Home About us Contact
|
Home About us Contact | ||
|
|
||
High Resistivity (high + resistivity)
Selected AbstractsSchottky contacts to hydrogen doped ZnOPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008R. Schifano Abstract High resistivity (,1 k, cm) hydrothermally grown single crystal ZnO wafers were modified by hydrogen implantation. The implantation has been performed with multiple energies in order to form a box-like profile with a depth of 4 ,m and two different concentrations of 8 × 1017 H/cm3 and 1.5 × 1018 H/ cm3. A subsequent annealing at 200 °C for 30 min in N2 resulted in the formation of a highly conductive layer. Pd con- tacts deposited on the implanted side showed rectifying behaviour by up to three orders of magnitude. However by capacitance vs. voltage (C ,V) technique a carrier concentration significantly lower than the one expected according to the implanted H content was measured suggesting the presence of a high density of compensating centers and/or an incomplete activation of H as a donor. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Using DC resistivity tomography to detect and characterize mountain permafrostGEOPHYSICAL PROSPECTING, Issue 4 2003Christian Hauck ABSTRACT Direct-current (DC) resistivity tomography has been applied to different mountain permafrost regions. Despite problems with the very high resistivities of the frozen material, plausible results were obtained. Inversions with synthetic data revealed that an appropriate choice of regularization constraints was important, and that a joint analysis of several tomograms computed with different constraints was required to judge the reliability of individual features. The theoretical results were verified with three field experiments conducted in the Swiss and the Italian Alps. At the first site, near Zermatt, Switzerland, the location and the approximate lateral and vertical extent of an ice core within a moraine could be delineated. On the Murtel rock glacier, eastern Swiss Alps, a steeply dipping boundary at its frontal part was observed, and extremely high resistivities of several M, indicated a high ice content. The base of the rock glacier remained unresolved by the DC resistivity measurements, but it could be constrained with transient EM soundings. On another rock glacier near the Stelvio Pass, eastern Italian Alps, DC resistivity tomography allowed delineation of the rock glacier base, and the only moderately high resistivities within the rock glacier body indicated that the ice content must be lower compared with the Murtel rock glacier. [source] Inversion and interpretation of two-dimensional geoelectrical measurements for detecting permafrost in mountainous regionsPERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2003Christian Hauck Abstract The use of tomographic geoelectrical measurements for the detection of ground ice occurrences in mountainous regions is evaluated. Because isolated ground ice occurrences in a warming climate may be subject to rapid thawing, they present a future hazard in the context of thawing-permafrost-induced landslides and rockfalls. Isolated permafrost occurrences are difficult to detect with commonly used one-dimensional sounding techniques, as plane-layer approximations for the inversion are often invalid. Therefore, recently developed two-dimensional tomographic inversion schemes are used to yield realistic near-surface geological models. The method is applied to various types of permafrost occurrences in the European Alps. The influence of topography, measurement geometry and different inversion parameters are discussed. In addition, complimentary seismic survey results are used to exclude the possibility of air-filled cavities, which exhibit similarly high resistivities as ground ice occurrences. The results show a large variety of influencing parameters which have to be considered in resistivity inversion and interpretation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Investigation of semi-insulating InP co-doped with Ti and various acceptors for use in X-ray detectionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005K. Zdansky Abstract Semi-insulating InP single crystals co-doped with Zn and Ti and co-doped with Ti and Mn were grown by Czochralski technique. Wafers of these crystals were annealed for a long time at a high temperature and cooled slowly. The samples were characterized by temperature dependent resistivity and Hall coefficient measurements. The binding energies of Ti in semi-insulating InP co-doped with Ti and Zn and co-doped with Ti and Mn were found to differ which shows that Ti may occupy different sites in InP. The curves of Hall coefficient vs. reciprocal temperature deviate from straight lines at low temperatures due to electron and hole mixed conductance. The value of resistivity of the annealed semi-insulating InP co-doped with Ti and Mn reaches high resistivity at a reduced temperature easily achievable by thermo-electric devices which could make this material useable in X-ray detection. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Construction of a polymer skeleton that is cut in half by ionizing radiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005Takashi Shimizu Abstract Polystyrene with a benzyl ester of carboxylic acid at the center of a polymer skeleton was synthesized by living radical polymerization. The initiator used had two functional groups for 2,2,6,6-tetramethylpiperidinoxyl (TEMPO)-mediated living radical polymerization on the benzyl and the carboxylic sides of the benzyl ester. Introduction of the benzyl ester changed the polystyrene from a crosslink type to a scission type polymer on ,-irradiation. Irradiation of the polymer resulted in a binary change of the molecular weight because of the dissociative capture of secondary electrons by the benzyl ester, as: The binary change of the molecular weight suggests that the polymer can be used as a new type of radiation resist with high sensitivity and spatial resolution to ionizing and high resistivity to plasma etching. The number of scissions per 100 eV radiation energy absorbed was 0.29, which was about one fourth of the yield of secondary electrons. The low efficiency was because of the recombination of polymer radicals generated by the dissociative electron attachment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1068,1075, 2005 [source] Physical and Electrical Properties of Nanosized Mn- and Cr-Doped Strontium Y-Type Hexagonal FerritesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Muhammad Javed Iqbal Nanometer-sized crystallites of Y-type strontium hexaferrite, Sr2Ni2Fe12O22 and its Mn- and Cr-doped derivatives have been synthesized by the sol,gel method. Y-type phase formation was achieved at a considerably lower temperature of 950°C than is required in the traditional solid-state method (1200°C). The effect of doping of manganese at the tetrahedral site, Sr2Ni2,xMnx Fe12O22 (x=0.0,2.0), and chromium at octahedral site, Sr2Ni2 Fe12,yCryO22 (y=0.0,1.5), has been studied. The crystal structure remains unaffected by the substitutions. The crystallite size in the range of 13,45 nm is calculated from the X-ray diffraction data. The energy-dispersive X-ray fluorescence analysis shows that Y-type hexaferrites can be prepared with a base of strontium. The extent of doped Cr+3 ions at the octahedral site has been increased from the reported maximum value of y=1.5. Scanning electron micrographs of the samples showed a homogenous microstructure. The dc electrical resistivity studies show that these hexaferrites exhibit high resistivity at room temperature. Cr-doped samples have comparatively higher resistivity than Mn-doped samples. The doubly doped (Cr+Mn) samples possess high resistivity (7.37 × 109,-cm), a low dielectric constant (33.88 at 3000 Hz), and a high Curie temperature (>698 K). The dielectric energy losses are minimized by increasing the Mn and Cr contents of the synthesized samples. [source] The analysis on the origin of high resistivity in Cl-doped polycrystalline CdZnTe thick filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004K. H. Kim Abstract Polycrystalline CdZnTe thick films were grown by thermal evaporation method using CdZnTe and CdZnTe:Cl source. Non-doped CdZnTe thick films have Te-rich stoichiometry having resistivity 3.3 × 109 ,cm. The Cl-doped CdZnTe thick films have 1.2 × 1010 ,cm in resistivity. To evaluate the role of Cl in the increasement of the resistivity, the density of localized states were calculated from the analysis of transient TOF (time of flight)current. From the comparison of Cl-doped CZT thick films with non-doped and O2 annealed CdZnTe thick films, we have found that Cl doping is related to the formation of states at EV + 0.75 eV region and oxygen reduces grain boundary related defects through formation TeO2 or CdTeO3. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||