Search

The chemical transport method is a process that occurs naturally; however, it is also very useful in the chemical laboratory environment for the synthesis of inorganic crystals. It was successfully used for the syntheses of simple and complex inorganic compounds, from binary (e.g., ZnS, CdSe) to quaternary (e.g., Cu2ZnSnS4) compounds. Many experimental parameters influence the quality of products of chemical transport reactions, and among them, one may distinguish the used precursors and applied temperature gradient. The careful selection of experimental conditions is crucial for the production of high-quality crystals. Mathematical descriptions of the chemical transport phenomena, however, may potentially help in the design of proper conditions. [ABSTRACT FROM AUTHOR]

Elemental Te and Cd are successfully recovered from CdTe via a combinatorial process involving chemical vapor transport (CVT) using sulfur as transport agent giving elemental Te being deposited. Separation is successfully enabled by the first process for CVT of Te starting with CdTe. Cd is subsequently recovered by an oxidation of the formed CdS to CdO followed by reduction to Cd metal with natural gas, in which Cd can also be separated via the gas phase. Hereby, the process addresses the main critical elements of the active material in thin film CdTe solar cells regarding both, scarcity and toxicity. Both, closed and open systems were investigated displaying more or less thermodynamic control of the system. Transport rates were determined for the closed system as well as for an open system working with sulfur vapour at moderate temperatures below and close to the boiling point of sulfur. Excellent purity of tellurium was achieved already by the initial transport, leading to low Cd2+ concentrations in the obtained Te being below the quantification limit of microwave plasma‐atomic emission spectroscopy (MP‐AES) (≪0.05 wt %). [ABSTRACT FROM AUTHOR]

Silicon structures with dielectric insulation, silicon-on-insulator structures, and group-III nitride compounds on silicon (AlN/Si, GaN/Si, etc.) are most often used in high-power electronics. One of the challenges in producing such structures is complex deformation (bending or warping) of the structures resulting from the use of a relatively thick layer of polysilicon as a support structure for the single-crystal silicon regions. The work investigates the dependence of the mechanical properties of polysilicon layers on the growth temperature during their deposition by the chemical vapor transport method. The dependence of the properties of polysilicon on the composition and ratio of gas reagents in the deposition process is shown. For chloride and bromide atmospheres, the optimal ranges of operating temperatures and operating ratios of chlorine and bromine in the gas environment are established. It is revealed that the main technological parameter determining the bending of silicon structures and its direction is the growth temperature of the polysilicon layer. The results of groove filling in silicon structures with dielectric insulation during formation of the support layer are presented. The obtained results have practical significance for the technology of creating semiconductor devices for high-power electronics. [ABSTRACT FROM AUTHOR]

The van der Waals (vdW) heterostructures, achieved by integrating atomically thin materials with distinct band structures and interfaces, exhibit diverse properties, enabling unprecedented opportunities for various device applications. Herein, we demonstrate controllable growth of vertically stacked heterobilayers (hBLs) of atomically thin selenene and WSe2 through a single-step-confined space chemical vapor transport (CVT) strategy. With an aim to leverage the electrocatalytic activity of the WSe2 domain toward hydrogen generation, along with the high photoresponsivity of CVT-grown selenene domains, we fabricate a microreactor device assembly to study the photoenhanced catalytic performance of the heterobilayer single domains toward hydrogen evolution. When exposed to light, the Se/WSe2 hBL exhibits a significant improvement in the hydrogen evolution reaction (HER) activity with a much lower overpotential and a smaller Tafel slope compared to their pristine counterparts. Control experiments carried out on mechanically stacked hBLs show poor HER activity, further confirming the effect of the interface on the overall photoenhanced HER performance of the vertical bilayer structures. The mechanism of the enhanced HER activity of the hBL is explored through electrochemical impedance studies and Ultraviolet photoelectron spectroscopy (UPS) measurements. The enhanced catalytic efficiency is attributed to effective electrical coupling and improved charge transfer in the Se/WSe2 hBLs. [ABSTRACT FROM AUTHOR]

Doping semiconductors is crucial for controlling their carrier concentration and enabling their application in devices such as diodes and transistors. Furthermore, incorporating magnetic dopants can induce magnetic properties in semiconductors, paving the way for spintronic devices without an external magnetic field. This review highlights recent advances in growing doped, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors through various methods, like chemical vapor deposition, molecular beam epitaxy, chemical vapor transport, and flux methods. It also discusses approaches for achieving n- and p-type doping in 2D TMDC semiconductors. Notably, recent progress in doping 2D TMDC semiconductors to induce ferromagnetism and the development of quantum emitters is covered. Experimental techniques for achieving uniform doping in chemical vapor deposition and chemical vapor transport methods are discussed, along with the challenges, opportunities, and potential solutions for growing uniformly doped 2D TMDC semiconductors. [ABSTRACT FROM AUTHOR]

A first cadmium copper selenite–bromide Cd7Cu2(SeO3)8Br2 (1) was obtained via chemical vapor transport reactions. The new compound is triclinic, P 1 ‾ , a = 5.3280(5) Å, b = 10.6190(12) Å, c = 11.4380(13) Å, α = 100.856(4)°, β = 93.321(4)°, γ = 91.021(4)°, V = 634.22(12) Å3, R1 = 0.027. 1 has no structural analogs and belongs to a new structure type. The structure of 1 can be described as a host-guest architecture. The host is the [Cd7(SeO3)8]2− interrupted framework, which consists of zigzag layers with a large aperture. The guests are copper bromide species. Thus, the formula can be written as [Cd7(SeO3)8]{Cu2Br2}. [ABSTRACT FROM AUTHOR]

