Exploring the heteroanionic 2D materials RhSeCl and RhTeCl as promising semiconductor materials.

Heteroanionic materials show promising potential as 2D semiconductors due to their tunable band gaps, making them excellent candidates for photocatalytic water splitting applications. We conducted detailed theoretical and experimental analysis of two selected materials by synthesizing crystals through chemical vapor transport and investigating the impact of anion variation on crystal structure and properties. Using powder X-ray diffraction and convergent beam electron diffraction, we elucidated the non-centrosymmetric space groups of these compounds.

Directed exciton transport highways in organic semiconductors.

Exciton bandwidths and exciton transport are difficult to control by material design. We showcase the intriguing excitonic properties in an organic semiconductor material with specifically tailored functional groups, in which extremely broad exciton bands in the near-infrared-visible part of the electromagnetic spectrum are observed by electron energy loss spectroscopy and theoretically explained by a close contact between tightly packing molecules and by their strong interactions. This is induced by the donor-acceptor type molecular structure and its resulting crystal packing, which induces a remarkable anisotropy that should lead to a strongly directed transport of excitons.

Correction to: Optical Anisotropy and Momentum-Dependent Excitons in Dibenzopentacene Single Crystals.

[This corrects the article DOI: 10.1021/acsomega.2c01987.

On-chip integrated process-programmable sub-10 nm thick molecular devices switching between photomultiplication and memristive behaviour.

Molecular devices constructed by sub-10 nm thick molecular layers are promising candidates for a new generation of integratable nanoelectronic applications. Here, we report integrated molecular devices based on ultrathin copper phthalocyanine/fullerene hybrid layers with microtubular soft-contacts, which exhibit process-programmable functionality switching between photomultiplication and memristive behaviour. The local electric field at the interface between the polymer bottom electrode and the enclosed molecular channels modulates the ionic-electronic charge interaction and hence determines the transition of the device function.

Synthesis and charge transfer characteristics of a ruthenium-acetylide complex.

A novel ruthenium-acetylide complex was synthesised and characterised in solid state and solution. Thin films of the complex were evaporated on silver and gold foils in ultra high vacuum in order to probe the electronic properties with photoemission spectroscopy. The charge transfer characteristics of the complex with the strong acceptor FTCNNQ were investigated by UV-vis absorption in solution as well as at an interface with photoemission spectroscopy.

Evolution of Structure and Electronic Correlations in a Series of BaTAs (T = Cr-Cu) Single Crystals.

We present a systematic study of the evolution of structural parameters and electronic correlations as a function of 3d band filling in a single crystal series of BaTAs (T = Cr-Cu). The structure trends are discussed in relation to the orbital occupation of the corresponding d elements supported by calculations of the charge density and electron localization function. Analysis of our specific heat data yields the mass enhancement (*/) throughout the series.

Integrated molecular diode as 10 MHz half-wave rectifier based on an organic nanostructure heterojunction.

Considerable efforts have been made to realize nanoscale diodes based on single molecules or molecular ensembles for implementing the concept of molecular electronics. However, so far, functional molecular diodes have only been demonstrated in the very low alternating current frequency regime, which is partially due to their extremely low conductance and the poor degree of device integration. Here, we report about fully integrated rectifiers with microtubular soft-contacts, which are based on a molecularly thin organic heterojunction and are able to convert alternating current with a frequency of up to 10 MHz.

An unusual donor-acceptor system MnPc-TCNQ/F-TCNQ and the properties of the mixed single crystals of metal phthalocyanines with organic acceptor molecules.

The interaction of manganese(ii) phthalocyanine with 7,7,8,8-tetracyanoquinodimethane and its perfluoro derivative proceeds with the oxidation of Mn and the reduction of the acceptor molecules to give the first mixed single crystals of manganese(iii) phthalocyanine with TCNQ/F4-TCNQ radical anions. The crystals have unusual structures with C-Hπ interactions between the ions and their orthogonal arrangement, as well as remarkable redox properties. The charge transfer was proved by spectroscopic and magnetic studies.

