Crystallize It Before It Diffuses: Kinetic Stabilization of Thin-Film Phosphorus-Rich Semiconductor CuP2

Andrea Crovetto, Danny Kojda, Feng Yi, Karen N. Heinselman, David A. Lavan, Klaus Habicht, Thomas Unold, Andriy Zakutayev

Research output: Contribution to journalArticlepeer-review

7 Scopus Citations

Abstract

Numerous phosphorus-rich metal phosphides containing both P-P bonds and metal-P bonds are known from the solid-state chemistry literature. A method to grow these materials in thin-film form would be desirable, as thin films are required in many applications and they are an ideal platform for high-throughput studies. In addition, the high density and smooth surfaces achievable in thin films are a significant advantage for characterization of transport and optical properties. Despite these benefits, there is hardly any published work on even the simplest binary phosphorus-rich phosphide films. Here, we demonstrate growth of single-phase CuP2films by a two-step process involving reactive sputtering of amorphous CuP2+xand rapid annealing in an inert atmosphere. At the crystallization temperature, CuP2is thermodynamically unstable with respect to Cu3P and P4. However, CuP2can be stabilized if the amorphous precursors are mixed on the atomic scale and are sufficiently close to the desired composition (neither too P poor nor too P rich). Fast formation of polycrystalline CuP2, combined with a short annealing time, makes it possible to bypass the diffusion processes responsible for decomposition. We find that thin-film CuP2is a 1.5 eV band gap semiconductor with interesting properties, such as a high optical absorption coefficient (above 105cm-1), low thermal conductivity (1.1 W/(K m)), and composition-insensitive electrical conductivity (around 1 S/cm). We anticipate that our processing route can be extended to other phosphorus-rich phosphides that are still awaiting thin-film synthesis and will lead to a more complete understanding of these materials and of their potential applications.

Original languageAmerican English
Pages (from-to)13334-13343
Number of pages10
JournalJournal of the American Chemical Society
Volume144
Issue number29
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

NREL Publication Number

  • NREL/JA-5K00-83300

Keywords

  • crystallization
  • layered
  • metastable
  • phosphide

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