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Sulfur and fullerenes are well-known materials that have received significant attention over many years and fullerene–S8 co-crystals have been reported recently. Here, via density functional theory (DFT) calculations, we shed light on the electronic, vibrational, and optical properties of the C60–2S8 and C70–2S8 co-crystals. In both co-crystals, the holes and electrons are characterized by very small effective masses that are comparable to those derived in fullerene single crystals. Interestingly, the S8 molecules are found not to contribute to charge transport as the calculations show that both types of carriers move over the networks formed by the fullerene molecules. Calculations of the excited electronic states point to the formation of charge-transfer states, where electrons are transferred from fullerene molecules to S8 molecules, i.e., the fullerenes act in these co-crystals as electron donors. However, the energies of these charge-transfer states in both C60–2S8 and C70–2S8 are higher than those of several excited states localized on C60 or C70; therefore, the charge-transfer states play no role in the low-energy part of the absorption spectrum. In agreement with experimental data, the calculations also show that the fullerene–S8 inter-molecular interactions are very weak in the ground state; as a result, the infrared (IR) spectra of the co-crystals represent a simple superposition of the spectra of S8 and fullerene molecules. Since the spectra are largely silent in the long-wave IR region (800–1250 cm−1), these fullerene–S8 co-crystals are potential candidates for thermal IR imaging applications. [ABSTRACT FROM AUTHOR]

A new approach to control the n-doping reaction of organic semiconductors is reported using surface-functionalized gold nanoparticles (f-AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n-type dopant precursor N-DMBI-H with several molecular and polymeric semiconductors at different temperatures with/without f-AuNPs, vis-à-vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that while f-AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~10-140 S cm -1 ). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions and will broaden the use of the corresponding n-doped films in opto-electronic devices such as thin-film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Both the intrinsic anisotropic optical materials and fullerene-assembled 2D materials have attracted much interest in fundamental science and potential applications. The synthesis of a monolayer (ML) fullerene makes the combination of these two features plausible. In this work, using first-principles calculations, we systematically study the electronic structure and optical properties of quasi-hexagonal phase (qHP) ML and quasi-tetragonal phase (qTP) ML fullerenes. The calculations of qHP ML show that it is a semiconductor with small anisotropic optical absorption, which agrees with the recent experimental measurements. However, the results for qTP ML reveal that it is a semimetal with highly in-plane anisotropic absorption. The dichroic ratio, namely the absorption ratio of x- and y-polarized light αxx/αyy, is around 12 at photon energy of 0.29 eV. This anisotropy is much more pronounced when the photon energy is between 0.7 and 1.4 eV, where αxx becomes nearly zero while αyy is more than two orders of magnitude larger. This indicates qTP ML as a candidate for long-pursuit lossless metal and a potential material for atomically thin polarizer. We hope this will stimulate further experimental efforts in the study of qTP ML and other fullerene-assembled 2D materials. [ABSTRACT FROM AUTHOR]

The unique formation of an infinity-shaped carbon backbone made exclusively from fused benzene rings has recently been achieved. The structure of [12]infinitene can be viewed as two fused [6]helicene structures with a central crossover section, depicting a global aromatic behavior along with the overall structure, with deshielding regions along both helicoidal axes. In addition, the 13C-NMR characteristics are discussed. The formation of a cumulative region involving the shielding regions from the aromatic rings is depicted along with the overall aesthetically pleasant structural backbone, which is enhanced at the crossover section. For the evaluated dianionic counterpart, the structure shows a deshielding region above the fused-ring trail and a helicoidal shielding region, ascribed to a global antiaromatic counterpart. The aromaticity is recovered and enhanced at the tetranionic state. Thus, the neutral and tetranionic states are able to build up a long-ranged shielding region, given by the global aromatic behavior, with an enhanced shielding region at the center of the crossover section displaying π–π stacked rings. [ABSTRACT FROM AUTHOR]

