Journal articles on the topic 'Semicore state'

This study, with experiments and comparisons, aims to analyze the difference of stainless (SUS316L) microtubes in the flaring forming among dies with various semicone angles (35°, 40°, 45°, 50°, and 55°). The flow rule by Prandtl-Reuss combined with the finite element deformation theory and updated Lagrangian formulation (ULF) is applied to establish the finite element analysis equation for an incremental elastoplastic deformation to simulate the microtube flaring process. The broadrminalgorithm is utilized in the forming process for the elastoplastic state and die contact. The simulation data allow acquiring the deformation traceability, the relationship between punch load and punch stroke, the distribution of stress and strain, the distribution of the thinnest thickness resulted from dies with different semicone angles, and the distribution of flaring radius caused by dies with distinct semicone angles in the forming process. The experimental result presents similar results to the relationship between punch load and punch stroke and the simulation of the coefficient of frictionμ=0.05, revealing the analysis being suitable for the analysis of microtube cone angle flaring process. The analysis and experimental results show that the thinnest thickness of the microtube increases with increasing semicone angles of dies and the maximal flaring radius of microtubes increases with increasing semicone angles of dies.

The thermogravimetric method was applied to study the combustion characteristics of waste plastics and semicoke mixture at different heating rates with temperature ranging from room temperature to 1173 K. Also, the kinetic parameters of combustion process were also estimated by fitting the experimental data to the calculated data. The results showed that the mixed combustion process of waste plastics and semicoke could be divided into volatile combustion stage and fixed carbon combustion stage. The addition of waste plastics could increase the comprehensive combustion characteristic index (S) and flammability index (C). It showed synergistic effect in the mixed combustion process. When the additive amount of waste plastics was 60%, the S value and C value reached peak point at the heating rate of 20 K/min. The heating rate had a promotion effect on combustion rate. The mixed combustion process of waste plastics and semicoke could be well simulated by the n-order rate model of double parallel reactions. The activation energies E in the first stage of combustion of the mixture were higher than that in the second stage, and the preexponential factor k was opposite. Meanwhile, a marked kinetic compensation effect was presented between the activation energy and the preexponential factor.

The thermal behavior of coal tar refined soft pitch (CTRSP) was investigated by using polarizing microscope with heating stage and thermogravimetric analyzer. The phenomena of carbonization regime process of CTRSP were observed directly in the micro-picture taken online. The results showed that the carbonization thermal dynamic process of CTRSP is divided into several typical stages. At 30-250°C,there is small molecular evaporation; at 250-390 °C,there is thermal decomposition and small molecular evaporation; at 390-480°C,there is the condensation of small molecules and radicals into macromolecules and directional arrangement generating small spheres; at 480-520°C,there is the coking stage; at 520-560°C, there is the semicokes dehydrogenation and shrinkage. The spherules are formed at about 390°C. The growth process of the spherules is divided into several stages: absorption optical isotropic matrix asphalt to grow, two spherule collision fusion and growth, finally (at 480-520°C) due to gravity is greater than surface tension small spheroid disintegration deformation and became fibrillar semicoke (at 520-560 °C). Thermogravimetric (TG) - differential thermogravimetry (DTG) curve are treated by Freeman-Carrolls non isothermal differential method, coal tar soft pitchs first-order reaction is from 253°C to 325°C, from 370 °C to 413°C two temperature stages, activation energy is 28.575 kJ/mol and 60.210 kJ/mol, pre-exponential factor is 2.328×106and 1.4833×107, respectively. The microscopic picture recording was consistent with thermal heavy kinetic equation and the results confirmed that the chief of thermal decomposition reaction is operated from 253 °C to 325 °C, the most of condensation polymerization reaction is operated from 370 °C to 413 °C.

Continuous sugar centrifugal is used to separate sugar and molasses from massecuite. The centrifugal basket is pierced with numerous holes to allow the molasses to escape and is lined with metal gauze, which serves to retain the sugar while allowing the molasses to pass through. The centrifugal basket is conical in shape (Fig. 1), runs at a constant speed in the range 1200 to 2200 rpm., and is fed by a continuous stream of material. The semicone angle α varies from 25 deg to 35 deg. What prompted this investigation is a fairly high level of working stress experienced in commerically available centrifugals, often close to yield stress. This technical brief presents the steady state stress distribution patterns in these centrifugals using a fairly accurate model. Since the problem under consideration is cyclic, a symmetric model using the finite element method with triangular shell elements is employed to determine the stresses and displacements. Besides, the critical speeds of the baskets have also been computed using Rayleigh’s method.

