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Register a new userHigh performance of generating and transporting hot carriers in plasmonic TiN: A first-principles study
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Promoting performance of generation and transport of hot carriers in metal/semiconductor junctions is critical for harvesting energy of hot carriers. However, the low injection efficiency of hot carriers generated in the commonly used noble metals such as Au hinder the applications of hot-carrier devices. Here, we proposed that metallic TiN might be a better plasmonic material than the noble metals for generating and transporting hot carriers, based on first-principles calculations and Monte Carlo simulations. For the TiN/TiO2 junction, the concentration of hot carriers near the Fermi level is high, the lifetime and mean free path of the hot carriers are long, and the injection efficiency is large. The optimal injection efficiency could be achieved in a core/shell cylindrical TiN/TiO2 junction with the thickness of TiN ~ 5 nm and the incident photon energy ~ 0.6 eV.
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Using density functional theory (DFT) based first principles calculations, we show that the preferred interfacial plane orientation relationship is determined by the strength of bonding at the interface. The thermodynamic stability, and the ideal tensile and shear strengths of Cu/TiN and Al/TiN interfaces are calculated. While there is a strong orientation relation (OR) preference for Al/TiN interface, there is no OR preference for Cu/TiN interface. Both the ideal tensile and shear strengths of Cu/TiN interfaces are lower than those of bulk Cu and TiN, suggesting such interfaces are weaker than their bulk components. By comparison, the ideal strengths of Al/TiN interface are comparable to the constituents in the bulk form. Such contrasting interfaces can be a test-bed for studying the role of interfaces in determining the mechanical behavior of the nanolayered structures.
This article reports the study of SnO by using the first-principles pseudopotential plane-wave method within the generalized gradient approximation (GGA). We have calculated the structural, elastic, electronic and optical of SnO under high pressure. The elastic properties such as the elastic constants Cij bulk modulus, shear modulus, Young modulus, anisotropic factor, Pugh ratio, Poisson ratio are calculated and analyzed. Mechanical stability of SnO at all pressure are confirmed by using Born stability criteria in terms of elastic constants and are associated with ductile behaviour based on G/B ratios. It is also found that SnO exhibits very high anisotropy. The energy band structure and density of states are also calculated and analyzed. The results show the semiconducting and metallic properties at 0 (zero) and high pressure, respectively. Furthermore, the optical properties such as dielectric function, refractive index, photoconductivity, absorption coefficients, loss function and reflectivity are also calculated. All the results are compared with those of the SnO where available but most of the results at high pressure are not compared due to unavailability of the results.
We theoretically investigate how each orbital and valley play a role for high thermoelectric performance of SnSe. In the hole-doped regime, two kinds of valence band valleys contribute to its transport properties: one is the valley near the U-Z line, mainly consisting of the Se-$p_z$ orbitals, and the other is the one along the $Gamma$-Y line, mainly consisting of the Se-$p_y$ orbitals. Whereas the former valley plays a major role in determining the transport properties at room temperature, the latter one also offers comparable contribution and so the band structure exhibits multi-valley character by increasing the temperature. In the electron-doped regime, the conduction band valley around the $Gamma$ point solely contributes to the thermoelectric performance, where the quasi-one-dimensional electronic structure along the $a$-axis is crucial. This study provides an important knowledge for the thermoelectric properties of SnSe, and will be useful for future search of high-performance thermoelectric materials.
Based on the exact muffin-tin orbitals (EMTOs), we developed a first-principles method to calculate the current operators and investigated the anomalous Hall effect in bcc Fe as an example, with which we successfully separated the skew scattering contribution from the side jump and intrinsic contributions by fitting the scaling law with the introduction of sparse impurities. By investigating the temperature dependence of the anomalous Hall effect in bulk Fe, we predicted a fluctuated anomalous Hall angle as a function of temperature when considering only phonons, which, in the future, can be measured in experiments by suppressing magnon excitation, e.g., by applying a high external magnetic field.
In a latest experimental advance, graphene-like and insulating BeO monolayer was successfully grown over silver surface by molecular beam epitaxy (ACS Nano 15(2021), 2497). Inspired by this accomplishment, in this work we conduct first-principles based simulations to explore the electronic, mechanical properties and thermal conductivity of graphene-like BeO, MgO and CaO monolayers. The considered nanosheets are found to show desirable thermal and dynamical stability. BeO monolayer is found to show remarkably high elastic modulus and tensile strength of 408 and 53.3 GPa, respectively. The electronic band gap of BeO, MgO and CaO monolayers are predicted to be 6.72, 4.79, and 3.80 eV, respectively, using the HSE06 functional. On the basis of iterative solutions of the Boltzmann transport equation, the room temperature lattice thermal conductivity of BeO, MgO and CaO monolayers are predicted to be 385, 64 and 15 W/mK, respectively. Our results reveal substantial decline in the electronic band gap, mechanical strength and thermal conductivity by increasing the weight of metal atoms. This work highlights outstandingly high thermal conductivity, carrier mobility and mechanical strength of insulating BeO nanosheets and suggest them as promising candidates to design strong and insulating components with high thermal conductivities.
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