不同溅射气压制备W/Si多层膜的实时应力研究

研究了不同溅射气压条件下磁控溅射制备W/Si多层膜过程中的应力变化,使用X射线衍射仪测量了多层膜的结构,使用实时应力测量装置研究W/Si多层膜沉积过程中的应力演变。结果表明,在溅射气压从0.05Pa增加到1.10Pa的过程中,薄膜沉积过程中产生的压应力不断减小并最终过渡为张应力,应力值在溅射气压为0.60Pa时最小,研究结果对减小膜层应力具有指导意义。     

W/B4C、W/C、W/Si多层膜的研究

给出了W/B₄C、W/C、W/Si(钨/碳化硼、钨/碳、钨/硅)周期多层膜的制备和测量研究。用超高真空直流磁控溅射方法制备出周期在1.1~7.2 nm范围内的多层膜样品,采用X射线衍射仪(XRD)小角度测量方法检测多层膜的光学性能,并用透射电镜(TEM)对样品的微观结构进行了研究。结果表明:周期大于1.3 nm的多层膜样品的结构质量高,膜层结构清晰,界面粗糙度小;周期为1.15 nm的多层膜的膜层结构不是很明显;所有膜层均为非晶态,没有晶相生成。结果还表明:采用目前的溅射设备和工艺过程能够制备出满足同步辐射荧光光束线上单色器用多层膜。     

极紫外宽带Mo/Si非周期多层膜偏振光学元件

研究了极紫外宽带多层膜偏振光学元件,包括反射式检偏器与透射式相移片。基于Mo/Si非周期多层膜结构,采用解析与数值优化相结合的方法进行了多层膜的设计;采用磁控溅射技术制备了多层膜。利用X射线衍射仪对非周期多层膜的结构进行了表征,利用德国BESSY-II同步辐射实验室的偏振测量仪对多层膜的偏振特性进行了测试。测量结果表明,在13~19 nm波段,s偏振分量的反射率高于15％;在15~17 nm波段,获得了37％的反射率。宽带多层膜同样可作为宽角偏振光学元件,在13.8~15.5 nm波段,宽带透射相移片的平均相移为41.7°。采用所研制的宽带多层膜相移片与检偏器,建立了宽带偏振分析系统,并对BESSY-II的UE56/1 PGM1光束线的偏振特性进行了系统研究。这种宽带多层膜偏振光学元件可以极大地简化极紫外偏振测量。     

eXTP望远镜用W/Si多层膜

针对增强型X射线时变与偏振探测卫星(eXTP)项目中嵌套式聚焦成像望远镜对柱面镜片上W/Si多层膜的要求,在掠入射角为0.5°,工作波段为1~30keV条件下,设计了非周期W/Si多层膜并优化了薄膜制备工艺。首先,利用分隔板和掩模板对溅射粒子进行准直,同时优化了本底真空度和溅射工作气压,提升了薄膜的成膜质量;然后,通过调整分隔板间距和公转速率提升了在柱面基底上薄膜的沉积均匀性;最后,利用幂指数算法设计了非周期多层膜,并在北京同步辐射光源上进行了多能点反射率测试,得到了与理论设计基本吻合的测试结果。基于优化的制备工艺制备了周期数为80,周期为3.8nm和W膜层厚度占比为0.47的W/Si周期多层膜,其界面粗糙度仅为0.29nm,柱面镜薄膜厚度误差可控制在3%以内,基本满足了eXTP项目中嵌套式掠入射望远镜镜片用多层膜对于成膜质量、沉积厚度均匀性和能谱响应宽度的需求。     

高反射率13nmMo/Si多层膜

采用离子束溅射在不同的工艺参数下制备一系列单层 Mo膜、Si膜及多层膜 ,并用原子力显微镜分析单层膜表面粗糙度及两种材料间的界面扩散。当束流电压超过一定数值时 ,可避免单层膜的柱状生长 ;在 Mo- on- Si和 Si- on- Mo界面中 ,Mo- on- Si界面扩散对反射率的影响更大。采用 X射线衍射仪分析多层膜中 Mo、Si材料的晶体结构 ,均为多晶结构 ,其中 Mo为 ( 1 1 0 )晶向 ,Si为 ( 4 0 0 )晶向。根据上述分析优化工艺参数 ,获得的 1 3nm Mo/Si多层膜反射率达到 60 %。     

