光学镜面离子束加工的材料去除效率

分析了离子束加工光学镜面的材料去除效率和不I司材料之间的相对去除效率与工艺参数的关系.基于Sigmund 溅射理论.建立了表征去除效率的指标一法向去除速率、体积去除速率和溅射产额与束能、束流以及入射角度之间的关系模型.以石英、微晶和K4玻璃等为样件,实验分析了去除效率与工艺参数的关系,验证了模型的正确性.分析结果表明,材料去除效率随束流线性增大,与束能平方根约呈线性关系;随着入射角度先缓慢增大,约在60～80°达到最大值.然后迅速降为0.不同材料之间的相对去除效率与束流无关;与束能的关系较弱,可以忽略;随角度变化较为明显.     

离子束加工光学镜面的材料去除特性

分析了离子束加工光学镜面的材料去除效率、加工损伤厚度以及表面热效应等材料去除评价指标。基于Sigmund溅射理论,分析了此三个评价指标与离子入射角度和离子能量等加工参数的关系,建立了相关模型。以石英玻璃为例,利用TRIM软件仿真离子溅射过程,分析理论模型各参数,具体研究了三个评价指标与离子能量和入射角度的关系。结果表明:材料去除效率随离子能量的增大而缓慢增大,随入射角度增大而显著增大,60°时的去除效率约为0°时的4.5倍;加工损伤厚度随离子能量增大而近似呈线性增大,随入射角度增大而减小;热效应随离子能量近似呈线性增大,而随入射角度增大而减小。因此,离子束加工工艺过程中,应尽量增大离子束入射倾角来同时提高这三方面的指标。     

CeO_2/SiO_2复合磨粒抛光性能及机制研究

为提高硅片抛光质量与效率,利用均相沉淀法制备CeO2/SiO2复合磨粒,配制绿色环保水基型抛光液对硅片进行化学机械抛光,研究pH值、抛光时间、抛光速度、抛光压力等抛光工艺参数对硅片抛光性能的影响。结果表明:随抛光液pH值增加,材料去除率相应增大;材料去除率在一定时间范围内随抛光时间增加而下降;材料去除量随抛光速度、抛光压力的增加均先增大后减小。推测CeO2/SiO2复合磨粒抛光机制为由于水合作用,在硅片表面形成一层易于磨削的软质层。     

CeO2/SiO2复合磨粒抛光性能及机理研究

为提高硅片抛光质量与效率,利用均相沉淀法制备ＣｅＯ２／ＳｉＯ２ 复合磨粒,配制绿色环保水基型抛光液对硅片进行化学机械抛光,研究ｐＨ值、抛光时间、抛光速度、抛光压力等抛光工艺参数对硅片抛光性能的影响。结果表明：随抛光液ｐＨ值增加,材料去除率相应增大;材料去除率在一定时间范围内随抛光时间增加而下降;材料去除量随抛光速度、抛光压力的增加均先增大后减小。推测ＣｅＯ２／ＳｉＯ２复合磨粒抛光机制为由于水合作用,在硅片表面形成一层易于磨削的软质层。     

考虑氧化作用的CMP接触去除模型分析

针对目前大多数化学机械抛光(CMP)材料去除模型没有考虑到氧化薄膜作用的现象,提出一种考虑氧化后的芯片与磨粒之间的接触模型,该模型的建立基于接触力学理论和接触微凸体由弹性变形向弹塑性变形及最终向完全塑性变形的转化过程,并将该模型与传统的塑性去除模型进行了对比分析。结果表明:低压CMP精抛过程中,磨粒在外载荷的作用与氧化后的芯片表面发生接触去除,且随着工作载荷的增大,芯片表面的压痕深度、卸载回弹量、最大应力和材料去除量也随之增大;当载荷为1200-4250n N时,芯片弹塑性接触去除率小于传统理想塑性接触去除率;当载荷约为1650n N时,相对误差达到最大值28%。因此,氧化后的芯片与磨粒并非简单的塑性去除,考虑氧化后的芯片去除将更有利于后续精确地统计实际CMP去除率,为进一步优化CMP工艺提供一定的理论基础。     

电火花加工中电极材料对加工性能影响的试验研究

以电火花多电极加工3Cr13模具型腔为研究对象,以提高材料去除率和降低电极损耗为目标,对负极性标准切入加工时不同电极材料的电火花加工性能(加工效率、电极损耗)进行研究,设计并进行了不同工艺参数下紫铜电极和Cu50W铜钨合金电极加工试验,获得了不同条件下的材料去除率和电极相对损耗参数,并对多电极电火花加工工艺及经济性进行了分析,结果表明:相同工艺参数下,加工性能因电极材料热学性能不同而不同,Cu50W铜钨合金的材料去除率约为紫铜的85.7％,而电极相对损耗约为紫铜的42.9％,从而为电火花加工不锈钢模具材料的电极选择提供了理论依据.     

