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Optical and dielectric dispersion parameters for butyl rubber–general purpose furnace carbon black (IIR-GPF CB) composites with various carbon black (CB) concentrations were determined using ultraviolet transmittance spectra. X-ray diffraction (XRD) for the composite samples was measured in the 2θ range from 5° to 50°. There was a slight increase in the XRD peak intensity by increasing CB content indicating some significant changes in the composite structure. Some structural parameters were calculated for the XRD fundamental peak. The crystallite size increased significantly with the increase in carbon black concentration. This suggested a tendency of the polymer toward a more crystal state. Analysis of refractive index dispersion was carried out using Wemple–DiDomenico single effective oscillator model. The energy of effective single oscillator ( $$E_{\text{o}}$$ ) and the dispersion energy ( $$E_{\text{d}}$$ ) were estimated for the composites of different CB loadings. Accordingly, the moments of optical spectra, static and high-frequency dielectric constants were calculated. The variation of the real part $$\varepsilon_{1}$$ and imaginary part $$\varepsilon_{2}$$ of the complex dielectric function with the incident photon wavelength was investigated. The recorded values of $$\varepsilon_{1}$$ were greater than the values of $$\varepsilon_{2}$$ . The dielectric energy loss was specified by means of three important parameters: volume energy loss function, surface energy loss function and dielectric loss factor ( $$\tan \delta$$ ). The dielectric relaxation time $$\tau$$ and plasma frequency were studied as a function of incident photon wavelength for different composite samples. There was a great dependence of $$\tau$$ on the wavelength and amount of the carbon black in the composite.

PM-355 polymeric solid state nuclear track detectors were studied. Samples were irradiated with alpha particles before and after exposure to sunlight under various seasonal conditions. Track formation and optical characteristics of chemically etched samples were investigated. X-ray diffraction (XRD) analysis showed that the dominant structure of the PM-355 detectors is of an amorphous nature with some degree of crystallinity. Micro strain, distortion density and distortion parameter were calculated from the XRD data, and indicate that the structure was modified after alpha irradiation and solar exposure. There was a tendency in the structure towards crystallinity. Some optical properties of PM-355 detectors were studied using Ultraviolet–Visible absorption spectroscopy. The absorption edge was detectable in all samples. The direct band gap decreased first and then subsequently increased again. The fluorescence spectra of alpha irradiated and solar exposed PM-355 polymer detectors after chemical etching showed three dominant peaks at wavelengths 327, 418 and 465 nm, respectively. The changes in the optical properties can be used to detect the effect of alpha and ultraviolet irradiations. The variation of the optical band gap, fluorescence spectra and/or track diameters can be used as a detection of nuclear radiation.

Electrical properties of butyl rubber filled with General Purpose Furnace (GPF) carbon black were studied. The carbon black concentration (X) in the compound was X = 40, 60, 70, 80, and 100 parts by weight per hundred parts by weight of rubber (phr). The corresponding volume fractions of GPF carbon black were 0.447 ± 0.022, 0.548 ± 0.027, 0.586 ± 0.029, 0.618 ± 0.031 and 0.669 ± 0.034, respectively. The concentration dependence of conductivity ( $$ \sigma $$ ) at constant temperature showed that $$ \sigma $$ follows a percolation theory; $$ \sigma \propto \left( {X - X_{o} } \right)^{\gamma } $$ , where X o is the concentration at percolation threshold. The exponent $$ \gamma $$ was found as 6.6 (at room temperature 30°C). This value agrees with other experimental values obtained by many authors for different rubber-carbon black systems. Electron tunneling between the aggregates, which are dispersed in the insulator rubber, was mainly the conduction process proposed at constant temperature in the butyl-GPF carbon black composites. Temperature dependence of conductivity was investigated in the temperature range from 30°C up to 120°C. All samples exhibit negative temperature coefficients of conductivity (NTCC). The values obtained are − 0.130°C−1, − 0.019°C−1, − 0.0082°C−1, − 0.0094°C−1, and − 0.072°C−1 for carbon black concentrations of 40 phr, 60 phr, 70 phr, 80 phr, and 100 phr, respectively. The samples of concentrations 40 phr and 60 phr have also positive temperature coefficients of conductivity (PTCC) of values + 0.031 and + 0.013, respectively. Electrical conduction at different temperatures showed various mechanisms depending on the carbon black concentration and/or the interval of temperature. The hopping conduction mechanism was noticed at the lower temperature region while carrier thermal activation mechanisms were recorded at the higher temperature range.

