Combining diamond and two-dimensional materials is attracting increasing attention for synergic effects that have the best of both worlds. Applications range from electronics and quantum technologies to catalysis, energy conversion, and biosensors. Here, heterostructures based on hydrogenated diamond microcrystalline thin films with attached MoS2 nanosheets are formed by a single-zone annealing at atmospheric pressure. By varying the process parameters, MoS2 sheets are controllably synthesized in a vertical or horizontal orientation with respect to the diamond grain facets, which leads to a pronounced impact on the electronic and optoelectronic properties of the heterostructures. Raman, SEM, AFM, KPFM, and SKP analyses show the influence of the MoS2 orientation and thickness on the work function, surface potential, spatially and spectrally resolved photovoltage, and charge transfer kinetics. The aligned growth of MoS2 nanosheets and their properties are elucidated by molecular mechanics and time-dependent DFT calculations, which explain the mechanism of the assembly and the related optoelectronic effects in a straightforward way. The major switching point occurs precisely at 11 nm of the MoS2 thickness/length. The highest photoresponse of 350 meV and favorable charge transfer are observed for the vertical MoS2 arrangement on diamond, yet without a covalent bond. The results and theoretical model hint at broader implications beyond the MoS2-diamond system.

The in situ combination of plasma-enhanced chemical vapor deposition (PECVD) and vacuum evaporation in the same vacuum chamber allowed us to integrate germanium nanocrystals (Ge NCs) into hydrogenated amorphous silicon carbide (a-SiC:H) thin films deposited from monomethyl silane diluted with hydrogen. Transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy were used for the microscopic characterization, while photothermal deflection spectroscopy (PDS) and near-infrared photoluminescence spectroscopy (NIR PL) were for optical characterization. The presence of Ge NCs embedded in the amorphous a-Si:C:H thin films was confirmed by TEM and EDX. The embedded Ge NCs increased optical absorption in the NIR spectral region. The quenching of a-SiC:H NIR PL due to the presence of Ge indicates that the diffusion length of free charge carriers in a-SiC:H is in the range of a few tens of nm, an order of magnitude less than in a-Si:H. The optical properties of a-SiC:H films were degraded after vacuum annealing at 550 °C.

Due to the high surface to volume ratio, the particles' surface properties modification defines its properties in general, which is crucial for their use.From this point of view, plasma processing or high temperature annealing can be considered as the universal techniques for efficient modification of materials in the form of powder.In this study, the silicon dioxide microparticles have been treated in a hydrogen, oxygen or vacuum by low temperature plasma or annealing.The change of SiO2 microparticles properties was investigated by photoluminescence spectroscopy at room and low temperature.High temperature annealing in hydrogen induced under UV excitation photoluminescence in the near UV and visible light indicating the change of defect states on the surface of the microparticles.We believe that observed findings clearly demonstrate useful method for analysis of SiO2 microparticles surface modification attractive also for fundamental research.

Abstract Waste glasses based on silicon dioxide (silica) belong to one of the most demanded secondary raw materials. Besides the glass industry, with strict requirements for source materials, silica-based granular materials from waste glasses are considered suitable for use as fillers in alkali-activated cement-based composites. However, due to variations of ground waste glass powder composition and properties a comprehensive characterization is often needed. This study investigated commercially available silica-based powders by scanning electron microscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and Fourier transform infrared Raman spectroscopy, zeta-potential and pH measurements, etc. The differences found in the non-silica impurities composition and structure of SiO2 particles (amorphous vs crystalline) were considered as determinative factors that will affect particles’ interaction with water and cement binder. The observed results provide a fundamental background and will contribute to a better understanding and explanation of the silica-based secondary raw materials interaction reactions in concrete or mortar.

