Zinc-blende Lattice Research Articles

Plastic deformation and trace element mobility in sphalerite

Abstract Sphalerite (ZnS) is a sulfide found in a large variety of ore deposits and is frequently hosted in meta-morphic terranes that have undergone deformation and related recrystallization. However, the deformation mechanisms of sphalerite are still poorly understood because recrystallization evidence is barely visible under an optical microscope and may reflect complex and frequently multistage mechanisms. Furthermore, sphalerite may host up to a few thousands of parts per million of critical metals such as gallium (Ga), germanium (Ge), and indium (In). Metamorphic conditions and dynamic recrystallization may have induced local or total redistribution of these elements. Modern techniques such as electron backscattered diffraction analyses (EBSD) and laser-induced breakdown spectroscopy (LIBS) applied on sphalerite allow for the examination of grain boundaries, crystal-plastic deformation, and internal chemical diffusion, which classically reflect active deformation mechanisms. In this study, a microstructural and in situ chemical comparison between four sphalerite types (types 1, 2, 3, and 4) has been made for the first time. The four sphalerite types present different deformation imprints, although they are hosted in a similar geological setting: the Pyrenean Axial Zone and the Montagne Noire Variscan massifs (France). Based on EBSD and LIBS mapping, we describe two regional sphalerite growth stages composed of dark red crystals with polygonal shape (type 1, Bentaillou-Liat deposit) and light- to dark-brown euhedral crystals (type 3, Saint Salvy deposit). New investigation at microscale on sphalerite grains from the Saint-Salvy deposit shows late Cu-Ge-Ga enrichment not only in specific sector zonings but also along grain boundaries, growing crystal edges, and in low-angle misorientations or twin boundaries. Following a deformation event that probably occurred during the Pyrenean-Alpine orogeny, these two sphalerite mineralizations have both endured plastic deformation in a dislocation creep regime and dynamically recovered by subgrain rotation (SGR) mechanism. Two mechanisms of Cu-Ga-Ge spatial redistribution are observed and are key processes for the crystallization of Cu-Ga-Ge-rich minerals in sphalerite veins. The first mechanism involved the in situ redistribution of Cu-Ga-Ge contents from a pre-existing concentration in the sphalerite lattice (type 3, Arre deposit), creating Ge-sulfides (briartite), probably during Pyrenean-Alpine orogeny. Formation of this type of Ge-mineral may be related to solid-state diffusion processes. The second mechanism is associated with the circulation of a Cu-Ga-Ge-rich fluid in surrounding rocks. In the pre-existing polygonal sphalerite from Late-Variscan veins (type 2, Pale Bidau deposit), millimeter-size bands of small (<50 µm), recrystallized sphalerite grains are locally observed. Those domains contain inclusions of Cu (chalcopyrite) and Ga and Ge minerals (brunogeierite, carboirite). Fluid-induced diffusion in the polygonal sphalerite aggregates may occur with superimposed dynamic recrystallization, such as the Late-Variscan veins (type 2, Pale Bidau-type). During post-Variscan time, this fluid enriched in Cu-Ga-Ge largely circulated in the upper-crust of this Variscan terrane. This study highlights the key importance of coupled textural (EBSD) and in situ chemical analyses (LIBS) of diverse sphalerite types at a regional scale to indirectly unravel the origin of vein mineralization, and their related critical metal distribution.

Fluorescent sphalerite rich in tungsten, copper, gallium, silver, and other elements from the Cordilleran-style, polymetallic veins of Philipsburg, Montana