We start by investigating the arising of a spin-orbit coupling and a Darwin-type term that stem from Lorentz symmetry breaking effects in the CPT-odd sector of the Standard Model Extension. Then, we establish a possible scenario of the violation of the Lorentz symmetry that gives rise to a linear confining potential and an effective electric field in which determines the spin-orbit coupling for a neutral particle analogous to the Rashba coupling [E. I. Rashba, Sov. Phys. Solid State 2, 1109 (1960)]. Finally, we confine the neutral particle to a quantum dot [W.-C. Tan and J. C. Inkson, Semicond. Sci. Technol. 11, 1635 (1996)] and analyze the influence of the linear confining potential and the spin-orbit coupling on the spectrum of energy.

Metallurgical fuel, including various types of mineral fuels: coke, hard coal, brown coal, peat, combustible shales and products of their technological conversion – needs environmental control of their use safety. When burning metallurgical fuel, harmful substances fall into the environment such as chlorine, fluorine, sulfur, arsenic, which worsen the environmental situation. Technical regulations on the safety of coal products contain requirements to limit the content of harmful impurities and their maximum permissible concentrations. Due to the wide spread of fluorine in natural and technological objects and the high toxicity of its compounds, the control of fluorine content is an urgent problem in the industrial use of metallurgical fuel. Physical methods for the determination of fluorine in solid fuel based on excitation of different spectra of the studies allow to identify it without decomposition directly in the source solid material, however, they have several limitations (sensitivity, accuracy of definition, complexity of hardware design). In other methods, mainly in ionchromatography and ionometry, samples are decomposed and fluorine is transferred into the solution. High temperature processes: pyrohydrolysis and combustion melting are usually used for decomposition. The aim of this work was to create a selective method for ionometric determination of fluorine with a fluoride-selective electrode. The study objects were samples of coal: brown, gas, semicoke, coke nut. Effective decomposition of the samples by two-stage high-temperature melting with KNaCO3 is proposed. Hydrolysis coprecipitation of accompanying interfering cations with chloride iron (II) was carried out for fluorine discharge in the solution in the form of free fluoride. The procedure of decomposition and ionometric determination of fluorine is described. The estimation of trueness and reproducibility of the developed technique by the method of sample variation was carried out. Fluorine content in the studied samples did not exceed the limit- tolerance values for commercial samples of coal products, which indicates the environmental safety of the samples in their subsequent energy application. The developed method is promising for the control of fluorine impurity in metallurgical fuel and is characterized by selectivity and simple carrying out.

Kostryukova AM, Mashkova V, Krupnova TG, Egorov NO. 2018. Phytoplankton biodiversity and its relationship with aquatic environmental factors in Lake Uvildy, South Urals, Russia. Biodiversitas 19: 1422-1428. Lake Uvildy is one of the largest and the most unique of the South Ural region lakes. This mountain deep lake, which has the status of a natural monument. The purpose of this paper was to study the phytoplankton community structure and the aquatic environmental factors in Lake Uvildy. The phytoplankton samples were collected from 5 sites of Lake Uvildy, then filtered through the plankton net and were preserved in 5% formalin. Species were identified using the handbooks by Sladecek, Yarushina, and Al-Kandari. Water samples were taken for water quality analysis. The several physicochemical parameters were measured in situ by a Portable Meters (Multitest IPL-513 and Multitest KSL-111, Semico Ltd, Russia, Novosibirsk). The others parameters were measured in the laboratory of the Department of Chemistry of the South Ural State University according to the standard methods. The sampling was made during the vegetation period in June-July 2014. The water quality was evaluated using the Shannon biodiversity index. A total of 38 species (11 phyla, 31 genera), including 9 species of Chlorophyta, 13 species of Bacillariophyta, 9 species of Cyanophyta, 4 species of Euglenophyta, 2 species of Chrysophyta, 1 species of Dinophyta, were identified. The phytoplankton species in the lake were mainly represented by Cyanophyta and Bacillariophyta. There were 5 dominant species: Fragilaria crotonensis, Asterionella formosa, Dolichospermum lemmermannii, Microcystis aeruginosa, and Coenococcus planktonicus. The Shannon index value comprised 1.27-2.21. According to the saprobity index values (1.63-2.35), the water in the late is evaluated as satisfactorily clean. Physico-chemical parameters were factors driving the change in phytoplankton community composition in Lake Uvildy.

