Examinando por Autor "Oilunkaniemi, Raija"

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Accessing new 2D semiconductors with optical band gap: synthesis of iron-intercalated titanium diselenide thin films via LPCVD
(Royal Society of Chemistry, 2018-06-20) Sanchez-Perez, Clara; Knapp, Caroline E; Colman, Ross H; Sotelo-Vazquez, Carlos; Oilunkaniemi, Raija; Laitinen, Risto S; Carmalt, Claire J
Fe-doped TiSe2 thin-films were synthesized via low pressure chemical vapor deposition (LPCVD) of a single source precursor: [Fe(η5-C5H4Se)2Ti(η5-C5H5)2]2 (1). Samples were heated at 1000 °C for 1–18 h and cooled to room temperature following two different protocols, which promoted the formation of different phases. The resulting films were analyzed by grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and UV/vis spectroscopy. An investigation of the Fe doping limit from a parallel pyrolysis study of FexTiSe2 powders produced in situ during LPCVD depositions has shown an increase in the Fe–TiSe2–Fe layer width with Fe at% increase. Powders were analyzed using powder X-ray diffraction (PXRD) involving Rietveld refinement and XPS. UV/vis measurements of the semiconducting thin films show a shift in band gap with iron doping from 0.1 eV (TiSe2) to 1.46 eV (Fe0.46TiSe2).
Chalcogen–chalcogen secondary bonding interactions in trichalcogenaferrocenophanes
(Royal Society of Chemistry, 2016-04-29) Karjalainen, Minna M.; Sanchez-Perez, Clara; Rautiainen, J. Mikko; Oilunkaniemi, Raija; Laitinen, Risto S.
The solid-state structures of all members in the series of trichalcogenaferrocenophanes [FeĲC5H4E)2E′] (E, E′ = S, Se, Te) (1–9) have been explored to understand the trends in secondary bonding interactions (SBIs) between chalcogen elements sulfur, selenium, and tellurium. To complete the series, the crystal structures of the four hitherto unknown complexes [Fe(C5H4S)2Te] (3), [Fe(C5H4Se)2S] (4), [Fe(C5H4Se)2Te] (6), and [Fe(C5H4Te)2S] (7) have been determined in this contribution. The packings of all complexes 1–9 were considered by DFT calculations at the PBE0/pob-TZVP level of theory using periodic boundary conditions. The intermolecular close contacts were considered by QTAIM and NBO analyses. The isomorphous complexes [Fe(C5H4S)2S] (1), [Fe(C5H4S)2Se] (2), and [Fe(C5H4Se)2Se] (5a) form dimers via weak interactions between the central chalcogen atoms of the two trichalcogena chains of adjacent complexes. In the second isomorphous series consisting of [Fe(C5H4Se)2S] (4) and 5b, the complexes are linked together into continuous chains by short contacts via the terminal selenium atoms. The intermolecular chalcogen–chalcogen interactions are significantly stronger in complexes [Fe(C5H4S)2Te] (3), Fe(C5H4Se)2Te] (6), and [Fe(C5H4Te)2E′] (E′ = S, Se, Te) (7–9), which contain tellurium. The NBO comparison of donor–acceptor interactions in the lattices of [Fe(C5H4S)2S] (1), [Fe(C5H4Se)2Se] (5a and 5b), and [Fe(C5H4Te)2Te] (9) indeed shows that the n(5pTe) 2 → σ*(Te–Te) interactions in 9 are the strongest. All other interaction energies are significantly smaller even in the case of tellurium. The computed natural charges of the chalcogen atoms indicate that electrostatic effects strengthen the attractive interactions in the case of all chalcogen atoms.
Iron-Intercalated Zirconium Diselenide Thin Films from the Low-Pressure Chemical Vapor Deposition of [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2
(American Chemical Society Publications, 2020) Sanchez-Perez, Clara; Knapp, Caroline E; Colman, Ross H; Sotelo-Vazquez, Carlos; Sathasivam, Sanjayan; Oilunkaniemi, Raija; Laitinen, Risto S; Carmalt, Claire J
Transition metal chalcogenide thin films of the type FexZrSe2 have applications in electronic devices, but their use is limited by current synthetic techniques. Here, we demonstrate the synthesis and characterization of Fe-intercalated ZrSe2 thin films on quartz substrates using the low-pressure chemical vapor deposition of the single-source precursor [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2. Powder X-ray diffraction of the film scraping and subsequent Rietveld refinement of the data showed the successful synthesis of the Fe0.14ZrSe2 phase, along with secondary phases of FeSe and ZrO2. Upon intercalation, a small optical band gap enhancement (Eg(direct)opt = 1.72 eV) is detected in comparison with that of the host material.
Macrocycles containing 1, 1′-ferrocenyldiselenolato ligands on group 4 metallocenes
(Royal Society of Chemistry, 2018) Sanchez-Perez, Clara; Knapp, Caroline E; Karjalainen, Minna M; Oilunkaniemi, Raija; Carmalt, Claire J; Laitinen, Risto S
Macrocyclic [Fe(η5-C5H4Se)2M(η5-C5H4R)2]2 [M = Ti (1), Zr (2), Hf (3), R = H; and M = Zr (4), Hf (5), R = tBu] were prepared and characterized by 77Se NMR spectroscopy and the crystal structures of 1–3 and 5 were determined by single-crystal X-ray diffraction. The crystal structure of 4 is known and the complex is isomorphous with 5. 1–5 form mutually similar macrocyclic tetranuclear complexes in which the alternating Fe(C5H4Se)2 and M(C5H4R)2 centers are linked by selenium bridges. The thermogravimetric analysis (TGA) of 1–3 under a helium atmosphere indicated that the complexes undergo a two-step decomposition upon heating. The final products were identified using powder X-ray diffraction as FexMSe2, indicating their potential as single-source precursors for functional materials.