Showing papers on "Single crystal published in 2015"
TL;DR: A detailed comparison of single-crystal diffraction data collected with Ag Kα and Mo’™Kα microsources (IµS) indicates that the Ag”Kα data are better when absorption is significant.
Abstract: The quality of diffraction data obtained using silver and molybdenum microsources has been compared for six model compounds with a wide range of absorption factors. The experiments were performed on two 30 W air-cooled Incoatec IµS microfocus sources with multilayer optics mounted on a Bruker D8 goniometer with a SMART APEX II CCD detector. All data were analysed, processed and refined using standard Bruker software. The results show that Ag Kα radiation can be beneficial when heavy elements are involved. A numerical absorption correction based on the positions and indices of the crystal faces is shown to be of limited use for the highly focused microsource beams, presumably because the assumption that the crystal is completely bathed in a (top-hat profile) beam of uniform intensity is no longer valid. Fortunately the empirical corrections implemented in SADABS, although originally intended as a correction for absorption, also correct rather well for the variations in the effective volume of the crystal irradiated. In three of the cases studied (two Ag and one Mo) the final SHELXL R1 against all data after application of empirical corrections implemented in SADABS was below 1%. Since such corrections are designed to optimize the agreement of the intensities of equivalent reflections with different paths through the crystal but the same Bragg 2θ angles, a further correction is required for the 2θ dependence of the absorption. For this, SADABS uses the transmission factor of a spherical crystal with a user-defined value of μr (where μ is the linear absorption coefficient and r is the effective radius of the crystal); the best results are obtained when r is biased towards the smallest crystal dimension. The results presented here suggest that the IUCr publication requirement that a numerical absorption correction must be applied for strongly absorbing crystals is in need of revision.
2,639 citations
TL;DR: The major achievements and research and development trends from the last decade in the field of single crystal scintillator materials are described in this paper, where two material families are included, namely, those of halide and oxide compounds.
Abstract: In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin- and parity-allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high-energy physics and the high-tech industry, in which X(γ)-rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field.
493 citations
TL;DR: In this article, a single crystal of tetragonal CH3NH3PbI3 with dimensions of 10 mm × 10mm × 8 mm was grown by a temperature-lowering method in HI solution.
Abstract: Organic–inorganic hybrid perovskite materials have been receiving considerable attention due to their promising applications in many optoelectronic fields. However, some of the fundamental properties of perovskite materials are still disputed, because most of them are derived from a thin-film state. To comprehend the intrinsic characteristics in a single crystal, herein we report, for the first time, the bulk crystal growth of CH3NH3PbI3. Single crystals of tetragonal CH3NH3PbI3 with dimensions of 10 mm × 10 mm × 8 mm were grown by a temperature-lowering method in HI solution. Studies in to the refinement and orientations of the CH3NH3PbI3 single crystal structure were conducted based on a high quality crystal. The absorption edge of a CH3NH3PbI3 single crystal was located at about 836 nm, indicating that the band gap of CH3NH3PbI3 is approximately 1.48 eV, which is close to the theoretical results and smaller than those derived from polycrystalline and thin-films. CH3NH3PbI3 crystal exhibits a relatively wide absorption (from 250 nm to 800 nm) and a relatively good thermal stability.
456 citations
TL;DR: This work measures surface recombination dynamics in CH3NH3PbBr3 perovskite single crystals using broadband transient reflectance spectroscopy and suggests that the planar grain size for the perovkite thin films should be larger than ∼30 μm to avoid the influence ofsurface recombination on the effective carrier lifetime.
Abstract: Surface recombination velocity can have a major impact on solar cell performance. Here, Yang et al. measure surface recombination dynamics in perovskite single crystals using broadband transient reflectance spectroscopy. Grain size is crucial to avoid the effects of surface recombination on carrier lifetime.
400 citations
TL;DR: In this paper, the crystal structures of the ternary iodides are redetermined and a corrected structural model for Rb3Bi2I9, as established by single crystal X-ray diffraction and solid state 87Rb NMR spectroscopy and supported by density functional theory (DFT) calculations is presented.
