【作者】 张恒；

【导师】 刘昌；

【作者基本信息】 武汉大学 ， 材料物理与化学， 2022， 博士

【摘要】 光在人们的生活当中极其重要。太阳光普照大地,让人们可以在白天看到绚丽多姿的世界,让绿色植物通过光合作用产生氧气,让空气中充满温暖的气息……。除了我们可以看见的可见光,还存在肉眼看不见的紫外光和红外光。在新冠疫情肆虐全球的背景下,教室里的紫外杀菌和商场门口的红外测温,让我们更直观地认识到它们的存在。紫外光具有较高能量,可以用于医疗杀菌、紫外固化等领域。氧化锌由于具有3.37 e V的宽带隙,60 me V的激子束缚能,同时又具有价廉、无毒等优点,是很好的紫外发光材料。然而目前基于氧化锌的发光器件,其发光效率依然有限,增强其发光就显得意义非凡。红外光与热辐射相关,在热成像、导弹制导、红外隐身等领域具有重要用途。温度大于绝对零度的物体都是热辐射源。为了利用这些热辐射,需要捕获红外光,此时实现宽光谱红外吸收就显得尤为重要。当物质具有一定的微纳结构时,其往往展现出新颖的光学性质。制备特定的微纳结构,是实现增强紫外发光和宽光谱红外吸收的有效方法。本文主要围绕以下五个部分进行展开:一、以胶体晶体为模板,制备了多种微纳结构,为实现增强紫外发光和宽光谱红外吸收奠定基础。首先,通过气液界面自组装的方法,制备了作为模板的单层胶体晶体,胶体球的直径可以从360 nm到3μm。然后,以胶体晶体为模板,结合氧等离子体处理和物理气相沉积,制备了金属纳米颗粒阵列和金属纳米网。最后,以胶体晶体为模板,结合原子层沉积和氧等离子体处理,制备了氧化铝球壳结构和氧化铝碗形结构。二、将基于胶体晶体模板的金属纳米结构引入到氧化锌中,增强了其紫外发光。首先,通过时域有限差分(FDTD)的方法进行了理论模拟,找出了表面等离激元共振波长与氧化锌紫外发光波长相匹配的铝三角形纳米颗粒的尺寸。然后基于模拟结果,选择了直径为360 nm的胶体球,制备了间隙可调的铝纳米结构,其中最小、均一的间隙为31 nm。最后,将铝纳米结构引入到氧化锌中,获得了4倍的紫外发光增强。FDTD理论模拟表明,在间隙处产生了巨大的场增强,这促进了表面等离激元-激子共振耦合,从而产生了较大的发光增强。三、基于炭黑渐变结构,获得了超宽光谱吸收器。吸收表现为抑制透射和反射,可以通过由抗透层、吸收层和减反层组成的结构来实现。本文以铝板为抗透层,炭黑有机粘合剂复合膜为吸收层,纳米锥为减反层,获得了在0.4-20μm范围内平均光吸收率为99.1%的超宽光谱吸收器。四、构思了基于超薄折叠高损耗薄膜的宽光谱红外吸收器。较高光损耗的体材料常常具有高反射,然而当其为超薄薄膜时,上下两个界面的反射光会发生相消干涉,在宽光谱范围内可以具有很小的反射。如果此时通过折叠的方式使光多次穿过超薄薄膜,则可以实现多次光损耗,最终强有力地捕获光。基于此,构思了基于这种结构的宽光谱红外吸收器。对于超薄折叠高损耗薄膜,进一步地通过传输矩阵的方法对其进行了理论分析,探究了结构参数对其光学性质的影响。五、通过在作为折叠支架的氧化铝球壳上沉积薄膜的方法,获得了基于超薄折叠高损耗薄膜的宽光谱红外吸收器。首先,通过FDTD的方法进行了理论模拟,探究了氧化铝球壳层数和作为光损耗材料的铝掺杂氧化锌(AZO)薄膜的厚度对平均光吸收率的影响,进而找到了合适的参数。然后基于模拟结果,实验上以原子层沉积的方法,在三层氧化铝球壳支架上沉积了43 nm的AZO薄膜,获得了在3-15μm范围内平均光吸收率达到97.6%的结果。FDTD理论模拟表明,AZO薄膜厚度较大时,不利于光的进入,AZO薄膜厚度较小时,每层的吸收有限,只有选择合适的薄膜厚度和支架层数时,才可以实现强吸收。最后,将超薄折叠高损耗薄膜应用到铝箔上,在人体背景下实现了铝箔的红外隐身。更多还原