软X射线共振反射方法表征Sc/Si多层膜界面化合物成分的计算研究

Sc/Si周期多层膜是极紫外波段的重要材料,但膜层界面处材料原子间的扩散与化合反应严重影响了多层膜反射率。为了无损表征多层膜界面化合物的成分,利用软X射线共振反射的方法,研究了Sc/Si多层膜界面化合物成分。在Si的L吸收边附近,计算了不同周期厚度以及不同界面硅化物成分的Sc/Si多层膜的共振反射率。结果表明,界面硅化物成分不同的膜系在Si的L边处的反射率有明显差异,并且反射率随着膜层中Si化合反应的消耗而降低,证实了软X射线共振反射方法在亚纳米尺度下对化合物的成分进行无损分析的可行性,为后续的实验研究提供参考。     

AlN/VN纳米多层膜的共格生长与超硬效应

研究了亚稳相立方AlN(c-AlN)在AlN/VN纳米多层膜中的形成条件以及c-AlN对纳米多层膜力学性能的影响。一系列不同调制周期的AlN/VN多层膜采用反应磁控溅射法制备,多层膜的微结构采用小角度X射线衍射和高分辨电子显微镜表征,利用微力学探针测量了多层膜的力学性能。结果表明：亚稳的c-AlN因VN的“模板”作用生成于小调制周期的纳米多层膜中,并与VN形成共格外延生长的超晶格柱状晶,从而使多层膜产生硬度和弹性模量升高的超硬效应。随调制周期的增大,c-AlN转变为稳定的六方结构(h-AlN),使多层膜形成纳米晶的“砖墙”型结构。此时多层膜的硬度和弹性模量与混合法则所得值相当。AlN/VN纳米多层膜在小调制周期下产生的超硬效应与c-AlN形成带来的性质变化以及c-AlN与VN形成共格结构所产生的界面交变应变场有关。     

Si含量对TaN/TiSiN纳米多层膜结构和性能的影响

采用磁控溅射技术在304不锈钢和硬质合金刀片上交替沉积TaN、TiSiN层,制备不同Si含量的TaN/TiSiN纳米多层膜.通过X射线衍射仪、扫描电子显微镜、纳米压痕仪、原子力显微镜和摩擦磨损试验机等仪器的测试结果来表征其微观结构、硬度、表面粗糙度及摩擦学等性能.不同Si含量的TaN/TiSiN纳米多层膜均在(200)晶面呈现择优取向,并且衍射峰随着Si含量的增加向右偏移,当Si含量为10％时,衍射峰的偏移量最大.随着Si含量的增加,TaN/TiSiN纳米多层膜的硬度先升高后降低,当Si含量为10％时,硬度最大,达到25.8 GPa.表面粗糙度值随着Si含量的增加先减小后增大,随后又减小,当Si含量为15％时,TaN/TiSiN纳米多层膜的表面最光滑,表面粗糙度值最小,为Ra 2.34 nm.摩擦系数和主切削力均随着Si含量的增加先减小后增大,当Si含量为15％时,摩擦系数最小,耐磨性能最好,主切削力最小;研究结果表明,掺入适量的Si元素可以有效地提高TaN/TiSiN纳米多层膜的硬度、耐磨性能和切削性能.     

Si含量对TaN/TiSiN纳米多层膜结构和性能的影响

采用磁控溅射技术在304不锈钢和硬质合金刀片上交替沉积TaN、TiSiN层,制备不同Si含量的TaN/TiSiN纳米多层膜.通过X射线衍射仪、扫描电子显微镜、纳米压痕仪、原子力显微镜和摩擦磨损试验机等仪器的测试结果来表征其微观结构、硬度、表面粗糙度及摩擦学等性能.不同Si含量的TaN/TiSiN纳米多层膜均在(200)晶面呈现择优取向,并且衍射峰随着Si含量的增加向右偏移,当Si含量为10％时,衍射峰的偏移量最大.随着Si含量的增加,TaN/TiSiN纳米多层膜的硬度先升高后降低,当Si含量为10％时,硬度最大,达到25.8 GPa.表面粗糙度值随着Si含量的增加先减小后增大,随后又减小,当Si含量为15％时,TaN/TiSiN纳米多层膜的表面最光滑,表面粗糙度值最小,为Ra 2.34 nm.摩擦系数和主切削力均随着Si含量的增加先减小后增大,当Si含量为15％时,摩擦系数最小,耐磨性能最好,主切削力最小;研究结果表明,掺入适量的Si元素可以有效地提高TaN/TiSiN纳米多层膜的硬度、耐磨性能和切削性能.     