We really like pores in our research group. Big pores, small pores, ordered pores, random pores – they all have a function and as is often found, show behaviour that is not always predicted. I started my research journey trying to put extremely thin films onto near-perfect III-V crystals to control (opto)electronic properties and when the first TEM on our campus showed the image in Fig. 1 almost 21 years ago (1,2), the electrochemical modification of the InP made more sense. In this talk, I will summarise the journey from porous InP that led to studies of other porous semiconductors such as silicon (3-10) and GaN (11-15), periodically ordered photonic crystal porous structures (16-26) and some optical, thermal and electrochemical properties photocatalysis, batteries and related that were modified by the porous structure, leading up to the most recent porous materials (27). References C. O’Dwyer, D. N. Buckley, D. Sutton, M. Serantoni and S. B. Newcomb, J. Electrochem. Soc., 154, H78 (2007). C. O’Dwyer, D. N. Buckley, D. Sutton and S. B. Newcomb, J. Electrochem. Soc., 153, G1039 (2006). C. O'Dwyer, W. McSweeney and G. Collins, ECS J. Solid State Sci. Technol., 5, R3059 (2016). W. McSweeney, C. Glynn, H. Geaney, G. Collins, J. D. Holmes and C. O'Dwyer, Semicond. Sci. Technol., 31, 014003 (2016). W. McSweeney, H. Geaney and C. O'Dwyer, Nano Res., 8, 1395 (2015). W. McSweeney, H. Geaney, C. Glynn, D. McNulty and C. O'Dwyer, ECS Trans., 66, 39 (2015). W. McSweeney, O. Lotty, C. Glynn, H. Geaney, J. D. Holmes and C. O'Dwyer, Electrochim. Acta, 135, 356 (2014). W. McSweeney, O. Lotty, N. V. V. Mogili, C. Glynn, H. Geaney, D. Tanner, J. D. Holmes and C. O'Dwyer, J. Appl. Phys., 114, 034309 (2013). E. Quiroga-González, J. Carstensen, C. Glynn, C. O’Dwyer and H. Föll, Phys. Chem. Chem. Phys., 16, 255 (2014). C. Glynn, K.-M. Jones, V. Mogili, W. McSweeney and C. O'Dwyer, ECS J. Solid State Sci. Technol., 6, N3029 (2017). O. V. Bilousov, J. J. Carvajal, A. Vilalta-Clemente, P. Ruterana, F. Díaz, M. Aguiló and C. O’Dwyer, Chem. Mater., 26, 1243−1249 (2014). O. V. Bilousov, J. J. Carvajal, H. Geaney, V. Z. Zubialevich, P. J. Parbrook, O. Martínez, J. Jiménez, F. Díaz, M. Aguiló and C. O’Dwyer, ACS Appl. Mater. Interface, 6, 17954 (2014). O. V. Bilousov, J. J. Carvajal, H. Geaney, F. Díaz, M. Aguiló and C. O’Dwyer, CrystEngComm, 16, 10255 (2014). O. V. Bilousov, H. Geaney, J. J. Carvajal, V. Z. Zubialevich, P. J. Parbrook, A. Giguère, D. Drouin, F. Díaz, M. Aguiló and C. O’Dwyer, Appl. Phys. Lett., 103, 112103 (2013). O. V. Bilousov, J. J. Carvajal, D. Drouin, X. Mateos, F. Díaz, M. Aguiló and C. O'Dwyer, ACS Appl. Mater. Interfaces, 4, 6927 (2012). S. O'Hanon, D. McNulty, R. Tian, J. Coleman and C. O'Dwyer, J. Electrochem. Soc., 167, 140532 (2020). D. McNulty, H. Geaney, Q. Ramasse and C. O'Dwyer, Adv. Funct. Mater., 30, 2005073 (2020). A. Lonergan, C. Hu and C. O'Dwyer, Phys. Rev. Materials, 4, 065201 (2020). G. Collins, A. Lonergan, D. McNulty, C. Glynn, D. Buckley, C. Hu and C. O’Dwyer, Adv. Mater. Interfaces, 7, 1901805 (2020). D. McNulty, A. Lonergan, S. O'Hanlon and C. O'Dwyer, Solid State Ionics, 314, 195 (2018). D. McNulty, H. Geaney, D. Buckley and C. O'Dwyer, Nano Energy, 43, 11 (2018). A. Lonergan, D. McNulty and C. O'Dwyer, J. Appl. Phys., 124, 095106 (2018). S. O'Hanlon, D. McNulty and C. O'Dwyer, J. Electrochem. Soc., 164, D111 (2017). D. McNulty, E. Carroll and C. O'Dwyer, Adv. Energy Mater., 7, 1602291 (2017). E. Armstrong and C. O'Dwyer, J. Mater. Chem. C, 3, 6109 (2015). E. Armstrong, D. McNulty, H. Geaney and C. O’Dwyer, ACS Appl. Mater. Interfaces, 7, 27006 (2015). A. Lonergan, B. Murphy and C. O'Dwyer, ECS J. Solid State Sci. Technol., 10, 085001 (2021). Figure 1. Bright field TEM of a cross section of an InP electrode after a potential sweep from 0.0 to 0.44 V (SCE) in 5 mol dm-3 KOH at 2.5 mV s-1. The plane of the micrograph is (011). Figure 1