Pre- and postalpha-exposed PM-355 detectors were irradiated using UV laser with different number of pulses (100, 150, 200, 300, and 400). UV laser beam energy of 20mJ per pulse with a pulse width of 9ns was incident on an area of 19.6mm2 of the samples. XRD spectra indicated that for both reference and UV-irradiated samples, the structure is amorphous, but the crystallite size increases upon UV irradiation. The same results were obtained from SEM analysis. Optical properties of PM-355 polymeric solid-state nuclear track detectors were also investigated. Absorbance measurements for all PM-355 samples in the range of 200-400nm showed that the absorption edge had a blue shift up to a certain value, and then, it had an oscillating behavior. Photoluminescence spectra of PM-355 at 250nm revealed a decrease in the broadband peak intensity as a function of the number of UV pulses, while the wavelengths corresponding to the peaks had random shifts.

The effect of alpha irradiation before and after solar exposed PM-355 polymeric SSNTDs films was investigated. The absorption spectra for both non-irradiated and irradiated samples at different solar exposure time in different months showed a shift in the absorption edge towards lower wavelengths as the solar exposure time increases. This is probably ascribed to the presence of conjugate bonds. The fluorescence spectra indicated three distinguished peaks at approximately 330, 415 and 465 nm respectively. The first peak is attributed to the band gap while the other two peaks due to a probable formation of solid defects. The structure analysis using X-ray diffraction (XRD) proved the partial crystalline nature of the polymer with dominant amorphous phase. There was a slight increase in the XRD peak intensity for the sample irradiated by alpha particles indicating that the polymeric detector structure becomes more crystalline with a change in the crystallite size.

Optical properties of super-grade PM-355 polymer films were studied after solar irradiation with different durations of solar exposure in different months. Results of X-ray diffraction (XRD) analysis showed that a large and wide peak occurred at an angle of 2θ ≈ 20.8° in the solar-exposed samples. The phase crystallinity showed the amorphous nature of the PM-355 polymer sheets. The absorption spectra of the solar-exposed samples indicated that the absorption edge was randomly shifted to longer wavelengths. This is probably due to some structural changes produced by the effect of solar irradiation. Fluorescence spectra of the detectors before and after solar irradiation have three prominent peaks, P1, P2, and P3 at approximately 350, 420, and 470 nm, respectively. The peak P1 could be attributed to the band gap and it was shifted randomly with solar exposure time. The peaks P2 and P3 may be ascribed to some defects and cluster of atoms or molecules formed in the PM-355 polymer.

The electric field dependence of the electron mobility in bulk wurtzite zinc oxide (ZnO) material is studied. The low-field electron mobility is calculated as a function of doping concentration and lattice temperature. The results show that above nearly 50 K the electrical conduction is governed by activation through the bulk material and the conduction is then influenced by both lattice and impurity scattering mechanisms. The high-field characteristics are also considered. The transition between the low-field and high-field regions is specified. The negative differential mobility for bulk ZnO at room temperature is observed at electric fields above 280 kV/cm.

The electron mobility of zincblende (ZB) and wurtzite (WZ) structures of n-type GaN is investigated as a function of both temperature and donor concentration. Numerical calculations of the mobility are carried out in a temperature range from 10 K up to 400 K and donor doping concentrations from 10 19 m -3 to 10 27 m -3 . Elastic types of scattering mechanisms are considered. These types include ionized impurity scattering, neutral impurity scattering, deformation potential acoustic phonons scattering and piezoelectric potential scattering. The electron drift mobility versus temperature shows peak behavior for both zincblende and wurtzite GaN structures. Below approximately 120/140 K (for ZB and WZ GaN respectively), the mobility increases when the temperature is increased. In this temperature range, the ionized impurity scattering is assumed to be the dominant scattering mechanism. Above 120/140 K, the mobility is lowered down by raising the temperature. In this regime, the lattice scattering is considered to be the dominant mechanism. The variation of the electron drift mobility with donor concentration at room temperature shows a continuous decrease with the increase of impurity doping concentration. This is probably due to Coulomb scattering present particularly at low temperatures.

