Narrow Results

In this study, we conduct calculations of Ag- and Sr-doped in 3C-SiC using density-functional. To model defective systems, we dope Ag and Sr atoms in substitutional and interstitial sites. We use a supercell model consisting of 64 atoms and relax all atoms so that the atomic forces are less than $5.0\times 10^{-3}$eV/Å. Then, we calculate the defect formation energies for each system. The calculated defect formation energies are 5.67eV and 7.77eV for substitutional Ag and Sr, respectively. In the case of the interstitial sites, the lowest defect formation energies are 10.36eV (Ag) and 14.63eV (Sr). We conclude that Ag and Sr are energetically favorable to be trapped at the substitutional site. Furthermore, the substitutional configuration of Ag is more stable than that of Sr. We check the converged value of the defect formation energies using a 216-site supercell and find that the energy difference is only 0.21eV. Thus, the 64-atom supercell is reliable for the calculations.

An insight into electronic structure and optical feature of S-adsorbed 3C–SiC (111) surface is carried out employing first-principles calculation. It is found that the ${\mathrm{\text{T}}}_{\mathrm{\text{o}}}$ and B position systems with adsorption energies of 3.880 and 3.895, respectively, are relatively stable compared to the ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ and C systems. Impurity energy levels are present near Fermi level in C and ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ position adsorption systems and the band-gap decreases obviously in the two systems. A raindrop-like electron cloud of S atom can be observed in ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ adsorption system and the order of the chemical bond strength in the adsorption system is $(\mathrm{\text{B}},{\mathrm{\text{T}}}_{\mathrm{\text{o}}})>{\mathrm{\text{T}}}_{\mathrm{\text{w}}}>\mathrm{\text{C}}$. The B and ${\mathrm{\text{T}}}_{\mathrm{\text{o}}}$ adsorption systems have good light permeability in the visible and infrared regions, while the C and ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ adsorption systems are relatively suitable as dielectric materials and have high service life when they as devices in the ultraviolet region.

This paper presents the formation of graphene and its application to hydrogen sensors. In this work, the graphene was synthesized by annealing process of 3C-SiC thin films with Ni transition layer. The Ni film was coated on a 3C-SiC layer grown thermal oxided Si substrates and used extracts of the substrate's carbon atoms under rapid thermal annealing (RTA). Various parameters such as ramping speed, annealing time and cooling rate were evaluated for the optimized combination allowed for the reproducible synthesis of graphene using 3C-SiC thin films. Transfer process performed by Ni layer etching in HF solution and transferred graphene onto SiO₂ shows the I_G/I_D ratio of 2.73. Resistivity hydrogen sensors were fabricated and evaluated with Pd and Pt nanoparticles in the room temperature with hydrogen range of 10–50 ppm. The response factor of devices with the Pd catalyst was 1.3 when exposed to 50 ppm hydrogen and it is able to detect as low as 10 ppm hydrogen at room temperature.