Coherent-to-semi-coherent transition of precipitates in niobium-hydrogen thin films
Coherent-to-semi-coherent transition of precipitates in niobium-hydrogen thin films
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DOI：
10.1103/physrevb.78.014105
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发表时间：
2008-07-01
影响因子：
3.7
通讯作者：
Pundt, Astrid
中科院分区：
文献类型：
--
作者：
Noerthemann, Kai;Pundt, Astrid
以铌氢（Nb-H）为模型体系研究了薄膜中的成核和生长。薄膜中的氢化物沉淀会导致局部表面形貌变化，可以通过扫描隧道显微镜进行监测。局部薄膜膨胀可用于检测氢化物沉淀物，研究其生长，以获得有关其形状和晶格相干性的信息。借助理论计算，将表明圆柱形 Nb-H 析出物在早期阶段演化。只要薄膜很薄并且氢化物尺寸低于临界体积，这些沉淀物就会与基质相干。超过这个临界体积，就会发生相干到半相干的转变。临界尺寸由相干沉淀物中存储的弹性能与位错形成所需的能量之间的平衡控制。因此，厚度低于 26 nm 的薄膜保持所有氢化物沉淀体积的相干性，并且永远不会成为半相干性。
Nucleation and growth in thin films are studied by using niobium-hydrogen (Nb-H) as model system. Hydride precipitation in thin films results in local surface topography changes that can be monitored by scanning tunneling microscopy. The local film expansion can be used to detect hydride precipitates, to study their growth, to gain information about their shape and their lattice coherency. With the help of theoretical calculations, it will be shown that cylindrical Nb-H precipitates evolve in early stages. These precipitates are coherent to the matrix as long as the film is thin and the hydride size is below a critical volume. Above this critical volume, a coherent-to-semi-coherent transition occurs. The critical size is controlled by the balance between the elastic energy stored in the coherent precipitate and the energy needed for the formation of dislocations. Consequently, films below 26 nm thickness keep coherency for all hydride precipitate volumes and never get semi-coherent.