Recycled soda-lime glass powder is a sustainable material that is also often considered a filler in cement-based composites. The changes in the surface properties of the glass particles due to the treatments were analyzed by X-ray photoelectron spectroscopy (XPS) and optical spectroscopy. We have found that there is a relatively high level of carbon contamination on the surface of the glass particles (around 30 at.%), so plasma technology and thermal annealing were tested for surface cleaning. Room temperature plasma treatment was not sufficient to remove the carbon contamination from the surface of the recycled glass particles. Instead, the room temperature plasma treatment of recycled soda-lime glass particles leads to a significant enhancement in their room temperature photoluminescence (PL) by increasing the intensity and accelerating the decay of the photoluminescence. The enhanced blue PL after room-temperature plasma treatment was attributed to the presence of carbon contamination on the glass surface and associated charge surface and interfacial defects and interfacial states. Therefore, we propose blue photoluminescence under UV LED as a fast and inexpensive method to indicate carbon contamination on the surface of glass particles.

Abstract We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.

Abstract Zinc oxide exhibits high electron mobility, wide 3.3eV band gap, ability to sustain large electric fields, relatively low electronic noise, and strong luminescence. These properties make ZnO invaluable for a broad range of applications. To optimize them, it is important to study the influence of annealing on ZnO properties under various conditions. In this work we compare the infrared Raman (IR Raman, 1064 nm laser excitation, 70-3500 cm1 spectral range, 1cm1 spectral resolution) and photoluminescence (PL, 360 nm UV LED excitation, 375-700 nm spectral range, 1 ns time resolution) optical spectra of as the received and annealed ZnO single crystals. The annealing has been done in oxidizing (air) and reducing (hydrogen) atmosphere at 350, 500 and 700°C. The Raman spectra consist of two characteristic peaks at 99 and 438 cm-1 associated with the sublattice oscillations of Zn and O, respectively, and a broad PL band in the visible spectrum with mean time decay about 10 microseconds. The optical measurements are correlated with the topographical information obtained by atomic force microscopy (AFM). The result shows the ZnO single crystals can be enhanced in terms of PL intensity, decay time and optical scattering by annealing in the oxidizing and consequential reducing atmosphere. The trends are more profoundly on the O-face. Both treatments lead to greater surface roughness, particularly in the case of hydrogen atmospheres, but without any observable change in the IR Raman spectra.

The study delves into the impact of waste silicon-based materials on the mechanical characteristics of the resulting cement pastes. The investigation uses Portland cement CEM I 42.5R in conjunction with silicon-based waste materials sourced from the packaging industry, specifically from Recifa, a.s. Variations between the sample groups arise from differences in the concentration of silicon-based materials and the method of surface treatment. The inquiry seeks to assess the effects of two distinct levels of Si-based material incorporation, namely 10 wt. % and 20 wt. %, along with plasma treatment involving two different gases: oxygen (O2) and hydrogen (H2). The mechanical attributes under scrutiny encompass compressive and flexural strengths. The evaluation of mechanical properties is carried out on samples aged 28 days, with dimensions measuring 20 × 20 × 100 mm.

Nanodiamonds (NDs) containing optically active centers have gained significant relevance as the material of choice for biological, optoelectronic, and quantum applications. However, current production methods lag behind their real needs. This study introduces two CVD-based approaches for fabricating NDs with optically active silicon-vacancy (SiV) color centers: bottom-up (BU) and top-down (TD) methods. The BU approach generates nanoporous diamond films with a core-shell structure, while the TD method employs molten-salt thermal etching to create uniform porous structures from nanocrystalline diamond films. Comprehensive characterization using advanced techniques revealed distinct morphologies and optical properties for each approach. The BU method yielded higher-quality diamond phases with top-surface incorporation of SiV centers, while the TD method demonstrated efficient nondiamond phase removal. Ultrasonic disintegration of both porous films produced NDs ranging from 40 to 500 nm, with unique morphologies characteristic of each approach. Photoluminescence measurements confirmed SiV centers (738 nm) in all NDs, exhibiting sensitivity to surface terminations, particularly in BU samples. Temperature-resolved spectroscopy shows the potential of the fabricated NDs for nano thermometry over a wide range of temperatures up to 100 degrees C. The zero-phonon line shows 0.022 +/- 0.003 nm/K sensitivity, while the line width exhibits 0.068 +/- 0.004 nm/K broadening. The presented BU and TD methods offer significant advantages over existing techniques, including streamlined production processes, high-yield ND synthesis with tailored properties, and the potential for scalable, cost-effective manufacturing.