Abstract: Ternary bismuth halides form an interesting functional materials class in the context of the closely related Pb halide perovskite photovoltaics, especially given the significantly reduced toxicity of Bi when compared with Pb. The compounds A3Bi2I9 (A = K, Rb, Cs) examined here crystallize in two different structure types: the layered defect-perovskite K3Bi2I9 type, and the Cs3Cr2Cl9 type. The latter structure type features isolated Bi2I93– anions. Here, the crystal structures of the ternary iodides are redetermined and a corrected structural model for Rb3Bi2I9, as established by single crystal X-ray diffraction and solid state 87Rb NMR spectroscopy and supported by density functional theory (DFT) calculations is presented. A variety of facile preparation techniques for single crystals, bulk materials, as well as solution-processed thin films are described. The optical properties and electronic structures are investigated experimentally by optical absorption and ultraviolet photoemission spectroscopy and c...
379 citations
TL;DR: It is suggested that single-crystal perovskite nanostructures provide improved photophysical properties that are important for fundamental studies and future applications in nanoscale optoelectronic and photonic devices.
Abstract: Understanding crystal growth and improving material quality is important for improving semiconductors for electronic, optoelectronic, and photovoltaic applications. Amidst the surging interest in solar cells based on hybrid organic–inorganic lead halide perovskites and the exciting progress in device performance, improved understanding and better control of the crystal growth of these perovskites could further boost their optoelectronic and photovoltaic performance. Here, we report new insights on the crystal growth of the perovskite materials, especially crystalline nanostructures. Specifically, single crystal nanowires, nanorods, and nanoplates of methylammonium lead halide perovskites (CH3NH3PbI3 and CH3NH3PbBr3) are successfully grown via a dissolution-recrystallization pathway in a solution synthesis from lead iodide (or lead acetate) films coated on substrates. These single crystal nanostructures display strong room-temperature photoluminescence and long carrier lifetime. We also report that a solid...
360 citations
TL;DR: In this paper, the thermal conductivities of β-Ga2O3 single crystals along four different crystal directions were measured in the temperature range of 80 −495 K using the time domain thermoreflectance method.
Abstract: The thermal conductivities of β-Ga2O3 single crystals along four different crystal directions were measured in the temperature range of 80–495 K using the time domain thermoreflectance method. A large anisotropy was found. At room temperature, the [010] direction has the highest thermal conductivity of 27.0 ± 2.0 W/mK, while that along the [100] direction has the lowest value of 10.9 ± 1.0 W/mK. At high temperatures, the thermal conductivity follows a ∼1/T relationship characteristic of Umklapp phonon scattering, indicating phonon-dominated heat transport in the β-Ga2O3 crystal. The measured experimental thermal conductivity is supported by first-principles calculations, which suggest that the anisotropy in thermal conductivity is due to the differences of the speed of sound along different crystal directions.
350 citations
TL;DR: This tutorial review focuses on introducing the more recent advances in the CVD growth of MX2 monolayers via the sulphurisation/decomposition of pre-deposited metal-based precursors, or the one-step reaction and deposition of gaseous metal and chalcogen feedstocks.
Abstract: As structural analogues of graphene but with a sizeable band gap, monolayers of group-VIB transition metal dichalcogenides (MX2, M = Mo, W; X = S, Se, Te, etc.) have emerged as the ideal two dimensional prototype for exploring fundamental issues in physics such as valley polarization, and for engineering a wide range of nanoelectronic, optoelectronic and photocatalytic applications. Recently, chemical vapour deposition (CVD) was introduced as a more efficient preparation method than traditional chemical or physical exfoliation options, and has allowed for the successful synthesis of large-area MX2 monolayers possessing a large domain size, high thickness uniformity and continuity, and satisfactory crystal quality. This tutorial review therefore focuses on introducing the more recent advances in the CVD growth of MX2 (MoS2, WS2, MoS2(1−x)Se2xetc.) monolayers via the sulphurisation/decomposition of pre-deposited metal-based precursors, or the one-step reaction and deposition of gaseous metal and chalcogen feedstocks. Differences in growth behaviour caused by commonly used amorphous SiO2/Si, and newly adopted insulating single crystal substrates such as sapphire, mica and SrTiO3, are also comparatively presented. Also discussed are the essential parameters that influence the growth of MX2, such as the temperature, the source–substrate distance and the composition of the carrier gas (Ar/H2). Finally, an assessment is provided for viable future pathways for fine-tuning of the domain size and orientation, thickness uniformity, and the bandgap of MX2 and its alloys.
