【作者】 杨磊；

【导师】 韩杰才； 朱嘉琦；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2015， 博士

【摘要】 在光电系统的发展过程中,透明导电材料已经成为航空航天光电系统不可或缺的重要组成部分。对于红外光电系统而言,前置大孔径红外光学窗口探测红外信号易受电磁波的干扰,传统金属网栅等材料不能满足红外波段高透过与电磁屏蔽隐身性能协调的要求。针对上述问题,本文在室温下采用等离子体轰击辅助磁控溅射制备晶态中红外透明导电氧化铟(In2O3)和氧化铟锡(In2O3:Sn)薄膜。系统研究不同负偏压(|Vp|)对两种薄膜内部晶体结构、光电性能和表面能态之间的内在联系;采用双靶磁控共溅射制备远红外透明导电钌掺杂氧化钇(Y2O3:Ru)薄膜,研究不同基底温度和掺杂浓度与成分、结构和光电等性能的联系;利用德鲁德自由电子理论对上述薄膜材料的等离子频率进行拟合,并实现了中、远红外的透明导电。等离子体轰击辅助磁控溅射在室温下制备的In2O3和In2O3:Sn薄膜,证实晶体结构与其生长条件密切相关。随着负偏压(|Vp|)的增加,In2O3和In2O3:Sn薄膜表面形貌发生显著变化,证明等离子体轰击辅助磁控溅射是一种精细修改表面形貌的可控手段。随着|Vp|的增加,薄膜内部由非晶态转变为晶态,且晶态薄膜择优取向也发生了相应的变化。通过光电性能的研究发现,In2O3和In2O3:Sn薄膜在可见光波段的透过率均大于80%,且光学带隙的变化遵从Burstein-Moss效应;薄膜随着|Vp|的增加,两者电阻率均呈现先降低后增加的变化。In2O3薄膜的变化原因是|Vp|的增加导致氧空位含量减少、载流子浓度降低、迁移率呈现先升高后降低的趋势。相比之下,In2O3:Sn薄膜的变化原因是|Vp|的增加,掺杂的低价态Sn2+转变为高价态Sn4+的量增多,因此载流子浓度有所增加。在|Vp|=|-700 V|制备的In2O3和In2O3:Sn薄膜具有在可见光波段最佳的光电性能;通过紫外荧光光谱法(UPS)证明该技术有助于改善In2O3和In2O3:Sn薄膜的功函数。当|-600 V|<|Vp|<|-700 V|时,In2O3薄膜氧空位含量减少使得其功函数提高。当|-700 V|<|Vp|<|-900 V|时,In2O3薄膜随着晶向由<222>转变为<400>,表面结构发生重构引起表面功函数的增加。与之相比,In2O3:Sn薄膜功函数的增加是因为低氧化态Sn2+向高氧化态Sn4+转变。在高轰击能作用下,表面结合Sn-O键增多提高了In2O3:Sn薄膜的功函数。利用双靶磁控共溅射制备的Y2O3:Ru薄膜发现,薄膜微观结构直接受到钌靶射频功率和基底温度的影响。薄膜的沉积速率随钌靶溅射功率的增加而增加。制备Y2O3:Ru薄膜的XRD结果证实,所有Y2O3:Ru薄膜均为非晶薄膜。XPS测试表明Y2O3:Ru薄膜中含有低能态的Ru4+-O键和高能态的Ru6+-O键。随着Ru掺杂含量的增加,Ru4+峰的强度增大而Ru6+峰强度减小。当衬底温度逐渐升高时,Ru6+峰的强度提高而Ru4+峰的强度下降。霍尔测试分析表明Y2O3:Ru薄膜属于n型半导体。随着掺杂含量的增加导致薄膜中的间隙原子等缺陷增多、载流子浓度逐渐增加,最佳的面电阻可达~283.4Ω/□。当衬底温度升高时,薄膜中缺陷含量相对减少,面电阻增大至~2.17×105Ωcm。UV-VIS-NIR分析表明,钌掺杂含量的增加显著提高了薄膜中散射质点的含量,降低了可见光波段的透过率。可见光波段的透过率同衬底温度的升高一同升高,说明薄膜中原子的有序性有所增加,消除了部分空位并使得一些间隙原子运动到更加有利的位置。在这两个过程中,载流子浓度的变化,引起了费米能级上升或下降,从而带来光学带隙在1.90~2.54 e V间的变化。根据德鲁德自由电子理论对以上三种薄膜材料的等离子波长进行拟合。通过延长等离子波长,沉积In2O3/Y2O3膜系与仅在Zn S基底上沉积In2O3薄膜相比,中红外透过率提高19%;在沉积Y2O3:Ru薄膜于红外透明Zn S基底,远红外透过率基本与基底透过率相当(~70%);通过设定延长等离子波长利用并沉积In2O3:Sn于Si O2镜头和飞机座舱盖(PMMA)实现抗红外热辐射和电磁屏蔽效果。通过载流子浓度的调整可以有效地延长和缩短以上三种薄膜材料的等离子波长,可以实现中红外和远红外的透明导电特性。更多还原