A first cadmium copper selenite–bromide Cd7Cu2(SeO3)8Br2 (1) was obtained via chemical vapor transport reactions. The new compound is triclinic, P 1 ‾ , a = 5.3280(5) Å, b = 10.6190(12) Å, c = 11.4380(13) Å, α = 100.856(4)°, β = 93.321(4)°, γ = 91.021(4)°, V = 634.22(12) Å3, R1 = 0.027. 1 has no structural analogs and belongs to a new structure type. The structure of 1 can be described as a host-guest architecture. The host is the [Cd7(SeO3)8]2− interrupted framework, which consists of zigzag layers with a large aperture. The guests are copper bromide species. Thus, the formula can be written as [Cd7(SeO3)8]{Cu2Br2}. [ABSTRACT FROM AUTHOR]

The promise of two-dimensional (2D) rhenium diselenide (ReSe2) in electronics and optoelectronics has sparked considerable interest in this material. However, achieving the growth of high-quality ReSe2 thin films on a wafer scale remains a significant challenge. In this study, we adopted a two-step method to produce ReSe2 thin films by combining magnetron sputtering of Re and ReOx onto flat substrates with subsequent selenization via atmospheric pressure chemical vapor transport (CVT). After analyzing the produced films using X-ray diffraction to identify the crystalline phase in formed thin film and scanning electron microscopy (SEM) to examine surface morphology, it was determined that the suitable temperature range for the 15 min selenization process with CVT is 650 °C–750 °C. Further investigation of these optimally produced ReSe2 thin films included atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and Raman spectroscopy. The bulk electrical analysis of these films and AFM and SEM surface morphology revealed a strong reliance on the type of precursor material used for their synthesis, whereas optical measurements indicated a potential for the films in non-linear optics applications, irrespective of the precursor or temperature used. This study not only provides a new pathway for the growth of ReSe2 films but also sheds light on the synthesis approaches of other 2D transition metal dichalcogenide materials. [ABSTRACT FROM AUTHOR]

A comparative analysis of photodetectors based on TiS2 nanosheets and on TiS2 nanosheets functionalized with silver nitrate is carried out. TiS2 nanosheets were synthesized by a chemical vapor transport technique, followed by a 1-hour ultrasonication treatment. The obtained solution was deposited between interdigitated electrodes fabricated on the surface of a flexible substrate using a dielectrophoresis process. Polyethylene terephthalate was used as a flexible substrate material. The characteristics of the fabricated photodetectors were determined by illuminating them with tunable-power laser light at 1064 nm. A significant effect of silver nitrate particles scattered in the volume of the photodetector sensitive material on its efficiency is observed. The superiority of the photodetector based on TiS2 nanosheets functionalized with silver nitrate is demonstrated. This photodetector demonstrates a significant response for all the laser light powers used (11.6, 19.6, 51, 100, and 150 mW), shows fast response (0.23±0.01 s) and recovery (0.49±0.02 s) times, coupled with high sensitivity (260∙103±7∙103 A/W), quantum efficiency (303∙103±8∙103 A/W∙nm) and detectivity (3.10∙1013±0.09∙1013 Jones) at an incident laser light power of 11.6 mW. The results obtained in this study can be used for the development and optimization of modern optoelectronic devices.

The chemical transport method is a process that occurs naturally; however, it is also very useful in the chemical laboratory environment for the synthesis of inorganic crystals. It was successfully used for the syntheses of simple and complex inorganic compounds, from binary (e.g., ZnS, CdSe) to quaternary (e.g., Cu2ZnSnS4) compounds. Many experimental parameters influence the quality of products of chemical transport reactions, and among them, one may distinguish the used precursors and applied temperature gradient. The careful selection of experimental conditions is crucial for the production of high-quality crystals. Mathematical descriptions of the chemical transport phenomena, however, may potentially help in the design of proper conditions.

Ternary chalcogenide PbGa2Se4 with high resistivity, photosensitivity, and excellent nonlinear properties, exhibits a potential application in optoelectronic and nonlinear optical devices. However, the preparation of large‐sized pure PbGa2Se4 crystals is challenging due to the presence of peritectic reaction L+α(Ga2Se3)→PbGa2Se4${\mathrm{L}} + {{\alpha}}({G{a}_2S{e}_3}) \to PbG{a}_2S{e}_4$ and a narrow homogeneity region. Here, a "quenching‐annealing" method (quenching at 850 °C in ice water, and then annealing at 650 °C for 250 h by reheating) is developed to eliminate the PbSe second phase during the synthesis. Subsequently, the PbGa2Se4 single crystals are successfully grown using chemical vapor transport (CVT) with the I2 as the transport agent. The resulting crystal exhibits the crystal structure belonging to Fddd space group with the lattice parameters of a = 12.7192 Å, b = 21.2831 Å, and c = 21.5226 Å. Additionally, it possesses a wide bandgap (≈2.26 eV), high resistivity (6.59 × 1012 Ω·cm), and defect density calculated via space charge limited current measurement (SCLC) as 2.46 × 1011 cm−3. Photodetectors based on these as‐grown crystals demonstrate exceptional photosensitivity along with a high detectivity (3.2 × 108 Jones). [ABSTRACT FROM AUTHOR]

Doping semiconductors is crucial for controlling their carrier concentration and enabling their application in devices such as diodes and transistors. Furthermore, incorporating magnetic dopants can induce magnetic properties in semiconductors, paving the way for spintronic devices without an external magnetic field. This review highlights recent advances in growing doped, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors through various methods, like chemical vapor deposition, molecular beam epitaxy, chemical vapor transport, and flux methods. It also discusses approaches for achieving n- and p-type doping in 2D TMDC semiconductors. Notably, recent progress in doping 2D TMDC semiconductors to induce ferromagnetism and the development of quantum emitters is covered. Experimental techniques for achieving uniform doping in chemical vapor deposition and chemical vapor transport methods are discussed, along with the challenges, opportunities, and potential solutions for growing uniformly doped 2D TMDC semiconductors.

