Beam focusing for field-emission flat-panel displays

A combination of finite element and finite difference techniques have been used to simulate the performance of micro-fabricated gated field emitters for flat-panel display applications. The computer model has been verified against both analytic models and experimental data for unfocused devices and then applied to the study of focused structures for which sufficient models and data are not yet available. Quantitative results include electrode current-voltage characteristics and electron beam widths as a function of distance from the cathode. Practical issues such as visual image quality, electrical stress and fabrication complexity are considered to identify a practical design for use in conjunction with existing high-efficiency cathode ray tube phosphors. It is found that the addition of an integrated aperture electrode to focus the emitted electrons increases the cathode-gate drive voltage by about 30% over the case of unfocused emitters. A concentric electrode design results in only 15% increase and promises simpler fabrication. Both approaches demonstrate electron beam widths of tens of microns at anode distances of several millimeters, allowing for full-color resolution in excess of 100 lines per inch with proven color phosphors.<
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