【Abstract】 Infrared transparent and conductive oxides will become the indispensable components of optic-electric devices in the astronautics and aeronautics. However, the traditional infrared transparent and conductive oxide is unavailable to have both the high infrared transmittance and superior electric properties. Based on the above background, mid-infrared transparent and conductive In2O3 and In2O3:Sn films were prepared by plasma assisted magnetron sputtering, which are crystalline. The influence of pulsed bias voltage(|-400 V|<|Vp|<|-900 V|)on the crystal structure, optical-electric properties and surface energy state were studies systematically. After that, far-infrared transparent and conductive Y2O3:Ru films were prepared by using magnetron sputtering with dual targets. Investigating the correlation between the Ru doping concentration, substrate and the chemical elements, structure and electric-opt properties were conducted. Carrier concentration were coupling with the plasma frenquency for In2O3 and In2O3:Sn films. The Y2O3:Ru films were deposited on the Zn S substrate, realizing the transparent and conductive functionality in far-infrared range.The crystal structure of In2O3 and In2O3:Sn films, which prepared by plasma assisted magnetron sputtering, is closely linked to the growth parameters. With the increase of plused bais voltage, it is obviously to observe the change in surface morphology, proving that this method is an useful way to modify the surface contents. Amorphous-crystal transformation come true when the pulsed bias voltage changes. Both In2O3 and In2O3:Sn films have superior optical and electric properties. The electric properties of In2O3 and In2O3:Sn films increased with the increase of pulsed bias voltage. The film resistivity decreased firstly and then went up, while the electronic mobility shows the opposite trend. With the increase of pulsed bias voltage the oxygen vacancies reduced, causing the lower carrier concentration. In contrast, the increased pulsed bias voltage induced the transform from Sn2+ to Sn4+ in the films, resulting in the higher carrier concentration. Both In2O3 and In2O3:Sn films had high transmittance of 80 % in visible range, the band gap follows the Burstein-Moss law. At room temperature, the In2O3 and In2O3:Sn films have the optimal electric and optical properties at the pressure of 0.5 Pa and |Vp|=|-700 V|. Furthermore, hardness results showed the improved hardness of films can be obtained by the route of plasma assisted deposition. The work function of In2O3 and In2O3:Sn films measured by UPS can be modified by plasma assisted deposition. When the bias voltage is in the range of |-600 V|<|Vp|<|-700 V|, oxygen vacancie on the In2O3 surface reduced, leading to the increased work function. While the bias voltage increased to the range of |-700 V|<|Vp|<|-900 V|, the transformation between <222> orientation and <400>occurred resulting the higher wok function. In contrast, the higher work function of In2O3:Sn was mainly due to the transformation of Sn2+ to Sn4+ state after the plasma bombardment. Higher energy ions bombardment induced more Sn-O bond, more oxygen on the surface, causing large work function.In the preparation of Y2O3:Ru by dual magnetron sputtering, it was found that radio frequency power applied on the Ru target and the substrate temperature were the most important growth parameters. When the power increased, the deposition rate increases. All the as-deposited Y2O3:Ru films were amorphous. XPS results showed Y2O3:Ru films contained Ru4+-O and Ru6+-O bonds. As the Ru concentration increased, the intensity of Ru6+ increased and decreased for Ru4+. Hall measurement showed Y2O3:Ru belonged to the n-type semiconductor. Increasing Ru doping concentration, the films had more defects, causing in creased carrier concentration and decreased mobility. At higher temperature, the films showed lower carrier concentration and higher mobility due to the reduction of interstitial atoms and oxygen vacancies in the films.Ultar violet-visible-near infrared spectrophotometry displayed higher Ru doping concentration induced lower transmittance in visible range due to the stronger scattering. When the substrate temperature increased form room temperature to 600 ℃, the transmittance of films in the visible range increased gradually, indicating the improved atom order, which can be explained that higher temperature remove some vacancies and provided more energy for atom mobility, during this process, the carrier concentration increased or decreased causing the increasing and decreasing band gap.Finally, the coupling relationship between carrier concentration and plasma frequency of In2O3, In2O3:Sn and Y2O3:Ru thin films by magnetron sputtering assisted plasma exposure were investigated. Moreover, the optimized Y2O3:Ru was deposited on the Zn S substrate and compared with the other known far-infrared transparent and conductive materials.更多还原