The promise of two-dimensional (2D) rhenium diselenide (ReSe2) in electronics and optoelectronics has sparked considerable interest in this material. However, achieving the growth of high-quality ReSe2 thin films on a wafer scale remains a significant challenge. In this study, we adopted a two-step method to produce ReSe2 thin films by combining magnetron sputtering of Re and ReOx onto flat substrates with subsequent selenization via atmospheric pressure chemical vapor transport (CVT). After analyzing the produced films using X-ray diffraction to identify the crystalline phase in formed thin film and scanning electron microscopy (SEM) to examine surface morphology, it was determined that the suitable temperature range for the 15 min selenization process with CVT is 650 °C–750 °C. Further investigation of these optimally produced ReSe2 thin films included atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and Raman spectroscopy. The bulk electrical analysis of these films and AFM and SEM surface morphology revealed a strong reliance on the type of precursor material used for their synthesis, whereas optical measurements indicated a potential for the films in non-linear optics applications, irrespective of the precursor or temperature used. This study not only provides a new pathway for the growth of ReSe2 films but also sheds light on the synthesis approaches of other 2D transition metal dichalcogenide materials.

Three‐dimensional (3D) charge‐written periodic peak and valley nanoarray surfaces are fabricated on a (112¯0$11\bar{2}0$) ZnO single crystal grown via chemical vapor transport. Because the grown ZnO crystals exhibit uniform n‐type conduction, 3D periodic nanoarray patterns are formed via oxygen annealing. These periodically decorated structures show that the peak arrays are conducting at the nanoampere level, whereas the valley arrays are less conductive. Energy dispersive spectroscopy indicates that the valley arrays are deficient in zinc by ≈4–6 at%, and that the peak arrays are deficient in oxygen, respectively. Kelvin probe force microscopy reveals the presence of periodic wiggles featuring variations of ≈70–140‐meV between the peak and valley arrays. A significant decrease in the Fermi level of the valley region is observed (≈190 meV), which corresponds to a high zinc vacancy doping density of 2 × 1018 cm−3. This result indicates the periodic generation of an extremely large electric field (≈11 000 V cm−1) in the vicinity of the peak–valley arrays. Computational analysis corroborates the experimentally observed generation of VZn and the preferential formation of surface protrusions on ZnO (112¯0$11\bar{2}0$) rather than on (0001), based on surface effects, along with the generation of peak and valley features. [ABSTRACT FROM AUTHOR]

The scientific community believes that high-quality, bulk layered, semiconducting single crystals are crucial for producing two-dimensional (2D) nanosheets. This has a significant impact on current cutting-edge science in the development of next-generation electrical and optoelectronic devices. To meet this ever-increasing demand, efforts have been made to manufacture high-quality SnS2 single crystals utilizing low-cost CVT (chemical vapor transportation) technology, which allows for large-scale crystal production. Based on the chemical reaction that occurs throughout the CVT process, a viable mechanism for SnS2 growth is postulated in this paper. Optical, XRD with Le Bail fitting, TEM, and SEM are used to validate the quality, phase, gross structural/microstructural analyses, and morphology of SnS2 single crystals. Furthermore, Raman, TXRF, XPS, UV–Vis, and PL spectroscopy are used to corroborate the quality of the SnS2 single crystals, as well as the proposed energy level diagram for indirect transition in the bulk SnS2 single crystals. As a result, the suggested method provides a cost-effective method for growing high-quality SnS2 single crystals, which could lead to a new alternative resource for producing 2D SnS2 nanosheets, which are in great demand for designing next-generation optoelectronic and quantum devices. [ABSTRACT FROM AUTHOR]

Halide perovskites have many important optoelectronic properties, including high emission efficiency, high absorption coefficients, color purity, and tunable emission wavelength, which makes these materials promising for optoelectronic applications. However, the inability to precisely control large-scale patterned growth of halide perovskites limits their potential toward various device applications. Here, we report a patterning method for the growth of a cesium lead halide perovskite single crystal array. Our approach consists of two steps: (1) cesium halide salt arrays patterning and (2) chemical vapor transport process to convert salt arrays into single crystal perovskite arrays. Characterizations including energy-dispersive X-ray spectroscopy and photoluminescence have been employed to confirm the chemical compositions and the optical properties of the as-synthesized perovskite arrays. This patterning method enables the patterning of single crystal cesium lead halide perovskite arrays with tunable spacing (from 2 to 20 μm) and crystal size (from 200 nm to 1.2 μm) in high production yield (almost every pixel in the array is successfully grown with converted perovskite crystals). Our large-scale patterning method renders a platform for the study of fundamental properties and opportunities for perovskite-based optoelectronic applications.

Abstract Three‐dimensional (3D) charge‐written periodic peak and valley nanoarray surfaces are fabricated on a (112¯0) ZnO single crystal grown via chemical vapor transport. Because the grown ZnO crystals exhibit uniform n‐type conduction, 3D periodic nanoarray patterns are formed via oxygen annealing. These periodically decorated structures show that the peak arrays are conducting at the nanoampere level, whereas the valley arrays are less conductive. Energy dispersive spectroscopy indicates that the valley arrays are deficient in zinc by ≈4–6 at%, and that the peak arrays are deficient in oxygen, respectively. Kelvin probe force microscopy reveals the presence of periodic wiggles featuring variations of ≈70–140‐meV between the peak and valley arrays. A significant decrease in the Fermi level of the valley region is observed (≈190 meV), which corresponds to a high zinc vacancy doping density of 2 × 1018 cm−3. This result indicates the periodic generation of an extremely large electric field (≈11 000 V cm−1) in the vicinity of the peak–valley arrays. Computational analysis corroborates the experimentally observed generation of VZn and the preferential formation of surface protrusions on ZnO (112¯0) rather than on (0001), based on surface effects, along with the generation of peak and valley features.

