Epitaxial SnSxSe2−x films with tunable band gap energies (1.0–2.2 eV) are of growing interest for photodetectors and 2D heterostructures for nanoscale electronics. In this study, powder vapor transport growth of SnSxSe2−x was investigated on c-plane sapphire and epitaxial graphene (EG)/6H–SiC substrates using tin, sulfur, and selenium powder sources in a heated tube furnace. The SnSxSe2−x composition was controlled by varying the sulfur and selenium source temperatures and the corresponding chalcogen vapor pressure ratio. Raman spectroscopy was used to determine the alloy composition of the films, and the optical properties were characterized using UV-Vis-NIR spectroscopy. SnSxSe2−x grown on sapphire consisted of vertically oriented platelets. By contrast, large-area, planar coalesced SnSxSe2−x films grew on EG with low surface roughness indicative of a van der Waals growth mode. High-resolution X-ray diffraction θ–2θ scans and pole figure analysis confirm that the SnSxSe2−x films are c-axis oriented with epitaxial relation being $\left[ {11\bar{2}0} \right]$ SnSxSe2−x‖$\left[ {10\bar{1}0} \right]$ 6H–SiC.

The synergetic effects of surface smoothing exhibited during the inductively coupled plasma reactive ion etching (ICP-RIE) of free-standing polycrystalline diamonds (PCDs) were investigated. Changing the assistive gas types generated variable surface oxidation states and chemical environments that resulted in different etching rates and surface morphologies. The main reaction bond mechanism (C–O) during ICP-RIE and the ratio of C–O–C/O–C=O associated with the existence of a uniform smooth surface with root mean square (RMS) roughness of 2.36 nm were observed. An optimal process for PCD smoothing at high etching rate (4.6 μm/min) was achieved as follows: 10% gas additions of CHF3 in O2 plasma at radio frequency power of 400 W. The further etched ultra-smooth surface with RMS roughness <0.5 nm at etching rate of 0.23 μm/min that being produced by transferring this optimum recipe on single crystal diamonds with surface patterns confirmed the effectiveness of the fast smoothing approach and its feasibility for diamond surface patterning.

Ceramic fiber–matrix composites (CFMCs) are exciting materials for engineering applications in extreme environments. By integrating ceramic fibers within a ceramic matrix, CFMCs allow an intrinsically brittle material to exhibit sufficient structural toughness for use in gas turbines and nuclear reactors. Chemical stability under high temperature and irradiation coupled with high specific strength make these materials unique and increasingly popular in extreme settings. This paper first offers a review of the importance and growing body of research on fiber–matrix interfaces as they relate to composite toughening mechanisms. Second, micropillar compression is explored experimentally as a high-fidelity method for extracting interface properties compared with traditional fiber push-out testing. Three significant interface properties that govern composite toughening were extracted. For a 50-nm-pyrolytic carbon interface, the following were observed: a fracture energy release rate of ∼2.5 J/m2, an internal friction coefficient of 0.25 ± 0.04, and a debond shear strength of 266 ± 24 MPa. This research supports micromechanical evaluations as a unique bridge between theoretical physics models for microcrack propagation and empirically driven finite element models for bulk CFMCs.

The codeposition characteristics of Si–B–N ceramics from the SiCl4–NH3–BCl3–H2–Ar system at lower temperatures and phase transformation of as-prepared Si–B–N ceramics at temperatures from 1200 to 1800 °C were investigated. Thermodynamic analysis results indicated that the BN + Si3N4 dual phase region existed from 800 to 1200 °C and that 800 °C was an optimum deposition temperature to deposit Si–B–N ceramic coating. Deposition efficiencies at equilibrium for Si3N4 and BN were high, particularly at temperatures below 1000 °C. Pressure and dilution ratio of H2 had little influence on deposition efficiencies of BN and Si3N4 at 800 °C. The amorphous Si–B–N ceramic coatings were successfully deposited at 800 °C from the same precursor system and contained N–B and N–Si bonds by XPS analysis. It kept amorphous below 1600 °C in N2 and partly transformed to α/β-Si3N4 when heat treated at 1600 °C in N2 for 2 h. These results demonstrated that the composite Si–B–N ceramics could be fabricated at 800 °C and used below 1600 °C.

A diamond film was deposited on YT14 cemented carbide cutting tools with a chemical vapor deposition, the surface-interface morphologies, compositions of chemical elements, phases, atomic bonding energies, and structures of the films were analyzed with a scanning electron microscopy, energy dispersive spectrometer, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, respectively, and the mechanical properties of the film were characterized with a nanoindentation and scratch test, respectively. The results show that the surface of diamond film is continuous and dense, the surface roughness of the film is 79.2 nm, and the average grain size is 478.2 nm. The atomic binding energies of C1s are composed of sp 2 at the Raman shift of 1363.01 cm−1 and sp 3 at the Raman shift of 1556.26 cm−1. The hardness and equivalent elastic modulus of the film is 16.27397 GPa and 166.1791 GPa, respectively, and the binding strength of the film-substrate is 26.2 N, showing a high anti-scratch ability.

