Plasma-optical Properties Of Copper Film Nanocavities Studied Using Finite-difference Time-domain Metho

The local surface plasmon resonance of noble metal nanostructures has many novel optical properties,which can realize the enhancement of light absorption and scattering,the local enhancement of electromagnetic fields,and the photoelectric coupling and catalytic effect.Gold/silver has excellent surface plasmon optical properties,but due to its high price,its application in industrial catalysis,environmental protection and other fields has been limited.As a relatively inexpensive precious metal material,copper also has good surface plasmon characteristics and photocatalytic properties.Therefore,it is of great significance to study the plasmon optical properties of copper-based nanocavities.This thesis is reported in the following three parts:A single noble metal nanowire-thin film nanocavity is one of the important structures for the interaction between light and matter in current plasmonic optics.We designed the structure of Ag nanowire-Cu thin film nanocavity,and calculated its absorption and scattering spectra by finite difference time domain（FDTD）,and the results show that Cu thin film-based nanocavity has excellent plasmon resonance and electromagnetic field enhancement effects,and the results are basically consistent with Au thin film nanocavity,and low-cost copper can be expected to replace gold/silver to construct metal plasmonic optics.We further explored the effect of Cu film thickness on nanocavity plasmon optics and found that 40 nm thickness Cu thin films can achieve excellent optical properties.Subsequently,the effects of Al₂O₃ gap thickness,nanoparticle size and metal nanomaterials on plasmon resonance in Cu film nanocavities were studied.When the radius of Ag nanowires increased from 20 nm to 60 nm,the regulation of metal plasma resonance optics in the visible-near-infrared wide-band band of scattering resonance peaks from 626 nm to 1059 nm was realized.Based on the single-metal nanostructure-Cu thin film nanocavity,we further designed the Cu nanodisk-Cu thin film nanocavity periodic array.The effects of Cu nanodisk thickness,size and period spacing on plasmon resonance frequency were systematically studied by using FDTD to calculate the reflection spectrum of nanocavity arrays.The results showed that Cu nanodisk thickness and period spacing had little effect on the plasmon resonance frequency,while the influence of nanodisk radius was very significant.When the radius of the nanodisk increases from 15 nm to 50 nm,the resonance wavelength is redshifted to 575 nm,which realizes the large-scale regulation of the near-infrared region and provides an important theoretical basis for the construction of tunable copper-based nanodevices.In order to realize the ultra-sensitive regulation of the optical properties of the nanocavity,a two-dimensional material with atomic layer thickness is introduced as the gap layer,and three two-dimensional materials with different physical properties are selected:zero-bandgap graphene,semiconductor molybdenum disulfide and insulator hexagonal boron nitride.For two-dimensional materials from layers 4 to 12,we calculated the absorption and scattering spectra of the nanocavity,respectively.The results show that the graphene interstitial nanocavity does not obtain plasmon resonance enhancement with the increase of the gap layer thickness,and the molybdenum disulfide interstitial nanocavity achieves resonance regulation in a small range（1150-1000 nm）,while the hexagonal boron nitride interstitial nanocavity realizes metal plasma regulation from 784 nm-1161 nm visible-near-infrared band through the thickness change at the atomic layer level.This paper comprehensively analyzes the optical properties of nanocavity plasmon based on Cu thin film by using FDTD,which provides an important theoretical basis for the design and application of copper-based plasmon optical devices.