【作者】 李莉；

【导师】 徐英添；

【作者基本信息】 长春理工大学 ， 光学工程， 2024， 博士

【摘要】 ZnO作为代表性第三代直接带隙半导体材料,具有3.37 e V的禁带宽度,高达60me V的激子束缚能,是制备高性能紫外光电子器件的理想材料。此外,ZnO纳米材料具有制备方法多样,形貌结构丰富且物理化学性质卓越等特点。近年来,由于纳米线具有更大的比表面积,更优良的电导传输效率,成为国内外研究热点。尤其是高度一致且排列有序的纳米线阵列,因其精确可控的结构,具有比无序的纳米材料更加优异的光电特性。基于此,本论文分别利用低温水热法和化学气相沉积（CVD）法开展ZnO纳米线阵列的可控生长研究,并通过紫外光刻技术构建有序可控的ZnO纳米线阵列结构。最后基于有序可控的ZnO纳米线阵列结构开展光电器件特性研究。具体研究内容与成果如下:一、开展了ZnO纳米线阵列的生长研究。分别采用低温水热和CVD法,进行ZnO纳米线阵列的生长实验。研究表明,在水热法的制备过程中,纳米线径向的生长速度会随着反应物浓度的增加而提高,随着生长时间的增加,纳米线径向会出现聚合现象,反应时间越久,聚合现象愈加明显;在CVD法的制备过程中,在1000 Pa的低压环境下实现纳米线的生长,实验证明低压环境更有利于纳米线生长,管内压强过大会导致纳米线侧面（1010）的Zn原子会和O原子反应,以纳米线为基底沿侧向外延生长纳米线,连成纳米梳甚至纳米片。二、开展基于ZnO纳米线阵列紫外光电探测器的研究。首先,制备基于ZnO纳米线阵列及掺镁ZnO纳米线阵列紫外光电探测器。对于Mg元素作为ZnO受主掺杂剂的ZnO:Mg纳米线阵列的紫外探测器件,其暗电流相比于无掺ZnO纳米线阵列的器件下降超过10倍,灵敏度提升近2倍。其次,采用时域有限差分法（FDTD）设计折射率交替排布的周期性多膜结构,即增加ZnO/Si O₂/ZnO/Si O₂多层周期膜,有效提高纳米线阵列层光场局域性。实验结果表明,优化后的器件365 nm光照下的光电流提高了约50倍,响应度由原来的0.19 m A/W提升到2.80 m A/W,比探测率由原来的2.05×10⁹Jones提升到3.16×10⁹Jones,器件的整体探测性能得到显著提升。最后,构造ZnO纳米线阵列/Zn掺杂Cu Ga O₂微米片（Mg掺杂Cu Ga O₂微米片）垂直异质结构光电探测器。实验结果表明,垂直异质结构器件的探测性能较纯微米片器件的探测性能具有显著提升,ZnO/Zn掺杂Cu Ga O₂微米片异质结构的响应度由7.52 m A/W提升至1.34×10³m A/W,ZnO/Mg掺杂Cu Ga O₂微米片异质结构的响应度由5.11 m A/W提升至636 m A/W。三、利用紫外光刻技术在GaN衬底上制备有序可控的ZnO纳米线簇阵列,基于此结构制备具有垂直结构的异质结发光二极管,通过调整ZnO种子层的退火温度,改变单孔内纳米线簇的密度及孔内纳米线的直径,制备可以能够在正反偏压下均发光的双向发光二极管。进一步地,对生长模板和反应条件进行调整,实现单根纳米线的有序且位置可控的生长。制备直径2μm纳米线间距2μm,直径2μm纳米线间距5.5μm,直径6μm纳米线间距2μm,直径6μm纳米线间距18μm的四个不同排列的周期性ZnO纳米线阵列紫外发光器件。实验结果表明减小纳米线之间的间距或增大纳米线直径能够增强纳米线阵列的耦合作用,从而实现纳米线阵列的发光增强。当保持纳米线间距不变,随着纳米线直径从2μm增加至6μm,其电致发光特性得到近1.5倍的增强;当保持纳米线直径6μm不变,随着纳米线间隔由18μm减小至2μm,其电致发光特性也得到近1.5倍的增强。四、利用纳米颗粒的局域表面等离激元（localized surface plasmon,LSP）,实现纳米颗粒与有序可控ZnO纳米线阵列的局域表面等离激元共振（localized surface plasmon resonance,LSPR）。首先,利用FDTD对金属纳米颗粒和金属纳米颗粒修饰的ZnO纳米线阵列的光学特性进行仿真计算,发现金属纳米颗粒的修饰可以有效增强ZnO纳米线阵列的光场特性。其次,通过以硼氢化钠（Na BH₄）为还原剂对硝酸银进行还原,制备了直径20 nm的Ag纳米颗粒,然后以正硅酸乙酯为硅源,以氨水作为催化剂,在直径20nm的Ag纳米颗粒表面包裹了5 nm厚度的Si O₂,形成核壳结构Ag@Si O₂纳米颗粒。对制备的核壳结构Ag@Si O₂纳米粒子吸收光谱进行表征,测试结果表明其共振吸收峰位于402 nm,可以与纳米线阵列的电致发光峰相重合,从而与所制备的ZnO纳米线阵列发生共振耦合。最后,将制备的Ag@Si O₂核壳结构金属纳米颗粒修饰在纳米线间距2μm,直径分别为2μm和6μm的ZnO纳米线阵列上。实验结果表明,纳米颗粒修饰后的两个器件的紫外波段电致发光强度都得到了约1.5倍的提升,并且ZnO的深能级缺陷发光被抑制。直径越大的纳米线不仅拥有更强的耦合作用,同时更有利于增加纳米颗粒的附着量,可以更大程度的利用纳米颗粒的等离子激元特性,因此,修饰后的直径6μm纳米线阵列的电致发光强度是修饰后直径2μm纳米线阵列的2倍,较之前的1.5倍有更高的提升。五、开展以ZnO纳米线阵列实现连续域束缚态的研究。利用仿真软件Comsol Multiphysics,对不同半径的四方晶格排列的ZnO纳米线阵列进行分析,在半径为150 nm时找到位于布里渊区中心点的孤立的对称保护模式的连续区束缚态（BIC）,在半径为125nm时找到位于非中心点处的偶然BIC,并且通过调整半径,在半径为200 nm时成功将两种BIC合并,得到合并模式的BIC,合并BIC相对于孤立BIC和偶然BIC,可以在更广的波矢量范围内实现稳定有效的BIC态,大大提高结构的鲁棒性,降低了对器件对称性要求,在提高微纳光电子器件性能的同时降低对工艺精度的要求。并且由于Γ点BIC和偶然BIC常出现于光子晶体平板中,使合并BIC结构具有普适性,可扩展应用于许多光电子器件中。更多还原

【Abstract】 Zinc oxide（ZnO）,a representative of third-generation direct bandgap semiconductors,possesses a bandgap energy of 3.37 e V and an exciton binding energy of 60 me V.These characteristics make it indispensable for the fabrication of high-performance ultraviolet（UV）optoelectronic devices.Furthermore,ZnO is distinguished by the varied synthetic methods,intricate morphological structures,and exceptional physicochemical properties.In recent years,nanowires（NWs）have become a research hotspot in national and international because of their larger specific surface area and better conductivity transmission efficiency recently.Particularly,highly coherent and precisely aligned arrays of NWs exhibit superior optoelectronic