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3D lattice distortions and defect structures in ion-implanted nano-crystals

View Article: PubMed Central - PubMed

ABSTRACT

Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. By manipulating a tightly focussed beam of energetic ions, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life, earth and materials sciences. Despite its widespread usage, detailed understanding of the FIB-induced structural damage, intrinsic to the technique, remains elusive. Here we examine the defects caused by FIB in initially pristine objects. Using Bragg Coherent X-ray Diffraction Imaging (BCDI), we are able to spatially-resolve the full lattice strain tensor in FIB-milled gold nano-crystals. We find that every use of FIB causes large lattice distortions. Even very low ion doses, typical of FIB imaging and previously thought negligible, have a dramatic effect. Our results are consistent with a damage microstructure dominated by vacancies, highlighting the importance of free-surfaces in determining which defects are retained. At larger ion fluences, used during FIB-milling, we observe an extended dislocation network that causes stresses far beyond the bulk tensile strength of gold. These observations provide new fundamental insight into the nature of the damage created and the defects that lead to a surprisingly inhomogeneous morphology.

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Strains induced by extensive FIB milling (crystal D).(A) 3D rendering of crystal D coloured according to the measured lattice displacement magnitude. Superimposed are the q vectors of the six reflections measured from this crystal. (B) Crystal coordinates and sections on which strains are plotted. The x, y and z axes correspond to [2-1-1], [111] and [0-11] crystal directions respectively. (C) and (D) show the six components of the experimentally measured strain tensor plotted on xy and yz sections through the crystal (shown in (B) coloured red and green respectively). Scale bars are 300 nm in length.
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f5: Strains induced by extensive FIB milling (crystal D).(A) 3D rendering of crystal D coloured according to the measured lattice displacement magnitude. Superimposed are the q vectors of the six reflections measured from this crystal. (B) Crystal coordinates and sections on which strains are plotted. The x, y and z axes correspond to [2-1-1], [111] and [0-11] crystal directions respectively. (C) and (D) show the six components of the experimentally measured strain tensor plotted on xy and yz sections through the crystal (shown in (B) coloured red and green respectively). Scale bars are 300 nm in length.

Mentions: Our findings show that every use of FIB to image or shape material causes large lattice distortions. Fundamental insight into the underlying damage mechanisms can be gained by combining coherent X-ray measurements with numerical calculations. Surprisingly, FIB-induced lattice strains are not confined to the ion-damaged layer, but can extend far into the material bulk, as visible in crystal C. This is further highlighted by measurements of crystal D into which a central hole was FIB-machined, and which exhibits large strains even far from the ion-damaged surfaces (Fig. 5). These extensive strains may explain the dramatic changes in mechanical properties caused by FIB milling113536.


3D lattice distortions and defect structures in ion-implanted nano-crystals
Strains induced by extensive FIB milling (crystal D).(A) 3D rendering of crystal D coloured according to the measured lattice displacement magnitude. Superimposed are the q vectors of the six reflections measured from this crystal. (B) Crystal coordinates and sections on which strains are plotted. The x, y and z axes correspond to [2-1-1], [111] and [0-11] crystal directions respectively. (C) and (D) show the six components of the experimentally measured strain tensor plotted on xy and yz sections through the crystal (shown in (B) coloured red and green respectively). Scale bars are 300 nm in length.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382701&req=5

f5: Strains induced by extensive FIB milling (crystal D).(A) 3D rendering of crystal D coloured according to the measured lattice displacement magnitude. Superimposed are the q vectors of the six reflections measured from this crystal. (B) Crystal coordinates and sections on which strains are plotted. The x, y and z axes correspond to [2-1-1], [111] and [0-11] crystal directions respectively. (C) and (D) show the six components of the experimentally measured strain tensor plotted on xy and yz sections through the crystal (shown in (B) coloured red and green respectively). Scale bars are 300 nm in length.
Mentions: Our findings show that every use of FIB to image or shape material causes large lattice distortions. Fundamental insight into the underlying damage mechanisms can be gained by combining coherent X-ray measurements with numerical calculations. Surprisingly, FIB-induced lattice strains are not confined to the ion-damaged layer, but can extend far into the material bulk, as visible in crystal C. This is further highlighted by measurements of crystal D into which a central hole was FIB-machined, and which exhibits large strains even far from the ion-damaged surfaces (Fig. 5). These extensive strains may explain the dramatic changes in mechanical properties caused by FIB milling113536.

View Article: PubMed Central - PubMed

ABSTRACT

Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. By manipulating a tightly focussed beam of energetic ions, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life, earth and materials sciences. Despite its widespread usage, detailed understanding of the FIB-induced structural damage, intrinsic to the technique, remains elusive. Here we examine the defects caused by FIB in initially pristine objects. Using Bragg Coherent X-ray Diffraction Imaging (BCDI), we are able to spatially-resolve the full lattice strain tensor in FIB-milled gold nano-crystals. We find that every use of FIB causes large lattice distortions. Even very low ion doses, typical of FIB imaging and previously thought negligible, have a dramatic effect. Our results are consistent with a damage microstructure dominated by vacancies, highlighting the importance of free-surfaces in determining which defects are retained. At larger ion fluences, used during FIB-milling, we observe an extended dislocation network that causes stresses far beyond the bulk tensile strength of gold. These observations provide new fundamental insight into the nature of the damage created and the defects that lead to a surprisingly inhomogeneous morphology.

No MeSH data available.


Related in: MedlinePlus