In recent years, germanium (Ge) has attracted a lot of attention for the development of next generation devices due to its higher carrier mobilities compared with silicon (Si) and its compatibility for complementary metal-oxide-semiconductor (CMOS) applications. It is widely known that Ge is an indirect-band semiconductor like Si. However, by introducing tensile strain, the 136 meV difference between direct and indirect gaps can be reduced. Furthermore, in the case of 0.2-0.3% tensile strained Ge, n-type doping in the order of 1019 cm-3 were expected to be resulted in quasi direct-band light emission around 1550 nm wavelength. [1] The realization of this tensile strained n-Ge is promising for the integration of light sources on next generation Ge-based devices. Here, we focused on n-type Ge deposition using molecular beam epitaxy (MBE) method and have succeeded in realizing highly Sb-doped epitaxial n-Ge films by modulating the deposition temperatures. [2] Moreover, we have recently reported the crystallization of amorphous Ge by high-speed continuous wave laser annealing (CWLA), which more importantly also resulted in the introduction of 0.55-0.62% tensile strain. [3] In this study, we applied the similar annealing technique for crystallization of Sb-doped Ge toward the realization of tensile strained n-type Ge films. Sb-doped poly-crystalline Ge films with high Sb concentration (approximately 1019 cm-3) and thickness of about 100 nm were deposited on quartz substrate by molecular beam deposition at 450ºC substrate temperature. Then, 300 nm of SiO2 capping layer was deposited by sputtering in room temperature, such that the sample structure become that shown in Fig.1(a). The samples then annealed in the CWLA system equipped with Nd:YVO4 solid state laser with wavelength of 532 nm as the light source, which scan laser light at the speed (vscan) of 800 m/min. Also, the laser is focused to 20 μm diameter and shifted at 5 μm to scan the samples. Here, the laser power (Elaser) was changed from 300 to 1000 mW. After laser annealing, the capping layer were removed then the samples were characterized by micro-Raman spectroscopy. The annealed sample surface shows brighter contrast compared to the as-deposited samples, as shown in Fig.1(b) and (c), which indicate the structural change of Ge layer. Raman spectra measured at surface of annealed Ge layers are summarized in Fig.2. Here, Ge-Ge peak around 300.2 cm-1 confirmed on the samples, indicating the crystallization of the Ge layers. This peak is not shifted in low Elaser but largely shifted in high Elaser at up to -2.4 cm-1 for undoped and -3.6 cm-1 for the Sb-doped Ge films. This difference could be explained by the liquid phase recrystallization after Ge layer melted in high Elaser (≥600 mW). During recrystallization process, tensile strain is accumulated upon cooling as the tensile strain amount (0.43-0.63%) is agree with the thermal expansion value of Ge between solidification temperature and room temperature (-0.60%). This mechanism is similar to the crystallization of amorphous Ge films on quartz substrates in our previous work. [3] These results show the successful crystallization of tensile strained n-Ge layer by the CWLA method. This finding will be useful for the growth of Ge-based films and a promising step toward the development of CMOS-integrated optoelectronics. Further investigation of the annealing conditions and its relations with the properties of Sb-doped Ge films will be discussed in the main presentation. References Liu, J., Kimerling, L. C. & Michel, J. Semicond. Sci. Technol. 27, (2012). Saputro, R.H., Matsumura, R. & Fukata, N. Cryst. Growth & Des. 21, 6523–6528 (2021). Matsumura, R. & Fukata, N. ECS J. Solid State Sci. Technol. 9, 063002 (2020). Figure 1