最小膜层厚度对X射线非周期多层膜光学性能的影响

选用能制备小周期的钨/硅(W/S i)作为膜层材料对,着重研究最小膜层厚度对X射线非周期多层膜光学性能的影响。基于矩阵法计算多层膜反射率和单纯形数值优化方法,设计了入射光子能量为8.0keV,掠入射角的宽度分别为0.85°~1.10°,1.40°~1.70°的X射线超反射镜。结合实际实验制备技术,考虑了W/S i两种膜层材料的最小成膜厚度,确定了膜堆中最小膜层厚度为0.5nm~1.0nm。通过改变最小膜层厚度的值,优化设计了上述条件下的非周期多层膜并对其光学性能进行比较。结果表明:同一个工作波长下,随着多层膜工作角度(掠入射)的增加,膜堆中膜层的厚度减小,最小膜层厚度对其光学性能的影响增加,其光学性能变差。     

Tribological Properties of a C/C–SiC–Cu Composite Brake Disc

A life-size composite brake disc was produced from Si, carbon–carbon composite, copper, and phenol resin. The disc had an outer radius Ø380, inner radius Ø180, and thickness of 36 mm. Chopped carbon fibers were used to reinforce frictional and structural layers. To obtain a preform of each layer, resin and carbon-fibers were mixed and hot-pressed. The preforms were pyrolyzed, and bonded by hot pressing. Finally Si and Cu infiltration in vacuum atmosphere was carried out to obtain a C/C–SiC–Cu _x Si _y composite brake disc. The density of the disc was 2.17 g/cm³. The bending strength was 61 MPa. The heat transfer coefficients in vertical and horizontal directions were 30.7, and 85.2 W/m-°C at 25°C, respectively. Friction coefficients of the C/C–SiC–Cu _x Si _y brake disc were more stable than those of C/C–SiC brake discs. X-ray diffraction analysis showed that Cu formed a compound, Cu₃Si.     

Interlevel optical transitions in Si/Ge x Si1−x /Si quantum wells

Results of mathematical simulation of the hole spectrum and optical absorption in Si/Ge _x Si_1?x /Si quantum wells formed on virtual Ge _y Si_1?y substrates are presented. It is shown that the presence of elastic strains in such a system can significantly change the position of absorption lines in GeSi heterostructures. Selecting the quantum well and virtual substrate compositions can change the intersublevel absorption wavelength in the range from 6 to 12 µm for light polarized in the quantum well plane. When tensile strain is applied, the change in the hole transition intensity under the influence of the light polarized in the quantum well plane reaches a factor of 1.8. Compressive strain changes the intersubband transition intensity by a factor of 1.45.     

Architecture of superthick diamond-like carbon films with excellent high temperature wear resistance

A plasma-enhanced chemical vapor deposition system was used to deposit super thick diamond-like carbon (DLC)-based films ((Si_x-DLC/Si_y-DLC)_n). The aim of this work is to investigate the properties of super thick films to verify that increasing the thickness of DLC films offers the possibility of improving their properties at high temperatures. The investigation revealed that superthick (Si_x-DLC/Si_y-DLC)_n film exhibited excellent tribological property up to 500 °C. One reason is that a thin layer that consists of nanocrystals SiC is formed on the top of wear track. Another is that the stress mostly concentrates near the top surface.     

A system for detecting weak light signals with nanosecond resolution

A simple method for detecting time-resolved weak light signals with a digital oscilloscope, which allows detection of several photons per one excitation period, is described. A system for detecting low-temperature photoluminescence with a resolution of 15 ns has been implemented on the basis of this technique and a method for attaining a resolution of 1–3 ns has been developed. The luminescence kinetics of Si/Ge _x Si_{1 ? x} /Si quantum wells was measured in the near-IR region.     

Formation of Ge/Si and Ge/Ge x Si1−x /Si nanoheterostructures by molecular beam epitaxy

