【作者】 徐静；

【导师】 闵光辉；

【作者基本信息】 山东大学 ， 材料学， 2009， 博士

【摘要】 六硼化镧（LaB₆）是一种具有许多优异性能的陶瓷材料,广泛应用于民用和国防工业制作现代仪器中的电子元器件。国内外的科研工作者对LaB₆薄膜开展了一些研究工作,但对薄膜性能的研究主要集中于所制得薄膜的形貌、结构及其物理性能,对其光学性能研究较少,仅有的研究也是将其作为装饰材料使用。为充分研究和利用LaB₆在光学方面的独特性能,采用透明的SiO₂材料作为基体沉积LaB₆薄膜。采用磁控溅射法在SiO₂基片上沉积LaB₆薄膜。调整了溅射过程中的氩气气压、基片偏压、基片温度和溅射功率等工艺参数。分别采用探针轮廓仪、原子力显微镜、掠入射角X射线衍射仪、高分辨透射电镜及场发射扫描电镜,分析不同工艺参数对薄膜的沉积速率、表面形貌、结构、晶格相、断口形貌及膜基相互扩散情况的影响。系统研究了磁控溅射法沉积的LaB₆薄膜的膜基结合力、硬度、弹性模量以及薄膜的光学和电学性能。分析了工艺参数对LaB₆薄膜性能的影响。研究结果表明,LaB₆薄膜的沉积速率受溅射功率影响最明显,溅射功率为61.6W、氩气气压为1.5Pa、基片偏压为-100V和基片温度为室温时,沉积速率最大,为19.8nm/min。溅射功率降至17.6W,其它工艺参数不变时,沉积速率为3.22nm/min。原子力显微镜的结果显示,SiO₂基LaB₆薄膜表面平整,结构较为致密。有些薄膜表面存在孔洞等缺陷,但通过调整溅射工艺,可以得到致密性良好的薄膜。基片偏压对薄膜的形貌影响最大,不同偏压下制备的薄膜表面致密度相差较大,其中基片偏压为-100V、溅射功率为44.0W、氩气气压为1.5Pa、基片温度为400℃时,制备的LaB₆薄膜表面致密,没有发现明显的缺陷。薄膜表面平均粗糙度均在2nm左右,其最小值仅为1.336nm。基片温度对薄膜的平均粗糙度影响最大,其最大值与最小值之差为1.125nm。在基片加热条件下制备的LaB₆薄膜的粗糙度大于其它工艺条件下制备的薄膜的粗糙度。利用场发射扫描电镜观察了SiO₂基LaB₆薄膜的断口形貌以及断口表面的面元素分布。结果显示,薄膜的生长方式为柱状生长,SiO₂基片偏压绝对值的增大和温度的升高有利于薄膜的柱状结构生长,基片偏压绝对值的增大对薄膜柱状结构的影响最大。其中,溅射功率为44W、基片偏压为-150V、氩气气压为1.5Pa、基片温度为室温的LaB₆薄膜柱状结构最为明显。随着基片温度的降低和基片偏压绝对值的增大,LaB₆薄膜与SiO₂基片之间的扩散程度变弱。XRD结果显示,除在溅射功率为17.6W,氩气气压为1.5Pa,基片偏压为-100V,基片温度为室温以及基片温度为500℃,溅射功率为44W,基片偏压为-100V,氩气气压为1.5Pa时所制得的两个试样没有出现明显的X射线衍射图谱外,其余薄膜均得到了良好的XRD图谱,且所有晶体结构薄膜的优势结晶面均为（100）晶面,这一情况与块体材料不同。研究发现,薄膜的结晶程度受工艺参数的影响,在氩气气压为1.0Pa、基片温度为室温和氩气气压为1.5Pa、基片温度为400℃,其它参数分别为基片偏压为-100V、溅射功率为44.0W时沉积的薄膜结晶情况最好。利用X射线衍射数据,Scherrer公式计算的结果表明,本论文中制备的薄膜均为纳米结构,其平均颗粒尺寸介于10～30nm之间。这一结果与原子力显微镜和场发射扫描电镜的结果吻合的很好。高分辨透射电镜的结果表明,溅射功率为44W,氩气气压为1.5Pa,基片偏压为-100V,基片温度为室温的条件下制备的薄膜结晶程度良好。在其晶格相中发现了（100）（110）（111）三个晶面。其晶面间距分别为0.4051nm、0.2942nm和0.2382nm,相对于块体材料都有不同程度的畸变。利用划痕法测试了薄膜与基体之间的结合力。实验结果表面,SiO₂基体与LaB₆薄膜之间的结合力介于110mN到155mN之间。采用纳米压痕仪测试了薄膜的硬度及弹性模量。薄膜的载荷-位移曲线中未出现突变现象,表明薄膜的弹塑性能良好。薄膜的最大硬度和最小硬度分别为20.043GPa和8.053GPa。弹性模量的最大值和最小值分别为199.575GPa和127.988GPa。研究了LaB₆薄膜在紫外-可见、近红外区的光谱吸收情况。薄膜在紫外-可见波段的吸收受薄膜结构的影响不大,但近红外区的吸收情况受影响较大,出现了不同程度的蓝移或红移。利用四探针电阻法测量了LaB₆薄膜的电阻,据此得到其电阻率。薄膜的导电性能比常规LaB₆较差,其导电性能与半导体相近。更多还原

