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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.

No MeSH data available.


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Full 3D lattice strain tensor after FIB imaging (crystal A).(A) 3D rendering of crystal A coloured by lattice displacement magnitude. Superimposed are the q vectors of the five measured crystal reflections. (B) Coordinate system used for plotting lattice strains and sections on which strains are plotted. The x, y and z axes correspond to [-12-1], [111] and [10-1] crystal directions respectively. (C) and (D) Maps of the six independent lattice strain tensor components on the xy section (red plane in (B)) and yz section (green plane in (B)) through crystal A respectively. (E) Finite element model of crystal A showing the predicted displacement field magnitude. Calculated lattice strain components are plotted on the same xy (F) and yz (G) planes as the experimental data. Scale bars are 300 nm in length.
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f2: Full 3D lattice strain tensor after FIB imaging (crystal A).(A) 3D rendering of crystal A coloured by lattice displacement magnitude. Superimposed are the q vectors of the five measured crystal reflections. (B) Coordinate system used for plotting lattice strains and sections on which strains are plotted. The x, y and z axes correspond to [-12-1], [111] and [10-1] crystal directions respectively. (C) and (D) Maps of the six independent lattice strain tensor components on the xy section (red plane in (B)) and yz section (green plane in (B)) through crystal A respectively. (E) Finite element model of crystal A showing the predicted displacement field magnitude. Calculated lattice strain components are plotted on the same xy (F) and yz (G) planes as the experimental data. Scale bars are 300 nm in length.

Mentions: To further explore these FIB-induced lattice distortions, CXDPs from five reflections were used to reconstruct the full 3D-resolved lattice strain tensor, ε(r), inside crystal A (Fig. 2). The six independent components of ε(r) are shown on virtual xy and yz sections through crystal A (Fig. 2). εyy(r) is large and negative within ~30 nm of the implanted top surface, indicating a lattice contraction due to Ga+ implantation. The εxy(r) (Fig. 2(C)) and εyz(r) (Fig. 2(D)) shear components show more subtle strain features.


3D lattice distortions and defect structures in ion-implanted nano-crystals
Full 3D lattice strain tensor after FIB imaging (crystal A).(A) 3D rendering of crystal A coloured by lattice displacement magnitude. Superimposed are the q vectors of the five measured crystal reflections. (B) Coordinate system used for plotting lattice strains and sections on which strains are plotted. The x, y and z axes correspond to [-12-1], [111] and [10-1] crystal directions respectively. (C) and (D) Maps of the six independent lattice strain tensor components on the xy section (red plane in (B)) and yz section (green plane in (B)) through crystal A respectively. (E) Finite element model of crystal A showing the predicted displacement field magnitude. Calculated lattice strain components are plotted on the same xy (F) and yz (G) planes as the experimental data. 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

f2: Full 3D lattice strain tensor after FIB imaging (crystal A).(A) 3D rendering of crystal A coloured by lattice displacement magnitude. Superimposed are the q vectors of the five measured crystal reflections. (B) Coordinate system used for plotting lattice strains and sections on which strains are plotted. The x, y and z axes correspond to [-12-1], [111] and [10-1] crystal directions respectively. (C) and (D) Maps of the six independent lattice strain tensor components on the xy section (red plane in (B)) and yz section (green plane in (B)) through crystal A respectively. (E) Finite element model of crystal A showing the predicted displacement field magnitude. Calculated lattice strain components are plotted on the same xy (F) and yz (G) planes as the experimental data. Scale bars are 300 nm in length.
Mentions: To further explore these FIB-induced lattice distortions, CXDPs from five reflections were used to reconstruct the full 3D-resolved lattice strain tensor, ε(r), inside crystal A (Fig. 2). The six independent components of ε(r) are shown on virtual xy and yz sections through crystal A (Fig. 2). εyy(r) is large and negative within ~30 nm of the implanted top surface, indicating a lattice contraction due to Ga+ implantation. The εxy(r) (Fig. 2(C)) and εyz(r) (Fig. 2(D)) shear components show more subtle strain features.

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