Searching for low-workfunction phases in the Cs-Te system: the case of Cs2Te5

TL;DR

This study computationally investigates the workfunction of Cs2Te5, identifying a low-workfunction surface with potential for high quantum efficiency in photoemission, and compares its properties to related materials.

Contribution

It reveals a low-workfunction surface in Cs2Te5 covered with Cs atoms, expanding the understanding of low-workfunction materials in the Cs-Te system.

Findings

Cs2Te5(010) surface with Cs coverage has ~1.9 eV workfunction

Cs2Te5 contains quasi one-dimensional polytelluride substructures

Low-workfunction surface less energetically favored than in Cs2TeC2

Abstract

We have computationally explored workfunction values of Cs2Te5, an existing crystalline phase of the Cs-Te system and a small bandgap semiconductor, in order to search for reduced workfunction alternatives of Cs2Te that preserve the exceptionally high quantum efficiency of the Cs2Te seasoned photoemissive material. We have found that the Cs2Te5(010) surface exhibits a workfunction value of ~ 1.9 eV when it is covered by Cs atoms. Cs2Te5 is analogous to our recently proposed low-workfunction materials, Cs2TeC2 and other ternary acetylides [J. Z. Terdik, et al., Phys. Rev. B 86, 035142 (2012)], in as much as it also contains quasi one-dimensional substructures embedded in a Cs-matrix, forming the foundation for anomalous workfunction anisotropy, and low workfunction values. The one-dimensional substructures in Cs2Te5 are polytelluride ions in a tetragonal rod packing. Cs2Te5 has the advantage of simpler composition and availability as compared to Cs2TeC2, however its low workfunction surface is less energetically favored to the other surfaces than in Cs2TeC2.