Complex momentum behavior of electronic excitations in -CuPc.

The electronic excitation spectrum of -CuPc has been investigated using electron energy-loss spectroscopy in transmission. Our results demonstrate a rather strong momentum dependence of the lowest exciton features. Both main components show a negative dispersion, and the momentum dependence indicates that this negative dispersion is parallel to the molecular stacks in -CuPc.

Investigation of indirect excitons in bulk 2H-MoS using transmission electron energy-loss spectroscopy.

We have investigated indirect excitons in bulk 2H-MoS using transmission electron energy-loss spectroscopy. The electron energy-loss spectra were measured for various momentum transfer values parallel to the [Formula: see text] and [Formula: see text] directions of the Brillouin zone. The results allowed the identification of the indirect excitons between the valence band K and conduction band Λ points, the Γ and K points as well as adjacent K and [Formula: see text] points.

Electronic excitations of manganese phthalocyanine molecules.

We have investigated the electronic excitation spectrum of individual manganese phthalocyanine (MnPc) molecules in a coronene matrix. Our results corroborate that the observed excitation spectrum is rather sensitive to oxygen contamination of the respective samples. Annealing in vacuum allowed the determination of the electronic excitations of individual MnPc molecules.

Charge transfer from and to manganese phthalocyanine: bulk materials and interfaces.

Manganese phthalocyanine (MnPc) is a member of the family of transition-metal phthalocyanines, which combines interesting electronic behavior in the fields of organic and molecular electronics with local magnetic moments. MnPc is characterized by hybrid states between the Mn 3d orbitals and the π orbitals of the ligand very close to the Fermi level. This causes particular physical properties, different from those of the other phthalocyanines, such as a rather small ionization potential, a small band gap and a large electron affinity.

Energy-level alignment at interfaces between manganese phthalocyanine and C.

We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the fullerene C. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of the two lowest unoccupied molecular orbitals (LUMOs) is rather small.

Semiconductor-to-metal transition in the bulk of WSe upon potassium intercalation.

We present electron energy-loss spectroscopic measurements of potassium (K) intercalated tungsten diselenide (WSe). After exposure of pristine WSe films to potassium, we observe a charge carrier plasmon excitation at about 0.97 eV, which indicates a semiconductor-to-metal transition.

STM Study of Au(111) Surface-Grafted Paramagnetic Macrocyclic Complexes [Ni2L(Hmba)](+) via Ambidentate Coligands.

Molecular anchoring and electronic properties of macrocyclic complexes fixed on gold surfaces have been investigated mainly by using scanning tunnelling microscopy (STM) and complemented with X-ray photoelectron spectroscopy (XPS). Exchange-coupled macrocyclic complexes [Ni2L(Hmba)](+) were deposited via 4-mercaptobenzoate ligands on the surface of a Au(111) single crystal from a mM solution of the perchlorate salt [Ni2L(Hmba)]ClO4 in dichloromethane. The combined results from STM and XPS show the formation of large monolayers anchored via Au-S bonds with a height of about 1.

Impact of potassium doping on the electronic structure of tetracene and pentacene: An electron energy-loss study.

We report the doping induced changes of the electronic structure of tetracene and pentacene probed by electron energy-loss spectroscopy in transmission. A comparison between the dynamic response of undoped and potassium-intercalated tetracene and pentacene emphasizes the appearance of a new excitation feature in the former gap upon potassium addition. Interestingly, the momentum dependency of this new excitation shows a negative dispersion.

Universal electronic structure of polar oxide hetero-interfaces.

The electronic properties of NdGaO3/SrTiO3, LaGaO3/SrTiO3, and LaAlO3/SrTiO3 interfaces, all showing an insulator-to-metal transition as a function of the overlayer-thickness, are addressed in a comparative study based on x-ray absorption, x-ray photoemission and resonant photoemission spectroscopy. The nature of the charge carriers, their concentration and spatial distribution as well as the interface band alignments and the overall interface band diagrams are studied and quantitatively evaluated. The behavior of the three analyzed heterostructures is found to be remarkably similar.

