Double spiral steps on Ih ice crystal surfaces grown from water vapor just below the melting point
Double spiral steps on Ih ice crystal surfaces grown from water vapor just below the melting point
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由熔点以下的水蒸气生长而成的 Ih 冰晶表面上的双螺旋台阶
DOI：
10.1021/cg4014448
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发表时间：
2014
影响因子：
3.8
通讯作者：
Y. Furukawa
中科院分区：
文献类型：
--
作者：
G. Sazaki;H. Asakawa;K. Nagashima;S. Nakatsubo;Y. Furukawa
在冰晶生长过程中，螺旋生长是主导冰晶生长的重要生长机制之一。然而，在接近熔点的温度下，冰晶表面的螺旋台阶结构尚未被确定。在这里，我们展示了一种可能的模型结构，即从低于0°C的水蒸气中生长的冰晶的基面上和棱柱面上的螺旋台阶。我们利用先进的光学显微镜在现场观察了螺旋台阶和二维（2D）岛屿台阶的合并，该显微镜可以可视化冰基面上二维岛屿的单个基本台阶（单层高度）。我们发现，螺旋阶梯和二维岛状阶梯在基面和棱镜面上都显示出单双层高度，尽管由于晶体学要求，两个面上的螺旋位错的Burgers矢量需要具有双双层高度。这些结果表明，在螺旋生长丘的中心，相邻的两个单层台阶重合，形成双双层台阶，随着螺旋台阶半径的增大，两个单层台阶逐渐分离。在- 15.0°C（我们设置的最低温度）下，我们观察到双螺旋台阶的出现，这有力地支持了我们的模型结构。
During the growth of ice crystals, spiral growth is one of the important growth mechanisms that dominate their growth. However, the structure of spiral steps on ice crystal surfaces at temperatures near the melting point has not been identified. Here we show a possible model structure of spiral steps on basal and prism faces of Ihice crystals grown from water vapor just below 0 °C. We observed in situ the coalescences of spiral steps and steps of two-dimensional (2D) islands by our advanced optical microscopy, which can visualize individual elementary steps (single-bilayer height) of 2D islands on ice basal faces. We found that both spiral steps and 2D island steps on basal and prism faces show single-bilayer heights, though Burgers’ vectors of screw dislocations on both faces need to have double-bilayer heights because of a crystallographic requirement. These results suggest that at the center of a spiral growth hillock, steps of two adjacent single bilayers coincide and then form a double-bilayer step and that the steps of two single bilayers gradually detach themselves with increasing radii of their spiral steps. We observed the appearance of double spiral steps, which strongly supports our model structure, at −15.0 °C (the lowest temperature of our setup).