Catálogo de publicaciones - revistas

<jats:p>The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors. The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZnTe crystals were studied theoretically by Silvaco TCAD software simulation. The sub-bandgap illumination with a wavelength of 890 nm and intensity of 8 × 10<jats:sup>−8</jats:sup> W/cm<jats:sup>2</jats:sup> were used in the simulation to explore the space charge distribution and internal electric field distribution in CdZnTe crystals. The simulation results show that the deep level occupation faction is manipulated by the sub-bandgap illumination, thus space charge concentration can be reduced under the bias voltage of 500 V. A flat electric field distribution is obtained, which significantly improves the charge collection efficiency of the CdZnTe detector. Meanwhile, premised on the high resistivity of CdZnTe crystal, the space charge concentration in the crystal can be further reduced with the wavelength of 850 nm and intensity of 1 × 10<jats:sup>−7</jats:sup> W/cm<jats:sup>2</jats:sup> illumination. The electric field distribution is flatter and the carrier collection efficiency of the device can be improved more effectively.</jats:p>

<jats:p>Ferritic-martensitic steels and ODS steels are attractive candidates for structural materials in advanced nuclear-power systems due to their good swelling resistance. Four kinds of steels, F82H, 15Cr-ODS, SIMP and T91, are investigated in this study. We take 6.4 MeV Fe<jats:sup>3+</jats:sup> ions and energy-degraded 1.0 MeV He<jats:sup>+</jats:sup> ions in the irradiation of these materials to 5 dpa and 60 appm He/dpa, 200 appm He/dpa and 600 appm He/dpa at 300 °C and 450 °C, respectively. The bubble formation and distribution are investigated by transmission electron microscopy (TEM). Formation and distribution of the bubbles in the four investigated steels are compared. The influence of irradiation temperature and helium injection ratio on bubble formation is discussed. It is found that there appears to be homogenously distributed bubbles at 300 °C irradiation while heterogeneously distributed bubbles at 450 °C irradiation.</jats:p>

<jats:p>Three-dimensional integrated circuits (3D ICs) have entered into the mainstream due to their high performance, high integration, and low power consumption. When used in atmospheric environments, 3D ICs are irradiated inevitably by neutrons. In this paper, a 3D die-stacked SRAM device is constructed based on a real planar SRAM device. Then, the single event upsets (SEUs) caused by neutrons with different energies are studied by the Monte Carlo method. The SEU cross-sections for each die and for the whole three-layer die-stacked SRAM device is obtained for neutrons with energy ranging from 1 MeV to 1000 MeV. The results indicate that the variation trend of the SEU cross-section for every single die and for the entire die-stacked device is consistent, but the specific values are different. The SEU cross-section is shown to be dependent on the threshold of linear energy transfer (LET<jats:sub>th</jats:sub>) and thickness of the sensitive volume (T<jats:sub>sv</jats:sub>). The secondary particle distribution and energy deposition are analyzed, and the internal mechanism that is responsible for this difference is illustrated. Besides, the ratio and patterns of multiple bit upset (MBU) caused by neutrons with different energies are also presented. This work is helpful for the aerospace IC designers to understand the SEU mechanism of 3D ICs caused by neutrons irradiation.</jats:p>

<jats:p>Colloidal polymers with tunable chain stiffness have been successfully assembled in experiments recently. Similar to molecular polymers, chain stiffness is an important feature which can distinctly affect the dynamical behaviors of colloidal polymers. Hence, we model colloidal polymers with controlled chain stiffness and study the effect of chain stiffness on glassy behaviors. For stiff chains, there are long-ranged periodic intrachain correlations besides two incompatible local length scales, i.e., monomer size and bond length. The mean square displacement of monomers exhibits sub-diffusion at intermediate time/length scale and the sub-diffusive exponent increases with chain stiffness. The data of localization length of stiff polymers versus rescaled volume fraction for different monomer sizes can gather close to an exponential curve and decay slower than those of flexible polymers. The increase of chain stiffness linearly increases the activation energy of the colloidal-polymer system and thus makes the colloidal polymers vitrify at lower volume fraction. Static and dynamic equivalences between stiff colloidal polymers of different monomer sizes have been checked.</jats:p>

