接触

晶体各向异性的测量通常需要在多个方向对晶体进行接触，与晶体轴[1]平行和垂直。因此，研究人员要求材料在测量时必须能够实现可靠的电子接触，而且测量后必须能够迅速清除，不在样本表面遗留污染物。常见的粘贴材料（如导电性银胶或导电性碳黑）具有粘贴良好的特性或者包含溶剂，因此不适合此用途。镓的熔点很低（30°C），如果再加入8%的锡，其熔点会降至20°C。另外，镓的表面张力高，这意味着它不会弄湿大多数材料，因此在测量后容易清除。如图2所示，利用测试夹具[2]电极上的镓液滴可以与相当小（小到100µm）的晶体样本进行接触。期间，利用显微镜观察接触区域，并引导镓液滴的位置。

Contacts

Measuring the anisotropic properties of crystals often requires making contact with the same crystal in multiple directions, e.g., parallel and perpendicular to a crystal axis. Therefore, researchers need a material that provides reliable electrical contact, but which can be removed after the measurement is made without leaving contaminants behind on the sample. Typical adhesive materials that “stick well” or contain solvents like conductive silver or carbon are unsuitable. Gallium, a metal with a low melting point of 30°C, provided good results when its melting point was lowered to 20°C by adding 8% tin. Gallium’s high surface tension means it doesn’t wet most materials, so it’s easy to remove after the measurement is made. As Figure 2 shows, contact with the extremely small crystal samples (down to 100μm) was made with drops of liquid gallium placed on the electrodes in the test fixture. A microscope was used to visualize the contact area and guide the positioning of the gallium drops.

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