properties compared to disordered counterparts due to their finely adjustable structural attributes.Based on this,the controlled synthesis of ZnO NW arrays is studied by low-temperature hydrothermal methods and chemical vapor deposition（CVD）methods.The orderly and controllable ZnO NW arrays are constructed through UV lithography techniques.Finally,the characteristics of optoelectronic devices are studied based on the ordered and controllable ZnO NW array structure.The concrete research contents and achievements are as follows:（1）The growth of ZnO NW arrays was studied.The growth experiments of ZnO NW arrays were carried out by the low-temperature hydrothermal method and CVD method,respectively.The results show that the radial growth rate of the NWs increases with the increase of material concentration,and radial polymerization of the NWs occurs with the increase of growth time.In the processes of the CVD method,NW growth was achieved under a low-pressure environment of 1000 Pa,and the experiment proved that the low-pressure environment was more conducive to the growth.Excessive pressure in the tube resulted in a reaction between Zn atoms（1010）on the side of the NWs and O atoms,leading to a lateral epitaxial growth,forming interconnected nano-combs or nano-sheets.（2）The study of photodetectors based on the ZnO NW array was carried out.Firstly,the UV photodetectors based on ZnO NW array and Mg-doped ZnO NW array were prepared.For the UV photodetectors based on the ZnO:Mg NW array,the dark current of the photodetector is more than 10 times lower than that of the undoped ZnO NW array,and the sensitivity is nearly 2 times higher.Secondly,the finite-difference-time-domain（FDTD）method is used to design the periodic multi-film structure with alternating refractive index.The multi-layer periodic films of ZnO/Si O₂/ZnO/Si O₂were added to improve the optical field localization of the NW array layer effectively.The experimental results showed that the photocurrent of the optimized device under 365 nm illμmination was increased by about 50times,the responsivity was increased from the 0.19 m A/W to 2.80 m A/W,the specific detection rate was increased from the 2.05×10⁹Jones to 3.16×10⁹Jones,and the overall performance of the device was significantly improved.Finally,the ZnO NW array/Zn-doped Cu Ga O₂micron sheet（Mg-doped Cu Ga O₂micron sheet）vertical heterostructure photodetector was constructed.The experimental results showed that the detection performance of heterostructure devices was significantly improved than that of pure micron sheet devices,and the response of ZnO/Zn-doped Cu Ga O₂micron sheet heterostructures was increased from 7.52 m A/W to 1.34×10³m A/W.（3）An orderly and controllable ZnO NW array was prepared on GaN substrate by ultraviolet lithography,and the heterostructure LEDs was prepared based on the structure.By adjusting the annealing temperature of ZnO seed layers,changing the density of the nanowires in a single hole and the diameter of the NWs in the hole,the bidirectional LED was prepared.Furthermore,the growth template and reaction conditions were adjusted to achieve the orderly and position-controlled growth of single NW.And,four different arrangements of ZnO NW arrays were prepared:diameter of 