<jats:p>Quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics has been investigated as a potential nuclear fusion structural material, and it has advantages in certain aspects compared with Ti<jats:sub>2</jats:sub>AlC, Ti<jats:sub>3</jats:sub>AlC<jats:sub>2</jats:sub>, and Ti<jats:sub>3</jats:sub>SiC<jats:sub>2</jats:sub> structural materials. In this paper, quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics is pressurized to investigate its structural, mechanical, electronic properties, and Debye temperature. Quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics still maintains a cubic structure under pressure (0–110 GPa). At zero pressure, quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics only has three bonds: Ti–Al, Ni–Al, and Ti–C. However, at pressures of 20 GPa, 30 GPa, 40 GPa, 60 GPa, and 70 GPa, new Ti–Ni, Ti–Ti, Al–Al, Ti–Al, and Ti–Ti bonds form. When the pressure reaches 20 GPa, the covalent bonds change to metallic bonds. The volume of quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics can be compressed to 72% of its original volume at most. Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics. At 50–60 GPa, its mechanical strength can be comparable to pure tungsten, and the material changes from brittleness to ductility. However, the degree of anisotropy of quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics increases with the increasing pressure. In addition, we also investigated the Debye temperature, density, melting point, hardness, and wear resistance of quaternary carbide Ti<jats:sub>3</jats:sub>NiAl<jats:sub>2</jats:sub>C ceramics under pressure.</jats:p>

<jats:p>We propose the concept of thermal demultiplexer, which can split the heat flux in different frequency ranges into different directions. We demonstrate this device concept in a honeycomb lattice with dangling atoms. From the view of effective negative mass, we give a qualitative explanation of how the dangling atoms change the original transport property. We first design a two-mass configuration thermal demultiplexer, and find that the heat flux can flow into different ports in corresponding frequency ranges roughly. Then, to improve the performance, we choose the suitable masses of dangling atoms and optimize the four-mass configuration with genetic algorithm. Finally, we give out the optimal configuration with a remarkable effect. Our study finds a way to selectively split spectrum-resolved heat to different ports as phonon splitter, which would provide a new means to manipulate phonons and heat, and to guide the design of phononic thermal devices in the future.</jats:p>

<jats:p>A new material of Zr<jats:sub>0.1</jats:sub>Al<jats:sub>1.9</jats:sub>Mo<jats:sub>2.9</jats:sub>V<jats:sub>0.1</jats:sub>O<jats:sub>12</jats:sub> is synthesized by the traditional solid state synthesis method. The phase transition, coefficient of thermal expansion, and luminescence properties of Zr<jats:sub>0.1</jats:sub>Al<jats:sub>1.9</jats:sub>Mo<jats:sub>2.9</jats:sub>V<jats:sub>0.1</jats:sub>O<jats:sub>12</jats:sub> are explored with Raman spectrometer, dilatometer, and x-ray diffraction (XRD) diffractometer. The results show that the Zr<jats:sub>0.1</jats:sub>Al<jats:sub>1.9</jats:sub>Mo<jats:sub>2.9</jats:sub>V<jats:sub>0.1</jats:sub>O<jats:sub>12</jats:sub> possesses the strong broad-band luminescence characteristics almost in the whole visible region. The sample is crystallized in a monoclinic structure group of <jats:italic>P</jats:italic>2<jats:sub>1</jats:sub>/<jats:italic>a</jats:italic> (No. 14) crystallized at room temperature (RT). The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K. The material has very low thermal expansion performance in a wide temperature range. Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode (LED) and other optoelectronic devices.</jats:p>

<jats:p>AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy (HVPE) have been fabricated and structurally characterized. The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared. The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150. At the same time, the full width at half-maximum (FWHM) values of (0002)- and (<jats:inline-formula> <jats:tex-math><?CDATA $10\bar{1}2$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>10</mml:mn> <mml:mover accent="true"> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_3_036801_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>)-plane were 64 arcsec and 648 arcsec, respectively. As revealed by AFM, the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation (TD). The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy (TEM) technique combined with geometric phase analysis (GPA). It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface, while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface. Consequently, part of the edge TDs propagated to the surface vertically. The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150.</jats:p>

<jats:p>We investigate the photoconductivities of injection current and the shift current in transition metal dichalcogenide with warping term in the presence of sublattice potential and spin orbit coupling. The system shows the valley photoconductivities of injection current and the photoconductivities of shift current. It is found that the warping term and the geometric tensor play a critical role in the system, which are responsible for the photoconductivities. Due to the interplay between the sublattice potential and the spin orbit coupling, the photoconductivities can be tuned. Furthermore, the effect of warping term on geometric tensor and the amplitude of the photoconductivities are also discussed.</jats:p>

<jats:p>The uncertainty principle is a crucial aspect of quantum mechanics. It has been shown that the uncertainty principle can be tightened by quantum discord and classical correlation in the presence of quantum memory. We investigate the control of the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environment. Our results show that the entropic uncertainty of an observed system can be reduced and the quantum discord between the observed system and the quantum memory system can be enhanced in the steady state of the system by adding an dissipative ancilla. Particularly, via preparing the state of the system to the highest excited state with hight fidelity, the entropic uncertainty can be reduced markedly and the quantum discord can be enhanced obviously. We explain these results using the definition of state fidelity. Furthermore, we present an effective strategy to further reduce the the entropic uncertainty and to enhance the the quantum discord via quantum-jump-based feedback control. Therefore, our results may be of importance in the context of quantum information technologies.</jats:p>