Sphalerite from the central, high-sulfidation zone (enargite-stable) of the Philipsburg polymetallic mining district, southwest Montana, displays unusually bright fluorescence (red, orange, yellow, blue, purple, green) under longwave UV light (365 nm). LA-ICP-MS analysis reveals the fluorescent sphalerite has very low Fe (average < 100 ppm) and variable content of other trace elements that correlate to luminescence color banding. Mean/maximum content (in ppm) in fluorescent sphalerite for selected elements are 5.7/7900 Ag, 107/11800 As, 1400/4730 Cd, 917/30400 Cu, 381/5000 Ga, 32/696 Ge, 119/2130 In, 230/8190 Mn, 43/3000 Pb, 16/1700 Sb, and 89/1980 W. This study is the first to document elevated tungsten content (>10 ppm) in sphalerite. Copper is closely correlated with Ga, consistent with the coupled substitution: Cu+ + Ga3+ = 2Zn2+. Similar coupled substitution reactions can be written for Ag+, In3+, As3+, Sb3+, Bi3+, and Ge4+. However, the brightest red fluorescent bands are most closely related to the unexpected presence of W. Sphalerite with high Cu and Ga but lacking W fluoresces yellow and shows a single Raman peak at 349 cm−1 corresponding to pure sphalerite. In contrast, red-fluorescent sphalerite shows the presence of a second peak at 427 cm−1 that increases in intensity with increased W content. We propose that tungsten enters the sphalerite lattice as W6+ via a substitution such as W6+ + 4Cu+ = 5Zn2+ and that this substitution creates lattice strain that results in the anomalous fluorescence and Raman signals. Sphalerite bands with low concentrations of Cu and Ga fluoresce blue or green. Vivid blue fluorescence is displayed by sphalerite with high Cd (>1000 ppm) but low concentrations of all other trace elements. Sphalerite from the low-sulfidation peripheral mines of the Philipsburg district contains high Fe (>10,000 ppm) and does not fluoresce. Nonetheless, this sphalerite is also highly enriched in trace metals, including Ag (mean 2480/max 8660 ppm), Cu (1610/3440), Mn (7020/8100), and Sb (1960/6390). The results of this study underscore the importance of including tungsten in the list of analytes in future studies of trace elements in sphalerite. In addition, a hand-held UV lamp may be a rapid and cost-effective method to screen sphalerite of variable composition in outcrop or drill core. It may be a useful exploration tool to vector towards a high-sulfidation zone of a zoned porphyry or epithermal deposit, when it is present.

Newly discovered germanium minerals in Huize and Maoping MVT Pb[sbnd]Zn deposits in Southwest China: Implications for the germanium enrichment mechanism and exploration

The Sichuan-Yunnan-Guizhou (Chuan-Dian-Qian) region represents the largest Mississippi Valley-type (MVT) Pb-Zn-Ge metallogenic province in China, including giant Huize and Maoping deposits. Research has suggested that Ge is incorporated primarily into the sphalerite lattice in the form of element substitution, and few Ge-bearing minerals have been reported in these deposits. We identified numerous sphalerite colors in Huize and Maoping and further found Ge-bearing minerals in black (C1) sphalerite. These Ge-bearing minerals are randomly distributed and have regular mineral morphologies, suggesting potential co-precipitation with C1 sphalerite rather than formation during later metamorphism and oxidation. One Ge-bearing mineral, argutite (GeO2), is found in Huize C1 sphalerite, which occurs in an isolated distribution or is locally associated with pyrite and hematite. Two Ge-bearing minerals, brunogeierite (GeFe2O4) and argutite (GeO2), are found in the Maoping C1 sphalerite. Brunogeierite is more abundant than argutite and is commonly associated with pyrite and rarely with argutite. The petrography and elemental composition confirmed that the C1 sphalerite in Huize and Maoping is the earliest formed sphalerite with the highest formation temperature. This suggests that high temperatures favor the precipitation of argutite and brunogeierite. However, slight variations in sulfur and oxygen fugacity may have resulted in discrepancies in the occurrence of Ge-bearing minerals between the Huize and Maoping deposits. According to the fluid mixing metallogenic model in the Chuan–Dian–Qian region, we posit that Ge-oxide mineral precipitation benefited from the initial stage of fluid mixing between Ge-bearing reduced fluid and oxidized basinal brine. This is also consistent with the findings that argutite and brunogeierite are exclusively associated with C1 sphalerite. As fluid mixing progresses, Ge is incorporated into the sphalerite lattice via element substitution. The newly discovered independent Ge minerals (argutite and brunogeierite) present greater economic potential than Ge-rich sphalerite does, thereby offering significant insights into the enrichment mechanism of Ge and the further utilization of Ge resources.

Unveiling Variations in Electronic and Atomic Structures Due to Nanoscale Wurtzite and Zinc Blende Phase Separation in GaAs Nanowires.

