Electrical properties of mercury telluride films

Vacuum deposited HgTe films formed at 120°C were studied for resistivity, activation energy, Hall constant, mobility μ and thermoelectric power α between 78 and 420 K. These films are semiconducting and p-type. Graphs of μ against temperature T showed peaks around 310 K suggesting the predominance of ionized impurity scattering below 310 K and piezoelectric scattering above 310 K. A reasonable agreement between the experimental and calculated values of α was also observed.     

Electrical properties of ZnSe-CdS alloy films

Thin films of ZnSe _x CdS_1–x (t 0.6 m) over the entire range of x, were deposited on glass substrates at two temperatures, T _s (350 and 470 K) by vacuum evaporation. X-ray diffraction studies showed that all the films were polycrystalline in nature. Films prepared at 470 K were nearly stoichiometric. Grain size increased with substrate temperature, T _s. The electrical conductivity and Hall measurements were carried out by d.c. van der Pauw technique. Hall effect studies/hot probe test showed that all the films were of n-type conductivity. Hall mobility increased with T _s. In addition, mobilities increased with temperature in films of all compositions, indicating the dominance of grain-boundary scattering. Grain-boundary potentials were in range 0.03–0.06 eV.     

Electrical properties of thick PZT-based films

We have studied the effect of bismuth oxide additions (2 wt %) on the electrical properties of thick lead zirconate titanate films. The results demonstrate that the addition of bismuth oxide to the starting mixture, followed by grinding in a high-energy vibratory mill, enables the sintering temperature to be lowered to 820–850°C.     

Electrical properties of polycrystalline germanium-metal films

The electron transport properties of crystalline and crystallized Ge-metal (Al, Ga, Ag, Au, Cu and Fe) films were studied as functions of the metal concentration (up to 10 at.%) and temperature (150–500 K). The addition of aluminium and gallium decreases the electrical resistivity and thermoelectric power (TEP). The carrier concentration increases rapidly and there is a gradual decrease in the Hall mobility. Silver affects these transport properties only slightly in crystalline films but large effects are observed in crystallized GeAg films. There is a gradual decrease in the electrical resistivity and TEP of crystalline and crystallized GeAu films. The carrier concentration increases slowly and the Hall mobility shows a maximum. The carrier concentration in crystalline GeCu and GeFe films decreases slowly but shows an increase in the corresponding crystallized films. The Hall mobility in crystalline films decreases but shows a maximum in the crystallized films. In crystalline GeCu films the TEP decreases initially (up to approximately 2 at.% Cu) and then increases. The electron transport properties in these films are explained in terms of the formation of solid solution/segregated ordered phases.     

Electrical properties of AgGaSe2 films

Single phase polycrystalline films of AgGaSe₂ with different thicknesses are prepared on glass substrates by flash evaporation technique, at a substrate temperature of 523 K. The electrical properties of these films such as resistivity. Hall mobility, carrier concentration and activation energy are determined with different thicknesses of the films. The optical absorption in these films is studied in the energy range 1.3-1.9 eV and found to possess a direct band gap with an energy gap of 1.61 eV for a AgGaSe₂ film having thickness 250 nm. The implications are discussed.     

Electrical properties of thin metal zinc films

Thin metal zinc films 40 to 200 nm thick are deposited by thermal evaporation at room temperature onto glass substrates with a deposition rate of 0.2 to 0.7 nm sec^–1. The electrical resistivity is measured as a function of film thickness, deposition rate and annealing temperature. The experimental results show that electrical resistivity decreases as the film thickness, deposition rate and annealing temperature increase, while the temperature coefficient of resistivity increases with the increase in the film thickness. The calculated values of the activation energy for the conduction electrons increases as the film thickness and deposition rate increase. The well known Fuchs-Sondheimer model is applied for zinc films. The theoretically calculated values for the electrical resistivity and the temperature coefficient of resistivity are in good agreement with the experimental results.     

