Conductivity and photoconductivity

The electrical properties (dark conductivity and photoconductivity) are reported to first decrease and then increase upon increasing power [361]. The optical bandgap increases with increasing power, due to the increase of the hydrogen content [63, 82, 362, 363]. However, at very high power levels, microcrystalline silicon is formed [364], which causes the hydrogen content (and, consequently, the bandgap) to decrease. 

Both the dark conductivity and the photoconductivity of the sample deposited at 40 W have been measured. The photoconductivity has been measured under AM 1.5 conditions. The dark conductivity and photoconductivity of the material deposited at 40 W are 1 x 10 and 1.2 x 10 " cm, respectively. These... 

Electrical data are shown in Figure 59 as a function of deposition rate for all frequencies, using the relation between deposition rate and power density as depicted in Figure 54. Both dark conductivity and photoconductivity decrease exponentially with increasing deposition rate. The data in this range of deposition rates can be fitted with (Td = 9 x 10 -exp( —1.5r[Pg.142]

Madan et al. [515] have presented the effect of modulation on the properties of the material (dark conductivity and photoconductivity) and of solar cells. They also observe an increase in deposition rate as a function of modulation frequency (up to 100 kHz) at an excitation frequency of 13.56 MHz, in their PECVD system [159]. The optimum modulation frequency was 68 kHz, which they attribute to constraints in the matching networks. Increasing the deposition rate in cw operation of the plasma by increasing the RF power leads to worse material. Modulation with a frequency larger than 60 kHz results in improved material quality, for material deposited with equal deposition rates. This is also seen in the solar cell properties. The intrinsic a-Si H produced by RF modulation was included in standard p-i-n solar cells, without buffer or graded interface layers. For comparison, solar cells employing layers that were deposited under cw conditions were also made. At a low deposition rate of about 0.2 nm/s, the cw solar cell parameters... 

Our investigation of sNPS showed that the samples prepared by the chemical etching method described above have consistent photoluminescence, conductivity and photoconductivity properties, which have remained unchanged over 5 years. sNPS structure was investigated by scanning electronic microscopy (Fig. 9.1). 

The adsorption of electron acceptors (quinone, chloranil) from the gas phase does not substantially influence the photo-emf of PAC but decreases the dark conductivity and the photoconductivity. The same compounds, however, adsorbed on certain polyacetylenides from solution, increase the photo emf without causing any appreciable change in the spectral distribution. Mercury vapor depresses reversibly the dark conductivity and photoconductivity [276-278]. 

Evaluation of photoreceptor performance includes tests of dark conductivity and photoconductivity. Dark conductivity is determined by charging the surface to the... 

Results obtained from thermal studies can often be compared with observations obtained in parallel investigations of the radiolysis of azides [3], Additional information is also often available from measurements of the conductivities and photoconductivities of the solids, including the influences of various impurities in the crystals. Preirradiation generally increases the rate of subsequent thermal decomposition of azides and such studies can provide information on decomposition... 

K. Park, Radiation-induced zero-resistance state at low magnetic fields and near half-filling of the lowest Landau level, Phys. Rev. B 69, 201301 (2004) M. G. Vavilov et al.. Magnetotransport in a two-dimensional electron gas at large filling factors, Phys. Rev. B 69, 035303 (2004) I. A. Dmitriev et al.. Oscillatory ac conductivity and photoconductivity of a two-dimensional electron gas Quasiclassical transport beyond the Boltzmann equation, Phys. Rev. B 70, 165305 (2004) J. Inarrea and G. Platero, Theoretical approach to microwave-radiation-induced zero-resistance states in 2D electron systems, Phys. Rev. Lett. 94, 016806 (2005). 

With the exception of mass-sensitive electrochemical, light-scattering, conductivity and photoconductivity detectors, all those described in Sections 6.2-6.7 are concentration-sensitive. 

Fig. 4. Variation of dark conductivity and photoconductivity of phthalocyanine with amount of electron acceptor (o-chloranil) added.

The electrical conductivity and photoconductivity of metal polyynes have been studied in some detail.For instance, it has been demonstrated that in the unoxidized state 166 (M = Gu) is an insulator (cr= 10 Scm ) and, upon doping with I2, the conductivity is increased to 10 S cm Polyynes such as 165 (M = Ni, Pd, Pt L = E Bus E = P or As) can either be oxidized with nitric acid or doped with Measurements on undoped films showed low conductivity values of ca. 10 Scm which improved to ca. 10 Scm in the l2-doped samples." The Pt-acetylide pyridine polymers 188 showed conductivities of 2.5 x 10 Scm upon doping with iodine. Quaternization followed by iodine doping gave a similar value (3.4 x 10 S cm ). These values appear to be the highest reported for soluble polymetallaynes. 

The.unusual ability of poly(silanes) to absorb UV light led to the demonstration that Asp5-doped poly(silastyrene) is a semiconductor. The band gap in common silane polymers is about 4eV in contrast to a value of almost 8eV for carbon chains. Conducting and photoconducting properties have been studied. Only holes were found mobile (mobilities of 10 cm V s at 20°C) and it appears hole transport occurs via the a electronic states of the silicon backbone rather than hopping between chain substituents. 

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