Injection of electrons

Ion engines are used in sateUites for orientation control. Cesium is vaporized in a vacuum and ionized as it passes through a heated porous tungsten disk, the ions are accelerated by an electric field to about 135 km/s and are neutralized by the injection of electrons and exhausted from the thmster. However, mercury, xenon, and argon-based ion engines are preferred. 

The materials used as the electron and hole injecting electrodes play a crucial role in the overall performance of the device and therefore cannot be neglected even in a brief review of the materials used in OLEDs. The primary requirements for the function of the electrodes is that the work function of the cathode be sufficiently low and that of the anode sufficiently high, to enable good injection of electrons and holes, respectively. In addition, at least one electrode must be sufficiently transparent to permit the exit of light from the organic layer. 

Modification of the top electrode may also be achieved. This was done by adding a small amount of surfactant, such as an ether phosphate or an ether sulfate, to the spin-coal solution of the luminescent polymer [89[. The lipophobic ether chains segregate at the surface of the (predominantly) hydrocarbon polymer, becoming available for complexation with the aluminum cathode which is deposited on top. Thus, the dipole in the surfactant points away from the electrode and lowers its work function to improve the injection of electrons. 

Fig. 5.20 Schematic diagram illustrating the energy levels of different-sized CdSe quantum dots and Ti02 (band positions are not drawn to scale). The injection of electrons from CdSe into Ti02 is influenced by the energy difference between the two conduction bands. [Adapted (in gray scale) from [351]]...

Mehl, W. and Funk, B. (1967) Dark injection of electrons and holes and radiative recombination in anthracene with metallic contacts. Phys. Lett. A, 25, 364-365. 

As for the energy transfer to the subsurface layers of zinc oxide from the singlet oxygen molecules, the transfer should lead to an intn ease in the electrical conductivity of semiconductor either due to ejection of electrons into the conduction band h-om shallow traps [67], or due to the injection of electrons into zinc oxide by excited particles [68]. Effects of this kind were observed in the interaction between a ZnO surface and excited pairs of benzophenone [70], and also in adsorption of singlet oxygen on the surface of ZnO monocrystal in electrolyte [69]. 

In a study of long range ET between aromatic donor (biphenyl) and acceptor molecules separated by steroid spacers [39], pulse radiolysis and electron beam techniques have been used for the injection of electrons (Closs and Miller, 1988 Closs et al., 1989 Liang et al, 1990). Here, the reaction rates (observed by changes in the absorption spectra) pass through a... 

Landauer proposed in 1957 the first mesoscopic theoretical approach to charge transport [176]. Transport is treated as a scattering problem, ignoring initially all inelastic interactions. Phase coherence is assumed to be preserved within the entire conductor. Transport properties, such as the electrical conductance, are intimately related to the transmission probability for an electron to cross the system. Landauer considered the current as a consequence of the injection of electrons at one end of a sample, and the probability of the electrons reaching the other end. The total conductance is determined by the sum of all current-carrying eigenmodes and their transmission probability, which leads to the Landauer formula of a ID system ... 

Fig. 9.2. Schematic setup for the external injection of electrons from a LINAC into a laser wakefield...

M. Jang, S. Song, and H. Shim, Efficient green light-emitting polymer by balanced injection of electron and holes new electron accepting perfluorinated substituent, Polymer, 41 5675-5679, 2000. 

Microbial response to injection of electron acceptors and nutrients may be conducted. 

Electroless deposition is the reduction of a metal ion without an external injection of electrons. This occurs when the redox potential is higher than that of the substrate or... 

Figure 4. Injection of electron acceptors into a contaminant plume.

Reactive metals are of interest for two primary reasons (1) reaction with the uppermost part of the SAM which can drive uniform nucleation with no penetration and (2) for electropositive metals, injection of electrons into the SAM to create a favorable dipole at the metal/SAM interface for device operation. With respect to the first, as opposed to the results with non-reactive metal deposition, some reports of reactive metal deposition appear to show prevention of metal penetration with the avoidance of short-circuits across the M junction. In general, serious concerns remain that some of metal atoms react destructively with the SAM backbone to produce inorganic species, e.g., carbides and oxides in the case of aggressive metals such as titanium. 

Fig. 118a. Schematic of the electron injection process at a highly porous H02 electrode surface (only a patchy and fractured pyrite layer can be expected on the highly porous Ti02 layer), b Surface TiOj/FeSj energy diagram at pH = 1, indicating the injection of electrons from the valence band of FeS2 into the conduction band of HO2, and the reaction of holes with the redox system [714]...

The details of die operating principles of the dye-sensitized solar cell are given in Figure. 3. The photoexcitation of the metal-to-ligand charge transfer of the adsorbed sensitizer [Eq. (1)] leads to injection of electrons into the conduction band of the oxide [Eq. (2)]. The oxidized dye is subsequently reduced by electron donation from an electrolyte containing the iodide/triiodide redox system [Eq. 

Injection of electron spins is preferable from the application point of view as electrons usually exhibit longer spin lifetime. Spin-injection experiments using n-type II-VI DMS in the magnetic field were performed by Fiederling et al. (1999) and Jonker et al. (2000). An appealing scheme for electrical electron spin injection from a ferromagnetic material... 

As mentioned, the photocatalytic activation of Ti02 requires UV irradiation, and hence the semiconductor performance in the solar spectrum is inefficient. A solution to switch the photocatalytic activity to the visible spectral region was described by covalent attachment of an eosin dye monolayer to the semiconductor oxide particles of a Pd-Ti02 catalyst.168 The improved photocatalytic activities, specifically, the efficient formation of formate, are attributed to the effective injection of electrons from the excited dye into the semiconductor conduction band. 

A number of other investigations of the electrical properties of lipid mono- and multilayers were published recently. It is obvious from studies of the conductivity of thin Langmuir films that the electrical properties of metal-organic layer-metal structures can be described by well known concepts from solid state physics, like Schottky injection of electrons from the metal into the lipid film (45, 46, 47). Measurements of dielectric losses in calcium stearate and behenate indicate the presence of movements of dipoles in the organic molecules, and loss peaks connected with the amorphous and crystalline parts of the layers were identified (48). 

---