Temperature effects on the structure and mechanical properties of vapor deposited a-SiO2
Temperature effects on the structure and mechanical properties of vapor deposited a-SiO2
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温度对气相沉积a-SiO2结构和力学性能的影响
DOI：
10.1016/j.jnoncrysol.2022.121588
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发表时间：
2022
影响因子：
3.5
通讯作者：
Szlufarska, I.
中科院分区：
文献类型：
--
作者：
Jambur, V.;Molina-Ruiz, M.;Dauer, T.;Horton-Bailey, D.;Vallery, R.;Gidley, D.;Metcalf, T.H.;Liu, X.;Hellman, F.;Szlufarska, I.
非晶二氧化硅（a-SiO2）表现出独特的热机械行为，使其与其他玻璃区别开来。然而，对于这种力学行为与原子结构和a-SiO2的制备条件之间的关系，人们的理解仍然有限。本文采用电子束物理气相沉积（PVD）技术制备了一系列在不同衬底温度下生长的a- sio2薄膜，并结合分子模拟、正电子湮灭寿命谱和纳米压痕实验，建立了薄膜的加工、结构和力学响应之间的关系。具体来说，我们发现生长温度的升高导致薄膜的弹性模量和硬度的增加。膜中的相对孔隙度也增加，同时a- sio2网络本身变得更致密，导致孔隙度增加，但总体密度增加。此外，我们发现a-SiO2薄膜的弹性模量表现出与体a-SiO2相同的反常温度依赖性。然而，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。我们的发现为原子网络结构对a- sio2异常热力学行为的影响提供了新的见解，从而指导了控制a- sio2薄膜的力学性能。
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-SiO2films 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-SiO2network itself becomes denser, resulting in an overall increase in density despite increased porosity. In addition, we found that the a-SiO2films 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-SiO2network 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-SiO2and in turn guidance to control the mechanical properties of a-SiO2films.