Abstract Recent investigations on ternary diborides revealed their enormous potential for the use as protective thin films. Within this study we investigate DC magnetron sputtered V 1 − x WxB2 thin films (with x = 0, 0.05, 0.13, 0.21) concerning their morphology, structure, mechanical properties, and thermal stability. A b − i n i t i o calculations revealed, that while the equilibrium state of VB2 is the AlB2-prototype (α-type), that of WB2 is the W2B 5 − x -prototype (ω-type). However, when considering the formation of point defects such as vacancies, the preferred structure of WB2 can even be α, while that of VB2 remains with α. This allows for the formation of metastable α-WB2 – and especially ternary α-V 1 − x WxB2, which are stable with respect to their constituting α-VB2 and α-WB2 phases (as suggested by DFT and vacuum annealing for 1h at 1400∘ C)even without considering point defects – when using physical vapor deposition, as thereby the point defect concentration is typically high. Our results further show that the highest W-containing ternary coating, V0.69W0.21B2 (which is still single-phase α-structured with a hardness of ∼ 40 GPa combined with low tensile stresses of 0.3 Pa in the as deposited state) exhibits the highest hardness of ∼ 43 GPa and ∼ 40 GPa after 1-h-vacuum annealing at 1000 and 1400∘ C, respectively, among all coatings studied. Their indentation modulus ( ∼ 500 GPa) and also their microstructure (single-phase α-structure, pronounced 0001-orientation, column diameter of 14.7 nm) showed no significant changes up to 1000∘ C.

中文翻译：

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热稳定的超硬二硼化物：大众二硼化物薄膜从头开始的案例研究

摘要 最近对三元二硼化物的研究揭示了它们作为保护薄膜的巨大潜力。在这项研究中，我们研究了直流磁控溅射 V 1 - x WxB2 薄膜（x = 0、0.05、0.13、0.21）的形态、结构、机械性能和热稳定性。A b - initio 计算表明，虽然 VB2 的平衡状态是 AlB2 原型（α 型），但 WB2 的平衡状态是 W2B 5 - x 原型（ω 型）。然而，当考虑空位等点缺陷的形成时，WB2的优选结构甚至可以是α，而VB2的结构仍然是α。这允许形成亚稳态α-WB2——尤其是三元α-V 1 - x WxB2，即使不考虑点缺陷，它们在构成 α-VB2 和 α-WB2 相方面也是稳定的（如 DFT 所建议的，在 1400∘ C 下真空退火 1 小时），即使不考虑点缺陷——当使用物理气相沉积时，因此点缺陷浓度为通常高。我们的结果进一步表明，含 W 最高的三元涂层 V0.69W0.21B2（仍为单相 α 结构，硬度约为 40 GPa，在沉积状态下具有 0.3 Pa 的低拉伸应力）表现出在所研究的所有涂层中，在 1000 和 1400 ∘ C 下真空退火 1 小时后，最高硬度分别为 ~ 43 GPa 和 ~ 40 GPa。它们的压痕模量 (∼ 500 GPa) 以及它们的微观结构（单相 α 结构，明显的 0001 取向，柱直径为 14.7 nm）在 1000∘ C 之前没有显着变化。