Design,Growth And Application Of Far-infrared Transparent Conductive Films

Transparent conductive film refers to a film material that has both high transmission properties and high conductivity in the reference band.It is widely used in infrared fairings,infrared thermal cameras,transparent electrodes and other military and sensing fields.At present,the transparent conductive synergy theory and material development in the visible-near-infrared region(0.4-1?m)are quite mature,but the infrared region(3-12?m),especially in the far-infrared band(8-12?m),not only It is difficult to put forward the theory of transparent conductive synergy,and far-infrared transparent conductive materials have not yet been successfully developed.Therefore,researchers are committed to developing various new infrared transparent conductive materials to meet the needs of far-infrared transparent conduction at the same time.But there are still the following problems:(1)The fundamental challenge in designing far-infrared transparent conductive films is how to simultaneously obtain high plasmonic reflection wavelength(?_p)and high electrical conductivity(?).Existing transparent conductive synergy theories are almost all limited to the relationship between equilibrium carrier concentration(n),effective mass(m*)and relaxation time(?),which usually leads to high?_p and high?at the expense of one another.For example,in order to ensure high conductivity of the material,the doping concentration is usually maintained at a high level,and the resulting large n will inevitably lead to a small?_p.Therefore,such synergistic ideas are not suitable for guiding the development of far-infrared transparent conductors.(2)The transmission properties of dielectric materials are strongly dependent on their dielectric properties.Various existing transparent conductive materials are mainly low optical frequency dielectric constants(?_opt),and there is no report on the use of high?_opt materials as far-infrared transparent conductive materials,and there is no related theory that?_opt can synergize with transparent conduction.In view of the above problems,we propose a new idea of increasing?_opt to realize the synergy of far-infrared transparent conduction and introduce high?_opt materials into the field of far-infrared transparent conduction.A series of high?_opt thin film materials,such as r-Bi₂Se_3-x,r-Bi₂Te_3-x,r-Bi₂(Se,Te)_3-x and c-Pb Se_1-x were prepared by magnetron sputtering,and carried out research on the growth,structure,bonding and optical and electrical properties of thin films.The main research contents can be summarized as the following two aspects:(1)We propose an efficient method to design high?_opt materials by dissecting the novel phenomenon that the?_opt(29.6)of crystalline r-Bi₂Se_3-x is much larger than that of amorphous Bi₂Se_3-x(9.5).Through theoretical calculations and experimental means such as charge density difference function and electron energy loss spectrum,we found that this unusually large optical-frequency dielectric constant originated from the few-electron multi-center bonding structure of the r-Bi₂Se_3-x film.In order to discover more potential far-infrared transparent conductors,we screened crystals with few electrons and multi-center bonds by the degree of ionization,hybridization and saturation,and thus established a map of far-infrared transparent conductive materials.(2)In order to verify that the predicted high?_opt materials are potential far-infrared transparent conductive films,we prepared a series of high?_opt thin films by magnetron sputtering and characterized their transparent and conductive properties.First,we investigated the effect of preparation conditions on the chemical composition of r-Bi₂Se_3-x films,and explored the effect of chemical composition on its transparent conductive properties.Then,we discuss the transparent conductive synergistic mechanism of high?_opt films through Se-deficient r-Bi₂Se_3-x films.Next,we prepared r-Bi₂Te_3-x,r-Bi₂(Se,Te)_3-x and c-Pb Se_1-x high?_opt films and characterized their transparent conductive properties.Finally,we evaluate the electromagnetic shielding properties of the r-Bi₂Se_2.4 film,verifying the feasibility of the r-Bi₂Se_2.4 film as a high transmittance electromagnetic shielding film.