The ultrawide-bandgap (UWBG) AlGaN alloy system is emerging as a promising material for next generation power semiconductor devices. The increase in bandgap as the alloy composition is varied from the binary endpoints GaN to AlN leads to an increase in the critical electric field, which is a key parameter determining the performance of power semiconductor devices. As development of GaN and SiC materials for high-frequency and high-power devices reaches a state of maturity, pursuit of improved device performance is generating interest in UWBG materials with larger bandgaps. High Al composition AlGaN alloys, in addition to offering increased critical electric fields, offer prospects for improved device performance in high temperature operation. Fundamental challenges to the development of AlGaN-based devices, such as controllable doping, electrical contacts, and effective passivation, remain, but a variety of power devices have already been demonstrated (1-3). Point defects strongly affect the material properties of semiconductors, with important consequences for device performance. In traditional semiconductors, such as Si, point defects have been studied extensively, and point defect engineering methods have been developed to enhance device performance. However, the properties of point defects in UWBG materials are not as well understood. Point defects may be introduced during device growth, fabrication, and operation. On the one hand, intentionally introduced impurities (dopants) are critical to the control of electrical transport, while on the other hand, unintentionally introduced impurities may act deleteriously as carrier traps or recombination centers. In AlGaN, compensation by deep level, native point defects or unintentionally incorporated impurities limits achievable free carrier concentrations in electronic devices, while defects and their complexes affect the optical properties in optoelectronic devices. Since point defects exert such a strong influence on material properties, and are often responsible for device degradation, knowledge of their formation mechanisms and material effects are essential to develop strategies for the required control of point defect concentrations (4). In this work, we studied the optical signatures of deep level defects in single crystal AlN substrates. AlN possesses a high thermal conductivity and a close lattice match to high Al composition alloys, which make it an excellent substrate choice for growth of AlGaN-based power electronic and optoelectronic devices. High-quality, 2-inch diameter AlN substrates with average threading dislocation densities below 103 cm-2 were recently demonstrated (5). However, high optical absorption in the ultraviolet-C (UV-C) region was observed in AlN substrates grown by physical vapor transport (PVT), due to a deep level absorption band related to the carbon impurity. This absorption band negatively impacts the efficiency of UV-C optoelectronic devices that require light propagation through the substrate. In order to reduce the unwanted UV-C absorption, we studied the optical properties of double-side polished, 2-inch, c-plane AlN substrates by ultraviolet-visible (UV-Vis) spectroscopy and developed strategies for point defect control. Spatially uniform absorption coefficients below 30 cm-1 at 265 nm were demonstrated across 2-inch substrates (6). In this talk, UV-Vis absorption, photoluminescence (PL) emission, and PL excitation spectra will be presented and correlated with measured impurity concentrations from secondary ion mass spectrometry (SIMS) data, in order to identify deep level defects in AlN. Finally, the mechanisms for reduction of UV-C absorption in PVT AlN will be discussed. References R. J. Kaplar, A. A. Allerman, A. M. Armstrong, M. H. Crawford, J. R. Dickerson, A. J. Fischer, A. G. Baca, and E. A. Douglas, ECS J. Sol. State Sci. and Technol. 6(2), Q3061 (2017). P. H. Carey IV, F. Ren, A. G. Baca, B. A. Klein, A. A. Allerman, A. M. Armstrong, E. A. Douglas, R. J. Kaplar, P. G. Kotula, and S. J. Pearton, IEEE Trans. Semicond. Manuf. 32(4), 473 (2019). A. G. Baca, A. M. Armstrong, B. A. Klein, A. A. Allerman, E. A. Douglas, and R. J. Kaplar, J. Vac. Sci. Technol. A 38, 20803 (2020). S. Washiyama, P. Reddy, B. Sarkar, M. H. Breckenridge, Q. Guo, P. Bagheri, A. Klump, R. Kirste, J. Tweedie, S. Mita, Z. Sitar, and R. Collazo, J. Appl. Phys. 127, 105702 (2020). R. Dalmau, J. Britt, H. Fang, B. Raghothamachar, M. Dudley, and R. Schlesser, Mater Sci. Forum 1004, 63 (2020). R. Dalmau, S. Kirby, J. Britt, and R. Schlesser, ECS Trans. 104(7), 49 (2021).