A hot wire chemical vapor deposition technique is described for synthesis of 1D nanostructures of a controlled morphology, stoichiometry, and composition. The synthesis involves the evaporation and condensation of metal oxide vapor through the reaction of oxygen with the hot filaments of respective transition metals. The stoichiometry and morphology of MoO3 and WO3 were modulated by varying the filament temperature and partial pressure of oxygen in the growth chamber. Based on the results under different conditions, a morphological phase diagram, and a growth model based on the extent of gas phase supersaturation were developed to understand the growth mechanism. Further, ternary transition metal oxide, NiMoO4, was synthesized as a proof-of-concept for tuning the composition of deposition through simultaneous evaporation of two metal oxides.

Diamond offers a unique combination of extreme physical properties. For many technological applications, diamond samples of the highest crystal quality are required to utilize the ultimate potential of the material. Specifically, grain boundaries, as in polycrystalline films, have to be avoided. In this article, the two major current approaches of synthesizing single crystal diamond by chemical vapor deposition are described. In homoepitaxy, high gas pressure and high power density microwave discharges facilitating growth rates above 50 µm/h form the basis for the deposition of mm-thick single crystal samples. Cloning and tiling followed by homoepitaxial overgrowth are promising novel concepts aimed at an increase in the lateral dimensions. Heteroepitaxial deposition on large-area single crystals of a foreign material represents a second alternative approach. The state of the art for both concepts is summarized, and current as well as potential future applications are discussed.

A novel thermosensitive core/shell microgel with carbon microspheres (CMSs) cores was prepared by three steps. First, oxidized-carbon microspheres were obtained by mixed-acid oxidization. Second, the silane agent of 3-(trimethoxysilyl)-propyl methacrylate was used to functionalize the oxidized-carbon microspheres so as to generate the vinyl groups on the microspheres. Thereafter, the as-synthesized particles were used as seeds in the precipitation polymerization of N-isopropylacrylamide to introduce a thermosensitive polymer microgel shell onto the surfaces of the silanized-CMSs in the presence of an initiator and a crosslinker. The morphology and thermosensitive properties of the composite microspheres were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transformation infrared spectroscopy, thermogravimetry, and dynamic light scattering. Results indicate that the thickness of polymer layer could be adjusted by the crosslinking agent's concentration. The composite microgels had a low critical solution temperature at about 30 °C and exhibited strong thermosensitivity. The controlled release of a drug molecule (a model drug, acetosalicylic acid) was also investigated.

Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation.

In this article, ZnO microtube was prepared using mixed powder of Zn, ZnO, and carbon as source via chemical vapor deposition method. The growth process was discussed in detail, and the high Zn vapor pressure and high growth temperature were considered as two crucial factors determining the formation of tubular structure. A two-step growth model was proposed, namely initial deficient-oxidation and followed by second-volatilization. Four another experiments were further conducted to analyze the growth behavior of reagent species under different Zn vapor pressure and growth temperature, respectively. These experimental results indicated that the formation of Zn-rich structure under enough high Zn vapor pressure and second-volatilization of these abundant interstitial Zn under high growth temperature were important to form tubular structure. Our experimental method provided a feasible route to prepare other hollow structures, such as oxide, sulfide, etc. Furthermore, these synthesized ZnO microtube might have potential application as functional blocks in nanodevices.

Single and multilayer diamond films were grown on silicon by varying substrate distance in hot-filament chemical vapor deposition. The grown films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. From SEM surface images, it was observed that the films grown at substrate distances of 8, 7, and 6 mm and temperatures of 740, 780, and 830 °C possessed cauliflower, pseudocubes, and finally well-faceted cubes morphology. SEM fracture cross-sectional investigations revealed that growth of pseudocubes initiated on the top of cauliflower structure. By using the parametric relations gathered from single layer diamond growth studies, first time, multilayer diamond coatings were grown in situ with tunable thickness by only varying the substrate distance from filament assembly during deposition.

Next-generation fission and fusion nuclear reactor materials will be exposed to very high temperatures, intense neutron radiation, corrosive environments, and, mostly, all three at once. Grand opening will be given to the material, if they have stability at high temperature operating favorable in the extreme environments, self-healing, thermal as well as irradiation properties. Owing to the superior properties of silicon carbide, nuclear scientists are closely evaluating SiC-based materials for various applications in nuclear reactors. In the present perspective, relevant properties, challenging issues, and recommendations are emphasized. Based on our recent experiments, attempt to solve various uses on SiC-based materials in nuclear applications is described in detail.