Electrical properties of polycrystalline GaInAs thin films

Polycrystalline Ga_xIn_1 − xAs films with x ranging from 0 to 1 were deposited on glass substrates by molecular-beam deposition at 240 or 350 °C. Room temperature Hall-effect measurements showed that the Ga_xIn_1 − xAs films deposited at either temperature exhibit high electron concentrations in the range of 10¹⁸ cm^− 3 for x ≤ 0.21 while the electron concentration decreases with increasing Ga content for x ≥ 0.29 to be < 10¹⁵ cm^− 3 at x = 0.64. Even at the low deposition temperature of 240 °C, the electron mobility remains > 400 cm²/(V s) at x ~ 0.2 and then decreases with Ga content to be ~ 40 cm²/(V s) at x = 0.64. Temperature-varying Hall-effect measurements in the range of 100-390 K revealed that both the electron concentration and mobility of the samples with x ≤ 0.21 are almost independent of the measurement temperature, while those of the samples with x ≥ 0.30 decrease with decreasing measurement temperature. The concentrations and ionization energies of donor levels were deduced from the temperature dependence of the electron concentration with the non-parabolicity of the conduction band taken into account. The temperature dependences of electron mobility in the samples with x ≥ 0.30 are well explained in terms of thermionic electron emission across the grain-boundary barriers assuming fluctuation in potential barrier height, while the almost temperature-independent high electron mobilities in the samples with x ≤ 0.21 are attributed to the absence of potential barrier at the grain boundaries.     

Electrical properties of films at microwave frequencies

A technique suitable for the measurement of electrical properties of films/sheets at microwave frequencies has been described. Groups of materials are identified for which the absence of any kind of electrodes in these microwave measurements can be utilised with advantage. Results are presented for a variety of materials such as metal films, superionic conductors, semiconductors and insulating polymers.     

Electrical properties of plasma-sprayed yttria-stabilized zirconia films

Yttria-stabilized zirconia films, 100 to 200 m thick, were prepared by plasma spraying. The electrical properties were investigated by complex impedance spectroscopy. The results are compared with those obtained on sintered pellets prepared with the same powders used for spraying and on commercial single crystals. The ionic conductivity and the activation energies of sprayed films and single crystals are found to be very similar, and no grain-boundary effect is observed in the film complex impedance plots. These results are explained by the high density and purity of the sprayed films.     

Electrical and optical properties of phthalocyanine films

Thin films of various phthalocyanines (Pcs) were sublimed onto quartz glass in ultrahigh vacuum. The electrical and optical properties were studied without breaking the ultrahigh vacuum. The dyes were purified by repeated sublimation in vacuum.The conductivity varied with pretreatment (modification) and temperature. Exposure to oxygen, iodine and bromine increased the p-type conductivity by orders of magnitude and lithium doping caused n-type conductivity. Heavy exposure to halogens caused not only broadening of the optical absorption band but also bleaching. Annealing in vacuum removed the electrical and optical effects of doping nearly completely.Field effect studies were used to identify p- and n-type conductivity, to determine the drift mobility and to estimate the trap densities. The field effect and the photoconductivity of p- and n-type films increased by several orders of magnitude with the dark conductivity, i.e. with doping. This correlation is attributed either to traps with a continuous distribution in energy or to trapping by at least two discrete defect levels crossing the Fermi level within the surface-induced accumulation layer. Possible consequences for the sensitivity of semiconductor gas sensors are discussed.     

Electrical properties of ion irradiated polypropylene films

The effect of high-energy (50 MeV) Li³⁺ ion beam irradiation on polypropylene (PP) film has been studied in the fluence range 2.4 × 10¹²−l.5 × 10¹⁴ ions/cm². The a.c. electrical properties of PP films were measured in the frequency range from 0.05– 100 kHz, and at temperature range between 30 and 140°C. This study indicates two peaks at 60°C and 120°C with comparatively high magnitudes. There is an exponential increase in conductivity with log of frequency and the effect is significant at higher fluences. The loss factor (tan δ) vs frequency plot suggests that PP film based capacitors may be useful below 10 kHz. The capacitance is constant over a wide temperature range up to 130°C. FTIR spectra of the PP films before and after irradiation indicate that intensity of C-H stretching vibration at 2900 cm⁻¹ is modified. The presence of many new peaks with the increase of fluence suggests the formation of alkanes and alkynes which might be responsible for the observed changes in the dielectric and electrical properties of PP films.