322 citations
TL;DR: The successful synthesis of large single-crystal h-BN grains on rational designed Cu-Ni alloy foils is reported, found that the nucleation density can be greatly reduced to 60 per mm(2) by optimizing Ni ratio in substrates.
Abstract: High nucleation density has thus far limited the quality and grain size of CVD-grown hexagonal boron nitride. Here, by optimizing the Ni ratio in Cu–Ni substrates, the authors successfully reduce nucleation density and report single-crystal hexagonal boron nitride grains up to 7500 μm2.
321 citations
TL;DR: Spatially resolved surface photovoltage spectroscopy was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO4 photocatalyst.
Abstract: Spatially resolved surface photovoltage spectroscopy (SRSPS) was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO4 photocatalyst. Through the controlled synthesis of a single crystal with preferentially exposed {010} facets, highly anisotropic photogenerated hole transfer to the {011} facet of single BiVO4 crystals was observed. The surface photovoltage signal intensity on the {011} facet was 70 times stronger than that on the {010} facets. The influence of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal is revealed.
281 citations
TL;DR: It is demonstrated that MAPbI3 photodetector based on single crystal can perform much better than that on polycrystalline-film counterpart, and may pave the way for exploiting high-performance perovskitesPhotodetectors based onsingle crystal.
Abstract: Recently, the discovery of organometallic halide perovskites provides promising routes for fabricating optoelectronic devices with low cost and high performance. Previous experimental studies of MAPbI3 optoelectronic devices, such as photodetectors and solar cells, are normally based on polycrystalline films. In this work, a high-performance planar-type photodetector fabricated on the (100) facet of a MAPbI3 single crystal is proposed. We demonstrate that MAPbI3 photodetector based on single crystal can perform much better than that on polycrystalline-film counterpart. The low trap density of MAPbI3 single crystal accounts for the higher carrier mobility and longer carrier diffusion length, resulted in a significant performance increasement of MAPbI3 photodetector. Compared with similar planar-type photodetectors based on MAPbI3 polycrystalline film, our MAPbI3 single crystal photodetector showed excellent performance with good stability and durability, broader response spectrum to near-infrared region, about 10(2) times higher responsivity and EQE, and approximately 10(3) times faster response speed. These results may pave the way for exploiting high-performance perovskites photodetectors based on single crystal.
TL;DR: In this article, the 1H and 13C NMR spectra in methylammonium lead halide perovskites, CH3NH3PbX3 (X = I, Br and Cl) were used to refine some single crystal X-ray and neutron diffraction data to probe their unusual structures.
Abstract: The 1H and 13C NMR spectra in methylammonium lead halide perovskites, CH3NH3PbX3 (X = I, Br and Cl) show that the CH3NH3+ units undergo dynamic reorientation, as the organic component tumbles in the perovskite cage. In addition, the differences in the anomalously long relaxation times of the protons associated with the CH3 and not the NH3 groups indicate that only the amine end of the CH3NH3+ group is interacting with the inorganic network. Using this information, we have refined some single crystal X-ray and neutron diffraction data to probe their unusual structures in more detail. Furthermore, impedance spectroscopy has been used to monitor the high-temperature phase transition of CH3NH3PbI3, which confirms a significant increase in conductivity, when it is in its high temperature and higher symmetry structural regime. The optical band-gaps of each halide perovskite were determined using UV-visible spectroscopy and are consistent with previous reports.
TL;DR: In this paper, the authors used pulses of multi-THz frequency light in the ultra-broadband 1-30 THz (4-125 meV) range to observe the ac conductivity in large single crystal CH3NH3PbI3.
