Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, Illinois 61801, USA.
Phys Rev Lett. 2011 Jun 10;106(23):235501. doi: 10.1103/PhysRevLett.106.235501.
Amorphous silicon is an important material, amidst a debate whether or not it is a glass. We produce amorphous Si surfaces by ion bombardment and vapor growth, and image discrete Si clusters which hop by two-state dynamics at 295 K. Independent of surface preparation, these clusters have an average diameter of ∼5 atoms. Given prior results for metallic glasses, we suggest that this cluster size is a universal feature. The hopping activation free energy of 0.93±0.15 eV is rather small, in agreement with a previously untested surface glass model. Hydrogenation quenches the two-state dynamics, apparently by increasing surface crystallinity.
非晶硅是一种重要的材料，人们对其是否为玻璃存在争议。我们通过离子轰击和气相生长来制备非晶硅表面，并在 295K 下通过两态动力学成像离散的硅团簇。这些团簇的平均直径约为 5 个原子，与表面制备无关。考虑到金属玻璃的先前结果，我们认为这种团簇尺寸是普遍存在的特征。跃迁激活自由能为 0.93±0.15eV，相当小，与之前未经测试的表面玻璃模型一致。氢化会抑制两态动力学，显然是通过增加表面结晶度来实现的。