The configuration of an electric double layer transistor (EDLT) allows for a very high surface charge density that cannot be achieved by solid dielectrics. Novel phases and superconductivity have been explored using the EDLT technique. The channel in an EDLT typically consists of single crystals or two-dimensional materials. When polycrystalline materials with porous surfaces are used as channel materials in an EDLT, it may not be easy to prepare gate electrodes that have a larger surface area than that of the channel to accumulate significant charge on the channel. Based on the impedance measurements, we estimated the electric double layer (EDL) capacitance on porous YBa2Cu3Oy (YBCO), which can be used as a gate electrode. The ratio of the EDL capacitances on YBCO and Au per unit area was found to be larger than 10, implying that the large surface area is associated with the YBCO porosity. The accumulated electrostatic charge on the YBCO electrodes estimated from double-step chronocoulometry is consistent with the EDL capacitance obtained from impedance measurements. Our work should broaden the applicability of EDLT to a wide range of materials, including porous materials. [ABSTRACT FROM AUTHOR]

We study the experimental and theoretical works concerned with the description of state-of-the-art methods for the preparation of iron-containing endohedral metallof)ullerenes (EMF), as well as works, which dispute such results due to the extremely low efficiency of the used methods. We discuss the features of traditional methods for the fabrication of endometallofullerenes, their advantages and disadvantages, and indicate the areas of possible application of the synthesis products. As shown, the EMF is obtained mainly by two methods, namely, arc discharge (plasma) and synthesis using ablation and implantation methods. Despite a very small number of works on iron endometallofullerenes, the group of authors achieved some progress in their analysis. Thus, the fact of obtaining the Fe-containing endometallofullerenes with their isolation from a mixture of synthesis products is proved. In addition, the influence of the magnetic state of metal atoms on the stability of endohedral fullerenes is predicted, a relationship between the EMF output and the plasma temperature as well as the chemical nature of the precursor of Fe atoms are established. Particularly, as found, with an increase of the group number in the periodic table, in which the metal is located, the EMF yield decreases exponentially. We conclude that, due to the magnetic properties of EMF, they are prospective materials in the field of clinical diagnostics (e.g., as a contrast agents in the magnetic resonance imaging) and medicine (for magnetically controlled delivery of drugs directly to a diseased organ). [ABSTRACT FROM AUTHOR]

As one of the 25 physics challenges in this century, high-temperature superconductivity has been of concern for a long time. According to BCS theory, superconductivity is possible if three conditions are met, which are high-frequency phonons, strong electron–phonon coupling, and a high density of states. In theory, the metallic state of hydrogen and hydride under high pressure can satisfy the above conditions. Several binary hydride systems have been experimentally proved to be high-temperature superconductors (HTSs) at high pressure. Ternary hydrides can be regarded as the doping of binary hydrides, which have broad prospects. At present, in both experimental and theoretical research, ternary hydrides are the record holder for the highest superconducting critical temperature ( T c) which is 287 K in C–H–S system, and 473 K in Li–Mg–H system, respectively. This review will systematically describe the research status of superconductivity on ternary hydride at high pressure. Relevant theoretical research was classified according to different binary hydride doping systems. The experimental research was then introduced. In terms of experimental research, we focus on the latest research of C–S–H and La–Y–H HTSs, and overview the subsequent studies about high T c of C–S–H system. [ABSTRACT FROM AUTHOR]

Functionalized fullerene nanostructures are a distinct class of materials that exhibit the combined properties of both fullerene and nanostructures including excellent optoelectronic features, modified band edges, high electron affinity, fast charge transfer capabilities, and tunable structural and textural properties. These fascinating properties allow for their utilization in many applications such as polymer solar cells, photovoltaics, photocatalysis, photodynamic therapy, electrocatalysis, environmental remediation, and drug and gene delivery. Numerous synthesis methods and anchoring groups are employed for functionalized fullerenes with nanostructures by using convergent bottom‐up and top‐down strategies. The supramolecular self‐assembly and functionalization of fullerenes through robust chemistry approaches such as surface oxidation, grafting, polymer coating, doping of metals/nonmetal heteroatoms, noncovalent modification with 2D materials and nanoparticle attachment result in achieving fine control over its surface and bulk properties, including increased solubility, wettability, electron transport, acid–base properties, adsorption, electronic conductivity, and light absorption. This review analyzes the salient developments in the fabrication of nanostructured fullerenes and their functionalized derivatives for many applications including adsorption, catalysis, sensors, energy storage, solar cells, drug delivery, magnetic and superconducting devices. The contents of this review will allow the readers to cherish exciting possibilities and opportunities in field of functionalized nanofullerenes. [ABSTRACT FROM AUTHOR]