Abstract: Hybrid metal–organic perovskite solar cells have astounded the solar cell community with their rapid rise in efficiency while maintaining low-cost fabrication. The intrinsic material photophysics related to the generation of free charges, their dynamics and efficiency, however, remains to be understood. As fabrication techniques improve, larger crystal grain sizes have been shown to be a critical factor for improving both the optical and transport properties of the hybrid metal halide perovskites. In this work, we use pulses of multi-THz frequency light in the ultra-broadband 1–30 THz (4–125 meV) range to observe the ac conductivity in large single crystal CH3NH3PbI3. Our spectra reveal the ultrafast dynamics and efficiencies of free charge creation and extremely high charge carrier mobility as high as 500–800 cm2 V−1 s−1. While quasi-equilibrium analysis of efficiencies through the Saha equation suggests a binding energy on the order of 49 meV, an observed reflectance feature appearing at high pump fluence occurs at 12 meV and is consistent with an orbital transition of the exciton, indicating a much lower Rydberg energy of 17 meV at room temperature. The signature of the exciton is found to vanish on a 1 ps time scale commensurate with the appearance of mobile carriers, consistent with thermal dissociation of the exciton to the continuum in the room temperature tetragonal phase.
TL;DR: In this article, the authors present an overview of the historic evolution in understanding of carrier diffusion length in CH3NH3PbI3, the initial investigations of the synthesis of single crystalline hybrid perovskites, and the characterization of their optoelectronic properties.
Abstract: Hybrid perovskite single crystals have been recently revealed to have superior optoelectronic properties to perovskite polycrystalline thin films, especially the extraordinarily long carrier diffusion length due to the eliminated grain boundaries. One question that naturally arises is whether the single crystal hybrid perovskites can be a next wave of photoactive materials for even higher-efficiency devices. This Perspective presents an overview of the historic evolution in understanding of carrier diffusion length in CH3NH3PbI3, the initial investigations of the synthesis of single crystalline hybrid perovskites, and the characterization of their optoelectronic properties. Our analysis indicates that single crystalline perovskite materials have potential to further boost photovoltaic device power conversion efficiency to 25%. The potential opportunities for the fundamental study of the perovskite intrinsic properties, particularly the carrier mobility and carrier recombination lifetime, and other fields ...
TL;DR: Structural inhomogeneity on a micrometer-scale across a CH3NH3PbI3 single crystal is responsible for a local modulation of the optical band gap, which is also highly sensitive to humidity.
Abstract: Here we identify structural inhomogeneity on a micrometer scale across the surface of a CH3NH3PbI3 perovskite single crystal. At the crystal edge a local distortion of the crystal lattice is responsible for a widening of the optical bandgap and faster photo-carrier recombination. These effects are inherently present at the edge of the crystal, and further enhanced upon water intercalation, as a preliminary step in the hydration of the perovskite material.
TL;DR: In this paper, a numerical study of the distribution of the local stress state associated with deformation twinning in Mg is presented, both inside the twinned domain and in its immediate neighborhood, due to the accommodation of the twinning transformation shear.
TL;DR: This protocol is intended to provide chemists and physicists with a tool for predicting the charge carrier mobilities of π-stacked systems such as organic semiconductors and the DNA double helix.
Abstract: Carrier mobility is the most important parameter for assessing charge carrier transfer. This protocol describes a tool for predicting the charge carrier mobilities of π-stacked systems such as organic semiconductors and the DNA double helix. This protocol is intended to provide chemists and physicists with a tool for predicting the charge carrier mobilities of π-stacked systems such as organic semiconductors and the DNA double helix. An experimentally determined crystal structure is required as a starting point. The simulation involves the following operations: (i) searching the crystal structure; (ii) selecting molecular monomers and dimers from the crystal structure; (iii) using density function theory (DFT) calculations to determine electronic coupling for dimers; (iv) using DFT calculations to determine self-reorganization energy of monomers; and (v) using a numerical calculation to determine the charge carrier mobility. For a single crystal structure consisting of medium-sized molecules, this protocol can be completed in ∼4 h. We have selected two case studies (a rubrene crystal and a DNA segment) as examples of how this procedure can be used.
TL;DR: In this article, a review of the state of the art on single crystal mullite is presented, focusing on the crystal structure of mullite and its properties, such as elasticity, compressibility, strength, toughness, creep and thermal properties.
