Characterization of Structural Defects in (Cd,Zn)Te Crystals Grown by the Travelling Heater Method

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth of CZT by the Travelling Heater Method (THM) under microgravity are scheduled. A detailed ground-based program was performed to determine experimental parameters and three CZT crystals were grown by the THM. The structural defects, compositional homogeneity and resistivity of these ground-based crystals were investigated. A ZnTe content variation was observed at the growth interface and a high degree of stress associated with extensive dislocation networks was induced, which propagated into the grown crystal region according to the birefringence and X-ray White Beam Topography (XWBT) results. By adjusting the growth parameters, the ZnTe variations and the resulting stress were efficiently reduced. In addition, it was revealed that large inclusions and grain boundaries can generate a high degree of stress, leading to the formation of dislocation slip bands and subgrain boundaries. The dominant defects, including grain boundaries, dislocation networks and cracks in the interior of crystals, led to the resistivity variation in the crystals. The bulk resistivity of the as-grown crystals ranged from 109 Ωcm to 1010 Ωcm.

Identifikasi Bidang Gelincir Zona Rawan Longsor Menggunakan Metode Geolistrik Di Ruas Jalan Toraja – Mamasa

Abstrak. Metode geolistrik tahanan jenis merupakan salah satu dari metode geofisika yang dapat mendeteksi aliran listrik di bawah permukaan bumi. Salah satu aplikasi metode geolistrik tahanan jenis adalah dapat mengidentifikasi bidang gelincir pada daerah rawan longsor. Penelitian ini bertujuan untuk mengetahui bidang gelincir pada daerah rawan lonsor di ruas jalan Toraja – Mamasa. Hasil dari pengukuran geolistrik tahanan jenis dipadukan dengan hasil pengeboran di beberapa titik agar tidak terjadi kesalahan dalam proses interpretasi batuan yang diduga sebagai penyebab terjadinya tanah longsor. Informasi tentang perlapisan tanah tersebut digunakan untuk mengetahui batas-batas ketidakstabilan pada lapisan tanah yang dapat menjadi acuan dalam pengembangan wilayah, khususnya ruas jalan Toraja - Mamasa. Dalam penelitian ini diperoleh nilai resistivitas yang berbeda-beda untuk setiap batuan. Variasi resistivitas yang diperoleh dimulai dari 0 – 978 Ωm. Nilai resistivitas batuan pada bidang gelincir di lokasi penelitian berada pada bidang batas 50-300 Ωm. Batuan penyusunnya berupa batupasir lempung, lava andesit dan basalt. Abstract The resistivity geoelectric method is one of the geophysical methods that can detect the flow of electricity below the earth's surface. One application of the resistivity geoelectric method is to identify the slip field in landslide prone areas. The research aimed to discover slip area of landslide prone zone at the segment road of Toraja-Mamasa. The results of the geoelectric resistivity measurements are combined with the results of drilling at several points so that there are no errors in the process of rock interpretation which are thought to be the cause of landslides. Information about the soil layers is used to determine the boundaries of instability in the soil layer which can be used as a reference in regional development, especially the Toraja - Mamasa road segment. In this research, it was obtained different resistivity values for each rock. The resistivity variation obtained started from 0 - 978 Ωm. The rock resistivity value in the slip plane at the research location is in the 50-300 Ωm boundary fields. The rocks lithologies are clay sandstones, andesite lava and basalt.

Investigating the Earth Fill Embankment of the Lotsane Dam for Internal Defects Using Time-lapse Resistivity Imaging and Frequency Domain Electromagnetics

We investigated the internal structure of the Lotsane Dam for zones that may be prone to seepage and internal erosion using the electrical resistivity imaging (ERI) and the frequency domain electromagnetic (FDEM) methods. Time-lapse ERI measurements were also made for a period of 8 months in order to monitor the temporal evolution of defective zones. Results from both the FDEM and ERI measurements show two main layers. The first is an upper conductive layer varying in thickness from 10 to 25 m which is related to the clay core embankment. Situated beneath this upper conductive layer is a highly resistive crystalline basement on which the dam was founded. Furthermore, the ERI and FDEM measurements revealed the presence of fractures and possible zones of weakness within the dam foundation. Time-lapse ERI measurements revealed resistivity increases in the observed possible defective zones, including proximal to the spillway and at the embankment-foundation interface. The long-term resistivity variation may be indicating change in material properties in those portions of the dam, and may evolve to destabilize the structural integrity of the dam and or develop into preferential seepage pathways with time. The identified anomalous zones are good indicators that the embankment integrity is at risk and we suggest continuous geophysical monitoring of Lotsane Dam structure in order to ensure dam safety and integrity on the long term.

The Relationships of Microscopic Evolution to Resistivity Variation of a FIB-Deposited Platinum Interconnector

Depositing platinum (Pt) interconnectors during the sample preparation process via a focused ion beam (FIB) system is an inescapable procedure for in situ transmission electron microscopy (TEM) investigations. To achieve good electrical contact and avoid irreversible damage in practical samples, the microscopic evolution mechanism of FIB-deposited Pt interconnectors need a more comprehensive understanding, though it is known that its resistivity could be affected by thermal annealing. In this work, an electron-beam FIB-deposited Pt interconnector was studied by advanced spherical aberration (Cs)-corrected TEM combined with an in situ heating and biasing system to clarify the relationship of microscopic evolution to resistivity variation. During the heating process, the Pt interconnector underwent crystallization, organic matter decomposition, Pt nanocrystal growth, grain connection, and conductive path formation, which are combined actions to cause several orders of magnitude of resistivity reduction. The comprehensive understanding of the microscopic evolution of FIB-deposited Pt material is beneficial, not only for optimizing the resistance performance of Pt as an interconnector, but also for understanding the role of C impurities with metal materials. For the purpose of wiring, annealed electron-beam (EB)-deposited Pt material can be recommended for use as an interconnector in devices for research purposes.

