Carrier loss mechanisms

Principles in Processing Materials. In most practical apphcations of microwave power, the material to be processed is adequately specified in terms of its dielectric permittivity and conductivity. The permittivity is generally taken as complex to reflect loss mechanisms of the dielectric polarization process the conductivity may be specified separately to designate free carriers. Eor simplicity, it is common to lump ah. loss or absorption processes under one constitutive parameter (20) which can be alternatively labeled a conductivity, <7, or an imaginary part of the complex dielectric constant, S, as expressed in the foUowing equations for complex permittivity ... 

Figure 12. Energy diagram of a semiconductor/electrolyte interface showing photogeneration and loss mechanisms (via surface recombination and interfacial charge transfer for minority charge carriers). The surface concentration of minority...

Through virtually all of the filament length, the temperature is constant. But at the ends the temperature must drop almost to the cell body temperature. Heat is transferred to the body through the ends. Like thermal conductivity, this loss is proportional to the difference in temperature between filament and body, but unlike thermal conductivity, the heat transfer does not depend on conductivity of the gas. This amounts to 45 mW for the case cited. For the small-diameter wire and high-conductivity carrier gases used today, this heat loss mechanism can usually be neglected. 

For solar cells, the fill factor FF determines the position of the maximum power point in the 4th I/V quadrant of the illuminated diode and is therefore a quality sign of the photodiode. Besides the increased efficiency, the FF of a photodiode is also important when evaluating the proper function of the diode. High FF values are expected only for diodes with a strict selection principle for the separation of positive and negative carriers. There are several loss mechanisms for photodiodes that can reduce the FF in a photodiode ... 

The other main loss mechanism in these LEDs is from carriers which do not recombine in the i layer, but instead are transported completely through the film. Ideally, the p-type contact should comprise a blocking layer preventing electrons from being collected, but easily injecting holes, and vice versa for the n-type contact. Perhaps when the band discontinuities between the different alloys are better understood, some new and more efficient structure can be designed. 

When the light is switched off, the photoconduction will decay as the carrier population gradually returns to equilibrium. By studying photoconduction kinetics it is often possible to determine the dominant mechanism of carrier loss neutralisation at electrodes, recombination of electrons with holes, or trapping at defects or impurity centres. 

During each of the above-mentioned processes, energy can be lost, resulting in various loss mechanisms. First of all, all photons are not absorbed by the active layer due to limitations of the band gap, as described in the introduction and limited thickness of the active layer (1). Secondly, excitons will decay when created too far from the donor/acceptor interface (2). After the transfer of electron, recombination of the bound electron-hole pair can take place (3) as well as bimolecular recombination (4) of free charge carriers during transport to the electrodes can also occur. 

Fig. 6. Catalyst inhibition mechanisms where ( ) are active catalyst sites the catalyst carrier and the catalytic support (a) masking of catalyst (b) poisoning of catalyst (c) thermal aging of catalyst and (d) attrition of ceramic oxide metal substrate monolith system, which causes the loss of active catalytic material resulting in less catalyst in the reactor unit and eventual loss in performance.

The mechanical strength of the carriers produced in lab scale (Fig. 8) was quantified in terms of attrition loss, side crush strength and drop test strength. An example of the results is given in Table 3 for carriers D and E prepared with... 

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