We present a technique for the direct deposition of nanoporous GaN particles on Si substrates without requiring any post-growth treatment. The internal morphology of the nanoporous GaN particles deposited on Si substrates by using a simple chemical vapor deposition approach was investigated, and straight nanopores with diameters ranging between 50 and 100 nm were observed. Cathodoluminescence characterization revealed a sharp and well-defined near band-edge emission at ∼365 nm. This approach simplifies other methods used for this purpose, such as etching and corrosion techniques that can damage the semiconductor structure and modify its properties.

A TiO2/carbon nanotubes (TiO2/CNTs) composite was synthesized by chemical vapor deposition method with in situ growth of CNTs using hydrothermally treated TiO2 as the starting material. The nanocomposite was characterized by powder x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectrum, and nitrogen adsorption/desorption isotherms and was investigated as an anode material for lithium-ion batteries. The underlying mechanism for the improvement was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The in situ synthesized composite showed better electrochemical performance than the pristine TiO2. The in situ formed CNTs not only supply an efficient conductive network but also keep the structural stability of the TiO2 particles, leading to improved electrochemical performance.

The role played by catalyst aggregates in the growth of carbon nanocoils (CNCs) by a chemical vapor deposition (CVD) method has been studied. The experimental results show that CNCs can be grown from the discrete aggregates on a substrate with a porous surface, while only some irregular carbon nanofibers are grown from those on a flat substrate. It is accepted from the viewpoint of mechanics that the spiral motion of a CNC should generate a torsional moment on its base that attaches to an aggregate. The catalyst particles readily expand on the flat substrate during the CVD process and form a loose aggregate, which cannot provide a strong interaction between the aggregate and the base of a carbon fiber grown from there. On the contrary, the expansion of catalyst particles in a microsized hole is restricted by the surrounding wall of the hole, leading to the formation of a compact aggregate that fixes the base of the grown fiber. A perfect CNC can be grown only under the condition that its base is firmly fixed by an aggregate that can balance the torsional moment of the CNC during its spiral growth.

Nanopillars and nanocoils fabricated by chemical vapor deposition using a focused ion beam were used to estimate bending and torsional rigidities under infinitesimal deformation and to investigate nonlinear large deformation behaviors. For the pillars, we performed bending tests using a unique double-cantilever specimen, which was made by joining two pillars together using focused electron beam deposition in a scanning electron microscope. The reproducible load–deflection curves, which were not severely disturbed by the ambiguous chuck condition of the specimens, indicated that the pillar deformation resistance decreased after the linear response (called softening), and it was dependent on the pillar diameter and the ratio of diameter to length. However, all pillars became extremely hardened at large deformation. At diameters of less than 300 nm, and at diameter/length ratios of over 10−2, this nanopillar size effect (characterized as softening) was consistently observed.

Core–shell structured Sn/carbon nanotube (CNT) was prepared by one-pot chemical vapor deposition (CVD) method in N2/C2H2 (10% C2H2) using nanosized SnO2 as the starting material. The obtained one-dimensional material is composed of a disordered carbon shell and a single-crystalline Sn nanorod core. The diameter of the Sn nanorod and the thickness of the carbon shell are around 40–50 and 4–5 nm, respectively, when the CVD reaction was carried out at 650 °C for 2 h. The core–shell structured Sn/CNT exhibits improved electrochemical performance compared with bare Sn with a diameter of around 100 nm. A reversible capacity of around 350 mAh/g can be retained after 20 cycles at 50 mA/g for Sn/CNT, while for bare Sn, the capacity drops rapidly to 100 mAh/g after the same cycles.

In this work, we compare the synthesis of germanium nanowires (GeNWs) using a highly localized heat source with GeNWs synthesized in a uniform temperature environment. With the exception of thermal environment, identical synthesis parameters were maintained in all experiments. The localized heat source, a suspended silicon microscale heater, enabled site-specific synthesis and thus the direct integration of GeNWs which is presented for the first time. The effect of heat source implementation and local temperature gradients on the resulting nanowires is assessed in terms of resulting nanowire geometry, growth rate, and quality. Overall, we note a reduction in growth rate and elevated kinking levels in locally synthesized nanowires when compared to nanowires synthesized in uniform temperature processes. The taper which typically characterizes GeNWs, however, is significantly reduced. Finally, we explore branching behavior which hints of instabilities in the synthesis process as nanowires grow away from the heat source.