离子束抛光去除函数计算与抛光实验

由于传统的离子抛光工艺采用的确定去除函数的方法操作复杂且成本很高,本文提出了利用法拉第杯对离子束流空间分布进行测量、标定的方法,并计算得到不同离子源工作参数对应的去除函数。首先,基于离子束抛光材料去除原理,研究了离子束抛光过程中束流分布与能量对去除函数的影响,并提出简化的离子束抛光去除函数模型。然后,设计实验并得出离子束流空间分布与去除函数相关参数间的关系,计算得到了不同离子源工作参数产生的离子束流对应的去除函数。对硅和融石英玻璃的相关实验表明:利用法拉第杯扫描结果计算相同材料的去除函数的单位时间体积去除率与实际测量值误差小于2%。结合抛光实验,对Φ800mm碳化硅表面硅改性层平面镜进行抛光,得到的初始面形误差均方根(RMS)值为57.886nm,两次抛光后RMS值为11.837nm,收敛率达到4.89,满足精密光学加工对去除函数的确定性及精度的要求,并大大提升了确定去除函数的效率。     

蓝宝石基片的单面研磨工艺研究

为了实现蓝宝石基片的快速平坦化,对蓝宝石基片进行系统的单因素单面研磨试验,研究了磨料种类、磨料粒径、研磨盘转速、研磨压力以及磨料质量分数等研磨工艺参数对蓝宝石基片材料去除率和表面粗糙度的影响规律。试验结果表明:金刚石磨料适合蓝宝石基片的单面研磨;随着磨料粒径的增大,材料去除率逐渐增大,表面越来越粗糙;随着研磨盘转速的增大,材料去除率先增大后减小,表面粗糙度值在20～60 r/min区间变化不大,稳定在Ra 0. 12～Ra 0. 13μm之间,而在60～100 r/min区间波动较大,当研磨盘转速为60 r/min时,材料去除率最大;随着研磨压力的增大,材料去除率逐渐增大,而表面粗糙度值越来越低;随着磨料质量分数的增大,材料去除率先增大后减小,表面粗糙度先增大然后趋于平缓,当磨料质量分数为3 wt%时,材料去除率最大,且表面粗糙度值相对较小;最后通过正交试验优化了工艺参数,在优化的工艺条件下依次选用粒径为W40、W14、W3的金刚石磨料对蓝宝石基片进行粗研、半精研及精研,取得了表面粗糙度为Ra 7. 9 nm的平坦表面。     

充磁与未充磁烧结钕铁硼电火花加工对比试验研究

钕铁硼硬度高、脆性大,且充磁后具有高磁性力.电火花加工是钕铁硼的重要加工方法.为探寻充磁与未充磁烧结钕铁硼在电火花加工过程中的工艺差异和规律,采用单因素试验方法,开展对比试验,研究放电参数(脉冲宽度、峰值电流和脉冲间隔)对充磁与未充磁烧结钕铁硼的材料去除率、表面粗糙度和重铸层的影响.结果 表明:随脉冲宽度的增加,充磁烧结钕铁硼的材料去除率增大,而未充磁烧结钕铁硼的材料去除率先增大后略有减小,充磁与未充磁烧结钕铁硼表面粗糙度值均增大,重铸层均增厚且内部出现裂纹;随峰值电流的增加,两者材料去除率和表面粗糙度值均增大;随脉冲间隔的增加,两者材料去除率和表面粗糙度值均减小;在较大的放电参数值下,充磁烧结钕铁硼的材料去除率和表面粗糙度明显优于未充磁烧结钕铁硼.     

