| Collective oscillations of conduction electrons are excited when incident light illuminates the surface of nanomaterials,also known as surface plasmons(SPs),and consequently a series of products such as local field enhancement and hot carriers.There are many limitations to the practical applications based on SPs:the strong Landau relaxation decay and scattering effects in noble metal materials lead to high propagation losses of SPs,and the scarcity of noble metals is not conducive to sustainable development;there are very few plasmonic materials with the visible response,which limits the development of optoelectronic systems based on solar energy conversion.Therefore,the exploration of alternative noble metal plasmonic materials with low loss and broadband strong response has become an important research direction for the practice of SPs.Further,hot carriers are excited by Landau relaxation of SPs in metallic materials or are generated by single-particle photoexcitation in semiconductor materials are typical practices based on solar energy conversion.Low generation efficiency and high scattering loss of hot carriers greatly reduce the efficiency of hot carrier systems.Therefore,understanding the generation and transport of hot carriers at the microscopic level and quantifying them accurately will help to achieve precise optimization of hot carrier system efficiency.Understanding the microphysical mechanism of nonradiative decay of SPs is the basis for solving the practical problems of SPs and hot carriers.First,this thesis quantifies the thermal decay of SPs at low frequencies based on the Drude theory.Given the limitations of the Drude model for the response of interband electronic transitions at high frequencies,this thesis further quantifies the Landau relaxation decay of SPs based on quantum mechanical theory,including interband and phonon-assisted electronic transitions,and so achieves the quantitative calculation of the hot carrier generation efficiency.Finally,the relaxation time characterizing the decay of phonon-assisted electronic transitions is obtained based on the Eliashberg spectral function,and by combining the relaxation time of the Drude effect and the interband electronic transitions response,a comprehensive dielectric function calculation model quantifying the response of the surface plasmon is obtained.To avoid the dependence on the accuracy of experimental data and empirical parameters for calculating SPs and hot carriers’ properties,a high-performance calculation(OPTx)for quantization of optical response,SPs,and hot carriers’ properties is done in a Linux system based on first principles.Therefore,from the perspective of sustainable development based on solar energy conversion utilization,this thesis systematically investigates the SPs and hot carrier properties in noble metal alloy materials,high-temperature materials X(Ti,V)N,2D borophene monolayers,and semiconductor materials.On the one hand,in response to the scarcity limitation of noble metals,the study of SPs properties of noble metal alloys shows that alloying significantly improves the LSPR absorption efficiency,resulting in a series of cost-effective LSPR materials.In addition,this thesis finds that phonon-assisted electronic transitions dominate the SPs decay near the interband threshold;In response to the low melting point limitation of noble metals,this thesis investigates the relationship between SPs and temperature,showing that TiN,a high-temperature resistant plasmonic material with the visible response,exhibits efficient light absorption and stable low-loss SPP at different temperatures,and the temperature mainly affects the phonon-assisted electronic transitions;In response to the exploration of the SPs in the new material,the study of 2D borophene shows that borophene with anisotropic electronic structure exhibit polarization-sensitive SPP and X-polarized light produces low-loss SPP in the visible light.On the other hand,this thesis investigates the properties of hot carriers excited by the SPs decay in metallic materials,including generation efficiency,energy and momentum distribution,and transport properties.The study of alloying of noble metals shows that alloying significantly improves the generation efficiency of high-energy hot carriers,which is closely related to the atomic ratio;The study of the temperature-hot carrier relationship shows that the energy distribution of high-energy hot holes in TiN and high-energy hot electrons in VN is thermally stable,and the effect of temperature on high-energy hot holes is significantly higher than that of highenergy hot electrons;The study of hot carriers in 2D borophene shows that the energy and momentum distributions of hot carriers exhibit strong polarization sensitivity and directionality.especially the momentum direction of hot electrons is highly anisotropic.while hot holes are uniformly distributed.In addition,the effect of electron-phonon scattering on hot carrier transport is found to be as significant as electron-electron scattering and cannot be neglected.Finally,for hot carriers generated by the dominant single-particle excitation in semiconductor materials,the effect of stress on hot carrier properties is investigated in this thesis.The results show that compression achieves an effective separation of hot electrons and hot holes in MoSi2N4 and improves the energy distribution probability of high-energy hot electrons.In addition,the transport properties of hot carriers are very sensitive to the stress response,especially the tensile significantly increases the relaxation time and the mean free range of carriers. |
