Evolution of thermodynamic potentials in closed and open nanocrystalline systems:: Ge-Si:Si(001) islands
Evolution of thermodynamic potentials in closed and open nanocrystalline systems:: Ge-Si:Si(001) islands
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DOI：
10.1103/physrevlett.100.226101
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发表时间：
2008-06-06
影响因子：
8.6
通讯作者：
Medeiros-Ribeiro, G.
中科院分区：
文献类型：
--
作者：
Leite, Marina S.;Malachias, A.;Medeiros-Ribeiro, G.
通过生长动力学实现了一个开放（封闭）系统，其中物质通过表面扩散进行（不）交换。对外延生长的Si-Ge：Si（001）岛在不同的退火环境中进行退火，选择性地影响Si原子的扩散率。混合的驱动力，而接近平衡的演变推断从同步辐射X射线测量的组成和应变。对于开放系统，由于硅从润湿层（水库）流入的混合引起的Ge含量的减少，导致弹性能的降低和混合熵的增加。相反，对于封闭系统，同时保持平均Ge组成不变，原子重排内的岛屿导致增加弹性和熵的贡献。吉布斯自由能下降，在这两种情况下，尽管不同的演化路径的组成配置文件。
An open (closed) system, in which matter is (not) exchanged through surface diffusion, was realized via growth kinetics. Epitaxially grown Si-Ge:Si (001) islands were annealed in different environments affecting the diffusivity of Si adatoms selectively. The evolution of the driving forces for intermixing while approaching the equilibrium was inferred from Synchrotron x-ray measurements of composition and strain. For the open system, intermixing due to the Si inflow from the wetting layer (reservoir) caused a decrease in the Ge content, leading to a lowering of the elastic energy and an increase in the mixing entropy. In contrast, for the closed system, while keeping the average Ge composition constant, atom rearrangement within the islands led to an increase in both elastic and entropic contributions. The Gibbs free energy decreased in both cases, despite the different evolution paths for the composition profiles.