Narrow Results

The effects of the sequence of technology steps of electrical contact formation between carbyne layers and metal electrodes (gold, platinum) on contact parameters were explored. Enhancements in contact parameters were achieved through thermal annealing of the samples. Contact parameters were measured by transmission line method (TLM) and impedance spectroscopy after annealing at atmospheric conditions. Lowering of contact resistivity and sheet resistance of the carbyne layer after annealing was observed for temperatures up to 150${}^{\circ }$C for palladium contacts and up to 100${}^{\circ }$C for gold contacts. It was found that exceeding these temperatures is not recommended, as higher annealing temperatures led to a reduction in the sheet resistance of the carbyne layer. Based on these findings, it can be concluded that the electrical losses at metal contacts of carbyne-based devices, with Au or Pd metallization, can be reduced through annealing. This is particularly critical in carbyne-based gas sensors, where decreasing contact resistance enhances sensitivity.

Metallization of methane (CH₄) has always been an interesting issue. Here, we report a study on the structure, metallization and superconductivity in K-doped CH₄ under pressure, based on the particle swarm optimization, density functional theory, and density functional perturbation theory. Summarizing the thermodynamical and dynamical stabilities, the electronic band structures, and the electron–phonon interaction calculations, we predicted that K-doped CH₄ in $P{2}_1∕m$ space-group is a metal and a possible superconductor in the pressure range of $70-90$ GPa. The superconducting critical temperature is about 12.7 K at 80 GPa. It was found that the charge transfer from K to CH₄ drives the metallization and mainly contributes to the electron–phonon interaction. The result confirms that CH₄ can become a metal and superconductor under the electron doping and the relative low pressure.

To explore the high-temperature superconductor at low pressures, we have investigated the crystal structures, electronic properties, and possible superconductivity in the case of methane (CH₄) doped by lithium in the pressure range of $0-100$GPa, based on the first-principles calculations. The results show that Li-intercalated CH₄ (Li_x(CH₄)${}_{1-x}$) can realize metallization and superconductivity at low pressures, even 5GPa. We find that there is a charge transfer between Li and CH₄, but the metallization is driven by the change of crystal field induce by doping instead of charge transfer. The critical temperture is predicted from 3.8K at 5GPa for LiCH₄ to 12.1K at 100GPa for Li(CH₄)₄. The low-pressure superconductivity of Li_x(CH₄)${}_{1-x}$ can be further optimized by adjusting component and pressure.

The electronic band structure, metallization, structural phase transition, and superconductivity of cubic zinc blende type GaAs and InAs are investigated. The equilibrium lattice constant, bulk modulus, and the phase transition pressure at which the compounds undergo structural phase transition from ZnS to NaCl are predicted from the total energy calculations. The density of states at the Fermi level (N(E_F)) get enhanced after metallization, which leads to the superconductivity in GaAs and InAs. The superconducting transition temperatures (T_c) of GaAs and InAs are obtained as a function of pressure for both the ZnS and NaCl structures. GaAs and InAs come under the class of pressure-induced superconductors. When pressure is increased T_c increases in both the normal and high pressure-structures. The dependence of T_c on electron–phonon mass enhancement factor λ shows that GaAs and InAs are electron–phonon-mediated superconductors. Also, it is found that GaAs and InAs retained in their normal structure under high pressure give appreciably high T_c.