Eric R. Dickey

High rate roll to roll atomic layer deposition, and its application to moisture barriers on polymer films

Atomic layer deposition has been shown to provide high quality single layer moisture barrier films on polymer substrates, but conventional pulse-based processes are too slow to be commercially feasible. One way to overcome this speed limitation is to avoid the need to pulse and purge precursors by moving the substrate between zones containing the precursors, passing through intermediate purge zones. Recently, several groups have reported various approaches to accomplishing this, including the approach discussed here in which the flexible web is passed between precursor zones in a serpentine pattern. Al2O3 and TiO2 barrier films 12 to 20 nm thick with water vapor transmission rates in the range of 10−4 g/m2/day have been demonstrated for web speeds in excess of 1 m/s on 100 mm wide polyethylene terephthalate web. Scale-up of this process to 300 mm wide web in a system capable of depositing 10–20 nm of film in a single pass is currently under way. This scale-up effort and the potential for very high volume,...

A Polysilicon Active Matrix Organic Light Emitting Diode Display with Integrated Drivers

The design of an active matrix organic light emitting diode (AMOLED) display using a polysilicon thin film transistor pixel is described. Characteristics of the OLED response in the low current regime are described and their impact on the design of integrated driver circuitry is discussed. Integrated data and select scanners which generate the signals necessary for data capture and pixel calibration are presented.

Electrical characterization of blue electroluminescent devices

A new class of blue thin-film electroluminescent (TFEL) devices based on thiogallate phosphors has been reported recently. The purpose of this work reported herein is to compare and contrast the electrical properties of CaGa2S4:Ce TFEL blue phosphor devices to those of conventional evaporated ZnS:Mn TFEL devices. Capacitance-voltage (C-V) and internal charge-phosphor field (Q-Fp) techniques are employed for electrical characterization.

High-performance alkaline-earth thiogallate blue-emitting ACTFEL devices

Significant improvement in the luminescent performance of Sr x Ca 1-x Ga 2 S 4 :Ce (0 < x < 1) EL devices was achieved by optimizing the Sr/Ca ratio and oxygen doping. The key factor for improvement is oxygen doping of thiogallate thin films. Microstructural analysis from x-ray diffraction and transmission electron microscopy showed that oxygen doping increased crystal grain size and induced a preferred orientation along (602) planes. Photoluminescence studies showed the luminescence decay time increased with oxygen doping, indicating the suppression of non-radiative energy transitions at structural defects, e.g., sulfur vacancies, due to improved crystalline quality of the thiogallate thin films. The emission color blue shift in oxygen-doped Sr-Ca mixed thiogallate was attributed to the preferential substitution of Ce 3+ for Sr 2+ rather than Ca 2+ due to a better match of ion size and a possible ordering effect from lattice strain introduced by oxygen incorporation. The threshold-field reduction and steeper turn-on near threshold in oxygen-doped devices was considered to be a result of the introduction of shallow trapping states at the insulator/phosphor interface and the elimination of bulk trapping states by oxygen doping.

Blue And Yellow Light Emitting Phosphors For Thin Film Electroluminescent Displays

Following a description of the purpose and participating members in the Phosphor Technology Center of Excellence, research on the growth and characterization of modulation doped ZnS:Mn and of Ca 0.95 Sr 0.05 Ga 2 S 4 :6%Ce are reported. ZnS:Mn has been grown using MOCVD and incorporation of Mn in 1 to 5 layers from 5 to 20 nm thick separated by layers of pure ZnS from 5 to 50 nm thick. This is shown to result in lower threshold voltages for ACTFELD displays. The luminescence spectra from sputter deposited, cerium-doped thiogallate thin films were measured and the diffusion of thin ZnS passivation layers versus temperature of heat treatment was discussed.