Tersoff J, Jesson D E, Tang W X
IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598, USA.
Science. 2009 Apr 10;324(5924):236-8. doi: 10.1126/science.1169546.
High-temperature annealing of gallium arsenide in vacuum causes excess evaporation of arsenic, with accumulation of gallium as liquid droplets on the surface. Using real-time in situ surface electron microscopy, we found that these droplets spontaneously run across the crystal surface. Running droplets have been seen in many systems, but they typically require special surface preparation or gradient forces. In contrast, we show that noncongruent evaporation automatically provides a driving force for running droplets. The motion is predicted and observed to slow and stop near a characteristic temperature, with the speed increasing both below and above this temperature. The same behavior is expected to occur during the evaporation of similar III-V semiconductors such as indium arsenide.
砷化镓在真空中进行高温退火会导致砷过度蒸发，镓以液滴形式在表面积聚。通过实时原位表面电子显微镜，我们发现这些液滴会自发地在晶体表面移动。在许多系统中都观察到了移动的液滴，但它们通常需要特殊的表面处理或梯度力。相比之下，我们表明非一致蒸发自动为移动液滴提供了驱动力。预计并观察到该运动会在特征温度附近减慢并停止，在该温度以下和以上速度都会增加。预计在类似的III-V族半导体（如砷化铟）蒸发过程中也会出现相同的行为。