Wire-grid polarizers constitute a traditional component for the control of polarization in free-space devices that operate in a broad part of the electromagnetic spectrum. Here, we present an aluminium-based THz wire grid polarizer, fabricated on a sub-wavelength thin flexible and conformal foil of Zeonor polymer having a thickness of 40um. The fabricated device,characterized by means of THz time-domain spectroscopy, exhibitsa high extinction ratio between 30 and 45dB in the 0.3-2.1THz range. The insertion losses oscillate between 0 and 1.1dB andthey stemalmost exclusively from moderate Fabry-Perót reflections and it is engineered forvanishing at 2THz for operation with quantum cascade lasers. Full Text: PDF ReferencesI. F. Akyildiz, J. M. Jornet, C. Han, "Terahertz band: Next frontier for wireless communications", Phys. Commun. 12, 16 (2014). CrossRef M.C. Kemp, P.F. Taday, B.E. Cole, J.A. Cluff, A.J. Fitzgerald, W.R. Tribe, "Security applications of terahertz technology", Proc. SPIE 5070, 44 (2003). CrossRef M. Schirmer, M. Fujio, M. Minami, J. Miura, T. Araki, T. Yasui, "Biomedical applications of a real-time terahertz color scanner", Biomed. Opt. Express 1, 354 (2010). CrossRef R.P. Cogdill, R.N. Forcht, Y. Shen, P.F. Taday, J.R. Creekmore, C.A. Anderson, J.K. Drennen, "Comparison of Terahertz Pulse Imaging and Near-Infrared Spectroscopy for Rapid, Non-Destructive Analysis of Tablet Coating Thickness and Uniformity", J. Pharm. Innov. 2, 29 (2007). CrossRef Y.-C. Shen, "Terahertz pulsed spectroscopy and imaging for pharmaceutical applications: A review", Int. J. Pharm. 417, 48(2011). CrossRef A.G. Davies, A.D. Burnett, W. Fan, E.H. Linfield, J.E. Cunningham, "Terahertz spectroscopy of explosives and drugs", Mater. Today 11, 18 (2008). CrossRef J.F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, D. Zimdars, "THz imaging and sensing for security applications?explosives, weapons and drugs", Semicond. Sci. Technol. 20, S266 (2005). CrossRef D. Saeedkia, Handbook of Terahertz Technology for Imaging, Sensing and Communications (Elsevier, 2013).N. Born, M. Reuter, M. Koch, M. Scheller, "High-Q terahertz bandpass filters based on coherently interfering metasurface reflections", Opt. Lett. 38, 908 (2013). CrossRef A. Ferraro, D.C. Zografopoulos, R. Caputo, R. Beccherelli, "Periodical Elements as Low-Cost Building Blocks for Tunable Terahertz Filters", IEEE Photonics Technol. Lett. 28, 2459 (2016). CrossRef A. Ferraro, D.C. Zografopoulos, R. Caputo, R. Beccherelli, "Broad- and Narrow-Line Terahertz Filtering in Frequency-Selective Surfaces Patterned on Thin Low-Loss Polymer Substrates", IEEE J. Sel. Top. Quantum Electron. 23 (2017). CrossRef B. S.-Y. Ung, B. Weng, R. Shepherd, D. Abbott, C. Fumeaux, "Inkjet printed conductive polymer-based beam-splitters for terahertz applications", Opt. Mater. Express 3, 1242 (2013). CrossRef J.-S. Li, D. Xu, J. Yao, "Compact terahertz wave polarizing beam splitter", Appl. Opt. 49, 4494 (2010). CrossRef K. Altmann, M. Reuter, K. Garbat, M. Koch, R. Dabrowski, I. Dierking, "Polymer stabilized liquid crystal phase shifter for terahertz waves", Opt. Express 21, 12395 (2013). CrossRef D.C. Zografopoulos, R. Beccherelli, "Tunable terahertz fishnet metamaterials based on thin nematic liquid crystal layers for fast switching", Sci. Rep. 5, 13137 (2015). CrossRef G. Isić, B. Vasić, D. C. Zografopoulos, R. Beccherelli, R. Gajić, "Electrically Tunable Critically Coupled Terahertz Metamaterial Absorber Based on Nematic Liquid Crystals", Phys. Rev. Appl. 3, 064007 (2015). CrossRef K. Iwaszczuk, A.C. Strikwerda, K. Fan, X. Zhang, R.D. Averitt, P.U. Jepsen, "Flexible metamaterial absorbers for stealth applications at terahertz frequencies", Opt. Express 20, 635 (2012). CrossRef F. Yan, C. Yu, H. Park, E.P.J. Parrott, E. Pickwell-MacPherson, "Advances in Polarizer Technology for Terahertz Frequency Applications", J. Infrared Millim. Terahertz Waves 34, 489 (2013). CrossRef http://www.tydexoptics.com DirectLink K. Imakita, T. Kamada, M. Fujii, K. Aoki, M. Mizuhata, S. Hayashi, "Terahertz wire grid polarizer fabricated by imprinting porous silicon", Opt. Lett. 38, 5067 (2013). CrossRef A. Isozaki, et al., "Double-layer wire grid polarizer for improving extinction ratio", Solid-State Sens. Actuators Microsyst. Transducers Eurosensors XXVII 2013 Transducers Eurosensors XXVII 17th Int. Conf. On, IEEE, pp. 530?533 (2013). DirectLink A. Ferraro, D. C. Zografopoulos, M. Missori, M. Peccianti, R. Caputo, R. Beccherelli, "Flexible terahertz wire grid polarizer with high extinction ratio and low loss", Opt. Lett. 41, 2009(2016). CrossRef M.S. Vitiello, G. Scalari, B. Williams, P.D. Natale, "Quantum cascade lasers: 20 years of challenges", Opt. Express 23, 5167(2015). CrossRef A. Podzorov, G. Gallot, "Low-loss polymers for terahertz applications", Appl. Opt. 47, 3254(2008). CrossRef

