Silicon Carbide Buffer Layer Research Articles

Evidence for temporary and local transition of sp2 graphite-type to sp3 diamond-type bonding induced by the tip of an atomic force microscope

Artificial diamond is created by exposing graphite to pressures on the order of 10 GPa and temperatures of about 2000 K. Here, we provide evidence that the pressure exerted by the tip of an atomic force microscope onto graphene over the carbon buffer layer of silicon carbide can lead to a temporary transition of graphite to diamond on the atomic scale. We perform atomic force microscopy with CO terminated tips and copper oxide (CuOx) tips to image graphene and to induce the structural transition. A local transition induced by the force of the tip is accompanied by local rehybridization from an sp2-bonded to an sp3-bonded local structure. Density functional theory predicts that a repulsive threshold of nN, followed by a force reduction by nN is overcome when inducing the graphite-diamond transition. The experimental observation of the third harmonic with a magnitude of about 200 fm fits well to overcoming a force barrier of F barrier ≈ 5 nN, followed by a force reduction by −F barrier and an upswing by F barrier for decreasing distances. Experimental evidence for this transition is provided by the emergence of third harmonics in the cantilever oscillation when the laterally flexible CO terminated tip exerts a large repulsive force. Probing the sample with rigid CuOx tips in the strong repulsive regime shows a strong difference in the yielding of the A versus B sites to the pressure of the tip. The large repulsive overall force of nN is only compatible with the experimental data if one assumes that the repulsive force acting on the tip when inducing the transition is compensated by a heavily increased van-der-Waals attraction of the tip due to form fitting of tip and sample by local indentation. The experiment also shows that atomic force microscopy allows to perform high pressure physics on the atomic scale.

Structure and properties of composites based on aluminum and gallium nitrides grown on silicon of different orientations with a buffer layer of silicon carbide

The microstructure and pyroelectric properties of AlxGa1-xN composite epitaxial layers grown on SiC/Si(111) and SiC/Si(110) hybrid substrates by the chloride-hydride epitaxy have been studied. The phenomenon of spontaneous formation of a system of heterojunctions consisting of periodic AlxGa1-xN layers of different composition located perpendicular to the direction of growth, was discovered during the growth of layers. Measurements of the pyroelectric coefficients of these heterostructures have shown that regardless of the orientation of the initial Si substrate and their pyroelectric coefficients have close values of the order of γ~(0.7-1)·10-10 C/cm2K. It is shown that to increase the magnitude of the pyroresponse it is necessary to deposit an AlN layer with a thickness exceeding 1 μm on the AlxGa1-xN/SiC/Si surface. This leads to record values of the pyroelectric coefficient γ~18·10-10 C/cm2K for AlN crystals and films. Keywords: silicon carbide-on-silicon substrates, chloride-hydride epitaxy, AlGaN epitaxial layers, aluminum nitride, gallium nitride, pyroelectric properties.

Effects of SiC and Resorcinol-Formaldehyde (RF) Carbon Coatings on Silicon-Flake-Based Anode of Lithium Ion Battery.

Silicon flakes of about 100 × 1000 × 1000 nm in sizes recycled from wastes of silicon wafer manufacturing processes were coated with combined silicon carbide (SiC) and graphitic (Resorcinol–Formaldehyde (RF)) carbon coatings to serve as active materials of the anode of lithium ion battery (LIB). Thermal carbonization of silicon at 1000 °C for 5 h forms 5-nm SiC encapsulating silicon flakes. SiC provides physical strength to help silicon flakes maintain physical integrity and isolating silicon from irreversible reactions with the electrolyte. Lithium diffuses through SiC before alloying with silicon. The SiC buffer layer results in uniform alloying reactions between lithium and silicon on the surface around a silicon flake. RF carbon coatings provide enhanced electrical conductivity of SiC encapsulated silicon flakes. We characterized the coatings and anode by SEM, TEM, FTIR, XRD, cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and electrical resistance measurements. Coin half-cells with combined SiC and RF carbon coatings exhibit an initial Coulombic efficiency (ICE) of 76% and retains a specific capacity of 955 mAh/g at 100th cycle and 850 mAh/g at 150th cycle of repetitive discharge and charge operation. Pre-lithiation of the anode increases the ICE to 97%. The SiC buffer layer reduces local stresses caused by non-uniform volume changes and improves the capacity retention and the cycling life.

