Interfaces photo current

Microwave power and its effect on the electrode/electrolyte interface, 439 Microwave region, Hall experiments, 453 Microwave spectroscopy, intensity modulated photo currents, 508 Microwave transients for nano crystalline desensitized cells, 514 Microwave transmission, as a function of magnetic field, 515 Minority carriers... 

Zinc oxide, anodic photo currents for, 470 Zinc oxide layers, spotted, 471 Zinc oxide-electrolyte interfaces, electron transfer rate and its exponential increase at, 512... 

Electrons, generated near the semiconductor-electrolyte interface are unable to stay in this region because of the electric field there which drives them into the bulk of the TiOz crystal, out through the metallic contact, the external circuit (where the photo-current may be measured) and into the catalytically active metal. At the interface of this metal with the electrolyte solution, reaction occurs ... 

In organic cells, however, the steps involved in the generation of photo-current are (1) light absorption, (2) exciton creation, (3) exciton diffusion, (4) exciton dissociation in the bulk or at the surface, (5) field-assisted carrier separation, (6) carrier transport, and (7) carrier delivery to external circuit. Assuming that only the excitons which reach the junction interface produce free carriers, if the blocking contact is illuminated [65],... 

All incident photons which generate electron hole-pairs within the semiconductor bulk and space charge regions must first pass through the semitransparent metal layer. Photons which are reflected at the air-metal interface or are absorbed within the metal do not contribute to the photo current. It is therefore of utmost importance that the transmittance of light into the semiconductor is made as high as possible. 

The photovoltage is esentially determined by the ratio of the photo- and saturation current. Since io oomrs as a pre-exponential factor in Eq. 1 it determines also the dark current. Actually this is the main reason that it limits the photovoltage via Eq. 2, The value of io depends on the mechanism of charge transfer at the interface under forward bias and is normally different for a pn-junction and a metal-semiconductor contact. In the first case electrons are injected into the p-region and holes into the n-region. These minority carriers recombine somewhere in the bulk as illustrated in Fig. 1 c. In such a minority carrier device the forward current is essentially determined... 

Besides the traditional capacitance versus voltage (C/V) measurements, which are mainly used for the characterisation of MOS and EIS capacitances, the scanned light pulse technique (SLPT) was introduced by Engstrom and Aim [13], first for MOS structures. This technique utilises a fight source to illuminate a local area of the MOS structure. Thus, a local photo-effect-induced current can be measured, which only depends on the local properties and energy states of the illuminated region of the MOS structure. In 1988, Hafeman et al. combined this SLPT method with EIS structures to develop the LAPS [14,15]. This sensor is capable of measuring the surface potential of the electrolyte-transducer interface with a lateral resolution. Hence, the surface... 

Actually, the electrochemistry of diamond dates back to the paper [11], A current-voltage curve of crystalline diamond electrode was first taken there, as well as the differential capacitance measured at the diamond/electrolyte solution interface. The diamond electrodes turned out to be photosensitive, and their photo-electrochemical behavior was compared with their semiconductor nature. 

More recently time-resolved techniques have been applied for studying photocarrier dynamics at the semiconductor-liquid interface. One of the main motivations is that such studies can lead to an estimation of the rate at which photo-induced charge carriers can be transferred from the semiconductor to a redox acceptor in the solution. This method is of great interest because rate constants for the transfer of photocarriers cannot be obtained from current-potential curves as in the case of majority carrier transfer (Section 7.3.5). The main aim is a detailed understanding of the carrier dynamics in the presence of surface states. The different recombination and transfer processes can be quantitatively analyzed by time-resolved photoluminescence emitted from the semiconductor following excitation by picosecond laser pulse. Two examples are shown in Fig. 7.60 [82, 83]. 

Although not of primary concern in this review a number of experimenters have developed information on the oxidation rates of amorphous and polycrystalline films of germanium. While there is some disagreement on the role of porosity in the oxidation rate of such films, (17,18) the kinetics of the reaction appear to be strongly dependent on the morphology of the films and the ambient atmospheres to which they are initially exposed. Based on that information it would appear that implant areas should be annealed in situ or at least removed from vacuum to a controlled environment until final surface preparation is affected. This is particularly true of photovoltaic and photo-conductive devices where the uniformity of oxide, interface moisture content, uptake of carbon complexes etc. strongly affect the surface recombination currents and hence the device performance (77). 

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