Crovetto Andrea, Kojda Danny, Yi Feng, Heinselman Karen N, LaVan David A, Habicht Klaus, Unold Thomas, Zakutayev Andriy
Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany.
J Am Chem Soc. 2022 Jul 27;144(29):13334-13343. doi: 10.1021/jacs.2c04868. Epub 2022 Jul 13.
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 CuP films by a two-step process involving reactive sputtering of amorphous CuP and rapid annealing in an inert atmosphere. At the crystallization temperature, CuP is thermodynamically unstable with respect to CuP and P. However, CuP can 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 CuP, combined with a short annealing time, makes it possible to bypass the diffusion processes responsible for decomposition. We find that thin-film CuP is a 1.5 eV band gap semiconductor with interesting properties, such as a high optical absorption coefficient (above 10 cm), 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.
从固态化学文献中可知，有许多富含磷的金属磷化物同时含有P-P键和金属-P键。生长这些薄膜形式材料的方法将是很有必要的，因为在许多应用中都需要薄膜，而且它们是高通量研究的理想平台。此外，薄膜可实现的高密度和平滑表面对于传输和光学性质的表征是一个显著优势。尽管有这些好处，但即使是最简单的富含磷的二元磷化物薄膜，也几乎没有任何已发表的研究工作。在此，我们通过两步法展示了单相CuP薄膜的生长，该方法包括非晶态CuP的反应溅射和在惰性气氛中的快速退火。在结晶温度下，相对于CuP和P，CuP在热力学上是不稳定的。然而，如果非晶态前驱体在原子尺度上混合且足够接近所需组成（既不过度贫P也不过度富P），则CuP可以被稳定下来。多晶CuP的快速形成，再加上较短的退火时间，使得有可能绕过导致分解的扩散过程。我们发现薄膜CuP是一种带隙为1.5 eV的半导体，具有一些有趣的特性，如高光吸收系数（高于10 cm）、低热导率（1.1 W/(K m)）和对组成不敏感的电导率（约1 S/cm）。我们预计我们的加工路线可以扩展到其他仍在等待薄膜合成的富含磷的磷化物，并将有助于更全面地了解这些材料及其潜在应用。
