Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM
Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM
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DOI：
10.1111/j.1365-2818.2010.03471.x
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发表时间：
2011-06
影响因子：
2
通讯作者：
I. Weikusat;D. D. Winter-D.;G. Pennock;M. Hayles;C. Schneijdenberg;M. Drury
中科院分区：
文献类型：
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作者：
I. Weikusat;D. D. Winter-D.;G. Pennock;M. Hayles;C. Schneijdenberg;M. Drury
自然变形的冰含有具有特征几何形状的亚颗粒，这些亚颗粒最近已在蚀刻表面中使用高分辨率光学显微镜（LM）进行了鉴定。负责这些亚晶界类型的可能的滑移系统可以使用电子背散射衍射（EBSD）确定，提供的蚀刻功能与反射LM成像可以保留在EBSD数据采集过程中的扫描电子显微镜（SEM）。保留蚀刻特征需要冰表面稳定。根据压力和温度，冰的升华可能发生。在1 × 10−6 hPa下工作的低压SEM的平衡温度约为−112°C，在更高温度下工作会导致升华。虽然未涂覆的冰样品的充电通过升华而减少，但是当表面升华时，蚀刻特征中包含的重要信息被去除。我们开发了一种方法，收集EBSD数据稳定的冰面在低压扫描电镜。我们发现，在<-112 ° C的温度下操作减少了升华，从而保留了原始蚀刻表面特征。在低压（<1.5 × 10−6至2.8 × 10−5 hPa）下发生的充电通过使电子束散焦而减少。在非常低的压力（<1.5 × 10 - 6 hPa）下，10 kV离焦束的空间分辨率在-150 °C时x方向约为3 μm，在-120 °C时约为0.5 μm，因为在较高的温度下，充电较少，只需要很小的散焦来补偿它。取向平均后的角分辨率优于0.7°。LM蚀刻特征和EBSD映射的微观结构之间获得了极好的一致性。第一个结果显示，这表明亚晶界类型包括基底（倾斜和扭曲）和非基底位错（倾斜边界）。
Naturally deformed ice contains subgrains with characteristic geometries that have recently been identified in etched surfaces using high‐resolution light microscopy (LM). The probable slip systems responsible for these subgrain boundary types can be determined using electron backscattered diffraction (EBSD), providing the etch features imaged with reflected LM can be retained during EBSD data acquisition in a scanning electron microscope (SEM). Retention of the etch features requires that the ice surface is stable. Depending on the pressure and temperature, sublimation of ice can occur. The equilibrium temperature for a low pressure SEM operating at 1 × 10−6 hPa is about −112°C and operating at higher temperatures causes sublimation. Although charging of uncoated ice samples is reduced by sublimation, important information contained in the etch features are removed as the surface sublimes. We developed a method for collecting EBSD data on stable ice surfaces in a low pressure SEM. We found that operating at temperatures of <–112°C reduced sublimation so that the original etch surface features were retained. Charging, which occurred at low pressures (<1.5 × 10−6 to 2.8 × 10−5 hPa) was reduced by defocusing the beam. At very low pressures (<1.5 × 10−6 hPa) the spatial resolution with a defocused beam at 10 kV was about 3 μm in the x‐direction at −150°C and 0.5 μm at −120°C, because at higher temperature charging was less and only a small defocus was needed to compensate it. Angular resolution was better than 0.7° after orientation averaging. Excellent agreement was obtained between LM etch features and EBSD mapped microstructures. First results are shown, which indicate subgrain boundary types comprised of basal (tilt and twist) and nonbasal dislocations (tilt boundaries).