processed films has been shown to remain >85%. Initial measurements indicate that thermal and laser post processes reduce surface roughness.

A comparison of the outcoupling characteristics of laterally emitting thin-film electroluminescent devices

This paper presents a study of the light output characteristics of laterally emitting thin-film electroluminescent (LETFEL) devices. The limitations of the conventional non-etched LETFEL outcoupling mechanism have been theoretically and experimentally analysed. The theoretical approach assumes the device behaves as a perfect optical waveguide and studies the scattering and bend radiation losses responsible for outcoupling at the aperture locations. This study leads to outcoupling efficiency values under 2%. Additionally, the angular profile has been experimentally determined and illustrates two maxima at ±50°. As a result, we conclude that the conventional non-etched LETFEL output characteristics are not optimum for the two main LETFEL applications, which are head mounted displays (HMD) and electrophotographic printing (EP). Consequently, an alternative outcoupling mechanism is introduced, which is referred to as the etched LETFEL device. This has been fabricated for the first time, using ion milling. The resultant light output characteristics have been experimentally determined and subsequently compared with the conventional non-etched structure properties. A 400% enhancement in the total emitted light intensity has been obtained for a 600xa0V peak to peak driving voltage, using the etched structure. Additionally, the angular profile is observed to redistribute towards narrower angles of view. This introduces further enhancement of the coupling efficiency of HMD and EP applications, with acceptance angles under 30 and 6° respectively, by 12 and 5% respectively.

Ion milling properties of laterally emitting thin-film electroluminescent materials

A study has been undertaken of the ion milling properties of ZnS:Mn, Y/sub 2/O/sub 3/, Si/sub 3/N/sub 4/, SiO/sub 2/, SiO/sub x/N/sub y/, and Al versus the etching time, the acceleration voltage, and the angle of incidence of the ion beam. Different ZnS:Mn etched profiles have been fabricated by modifying the angle of incidence; these are in agreement with the reported simulations.

P-32: Feasibility of Laterally-Emitting Thin-Film Electroluminescent (LETFEL) Devices for an Opto-Electronic Integrated Circuit (OEIC)

The feasibility of developing the Laterally-Emitting Thin-Film Electroluminescent (LETFEL) device for an Opto-Electronic Integrated Circuit (OEIC)—a LETFEL device with its corresponding on-board electronic driver—has been investigated as an alternative low-cost, high-resolution, high-intensity, integrated light source for optical image applications.