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

我们利用聚焦离子束(FIB)在室温下在Ni-P非晶态合金中形成了具有晶体取向的纳米晶体(NCS)。对辐照平面的透射电子显微镜观察表明，整个辐照区域都形成了NCS。由一系列电子衍射分析确定了所形成的NCS的结构为面心立方(FCC)，并确定了所形成的NCS的以下取向：辐照平面法线||&lt；111&gt；fcc和FIB方向||&lt；110&gt；fcc。形成的NCS由两个具有孪晶关系的变体组成，孪晶面是被辐照的面。这些孪晶相关晶体具有磁区状微结构，平均磁区尺寸约为200 nm。非晶态合金的弹性各向异性不影响形成的NCS的结晶学特征。从结晶学和几何角度讨论了控制NCS取向的特征。还研究了Ni-P非晶态合金辐照面上NCS的结晶学特征随入射FIB角的变化。当平行于非晶膜照射时，纳米晶形成，而当垂直于非晶膜照射时，不形成纳米晶。这表明，FIB辐照可以从垂直于非晶膜的方向擦除先前形成的纳米晶。我们已经使用这种技术成功地形成了纳米晶体的图案化。通过在FIB辐照前进行低于晶化温度的预热处理，也尝试了控制纳米晶体晶粒度的可能性。

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.