In the paper, we prepared a hydrogenated nanocrystalline diamond (NCD-H) film by the chemical vapor deposition (CVD) method. A variable degree of NCD-H surface destruction and surface graphitization was achieved by Ar ion bombardment using monoatomic beam (Ar+) and cluster ion beam (ArCIB). Bombardment with ArCIB manifests itself by the formation of a very thin altered layer on the surface of NCD-H accompanied by no Ar atoms embedded in the surface region. In contrast, bombardment with Ar+ beam leads to the creation of thicker, homogeneous altered layer characterized by dominating C sp2 hybridization, by the embedded Ar atoms, and by the reduced dimensions of diamond grains located near the surface of the samples. A combination of multiple microscopy and spectroscopy methods enabled us to evaluate the contribution of the C-Hx bonds to the asymmetry of the C 1s core level line shape and to measure the H concentration on the surface. The limitation of Auger spectroscopy (D-parameter) analysis for the sp2/sp3 phase concentration measurement on rough, NCD-H surface is demonstrated. The controllable amorphization or graphitization of diamond surface can further extend its functionality in detectors, electrochemical sensing or supercapacitor uses.

Diamond films are multifunctional materials with a wide range of extraordinary properties and a high application potential in various fields. In this work, we investigate the low temperature (< 500 degrees C) diamond films chemical vapor deposition on fused silica substrates realized in two different focused microwave plasma systems, i.e. a multimode clamshell cavity reactor ( MCC) and a rotational ellipsoid cavity (REC) reactor. During the experiments, the methane to hydrogen ratio, in the hydrogen-rich process gas mixture, varied from 1 % to 15 % for MCC and from 1 % to 9 % for the REC reactor. For both deposition systems, the methane increase led to an increase in the diamond growth rate, e.g. it raised at least by a factor of 2.6 for the MCC reactor. Furthermore, the MCC reactor also allowed the growth of well-shaped diamond crystals at a methane to hydrogen ratio as high as 15 %. This finding is in good agreement with the Raman shift measurements, which also revealed a low content of non-diamond phases in the films making the MCC reactor more preferential for industrial uses. Moreover, the enhanced diamond growth at low temperatures is further advantageous for overcoating fused silica as well as thermally sensitive substrates which altogether opens new vistas for diamond application in optically related fields (optical elements, photonic crystals, sensors).

Diamond thin films can be, at a relatively low-cost, prepared with a high-density of light-emitting negatively charged silicon vacancy (SiV) centers, which opens up the possibility of their application in photonics or sensing. The films are composed of diamond grains with both the SiV centers and sp2-carbon phase, the ratio of these two components being dependent on the preparation conditions. The grain surface and the sp2-related defects might act as traps for the carriers excited within the SiV centers, consequently decreasing their internal photoluminescence (PL) quantum efficiency. Here, we show that in a 300 nm thick polycrystalline diamond film on a quartz substrate, the SiV centers in the diamond grains possess similar temperature-dependent (13-300 K) PL decay dynamics as the SiV centers in monocrystalline diamond, which suggests that most of the SiV centers are not directly interconnected with the defects of the diamond thin films, i.e. that the carriers excited within the centers do not leak into the defects of the film. The activation energy ΔE = 54 meV and the attempt frequency α = 2.6 were extracted from the measured data. These values corresponded very well with the published values for SiV centers in monocrystalline diamond. We support this claim by measuring the transient absorption via a pump and probe technique, where we separated the nanosecond recombination dynamics of carriers in SiV centers from the picosecond decay dynamics of polycrystalline diamond defects. Our results show that PL emission properties of SiV centers in polycrystalline diamond thin films prepared via chemical vapor deposition are very similar to those in monocrystalline diamond thereby opening the door for their application in diamond photonics and sensing.

