Alkali semi-metal films and method and apparatus for fabricating them
Methods and systems for fabricating a film, such as, for example, a photocathode, having a tailored band structure and thin-film components that can be tailored for specific applications, such as, for example photocathode having a high quantum efficiency, and simple components fabricated by those methods.
1. An apparatus for fabricating a thin film component, the thin film component being a photocathode, the apparatus comprising: a deposition subsystem configured to deposit a pre-synthesized semi-metal compound material on a substrate; wherein the apparatus comprises a pre-synthesized semi-metal compound material source providing a target material; the pre-synthesized semi-metal compound material source having pre-synthesized semi-metal compound material loaded therein; the pre-synthesized semi-metal compound material comprising at least two alkali materials, the two alkali materials comprising potassium (K) and cesium (Cs); the pre-synthesized semi-metal compound material comprising a semi-metal material comprising antimony (Sb); the pre-synthesized semi-metal compound material comprising K 2 CsSb; the pre-synthesized semi-metal compound material being a polycrystalline powder; wherein the deposition subsystem comprises a sputtering apparatus.
2. An apparatus for fabricating a thin film component, comprising: a deposition subsystem configured to deposit a pre-synthesized semi-metal compound material on a substrate; wherein the apparatus comprises a pre-synthesized semi-metal compound material source providing a target material; the pre-synthesized semi-metal compound material source comprising an evaporation crucible into which pre-synthesized semi-metal compound material is loaded; the deposition subsystem comprising a pulsed laser deposition apparatus; the pre-synthesized semi-metal compound material comprising at least two alkali materials and a semi-metal material; the pre-synthesized semi-metal compound material being polycrystalline; the pre-synthesized semi-metal compound material having crystallite size from about 15 nm to about 30 nm.
3. The apparatus of claim 2 further comprising a characterization member configured to measure a quantum efficiency of the photocathode in real time of photocathode deposition.
4. The apparatus of claim 3 , wherein the characterization member comprises:
a light source for generating a light of a wavelength;
an anode; and
an electric circuit coupled between the anode and the photocathode for measuring a photocurrent in response to the light from the light source to obtain the quantum efficiency.
5. The apparatus of claim 4 , wherein the anode comprises a metallic ring configured to stay remote from a photocathode source material and proximate the deposited photocathode.
6. The apparatus of claim 2 , further comprising a feedback member coupled to the deposition subsystem and a member chosen from at least one of a characterization member or a thickness sensing member; said feedback member configured to adjust a parameter, the parameter being at least one of temperature of the deposition subsystem, temperature of the substrate or deposition rate in accordance with measurements by the member.
7. The apparatus of claim 2 wherein the at least two alkali materials comprise a first alkali material and a second alkali material.