Marek Jura

Bio: Marek Jura is an academic researcher from Rutherford Appleton Laboratory. The author has contributed to research in topics: Thin film & Raman spectroscopy. The author has an hindex of 16, co-authored 44 publications receiving 674 citations. Previous affiliations of Marek Jura include University of Bath & University of Southampton.

Highly Selective Chemical Vapor Deposition of Tin Diselenide Thin Films onto Patterned Substrates via Single Source Diselenoether Precursors

Abstract: The distorted octahedral complexes [SnCl4{nBuSe(CH2)nSenBu}] (n = 2 or 3), (1) and (2), obtained from reaction of SnCl4 with the neutral bidentate ligands and characterized by IR/Raman and multinuclear (1H, 77Se{1H} and 119Sn) NMR spectroscopy and X-ray crystallography, serve as very effective single source precursors for low pressure chemical vapor deposition (LPCVD) of microcrystalline, single phase tin diselenide films onto SiO2, Si and TiN substrates. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) imaging show hexagonal plate crystallites which grow perpendicular to the substrate surface in the thicker films, but align mostly parallel to the surface when the quantity of reagent is reduced to limit the film thickness. X-ray diffraction (XRD) and Raman spectroscopy on the deposited films are consistent with hexagonal SnSe2 (P3m1; a = b = 3.81 A; c = 6.13 A), with strong evidence for preferred orientation of the crystallites in thinner (0.5–2 μm) samples, consistent with crystal pl...

Effect of oxidative surface treatments on charge storage at titanium nitride surfaces for supercapacitor applications

Abstract: The effects of surface oxidation on the capacitance of titanium nitride electrode surfaces, produced by reaction of titanium foils with ammonia, are examined. Thermal oxidation and electrochemical oxidation both increase the amount of redox active oxide at the surface, but electrochemical oxidation is found to be more successful in increasing the capacitance.

Unexpected Cation Dynamics in the Low-Temperature Phase of Methylammonium Lead Iodide: The Need for Improved Models.

Abstract: High-resolution inelastic neutron scattering and extensive first-principles calculations have been used to explore the low-temperature phase of the hybrid solar-cell material methylammonium lead iodide up to the well-known phase transition to the tetragonal phase at ca. 160 K. Contrary to original expectation, we find that the Pnma structure for this phase can only provide a qualitative description of the geometry and underlying motions of the organic cation. A substantial lowering of the local symmetry inside the perovskite cage leads to an improved atomistic model that can account for all available spectroscopic and thermodynamic data, both at low temperatures and in the vicinity of the aforementioned phase transition. Further and detailed analysis of the first-principles calculations reveals that large-amplitude distortions of the inorganic framework are driven by both zero-point-energy fluctuations and thermally activated cation motions. These effects are significant down to liquid-helium temperatures...

Six- and eight-coordinate thio- and seleno-ether complexes of NbF5 and some comparisons with NbCl5 and NbBr5 adducts

Abstract: The reaction of RS(CH2)2SR (R = Me, Et or iPr) with NbF5 produces [NbF4{RS(CH2)2SR}2][NbF6] which contain distorted eight-coordinate (dodecahedral) cations and octahedral anions, whereas RSe(CH2)2SeR (R = Me or Bun) form six-coordinate [(NbF5)2(μ-RSe(CH2)2SeR)]. Et2S and Me2Se (L) also form six-coordinate [NbF5(L)], but Me2S forms both [NbF5(Me2S)] and an eight-coordinate cation in [NbF4(Me2S)4][NbF6]. MeS(CH2)2SMe forms eight-coordinate cations in [NbX4{MeS(CH2)2SMe}2][NbX6] (X = Cl or Br), but other complexes of the heavier halides including [NbX5(L)] and [(NbX5)2(μ-L–L)] (L–L = RSe(CH2)2SeR; o-C6H4(CH2SMe)2 and o-C6H4(CH2SeMe)2) contain six-coordinate niobium. The very unstable [NbCl5(Me2Te)] was characterised spectroscopically, but all other attempts to form telluroether complexes resulted in decomposition, and NbI5 was reduced even by thioethers. The complexes have been characterised by multinuclear NMR (1H, 19F, 93Nb, 77Se or 125Te), IR and UV/visible spectroscopy, and X-ray crystal structures are reported for [NbF4{RS(CH2)2SR}2][NbF6] (R = Me, iPr), [NbF4(Me2S)4][NbF6], [NbCl5(Me2Se)], [NbBr5(Me2S)], [(NbCl5)2{o-C6H4(CH2SMe)2}] and [(NbCl5)2{MeSe(CH2)2SeMe}]. All the complexes are very moisture sensitive and the fluoride complexes decompose slowly with fluorination of the neutral ligand.

Tin(iv) chalcogenoether complexes as single source precursors for the chemical vapour deposition of SnE2 and SnE (E = S, Se) thin films.

Abstract: The molecular Sn(iv) complexes, [SnCl4{nBuS(CH2)3SnBu}] (2), [SnCl4(nBu2S)2] (3) and [SnCl4(nBu2Se)2] (4) have been prepared in good yield from reaction of SnCl4 with the appropriate chalcogenoether ligand in anhydrous hexane and, together with the known [SnCl4{nBuSe(CH2)3SenBu}] (1), employed as single source precursors for the low pressure chemical vapour deposition of the corresponding tin dichalcogenide thin films. At elevated temperatures the bidentate ligand precursors, (1) and (2), also form the tin monochalcogenides, SnSe and SnS, respectively. In contrast, (3) gave a mixture of phases, SnS2, Sn2S3 and SnS and (4) gave SnSe2 only. The morphologies, elemental compositions and crystal structures of the resulting films have been determined by scanning electron microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction and Raman spectroscopy. Van der Pauw measurements on the SnS2, SnS and SnSe2 films confirm their resistivities to be 2.9(9), 266(3) and 4.4(3) Ω cm, respectively.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

High-Efficiency Perovskite Solar Cells.

Abstract: With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.

Perovskites for Next-Generation Optical Sources.

Abstract: Next-generation displays and lighting technologies require efficient optical sources that combine brightness, color purity, stability, substrate flexibility. Metal halide perovskites have potential use in a wide range of applications, for they possess excellent charge transport, bandgap tunability and, in the most promising recent optical source materials, intense and efficient luminescence. This review links metal halide perovskites' performance as efficient light emitters with their underlying materials electronic and photophysical attributes.

Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors

Abstract: High-quality ultrathin single-crystalline SnSe2 flakes are synthesized under atmospheric-pressure chemical vapor deposition for the first time. A high-performance photodetector based on the individual SnSe2 flake demonstrates a high photoresponsivity of 1.1 × 10(3) A W(-1), a high EQE of 2.61 × 10(5)%, and superb detectivity of 1.01 × 10(10) Jones, combined with fast rise and decay times of 14.5 and 8.1 ms, respectively.

Achieving Persistent Room Temperature Phosphorescence and Remarkable Mechanochromism from Pure Organic Luminogens

Abstract: Persistent room temperature phosphorescence (RTP) from pure organic luminogens can be rationally realized based on the crystallization-induced phosphorescence phenomenon and severe crystallization. A perfect crystal with dense molecular packing and effective inter-molecular interactions isolates the triplet excitons from quenching sites and significantly blocks the high-energy vibrational dissipation, thus yielding long-lasting RTP.