Ferroelectric interfacial devices consist of materials systems whose interfacial electronic properties (such as a 2D electron gas or an interfacial magnetic spin configuration) are modulated by a ferroelectric layer set in its immediate vicinity. While the prototypical example of such a system is the ferroelectric field effect transistor first proposed in the 1950s, only with the recent advances in the controlled growth of epitaxial thin films and heterostructures, and the recent physical understanding down to the atomic scale of screening processes at ferroelectric-semiconducting and -metallic interfaces made possible by first principles calculations, have the conditions been met for a full development of the field. In this review, we discuss the recent advances in ferroelectric interfacial systems with emphasis on the ferroelectric control of the electronic properties of interfacial devices with well ordered (epitaxial) interfaces. In particular, we consider the cases of ferroelectric interfacial systems aimed at controlling the correlated state, including superconductivity, Mott metallic-insulator transition, magnetism, charge, and orbital order, and charge and spin transport across ferroelectric tunnel junctions. The focus is on the basic physical mechanisms underlying the emergence of interfacial effects, the nature of the ferroelectric control of the electronic state, and the role of extreme electric field gradients at the interface in giving rise to new physical phenomena. Such understanding is key to the development of ferroelectric interfacial systems with characteristics suitable for next generation electronic devices based on controlling the correlated state of matter. [ABSTRACT FROM AUTHOR]

Two subvalent, redox‐active diborane(4) anions, [3]4− and [3]2−, carrying exceptionally high negative charge densities are reported: Reduction of 9‐methoxy‐9‐borafluorene with Li granules without stirring leads to the crystallization of the B(sp3)−B(sp2) diborane(5) anion salt Li[5]. [5]− contains a 2,2′‐biphenyldiyl‐bridged B−B core, a chelating 2,2′‐biphenyldiyl moiety, and a MeO substituent. Reduction of Li[5] with Na metal gives the Na+ salt of the tetraanion [3]4− in which two doubly reduced 9‐borafluorenyl fragments are linked via a B−B single bond. Comproportionation of Li[5] and Na4[3] quantitatively furnishes the diborane(4) dianion salt Na2[3], the doubly boron‐doped congener of 9,9′‐bis(fluorenylidene). Under acid catalysis, Na2[3] undergoes a formal Stone–Wales rearrangement to yield a dibenzo[g,p]chrysene derivative with B=B core. Na2[3] shows boron‐centered nucleophilicity toward n‐butyl chloride. Na4[3] produces bright blue chemiluminescence when exposed to air. [ABSTRACT FROM AUTHOR]

In this work, we designed Li‐ and Na‐doped homo‐ and heterodinuclear helical molecules, that is, Li2‐sexipy with two Li atoms, LiNa‐sexipy with Li and Na atoms, and Na2‐sexipy with two Na atoms. LiNa‐sexipy exhibited shorter Li‐L length compared with Li2‐sexipy; longer Na‐L length compared with Na2‐sexipy; and more charge polarization, especially along the vertical direction. Thus, the largest βtot value of LiNa‐sexipy among three molecules was observed. However, the loss of conjugation did not attenuate nonlinear optics (NLO) response. In addition, the maximum absorptions for the three helicates were all at the ultraviolet region, which suggested the performance of their transparency. These results indicated the advantages of heterodinuclear helix in this work and provided a new strategy of alkali metal doping to solve the conflict between transparency and NLO properties and enhance the NLO response of materials. [ABSTRACT FROM AUTHOR]

We present experimental data on the synthesis and investigation of the superconducting and structural properties of organometallic fullerides M(3−n)(NR4)(n)C60, where M = K, Rb; R = hydrogen H, deuterium D, methyl Me, ethyl Et, butyl Bu; n = 1, 2, 3, synthesized by exchange reactions of homofullerides of alkali metals of composition K3C60 and Rb3C60 with ammonium halides in the medium of absolute toluene or tetrahydrofuran (THF) at temperatures from 23°C to 110°C. We have studied also superconductivity in Rb2NH4C60 and Rb2ND4C60 samples with replacement of hydrogen for deuterium in ammonium, as well as in K2NH4C60 and K2ND4C60. The superconducting transition temperature did not change with replacement H by D within the measurement accuracy. [ABSTRACT FROM AUTHOR]

