脉冲激光对类金刚石（DLC）薄膜的热冲击效应研究

强激光辐照红外热像系统时，可造成系统的干扰和破坏，激光的波长不同，对系统的破坏效果也不同.为了保护红外系统窗口以及提高窗口的透过率，红外窗口广泛沉淀类金刚石（DLC）薄膜.当入射的激光波长位于红外系统响应波段外时，激光对系统的破坏首先是激光对DLC薄膜的破坏.以波长为1.06μm的激光为例，研究了脉冲激光对DLC薄膜的损伤机理，建立了DLC薄膜的热冲击效应模型，并通过求解热传导和应力平衡方程，得出了薄膜的温度场和应力场分布.理论分析表明，热应力破坏在脉冲强激光对DLC膜的损伤机理中占主导地位.当 辐照能量密度为E₀=100mJ·cm^-2时，在薄膜表面距光斑中心约 40μm区域内的压应 力明显超出其断裂强度，将造成膜层的剥离、脱落.理论分析与实验结果基本相符，表明建 立热冲击效应模型的正确性. 关键词： 激光辐照 类金刚石（DLC）薄膜 热冲击效应     

类金刚石薄膜及其进展

为了使研究者能更详细地了解类金刚石（DLC）薄膜的研究现状,综述了类金刚石薄膜的特性及应用,分析对比了目前常用的一些类金刚石薄膜的制备方法,包括物理气相沉积法（PVD）和化学气相沉积法（CVD）,并对类金刚石薄膜的抗强激光损伤特性以及提高其激光损伤阈值的方法进行了论述。结果发现,利用PVD法制备的DLC膜的硬度可以达到40 GPa~80 GPa,且薄膜的残余应力可以达到0.9 GPa~2.2 GPa之间,而CVD法则由于反应气体的充入导致类DLC薄膜的沉积速率大大降低,故使用率不高。同时,优化膜系的电场强度设计,采用合理的制备工艺,进行激光辐照后处理,施加外界电场干预均可有效地提高DLC薄膜的抗激光损伤能力, 且目前的DLC薄膜的激光损伤阈值可达到2.4 J/cm2。     

RF-PECVD法制备大面积类金刚石薄膜性能的研究

采用RF-PECVD法在锗、硅红外光学窗口上制备了大面积(基底直径φ=150～250mm)类金刚石薄膜.采用拉曼光谱分析了大面积DLC膜的结构组成,对RF-PECVD法制备的大面积DLC膜的均匀性、红外光学性能、机械力学性能以及其抗恶劣环境的能力进行了检测和分析.膜层厚度均匀性在3%以内.锗、硅红外窗口双面镀制DLC膜后,极值透过率分别达92%和96%以上,可显著提高红外光学窗口的显微硬度.膜层具有极强的抗盐雾、耐海水腐蚀和抗摩擦的能力.     

DLC/Ag/DLC复合多层薄膜光学性能

采用等离子体增强化学气相沉积类金刚石(DLC)薄膜、高真空磁控溅射镀膜设备溅射Ag靶的方法制备了不同厚度Ag、DLC层的DLC/Ag/DLC多层膜,分别用紫外可见分光光度计、四探针测试仪对样品的光学性能、电学性能进行了测试.结果表明,随着Ag层厚度的增加,DLC/Ag/DLC多层膜透射率先增后减,外层DLC薄膜和内层DLC薄膜对透射率影响基本一致,随着厚度增加透射率先增后减,在内外层厚度为40 nm,Ag夹层厚度为16 nm时,DLC(30 nm)/Ag(16 nm)/DLC(40 nm)膜在550 nm处的透射率高达94.4%,电气指数高达112.4 ×10-3Ω-1,远远超过现有透明导电膜的电气指数(FTC≈20×10-3Ω-1).     

