Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userElectronic properties of Mn-Phthalocyanine - C$_{60}$ bulk heterojunctions: combining photoemission and electron energy-loss spectroscopy
183
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C$_{60}$ (MnPc:C$_{60}$) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) as well as electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C$_{60}$. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C$_{60}$ bulk heterojunction. Moreover, the results from our EELS investigations show that despite of the rather small interface interaction the MnPc related electronic excitation spectrum changes significantly by admixing C$_{60}$ to MnPc thin films.
rate research
Read More
Phthalocyanines in combination with C$_{60}$ are benchmark materials for organic solar cells. Here we have studied the morphology and electronic properties of co-deposited mixtures (blends) of these materials forming a bulk heterojunction as a function of the concentration of the two constituents. For a concentration of 1:1 of CuPc:C$_{60}$ a phase separation into about 100 nm size domains is observed, which results in electronic properties similar to layered systems. For low C$_{60}$ concentrations (10:1 CuPc:C$_{60}$) the morphology, as indicated by Low-Energy Electron Microscopy (LEEM) images, suggests a growth mode characterized by (amorphous) domains of CuPC, whereby the domain boundaries are decorated with C$_{60}$. Despite of these markedly different growth modes, the electronic properties of the heterojunction films are essentially unchanged.
The spatial distributions of anti-bonding $pi^ast$ and $sigma^ast$ states in epitaxial graphene multilayers are mapped using electron energy-loss spectroscopy in a scanning transmission electron microscope. Inelastic channeling simulations validate the interpretation of the spatially-resolved signals in terms of electronic orbitals, and demonstrate the crucial effect of the material thickness on the experimental capability to resolve the distribution of unoccupied states. This work illustrates the current potential of core-level electron energy-loss spectroscopy towards the direct visualization of electronic orbitals in a wide range of materials, of huge interest to better understand chemical bonding among many other properties at interfaces and defects in solids.
There has been growing interest in perovskite BaSnO3 due to its desirable properties for oxide electronic devices including high electron mobility at room temperature and optical transparency. As these electronic and optical properties originate largely from the electronic structure of the material, here the basic electronic structure of epitaxially-grown BaSnO3 films is studied using high-energy-resolution electron energy-loss spectroscopy in a transmission electron microscope and ab initio calculations. This study provides a detailed description of the dielectric function of BaSnO3, including the energies of bulk plasmon excitations and critical interband electronic transitions, the band structure and partial densities of states, the measured band gap, and more. To make the study representative of a variety of deposition methods, results from BaSnO3 films grown by both hybrid molecular beam epitaxy and high pressure oxygen sputter deposition are reported.
The electronic excitation spectra of undoped, and potassium as well as calcium doped phenantrene-type hydrocarbons have been investigated using electron energy-loss spectroscopy (EELS) in transmission. In the undoped materials, the lowest energy excitations are excitons with a relatively high binding energy. These excitons also are rather localized as revealed by their vanishing dispersion. Upon doping, new low energy excitation features appear in the former gaps of the materials under investigation. In K$_3$picene and K$_3$chrysene they are characterized by a negative dispersion while in Ca$_3$picene they are dispersionless.
Transmission electron microscopy, scanning transmission electron tomography, and electron energy loss spectroscopy were used to characterize three-dimensional artificial Si nanostructures called metalattices, focusing on Si metalattices synthesized by high-pressure confined chemical vapor deposition in 30-nm colloidal silica templates with ~7 and ~12 nm meta-atoms and ~2 nm meta-bonds. The meta-atoms closely replicate the shape of the tetrahedral and octahedral interstitial sites of the face-entered cubic colloidal silica template. Composed of either amorphous or nanocrystalline silicon, the metalattice exhibits long-range order and interconnectivity in two-dimensional micrographs and three-dimensional reconstructions. Electron energy loss spectroscopy provides information on local electronic structure. The Si L2,3 core-loss edge is blue-shifted compared to the onset for bulk Si, with the meta-bonds displaying a larger shift (0.55 eV) than the two types of meta-atoms (0.30 and 0.17 eV). Local density of state calculations using an empirical tight binding method are in reasonable agreement.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