Chemical modification such as intercalation or doping of novel materials is of great importance for exploratory material science and applications in various fields of physics and chemistry. Herein, the systematic intercalation of chemically exfoliated few‐layer graphene with potassium is reported while monitoring the sample resistance using microwave conductivity. It is found that the conductivity of the samples increases by about an order of magnitude upon potassium exposure. The increased number of charge carriers deduced from the electron spin resonance (ESR) intensity also reflects this increment. The doped phases exhibit two asymmetric Dysonian lines in ESR, a usual sign of the presence of mobile charge carriers. The width of the broader component increases with the doping steps; however, the narrow components seem to have a constant line width. [ABSTRACT FROM AUTHOR]

According to the classic concept of photovoltaic devices, p–n junctions and heterojunctions are indispensable for carrier separation. Herein, for the first time, a novel concept of "anisotropic crystal facet unit" is put forward and clarified for photovoltaic and thermoelectric power generation. Specifically, an "anisotropic crystal facet unit" in monocrystalline p‐Cu2O between the {100} and the {111} crystal faces is built, which can fulfill self‐motivated carrier separation, due to their natural energy difference. The "anisotropic crystal facet unit" devices can directly and efficiently convert light and heat into electricity, where the {100} and the {111} faces act as the cathode and the anode, respectively. Moreover, hot and cold regions are unnecessary when the "anisotropic crystal facet unit" is applied in thermoelectric conversion. These findings may update the understanding of solar cells and thermoelectric cells, and blaze a new trail through the development of efficient and low‐cost energy utilization technologies. [ABSTRACT FROM AUTHOR]

We report on the realization of Nb-based all-metallic Dayem nano-bridge gate-controlled transistors (Nb-GCTs). These Josephson devices operate up to a temperature of ∼ 3 K and exhibit full suppression of the supercurrent thanks to the application of a control gate voltage. The dependence of the kinetic inductance and of the transconductance on gate voltage promises a performance already on par with so far realized metallic Josephson transistors and leads us to foresee the implementation of a superconducting digital logic based on the Nb-GCT. We conclude by showing the practical realization of a scheme implementing an all-metallic gate-tunable half-wave rectifier to be used for either superconducting electronics or photon detection applications. [ABSTRACT FROM AUTHOR]

A global theoretical study of the (hyper)polarizabilities of alkali doped Si10 is presented and discussed. First, a detailed picture about the low lying isomers of Si10Li, Si10Na, Si10K, Si10Li2, Si10Na2, and Si10K2 has been obtained in a global manner. Then, the microscopic first (hyper)polarizabilities of the most stable configurations have been determined by means of ab initio methods of high predictive capability such as those based on the Mo\ller-Plesset perturbation and coupled cluster theory, paying extra attention to the (hyper)polarizabilities of the open shell mono-doped systems Si10Li, Si10Na, Si10K, and the influence of spin contamination. These results were used to assess the performance of methods of low computational cost based on density functional theory (DFT) in the reliable computation of these properties in order to proceed with an in-depth study of their evolution as a function of the alkali metal, the cluster composition, and the cluster structure. The most interesting outcomes of the performed (hyper)polarizability study indicate that while alkali doping leaves the per atom polarizability practically unaffected, influences dramatically the hyperpolarizabilities of Si10. The lowest energy structures of the mono-doped clusters are characterized by significantly enhanced hyperpolarizabilities as compared to the analogue neutral or charged bare silicon clusters Si10 and Si11, while, certain patterns governed by the type and the number of the doping agents are followed. The observed hyperpolarizability increase is found to be in close connection with specific cluster to alkali metal charge transfer excited states and to the cluster structures. Moreover, an interesting correlation between the anisotropy of the electron density, and the hyperpolarizabilities of these systems has been observed. Finally, it is important to note that the presented method assessment points out that among the various DFT functionals used in this work, (B3LYP, B3PW91, BhandHLYP, PBE0, CAM-B3LYP, LC-BLYP, LC-BPW91) only B3PW91 and PBE0 out of the seven provided a consistent quantitative performance for both polarizabilities and hyperpolarizabilities with respect to the ab initio methods utilized here. On the other hand, the long range corrected functionals LC-(U)BLYP and LC-(U)BPW91 (μ = 0.47) failed to supply quantitatively accurate hyperpolarizability results in all the studied clusters while the CAM-(U)B3LYP functional performs satisfactory only in the case of the Na and K doped systems. [ABSTRACT FROM AUTHOR]

