Optical Properties Of Rare-earth Boride By Surface Plasmon Resonance

Localized surface plasmon resonances (LSPRs) are the collective oscillation of electronsin innanometer-sized structures stimulated by incident light. Impact factors of LSPRs includeparticle element, geometry morphology, particle size, and media environment around particlesas well as the distance between the particles. LSPRs absorption peaks can be shift byregulating size and element of the particle. Rare-earth hexaboride (ReB6), with a small workfunction, high hardness, high melting point, high conductivity, are widely used in variousfields of civil industry and military industry. In this thesis, we studied LaB6, SmB6and EuB6nanoparticles. Based on the Drude model of size-dependence dielectric function andKramers-Kronig relationships, we researched optical properties of LaB6, SmB6and EuB6nanoparticles, such as absorption coefficient, extinction coefficient, energy loss, refractiveindex, and reflectivity. The main research contents and results are as follows:1. Based on the Drude model of dielectric function and Kramers-Kronig relationships ofself-consistent, Optical properties of LaB6, SmB6and EuB6nanoparticles (NPs) wereresearched. We found that absorption optimum position of LaB6, SmB6and EuB6nanoparticles were1200nm,1500nm and2000nm, respectively, and the intensity weregradually decreased. The absorption peaks redshifted as atomic number increased. LSPRsabsorption of LaB6NPs is the best. In rare-earth hexaboride, this is assumed to decrease theoverlap of electron clouds of Re5d with B2p that form the conduction bands and areconsidered to reduce the density and mobility of free electrons. LSPRs absorption peakredshifted as conduction electrons density decreased.2. LSPRs absorption peaks also can be shift by regulating the size particle. Firstly, inLaB6nanoparticles, when R <80nm, LSPRs peaks redshifted from870to3000nm as sizeincreased, and LSPRs disappear when R>80nm. Secondly, in SmB6nanoparticles, whenR<130nm, LSPRs peaks redshifted from700to4300nm as size increased, and LSPRsdisappear when R>130nm. Thirdly, in EuB6nanoparticles, when R <130nm LSPRs peaksredshifted from1350to4900nm as size increased, and LSPRs disappear when R>130nm. SoLSPRs peaks exhibited size-dependence.3. We also researched the LSPRs absorption of LaB6thin films. By changing the filmdeposition time, LSPRs absorption peak of LaB6films redshifted from950nm to1250nm. Aroughness structure is built up by islands and tips from AFM topography. In the incident light,due to LSPRs, electron on the projection surface redistributed and absorbed selectivelyincident light. LSPRs enhanced absorption of LaB6films emerged in the near-infrared regionand exhibited broad absorption, so that LaB6thin films can be used in a wide range of laserprotection in infrared image. Meanwhile LaB6film with good transmittance in the visibleregion can be used as a window material in automotive glass and building to block the thermal radiation of sunlight.