Wang et al. reported changes in the muonium (Mu) addition rate to different sites in 6,13-bis(tri(isopropyl)silylethynyl)-pentacene (TIPS-Pn) in CH 2 Cl 2 when it is photo-excited compared with the ground electronic state [1].In order to make this claim one must demonstrate that 1) there is a change in the overall reaction rate of Mu with TIPS-Pn, and 2) there is a change in the relative yield of each muoniated radical formed by Mu addition to TIPS-Pn.Our independent analysis of the transverse-field muon spin rotation (TF-µSR) and avoided level crossing muon spin resonance (ALC-µSR) spectra in [1] indicate that there is no statistically significant effect of photo-excitation.Point (1): Wang et al. assume the fast precession signal in the TF-µSR spectra is due to Mu.Chemical reaction of Mu leads to damping of the precession signal at a rate λ that is given by the second-order rate constant k times the concentration of the reactant (plus a contribution including effects other than chemical reaction) [2,3].It is λ that should change if the rate of one or more of the competing pathways for Mu addition to TIPS-Pn is altered by photoexcitation.In order to establish and quantify any effect of illumination with statistical significance the spectra must be fitted in the time domain to an appropriate model (Lorentzian relaxation of the precession signal due to non-viscous solution) and the errors on the fit parameters must be reported.Fourier-transformed TFµSR spectra as presented in [1] cannot provide this essential information.We have determined the amplitude of the spin precession signal A Mu and the relaxation rate λ as a function of applied magnetic field (Fig. 1), details are provided in the Supplementary Information.There is no significant difference in A Mu or λ between light on and off.Moreover, the assignment of this signal to Mu is questionable.The observed λ of ∼ 0.6 µs -1 would imply a very small rate constant of k = 6 × 10 7 M -1 s -1 , which is about two orders of magnitude smaller than for Mu addition to naphthalene [2].Furthermore, for λ 10 µs -1 one should not be able to observe ALC resonances due to muoniated radicals (Supplementary Information).Point ( 2): The muon-methylene proton spin flip-flop (∆ 0 ) ALC resonances due to the three types of Mu adduct are shown in Fig. 1e and Fig. 1f.There is no significant difference in the amplitude of the resonances, which indicates there is no light-induced change in the Mu addition rate.Only the resonance field of Site 2 might be affected upon illumination, but this needs further investigation.It is this shift that has the biggest effect on the shape of the overlapping resonances due to Sites 2 and 1.The apparent difference in asymmetry measured at a fixed off-resonant magnetic field (710 mT) (Fig. 2c in [1]) therefore is not related to a change of the radical yield which must be deduced from the fitted amplitudes.It is our opinion that the appropriate null experiments were not performed and that the system TIPS-Pn/DCM is not sufficiently characterized.At least, an experiment should have been performed on pure CH 2 Cl 2 in order to quantify any spurious effects due to irradiation and the formation rates of the different radicals should have been properly determined beforehand.There is no evidence that the data presented in [1] reflect a change in the Mu addition rate to TIPS-Pn, and the assignment of the fast-precession signal to solvated Mu and any interpretation based on that working hypothesis is questionable.

In this study, a direct sulfidation reaction of ammonium perrhenate (NH4ReO4) leading to a synthesis of rhenium disulfide (ReS2) is demonstrated. These findings reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS2. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The results indicated the formation of a lower symmetry (1T') ReS2 with a low degree of layer stacking.

The use of implanted muons to probe the spin dynamics and electronic excitations in organic materials is reviewed. At first, a brief introduction to the historical context and background of the muon technique is given, followed by an outline of some of the underlying theoretical models needed to quantitatively interpret data taken on organic molecules. Caution is advised when using certain theoretical models for the interpretation of low-field spin relaxation data. The next section deals with spin dynamics in soft materials, and starts with discussing many of the key results in thin films, followed by a review of bulk measurements in three different materials classes-polymers, biologically active molecules, and small molecules. Finally, we present a detailed discussion of the density functional theory methodology when applied to mu SR, and present the common issues encountered when trying to perform these calculations to support muon experiments. In particular, we discuss a method for benchmarking to manage the approximations inherent to the technique and common sources of errors that can sometimes fortuitously cancel.

在电子产业中,能够进行低压操作以及能够在非常薄的薄层上进行器件设计的材料备受关注.并且,这些材料需要使用方法简单、快速、可靠.作者提出一种简单且快速可靠的沉积高k二氧化锆介电层的方法.整个过程从原来常规过程的140分钟缩短到10分钟.这种改进的方法在操作流程方面有显著的提升.这种溶胶凝胶法制备的样品介电层厚度远小于与之前报道的样品,其厚度约为原方法制备样品的25％.在优化操作过程与降低介电层厚度的同时,二氧化锆的介电性质并没有被影响.作者进一步研究了样品的介电特性,在90K到300K之间介电性质的变化小于10％.