Dielectric measurements were carried out on moderately doped n-InP at low temperatures down to 10 K and at frequencies in the range of 120-105 Hz. The low-temperature asymptotic value of the relative dielectric constant (\( \varepsilon_{r}\)) was found to be greater than the host crystal value. The excess of \( \varepsilon_{r}\) above the host crystal value is attributed to the contribution of impurities. This contribution is originated from an overlap between adjacent wave functions of the impurities. A comparison was made with the theoretical approach taking into account the effect of such overlap and a good agreement was obtained.

ZnTe layers have been grown on a (111) oriented CdTe single crystal substrate by vacuum thermal evaporation technique. The growth temperature was 180 °C at a base pressure of 10 − 4 N/m 2 . The as-grown samples were investigated by X-ray diffraction. The pattern indicated a highly oriented crystallographic growth of ZnTe (111) layer on CdTe (111) substrate. The current–voltage characteristics in both forward and reverse biasing were carried out in the temperature range from 300 down to 200 K. The dark forward current curves were definitely of the diode type in the forward direction. This behavior can be understood as the barrier at the interface limits forward and reverse carrier flow across the junction, where the built-in potential could be developed. Series resistance due to the neutral region was estimated at approximately 320 Ω and the activation energy of the carriers was calculated and found to be 0.11 ± 0.03 eV. The reverse current shows negative resistance behavior at low voltage range.

Epitaxial layers of ZnTe have been grown on a (111) oriented CdTe single crystal substrate by thermal evaporation technique at 180°C and a pressure of 10-6 Torr. X-ray diffraction pattern indicated a highly oriented crystallographic growth of ZnTe (111) layer on CdTe (111) substrate. C–V measurements are carried out at frequencies of 10 kHz and 100 kHz. 1/C2 versus the forward bias voltage gave a straight line in the voltage range from 1 to 3 V. Extrapolation of 1/C2 → 0 led to an estimated value of the built-in potential of about 0.58 V. The calculated charge carrier concentration in the lightly doped over-grown layer, ZnTe , has been found to be p = 1.7 × 1016 cm -3. It was found that energy band diagram constructed according to the electron affinity model is not the adequate one to explain the capacitance–voltage behavior. Therefore, one should take into account the effect of interface states on the energy band diagram. The interface states density has been estimated to be ~1013 cm -2 for (111) ZnTe /(111) CdTe heterojunction system. The interface states were identified as hole traps for the ZnTe / CdTe heterojunction. Accordingly, a band bending downward both materials, and a depletion zone in both of them are expected.

Optical characteristics of butyl rubber/GPF carbon black (BR/GPFCB) composites with carbon black (CB) concentrations 40, 60, 80 and 100 phr (part per hundred part of rubber) were investigated. The structure of the BR/GPFCB composites was analyzed by x-ray diffraction (XRD). All samples with various CB showed diffraction peaks around 2θ = 14°, 25° and 44° which correspond to interlayer spacing of 6.23 A, 3.62 A and 2.10 A respectively. The peaks were shifted toward larger 2θ angles with increasing CB concentration, indicating a decrease in layer spacing. Ultraviolet and visible (UV–vis) absorbance spectra in the range from 200 nm to 800 nm of the BR/GPFCB composites were studied. In the UV range of the spectra, an absorption edge was recorded. Direct and indirect optical band gaps for the composites were evaluated. The direct band gap values were found-as shown to be slightly greater than that of the indirect ones. The reflectance spectra in the UV optical range were demonstrated. Most of the incident UV light was absorbed inside the composites while a very small fraction was reflected and transmitted. This was attributed to the high UV absorption property of the CB filler. The refractive index of the composite was calculated from the reflectance data. The dependence of the real and imaginary parts of the complex dielectric constant on the incident light energy was characterized. The dielectric loss factor was found to decrease with increasing incident photon energy until approximately 5.5 eV (around the absorption edge) and then it increased rapidly.

