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arXiv 2204.06103cond-mat.mtrl-sci
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温度对气相沉积a-SiO2结构和力学性能的影响

Temperature effects on the structure and mechanical properties of vapor deposited a-SiO2

Vrishank Jambur, Manel Molina-Ruiz, Tom Dauer, Donez Horton-Bailey, Richard Vallery, David Gidley, Thomas Metcalf, Xiao Liu, Frances Hellman, Izabela Szlufarska

摘要:

无定形二氧化硅(a-SiO2)具有独特的热机械行为,使其有别于其他玻璃。然而,仍然有有限的理解,这种机械行为是如何相关的原子结构和a-SiO2的制备条件。在这里,我们使用电子束(e-beam)物理气相沉积(PVD)制备一系列的a-SiO2薄膜生长在不同的衬底温度,然后结合分子模拟与正电子湮没寿命谱和纳米压痕实验,以建立加工,结构和薄膜的机械响应之间的关系。具体来说,我们发现,在生长温度的增加导致的薄膜的弹性模量和硬度的增加。膜中的相对孔隙率也增加,同时a-SiO2网络本身变得更致密,导致尽管孔隙率增加但密度总体增加。此外,我们发现,a-SiO2薄膜表现出相同的反常的弹性模量的温度依赖性体a-SiO2。然而,发现弹性模量随测量温度的增加速率取决于a-SiO2网络的密度,因此取决于生长温度。我们的研究结果提供了新的见解的原子网络结构的影响,异常的热机械行为的a-SiO2和反过来指导,以控制a-SiO2薄膜的机械性能。

英文摘要:

Amorphous silica (a-SiO2) exhibits unique thermo-mechanical behaviors that set it apart from other glasses. However, there is still limited understanding of how this mechanical behavior is related to the atomic structure and to the preparation conditions of a-SiO2. Here, we used electron beam (e-beam) physical vapor deposition (PVD) to prepare a series of a-SiO2 films grown at different substrate temperatures and then combined molecular simulations with Positronium Annihilation Lifetime Spectroscopy and nanoindentation experiments to establish relations among processing, structure, and mechanical response of the films. Specifically, we found that increase in the growth temperature leads to increase in the elastic moduli and hardness of the films. The relative porosity in the films also increases while the a-SiO2 network itself becomes denser, resulting in an overall increase in density despite increased porosity. In addition, we found that the a-SiO2 films exhibit the same anomalous temperature dependence of elastic modulus as bulk a-SiO2. However, the rate of increase in the elastic modulus with the measurement temperature was found to depend on the density of the a-SiO2 network and therefore on the growth temperature. Our findings provide new insights into the influence of the atomic network structure on the anomalous thermomechanical behavior of a-SiO2 and in turn guidance to control the mechanical properties of a-SiO2 films.

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