Photochemical reactions are essential to a large number of important industrial and biological processes. A method for monitoring photochemical reaction kinetics and the dynamics of molecular excitations with spatial resolution within the active molecule would allow a rigorous exploration of the pathway and mechanism of photophysical and photochemical processes. Here we demonstrate that laser-excited muon pump–probe spin spectroscopy (photo-μSR) can temporally and spatially map these processes with a spatial resolution at the single-carbon level in a molecule with a pentacene backbone. The observed time-dependent light-induced changes of an avoided level crossing resonance demonstrate that the photochemical reactivity of a specific carbon atom is modified as a result of the presence of the excited state wavefunction. This demonstrates the sensitivity and potential of this technique in probing molecular excitations and photochemistry. Laser-excited muon pump–probe spin spectroscopy and analysis of avoided level crossing resonances are used to probe the time evolution of the chemical reactivity of individual carbon atoms in TIPS-pentacene after light excitation.

We describe the device and transport characteristics of amorphous zinc tin oxide thin‐film (ZTO) transistors. In samples with a sufficiently high mobility and at a high gate voltage, a crossover occurs from transport governed by thermal excitation of trapped charges to one where the charge carriers reside for a sufficiently long time in extended states. Very few semiconductors exhibit this range of behavior in the same device under different conditions. We also describe the correct methods to extract mobility values and ionization energies from current voltage characteristics.

Muon spin spectroscopy and in particular the avoided level crossing technique is introduced, with the aim of showing it as a very sensitive local probe for electron spin relaxation in organic semiconductors. Avoided level crossing data on tert-butyl-ethynyl anthradithiophene, tri-methyl-silyl-ethynyl anthradithiophene and tri-ethygermyl-ethynyl anthradithiophene at different temperatures are presented. This series of molecules have an identical anthradithiophene backbone, but we have performed a targeted substitution on the central atom of the two side groups, of C, Si and Ge. We extracted the electron spin relaxation for the three molecules of this series and discuss them in the context of previously published results. (C) 2015 Elsevier B.V. All rights reserved.

We report the hyperfine coupling constants of muoniated radicals formed in a number of organic semiconductors, via transverse field measurements taken in the Paschen Back limit, and compare the results to avoided level crossing resonances. Five muoniated radicals are found in tetracene, despite there only being three potential non-equivalent bonding sites, and we suggest that this might be down to crystal packing effects. For 6,13-bis(triisopropylsilylethynyl) pentacene and 6,13-bis(trimethlsilylethyny1)-pentacene, we demonstrate that the transverse field data supports the previously published avoided level crossing resonances.

Accurate determination of the charge transport characteristics of amorphous metal-oxide transistors requires the mitigation of the effects of contact resistance. The use of additional electrodes as voltage probes can overcome contact resistance-related limitations and yields accurate charge carrier mobility values, trap depths and temperature and carrier density dependencies of mobility as well as trap depths. We show that large differences in measured charge carrier mobility values are obtained when such contact resistances are not factored out. Upon exclusion of the contact resistance, the true temperature dependence of charge carrier mobility appears in the form of two clearly distinct mobility regimes. Analyzing these revealed mobility regions leads to a more accurate determination of the underlying transport physics, which shows that contact resistance-related artefacts yield incorrect trends of trap depth with gate voltage, potentially leading to a misconstruction of the charge transport picture. Furthermore, a comparison of low- and high-mobility samples indicates that the observed effects are more general.

The use of implanted muons to probe the spin dynamics and electronic excitations in a variety of magnetic and non-magnetic materials is reviewed and is split into three main sections, the first of which is an introduction to the historical context and background of the muon technique, which includes a basic introduction to the experimental method and underlying theoretical models. The second section is concerned with inorganic magnetic systems, starting with an overview of spin dynamics around critical points in ordered magnets. This is followed by an introduction to the early work on spin glasses, liquids and ices, which then continues onto the recent research in this area, including a discussion of some of the more controversial recent work on spin ices and magnetic monopoles. Information obtained by muons vital to two very important technological areas-magnetic semiconductors and next-generation energy materials-closes the discussion of inorganic magnetic materials. The final section is concerned with spin dynamics and magnetism in soft materials, and starts with discussing many of the key results in molecular magnets and organic spintronics. Spin dynamics in organic semiconductors, polymers and biological molecules is then covered, where contradictory experimental and theoretical work on charge carrier motion is presented. The similarities between the low-field relaxation rates in these 'conducting' organic materials is compared to measurements of the electron spin relaxation measured in localized electronic states, obtained from high-field avoided level crossing spectroscopy in similar (and the same) materials.

Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of the fundamental physics behind electron spin relaxation in organic semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but the role of the spin-orbit interaction remains elusive. Here, we report muon spin spectroscopy and time-resolved photoluminescence measurements on two series of molecular semiconductors in which the strength of the spin-orbit interaction has been systematically modified with a targeted chemical substitution of different atoms at a particular molecular site. We find that the spin-orbit interaction is a significant source of electron spin relaxation in these materials.