Properties of nanocomposites composed of fullerene C60 chemically bonded to Al nanocrystals are reported. The nanocomposites of Al-C60 create a class of new material of fulleride of aluminum nanoclusters. New nanostructured and modified by C60 aluminum-based material has been sintered from fulleride of aluminum nanoclusters. Key features of this material are creating covalent bonds Al-C60 and preserving C60 during sintering. Addition of several wt % of C60 essentially improves (by a factor of 3 to 10, up to 7 GPa) the hardness of initial aluminum. [ABSTRACT FROM AUTHOR]

The interaction of C60 with the Au(111) surface has been investigated using synchrotron radiation-based electron spectroscopy. Resonant photoelectron spectroscopy and autoionization spectroscopy have been used to probe the coupling between the molecule and the substrate. Three distinct high energy spectator Auger features were observed that are only evident for a monolayer of C60 chemisorbed to the Au(111) surface and not a multilayer or the clean surface itself. Combined with C 1s x-ray absorption and valence band spectra, the data suggest a decay process not previously reported for this system. This is a spectator decay channel involving electrons transferred from the gold substrate to the adsorbed molecule, either in the ground state or during the timescale of the core-hole lifetime. Both possibilities are considered in the interpretation of the results, which support, on balance, a ground state charge transfer. [ABSTRACT FROM AUTHOR]

The electronic structure of single and multiple layers of C60 molecules deposited on a Rh(100) surface is investigated by means of valence photoemission spectroscopy and density functional theory calculations. The binding of the fullerene monolayer to the metal surface yields the appearance of a new state in the valence band spectrum crossing the Fermi level. Insight into the metallization of the metal/fullerene interface is provided by the calculated electronic structure that allows us to correlate the measured interface state with a strong hybridization between the Rh metal states and the highest and lowest molecular orbitals. This results in a net charge transfer of ≈0.5e–0.6e from the metal to the p states of the interfacial C atoms. The charge transfer is shown to be very short range, involving only the C atoms bound to the metal. The electronic structure of the second C60 layer is already insulating and resembles the one measured for C60 multilayers supported by the same substrate or calculated for fullerenes isolated in vacuum. The discussion of the results in the context of other C60/metal systems highlights the distinctive electronic properties of the molecule/metal interface determined by the Rh support. [ABSTRACT FROM AUTHOR]

We have used large-scale first-principles calculations based on density functional theory to investigate the structure, energetics, electronic, and magnetic structures of Fen-doped C60 monolayers supported by h-BN monolayer-covered Ni(111) surfaces. A systematic study of n-dependent physical properties has been performed (n=1–4,15). Binding energies on Fe atoms to the Fen-1–C60 complex have been calculated for n=1–4 after a thorough configuration search and structural optimization. The binding energy, electron charge transfer (from Fen to C60), and magnetic moment all increase monotonically as functions of n. The electron charge transfer, ranging from ∼1e- to 5e-, is from the spin minority population. This leads to a situation in which the net spin of the C60 molecule aligns with the spin minority and the magnetic moment in C60 is opposite to the total magnetic moment of the system. For n=2, a competing antiferromagnetic state has been found. In this state, the net spin of the system as well as the C60 is zero. Density of states and projected density of states analysis indicate that the system becomes metallic upon metal doping regardless its magnetic state. In addition, we have also performed calculations with the Hubbard U term (DFT+U) for two systems, n=4 and 15, to investigate possible gap opening near the Fermi surface. [ABSTRACT FROM AUTHOR]

A systematic study on the energy level alignment, chemical interaction, and electron doping at interfaces between bathocuproine (BCP) and various types of metals (Au, Cu, Ag, Mg, and Ca) was carried out by performing ultraviolet photoelectron spectroscopy and electronic conductivity measurements. The energy level alignment at BCP/metal interfaces was found to depend on the metal work function ([uppercase_phi_synonym]m). For BCP on Au and Cu, whose [uppercase_phi_synonym]m exceeds 4.3 eV, the energy shift in the highest occupied molecular orbital (HOMO) level with respect to the metal Fermi level (EF) almost accords with the variation in [uppercase_phi_synonym]m. For BCP on Ag, Mg, and Ca, whose [uppercase_phi_synonym]m is below 4.3 eV, the HOMO energy level is fixed at 3.7 eV with respect to EF regardless of [uppercase_phi_synonym]m and new electronic states, called gap states, appeared at BCP/metal interfaces. Since the appearance of gap states is correlated with the energy of the lowest unoccupied molecular orbital (LUMO) level with respect to EF, these states appear to have formed mainly through the interaction with the LUMO. A clear correlation between the density of the gap states and the vacuum level shift suggesting a charge redistribution at BCP/metal interfaces was found. The energy shift in the gap states, which may originate from the variation in the electron occupation of the states, directly affected the electronic conductivity of metal-doped BCP layers (doping metal=Au, Ag, and Ca). These results suggest the electron transfer from the metal EF to gap states plays an influential role in the electrical properties at BCP/metal interfaces. [ABSTRACT FROM AUTHOR]

