A new experimental procedure combining usual isothermal DC charging and discharging with non-isothermal current measurements has been recently proposed. It is mainly suitable for very high insulating polymers and it was successfully applied to the study of space charge trapping and transport in low-density polyethylene. The analysis of the isothermal currents revealed the presence of different traps whose characteristic (de)trapping times can be deduced. The isothermal procedures allowed the selective charging of the sample. By choosing the charging field and the ratio of charge/discharge times, non-isothermal analysis permitted the differentiation of three or four peaks (at approximate to50degreesC, approximate to65degreesC, approximate to70degreesC and approximate to85degreesC) associated with charge detrapping from surface or near-surface (<20 mum) traps. These traps have activation energies between 0.21 and 1.54 eV. The mobility at 30degreesC is around 5 x 10(-16) m(2) V-1 s(-1). Samples had to be conditioned before each experiment in order to obtain reproducible results.

A new experimental procedure combining usual isothermal DC charging and discharging with non-isothermal current measurements has been recently proposed. It is mainly suitable for very high insulating polymers and it was successfully applied to the study of space charge trapping and transport in low-density polyethylene. The analysis of the isothermal currents revealed the presence of different traps whose characteristic (de)trapping times can be deduced. The isothermal procedures allowed the selective charging of the sample. By choosing the charging field and the ratio of charge/discharge times, non-isothermal analysis permitted the differentiation of three or four peaks (at approximate to50degreesC, approximate to65degreesC, approximate to70degreesC and approximate to85degreesC) associated with charge detrapping from surface or near-surface (<20 mum) traps. These traps have activation energies between 0.21 and 1.54 eV. The mobility at 30degreesC is around 5 x 10(-16) m(2) V-1 s(-1). Samples had to be conditioned before each experiment in order to obtain reproducible results.

In this work we studied the influence of the dopant elements and concentration on the properties of ZnO thin film deposited by spray pyrolysis. The results show that the doping affects the thin films properties mainly the electrical ones, function of dopant concentration and nature. The most important changes were observed for films doped with 1at% of indium which exhibit a resistivity of 1.9 × 10-1 Ωcm associated with a transmitance of 90%. After the annealing treatment, the resistivity of the film decreases to 5.9 × 10-3 Ωcm without significative changes in the optical properties. The films were also used to produce amorphous silicon solar cells where the best results were obtained for ZnO:In. © 2002 Elsevier Science Ltd. All rights reserved.

In this work, we report the electro-optical properties exhibited by ZnO:A1 thin films deposited by r.f. magnetron sputtering. The effect of the deposition parameters on the properties of the films were studied with the aim to determine the most suitable deposition conditions to obtain ZnO:Al thin films with a low resistivity and high transmittance, characteristics required for applications on optoelectronic devices. After annealing, the ZnO:Al thin films present a low resistivity (6.25 × 10-3 Ωcm) and a high transmittance (90%) when produced with a deposition pressure of 1.6 × 10-2 mbar and r.f. power of 150W. © 2002 Elsevier Science Ltd. All rights reserved.

The most common techniques used to produce ZnO thin films are the spray pyrolysis and the magnetron sputtering techniques, low and high cost processes respectively. The aim of this work is to compare the properties of the films produced by these two techniques. The predominant difference observed was on the morphological properties. The films produced by spray pyrolysis have a rougher surface than the ones obtained by sputtering. Also the effect of the thermal annealing treatment is much more prononnced for the ZnO thin films produced by spray pyrolysis. After heat treatment films exhibit similar electrical properties and their application to optoelectronic devices is demonstrated.