Effect of nano and micro conductive materials on conductive properties of carbon fiber reinforced concrete

In this study, the pressure sensitivity and temperature sensitivity of the diphasic electric conduction concrete were investigated by measuring the resistivity using the four-electrode method. The diphasic electric conduction concrete was obtained by mixing nano and micro conductive materials (carbon nanofibers, nano carbon black and steel slag powder) into the carbon fiber reinforced concrete (CFRC). The results indicated that, with the increase of conduction time, the resistivity of CFRC decreased slightly at the initial stage and then became steady, while the resistivity of CFRC containing nano carbon black had a sharp decrease at the dosage of 0.6%. With the increase of compression load, the coefficient of resistivity variation of CFRC containing nano carbon black and steel slag powder changed little. The coefficient of resistivity variation increased with the increase of steel slag powder in the dry environment, and CFRC had preferable pressure sensitivity when the mass fractions of carbon fiber and carbon nanofiber were 0.4% and 0.6%, respectively. Besides, in the humid environment, the coefficient of resistivity variation decreased with the increase of steel slag powder, and the diphasic electric conduction concrete containing 0.4% carbon fibers and 20% steel slag powder had the best pressure sensitivity under the damp environment. Moreover, in the dry environment, CFRC containing nano and micro conductive materials presented better temperature sensitivity in the heating stage than in the cooling stage no matter carbon nanofiber, nano carbon black or steel slag powder was used, especially for the CFRC containing steel slag powder.

Three-dimensional Magnetotelluric Crustal Model of High Agri Valley seismic area to identify and to quantify the resistivity variation in depth

<p>The High Agri Valley (HAV) is an axial zone of the Southern Apennines thrust belt chain with a strong seismogenic potential as shown by different stress indicators and space geodesy data that suggest an NE-SW extensional stress regime still active. Moreover, the HAV hosts the Europe’s largest onshore oil and gas field, which give it further strategic importance.</p><p>There is a certain ambiguity concern the causative fault of the large event (M=7.0) occurred in 1857 in Agri Valley, although two well-documented fault systems are recognised as potentially seismogenic: the Monti della Maddalena Fault System (MMFS) and the Eastern Agri Fault System (EAFS).</p><p>With the aim to bring new information on identification and characterization of the principal structures, on the fluids distribution and their possible relationship with the developed of kinematics in upper fragile crust, several multiscale and multidisciplinary surveys are currently running in the HAV. Here we present the first results of a 3D Magnetotelluric (MT) investigation composed of 58 MT soundings in the period range [10<sup>-2</sup> Hz, 10<sup>3</sup> Hz] which cover an area of approximately of 15 km x 30 km. All the 3D results were obtained by using the 3D inversion conde ModEM: Modular EM Inversion Software.</p><p>The work carried out so far has been mainly focused on the definition of the best mesh to adopt, both in terms of cell size and orientation, and on the correct choice of the inversion parameters: resistivity of the starting model, smoothing model parameter, minimum error floor attributed to the data, regularization parameter (trade-off).</p><p>The 3D MT preliminary model obtained shows a good agreement with 2D models previously realized using a part of the same dataset and defines the main geo-structural features of the HAV.</p><p>The resistivity variations in HAV subsurface will be jointly interpreted with accurate seismic data collected by seismic broadband network INSIEME (composed by 8 stations distributed throughout the Agri Valley) and other available geophysical and geological data.</p><p>The interconnection between the conductivity and seismicity information will be useful to implement the knowledge on the role that fluids play in fault zones and in earthquake processes. </p>

Electrical resistivity variation connected to volcanic earthquake in the Campi Flegrei, Italy

<p>In this study we show an 2D Electrical Resistivity Tomography (ERT) survey acquired in Agnano site pre (Dec 5<sup>th</sup>, 2019) and post (Dec 12<sup>th</sup>, 2019) earthquake events occurred in Pisciarelli-Solfatara areas. This earthquake swarm consisted of sequence of 34 earthquakes with Magnitude (Md) -1.1≤Md≤2.8 at depths between 0.9 and 2.3 km. In particular, the earthquake of Dec 06<sup>th</sup>, 2019 at 00:17 UTC with Md = 2.8 (depth 2 km) was the maximum recorded event since bradyseismic crisis began in 2005.</p><p>The ERT survey allow us to identify the main structural boundaries (and their associated fluid circulations) defining the shallow architecture of the Agnano volcano. The hydrothermal system is identified by very low values of the electrical resistivity (<20 Ω m). Its downwards extension is clearly limited by the lava and pyroclastic fragments, which are relatively resistive (>100 Ω m). The resistivity values are increased after the main shock. This increase in resistivity may have been caused by a change in the state of stress and a decrease in pore pressure (subsequent depressurization). Previously to the earthquake, an increase in pressurized fluids has been observed which have reduced the resistivity values. The present observation suggests that the temporal variation of the resistivity values is related to the variation of the pore fluid pressure in the source area of the swarm, facilitated by earthquake and the subsequent fluid diffusion. The combination of these qualitative results with structural analysis leads to a synthetic model of magmatic and hydrothermal fluids circulation inside the Agnano area, which may be useful for the assessment of potential hazards associated with a renewal of fluid pressurization, and a possibly associated partial flank-failure.</p>