2μm and spacing of 2μm,diameter of 2μm and spacing of 5.5μm,diameter of 6μm and spacing of 2μm,diameter of 6μm and spacing of 18μm.The results showed that decreasing the distance between the NWs and increasing the diameter of the nanowire could enhance the coupling effect of the nanowire array,so as to realize the enhancement of the luminescence of the NW array.When the spacing between NWs was constant,the diameter was increased from 2μm to 6μm,and the electroluminescent characteristics got an approximately 1.5-fold enhancement.When the diameter of NWs was constant of 6μm,the spacing of NWs was decreased from 18μm to 2μm,and the electroluminescent characteristics were enhance by approximately 1.5 times.（4）Localized surface plasmon resonance（LSPR）between nanoparticles and orderly controllable ZnO NW arrays was achieved by localized surface plasmon（LSP）of nanoparticles.Firstly,the optical properties of ZnO NWs modified by metal nanoparticles and metal nanoparticles were simulated by FDTD.It was found that the modification of metal nanoparticles can effectively enhance the optical field characteristics of ZnO nanowire arrays.Secondly,Ag nanoparticles with a diameter of 20 nm were prepared and Si O₂with a thickness of 5 nm was coated on the surface of the Ag nanoparticles to form core-shell Ag@Si O₂nanoparticles.The absorption spectra of the prepared core-shell Ag@Si O₂nanoparticles were characterized.The results showed that the resonant absorption peak of the prepared core-shell Ag@Si O₂nanoparticles was 402 nm,which can coincide with the electroluminescence（EL）peak of the NW array,and resonance coupling with the prepared ZnO NW array was carried out.Finally,the prepared Ag@Si O₂core-shell metal nanoparticles were modified on ZnO NW arrays.The NW arrays were arranged in specific configurations:diameter of 2μm and spacing of 2μm,diameter of 6μm and spacing of 2μm.The results showed that the ultraviolet EL intensity of the two devices modified by nanoparticles was increased by about1.5 times,and the deep level defect luminescence was suppressed.Nanowires with larger diameter not only have stronger coupling effect,but also are more conducive to increasing the adhesion amount of nanoparticles,and the plasmon characteristics of nanoparticles could be better utilized.Therefore,the EL intensity of the modified 6-μm NW array was twice that of the modified 2-μm NW array,which is a higher improvement than the previous 1.5 times.（5）The bound states in continuum（BIC）was realized by ZnO NW arrays.The simulation software Comsol Multiphysics was used to analyze the ZnO NW arrays with different radii.The isolated symmetric protection BIC located at the center point of Brillouin region at the radius of 150 nm was found.When the radius is 125 nm,the accidental BIC located at the non-central point is found,and when the radius is 200 nm,the two kinds of BIC will be successfully merged to obtain the merged mode BIC.Compared with the isolated BIC and accidental BIC,the merged BIC could achieve more stable and effective BIC states in a wider range of wave vectors.And sinceΓBIC and accidental BIC could often occurs in photonic crystal plates,the merged BIC structure is universal and could be extended to many optoelectronic devices.更多还原