Three new copper-lead selenite bromides were synthesized by chemical vapor transport reactions. Pb5Cu+4(SeO3)4Br6 is monoclinic, space group C2/m, a = 17.7248(14), b = 5.5484(5), c = 12.7010(10) Å, β = 103.398(2)º, V = 1215.08(17) Å3, R1 = 0.024; Pb8Cu2+(SeO3)4Br10 is orthorhombic, space group I222, a = 9.5893(5), b = 12.4484(9), c = 12.7927(6) Å, V = 1527.08(15) Å3, R1 = 0.027; Pb5Cu2+(SeO3)4(Br,Cl)4 is monoclinic, C2/c, a = 24.590(6) Å, b = 5.5786(14) Å, c = 14.248(4) Å, β = 102.883(7)º, V = 1905.3(9) Å3, R1 = 0.026. The crystal structure of Pb5Cu+4(SeO3)4Br6 consists of two distinct parts: corner- and edge-sharing Cu+Br4 tetrahedra form infinite [Cu+4Br6]2- layers which alternate with [Pb5(SeO3)4]2+ layers. Pb8Cu2+(SeO3)4Br10 contains positively charged unique [Pb8Cu2+(SeO3)4]10+ rod-like chains with Cu2+ cations in the core. These chains are held together by Br- anions. Pb5Cu+4(SeO3)4Br6 and Pb8Cu2+(SeO3)4Br10 belong to new structure types. Pb5Cu2+(SeO3)4(Br,Cl)4 is a synthetic analogue of the mineral sarrabusite, Pb5Cu(SeO3)4Cl4, previously known from an electron diffraction study. The investigation of this synthetic equivalent of sarrabusite by conventional single-crystal X-ray diffraction provides a distinctly improved insight in this crystal structure. Cu atom has well-defined [2O+(2O+2X)] (X = halogen) distorted octahedral coordination. PbOn and SeO3 polyhedra interconnect via common oxygen atoms into [Pb5(SeO3)4]2+ layers parallel to (001). Cu2+ cations interconnect the layers into the framework with the large cavities filled by halide X anions. In all three new compounds described, a common feature is the formation of the selenophile substructure which is terminated by a 'lone-pair' shell that faces bromide complexes thus forming the surface of a halophile substructure. [ABSTRACT FROM AUTHOR]

Recently, low-dimensional structures in the form of bulk crystals and nanoflakes have received considerable interest due to their 2D unique functionality and promising applications in electronics, photonics, sensing devices and photovoltaic solar cells. As a result, remarkable efforts and modifications have been made for the synthesis process of crystalline material by the vapor transport technique. Here, an alternative concept of NbSe2 crystal growth by the chemical vapor transport (CVT) technique using bromine as a vapor transport agent is presented and subsequently analyzed by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) spectroscopy. X-ray powder diffraction analysis revealed hexagonal 2H-NbSe2 and 4H-NbSe2 phases, and characteristic Raman and XPS spectra typical for crystalline NbSe2 were obtained. The environmental sensitivity of the grown crystals is manifested by luminescence attributed to oxidized Nb at the samples' surface. [ABSTRACT FROM AUTHOR]

• Tin in e-waste was efficiently separated and recycled by a novel two-stage CVT process. • The conversion of sn-SnO(g)-SnO 2 during staged oxidation was revealed. • The inhibition mechanism of O 2 content on SnO disproportionation was revealed. • Tetragonal nano-SnO 2 with a crystallinity of 99.9% was obtained from e-waste. E-waste is a valuable resource for the recovery of secondary metals. However, traditional methods only focused on the extraction of Cu and noble metals (Au, Ag, etc.), and significant tin (Sn) loss occurred during the smelting or the leached. In this paper, a novel chemical vapor transport (CVT) process was proposed to separate and recycle Sn from e-waste to prepare nano-SnO 2. The effect of roasting parameters on Sn volatilization and characterization of nano-SnO 2 were investigated using thermodynamic analysis, XRD, SEM, TEM, etc. The results indicated that Sn volatilization of 92.8 % was obtained under optimal roasting parameters under CO-CO 2 -N 2 atmosphere. In addition, nano-SnO 2 with a crystallinity of 99.9 %, an average grain size of 24.8 nm and a specific surface area of 97.9 m2/g was synthesized successfully. [ABSTRACT FROM AUTHOR]

This work investigates the transport properties of layered black phosphorus (BP) grown by the chemical vapor transport (CVT). The electrical measurements are carried out at a temperature ranging from 300 to 2 K and a magnetic field up to 16 Tesla. The CVT‐grown BP exhibits p‐type conduction with an acceptor's 14–1.2 meV activation energy. The concentration of ionized acceptors is 1.2×1017cm−3$1.2 \times {10^{17}}{\rm{c}}{{\rm{m}}^{ - 3}}$ Moreover, the Hall mobility is found to be 138 cm2V−1s−1 and 4 × 104 cm2V−1s−1, respectively, at room temperature and 2 K. This work reveals the potential of CVT synthesis as a simple, nontoxic, and cheap technique to make high‐quality BP crystals with high carrier mobility ready as a solid foundation for BP single‐crystal application. [ABSTRACT FROM AUTHOR]

An extensive study of the chemical mass transfer of indium oxide and In2O3−MexOy systems is performed. The efficiency of C, CO, H2, Se2, S2, In2S, In2Se, HI, HBr, HCl, InI3, InBr3, InCl3, I2, Br2 and Cl2 as transport agents for the growth of In2O3 crystals by means of the chemical vapor transport (CVT) in the sealed growth chambers is estimated. The CVT system composition and mass transfer are evaluated in the wide temperature range (627−1227°С). It is shown that among the examined substances, Cl2 is the optimal transport agent for the growth of In2O3 crystals with a minimum growth nucleus density. The compositions of MexOy−In2O3−Cl2 CVT systems were calculated for oxides (MexOy) of all non-radioactive metals of the periodic table, taking into account various types of chloride species. The effect of temperature (627−1227°С) on the total pressure and mass transfer rate of doping species (MeCln) were investigated. Doping of In2O3 by some metal oxides was predicted to be promising and some calculation results are confirmed experimentally. [ABSTRACT FROM AUTHOR]