Temperature and concentration dependence of electrical resistance of butyl rubber filled with GPF carbon black was carried out. Current–voltage (I–V) characteristics at room-temperature were also investigated. The I–V characteristics show that the behavior is linear at small voltages up to approximately 0.15 V and currents up to 0.05 mA indicating that the conduction mechanism was probably due to electron tunneling from the end of conductive path to the other one under the action of the applied electric field. At higher voltages, a nonlinear behavior was noticed. The nonlinearity was attributed to the joule heating effects. Electrical resistance of the butyl/GPF composites was measured as a function of temperature during heating and cooling cycles from 300 K and upward to a specific temperature. When the specimens were heated up, the resistance was observed to increase continuously with the rise of temperature. However, when the samples were cooled down, the resistance was observed to decrease following a different path. The presence of conduction hysteresis behavior in the resistance–temperature curves during the heating and cooling cycles was then verified. The electrical conduction of the composite system is supposed to follow an activation conduction mechanism. Activation energy was calculated at different filler concentrations for both the heating and cooling processes.

Direct analytical calculations of the static dielectric permittivity-dependent electron mobility due to different elastic scattering mechanisms for n-type InSb were carried out. The calculated static dielectric permittivity increases by increasing of donor concentration. The temperature dependence of the electron mobility from 10 K up to 300 K has been demonstrated. Generally, the electron mobility shows peak behavior in this range of temperatures. The direct correlation between the electron mobility and the static dielectric permittivity at 300 K was investigated. The dependence of the electron mobility on donor concentration was discussed both when the static dielectric permittivity is assumed to be varying and when it is assumed to be a constant. The difference in behavior was noticed particularly at high donor concentrations.

The growth of high-mobility modulation-doped Si/SiGe heterostructures on silicon-on-insulator (SOI) substrates is demonstrated. The structural and electrical properties of the samples are comparable with those of similar samples grown on standard Si substrates. Electron mobilities as high as 2800 cm 2 V −1 s −1 at room temperature and 8.2×10 4 cm 2 V −1 s −1 at 4 K are obtained.

Hole mobility and effective Hall factor for p -type GaSb were studied theoretically as a function of temperature from 10K up to 300K. The mobility calculations were based on the relaxation time approximation taking into account elastic scattering mechanisms including lattice and ionized-impurity types. The results showed that the ionized-impurity scattering is the dominant mechanism at low-temperature range while lattice scattering may be the dominant one at higher temperatures. The effective Hall factor was investigated using the two-band model assuming parabolic valence bands. Hall parameters of p -GaSb were analyzed by assuming that the bands of heavy and light holes are decoupled. If the impurity scattering exceeds all other scattering processes, the effective Hall factor may tend to unity but when the lattice scattering process dominates, this approximation is not valid.

The growth of high-mobility modulation-doped Si/SiGe heterostructures on silicon-on-insulator substrates is demonstrated. The structural and electrical properties of the samples are reported to be comparable with those of similar samples grown on standard Si substrates. Electron mobilities as high as 2900 cm2/Vs at room temperature and 8.2×104 cm2/Vs at 4.2 K were obtained.

We report on the growth and characterization of high‐mobility 2DEGs on tensile strained Si grown on cubic SiGe alloy on SOI substrates. The electrical properties were investigated in the 4.2–300 K temperature range as a function of growth conditions and sample structure. Hall mobilities as high as 82000 cm2/V.s at T=4.2 K were obtained in the best 2DEGs on SOI. We found that the main mechanism limiting the mobility at low temperature is the ionized impurity scattering.

In this paper, AC measurements on lightly doped n- InP were carried out as a function of temperature down to about 16 K and at frequencies in the range from 120 Hz up to 105 Hz. The AC conductivity at low temperatures is of a single hopping nature following the universal law; σ(ω) ~ ωs, where the exponent, s, is temperature-independent. At relatively high temperatures (but still below the room temperature) the AC conductivity is of a multiple hopping nature.