A kinetic diagram of Ge growth on Si is constructed by methods of fast electron diffraction and scanning electron microscopy. Activation energies of morphological transitions from two-dimensional to three-dimensional growth and from hut-clusters to dome-type islands are determined. The curve of the 2D–3D transition has two segments that follow the Arrhenius law and refer to different mechanisms of two-dimensional growth: two-dimensional island mechanism in the temperature range of 300–525 °C with the activation energy of ?0.11 eV and step motion in the temperature range of 525–700 °C with the activation energy of 0.15 eV. Transitions from hut-islands to dome-islands are also observed. The curve constructed for the hut-dome transition is approximated by two exponential segments that obey the Arrhenius law. The hut-dome transition activation energy is 0.11 eV in the temperature range of 350–550 °C and 0.24 eV in the temperature range of 550–700 °C. The maximum density of islands in the case of Ge growth on a Ge _x Si_1?x layer reaches 4 · 10¹¹ cm^?2. An increase in the composition leads to an increase in the density of Ge islands owing to a decrease in the length of migration of Ge adatoms on the Ge _x Si_1?x surface, as compared to the case of Ge growth on Si. The periodicity N, which is manifested as a (2 × N) superstructure, decreases during the reconstruction from 14 to 8 with increasing Ge content in the Ge _x Si_1?x layer. An increase in thickness or temperature leads to a decrease in periodicity and testifies to Ge segregation; in this case, stress relaxation occurs, which reduces the Ge diffisivity.     

Evaluation of the friction of WC/DLC solid lubricating films in vacuum

The accuracy of nanopositioning is to a large extent limited by the friction-caused errors, particularly in vacuum environments. An investigation of the friction behaviour of sp²-bonds dominating diamond like carbon (DLC) coatings and WC_1−x/DLC, WC(N)/DLC multilayer coatings, which are considered to be used in nanopositioning in vacuum, have been performed by a vacuum microtribometer. By using an atomically smooth Si sphere as a counterface, the reciprocating sliding friction was measured at a normal load <5 mN, and running speed at a 1–100 μm/s in ambient air and in ultra high vacuum (UHV) at 10⁻⁷ Pa, and correlated with microstructures and properties of the coatings. When tested in UHV, the coefficient of friction (COF) for pure DLC coatings (thickness: 700 nm) changes significantly between 0.2 and 0.4. Once the thickness of DLC layers is limited to 5 nm by formation of multilayer coatings, the COF in UHV decreases by nearly one order to 0.02–0.05. We suggest that the deformation of DLC films and the transfer films determines COF. Thick DLC coatings can induce more plastic deformation and consumes more energy in sliding resulting in a high COF. Thickening of the transfer film in running leads to a continuous decrease of COF since the deformation of the transfer films turns easier. The low COF of multilayer coatings is mainly due to their confinement of the thickness of DLC films. A consistent velocity-strengthening frictional behaviour of both WC_1−x/DLC and WC(N)/DLC coatings in UHV indicates that the transfer films acting as a thin layer of granular material. Further study of the friction behaviour with the presence of such granular materials might be interesting for the further development of tribological coatings for vacuum applications.     

Effect of counterparts on the friction and wear behavior of polyelectrolyte multilayers

Polyelectrolyte multilayers (PEMs) were prepared on Si substrates by alternative deposition of poly(sodium 4-styrenesulfonate) (PSS) as polyanion and poly (diallyldimethylammonium chloride) (PDDA) as polycation. The PEM film was characterized by means of ultraviolet-visible light absorption spectrometry and atomic force microscopy. The friction and wear behavior of the polymer film sliding against brass, 440C stainless steel, Si₃N₄ and WC balls was evaluated on a microtribometer. It was found that the multilayer film was uniform and compact, and it registered a lowered friction coefficient and extended antiwear life while sliding against soft counterparts, in particular, a brass ball. This could be because the polymeric transfer film had an enhanced adhesion on the soft metallic counterpart in the presence of inter-transferred metallic debris. Contrary to the above, the PEM film had a higher friction coefficient and shorter antiwear life while sliding against Si₃N₄ and WC balls, possibly owing to a higher shearing stress in the presence of stiff and hardly deformable hard counterparts. In other words, the polymeric transfer film on the hard couterparts, if any, would be easily scaled off, leading to decreased antiwear life. Moreover, the differences in the friction and wear behavior of the PEM film sliding against different counterparts were closely related to the differences in the chemical and crystallographic structure of the counterparts (ceramics Si₃N₄ and WC, and metals brass and stainless steel).     

用于热机械微纳加工的掺Al多晶硅加热器

针对热机械式微纳米结构的加工,提出了一种以掺Al多晶硅为材料,集成于微悬臂梁上的加热器.采用Al诱导退火晶化(AIC)方法,在750 K对Al/a-Si∶H复合薄膜低温晶化18 h,制备出掺Al多晶硅.通过低温退火,使复合薄膜的拉曼特征峰由478 cm-1移至520 cm-1,完成由非晶硅向多晶硅的转变;由四探针仪测得...