Phase separation is an intriguing phenomenon often found in III-V nanostructures, but its effect on the atomic and electronic structures of III-V nanomaterials is still not fully understood. Here we study the variations in atomic arrangement and band structure due to the coexistence of wurtzite (WZ) and zinc blende (ZB) phases in single GaAs nanowires by using scanning transmission electron microscopy and monochromated electron energy loss spectroscopy. The WZ lattice distances are found to be larger (by ∼1%), along both the nanowire length direction and the perpendicular direction, than the ZB lattice. The band gap of the WZ phase is ∼20 meV smaller than that of the ZB phase. A shift of ∼70 meV in the conduction band edge between the two phases is also found. The direct and local measurements in single GaAs nanowires reveal important effects of phase separation on the properties of individual III-V nanostructures.

A Late Jurassic Epithermal Pb-Zn Deposit: Insights from Rb-Sr Dating of Quartz-Hosted Fluid Inclusions and Sphalerite Chemical Composition

The Kangjiawan Pb-Zn deposit, situated within the Shuikoushan polymetallic ore field in Changning, Hunan Province, China, is a large-scale Pb-Zn deposit unearthed in 1976. Based on detailed geological field investigations, this study presents the results of the Rb-Sr isotopic dating, electron probe microanalyses (EPMAs), and LA-ICP-MS analyses of the Kangjiawan Pb-Zn deposit in order to determine the ore-forming age and the occurrence of trace elements in sphalerite and thereby constrain the genesis of the deposit. The Rb-Sr dating of quartz-hosted fluid inclusions yielded an Rb-Sr isochron age of 150 ± 4 Ma, with an initial 87Sr/86Sr ratio of 0.71101 ± 0.00008 (MSWD = 1.1), suggesting that the Pb-Zn mineralization of the Kangjiawan deposit took place during the Late Jurassic, coeval with the magmatic activities within the ore field. EPMA and LA-ICP-MS analyses showed that Fe, Mn, and Cd were primarily incorporated into the sphalerite lattice through isomorphous substitution. Specifically, Fe and Mn substituted for Zn, whereas Cd replaced both Fe and Zn. Other elements such as Cu, Sb, and Sn occurred within the sphalerite lattice through mineral micro-inclusions or isomorphic substitution. EPMAs and LA-ICP-MS results showed that the FeS contents in sphalerite were less than 14.33%, with corresponding ore-forming temperatures below 259 °C. The LA-ICP-MS results showed that sphalerites from the Kangjiawan Pb-Zn deposit had relatively high Ga/In ratios ranging from 0.01 to 144, providing further support for medium-to-low-temperature mineralization. The trace element compositions of sphalerites from the Kangjiawan Pb-Zn deposit exhibit skarn-type characteristics, suggesting a potential association with contemporary magmatic activities within the Shuikoushan ore field. During the Late Jurassic, extensive granitic magmatic activities occurred in the study area. At the late stage of magma crystallization, hydrothermal fluid containing Pb and Zn precipitated at medium-to-low temperatures and generated the Kangjiawan Pb-Zn deposit.

Modeling of polarization reversal-induced interface sheet charge in wurtzite-type AlScN/GaN heterostructures

In this work, the value and the polarity of the spontaneous and piezoelectric polarization have been investigated, as the use of two different reference structures for wurtzite-type group-III nitrides, namely, the zinc-blende and the layered-hexagonal crystal lattice, have resulted in different predictions. It was found that although the differences in value and polarity of the polarization for heterostructures such as wurtzite Al1−xScxN/GaN lead to similar interface sheet charges, a significant mismatch is observed when polarization reversal is considered. The interface sheet charge predicted before and after the polarization reversal in the wurtzite Al1−xScxN layer on GaN using the zinc-blende lattice as a reference predominantly shows a change in sign. When using the layered-hexagonal lattice as a reference, not only is the same polarity of the interface sheet charge maintained after polarization reversal, but it is even 30 times larger. In this case, the giant and positive spontaneous polarization values for metal-polar Al1−xScxN extracted from the ferroelectric switching, as well as the alignment of the piezoelectric polarization to it, were observed to be consistent with the predictions referenced to the layered-hexagonal lattice. Thus, it is concluded that the layered-hexagonal reference is not only more suitable for predicting the ferroelectric properties of wurtzite Al1−xScxN but should also be the correct reference when considering polarization reversal in heterostructures. If the significant increase in the interface sheet charge after polarization reversal is experimentally detected, it will allow the design and fabrication of novel devices for future high-frequency and power electronics applications.

