| 1. |
- Fallqvist, Amie
(författare)
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Aberration-Corrected Analytical Electron Microscopy of Transition Metal Nitride and Silicon Nitride Multilayers
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two multilayer thin films have been studied: TiN/SiNx and ZrN/SiNx. A double-corrected transmission electron microscope (TEM) was utilized for imaging and spectroscopy. Imaging was carried out in scanning mode (STEM) for all samples. Energy dispersive X-ray (EDX) spectrometry was used for chemical mapping of the ZrN/SiNx samples and electron energy loss spectrometry (EELS) for atomic coordination of the nitrogen in the TiN/SiNx samples.In the TiN/SiNx multilayer the structure of the epitaxially stabilized cubic SiNx was investigated. The high-resolution STEM images were compared with image simulations of SiNx in B1 (sodium chloride) and B3 (zinc blende) configurations and were found to be most similar to the B1 configuration. Core-loss EEL spectra were compared with calculated spectra and corroborated a resemblance with the B1 configuration.The ZrN/SiNx multilayers were initially believed to show a similarity to TiN/SiNx but further investigations with STEM showed that the SiNx is amorphous. For samples deposited at 800 °C a SiNx layer thickness ≤6 Å the SiNx forms precipitates at grain boundaries and surface defects of the ZrN resulting in a columnar distribution of the SiNx, which was further revealed by EDX. For such samples the ZrN grows by epitaxial lateral overgrowth. For samples deposited at 800 °C but with a SiNx layer thickness of 6 Å the SiNx starts to form more laterally extending layers and for thicknesses ≥8 Å the SiNx grows into continuous, amorphous layers causing the following ZrN layers to assume a polycrystalline microstructure. The transition from epitaxial ZrN with columnar, amorphous SiNx, to multilayers of polycrystalline ZrN and amorphous SiNx layers appears at an even smaller thickness of SiNx if the deposition temperature is lowered, which is explained by the lowered adatom mobility.
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| 2. |
- Fallqvist, Amie, et al.
(författare)
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Evidence for B1-cubic SiNx by Aberration-Corrected Analytical STEM
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The crystal structure of epitaxially stabilized SiNx layers on TiN(001) was investigated by analytical aberration corrected electron microscopy. Atomically resolved images of the structure, which were acquired by scanning transmission electron microscopy using high angle annular dark field and annular bright field detectors, are used to identify the B1-cubic structure of SiNx. To corroborate the acquired images, image simulations were performed using candidate structures. Complementary to imaging, spatially resolved electron energy loss spectroscopy of the epitaxial SiNx layers was performed to acquire the symmetry specific nitrogen near edge fine-structure. Finally, full potential calculations performed to determine the near edge structure from candidate crystal structures confirms the existence of B1-cubic SiNx.
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| 3. |
- Fallqvist, Amie, et al.
(författare)
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Optically addressable field effect nano-environments for chemical imaging
- 2009
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Ingår i: Procedia Chemistry. - : ELSEVIER SCIENCE BV. - 1876-6196. ; 1:1, s. 224-227
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Tidskriftsartikel (refereegranskat)abstract
- An optically addressable field effect device Incorporating functionalized nano-environments is demonstrated for the generation of multiple response signatures of a same analyte-sensing material combination. The device can operate unsupervised and different response mechanism can be simultaneously tested and incorporated in a multidimensional response. This proof of concept explores the well-known Pd-H-2 case, while the concept is a breadboard for chemical imaging experiments.
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| 4. |
- Fallqvist, Amie, et al.
(författare)
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Resolving the debated atomic structure of the metastable cubic SiNx tissue phase in nanocomposites with TiN
- 2018
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Ingår i: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 2:9
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Tidskriftsartikel (refereegranskat)abstract
- The TiN/SiNx nanocomposite and nanolaminate systems are the archetype for super if not ultrahard materials. Yet, the nature of the SiNx tissue phase is debated. Here, we show by atomically resolved electron microscopy methods that SiNx is epitaxially stabilized in a NaCl structure on the adjacent TiN(001) surfaces. Additionally, electron energy loss spectroscopy, supported by first-principles density functional theory calculations infer that SiNx hosts Si vacancies.
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| 5. |
- Fallqvist, Amie, et al.
(författare)
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Self-organization during Growth of ZrN/SiNx Multilayers by Epitaxial Lateral Overgrowth
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 114:224302
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Tidskriftsartikel (refereegranskat)abstract
- ZrN/SiNx nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiNx thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiNx is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiNx – known to take place on TiN(001) – on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiNx deposition, the material segregates to form surface precipitates in discontinuous layers for SiNx thicknesses ≤ 6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiNx precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiNx in samples deposited at 800 °C with up to 6 Å thick SiNx layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1-3 nm large SiNx precipitates along apparent column boundaries in the epitaxial ZrN.
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