【Abstract】 Light is very important in our daily life.The light from sun illuminates the earth,making us see the colorful world,making plants produce oxygen and making the air be warm.Besides visible light which we can see,there also exist ultraviolet and infrared light that we can not see.As the COVID-19 pandemic ravages the world,ultraviolet sterilization in the classroom and infrared thermometry at the gate of mall,visually make us realize the existence of ultraviolet and infrared light.Ultraviolet light with higher energy can find applicatons in sterilization and solidification.ZnO,which has a band gap of 3.37 e V and exciton binding energy with 60 me V,is a great choice for ultraviolet light emission for advantages of low cost and no toxicity.However,luminous efficiency from devices based on ZnO is still limited.Hence,it is attractive to enhance the emission from ZnO-based devices.Infrared light,which is associated with thermal radiation,is very important in the fields of thermal imaging,missile guidance and infrared camouflage.Matters with temperature above 0 K are sources of thermal radiation.It needs to trap infrared light for the purpose of utilizing thermal radiation.Therefore,it is very important to obtain super broadband infrared absorbers.When matters have micro/nano structures,they often possess novel optical properties.It is appealling to fabricate certain micro/nano structures for the realization of enhanced ultraviolet light emission and broadband infrared light absorption.In this thesis,we mainly focus on the following five topics:1.Micro/nano structures were fabricated by using colloidal crystals as templates,laying a foundation for the realization of enhanced ultraviolet light emission and broadband infrared light absorption.Firstly,colloidal crystals which served as templates were fabricated by the method of self-assembly at air-liquid interface,and the diameters of colloidal spheres can be the range from 360 nm to 3 μm.Then,combining with oxygen plasma treatment and physical vapor deposition(PVD),metal nanoparticle arrays and namomeshes were fabricated by using colloidal crystals as templates.Finally,combining with atomic layer deposition(ALD)and oxygen plasma treatment,alumina spherical shells and bowls were fabricated by using colloidal crystals as templates.2.Enhancement of ultraviolet light emission from ZnO was achieved by the introduction of metal nanostructures fabricated by using colloidal crystals as templates.Firstly,simulations based on finite-difference time-domain(FDTD)method,were performed to find the proper sizes of Al triangle nanoparticles whose surface plasmon resonance wavelength matches with the emission wavelength of ZnO.Then,based on the results of simulations,the diameter of colloidal spheres was chosen as 360 nm,and Al nanostructures with tunable gap distances whose uniform and minimum value is 31 nm,were subsequently fabricated.Finally,after the introduction of Al nanostructures,4-folded enhancement of ultraviolet light emission from ZnO,was gained.Theoretical analysis based on FDTD simulations demonstrated that the tremendous field enhancement among gaps promoted the surface plasmon-exciton coupling,and then improved light emission.3.Super wide bandwith absorbers which were based on carbon black graded structures,were obtained.Absorption results in the prohibition of transmission and reflection.This can be realized by the structures consisted of opaque substrates,absorptive layer and anti-reflection structures.In this thesis,Al plates,composite films consisted of carbon black and organic binding agent,and nanotips,were served as opaque substrates,absorptive layer and anti-reflection structures,respectively.Results showed that an average absorptance of 99.1% over the wavelength range from 0.4 to 20 μm,was obtained in this absorbers.4.A strategy of ultrathin folded highly-lossy films(UFHFs),was proposed to get super broadband infrared absorbers.Bulks with highly lossy materials usually show large reflection.However,when they have the structures of ultrathin films,tiny reflection is gained due to the destructive interference between reflected light from top and bottom interfaces.At this time,if fold the ultrathin films and make multiple optical pass through,it would impart enough optical loss and show strong absorption.Hence,A strategy of UFHFs was proposed.Theoretical analysis based on transfer matrix method was further performed for UFHFs,revealing the relationship between structure parameters and optical properties of UFHFs.5.Super broadband infrared absorbers based on UFHFs,were obtained by depositing ultrathin films on scaffolds of alumina spherical shells.Firstly,simulations based on FDTD method were performed to explore influences of the paramers that one is the number of scaffold layers and the other is the thickness of Al-doped ZnO(AZO)which serves as highly lossy materials,and find the proper values of the parameters.Then,based on the results of FDTD simulations,absobers were experimentally obtained by depositing 43 nm AZO films on three-layer scaffolds of alumina spherical shells,achieving an average absorptance of 97.6% over the wavelength range from 3 to 15 μm.Theoretical analysis based on FDTD simulations showed that thicker AZO films block the admission of incident light,thinner AZO films need more layers of scaffolds to stongly trap light due to the limited absorption in each layer,and super absorbers can be realized by choosing the proper parameters.Finally,applying this UFHFs on Al foil,it showed excellent infrared camouflage performance on human-body background.更多还原