Ab-initio calculations and molecular dynamics simulations of In, Ag, and Cu replacing Zn in sphalerite: Implications for critical metal mineralization

Sphalerite has been recognized as the most important carrier mineral of the critical metal of indium (In), which mainly exists in sphalerite lattice through isomorphous substitution for Zn. It is widely reported that there are two significant coupled substitution schemes, namely Ag++In3+→2Zn2+ and Cu++In3+→2Zn2+, for In entering sphalerite in natural mineralization. However, there is still little known about physicochemical constrains on these two substitution reaction processes, which hinders the understanding of In mineralization. Thus, the current study uses ab-initio calculations and molecular dynamics simulations to investigate the replacement processes of Zn by In, Ag and Cu in sphalerite. The doped systems of Zn30InAgS32 and Zn30InCuS32, which correspondingly represent the products of the two substitution processes, were constructed by using 2 × 2 × 2 supercell model of sphalerite. Molecular dynamics method was employed to simulate the doped models, obtaining average configurations and formation energies at different temperatures. Then, ab-initio calculations were utilized to study the population values and electronic properties of the simulated configurations. In order to simulate a system close to natural mineralization conditions, a constant pressure of 30 MPa was set in molecular dynamics simulations, as this pressure level can represent the average metallogenic pressure observed in magmatic-hydrothermal deposits associated with In-bearing sphalerite. The temperature parameters were tested within the range of 175 °C to 400 °C, covering the known possible ore-forming temperatures. The simulation results show: (1) it is more stable for In to enter sphalerite via the coupled substitution scheme of Cu++In3+→2Zn2+ than that of Ag++In3+→2Zn2+; (2) the favorable temperatures for the two substitution processes are 225–250 °C and 325–350 °C; and (3) the changes in chemical reactivity caused by temperature fluctuations during the substitution processes of Zn by In, Ag and Cu may lead to the cyclic oscillation distribution that is commonly observed for In within sphalerite in magmatic-hydrothermal mineralization systems. This discovery not only shows the physicochemical properties of In-rich sphalerite formed by the two reaction processes of replacement of Zn, but more importantly, provides deep insights into the natural mineralising process of In at the atomic or/and molecular scale.

Big data mining on trace element geochemistry of sphalerite

The determination of ore genesis is a main challenge in ore deposit research. Advanced and rapid analytical techniques have given rise to the accumulation of massive amounts of geoscientific data. Therefore, it is imperative to conduct data mining on ore geochemical data to efficiently extract useful metallogenic information. In this contribution, 4095 sets of sphalerite trace element data from 86 deposits of different origins (VMS, MVT, porphyry, epithermal, SEDEX, and skarn) were compiled and analyzed. Factor analysis revealed the effects of physicochemical conditions on sphalerite trace element compositions. Specifically, the high Mn-Fe-Cu-Co-In but low As-Ga-Ge-Sb-Pb concentration of sphalerite is commonly related to decreasing pH or increasing temperature; high sulfur fugacity favors the entry of Fe and Co (but not Ga or Sn) into the sphalerite lattice; and high salinity causes enrichment in Cd-Ga-Ge-Mn, but depletion in Ag-Cu-In-Sb. Multivariate statistical analysis reveals that the Mn-Ge-Sn contents in sphalerite have good potential to differentiate among ore genetic types, the Mn-Ge-In are used to determine between magmatic-hydrothermal and non-magmatic-hydrothermal deposits. Furthermore, machine learning models demonstrate high accuracy of sphalerite trace element data in distinguishing ore types, i.e., 93.02 % (random forest) and 92.82 % (gradient boosting), and its reliability was validated by receiver operating characteristics. Additionally, the blind tests by machine learning on sphalerite trace elements indicate that the Qingshuitang deposit (in the Qin-Hang metallogenic belt, South China), have been an MVT deposit, which is also supported by its low-temperature and high-salinity fluids, wallrock alterations (esp. bariteization), and the obvious age distinction between mineralization and local magmatism. This study highlights that machine learning and multivariate statistical analysis on sphalerite trace-element data can differentiate metallogenic origin and conditions.