【Abstract】 Lanthanum hexaboride（LaB₆） was widely used in electron instrument of the modern apparatus.Studies of LaB₆ films were focused on the morphology,structure and physical properties.Optical property of the LaB₆ films was studies seldomly,and it was only used as decorative materials for its special color.In order to study and utilize its special optical properties,SiO₂ was chosen as the substrate.LaB₆ films were deposited on SiO₂ substrate by magnetron sputtering.Argon pressure,substrate bias voltage,substrate temperature and sputtering power were adjusted,respectively.Style profile,AFM,SEM,HRTEM and GIXS were used to study thickness,surface morphology,structure,fracture morphology of the films and diffusion between the LaB₆ films and SiO₂ substrate.Bonding strength,hardness,elastic modulus,optical properties and electron properties were studied systematically,and influence of deposition parameters on properties of the LaB₆ films was also studied.Results of style profile showed that the influence of sputtering power on deposition rate was obvious.Deposition rate was higher than others when the deposition parameters were:sputtering power,61.6W;argon pressure,1.5Pa;bias voltage,-100V;substrate temperature,room-temperature.Maximum value of deposition rate was 19.8nm/min.When the sputtering power decreased to 17.6W, deposition rate changed to 3.22nm/min.Results of AFM showed that the LaB₆ films were smooth and compact.The influence of substrate bias voltage on surface morphology of films was obvious.There was no obvious default was found on the surface of the LaB₆ films with deposition parameters as following:sputtering power,44.0W;argon pressure,1.5Pa;bias voltage, -100V;substrate temperature,400℃.Values of average roughness of the LaB₆ films were about 2nm.Minimum value of average roughness was 1.336nm.Fracture morphologies of the films and their corresponding plane distributions were investigated by SEM.Substrate bias voltage had a deep influence on them. Diffusion between substrate and film was found.Increasing of substrate temperature was favorable to the diffusion.Results of XRD showed that most of the films were crystal.However,the obvious diffraction peaks didn’t turn up in the XRD patterns of the two samples prepared under the condition of sputtering power,17.6W;argon pressure,1.5Pa;bias voltage,-100V;substrate temperature,room temperature and sputtering power,44.0W; argon pressure,1.SPa;bias voltage,-100V;substrate temperature,500℃The predominate face of all the films were（100） face,and that was different from bulk LaB₆.Results of XRD exhibited that average grain sizes were 10～30nm,and the results were consistence with the result of AFM.HRTEM was used to investigate the crystal structure of the LaB₆ film with deposition parameters as follows:sputtering power,44.0W;argon pressure,1.5Pa; bias voltage,-100V;substrate temperature,room temperature,and（100）（110）（111） face were found from the morphology.Bonding strength between the films and substrate were tested.Values of the bonding strength ranged from 110mN to 155mN.There was no discontinuity found in the loading-displacement curves,and the results indentified that elastic-plasticity was good.Values of the films ranged from 21GPa to 8GPa.UV-Vis transmitted spectrum and FT-IR absorption spectrum of the films were studied.Influence of deposition parameters on UV-Vis transmitted spectrum was not evident.There were five absorption peaks,and the wave numbers of the peaks were red shift or blue shift with the change of the deposition parameters.Resistivity of the LaB₆ films was tested.Results showed that electrical conductivity of the films was not as good as normal LaB₆.Values of resistivity ratio of LaB₆ films were from 109Ω·mm²/m to 3609Ω·mm²/m.Deposition parameters influenced electron conductivity of LaB₆ films obviously.更多还原