We report an ultra-sensitive broadband photodetector based on horizontally aligned titanium disulfide nanosheets (TNs). Firstly, TNs were synthesized using the chemical vapor transport (CVT) technique to develop the photodetector, and then as-prepared TNs were deposited horizontally aligned between the interdigitated electrodes (IDEs) using the dielectrophoresis (DEP) technique. The photodetection performance of the as-prepared photodetector was analysed by illuminating the device with different wavelength low-power LED lights. The sensitivity of the as-developed photodetector has been studied for varying wavelength range (375 nm, 405 nm, 455 nm, 617 nm, 855 nm, 1050 nm) as well as for different power densities of individual incident lights. The as-developed photodetector shows high photoresponse for all mentioned wavelengths and shows a rapid response (10s) and recovery (10s) with ultra-high responsivity (1.174 × 104 AW−1), quantum efficiency (3.20 × 104 AW−1nm−1) as well as detectivity (3.039 × 1011 Jones) for 455 nm wavelength and 0.086 mW/mm2 power density of incident light. The ON/OFF ratio of the as-developed photodetector is found ultra-high i.e. 28.54. Its performance with respect to external bias voltage has also been studied and reported in the manuscript. The as-prepared TNs based photodetector shows many advantageous features like high stability and repeatability. The demonstrated ultra-sensitive photoresponse of as-prepared photodetector suggests the effectiveness of TNs for improving the characteristics of modern optoelectronic devices.

We report an optimized chemical vapor transport method to grow single crystals of (Mn1−xNix)2P2S6 where x = 0, 0.3, 0.5, 0.7, and 1. Single crystals up to 4 mm × 3 mm × 200 μm were obtained by this method. As-grown crystals are characterized by means of scanning electron microscopy and powder X-ray diffraction measurements. The structural characterization shows that all crystals crystallize in monoclinic symmetry with the space group C2/m (No. 12). We have further investigated the magnetic properties of this series of single crystals. The magnetic measurements of the all as-grown single crystals show long-range antiferromagnetic order along all principal crystallographic axes. Overall, the Néel temperature TN is non-monotonous; with increasing Ni2+ doping, the temperature of the antiferromagnetic phase transition first decreases from 80 K for pristine Mn2P2S6 (x = 0) up to x = 0.5 and then increases again to 155 K for pure Ni2P2S6 (x = 1). The magnetic anisotropy switches from out-of-plane to in-plane as a function of composition in (Mn1−xNix)2P2S6 series. Transport studies under hydrostatic pressure on the parent compound Mn2P2S6 evidence an insulator-metal transition at an applied critical pressure of ~22 GPa.

The scientific community believes that high-quality, bulk layered, semiconducting single crystals are crucial for producing two-dimensional (2D) nanosheets. This has a significant impact on current cutting-edge science in the development of next-generation electrical and optoelectronic devices. To meet this ever-increasing demand, efforts have been made to manufacture high-quality SnS2 single crystals utilizing low-cost CVT (chemical vapor transportation) technology, which allows for large-scale crystal production. Based on the chemical reaction that occurs throughout the CVT process, a viable mechanism for SnS2 growth is postulated in this paper. Optical, XRD with Le Bail fitting, TEM, and SEM are used to validate the quality, phase, gross structural/microstructural analyses, and morphology of SnS2 single crystals. Furthermore, Raman, TXRF, XPS, UV–Vis, and PL spectroscopy are used to corroborate the quality of the SnS2 single crystals, as well as the proposed energy level diagram for indirect transition in the bulk SnS2 single crystals. As a result, the suggested method provides a cost-effective method for growing high-quality SnS2 single crystals, which could lead to a new alternative resource for producing 2D SnS2 nanosheets, which are in great demand for designing next-generation optoelectronic and quantum devices.

Substitutional doping of 2D transition metal dichalcogenides (TMDCs) has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications. However, controllable doping of TMDCs remains a challenging issue due to the natural doping of these materials. Here, the controllable growth of Ti‐doped MoS2 monolayers is demonstrated via the chemical vapor transport method, and the atomic embedded structure is confirmed by scanning transmission electron microscope with a probe corrector measurements. Furthermore, the grown Ti‐doped MoS2 monolayer exhibits giant photoluminescence (PL), 85‐fold stronger than a pristine MoS2 monolayer prepared by the same method. The giant PL enhancement is attributed to dopant‐induced O‐Ti‐S units and improved interaction between the monolayer and the mica substrate, increasing the photoluminescence quantum yield and facilitating radiation recombination. The successful growth of Ti‐doped MoS2 monolayer and the improvement of its optical and electrical properties by Ti doping may provide a promising method to engineer the optoelectronic properties of 2D TMDCs materials. [ABSTRACT FROM AUTHOR]

The chemical vapor transport method was used in this research to synthesize MoS2 bulk. Through mechanical exfoliation, we limited the thickness of MoS2 flakes from 1 to 3 ÎĽ m. In order to fabricate a pâ€"n homogeneous junction, we used oxygen plasma treatment to transform the MoS2 characteristics from n-type to p-type to fabricate a pâ€"n homogenous junction and demonstrate the charge neutrality point shift from âˆ'80 to +102 V successfully using FET measurement. The MoS2 pâ€"n homogeneous junction diode showed an excellent p-n characteristic curve during the measurements and performed great rectifying behavior with 1â€"10 Vpp in the half-wave rectification experiment. This work demonstrated that MoS2 flake had great potential for p-n diodes that feature significant pâ€"n characteristics and rectifying behavior. [ABSTRACT FROM AUTHOR]

Fabrication of shape memory alloy (SMA) components based on NiTi is challenging due to the precision with which elemental composition and microstructure must be controlled during processing to achieve desired shape memory behavior. Herein, a method to control chemistry in an NiTi SMA via halide‐activated pack equilibration (SHAPE) against a constant chemical potential reservoir is described. To demonstrate the efficacy of the SHAPE process, an initially titanium‐deficient specimen (pure nickel foam) has been equilibrated against an excess of an intimately mixed two‐phase pack (NiTi + Ti2Ni) in the presence of a vapor phase transport agent (iodine). The two‐phase pack regulates chemical potentials in this two‐component system in accordance with Gibbs' phase rule. Ti‐rich NiTi foams thus produced exhibit reproducible and well‐defined phase transformation behaviors. The SHAPE process is advantageous for the fabrication of shape memory components of varying areal dimension, shape, and/or complexity owing to independence of the equilibrium state of the system from either the initial state of the specimen or the details of the process kinetics. Current limitations and prospects for the application of this method to improve the quality of SMA components are briefly discussed. [ABSTRACT FROM AUTHOR]

