Effect of microstructure on spontaneous polarization in amorphous solid water films
Effect of microstructure on spontaneous polarization in amorphous solid water films
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DOI：
10.1063/1.4916322
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发表时间：
2015-04-07
影响因子：
4.4
通讯作者：
Baragiola, Raul A.
中科院分区：
文献类型：
--
作者：
Bu, Caixia;Shi, Jianming;Baragiola, Raul A.
在110K以下用气相沉积方法生长的非晶态固体水薄膜相对于衬底产生负的表面电压V-S。这种极化是由于冷凝过程中水分子的部分排列造成的。开尔文探针测量表明，表面电势的大小，垂直条V-S垂直条随膜厚呈线性增加，而增加的速度随沉积温度的升高而减小。垂直条V-S垂直条随沉积温度的升高和气源入射角的增大而减小。冰膜生长后，当冰膜温度高于沉积温度约30K时，垂直条V-S垂直条不可逆地减少了80%。垂直线条V-S垂直线条随薄膜孔隙率的变化表明，ASW中的极化是由不完全配位的水分子控制的，在孔的内表面悬挂着不平衡的偶极子，并受到各向异性薄膜-真空界面的弱取向。这一观点得到了垂直棒V-S垂直棒惊人相似行为的支持，以及由于具有最柔韧的、随退火温度变化的两配位表面分子而产生的红外吸收。(C)2015 AIP出版有限责任公司。
Amorphous solid water (ASW) films grown by vapor deposition below 110 K develop negative surface voltages V-s with respect to the substrate. This polarization is due to a partial alignment of the water molecules during condensation. Kelvin probe measurements show that the magnitude of the surface potential, vertical bar V-s vertical bar, increases linearly with film thickness at a rate that decreases with increasing deposition temperature. vertical bar V-s vertical bar decreases with increasing deposition temperature and increasing incidence angle of the vapor source. After film growth, vertical bar V-s vertical bar decreases irreversibly by 80% when the ice film is heated to similar to 30 K above the deposition temperature. The measurements of vertical bar V-s vertical bar as a function of film porosity indicate that polarization in ASW is governed by incompletely coordinated water molecules, dangling with unbalanced dipoles at the internal surface of the pores and weakly aligned by the anisotropic film-vacuum interface. This idea is supported by the strikingly similar behavior of vertical bar V-s vertical bar and the infrared absorption due to the most pliable, two-coordinated surface molecules with annealing temperature. (C) 2015 AIP Publishing LLC.