Formation of Self-Oriented Nanocrystals in an Amorphous Alloy under Focused-Ion-Beam Irradiation

在室温下，利用聚焦离子束（FIB）在Ni-P非晶合金中形成了晶体取向纳米晶体（NCs）。通过透射电子显微镜观察辐照平面，发现在整个辐照区域形成nc。通过一系列的电子衍射分析，确定了形成的NCs的结构为Ni的面心立方（fcc），并确定了形成的NCs的取向：辐照面法向||<111>fcc， FIB方向||<110>fcc。形成的nc由两个具有孪生关系的变体组成，孪生平面为辐照平面。这些与孪晶相关的晶体具有类畴结构，平均畴尺寸约为200 nm。非晶合金的弹性各向异性不影响形成的非晶合金的晶体学特征。从晶体学和几何的角度讨论了控制纳米颗粒取向的特征。本文还研究了Ni-P非晶合金辐照面入射FIB角对NCs晶体学特征的影响。平行于非晶膜方向辐照时，形成纳米晶，而垂直于非晶膜方向辐照时，未形成纳米晶。这表明先前形成的纳米晶体可以在垂直于非晶膜方向的FIB照射下被擦除。我们利用这种技术成功地制作了纳米晶体的图案化。在FIB辐照前，通过低于结晶温度的预热处理，尝试控制纳米晶体晶粒尺寸的可能性。

We have formed oystallographically oriented nanosized crystals(NCs) in a Ni-P amorphous alloy using focused-ion-beam(FIB) irradiation at room temperature. Transmission electron microscopy observations of the irradiated plane revealed the formation of NCs throughout the irradiated area. From a series of electron diffraction analyses, the structure of the formed NCs was determined to be face-centered cubic(fcc) of Ni and the following orientation of the formed NCs was confirmed : Irradiated plane normal ||<111>fcc, and FIB direction ||<110>fcc. The formed NCs consisted of two variants which have a twin relation, the twinning plane being the irradiated plane. These twin related crystals have a domain-like microstructure with an average domain size of approximately 200 nm. The elastic anisotropy of the amorphous alloy does not affect the crystallographic features of the formed NCs. The features which control the orientation of the formed NCs are discussed from crystallographic and geometrical points of view. Changes in the crystallographic features of the NCs as a function of the incident FIB angle on the irradiated plane of Ni-P amorphous alloy have been also investigated. When irradiating parallel to the amorphous film, nanocrystals were formed, whereas nanocrustals were not formed when irradiating perpendicular to the amorphous film. This suggests that nancrystals, which had been formed previously, can be erased by FIB irradiation from perpendicular to the amorphous film. We have succeeded the patterning of nanocrystals using this technique. The possibility of grain size control of nanocrystals is also attempted by pre-heat treatments below crystallization temperature before FIB irradiation.