MBE synthesis and properties of GaN NWs on SiC/Si substrate and InGaN nanostructures on Si substrate

A possibility of GaN NWs and InGaN nanostructures of a branched morphology MBE growth on SiC/Si and Si substrate has been demonstrated. It was found that the intensity of the photoluminescence spectrum of the GaN NWs on SiC/Si(111) substrate integrally more than 2 times higher than that of the best structures of GaN NWs without a buffer layer of silicon carbide. The results of morphological studies have shown that InGaN synthesis occurs in several stages. InGaN nanostructures turned out to be optically active at room temperature and have a wide radiation visible range.

Influence of Orientation of a Silicon Substrate with a Buffer Silicon Carbide Layer on Dielectric and Polar Properties of Aluminum Nitride Films

Dielectric and polar properties of aluminum nitride (AlN) thin films epitaxially grown on differently oriented silicon substrates with the p-type conduction and a buffer silicon carbide (SiC) layer and on vicinal planes are investigated. The results of studies of the polar properties by two independent methods—the dynamic pyroelectric effect and the piezoresponse force microscopy—show that the SiC buffer layer application considerably improves polar properties of the aluminum nitride thin layer.

Epitaxial Growth of Zinc Sulfide by Atomic Layer Deposition on SiC/Si Hybrid Substrates

Epitaxial films of zinc sulfide on silicon were obtained by atomic layer deposition (ALD). In order to avoid the interaction between silicon and zinc sulfide, a high-quality buffer layer of silicon carbide ~100 nm in thickness was previously synthesized on the surface of silicon by chemical substitution of atoms. High-energy electron diffraction showed that ZnS layers are epitaxial. It is proved by ellipsometric methods that the grown ZnS layers are transparent in the photon energy region up to 3 eV, which is crucial for applications in optoelectronics.

Co-deposition of diamond and β-SiC by microwave plasma CVD in H2-CH4-SiH4 gas mixtures

The co-deposition of diamond and silicon carbide (SiC) was realized in a microwave plasma using H2-CH4-SiH4 mixtures at enhanced microwave power density of up to 150 W/cm3, and SiC/diamond composite films on (100) Si substrates were produced. The growth parameters were selected to ensure almost equal deposition rates of ~0.3 μm/h for both phases. Composite films were formed either directly on Si surface, or on a buffer (nucleation) layer of SiC or diamond, preliminary deposited on the Si substrate. The film structure has been characterized by SEM, XRD, Raman and PL spectroscopy. It was confirmed that the silicon carbide phase in the composite is the cubic polytype β-SiC (3C-SiC) with the presence of only a small fraction of the hexagonal polytype, while the diamond is in well-faceted microcrystalline form. Diamond grains are Si-doped as was evidenced by the strong photoluminescence of silicon-vacancy color centers. Also, minor inclusions of amorphous sp2 carbon and of trans-polyacetylene (t-PA) were detected in the β-SiC phase. The overall crystalline quality of the composite is high, as evidenced by narrow Raman peaks both for diamond and β-SiC. Our results show, that with an appropriate choice of growth parameters, particularly SiH4/CH4 ratio, high-quality films of Si-doped diamond, silicon carbide, SiC-diamond composite, and combinations of these structures can be synthesized in a single process. Prime novelty statementThe co-deposition of diamond and SiC was realized by microwave plasma CVD using H2-CH4-SiH4 mixtures at enhanced microwave power density; β-SiC/diamond composite films were produced with high crystalline quality on (100) Si substrates.