Thin-film photovoltaic (PV) cells based on a-Si:H have been and still are optimized. In this work, we present PV cells based on a-SiC:H alloys with low carbon content [1] deposited (compared to PV cells based only on a-Si:H) at elevated temperatures. The increased deposition temperature is in line with the deposition temperatures for consequent diamond layer deposition and helps to stabilize the achieved energy conversion efficiency. Thin diamond layers act as optically transparent material with a wide bandgap (5.47 eV) and a high optical refractive index (2.41). The outstanding properties of diamond are high chemical resistance, high mechanical hardness, and high thermal conductivity. Technological processes make it possible to diverge diamond from nanocrystalline to microcrystalline layers. The diamond crystal size governs the efficiency of the scattering of the incident light and its increased absorption in the connected structure of the PV cell. Both of these properties - high thermal conductivity and optimized layer roughness - are excellent prerequisites for the new structuring of thin-film PV cells. By efficient heat dissipation, PV cells operate in a mode of lower temperatures and thus higher energy conversion efficiency, even in the systems loaded with highly concentrated solar energy.

Diamond is recognized as one of the most promising wide bandgap materials for advanced electronic applications. However, for many practical uses, hybrid diamond growth combining metal electrodes is often demanded. Here, we present the influence of thin metal (Ni, Ir, Au) layers on diamond growth by microwave plasma chemical vapor deposition (MWCVD) employing two different concepts. In the first concept, a flat substrate (GaN) was initially coated with a thin metal layer, then exposed to the diamond MWCVD process. In the second concept, the thin diamond film was firstly formed, then it was overcoated with the metal layer and finally, once again exposed to the diamond MWCVD. It should be mentioned that this concept allows the implementation of the metal electrode into the diamond bulk. It was confirmed that the Ni thin films (15 nm) hinder the formation of diamond crystals resulting in the formation of an amorphous carbon layer. Contrary to this finding, the Ir layer resulted in a successful overgrowth by the fully closed diamond film. However, by employing concept 2 (ie hybrid diamond/metal/diamond composite), the thin Ir layer was found to be unstable and transferred into the isolated clusters, which were overgrown by the diamond film. Using the Au/Ir (30/15 nm) bilayer system stabilized the metallization and no diamond growth was observed on the metal layer.

The present study investigates the effect of an oxidized nanocrystalline diamond (O-NCD) coating functionalized with bone morphogenetic protein 7 (BMP-7) on human osteoblast maturation and extracellular matrix mineralization in vitro and on new bone formation in vivo. The chemical structure and the morphology of the NCD coating and the adhesion, thickness and morphology of the superimposed BMP-7 layer have also been assessed. The material analysis proved synthesis of a conformal diamond coating with a fine nanostructured morphology on the Ti6Al4V samples. The homogeneous nanostructured layer of BMP-7 on the NCD coating created by a physisorption method was confirmed by AFM. The osteogenic maturation of hFOB 1.19 cells in vitro was only slightly enhanced by the O-NCD coating alone without any increase in the mineralization of the matrix. Functionalization of the coating with BMP-7 resulted in more pronounced cell osteogenic maturation and increased extracellular matrix mineralization. Similar results were obtained in vivo from micro-CT and histological analyses of rabbit distal femurs with screws implanted for 4 or 12 weeks. While the O-NCD-coated implants alone promoted greater thickness of newly-formed bone in direct contact with the implant surface than the bare material, a further increase was induced by BMP-7. It can be therefore concluded that O-NCD coating functionalized with BMP-7 is a promising surface modification of metallic bone implants in order to improve their osseointegration.