Abstract: Mullite is certainly one of the most important oxide materials for both conventional and advanced ceramics. Mullite belongs to the compositional series of orthorhombic aluminosilicates with the general composition Al2(Al2+2xSi2-2x)O10-x. Main members are sillimanite (x = 0), stoichiometric 3/2-mullite (x = 0.25), 2/1-mullite (x = 0.40), and the SiO2-free phase ι-alumina (x = 1, crystal structure not known). This study gives an overview on the present state of research regarding single crystal mullite. Following a short introduction, the second part of the review focuses on the crystal structure of mullite. In particular, the characteristic mullite-type structural backbone of parallel chains consisting of edge-sharing MO6 octahedra and their specific cross-linkage by TO4 tetrahedra is explained in detail, the role of cation disorder and structural oxygen vacancies is addressed, and the possibility of cation substitution on different sites is discussed. The third part of the study deals with physical properties being relevant for technical applications of mullite and includes mechanical properties (e.g., elasticity, compressibility, strength, toughness, creep), thermal properties (e.g., thermal expansion, heat capacity, atomic diffusion, thermal conductivity), electrical conductivity, and optical properties. Special emphasis is put on structure–property relationships which allow for interpretation of corresponding experimental data and offer in turn the possibility to tailor new mullite materials with improved properties. Finally, the reported anomalies and discontinuities in the evolution of certain physical properties with temperature are summarized and critically discussed.
TL;DR: It is found that the magnetization of single-crystal SmFeO3 can be switched by temperature, and tuning the magnitude of applied magnetic field allows us to realize such spin switching even at room temperature.
Abstract: The prospect of controlling the magnetization (M) of a material is of great importance from the viewpoints of fundamental physics and future applications of emerging spintronics. A class of rare-earth orthoferrites RFeO3 (R is rare-earth element) materials exhibit striking physical properties of spin switching and magnetization reversal induced by temperature and/or applied magnetic field. Furthermore, due to the novel magnetic, magneto-optic and multiferroic properties etc., RFeO3 materials are attracting more and more interests in recent years. We have prepared and investigated a prototype of RFeO3 materials, namely SmFeO3 single-crystal. And we report magnetic measurements upon both field cooling (FC) and zero-field cooling (ZFC) of the sample, as a function of temperature and applied magnetic field. The central findings of this study include that the magnetization of single-crystal SmFeO3 can be switched by temperature and tuning the magnitude of applied magnetic field allows us to realize such spin switching even at room temperature.
TL;DR: A theoretical model for describing effective thermal conductivity of nanocrystalline materials has been proposed, and it has been demonstrated that with increasing grain size, both GBs and size effects become weaker, while size effect effects become stronger on thermal Conductivity than GBs effects.
Abstract: A theoretical model for describing effective thermal conductivity (ETC) of nanocrystalline materials has been proposed, so that the ETC can be easily obtained from its grain size, single crystal thermal conductivity, single crystal phonon mean free path (PMFP), and the Kaptiza thermal resistance In addition, the relative importance between grain boundaries (GBs) and size effects on the ETC of nanocrystalline diamond at 300 K has been studied It has been demonstrated that with increasing grain size, both GBs and size effects become weaker, while size effects become stronger on thermal conductivity than GBs effects
TL;DR: In this paper, a single particle X-ray diffraction analysis of the particle revealed that Ba2LiSi7AlN12:Eu2+ crystallizes in the Pnnm space group (No. 58) with a = 14.0941 A, b = 4.8924 A, c = 8.0645 A, and Z = 2.
Abstract: The narrow-band green-emitting phosphor Ba2LiSi7AlN12:Eu2+ was discovered by analyzing a single particle in a powder mixture, which we call the single particle diagnosis approach. Single crystal X-ray diffraction analysis of the particle revealed that Ba2LiSi7AlN12:Eu2+ crystallizes in the Pnnm space group (No. 58) with a = 14.0941 A, b = 4.8924 A, c = 8.0645 A, and Z = 2. The crystal structure is composed of a corner-sharing (Si,Al)N4 corrugated layer and edge-sharing (Si,Al)N4 and LiN4 tetrahedra. Ba(Eu) occupies the one-dimensional channel in a zigzag manner. The luminescence properties were also measured using a single crystalline particle. Ba2LiSi7AlN12:Eu2+ shows a green luminescence peak at approximately 515 nm with a narrow full-width at half-maximum of 61 nm. It shows high quantum efficiency of 79% with 405 nm excitation and a small decrease of luminescence intensity even at 300 °C.