Cycloaddition reactions on epitaxial graphene

By means of first principles calculations we studied the occurrence of cycloaddition reactions on the buffer layer of silicon carbide. Interestingly, the presence of the substrate favors the 1,3 cycloaddition instead of the [2+2] or [4+2] ones.

Эпитаксиальный рост cульфида цинка методом молекулярного наслаивания на гибридных подложках SiC/Si

In this work, we obtained epitaxial films of zinc sulfide on silicon by the ALD method. To avoid the interaction between silicon and zinc sulphide on the silicon surface, a high-quality buffer layer of silicon carbide ~ 100 nm thick was preliminarily synthesized by chemical substitution of atoms. The diffraction of high energy electrons showed that the ZnS layers are epitaxial. Using ellipsometric methods, it has been proved that the grown ZnS layers are transparent in the photon energy region up to 3 eV, which is of crucial importance for applications in optoelectronics.

Новый метод получения объемных кристаллов AlN, GaN и AlGaN с использованием гибридных подложек SiC/Si

The paper presents the main provisions of the new method of growing bulk, with a thickness of 100 μm or more, single-crystal AlN, AlGaN and GaN films on silicon poles with a silicon carbide buffer layer with their subsequent separation from the Si substrate. The main essence of this method is the combination of the method of chloride-hydride epitaxy, which ensures high growth rates of III-nitride layers using as substrate for growth, Si substrate with a buffer layer of a nanoscale atomic SiC film. The Si substrate with a SiC layer grown by the substitution method has a number of structural, physical, and chemical features as compared to SiC layers grown on Si by standard methods. It is shown that it is this feature that makes it possible to grow on its surface thick, uncracked layers of AlN, AlGaN and GaN, followed by their simple separation from the substrate. In this work, single-crystal uncracked layers were grown: AlN up to 300 microns thick; AlGaN thickness up to 400 microns; GaN thickness up to 200 microns; GaN semipolar (112 ̅4) orientation up to 35 microns.

Polycrystalline films of phosphors Cd(1-x-y-z) (CuyAgz) ZnxS on the silicon substrate with the silicon carbide buffer layer: structure and properties

Polycrystalline films of phosphors Cd(1-x-y-z) (CuyAgz) ZnxS on the silicon substrate with the silicon carbide buffer layer: structure and properties

Влияние ориентации кремниевой подложки с буферным подслоем карбида кремния на диэлектрические и полярные свойства пленок нитрида алюминия

The dielectric and polar properties of thin films of aluminum nitride (AlN) epitaxially grown on variously oriented p-type silicon substrates with a buffer sublayer of silicon carbide (SiC), as well as on vicinal planes, are studied. According to the results of studies of the polar properties by two independent methods — the dynamic pyroelectric effect and piezoelectric force microscopy, it was shown that the use of a SiC buffer layer significantly improves the polar properties of thin layers of aluminum nitride.

MBE growth and properties of GaAs, AlGaAs and InAs nanowires on SiC/Si(111) hybrid substrate

The possibility of GaAs, AlGaAs and InAs nanowires MBE growth on a silicon substrate with a nanometer silicon carbide buffer layer has been demonstrated for the first time. Under the same experimental conditions (including the same composition) the diameter of the nanowires is smaller than diameter of nanowires grown on silicon substrate. Based on the photoluminescence and TEM analysis it was suggest that when AlGaAs/SiC/Si NWs are grown, a physical complex structure is formed.

MBE Growth and Optical Properties of GaN, InN, and A3 B5 Nanowires on SiC/Si(111) Hybrid Substrate

The possibility of GaN, InN, and A3B5 nanowires MBE growth on a silicon substrate with a nanoscale SiC buffer layer has been demonstrated. Optical studies indicated a higher structural quality GaN NWs compared with the best structures of GaN NWs without silicon carbide buffer layer. The diameter of A3B5 NWs is smaller than diameter of similar NWs which were grown on a silicon substrate, because of higher lattice mismatch. In particular, InAs NWs diameter was evaluated as little as 10 nm, one of the smallest ever demonstrated for this NWs system.