Hydrothermal (HT) ZnO substrates were usually used as seeds for the vapor growth of ZnO crystals. In this work, ZnO bulk crystals were grown using the relatively low-cost GaN/Al2O3 substrates as seeds by chemical vapor transport (CVT). With the increase of growth time, the dislocation densities in the crystal decreased from about 1×106 to 6×103 cm−2. The carrier concentration decreased from 1.24×1019 to 1.57×1017 cm−3, while the carrier mobility increased from 63.8 to 179 cm2/(V·s). The optical transmittance in the VISNIR wavelength increased significantly in combination with the decreasing dislocation densities and impurity concentrations. The dislocation lines and related fast diffusion paths gradually decreased and disappeared in the late growth stage, and the crystal qualities were consequently improved. The experimental results show that the properties of as-grown ZnO crystals are comparable with bulk ZnO grown on the HT substrates to some extent. The GaN/Al2O3 seeds may have a potential application value in the industrial production of ZnO single crystals. [ABSTRACT FROM AUTHOR]

In this work, we study the effect of increasing temperature on the structure parameters (lattice, sulfur–sulfur distance, and ruthenium–sulfur distance) and the energy gap of RuS2. However, it was very challenging to obtain a sample of RuS2 due to many factors, some of which are discussed in the introduction. To prepare the crystal growth of RuS2, we have used the chemical vapor transport technique. The crystals obtained show a pyrite structure, of which we studied its crystallographic structure, including the structure of crystals in surface (100). The sample was then characterized by X-ray diffraction and by microprobe analysis. We determine the relationship between the energy gap and the sulfur–sulfur distance. We analyzed the S-S bond compared with the S2 molecule. [ABSTRACT FROM AUTHOR]

Herein, single crystalline boron nanowires (BNWs) have been synthesized by chemical vapor transport using boron element as boron source, iodine as transport agent, and Au as catalyst. The results demonstrate that BNWs can be all formed at 600 °Câ€"950 °C for 2 h, and possess rhombohedral crystal structure (β -boron). The NWs have diameters from several to hundreds of nanometers, and lengths from several to hundreds of microns. A single nanowire has been fabricated to field effect transistor (FET) which shows excellent solar blind photosensitivity and selectivity. The photo/dark current ratio and photoresponsitity is 1.14 and 97.6 mA Wâˆ'1 at a bias of 5 V under light illumination of 254 nm with 0.42 mW cmâˆ'2, respectively, and both the rising and decay time of the onâ€"off currents are 4.6 s and 10.3 s, respectively. When the FET is used as a personal breath sensor, the ratio of exsufflating and inhaling currents is 2.7, rising and decay time of the breath currents are 0.4 s and 2.2 s, respectively. So the BNWs are important sense materials. [ABSTRACT FROM AUTHOR]

Cu2OSeO3 single crystals are grown with an optimized chemical vapor transport technique using SeCl4 as a transport agent (TA). The optimized growth method allows to selectively produce large high‐quality single crystals. The method is shown to consistently produce Cu2OSeO3 crystals of maximum size 8 × 7 × 4 mm with a transport duration of around three weeks. It is found that this method, with SeCl4 as TA, is more efficient and simple compared with the commonly used growth techniques reported in literature with HCl gas as TA. The Cu2OSeO3 crystals have very high quality and their absolute structures are fully determined by simple single‐crystal X‐ray diffraction. Enantiomeric crystals with either left‐ or right‐handed chiralities are observed. The magnetization and ferromagnetic resonance data show the same magnetic phase diagram as reported earlier. [ABSTRACT FROM AUTHOR]

The emergence of two-dimensional (2D) van der Waals magnetic materials has attracted enormous attention due to their novel physical phenomena and potential application in the fields of spintronics and information storage technology. Here, we systematically study the magnetic and transport properties of a van der Waals antiferromagnetic material, FeNbTe2. The magnetic and magnetoresistance measurements verified its antiferromagnetic properties, spin glass state, and negative magnetoresistance effect at lower temperatures. In addition, the measurement results of transport also show the existence of angle-dependent anisotropic magnetoresistance in a wide temperature range and anisotropic magnetoresistance inversion in a certain temperature range.

In this manuscript, we study the grouping of bands and optical properties of p-type ${\rm{Zn}}{{\rm{S}}}_{2}$ pyrite, which helps us in the study of crystal p-type ${\rm{Zn}}{{\rm{S}}}_{2}$ pyrite and its impact in organic photovoltaic cells. Our work has two approaches one theorical where we find the band structure of ${\rm{p}}-$ type ${\rm{Zn}}{{\rm{S}}}_{2}$ by using linear muffin-tin orbital method in the atomic-sphere approximation (LMTO-ASA), the second approach is the experimental where we prepare the crystals by chemical vapor transport. The sample was examined by XRD and optical characterizations. Our results show that the p-type ${Zn}{S}_{2}$ pyrite is a direct semiconductor with optical gap about $1.610\,{eV}$ and calculated gap about $1.550\,{eV}.$ As an illustration of our finding, we present an application of our work to photovoltaic devices.