TL;DR: A low-temperature scanning tunneling microscopy study of single crystal methylammonium lead bromide CH3NH3PbBr3 reveals the real-space atomic structure and explains modified arrangements of atoms and molecules on the surface by surface reconstruction and a substantial interplay of the orientation of the polar organic cations.
Abstract: Organic-inorganic perovskite is a promising class of materials for photovoltaic applications and light emitting diodes. However, so far commercialization is still impeded by several drawbacks. Atomic-scale effects have been suggested to be possible causes, but an unequivocal experimental view at the atomic level is missing. Here, we present a low-temperature scanning tunneling microscopy study of single crystal methylammonium lead bromide CH3NH3PbBr3. Topographic images of the in situ cleaved perovskite surface reveal the real-space atomic structure. Compared to the bulk we observe modified arrangements of atoms and molecules on the surface. With the support of density functional theory we explain these by surface reconstruction and a substantial interplay of the orientation of the polar organic cations (CH3NH3)(+) with the position of the hosting anions. This leads to structurally and electronically distinct domains with ferroelectric and antiferroelectric character. We further demonstrate local probing of defects, which may also impact device performance.
TL;DR: In this paper, the authors investigated the shearing mechanisms during single-crystal tensile creep of L12-containing Co- and CoNi-base alloys, and found that the antiphase boundaries formed by shearing of dislocations on octahedral planes.
TL;DR: It is shown that the co-existence of In( 3+) and Cr(3+) induces a rapid crystal growth of large single crystals of heterometallic In-Cr-MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5-imidazole-dicarboxylate) cubane-like structure, which exhibit an exceptionally high proton conductivity.
Abstract: Metal–organic polyhedra (MOPs) or frameworks (MOFs) based on Cr3+ are notoriously difficult to synthesize, especially as crystals large enough to be suitable for characterization of the structure or properties. It is now shown that the co-existence of In3+ and Cr3+ induces a rapid crystal growth of large single crystals of heterometallic In-Cr-MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5-imidazole-dicarboxylate) cubane-like structure. With a high concentration of protons from 12 carboxyl groups decorating every edge of the cube and an extensive H-bonded network between cubes and surrounding H2O molecules, the newly synthesized In-Cr-MOPs exhibit an exceptionally high proton conductivity (up to 5.8×10−2 S cm−1 at 22.5 °C and 98 % relative humidity, single crystal).
TL;DR: The large π-conjugated N-heteroquinone 6,10,17,21-tetra-((triisopropylsilyl)ethynyl)-5,7,9,11,16,18,20,22-octaazanonacene-8,19-dione (OANQ) has been synthesized and characterized and no obvious degradation was observed even after one month.
Abstract: Increasing the length of N-heteroacenes or their analogues is highly desirable because such materials could have great potential applications in organic electronics. In this report, the large p-conjugated N-heteroquinone 6,10,17,21- tetra-((triisopropylsilyl)ethynyl)-5,7,9,11,16,18,20,22-octaaza- nonacene-8,19-dione (OANQ) has been synthesized and characterized. The as-prepared OANQ shows high stability under ambient conditions and has a particularly low LUMO level, which leads to it being a promising candidate for air- stable n-type field-effect transistors (FETs). In fact, FET devices based on OANQ single crystals have been fabricated and an electron mobility of up to 0.2 cm 2 V 1 s 1 under ambient conditions is reported. More importantly, no obvious degra- dation was observed even after one month. Theoretical calculations based on the single crystal are consistent with the measured mobility.
TL;DR: The first time the growth of n-channel single-crystal field-effect transistors and organic thin-film transistors by sublimation of 2,6-dichloro-naphthalene diimide in air is demonstrated and a new polymorph with two-dimensional brick-wall packing mode (β-phase) is obtained.