Using muon spin rotation (mu SR) we investigated the magnetic and superconducting properties of a series of Ba(Fe1-xCox)(2)As-2 single crystals with 0 <= x <= 0.15. Our study details how the antiferromagnetic order is suppressed upon Co substitution and how it coexists with superconductivity. In the nonsuperconducting samples at 0 < x < 0.04 the antiferromagnetic order parameter is only moderately suppressed. With the onset of superconductivity this suppression becomes faster and it is most rapid between x = 0.045 and 0.05. As was previously demonstrated by mu SR at x = 0.055 [P. Marsik et al., Phys. Rev. Lett. 105, 57001 (2010)], the strongly weakened antiferromagnetic order is still a bulk phenomenon that competes with superconductivity. The comparison with neutron diffraction data suggests that the antiferromagnetic order remains commensurate whereas the amplitude exhibits a spatial variation that is likely caused by the randomly distributed Co atoms. A different kind of magnetic order that was also previously identified [C. Bernhard et al., New J. Phys. 11, 055050 (2009)] occurs at 0.055 < x < 0.075 where T-c approaches the maximum value. The magnetic order develops here only in parts of the sample volume and it seems to cooperate with superconductivity since its onset temperature coincides with Tc. Even in the strongly overdoped regime at x = 0.11, where the static magnetic order has disappeared, we find that the low-energy spin fluctuations are anomalously enhanced below T-c. These findings point toward a drastic change in the relationship between the magnetic and superconducting orders from a competitive one in the strongly underdoped regime to a constructive one in near-optimally and overdoped samples.

Electron spin relaxation rate (eSR) is investigated on several organic semiconductors of different morphologies and molecular structures, using avoided level crossing muon spectroscopy as a local spin probe. We find that two functionalized acenes (polycrystalline tri(isopropyl)silyl-pentacene and amorphous 5,6,11,12-tetraphenyltetracene) exhibit eSRs with an Arrhenius-like temperature dependence, each with two characteristic energy scales similar to those expected from vibrations. Polycrystalline tris(8-hydroxyquinolate)gallium shows a similar behavior. The observed eSR for these molecules is no greater than 0.85 MHz at 300 K. The variety of crystal structures and transport regimes that these molecules possess, as well as the local nature of the probe, strongly suggest an intramolecular phenomenon general to many organic semiconductors, in contrast to the commonly assumed spin relaxation models based on intermolecular charge-carrier transport.

Muon spin spectroscopy and in particular the avoided level crossing technique is introduced, with the aim of showing it as a very sensitive local probe for electron spin relaxation in organic semiconductors. Avoided level crossing data on TMS-pentacene at different temperatures are presented, and they are analysed to extract the electron spin relaxation rate, that is shown to increase on increasing the temperature from 0.02 MHz to 0.33 MHz at 3 K and 300 K respectively.

Nature Materials 10, 39–44 (2011); published online 5 December 2010; corrected after print 18 January 2011. In the version of this Letter originally published, in the paragraph above the Methods section, 'kiloteslas' should have read 'kBT'. This has been corrected in the HTML and PDF versions.

We report muon spin rotation (μSR) and infrared spectroscopy experiments on underdoped BaFe1.89Co0.11As2 which show that bulk magnetism and superconductivity (SC) coexist and compete on the nanometer length scale. Our combined data reveal a bulk magnetic order, likely due to an incommensurate spin density wave (SDW), which develops below T(mag)≈32  K and becomes reduced in magnitude (but not in volume) below Tc=21.7  K. A slowly fluctuating precursor of the SDW seems to develop already below the structural transition at T(s)≈50  K. The bulk nature of SC is established by the μSR data which show a bulk SC vortex lattice and the IR data which reveal that the majority of low-energy states is gapped and participates in the condensate at T≪T(c).

Magnetic properties of thin composite films, consisting of non-interacting polystyrene-coated γ-Fe(2)O(3) (maghemite) nanoparticles embedded into polystyrene-block-polyisoprene P(S-b-I) diblock-copolymer films are investigated. Different particle concentrations, ranging from 0.7 to 43 wt%, have been used. The magnetization measured as a function of external field and temperature shows typical features of anisotropic superparamagnets including a hysteresis at low temperatures and blocking phenomena. However, the data cannot be reconciled with the unmodified Stoner-Wohlfarth-Néel theory. Applying an appropriate generalization we find evidence for either an elastic torque being exerted on the nanoparticles by the field or a broad distribution of anisotropy constants.

inYBa2Cu3O6:6 A. Suchaneck, V. Hinkov, D. Haug, L. Schulz, C. Bernhard, A. Ivanov, K. Hradil, C. T. Lin, P. Bourges, B. Keimer,* and Y. Sidis Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany Physics Department and Fribourg Center for Nanomaterials, Fribourg University, CH-1700 Fribourg, Switzerland Institut Laue-Langevin, 156X, F-38042 Grenoble Cedex 9, France Institute for Physical Chemistry, University of Göttingen, D-37077 Göttingen, Germany Laboratoire Léon Brillouin, CEA-CNRS, CE-Saclay, F-91191 Gif-sur-Yvette, France