溶胶-凝胶法制备ZrO2/SiO2双层减反硬膜

以锆酸丙酯[Zr(OPr)4]、正硅酸乙酯(TEOS)为原料, 用溶胶-凝胶(sol-gel)提拉法涂膜, 制备高透过的λ/ 4～λ/ 4型ZrO2/SiO2双层减反膜.该减反膜的表面均匀, 均方根(RMS)粗糙度为1.038 nm, 平均粗糙度(RA)为0.812 nm.制备的双层减反膜具有很好的减反效果, 在石英玻璃基片二面涂膜, 在激光三倍频波长351 nm处透射比达到99.41%, 比未涂膜石英玻璃基片的透射比提高了6.14%;在基频波长1053 nm处透射比达到99.63%, 比未涂膜K9光学玻璃基片的透射比提高了7.67%.膜层具有较高的激光损伤阈值, 在激光波长为1053 nm, 脉冲宽度为1 ns时, 薄膜的激光损伤阈值达到16.8 J/cm2.膜层具有良好的耐擦除性能.     

铜基类金刚石膜功能梯度材料作为散热材料的研究

随着电子技术、信息产业的发展, Cu在微型散热材料、电子封装材料上应用日益广泛. Cu在应用过程中存在强度低、易氧化、易磨损等缺点. 采用等离子体复合沉积技术, 在铜基体上制备了Ti/TiC/DLC功能梯度材料, 改善铜基体与美金刚石(DLC)膜的结合力, 强化了铜的机械性能. 瞬态热反射法检测结果表明, DLC功能梯度材料不会影响铜基体的散热效果.     

脉宽压缩光栅用多层膜制备和性能测试

给出了以413 nm作为写入波长,1053 nm作为使用波长的多层介质光栅膜的设计,计算表明膜系H3L(H2L)^9H0.5L2.03H满足光栅膜的要求.最后给出了制备得到的样品光学特性测试,结果表明在使用波长和曝光波长处满足设计要求,其抗激光损伤阈值在光正入射和51.2°入射时分别为14.14 J/cm2和9.32 J/cm2,膜系的应力表现为压应力.     

向列相液晶染料可调谐激光器的研究

对向列相液晶染料的可调谐激光器进行了光学特性研究. 以650 nm为中 心波长设计了SiO₂和TiO₂多层膜的一维光子晶体, 以激光染料与向列相液晶的混合物作为增益介质层, 制备了波长可调谐激光器.用Nd: YAG倍频脉冲激光器输出的532 nm激光抽运所制备的激光器样品得出如下光学特性: 激光发射波长随温度调谐范围为605.5---639.8 nm, 达到34.3 nm, 随电压调谐范围为634.5---619.5 nm, 达到15 nm. 发射激光每脉冲的阈值能量为12.3 μJ, 激光线宽小于1 nm.     

卫星激光通信滤光膜的研制

为满足卫星激光通信中超高速数据传输的特殊要求,采用电子束和离子辅助沉积技术,制备了532nm、632nm和1 064nm波长处高反射,808nm和1 550nm处高透射的多波段滤光膜.选取了H4和SiO2作为高低折射率材料,通过对膜系设计曲线的不断优化,减少了灵敏层的个数,得到了相对易于制备的膜系结构;采用电子束加热蒸发方法并加以离子辅助沉积系统制备薄膜,采用光控与晶控同时监控的方法控制膜厚;通过不断调整工艺,提高了薄膜的抗激光损伤能力,减小了膜厚控制误差,提高了透射波段的透过率及反射波段的反射率,最终得到了光谱性能较好的滤光膜.该薄膜能够承受雨淋、盐雾、高低温等环境测试,满足使用要求.     

一种适合微条气体室探测器的理想衬底材料

微条气体室(Micro-strip Gas Chamber,MSGC)探测器最严重的问题是电荷积累效应,通过选择合适的衬底材料可以有效的避免.为此,D263玻璃上沉积类金刚石(Diamond-like Carbon,DLC)膜来进行表面改性,从而制备DLC膜D/263玻璃双层结构作为MSGC衬底.拉曼光谱说明DLC膜是由sp³(σ键)和sp²(π键)杂化碳原子组成,属于电子导电型材料,并且沉积出的是一种高质量的DLC膜;I V曲线表明DLC膜改性后的样品具有非常稳定和理想的电阻率,其值在10⁹—10¹²Ω·cm间;C-F曲线显示改性后样品具有小而稳定的电容.DLC膜D/263玻璃的优良性能正是MSGC衬底的最佳要求,这种新型材料用作衬底将有效克服电荷积累效应和衬底不稳定性.     

