Beam collimation from field-emitter arrays with linear planar lens

Summary form only given. Many potential applications of field-emitter arrays (FEAs), including field-emitter flat panel displays, would benefit if the emitted electrons could be easily collimated. We report emission data from linear gated silicon emitter arrays with independently controlled planar lens electrodes fabricated by MCNC. The cross section of such an array with adjacent planar lenses is shown schematically in the figure below. A CCD camera mounted on a long focal lens microscope recorded images from a phosphor screen. With the lens electrode tied to the gate electrode, there is no focusing and the electrons produced elliptically shaped images on the phosphor screen. As the lens voltage is reduced relative to the gate voltage, the elliptical images collapse to fine lines and emission current decreases slightly. This reduction in emission current can be restored by increasing the gate voltage by only a few volts without affecting beam collimation. For a 2 mm long 100 tip linear array with gate at 65 V, the unfocused image at the phosphor screen (4.5 mm from the FEA at 1.5 kV) is about 5.5 mm long by 3.5 mm wide. Focused, the half width of the image was less than 100 /spl mu/m wide. For a given lens voltage, the focused images remain the same independent of all tested gate voltages, indicating that the planar lens focusing mechanism is very tolerant. For a range of anode distances, the focused images also remain nearly constant indicating that the depth of the focus is long and the beam quality is good.