Exceptional heavy-fermion semimetals in three dimensions

Topological heavy-fermion systems in three dimensions are usually classified as topological insulators or semimetals. Here, we theoretically predict a different type of heavy-fermion system (dubbed exceptional heavy-fermion semimetal) by studying a three-dimensional periodic Anderson model consisting of strongly correlated localized $f$ electrons and itinerant conduction $c$ electrons in a zincblende lattice. Due to the breaking of inversion symmetry, the quasiparticle lifetimes at different sublattices are distinct, leading to the emergence of Weyl exceptional rings in the complex pole of the Green's function at finite temperatures; such rings lead to the appearance of bounded Fermi surfaces (bulk Fermi disks). As temperatures rise, two pairs of Weyl exceptional rings merge into two exceptional rings with one bounded bulk Fermi surface (bulk Fermi tube), which are experimentally measurable by angle-resolved photoemission spectroscopy. Finally, we use the dynamical mean field theory to calculate the spectral functions which illustrate the emergence of bulk Fermi tubes. Our work thus opens the door for studying exceptional heavy-fermion semimetal phases in three dimensions.

Atomically thin interlayer phase from first principles enables defect-free incommensurate SnO2/CdTe interface

Advancing optoelectronic and emerging technologies increasingly requires control and design of interfaces between dissimilar materials. However, incommensurate interfaces are notoriously defective and rarely benefit from first-principles predictions, because no explicit atomic-structure models exist. Here, we adopt a bulk crystal structure prediction method to the interface geometry and apply it to SnO2/CdTe heterojunctions without and with the addition of CdCl2, a ubiquitous and beneficial, but abstruse processing step in CdTe photovoltaics. Whereas the direct SnO2/CdTe interface is highly defective, we discover a unique two-dimensional CdCl2 interphase, unrelated to the respective bulk structure. It facilitates a seamless transition from the rutile to zincblende lattices and removes defect-states from the interface bandgap. Implementing the predicted interface electronic structure in device simulations, we demonstrate the theoretical feasibility of bufferless oxide-CdTe heterojunction solar cells approaching the Shockley–Queisser limit. Our results highlight the broader potential of designing atomically thin interlayers to enable defect-free incommensurate interfaces.

Enrichment mechanisms and occurrence regularity of critical minerals resources in the Yaojialing Zn skarn polymetallic deposit, Tongling district, eastern China

Critical minerals resources are widely used in emerging industries, and their mineralization characteristics and metallogenic regularity are of high importance. Skarn deposits are one of the important sources of critical minerals resources. Yaojialing deposit is a typical large skarn zinc polymetallic deposit in Tongling district of the Middle and Lower Yangtze River metallogenic belt. The ore bodies are mainly lenticular and veined occurrence along the proximal skarn zone and structural or lithologic contacts, respectively. We recognize five hydrothermal stages in the deposit: skarn stage, oxide stage, early sulfide stage, late sulfide stage and carbonate stage. The early and late sulfide stages are the main ore-forming stages. In addition to the production of zinc, gold and copper, the deposit also contains critical element resources such as cadmium, cobalt, selenium, and tellurium. Taking the Yaojialing deposit as an example, this paper shows the occurrence and distribution of critical minerals resources in a typical skarn deposit by using scanning electron microscope, TESCAN integrated mineral analyzer (TIMA), and sulfide LA-ICP MS analysis. Although there are no cadmium minerals in Yaojialing deposit, cadmium can incorporated in the sphalerite lattice, and sphalerite in veins has elevated cadmium content (average 5478.78 ppm). Tellurium content in various sulfides is very low, and it does not enter into the sulfide lattice. It mainly forms tellurobismuthite, hessite and tetradymite, which occur in Cu-Zn ore formed in the early sulfide stage, there are 227 tetradymite grains in a single rock section. Selenium occurs as naumannite in vein ore in the distal of the deposit; selenium can also incorporated the lattice of chalcopyrite and sphalerite, and the selenium content is elevated in sphalerite formed in the early sulfide stage (average 226.80 ppm). The cobalt mineral glaucodot is only found in skarn ore; cobalt easily incorporated the lattice of pyrite and sphalerite, and pyrite and sphalerite formed in the early sulfide stage are enriched in cobalt (average 1962.18 ppm). The characteristics of trace elements in pyrite and sphalerite show that temperature is the main factor affecting the distribution of critical minerals resources, high temperature is conducive to the enrichment of cobalt, selenium and tellurium, while low temperature is conducive to the enrichment of cadmium. Cadmium, cobalt, selenium, and tellurium have high content in specific parts of the deposit, which makes them potentially amenable to recovery.