充磁与未充磁烧结钕铁硼电火花加工对比试验研究

钕铁硼硬度高、脆性大,且充磁后具有高磁性力.电火花加工是钕铁硼的重要加工方法.为探寻充磁与未充磁烧结钕铁硼在电火花加工过程中的工艺差异和规律,采用单因素试验方法,开展对比试验,研究放电参数(脉冲宽度、峰值电流和脉冲间隔)对充磁与未充磁烧结钕铁硼的材料去除率、表面粗糙度和重铸层的影响.结果 表明:随脉冲宽度的增加,充磁烧结钕铁硼的材料去除率增大,而未充磁烧结钕铁硼的材料去除率先增大后略有减小,充磁与未充磁烧结钕铁硼表面粗糙度值均增大,重铸层均增厚且内部出现裂纹;随峰值电流的增加,两者材料去除率和表面粗糙度值均增大;随脉冲间隔的增加,两者材料去除率和表面粗糙度值均减小;在较大的放电参数值下,充磁烧结钕铁硼的材料去除率和表面粗糙度明显优于未充磁烧结钕铁硼.     

SURFACE INTEGRITY AND REMOVAL RATE OF SILICON SPUTTERED WITH FOCUSED ION BEAM

This paper investigates the micromachinability of (100) silicon by focused gallium ion beam sputtering at normal incident angle. Effect of the beam parameters (dose, aperture and accelerating voltage) and the beam scanning parameters (pixel spacing, dwell time, retracing time and scanning type) on the surface integrity and material removal rate were studied. Statistical models derived from factorial experiments were used to predict the sputtered depths and material removal rates of silicon. The sputtering depth increased with higher accelerating voltage, more ion dose, shorter pixel spacing, and longer dwell time. Similar trends were found for predicting the material removal rate. A surface roughness in the range 2-5 nm was achieved, and was found to be linearly dependent on the pixel spacing.     

The use of amphipathic polymers for cryo electron microscopy of NADH:ubiquinone oxidoreductase (complex I)

Atom removal from surfaces via bombardment by ion beams – ion beam sputtering or ion milling – is a widely employed technique to form geometric structures in materials. In this work we present and test a new method to achieving uniform material removal from an irregular surface. The method is based on ion milling at off-normal incidence under four consecutive perpendicular azimuthal specimen orientations. Mathematical analysis shows that uniform ion milling of an uneven surface is achieved at the polar angle of incidence θ where the quantity     has its maximum [ Y (θ) is the number of removed atoms per incident ion].
The four-azimuth milling procedure is tested successfully for a 30 keV Ga⁺ beam on a suspended but wrinkled Si₃N₄/Au bilayer foil and on truncated Si pyramids with slopes up to 40°. Despite the variations in local surface orientations, uniform milling is achieved at a polar incidence angle of 45° and four consecutive azimuths of 0°, 90°, 180° and 270°.     

高能离子束辅助沉积制备钛纳米膜

用离子束溅射沉积和高能离子束辅助沉积方法制备了具有择尤性的钛纳米薄膜,并采用原子力显微镜、X射线衍射仪和俄歇电子谱仪研究了试样表面预处理、离子束流和温度等离子束工艺参数对钛薄膜结构的影响。结果表明：离子束溅射沉积的钛膜在[002]和[102]晶向上呈现出明显的择尤生长现象,并分别在该两个晶向上表现出纳米晶型和非纳米晶型结构;当用高能离子束辅助沉积时,[102]晶向择尤生长现象消失,且钛膜的结构对束流变化较为敏感,束流较低时,钛膜为纳米结构且择尤生长现象减弱,而束流增加时晶粒长大,择尤生长现象叉增强。另外钛膜容易受到氧的污染,并随辅助离子强度增加而增强。     

Low damage lamella preparation of metallic materials by FIB processing with low acceleration voltage and a low incident angle Ar ion milling finish

Metallic materials are known to be very sensitive to Gallium (Ga) focused ion beam (FIB) processing. Crystal defects formed by FIB irradiation degrade the transmission electron microscope image quality, and it is difficult to distinguish original defects from FIB process-induced damage. A solution to this problem is the low acceleration voltage and low incident angle (LVLA) Argon ion milling, which can be incorporated as an extensional countermeasure for FIB damage removal and eventually for preparation of high-quality lamellae. The transmission electron microscope image quality of iron single crystal could be improved by removing crystal defects using the low acceleration voltage and low incident angle Argon ion milling finish. Lamella quality of the processing result was almost similar with that of the conventional electrolytic polishing. As a practical application of the process, low damage lamella of stainless cast steel could be prepared. Effectiveness of the FIB system equipped with the low acceleration voltage and low incident angle Argon ion milling function as a tool to make high-quality metallic material lamellae is illustrated.     