Abstract Two‐dimensional (2D) anisotropic rhenium diselenide (ReSe2) has attracted lots of attention due to its promising applications in electronics and optoelectronics. However, controlled synthesis of high quality ultrathin ReSe2 remains as a challenge. Here we developed an approach for synthesizing high quality 2D ReSe2 flakes with a thickness down to monolayer by chemical vapor transport (CVT) through carefully tuning the growth kinetics. The atomic structures and anisotropy of the obtained ReSe2 flakes were intensively characterized with scanning transmission electron microscope and angle‐resolved polarized Raman spectroscopy. Field‐effect transistors fabricated on the CVT‐grown ReSe2 flakes showed n‐type semiconducting behavior with an on/off current ratio of 105 and a mobility up to ∼5 cm2 V−1 s−1, which is comparable to mechanically exfoliated flakes and is obvious higher than the samples synthesized with other approaches. This study not only make high quality 2D ReSe2 easily accessible for both fundamental and application explorations but also sheds new lights on the chemical synthesis of other anisotropic 2D materials.

In this work, the ZnO:Ga (GZO) single crystals are grown by the chemical vapor transport (CVT) method. The as‐grown crystals are annealed under an oxygen atmosphere at different temperatures. The GZO crystal's structure and its optical and electrical properties are characterized by X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, X‐ray diffraction (XRD), UV‐VIS spectrophotometry, and variable‐temperature Hall‐effect measurement. The XPS results indicate that the valence states of the majority of gallium atoms in the GZO crystals undergo transition from the metallic (Ga0) to the non‐metallic state (Gax+) with increasing annealing temperature. The Raman and XRD results show that the compressive stress along the biaxial c‐axis on GZO crystals increases gradually with annealing temperature. Meanwhile, the GZO crystal's transmittance within the range of 300 to 1000 nm is improved significantly from being opaque to about 57%. The GZO crystals exhibit a decrease in free‐carrier concentration (1020–1019 cm−3), an increase in carrier mobility (77.8–87.9 cm2/V−1s−1) and resistivity (10−4–10−2 Ω·cm). The annealed GZO crystal's carrier concentration is practically independent of temperature (90–300 K). These results show that the free‐carrier concentrations are affected by the change of valence states in gallium atoms present in the GZO crystal. [ABSTRACT FROM AUTHOR]

In this work, we study the effect of increasing temperature on the structure parameters (lattice, sulfur–sulfur distance, and ruthenium–sulfur distance) and the energy gap of RuS2. However, it was very challenging to obtain a sample of RuS2 due to many factors, some of which are discussed in the introduction. To prepare the crystal growth of RuS2, we have used the chemical vapor transport technique. The crystals obtained show a pyrite structure, of which we studied its crystallographic structure, including the structure of crystals in surface (100). The sample was then characterized by X-ray diffraction and by microprobe analysis. We determine the relationship between the energy gap and the sulfur–sulfur distance. We analyzed the S-S bond compared with the S2 molecule.

Rhenium disulfide (ReS2) single crystals are grown by chemical vapor transport technique. Powder X‐ray diffraction analysis of the single crystals shows them to possess ReS2 phase with triclinic unit cell structure. Energy dispersive analysis of X‐rays shows the crystals to be slightly rich in sulfur and deficient in rhenium. The optical bandgap obtained of the as‐grown single crystals is 1.35 eV. The surface morphology study done by scanning electron microscopy shows that the crystal surface to be flat with layer edges, such observation states that the growth mechanism of crystal have happened by mechanism of sheet spreading. The transmission and diffraction mode electron microscopy shows the single crystals to be layered and crystalline, respectively. The Raman peaks are well assigned to the ReS2. Thermogravimetric and differential thermogravimetric analysis shows the single crystals to disintegrate by two steps. The differential thermal analysis shows that the ReS2 possesses initial endothermic followed by exothermic nature for fast heating rates. In case of a slow heating rate of 10 K min−1, other than endothermic followed by exothermic, the end temperature range shows endothermic nature. The kinetic parameters determined by Kissinger relation shows the single‐crystal samples to disintegrate at a higher temperature range. [ABSTRACT FROM AUTHOR]

The structure and photoelectric properties of ZnO single crystal grown by homoepitaxy before and after annealing was reported. The red-brown ZnO single crystals were grown by the chemical vapor transport (CVT) method. The ZnO single crystal annealed in a high-temperature oxygen atmosphere shows colorless and transparent. The structure of the ZnO single crystal before and after annealing was analyzed by XRD, XPS, EDS, and Raman. The effect of annealing on the defect type and structure of a single crystal was discussed. XRD results show that the growth direction of the ZnO single crystal is (002). The FWHM of ω-rocking curve of ZnO single crystal before and after annealing is 59″ and 31″, respectively. It indicates that the defects in the single crystal decrease significantly after annealing. The composition and valence of elements in the single crystal before and after annealing were analyzed by XPS and EDS, and the results show that the content ratio of Zn and O elements in the single crystal after high-temperature oxygen atmosphere treatment is closer to the theoretical value. Raman spectroscopy analyzed the high-temperature oxygen atmosphere. The different Raman vibration modes of ZnO single crystal before and after annealing were analyzed. Through UV spectrum data analysis, the optical band-gap of ZnO single crystal before and after annealing is obtained to be 3. 05 eV and 3. 2 eV, respectively. Finally, the ZnO single crystal's electrical properties before and after annealing in a high-temperature oxygen atmosphere were analyzed by Hall test. The low-temperature electrical transport characteristics of ZnO single crystal before and after annealing were discussed in depth. [ABSTRACT FROM AUTHOR]

Despite the unique properties of bismuth (Bi), there is a lack of two-dimensional (2D) heterostructures between Bi and other functional 2D materials. Here, a coherent strategy is reported to simultaneously synthesize rhombohedral phase Bi nanoflakes and bismuth oxychloride (BiOCl) nanosheets. The delicate balance between several reactions is mediated mainly for the reduction and chlorination in the chemical vapor transport (CVT) process. The Bi-BiOCl lateral heterostructures have been constructed via the coalescence of the two different 2D nanostructures. The characteristics of ambipolar conducting Bi and insulator-like BiOCl are elaborated by scanning microwave impedance microscopy (sMIM). This work demonstrates a way to construct a 2D Bi nanostructure in junction with its oxyhalide. [ABSTRACT FROM AUTHOR]

