Examinando por Autor "Sanchez-Perez, Clara"

Mostrando 1 - 10 de 10

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).
Aerosol-assisted route to low-E transparent conductive gallium-doped zinc oxide coatings from pre-organized and halogen-free precursor
(Royal Society of Chemistry, 2020) Sanchez-Perez, Clara; Dixon, Sebastian C; Darr, Jawwad A; Parkin, Ivan P; Carmalt, Claire J
Thermal control in low-emission windows is achieved by the application of glazings, which are simultaneously optically transparent in the visible and reflective in the near-infrared (IR). This phenomenon is characteristic of coatings with wide optical band gaps that have high enough charge carrier concentrations for the material to interact with electromagnetic radiation in the IR region. While conventional low-E coatings are composed of sandwiched structures of oxides and thin Ag films or of fluorinated SnO2 coatings, ZnO-based glazing offers an environmentally stable and economical alternative with competitive optoelectronic properties. In this work, gallium-doped zinc oxide (GZO) coatings with properties for low-E coatings that exceed industrial standards (Tvisible > 82%; R2500 nm > 90%; λ(plasma) = 1290 nm; ρ = 4.7 × 10−4 Ω cm; Rsh = 9.4 Ω·□−1) are deposited through a sustainable and environmentally friendly halogen-free deposition route from [Ga(acac)3] and a pre-organized zinc oxide precursor [EtZnOiPr]4 (1) via single-pot aerosol-assisted chemical vapor deposition. GZO films are highly (002)-textured, smooth and compact without need of epitaxial growth. The method herein describes the synthesis of coatings with opto-electronic properties commonly achievable only through high-vacuum methods, and provides an alternative to the use of pyrophoric ZnEt2 and halogenated SnO2 coatings currently used in low-emission glazing and photovoltaic technology.
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.
Engineering of ultra-thin sintered porous silicon virtual substrates for lattice-mismatched growth compliance and epilayer detachability
(Elsevier, 2022) Sanchez-Perez, Clara; Hernandez-Castro, Mauricio; Garcia, Ivan
The air-sensitivity of mesoporous silicon layers etched on p-type wafers was evaluated comparing ambientoxidized to methyl-capped samples, from which the unaltered pore/interpore sizes were obtained and linked to diffraction patterns and reflectivity data. Sintering of oxide-free nano/mesoporous bilayers produced ultrathin porous epi-foils with full surface reconstruction at temperatures below 1000 ◦C. The epi-foils were inplane tensely strained and exhibited good crystallinity and polished wafer-like surface roughness (RMSmin = 0.23 nm), emerging as potential compliant substrates for crack-free epitaxy of flat heterostructures. Furthermore, they were conveniently formed over a weakly bonded macroporous mesh that provided both structural stability and ease for detachment, establishing sintering below 1000 ◦C as a promising route to avoid collapsing and premature delamination of ultra-thin films.
Fast chemical thinning of germanium wafers for optoelectronic applications
(Elsevier, 2022-03-30) Sanchez-Perez, Clara; Garcia, Ivan; Rey-Stolle, Ignacio
Chemical thinning of germanium wafers was carried out in H3PO4:HNO3:HF aqueous solutions, in which etch rates and surface morphology was adjusted through changes in etchant dilution and viscosity. Pitless and smooth surfaces (RMS = 0.42 nm) were obtained at industrially acceptable rates via a diffusion-controlled mechanism. Etchant-resistant wax enabled reversible bonding to a polypropylene substrate, emerging as a potential route for industrial production of thinned germanium optoelectronics.
High-throughput continuous-flow system for SABRE hyperpolarization
(Academic Press Elsevier, 2019) Štěpánek, Petr; Sanchez-Perez, Clara; Telkki, Ville-Veikko; Zhivonitko, Vladimir V; Kantola, Anu M
Signal Amplification By Reversible Exchange (SABRE) is a versatile method for hyperpolarizing small organic molecules that helps to overcome the inherent low signal-to-noise ratio of nuclear magnetic resonance (NMR) measurements. It offers orders of magnitude enhanced signal strength, but the obtained nuclear polarization usually rapidly relaxes, requiring a quick transport of the sample to the spectrometer. Here we report a new design of a polarizing system, which can be used to prepare a continuous flow of SABRE-hyperpolarized sample with a considerable throughput of several millilitres per second and a rapid delivery into an NMR instrument. The polarizer performance under different conditions such as flow rate of the hydrogen or liquid sample is tested by measuring a series of NMR spectra and magnetic resonance images (MRI) of hyperpolarized pyridine in methanol. Results show a capability to continuously produce sample with dramatically enhanced signal over two orders of magnitude. The constant supply of hyperpolarized sample can be exploited, e.g., in experiments requiring multiple repetitions, such as 2D- and 3D-NMR or MRI measurements, and also naturally allows measurements of flow maps, including systems with high flow rates, for which the level of achievable thermal polarization might not be usable any more. In addition, the experiments can be viably carried out in a non-deuterated solvent, due to the effective suppression of the thermal polarization by the fast sample flow. The presented system opens the possibilities for SABRE experiments requiring a long-term, stable and high level of nuclear polarization.
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.
Precursors for Atmospheric Plasma‐Enhanced Sintering: Low‐Temperature Inkjet Printing of Conductive Copper
(Wiley, 2018) Knapp, Caroline E; Metcalf, Elisabeth A; Mrig, Shreya; Sanchez-Perez, Clara; Douglas, Samuel P; Choquet, Patrick; Boscher, Nicolas D
Bidentate diamine and amino-alcohol ligands have been used to form solid, water-soluble, and air-stable monomeric copper complexes of the type [Cu(NH2CH2CH(R)Y)2(NO3)2] (1, R=H, Y=NH2; 2, R=H, Y=OH; 3, R=Me, Y=OH). The complexes were characterized by elemental analysis, mass spectrometry, infrared spectroscopy, thermal gravimetric analysis, and single-crystal X-ray diffraction. Irrespective of their decomposition temperature, precursors 1–3 yield highly conductive copper features [1.5×10−6 Ω m (±5×10−7 Ω m)] upon atmospheric-pressure plasma-enhanced sintering.
Scalable Production of Ambient Stable Hybrid Bismuth‐Based Materials: AACVD of Phenethylammonium Bismuth Iodide Films
(Wiley, 2021) Wang, Mingyue; Sanchez-Perez, Clara; Habib, Faiza; Blunt, M O; Carmalt, Claire J
Large homogeneous and adherent coatings of phenethylammonium bismuth iodide were produced using the cost-effective and scalable aerosol-assisted chemical vapor deposition (AACVD) methodology. The film morphology was found to depend on the deposition conditions and substrates, resulting in different optical properties to those reported from their spin-coated counterparts. Optoelectronic characterization revealed band bending effects occurring between the hybrid material and semiconducting substrates (TiO2 and FTO) due to heterojunction formation, and the optical bandgap of the hybrid material was calculated from UV-visible and PL spectrometry to be 2.05 eV. Maximum values for hydrophobicity and crystallographic preferential orientation were observed for films deposited on FTO/glass substrates, closely followed by values from films deposited on TiO2/glass substrates.