宽视场绝对辐射计杂散光特性研究

摘要：卫星太阳辐射监测仪在轨飞行中采用太阳扫过宽视场绝对辐射计视场期间动态测量太阳辐照度的方法,测量过程中进入辐射计接收腔的杂散光对测量精度带来影响,本文通过模型软件分析、风云辐射计外场标定测量和神舟三号辐射计在轨数据修正三个方面对宽视场辐射计的杂散光随角度变化分布进行了分析, 1）随光线入射角增大,杂散光影响基本呈线性增大;2）太阳辐射监测仪宽视场绝对辐射计无遮拦视场角18.4,对0～7视场进行了模拟分析,在7入射角时,杂光影响为0.63％,地面通过标定方法测量得到的结果为0.79％;3）神舟三号飞船上的辐射计视场角为10.4,视场角小,消光光栏多,杂散光的影响相对较小。以模型仿真结果对星上获得数据进行了修正,结果表明,通过杂光修正降低了系统误差。     

Comparison of ion beam sputtered chromium and iridium films for electron microscopy applications

The structure and composition of thin, conductive metallic films of chromium and iridium that are typical of the coatings used for electron microscopy is described. The purpose of this study was to determine the grain size and composition of the films deposited, with thicknesses of 1 nm, 2.5 nm, and 5 nm, onto amorphous carbon films using ion beam sputtering with argon as the sputtering gas. A comparison between chromium films deposited under conditions of liquid nitrogen (LN) trapping or of no trapping revealed slight differences in their microstructure. As expected, the grain size of the films increased with the thickness, and the average grain sizes varied between 10 and 25 nm. Grain size was also found to depend on the source of ion beam energy; the correlation between grain size and beam energy was more pronounced in the iridium films than in the chromium films. This effect was greater when the deposition chamber was not LN trapped. As the ion beam energy increased from 18 W to 24 W, there was a corresponding increase in grain size in some of the films. Although transmission electron diffraction analysis indicated the presence of about 5% chromium oxide in the chromium films, no oxide was detected in the iridium films.     

Finite element prediction of material removal rate due to traveling wire electrochemical spark machining

Manufacturing engineers are facing new challenges during machining of electrically nonconducting or partially conducting materials such as glass, quartz, ceramics, and composites. Traveling wire electrochemical spark machining (TW-ECSM), a largely unknown technology, has been applied successfully for cutting these types of materials. However, hardly any theoretical work has been reported related to machining performance of TW-ECSM process. The present work is an attempt in this direction. In the present work, a 3-D finite element transient thermal model has been developed to estimate the temperature field and material removal rate (MRR) due to Gaussian distributed input heat flux of a spark during TW-ECSM. First, the developed code calculates the temperature field in the workpiece and then MRR is calculated using this temperature field. The calculated MRR has been compared with the experimental MRR for verifying the approach. Computational experiments have been performed for the determination of energy partition and spark radius of a single spark. The effects of various process parameters such as energy partition, duty factor, spark radius, and ejection efficiency on MRR have been reported. It has been found that MRR increases with increase in energy partition, duty factor, and ejection efficiency but decreases with increase in spark radius.     

Analyzer system capable of determining energy and direction of charged particles in ultrahigh vacuum

We have constructed and tested a system capable of measuring the energy of charged particles emitted from a sample at any angle relative to the sample or the incident beam of exciting particles. The energy analysis is accomplished by a 180 degrees spherical deflecting-type analyzer, operated at constant pass energy with a series of electrostatic lenses. The analyzer system is properly apertured to accept incoming particles from a spot of 1.5 mm diameter at the sample and within a cone of 2.5 degrees half-angle. The lens system used has constant transmission independent of the incident energy. The energy analyzer is independently rotatable about two orthogonal axes, giving it complete freedom of access to any angle of collection relative to the sample orientation. The sample can rotate about two orthogonal axes so that any angle of incidence can be used. Specific examples are given of the performance of the system when used for the measurement of the angular distribution of photoelectrons excited by synchrotron radiation.