Heteroepitaxial growth of Ge on Si has great interest for various optoelectronic applications such as Ge photodiodes(1). However 4.2% of lattice mismatch causes dislocation formation and island growth. High quality Ge(001) growth techniques are reported in ref.(2-4). Moreover, Ge(111) surface is also interesting because of higher carrier mobility(5). Furthermore, Ge(110) is preferred orientation of virtual substrates for epitaxial graphene growth(6). In the case of the Ge deposition on Si(111) and Si(110) substrates, it seems that the process conditions used for Ge growth on Si(001) are not suitable to realize high crystallinity and smooth surface (7). In this paper, we present a method of high quality and smooth Ge layer growth on Si(111) and Si(110), which is the same level as the Ge growth on Si(001). Epitaxial growth of Ge on Si(111) and Si(110) is carried out using a reduced pressure chemical vapor deposition system. After HF last clean, a wafer is baked at 1000°C and cooled down to 600°C in H2 and further to 300-550°C in N2 to form a hydrogen-free Si surface. Then a 100 nm thick Ge layer is deposited as a seed layer using GeH4 with N2 carrier gas. Afterward the wafer is heated up to 450-650°C in H2 and the main part of Ge is deposited using a H2-GeH4 gas mixture. For threading dislocation density (TDD) reduction, annealing at 800°C in H2 is performed for several times (cyclic annealing) by interrupting the Ge growth. Atomic-force microscopy (AFM) is used for surface roughness analysis. Scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD) are used for structural characterization of the Ge layer. Secco defect etching combined with angle view scanning electron microscopy (SEM) or optical microscope is used for TDD evaluation. Figure 1(a,b) summarize the root mean square (RMS) roughness of Ge(111) and Ge(110) seed layers grown at 300-550°C before and after postannealing at 600-800°C. If the growth temperature is lower than 350°C for Ge(111) and 400°C for Ge(110), a significant increase of the surface roughness is observed after postannealing at 700°C and 800°C, respectively. For both crystal orientations, the lowest RMS roughness is observed by depositing at 450°C for as deposited and postannealed samples. The maintained RMS roughness even after postannealing at 800oC may be indicating good crystal quality even at as deposited condition. To confirm the influence of the growth temperature on the crystallinity, cross section TEM images of the Ge(111) and the Ge(110) seed layers deposited at 300°C and 450°C are shown in Fig. 2(a-d). In the case of Ge growth at 300°C (Fig. 2(a,b)), a very high density of stacking faults (SF) and high surface roughness are observed for both crystal orientations. In contrast, by depositing at 450°C (Fig. 2(c,d)), lower SF density in the Ge layer is observed compared to that at 300°C. By postannealing, an improvement of crystallinity is observed for the Ge seed layers deposited at 450°C. However, in the case of 300°C, the crystallinity cannot be improved by the postannealing, because a too high density of dislocations and SF may cause irregular Ge atom migration. As the result, surface roughening occurs. Figure 3(a,b) show AFM surface roughness images after 5 μm-thick Ge(111) and Ge(110) deposited with cyclic annealing at 800°C, respectively. Clear terraces of ~0.3 and ~0.2 nm, whose heights are close to those of Ge(111) bilayer and Ge(110) monolayer, are observed, respectively. RMS roughness of the Ge(111) and the Ge(110) are 0.51 and 0.35 nm, respectively. These RMS roughnesses are comparable to a level reported for Ge (001) in ref.(1). Figure 4 shows TDD of Ge(111) and Ge(110) surfaces as a function of the Ge thickness deposited with cyclic annealing on Si(111) and Si(110) substrates. For both orientations, TDD of ~4×108 cm-2 is obtained for 500 nm-thick samples. With increasing the Ge thickness, the TDD is reduced and levels below TDD of ~5×106 cm-2 are achieved for both Ge (111) and Ge(110) for 5 μm-thick Ge. These methods enable high quality virtual substrate fabrication not only for (001) surfaces but also for (111) and (110) orientation without a chemical mechanical polishing process. References Lischke et al. Nature Photonics15 (2021) 925 Yamamoto et al. Solid-State Electron. 60 (2010) 2 Yamamoto et al. Semicond. Sci. Technol. 33 (2018) 124007 M. Hartmann et al. J. Appl. Phys. 95 (2004) 5905 H. Lee et al. IEDM Tech. Digest (2009) 09-457 J-H. Lee et al. Science 344 6181(2014) 286 M. Hartmann et al. J. Cryst. Growth 310 (2008) 5287 Figure 1

Abstract The rare-earth metal hydrides with clathrate structures have been highly attractive because of their promising high-$$T_{\rm{c}}$$ T c superconductivity at high pressure. Recently, cerium hydride $$\hbox {CeH}_9$$ CeH 9 composed of Ce-encapsulated clathrate H cages was synthesized at much lower pressures of 80–100 GPa, compared to other experimentally synthesized rare-earth hydrides such as $$\hbox {LaH}_{{10}}$$ LaH 10 and $$\hbox {YH}_6$$ YH 6 . Based on density-functional theory calculations, we find that the Ce 5p semicore and 4f/5d valence states strongly hybridize with the H 1s state, while a transfer of electrons occurs from Ce to H atoms. Further, we reveal that the delocalized nature of Ce 4f electrons plays an important role in the chemical precompression of clathrate H cages. Our findings not only suggest that the bonding nature between the Ce atoms and H cages is characterized as a mixture of ionic and covalent, but also have important implications for understanding the origin of enhanced chemical precompression that results in the lower pressures required for the synthesis of $$\hbox {CeH}_9$$ CeH 9 .