Engineering of inorganic nanostructures with hierarchy of chiral geometries at multiple scales

Engineering of inorganic nanostructures with hierarchy of chiral geometries at multiple scales

Phonon thermal transport properties of GaN with symmetry-breaking and lattice deformation induced by the electric field

Electric fields commonly exist in semiconductor structures of electronics, bringing to bear on phonon thermal transport. Also, it is a popular method to tune thermal transport in solids. In this work, phonon and thermal transport properties of GaN with wurtzite and zincblende structures in the finite electric field are investigated using first-principles calculations from the perspectives of symmetry-breaking and lattice deformation. Effects of electric field on phonon transport properties including phonon dispersion and thermal conductivity from the response of electron density distribution only and response from lattice changes are studied in zincblende GaN. It is found that the former has a small but qualitative impact on phonon dispersion relations, i.e., splitting of phonon branches, since it breaks the symmetry of zincblende lattice. While the latter affects both lattice symmetry and size, causing significant changes in phonon properties and an increase in thermal conductivity. In wurtzite GaN, space-group-conserved lattice changes in the finite electric field are studied with lattice deformation only, where thermal conductivity decreases at electric fields significantly with the increase of anisotropy, much different from the changes in zincblende GaN. This work provides a comprehensive understanding of phonon thermal transport properties in GaN in the finite electric field, which promises to benefit phonon transport tuning and provide a reference for thermal management in GaN-based information and power electronics.

Growing epitaxial layers of InP/InGaAsP heterostructures on the profiled InP surfaces by liquid-phase epitaxy

The effect of various planes was studied when growing epitaxial layers by liquid-phase epitaxy (LPE) on the profiled InP substrates. The studies allowed obtaining buried heterostructures in the InP/InGaAsP system and creating highly efficient laser diodes and image sensors.It was found that protruding mesa strips or in-depth mesa strips in the form of channels formed by the {111}А, {111}B, {110}, {112}A, or {221}A family of planes can be obtained with the corresponding selection of an etching agent, strip orientation, and a method of obtaining a masking coating. It was noted that in the case of the polarity of axes being in the direction of &lt;111&gt;, the cut of mesa strips was conducted along the most densely packaged planes. This cut led to the difference in rates of both chemical etching and epitaxial burying of profiled surfaces.The cut was made along the planes at a low dissolution rate {111}A for a sphalerite lattice, to which the studied material, indium phosphide, belongs. Analysis of planes {110} and {Ī10} showed that the location of the most densely packaged planes {111}A and {111}B relative to them is different.

Low-symmetry nanowire cross-sections for enhanced Dresselhaus spin-orbit interaction

We study theoretically the spin-orbit interaction of low-energy electrons in semiconducting nanowires with a zinc-blende lattice. The effective Dresselhaus term is derived for various growth directions, including <11(-2)>-oriented nanowires. While a specific configuration exists where the Dresselhaus spin-orbit coupling is suppressed even at confinement potentials of low symmetry, many configurations allow for a strong Dresselhaus coupling. In particular, we discuss qualitative and quantitative results for nanowire cross-sections modeled after sectors of rings or circles. The parameter dependence is analyzed in detail, enabling predictions for a large variety of setups. For example, we gain insight into the spin-orbit coupling in recently fabricated GaAs-InAs nanomembrane-nanowire structures. By combining the effective Dresselhaus and Rashba terms, we find that such structures are promising platforms for applications where an electrically controllable spin-orbit interaction is needed. If the nanowire cross-section is scaled down and InAs replaced by InSb, remarkably high Dresselhaus-based spin-orbit energies of the order of millielectronvolt are expected. A Rashba term that is similar to the effective Dresselhaus term can be induced via electric gates, providing means to switch the spin-orbit interaction on and off. By varying the central angle of the circular sector, we find, among other things, that particularly strong Dresselhaus couplings are possible when nanowire cross-sections resemble half-disks.

Seeded Growth of HgTe Nanocrystals for Shape Control and Their Use in Narrow Infrared Electroluminescence

HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectronics. Despite their cubic zinc blende lattice, HgTe NCs tend to grow in a multipodic fashion, leading to poor shape and size control. Strategies to obtain HgTe NCs with well-controlled sizes and shapes remain limited and sometimes challenging to handle, increasing the need for a new growth process. Here, we explore a synthetic route via seeded growth. In this approach, small HgTe seeds are nucleated in a first step, and they show narrow and bright photoluminescence with 75% quantum yield in the near infrared region. Once integrated into light emitting diodes, these seeds lead to devices with high radiance up to 20 W·Sr–1·m–2 and a long lifetime. Heating HgTe seeds formed at the early stage promotes the formation of sphere-shaped HgTe with tunable band edges from 2 to 4 μm. Finally, the electronic transport tests conducted on sphere-shaped HgTe NC arrays reveal enhanced mobility and stronger temperature dependence compared to the multipodic shaped particles.