Abstract: Physical properties of active materials built up from small molecules are dictated by their molecular packing in the solid state. Here we demonstrate for the first time the growth of n-channel single-crystal field-effect transistors and organic thin-film transistors by sublimation of 2,6-dichloro-naphthalene diimide in air. Under these conditions, a new polymorph with two-dimensional brick-wall packing mode (β-phase) is obtained that is distinguished from the previously reported herringbone packing motif obtained from solution (α-phase). We are able to fabricate single-crystal field-effect transistors with electron mobilities in air of up to 8.6 cm2 V−1 s−1 (α-phase) and up to 3.5 cm2 V−1 s−1 (β-phase) on n-octadecyltriethoxysilane-modified substrates. On silicon dioxide, thin-film devices based on β-phase can be manufactured in air giving rise to electron mobilities of 0.37 cm2 V−1 s−1. The simple crystal and thin-film growth procedures by sublimation under ambient conditions avoid elaborate substrate modifications and costly vacuum equipment-based fabrication steps. Charge transport in organic semiconductors is highly sensitive to crystalline polymorphs. Here, He et al. manufacture the first n-channel single-crystal transistor via sublimation at ambient conditions and identify a new polymorphous phase that does not exist in its solution-processed counterpart.
TL;DR: Interestingly, the Cl/Br ratio in the (CH3NH3)Pb(Br1-xClx)3 single crystals is larger than that of the precursor solution, suggesting an unusual crystal growth mechanism.
TL;DR: In this paper, a new layered Co-Ca phosphonate (CoIIICaII(notpH2)(H2O)2]ClO4·nH 2O was reported, which undergoes a reversible relative humidity (RH) dependent SC-SC structural transformation between CoCa·2H 2 O and ClO4H2 O at room temperature, leading to a drastic decrease in proton conductivity.
Abstract: A combination of humidity-dependent single crystal to single crystal (SC–SC) structural transformation and single crystal proton conductivity measurements is essential to elucidate the underlying proton transport mechanism in metal–organic framework materials. Herein, we report a new layered Co–Ca phosphonate [CoIIICaII(notpH2)(H2O)2]ClO4·nH2O [abbreviated as CoCa·nH2O, where notpH6 = 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid), C9H18N3(PO3H2)3]. CoCa·nH2O undergoes a reversible relative humidity (RH) dependent SC–SC structural transformation between CoCa·2H2O and CoCa·4H2O at room temperature. Accordingly the continuous hydrogen bond network observed in CoCa·4H2O (95% RH) is interrupted in CoCa·2H2O (40% RH), leading to a drastic decrease in proton conductivity by ∼5 orders of magnitude. The process is reversible; hence, the proton conductivity is tunable simply through humidity control. The AC impedance measurements using single crystals of CoCa·nH2O reveal that the [010] directio...
TL;DR: In this article, chemical fluctuations in the vicinity of superlattice intrinsic stacking faults (SISFs) have been observed via high resolution energy dispersive X-ray spectroscopy (EDS) mapping in new single crystal Co- and CoNi-base superalloys containing γ ′ -(L1 2 ) precipitates.
TL;DR: In this paper, the superconducting transition temperature (T-c) of 42 K was determined by magnetic susceptibility and electric resistivity measurements, and the zero-temperature upper critical magnetic fields were evaluated as 79 and 313 T for the field along the c axis and the ab plane, respectively.
Abstract: A large and high-quality single crystal (Li0.84Fe0.16)OHFe0.98Se, the optimal superconductor of a reported (Li1-xFex)OHFe1-ySe system, has been successfully synthesized via a hydrothermal ion-exchange technique. The superconducting transition temperature (T-c) of 42 K is determined by magnetic susceptibility and electric resistivity measurements, and the zero-temperature upper critical magnetic fields are evaluated as 79 and 313 T for the field along the c axis and the ab plane, respectively. The ratio of out-of-plane to in-plane electric resistivity rho(c)/rho(ab) is found to increase with decreasing temperature and to reach a high value of 2500 at 50 K, with an evident kink occurring at a characteristic temperature T* = 120 K. The negative in-plane Hall coefficient indicates that electron carriers dominate in the charge transport, and the hole contribution is significantly reduced as the temperature is lowered to approach T *. From T * down to T-c we observe the linear temperature dependencies of the in-plane electric resistivity and the magnetic susceptibility for the FeSe layers. Our findings thus reveal that the normal state of (Li0.84Fe0.16)OHFe0.98Se becomes highly two dimensional and anomalous prior to the superconducting transition, providing an insight into the mechanism of high-T-c superconductivity.