Laser-assisted electron emission from gated field-emitters

Enhancement of electron emission by illumination of gated field-emitters was studied using a 100 mW cw YAG laser at a wavelength of 532 nm, intensities up to 107 W/m2 and mechanically chopped with a rise time of 4 μs. When shining an array of 640 silicon emitters, the emission current responded quickly to on–off of the laser. The increase of the emission current was proportional to the basic emission current at low gate voltages, but it was saturated at ≈3 μA as the basic current approached 100 μA with the increase of gate voltage. The emission increase was proportional to the square root of laser power at low gate voltages and to the laser power at elevated gate voltages. For 1- and 3-tip silicon emitters, the rise and fall of the current due to on–off of the laser showed a significant time lag. The magnitude of emission increase was independent of the position of laser spot on the emitter base and reached 2 μA at a basic current of 5 μA without showing signs of saturation. The mechanisms of these phenomena are discussed.