The equation describing the capacitance of capacitors is determined. It is shown that by optimizing the material of the conducting electrodes, the capacitance of capacitors reaching the quantum regime can be substantially enhanced or reduced. Dielectric capacitors with negative total capacitances are suggested and their properties analyzed. Resulting perspectives to enhance the performance of electronic devices are discussed. [ABSTRACT FROM AUTHOR]

The temperature dependence of capacitance, C[sub M], and conductance, G[sub M], of Al-Al[sub 2]O[sub 3]-metal capacitors with Cu, Ag, and Au electrodes has been measured between 100 and 340 K at seven frequencies between 10 kHz and 1 MHz. Al[sub 2]O[sub 3] films between 15 and 64 nm thick were formed by anodizing evaporated Al films in borate-glycol or borate-H[sub 2]O electrolyte. The interface capacitance at the Al[sub 2]O[sub 3]-metal interface, C[sub I], which is in series with the capacitance C[sub D] due to the Al[sub 2]O[sub 3] dielectric, is determined from plots of 1/C[sub M] versus insulator thickness. C[sub I] is not fixed for a given metal-insulator interface but depends on the vacuum system used to deposit the metal electrode. C[sub I] is nearly temperature independent. When C[sub I] is taken into account the dielectric constant of Al[sub 2]O[sub 3] determined from capacitance measurements is ∼8.3 at 295 K. The dielectric constant does not depend on anodizing electrolyte, insulator thickness, metal electrode, deposition conditions for the metal electrode or measurement frequency. By contrast, G[sub M] of Al-Al[sub 2]O[sub 3]-metal capacitors depends on both the deposition conditions of the metal and on the metal. For Al-Al[sub 2]O[sub 3]-Cu capacitors, G[sub M] is larger for capacitors with large values of 1/C[sub I] that result when Cu is evaporated in an oil-pumped vacuum system. For Al-Al[sub 2]O[sub 3]-Ag capacitors, G[sub M] does not depend on the Ag deposition conditions. [ABSTRACT FROM AUTHOR]

The capacitance of Al-Al[sub 2]O[sub 3]-metal capacitors with Al[sub 2]O[sub 3] of different thicknesses, formed by anodizing evaporated Al films in ethylene glycol-based or H[sub 2]O-based electrolytes to different voltages, has been measured between 10 kHz and 1 MHz for ten metal electrodes. The linear dependence of inverse capacitance on anodizing voltage, and thus on Al[sub 2]O[sub 3] thickness, shows that there is an interface capacitance in series with the bulk capacitance due to the dielectric properties of anodized Al[sub 2]O[sub 3]. The interface capacitance, C[sub I], is not a characteristic of the Al[sub 2]O[sub 3]-metal combination; it depends on the vacuum deposition conditions for the metal electrodes. C[sub I] is associated with interface states at the Al[sub 2]O[sub 3]-metal interface, not with field penetration into metal electrodes. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the process of plasma oxidation of a thin aluminum layer. Use of transmission electron microscopy to determine the thickness of the oxides; Use of Rutherford backscattering spectrometry and elastic recoil detection to measure oxygen content; Characterization of the oxide through ac impedance measurements.

