Charge carriers electrons

Static defects scatter elastically the charge carriers. Electrons do not loose memory of the phase contained in their wave function and thus propagate through the sample in a coherent way. By contrast, electron-phonon or electron-electron collisions are inelastic and generally destroy the phase coherence. The resulting inelastic mean free path, Li , which is the distance that an electron travels between two inelastic collisions, is generally equal to the phase coherence length, the distance that an electron travels before its initial phase is destroyed ... 

The simplest polymer-based EL device consists of a single layer of semiconducting fluorescent polymer, c.g., PPV, sandwiched between two electrodes, one of which has to be transparent (Fig. 1-1). When a voltage or bias is applied to the material, charged carriers (electrons and holes) are injected into the emissive layer and these earners arc mobile under the influence of the high (> 105 V enr1) elec-... 

When the difference A c0 - A 0 becomes positive, the interphase is depleted of majority charge carriers (electrons in this case) forming a... 

The interaction between charge carriers (electrons or holes) and phonons (lattice) may give origin to several phenomena in a crystal, e.g. the production of Cooper pairs. 

The electronic properties of silicon are essential in the understanding of silicon as an electrode material in an electrochemical cell. As in the case of electrolytes, where we have to consider different charged particles with different mobilities, two kinds of charge carriers - electrons and holes - are present in a semiconductor. The energy gap between the conduction band (CB) and the valence band (VB) in silicon is 1.11 eV at RT, which limits the upper operation temperature for silicon devices to about 200 °C. The band gap is indirect this means the transfer of an electron from the top of the VB to the bottom of the CB changes its energy and its momentum. 

LD. ff is in the order of 100 nm. In contrast, the thickness of the accumulation and inversion layers, in which the mobile charge carriers (electrons or holes) are concentrated, is in the order of 5 to 10 nm and is much thinner than the thickness of the depletion layer. 

In the foregoing discussion of this section, we have assumed that the transport current of charge carriers (electrons or holes) in semiconductor electrodes exceeds... 

Equality of i and i on an atomic scale means that a constant exchange of charge carriers (electrons or ions) takes place process the metal-solution interphase. Figure 6.3... 

Some polymeric materials become conductive when illuminated with light. For instance, poly(A -vinylcarbazole) is an insulator in the dark, but when exposed to UV radiation it becomes conductive. Addition of electron acceptors and sensitizing dyes allows the photoconductive response to be extended into the visible and near-IR (NIR) regions. In general, such photoconductivity is dependent on the material s ability to create free-charge carriers, electron holes, through absorption of light, and to move these carriers when a current is applied. 

As shown in Fig. 3.4b, when a semiconductor electrode is illuminated with photons having an energy hv equal to or larger than the semiconductor handgap the result is formation of electronic charge carriers, electrons in the conduction band and holes in the valence band, see equation (3.2.1). 

Electrochemical properties of silicon single crystals, usually cuts of semiconductor wafers, have to be considered under two distinct respects (1) As an electrode, silicon is a source of charge carriers, electrons or positive holes, involved in electrochemical reactions, and whose surface concentration is a determining parameter for the rate of charge transfer. (2) As a chemical element, silicon material is also involved in redox transformations such as electroless deposition, oxide generation, and anodic etching, or corrosion processes. 

FIGURE 4.10 Intrinsic, n-type and p-type semiconductors depicting negative charge carriers (electrons in the conduction band) and positive holes. 

The basis of Butler s reasoning can be seen in the following equation, which refers to the rate of formation of charge carriers (electron, holes) at a distance x from the electrode/solution interface ... 

In the dark, the junction between an extrinsic (doped) semiconductor and a redox electrolyte behaves as a diode because only one type of charge carrier (electrons for n-type and holes for p-type) is available to take part in electron transfer reactions. The potential distribution across the semiconductor/electrolyte interface differs substantially from that across... 

Thermal noise — originates from the thermal agitation of charge carriers (- electrons, -> ions, etc.) in a - resistor. It exists even in the absence of current flow and can be described by the formula (/thermal = (4kB TRAf)1/2. [/thermal is the average amplitude of this noise (also denoted [/rms (or Vrms), see also - root mean square), k is the -> Boltzmann constant, R is the resistance, and A/ is the bandwidth of measurement frequencies. 

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