This paper reports on the photoluminescence of porous GaPprepared by electrochemical anodization of (111)-oriented bulk material.Porous and bulk GaP exhibits green and red photoluminescence, respectively when excited by the 355-nm laser. The photoluminescence intensity of porous GaP is much stronger than that of the bulk sample. Temperature-dependent time-resolved photoluminescence shows that the green emission gradually decreases when the temperature increases and the photoluminescence full width at haft maximum (FWHM) slightly narrow with decreasing temperature. These results assigned to the contribution of lattice vibrations. Raman scattering measurement is carried out to confirm the size decreasing of the porous GaP material. Keywords PorousGaP, photoluminescence, time-resolved photoluminescence, electrochemical etching References 1. L. T. Canham, Appl. Phys.Lett. 57, 1046 (1990).2. K. Grigoras, Jpn. J. Appl. Phys. 39, 378 (2000)3. H. Koyama, J. Appl. Electrochem. 36, 999 (2006)4. H. A. Hadi, International Letters of Chemistry, Physics and Astronomy, 17(2), 142-152 (2014).5. S. Setzu, P. Ferrand, and R. Romestain, Mater.Sci. Eng, 34, 69-70 (2000).6. S. E. Letant and M. J. Sailor, Adv. Mater, 355, 12 (2000).7. M. T. Kelly, J. K. M. Chun, and A. B. Bocarsly, Nature, 382, 214 (1996).8. G. Di Francia, V. La Ferrara, L. Quercia, and G. Faglia, J. Porous Mater, 7, 287 (2000).9. J. Drott, K. Lindstrom, L. Rosengren, and T. Laurell, J. Micromech. Microeng, 7, 14 (1997).10. B. P. Azeredo, Y. W. Lin, A. Avagyan, M. Sivaguru, K. Hsu, P. Ferreira, Advanced Functional Materials, 26, 2929-2939 (2016).11. A. Anedda, A. Serpi, V. A. Karavanskii, I. M. Tiginyanu, and V. M. Ichizli, Appl. Phys.Lett, 67, 3316 (1995).12. A. I. Belogorokhov, V. A. Karavanskii, A. N. Obraztsov and V. Yu. Timoshenko, JETP Lett. 60, 274 (1994).13. K. Tomioka, S. Adachi, J. App. Phys, 98, 073511 (2005).14. M. A. Stevens-Kalceff, I. M. Tiginyanu, S. Langa, H. Foll and H. L. Hartnagel, J. App. Phys, 89,2560 (2001).15. A. V. Zoteev, P. K. Kashkarov, A. N. Obraztsov and V. Y. Timoshenko, Semiconductors, 30, 775 (1996).16. A. A. Lebedev, V. Y. Rud and Y. V. Rud, Tech. Phys. Lett, 22, 754 (1996).17. H. Richter, Z. P. Wang, and L. Ley, Solid State Commum, 39, 625 (1981).18. L. H. Campbell and P. M.Fauchet, Solid State Commum, 58, 739 (1986).19. V. V. Ursaki, N. N. Syrbu, S. Albu, V. V. Zalamai, I. M. Tiginyanu, and R. W. Boyd, Semicond. Sci. Technl, 20, 745- 748 (2005)20. R. W. Tjerkstra, Electrochemical and Solid-State Letters,9 (5), C81-C84 (2006)

Geometries associated relative stabilities, averaged binding energy, fragmentation energy, second-order energy difference and energy gaps of V-doped germanium cationic clusters GenV+ (n = 9-13) have been investigated by using density functional theory with the BP86 exchange-correlation potential and effective core potential (ECP) LanL2DZ basis sets. Natural population analysis charge is also examined to understand the associated charge transfer in structures of clusters. When an electron is removed from neutral cluster GenV to form the cation cluster GenV+, geometric structure of the lowest energy isomers change. The endohedral cage structure of the cation clusters appears at n = 10 in the cluster Ge10V+. The lowest energy isomers of cation cluster are in triplet state or singlet state. The cluster Ge10V+ is found to be the most stable in terms of stability parameters in the all system GenV+ (n = 9 - 13). Keywords: BP86/LANL2DZ, binding energy, V-Ge clusters, structure of clusters. 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