Diamond attracts the interest of researchers from different fields due to its extraordinary properties.However, many applications demand diamond films over large areas hence limiting usage of natural diamonds.Here we compare two microwave (2.45 GHz) plasma systems with ellipsoidal and multimode clamshell cavity for diamond synthesis by chemical vapor deposition.We use H2/CH4/CO2 gas mixture for diamond film deposition on Si <100> wafers.Both systems are capable of high pressure (up to 20 kPa) operation and high growth rates (several µm/h).We compare the cavity systems from the point of diamond quality (Raman shift measurement), substrate size (2" versus 4") and grown film homogeneity together with surface morphology (SEM), deposition rate and parasitic doping levels (photoluminescence).For instance, we show that by using the multimode operation of the clamshell cavity system and specially design sample holder, it is possible to sustain a plasma in a cavity and reach good enough process reproducibility and diamond film quality over 4-inch substrates.We discuss effects of the cavity design on deposited layers for large area applications of diamond such as thermal management, electrodes and sensor arrays fabrication, photoluminescence, photonics and light sources.

The effect of silicon oxynitride (SiON) layer on the thermally-induced stress of diamond-coated AlGaN/GaN heterostructures was studied by Raman and SIMS spectroscopy. Diamond films (0.8 or 2.8 mu m in thickness) were grown by MWCVD on selected areas of AlGaN/GaN/Si substrates with SiON interlayer. The stress in diamond became tensile for the thinner strip in the range of 0 - 0.5 GPa and compressive for the thicker strip in the range of -0.6 - -0.1 GPa both measured at temperatures ranging from 50 to 400 degrees C. The applied SiON interlayer positively influenced the induced stress (Delta stress decreased by about 0.14 GPa compared to the sample without SiON) independently on the thickness of the diamond film. SIMS depth profiling was applied to analyse the influence of diamond CVD on the AlGaN/GaN interface of SiON passivated samples. As observed, the hydrogen and carbon atoms were trapped in the SiON which acted as a stop layer.

A unique composite nanodiamond-based porous material with a hierarchically-organized submicron-nano-structure was constructed for potential bone tissue engineering. This material consisted of submicron fibers prepared by electrospinning of silicon oxide (SiOx), which were oxygen-terminated (O-SiOx) and were hermetically coated with nanocrystalline diamond (NCD) films. The NCD films were then terminated with hydrogen (H-NCD) or oxygen (O-NCD). The materials were tested as substrates for the adhesion, growth and osteogenic differentiation of human osteoblast-like Saos-2 cells. The number and the spreading area of the initially adhered cells, their growth rate during 7 days after seeding and the activity of alkaline phosphatase (ALP) were significantly higher on the NCD-coated samples than on the uncoated O-SiOx samples. In addition, the concentration of type I collagen was significantly higher in the cells on the O-NCD-coated samples than on the bare O-SiOx samples. The observed differences could be attributed to the tunable wettability of NCD and to the more appropriate surface morphology of the NCD-coated samples in contrast to the less stable, rapidly eroding bare SiOx surface. The H-NCD coatings and the O-NCD coatings both promoted similar initial adhesion of Saos-2 cells, but the subsequent cell proliferation activity was higher on the O-NCD-coated samples. The concentration of beta-actin, vinculin, type I collagen and alkaline phosphatase (ALP), the ALP activity, and also the calcium deposition tended to be higher in the cells on the O-NCD-coated samples than on the H-NCD-coated samples, although these differences did not reach statistical significance. The improved cell performance on the O-NCD-coated samples could be attributed to higher wettability of these samples (water drop contact angle less than 10°), while the H-NCD-coated samples were hydrophobic (contact angle >70°). NCD-coated porous SiOx meshes can therefore be considered as appropriate scaffolds for bone tissue engineering, particularly those with an O-terminated NCD coating.