Effect of Surfactants on the Structural and Luminescence Properties of γ‐CuI Nanocrystals Synthesized by Facile Sonochemical Method

AbstractSemiconducting cuprous iodide (CuI) nanocrystals have been synthesized by the one‐pot sonochemical method at room temperature. The synthesis was performed in aqueous medium using ascorbic acid, polyvinyl pyrrolidone, p‐toluene sulfonic acid and docusate sodium as surfactants. X‐ray diffraction (XRD) study of resulting material reveals the crystalline nature, cubic zinc blende lattice structure and γ phase of CuI nanocrystals. Scherrer method, Williamson‐Hall plot and Size‐Strain plot method have been used to investigate the particle size and intrinsic strain values from the XRD analysis. Field emission scanning electron microscopy (FESEM) revealed the morphology and different shapes (truncated tetrahedron, irregular, hexagonal &amp; clustered) of CuI nanocrystals synthesized using different surfactants. In the PL spectrum of γ‐CuI nanoparticles strong near band‐edge emission was observed at about 423 nm. A slight red‐shift in near band edge emission was observed due to the presence of surfactants. Enhanced electrical conductivity values (1.96 S/cm–9.19 S/cm) were obtained due to the presence of surfactants for γ‐CuI nanocrystals. These properties of CuI nanocrystals makes them a suitable material for the design and development of optoelectronic devices.

Unconventional high temperature superconductivity in cubic zinc-blende transition metal compounds

We consider possible high temperature superconductivity (high-T$_c$) in transition metal compounds with a cubic zinc-blende lattice structure. When the electron filling configuration in the d-shell is close to d$^7$, all three t$_{2g}$ orbitals are near half filling with strong nearest neighbor antiferromagnetic (AFM) superexchange interactions. We argue that upon doping, this electronic environment can be one of "genes" to host unconventional high T$_c$ with a time reversal symmetry broken $d_{2z^2-x^2-y^2} \pm i d_{x^2-y^2}$ pairing symmetry. With gappless nodal points along the diagonal directions, this state is a direct three dimensional analogue to the two dimensional $B_{1g}$ d-wave state in cuprates. We suggest that such a case may be realized in electron doped CoN, such as CoN$_{1-x}$O$_x$ and (H, Li)$_{1-x}$CoN.

Structural Characteristics and Processability of Sphalerite in Lead-Zinc Ore of the Gorevka Deposit

The theoretical and experimental substantiation of the behavior of ferrous sphalerite in magnetic separation is given in terms of the Gorevka deposit ore. In sphalerite of this deposit, the content of isomorphous iron ranges as 4–9%. The Mossbauer spectroscopy showed the singlet and two doublet lines of iron, demonstrating separate arrays of iron atoms in sphalerite lattice, with formation of Fe-Fe pairs and clusters of three or more iron atoms. It is found that distribution of iron in sphalerite into three forms coincides for magnetic and nonmagnetic products of zinc concentrate separation. It is determined that magnetic separation undivides sphalerite grains by the isomorphous iron content but is governed by the genetic features of the deposit formation—association of sphalerite with magnetic minerals (pyrrhotine and siderite) and the absence of such associations in galena.

X-ray diffraction analysis by Williamson-Hall, Halder-Wagner and size-strain plot methods of CdSe nanoparticles- a comparative study

Cadmium selenide (CdSe) nanoparticles have been prepared by chemical method using sodium hydrogen selenide precursor and cadmium chloride. X-ray diffraction (XRD) study confirms the crystalline nature of the CdSe nanoparticles with Cubic Zinc blende lattice structure, whereas transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis indicate the spherical morphology of the prepared nanoparticles, having an average size of approximately 36 nm. Here, Williamson-Hall (W–H), Size-Strain Plot (SSP), and Halder-Wagner Method (H–W) have been used to investigate the particle size and the intrinsic strain from the XRD peak broadening analysis. Further, in W–H method, different models have been considered for the determination of physical and microstructural parameters such as strain, stress, and energy density. The average particle size that has been determined from Williamson-Hall, Size-Strain, Halder-Wagner Methods are compared with HR-TEM, AFM, and SEM analysis.