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© 1996 - Elsevier Science S.A. International Workshop on Beam Injection Assessment of Defects in Semiconductors (4. 1996. El Escorial, España). This research has been partially supported by the Cooperation Programme “Azione Integrata” between Italy and Spain and by DGICYT (Project PB 93-1256). The authors are indebted to the Japan Energy Corporation for the undoped and Cl doped samples., We have investigated deep levels in semiconducting and semi-insulating II-VI compounds, namely undoped CdTe, CdTe:Cl and CdZnTe, in order to understand their role in the compensation mechanisms. To this aim Lye have utilized both junction spectroscopy techniques and cathodoluminescence (CL) spectroscopy. As junction spectroscopy methods we have utilized deep level transient spectroscopy (DLTS), photo-induced current transient spectroscopy (PICTS) and photo-DLTS (P-DLTS). By exploiting the peculiarities of these experimental methods, joined by CL characterization, we were able to gain further insight into the revealed traps properties, such as the trap nature (donor/acceptor). We have focused our attention on the deep levels that have been suggested to be involved in the compensation process, such as centre A., DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

This research has been partially supported by the Cooperation Programme ‘‘Azione Integrata’’ between Italy and Spain and by DGICYT (Project PB 93-1256). The authors are indebted to the Japan Energy Corporation for Corporation for the undoped and doped samples., We have investigated the electrical and optical properties of the deep levels responsible for the 1.4-1.5 eV luminescence band usually observed in II-VI compounds. We compared the energy levels found by cathodoluminescence and junction spectroscopy methods for semi-insulating (CdTe:Cl and Cd_(0.8)Zn_(0.2)Te) and semiconducting samples (undoped CdTe). The techniques utilized were deep level transient spectroscopy (DLTS) on semiconducting samples and photoinduced current transient spectroscopy and photo-DLTS on high resistivity materials. These last two techniques are complementary and allow the determination of the trap character (donor/acceptor). Three acceptor levels are seen in the electrical transient data at E(upsilon)+0.12, 0.14, and 0.16 eV with hole capture cross sections of 2x10^(-16), 1x10(-16), and 4X10^(-17) cm(2), respectively. The lowest level is seen only in Cl doped material corroborating the literature optical and electron spin resonance identification of a level at E_(upsilon)+0.12 eV as being a V_Cd+Cl_Te, donor-acceptor pair center. All three levels may be present in the 1.4 eV luminescence band., DGICYT (Spain), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1997 The American Physical Society. This research was partially supported by the Cooperation Programme ‘‘Azione Integrata’’ between Italy and Spain and by DGICYT (Project No. PB 93-1256). The authors are indebted to Japan Energy Corporation for the undoped and Cl-doped samples., We study, by cathodoluminescence and junction spectroscopy methods, the deep traps located near midgap in semiconducting and semi-insulating II-VI compounds, namely, undoped CdTe, CdTe:Cl, and Cd0.8Zn0.2Te. In order to understand the role such deep levels play in the control of the electrical properties of the material, it appears necessary to determine their character, donor, or acceptor, in addition to their activation energy and capture cross section. Photoinduced-current transient spectroscopy and photo deep-level transient spectroscopy are used to investigate the semi-insulating (SI) samples, and a comparison of the complementary results obtained allows us to identify an acceptor trap, labeled H, and an electron trap, labeled E. Level H is common to all investigated compounds, while E is present only in CdTe:Cl samples. This provides clear experimental evidence of the presence of a deep trap in CdTe:Cl, which could be a good candidate for the deep donor level needed to explain the compensation process of SI CdTe:Cl., DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1994 American institute of Physics. This work was supported by the Comision Interministerial de Ciencia y Tecnologia (Project No. PB90-1017) and by the Italian MURST. The authors wish to thank Wacker-Chemitronic (Dr. K. L6hnert) for providing the samples., The distribution in liquid-encapsulated-Czochralski (LEC) GaAs:Te wafers of point and complex defects has been investigated together with their influence on the minority-carrier diffusion length L. Three wafers with different Te-doping concentration (2.2 X 10(17), 4.5 X 10(17), and 1.5 X 10(18) cm-3) have been