MBE growth of thin AlGaAs nanowires with a complex structure on strongly mismatched SiC/Si(111) substrate

The possibility of AlGaAs nanowires MBE growth on a silicon substrate with a nanometer silicon carbide buffer layer was demonstrated for the first time. Under the same experimental conditions (including the same composition), the diameter of the AlGaAs/SiC/Si nanowires are smaller than nanowires diameter grown on a silicon substrate. Based on the photoluminescence analysis suggests that when AlGaAs/SiC/Si NWs are grown, a physical complex structure appears due to the self-organized formation of regions with different molar fractions of aluminum in the solid solution.

Study of the Anisotropic Elastoplastic Properties of β-Ga2O3 Films Synthesized on SiC/Si Substrates

The structural and mechanical properties of gallium oxide films grown on silicon crystallographic planes (001), (011), and (111) with a buffer layer of silicon carbide are investigated. Nanoindentation was used to study the elastoplastic properties of gallium oxide and also to determine the elastic recovery parameter of the films under study. The tensile strength, hardness, elasticity tensor, compliance tensor, Young’s modulus, Poisson’s ratio, and other characteristics of gallium oxide were calculated using quantum chemistry methods. It was found that the gallium oxide crystal is auxetic because, for some stretching directions, the Poisson’s ratio takes on negative values. The calculated values correspond quantitatively to the experimental data. It is concluded that the elastoplastic properties of gallium oxide films approximately correspond to the properties of bulk crystals and that a change in the orientation of the silicon surface leads to a significant change in the orientation of gallium oxide.

MBE growth and Structural Properties of InAs and InGaAs Nanowires with Different Mole Fraction of In on Si and Strongly Mismatched SiC/Si(111) Substrates

The possibility of InAs nanowires MBE growth on silicon (111) substrates with a nanometer buffer layer of silicon carbide has been demonstrated for the first time. The NWs diameter turned out to be smaller than on the silicon substrate—the minimum of NWs diameter was less than 10 nm. In addition, dependence of structural properties of InGaAs nanowires on composition was studied.

Optical Properties of GaN Nanowires Grown by MBE on SiC/Si(111) Hybrid Substrate

The aim of this work is to demonstrate the fundamental possibility of Si-doped GaN nanowires growth on the buffer layer of silicon carbide on silicon substrate and to investigate the optical characteristics of this structures.

Structural and elastoplastic properties of $$\upbeta $$ β - $$\hbox {Ga}_{2}\hbox {O}_{3}$$ Ga 2 O 3 films grown on hybrid SiC/Si substrates

Structural and mechanical properties of gallium oxide films grown on (001), (011) and (111) silicon substrates with a buffer layer of silicon carbide are studied. The buffer layer was fabricated by the atom substitution method, i.e., one silicon atom per unit cell in the substrate was substituted by a carbon atom by chemical reaction with carbon monoxide. The surface and bulk structure properties of gallium oxide films have been studied by atomic-force microscopy and scanning electron microscopy. The nanoindentation method was used to investigate the elastoplastic characteristics of gallium oxide, and also to determine the elastic recovery parameter of the films under study. The ultimate tensile strength, hardness, elastic stiffness constants, elastic compliance constants, Young’s modulus, linear compressibility, shear modulus, Poisson’s ratio and other characteristics of gallium oxide have been calculated by quantum chemistry methods based on the PBESOL functional. It is shown that all these properties of gallium oxide are essentially anisotropic. The calculated values are compared with experimental data. We conclude that a change in the silicon orientation leads to a significant reorientation of gallium oxide.

MBE growth and structural properties of InAs and InGaAs nanowires with different mole fraction of In on Si and strongly mismatched SiC/Si(111) substrates

AbstractThe possibility of InAs nanowires MBE growth on silicon (111) substrates with a nanometer buffer layer of silicon carbide has been demonstrated for the first time. The NWs diameter turned out to be smaller than on the silicon substrate—the minimum of NWs diameter was less than 10 nm. In addition, dependence of structural properties of InGaAs nanowires on composition was studied.