Violet phosphorus (VP) has attracted a lot of attention for its unique physicochemical properties and emerging potential in photoelectronic applications. Although VP has a van der Waals (vdW) structure similar to that of other 2D semiconductors, direct synthesis of VP on a substrate is still challenging. Moreover, optoelectronic devices composed of transfer-free VP flakes have not been demonstrated. Herein, a bismuth-assisted vapor phase transport technique is designed to grow uniform single-crystal VP flakes on the SiO 2 /Si substrate directly. The size of the crystalline VP flakes is an order of magnitude larger than that of previous liquid-exfoliated samples. The photodetector fabricated with the VP flakes shows a high responsivity of 12.5 A W -1 and response/recovery time of 3.82/3.03 ms upon exposure to 532 nm light. Furthermore, the photodetector shows a small dark current (<1 pA) that is beneficial to high-sensitivity photodetection. As a result, the detectivity is 1.38 × 10 13 Jones that is comparable with that of the vdW p-n heterojunction detector. The results reveal the great potential of VP in optoelectronic devices as well as the CVT technique for the growth of single-crystal semiconductor thin films., (© 2024 Wiley‐VCH GmbH.)

Cubic boron arsenide ( BAs) belongs to IIl-V compound semiconductor with indirect band gap and zin-blende FCC structure. First-principles calculations based on four-phonon scattering indicate that zinc-blende BAs has an unusually high room-temperature thermal conductivity which is second only to that of diamond. BAs single crystal demonstrates broad application prospects in electronics thermal management due to the unusually high thermal conductivity, and it becomes one of hotpots in the field of compound semiconductor materials. Great progress has been made in the growth of cubic BAs single crystal for the past few years. Ultrahigh thermal conductivity of 1 300 W · m -l • K -l at room temperature is experimentally observed in high-quality BAs single crystal with millimeter-sized synthesized by chemical vapor transport ( CVT ) growth method. Undoped BAs is p-type conducting due to the existence of the intrinsic acceptor defects. The application prospects, crystal structure, material properties and crystal growth method of cubic BAs are introduced. The research progress in crystal growth is reviewed, the technical challenges of crystal growth is described, and development prospects are also analyzed. [ABSTRACT FROM AUTHOR]

The growth of high-quality ZnO bulk crystals is an outstanding challenge, and the nature of grown-in defects in crystals is far from well understood. In this work, a specially designed low-temperature-gradient CVT growth system was developed based on finite element analysis. High-quality ZnO single crystals were successfully grown. The supersaturation front in the growth system was controlled, and internal stress in the crystal was reduced by introducing a radiation baffle and a special seed pedestal. The structural, electrical, and optical properties of ZnO crystals were studied before and after oxygen annealing. The scanning electron microscope (SEM) and optical microscope (OM) results indicate the stable growth is achieved under the Zn-rich growth condition. The X-ray rocking curve measurements reveal the high crystalline quality of the grown crystal with the full-width at half-maximum (FWHM) value of 17 arcsec for the (004) reflection. The time-of-flight secondary ion mass spectroscopy (ToF-SIMS) results prove the high purity of grown crystals and reveal the variations of trace impurity concentrations in crystals. When annealed in oxygen at 1000 °C, the optical band gap (E g) changes from 2.50 eV to 3.15 eV. The Raman analysis indicates that oxygen vacancies (V o) in the as-grown crystal disappear after annealing. The Hall measurements show that the room temperature (RT) mobilities before and after annealing are 197 cm2V−1c−1 and 207 cm2V−1c−1, respectively. The RT carrier concentration decreases by about two orders of magnitude to 5.45 × 1015 cm−3, while the RT resistivity increases by about one order of magnitude to 5.57 Ω cm after annealing. The positron annihilation lifetimes (PALS) results prove the presence of Zn vacancies (V zn) after annealing. The origins of as-grown ZnO green luminescence (GL) and the temperature-dependent blue shifts of the GL peak positions are explained based on Zn i and V o defects. The fine structures of annealed ZnO GL are found to be related to V zn native defects rather than Cu impurity. [ABSTRACT FROM AUTHOR]

Owing to the wide application of Mo in a range of fields, the performance requirements for molybdenum products and molybdenum alloys have increased in recent years. In this study, a novel process is developed for the production of the main component of molybdenum powder, namely MoO 2. Subsequently, the thermal stability of the component is measured, and the reduction mechanism is determined to evaluate its effects on the particle size and morphology. Evidently, the H 2 MoO 5 raw material is completely stripped of O 2 2− following a two-step heat-absorption reaction at 247 °C to produce MoO 3 grains with a needle-like structure. These needle-like grains exhibit a lower reduction temperature than commercial MoO 3 , enabling part of the reduction reaction to occur at 440 °C. Additionally, the reaction rate is higher, and the reaction time at the same temperature is approximately half that of the commercial MoO 3. The reaction mechanism associated with the needle-like MoO 3 is mainly governed by chemical vapor transport (CVT), which leads to greater morphological changes, and can effectively regulate the nucleation and growth of MoO 2. A more dispersed ultrafine/nano-MoO 2 powder with an average particle size of 200–700 nm could be successfully prepared at low temperatures by adjusting the reduction temperature of MoO 3 , and to reduce the reduction temperature. It was found that the MoO 2 grains began to grow continuously along the one-dimensional direction under the combined effects of the CVT and gas–liquid–solid growth mechanisms, forming MoO 2 grains with a unique stripe-like morphology. These results are expected to contribute to the production of high-quality molybdenum powder to satisfy the requirements of various research and application fields. • The hydrogen reduction reactions of H 2 MoO 5 and MoO 3 were investigated. • H 2 MoO 5 generated MoO 3 via a two-step endothermic reaction prior to reduction. • Using H 2 MoO 5 , the reaction temperature was lower and the reaction rate was faster. • Ultrafine and uniformly dispersed MoO 2 (200–700 nm) prepared at low temperatures. • Polyhedral MoO 2 with a different morphology to the feedstock was also prepared. [ABSTRACT FROM AUTHOR]