Conductive dots, wires, and supertips for field electron emitters produced by electron-beam induced deposition on samples having increased temperature

Abstract

The procedure for three-dimensional additive lithography with electron-beam induced deposition is applied in a scanning electron microscope equipped with an image processor beam control system for lithography. Employing organometallic materials, which contain gold or platinum, quantum dots, resistors, and field emitter tips are deposited. Changing the current, the properties of the deposited nanocrystalline compound materials can be selected to be insulating or conducting. High resolution and high aspect ratio structures are grown with this technique. To find the mechanism responsible for conductivity in the deposited material, resistors are characterized at temperatures ranging from −150 °C to +180 °C. Measurements are performed in a high-vacuum chamber equipped with a gas cooling system cooled with liquid nitrogen and a resistive heater. Poole–Frenkel plots show that field electron emission and hopping of electrons is the dominant mechanism of conduction. The metal content of the deposits is increased with rising sample temperatures ranging from room temperature to 100 °C. The deposited material features zero-dimensional electron gas in the nanocrystals of the material. Conductive tips with very small tip radius are routinely deposited as supertips on top of etched tungsten tips at elevated temperatures. The tips are investigated in an ultrahigh vacuum field electron microscope. Working supertips have a confined emission and therefore enhanced brightness is obtained routinely. The increase in brightness is at least ninefold for an emission from one site having a confined emission angle of ±7.2°. The emission current may be as large as 10 μA at extraction voltages below 800 V. No single crystalline tip material is needed to generate these supertips. Beam confinement to one emission site is demonstrated the first time for a deposited supertip.