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Nanoscale characterization of local structures and defects in photonic crystals using synchrotron-based transmission soft X-ray microscopy.

Nho HW, Kalegowda Y, Shin HJ, Yoon TH - Sci Rep (2016)

Bottom Line: Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components.Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated.This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul, 04763, Republic of Korea.

ABSTRACT
For the structural characterization of the polystyrene (PS)-based photonic crystals (PCs), fast and direct imaging capabilities of full field transmission X-ray microscopy (TXM) were demonstrated at soft X-ray energy. PS-based PCs were prepared on an O2-plasma treated Si3N4 window and their local structures and defects were investigated using this label-free TXM technique with an image acquisition speed of ~10 sec/frame and marginal radiation damage. Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components. Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated. This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties.

No MeSH data available.


Related in: MedlinePlus

(A) TXM transmission image of triple layered PCs (scale bar of 1 μm). Internal line defect shown in blue dash box, and line and point defects on the surface denoted as the red dash box and red star, respectively. (B) The bottom (the first layer), (C) middle (the second layer) and (D) top layers (the third layer) of reconstructed image.
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f4: (A) TXM transmission image of triple layered PCs (scale bar of 1 μm). Internal line defect shown in blue dash box, and line and point defects on the surface denoted as the red dash box and red star, respectively. (B) The bottom (the first layer), (C) middle (the second layer) and (D) top layers (the third layer) of reconstructed image.

Mentions: As described above, point or line defects of PCs could be easily found by TXM technique. However, it is also true that we could not determine the 3D location of those line or point defects by using 2D TXM images. Additionally, as mentioned in the previous section, it is also not feasible to determine the stacking sequences of PC structures (e.g., ABAC or ABCA) from only 2D TXM images. Generally, SEM images of cross-sectioned PC samples have been used to identify the 3D locations of point or line defects in PCs. However, this sample preparation process may cause artefacts during destructive cross-sectioning procedure. Therefore, we have applied 3D tomographic reconstruction approach to find 3D locations of line or point defects of PCs and presented in Fig. 4. To reconstruct a complete 3D tomographic image, it is typically necessary to acquire a few tens or hundreds of 2D images with different tilting angles. However, in this study, we have acquired 2D TXM images with 9 different tilting angles and reconstructed 3D tomographic TXM image, which was found sufficient to determine the colloidal layer containing the line or point defects. As shown in Fig. 4B–D, individual layer of PCs could be identified by observing virtually sectioned plane in the reconstructed tomographic image. By using this tomographic technique, we could determine the layers containing various defects without destructive sample preparation process. As shown in Fig. 4A,B, the domain boundary between FCC and HCP was induced by the line defect in the first layer of the PCs (see blue dashed box in Fig. 4A,B). However, this dislocation was not propagated to the second (Fig. 4C) or the third layer (Fig. 4D). In general, line defects formed by successive dislocation of particles can modify the crystal structures of PCs and generate misaligned structures or grain boundaries28, which was in good agreement with our observation shown in Fig. 4. These observations demonstrated that the 3D tomographic TXM technique is useful for the characterization of 3D locations of defects in PCs. Additionally, we have confirmed that it is more practical and efficient to use TXM technique, rather than STXM techniques, when characterizing local structures and defects of PCs via 3D tomographic study of PCs, due to the faster image acquisition capability of TXM technique over STXM technique.


Nanoscale characterization of local structures and defects in photonic crystals using synchrotron-based transmission soft X-ray microscopy.

Nho HW, Kalegowda Y, Shin HJ, Yoon TH - Sci Rep (2016)

(A) TXM transmission image of triple layered PCs (scale bar of 1 μm). Internal line defect shown in blue dash box, and line and point defects on the surface denoted as the red dash box and red star, respectively. (B) The bottom (the first layer), (C) middle (the second layer) and (D) top layers (the third layer) of reconstructed image.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834481&req=5

f4: (A) TXM transmission image of triple layered PCs (scale bar of 1 μm). Internal line defect shown in blue dash box, and line and point defects on the surface denoted as the red dash box and red star, respectively. (B) The bottom (the first layer), (C) middle (the second layer) and (D) top layers (the third layer) of reconstructed image.
Mentions: As described above, point or line defects of PCs could be easily found by TXM technique. However, it is also true that we could not determine the 3D location of those line or point defects by using 2D TXM images. Additionally, as mentioned in the previous section, it is also not feasible to determine the stacking sequences of PC structures (e.g., ABAC or ABCA) from only 2D TXM images. Generally, SEM images of cross-sectioned PC samples have been used to identify the 3D locations of point or line defects in PCs. However, this sample preparation process may cause artefacts during destructive cross-sectioning procedure. Therefore, we have applied 3D tomographic reconstruction approach to find 3D locations of line or point defects of PCs and presented in Fig. 4. To reconstruct a complete 3D tomographic image, it is typically necessary to acquire a few tens or hundreds of 2D images with different tilting angles. However, in this study, we have acquired 2D TXM images with 9 different tilting angles and reconstructed 3D tomographic TXM image, which was found sufficient to determine the colloidal layer containing the line or point defects. As shown in Fig. 4B–D, individual layer of PCs could be identified by observing virtually sectioned plane in the reconstructed tomographic image. By using this tomographic technique, we could determine the layers containing various defects without destructive sample preparation process. As shown in Fig. 4A,B, the domain boundary between FCC and HCP was induced by the line defect in the first layer of the PCs (see blue dashed box in Fig. 4A,B). However, this dislocation was not propagated to the second (Fig. 4C) or the third layer (Fig. 4D). In general, line defects formed by successive dislocation of particles can modify the crystal structures of PCs and generate misaligned structures or grain boundaries28, which was in good agreement with our observation shown in Fig. 4. These observations demonstrated that the 3D tomographic TXM technique is useful for the characterization of 3D locations of defects in PCs. Additionally, we have confirmed that it is more practical and efficient to use TXM technique, rather than STXM techniques, when characterizing local structures and defects of PCs via 3D tomographic study of PCs, due to the faster image acquisition capability of TXM technique over STXM technique.

Bottom Line: Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components.Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated.This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul, 04763, Republic of Korea.

ABSTRACT
For the structural characterization of the polystyrene (PS)-based photonic crystals (PCs), fast and direct imaging capabilities of full field transmission X-ray microscopy (TXM) were demonstrated at soft X-ray energy. PS-based PCs were prepared on an O2-plasma treated Si3N4 window and their local structures and defects were investigated using this label-free TXM technique with an image acquisition speed of ~10 sec/frame and marginal radiation damage. Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components. Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated. This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties.

No MeSH data available.


Related in: MedlinePlus