studied by means of the electron-beam-induced-current (EBIC) mode of scanning electron microscopy and of the surface photovoltage (SPV) method. The morphology and electrical activity of the defects observed across each wafer have been correlated to the formation and distribution of deep electronic levels, which are significantly affected by the tellurium concentration. The diffusion length has been found to be mainly controlled by deep levels associated with dislocations. EBIC localized measurements of L and of the net ionized free-carrier concentration provide evidence for the influence of Te concentration on impurity segregation at complex defects., Comision Interministerial de Ciencia y Tecnologia, Italian MURST, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 The American Physical Society. This research has been partially supported by the coperation Programme ‘‘Azione Integrata’’ between Italy and Spain and by DGICYT (Project No. PB93-1256).The authors are indebted to Professor F. Casali for providing thesamples., Deep levels in Cd_(1-x)Zn_xTe have not yet been fully characterized and understood, even though this material is very promising for medical and optoelectronic applications. We have investigated p-type semi-insulating Cd_(0.8)Zn_(0.2)Te with cathodoluminescence (CL) and photoinduced current transient spectroscopy (PICTS) methods. PICTS analyses allow detection of deep levels which are not revealed by other current spectroscopy techniques generally used, as they permit scanning of a wider region of the energy gap. Five levels have been detected (0.16, 0.25, 0.57, 0.78, and 1.1 eV) and, by combining the results obtained with the above-mentioned CL techniques, we were able to advance hypotheses on the character (donor or acceptor) and origin of some of these levels. The key role prayed by the 0.78-eV level in controlling the carrier transport properties has also been confirmed., DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1995 American Institute of Physics. This research has been partially supported by the Cooperation Programme “Azione Integrata” between Italy and Spain, We have investigated highly doped GaAs:Te at different doping concentrations (>10(17) cm(-3)) to assess the presence of the EL2 trap. We have utilized both capacitance and current transient spectroscopy techniques. The crucial parameter for the detection of EL2 is the relative position of the electron quasi-Fermi level in the depletion region. The observed shift of the EL2 apparent activation energy with increasing doping concentration is also discussed., Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

(C) 1998 American Institute of Physics., The deep levels present in semiconducting CdTe and semi-insulating CdTe:Cl and Cd0.8Zn0.2Te have been investigated by means of cathodoluminescence, deep level transient spectroscopy (DLTS), photo-induced current transient spectroscopy, and photo-DLTS. The latter two methods, which can be applied to semi-insulating materials, allow to characterize the deep traps located up to midgap and can determine whether they are hole or electron traps. We have identified 12 different traps, some common to all the investigated samples, some peculiar to one of them. A comparison of the results obtained from the various materials is given and the status of defect models is reviewed., DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Monitoring of bioelectric signals in peripheral sympathetic nerves of small animal models is crucial to gain understanding of how the autonomic nervous system controls specific body functions related to disease states. Advances in minimally-invasive electrodes for such recordings in chronic conditions rely on electrode materials that show low-impedance ionic/electronic interfaces and elastic mechanical properties compliant with the soft and fragile nerve strands. Here we report a highly stretchable low-impedance electrode realized by microcracked gold films as metallic conductors covered with stretchable conducting polymer composite to facilitate ion-to-electron exchange. The conducting polymer composite based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) obtains its adhesive, low-impedance properties by controlling thickness, plasticizer content and deposition conditions. Atomic Force Microscopy measurements under strain show that the optimized conducting polymer coating is compliant with the micro-crack mechanics of the underlying Au-layer, necessary to absorb the tensile deformation when the electrodes are stretched. We demonstrate functionality of the stretchable electrodes by performing high quality recordings of renal sympathetic nerve activity under chronic conditions in rats.