An electron energy-loss study of picene and chrysene based charge transfer salts.

The electronic excitation spectra of charge transfer compounds built from the hydrocarbons picene and chrysene, and the strong electron acceptors F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and TCNQ (7,7,8,8-tetracyanoquinodimethan) have been investigated using electron energy-loss spectroscopy. The corresponding charge transfer compounds have been prepared by co-evaporation of the pristine constituents. We demonstrate that all investigated combinations support charge transfer, which results in new electronic excitation features at low energy.

Encapsulation of the 4-mercaptobenzoate ligand by macrocyclic metal complexes: conversion of a metallocavitand to a metalloligand.

Complexation of the ambidentate ligand 4-mercaptobenzoate (4-SH-C6H4CO2H, H2mba) by the macrocyclic complex [Ni2L(μ-Cl)]ClO4 (L(2-) represents a 24-membered macrocyclic hexaazadithiophenolate ligand) has been examined. The monodeprotonated Hmba(-) ligand reacts with the Ni2 complex in a selective manner by substitution of the bridging chlorido ligand to produce μ1,3-carboxylato-bridged complex [Ni2L(Hmba)](+) (2(+)), which can be isolated as an air-sensitive perchlorate (2ClO4) or tetraphenylborate (2BPh4) salt. The reactivity of the new mercaptobenzoate complex is reminiscent of that of a "free" thiophenolate ligand.

Epitaxial growth and electronic properties of well ordered phthalocyanine heterojunctions MnPc/F₁₆CoPc.

We have prepared phthalocyanine heterojunctions out of MnPc and F16CoPc, which were studied by means of X-ray absorption spectroscopy. This heterojunction is characterized by a charge transfer at the interface, resulting in charged MnPc(δ +) and F16CoPc(δ -) species. Our data reveal that the molecules are well ordered and oriented parallel to the substrate surface.

Chemisorption of exchange-coupled [Ni2L(dppba)]+ complexes on gold by using ambidentate 4-(diphenylphosphino)benzoate co-ligands.

A new strategy for the fixation of redox-active dinickel(II) complexes with high-spin ground states to gold surfaces was developed. The dinickel(II) complex [Ni2L(Cl)]ClO4 (1ClO4), in which L(2-) represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, reacts with ambidentate 4-(diphenylphosphino)benzoate (dppba) to form the carboxylato-bridged complex [Ni2L(dppba)](+), which can be isolated as an air-stable perchlorate [Ni2L(dppba)]ClO4 (2ClO4) or tetraphenylborate [Ni2L(dppba)]BPh4 (2BPh4) salt. The auration of 2ClO4 was probed on a molecular level, by reaction with AuCl, which leads to the monoaurated Ni(II)2Au(I) complex [Ni(II)2L(dppba)Au(I)Cl]ClO4 (3ClO4).

Phthalocyanine dimers in a blend: spectroscopic and theoretical studies of MnPc(δ +)/F(16)CoPc(δ -).

We have prepared mixed phthalocyanine films out of MnPc and F(16)CoPc, which were characterized by means of photoemission spectroscopy and electron energy-loss spectroscopy. Our data reveal the formation of MnPc/F(16)CoPc charge transfer dimers in analogy to the related heterojunction. The electronic excitation spectrum of these blends is characterized by a new low energy excitation at 0.

Understanding high-yield catalyst-free growth of horizontally aligned single-walled carbon nanotubes nucleated by activated C60 species.

Our understanding of the catalyst-free growth of single-walled carbon nanotubes by chemical vapor deposition is limited. Toward improving our knowledge base, we conducted systematic investigations into the initial preparation of C(60) fullerenes as nucleation precursors for single-wall and even double-wall carbon nanotube fabrication. The role of the dispersing media is shown to be crucial and is related to the initial fullerene cluster size.