Although the improvement of power conversion efficiency (PCE) in organic photovoltaic cells (OSC) is due to the development of novel donors and non-fullerene acceptors, state-of-the-art devices commonly utilize charge transporting/extraction interlayers. Here we demonstrate a universal approach based on a series of tetraalkyl ammonium bromide (TXABr) Lewis bases as ndopants for mediating electron extracting properties in a range of OSCs with non-fullerene or PCBM acceptors. Under optimal conditions, the TXABr-doped devices without electron transporting layers (ETLs) exhibit PCEs comparable to those of the ones based on a conventional device structure containing ETLs. We found that the doping efficiency of acceptors is intimately correlated with the chain length (Lchain) of dopants. In OSCs based on acceptors of ITIC derivatives (IT-4F, ITIC, ITM, and ITCC), similar Lchain-dependent doping efficiency and PCE modification are found, while for OSCs with acceptors bearing different structures in conjugated backbones or side chains, the selection rule of dopants to achieve the best performance enhancement is different. These correlations are explained by the mutual effects of electrostatic interaction in the dopants and steric hindrance between the dopants and acceptors, the latter of which is affected by the compatibility of side chains in the host and dopant. With TXABr doping, (quasi-)ohmic contacts for electrons are realized in these ETL-free devices, leading to expediting the charge sweepout with mitigated interfacial charge recombination. This work offers a promising pathway to realize high efficiency non-fullerene OSCs with simplified device architecture. [ABSTRACT FROM AUTHOR]

A systematic screening study of the exohedral reactivity of the reduced fullerenes (fullerenides) C602− and C60⋅− is reported. These doubly and singly negatively charged carbon cages were prepared by two‐fold reduction of C60 with potassium, leading to K2C60, or by in situ monoreduction with the radical anion of benzonitrile PhCN⋅−, respectively. Several series of electrophiles, including geminal and distant dihalides, benzyl bromides, and diazonium compounds, were employed as addition partners. In general, the investigated bromides proved to be the most suitable reaction partners. A series of fullerene adducts and cycloadducts involving either 1,2‐ or 1,4‐addition patterns, depending on the precise architecture and the steric demand of the addends, were synthesized and fully characterized. Some of the reaction products are unprecedented and inaccessible forms of neutral C60. The fullerenide chemistry presented here closely resembles related reactions of graphenides and carbon nanotubides, which are the most powerful methods for the functionalization of these macromolecular forms of synthetic carbon allotropes (SCAs). Activation of C60 by negative charging represents a little explored concept of fullerene chemistry, providing both new insights of fullerene reactivity itself and new types of exohedral derivatives. New additions to the family: Insights into the reductive functionalization of fullerenes and its application for preparing highly sophisticated fullerene architectures including an unprecedented 1,4‐cycloadduct are presented. Investigations on the exohedral reactivity of fullerenides and the scope of different electrophiles as addition partners leading to a series of fullerene adducts and cycloadducts involving either 1,2‐ or 1,4‐addition patterns are reported. [ABSTRACT FROM AUTHOR]

Carbon materials are among the most commonly used components of supercapacitor electrodes. Particularly, active carbons are recognized as cheap, available, and easily tailored materials. However, the carbon family, i.e. carbon products and carbon precursors, consists of many members. In this manuscript some of these materials, including laboratory scale-produced carbon gels, carbon nanotubes and carbonized materials, as well as industrial scale-produced graphites, pitches, coke and coal, were compared. Discussion was preceded by a short history of supercapacitors and review of each type of tested material, from early beginning to state-of-the-art. Morphology and structure of the materials were analyzed (specific surface area, pore volume and interlayer spacing determination), to evaluate their applicability in energy storage. Thermal analysis was used to determine the stability and purity. Finally, electrochemical evaluation using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy was performed. Outcomes of each analytical technique were summarized in different sections. [ABSTRACT FROM AUTHOR]

Discusses the fabrication and characterization of high critical temperature Josephson junctions in thin films of YBa2Cu3O7-delta produced by the process of focused electron-beam irradiation. Description in terms of the resistive junction model; Superconducting material of reduced or zero critical temperature; Oxygen Frenkel defects in the Cu-O planes.

Examines the relationship between electrical transport and hole concentration in YBA2Cu3O7-x ultrathin films. Use of superconducting field effect transistors; Determination of the hole concentration change; Measurement of the field-induced dielectric polarization of the SrTiO3 dielectric.

Examines the characterization and micro-Raman spectra of the intercalation of Bi2Sr2CaCu2O8+ gamma single crystal with C60. Changes in vibrational electronic and structural characteristics of guest and host specie; Appearance of forbidden modes in the Raman spectra.

Examines the electric field effect on the transport properties of ultrathin high-temperature superconductor channels in the insulating phase of superconductor-insulator transition. Modulation ratio of conductance; Association of field effect mobility with increasing channel thickness.

Presents a study that examined the formation of buried potassium-fulleride layers. Use of Raman scattering and grazing-angle x-ray diffraction; Discussion on potassium doping; Information on various thermodynamic processes including segregation, phase formation and diffusion.