The Photoemission of Electrons onto Superfluid Helium

Abstract

Single electrons can be transported across billions of pixels in a chargecoupled device (CCD) constructed on superfluid helium, due to its high surface mobility. The electrons can be stored at specified locations within the CCD to an extreme degree of accuracy, and it is thought that the electron spin coherence on superfluid helium may have a long lifetime, enabling it to serve as the basis for a quantum computer. To place the electrons on the surface of the superfluid helium, a cryogenic photoemissive source is used [1]. In the past, zinc films, as a result of their ease of preparation and relatively low work function, served as the target for UV radiation to emit electrons. Yet, when zinc is exposed to air, its photocurrent decreases, sending fewer electrons to the helium. Organic thin films deposited onto zinc have been shown to reduce the work function and protect against corrosion, increasing both the photocurrent and its stability when exposed to air [2]. In the following paper, I report the experimental setup I conducted for testing this novel approach, and the necessary steps for the conclusion of the project. In addition, I preface the experimental description by detailing the underlying Fowler theory of photoemission and the behavior of electrons on the surface of superfluid helium.