Current state-of-the-art of pulsed laser deposition of optical waveguide structures: Existing capabilities and future trends

Pulsed laser deposition (PLD) has now reached a stage of maturity where the growth of thin films is routine. All that is required is a pulsed ultra-violet (UV) wavelength laser, a vacuum chamber, a target, and a substrate placed in near proximity to the plasma plume. Whether the film that you grow is the film that you need, and whether the thickness, uniformity, optical quality, stoichiometry, degree of crystallinity, orientation and much more is what is desired is another question entirely. PLD is both a science and an art and there are many tricks-of-the-trade that need to be considered to ensure that materials grown are the materials wanted. This paper discusses the practicalities of PLD systems, target geometries, heating regimes for successful epitaxial growth of crystalline films, the problem of particulates, laser sources to use, and in the context of our most recent PLD system, the number of independent lasers and targets used. We show that the use of multiple targets permits a combinatorial approach, whereby stoichiometry can be adjusted to grow designer materials, and in particular multilayer systems, ideally suited for active optical waveguides, a truly demanding end application where optical quality and in-plane losses must be reduced to an absolute minimum.     

Fabrication and characterization of freestanding ultrathin diamond-like carbon targets for high-intensity laser applications

Here, we report the fabrication of diamond-like carbon (DLC) thin films using pulsed laser deposition (PLD). PLD is a well-established technique for deposition of high-quality DLC thin films. Carbon tape target was ablated using a KrF (248 nm, 25 ns, 20 Hz) excimer laser to deposit DLC films on soap-coated substrates. A laser fluence between 8.5 and 14 J/cm² and a target to substrate distance of 10 cm was used. These films were then released from substrates to obtain freestanding DLC thin foils. Foil thicknesses from 20 to 200 nm were deposited using this technique to obtain freestanding targets of up to 1-inch square area. Typically, 100-nm-thick freestanding DLC films were characterized using different techniques such as AFM, XPS, and nano-indentation. AFM was used to obtain the film surface roughness of 9 nm rms of the released film. XPS was utilized to obtain 74 % sp², 23 % sp³, and 3 % C–O bond components. Nano-indentation was used to characterize the film hardness of 10 GPa and Young’s modulus of 110 GPa. Damage threshold properties of the DLC foils were studied (1,064 nm, 6 ns) and found to be 7 × 10¹⁰ W/cm² peak intensity for our best ultrathin DLC foils.     

离子束流后处理对类金刚石薄膜激光损伤特性的影响

类金刚石薄膜激光损伤阈值低,已经严重制约其在红外激光系统中的应用。基于非平衡磁控溅射技术,在硅基底上沉积类金刚石薄膜;采用离子束流后处理技术,用正交实验法确定影响处理效果的主要因素,对已沉积完成的DLC薄膜进行离子束轰击;在不同处理工艺下,观测薄膜样品的光学常数及拉曼光谱,最后进行了激光损伤测试。从测试结果可知,离子束流后处理参数:离子能量1000eV、放电电流30~40mA、轰击时间8min时,透射率由原来的60.65%提高到了65.98%;消光系数在900nm后明显降低,DLC薄膜的激光损伤阈值从0.69J/cm2提高到1.01J/cm2。     

XeCl（308nm）脉冲准分子激光淀积类金刚石薄膜

利用ＸｅＣｌ（３０８ｎｍ）脉冲准分子激光淀积技术在功率密度５×１０８Ｗ／ｃｍ２、室温、真空度１０－３Ｐａ的条件下，制备出不含氢成分的类金刚石薄膜，研究了类金刚石薄膜的特性及其随制备工艺条件的变化规律。研究了激光诱导的碳等离子体发射光谱，探讨了类金刚石薄膜的形成机理。     

脉冲准分子激光淀积薄膜的实验研究

 利用两种脉宽(30ns，500fs)的KrF准分子激光展开了淀积类金刚石薄膜的实验研究，并且成功地制备了大面积不含氢成分的HF-DLC薄膜，运用时空分辨的等离子体发射光谱诊断系统和离子探针系统研究了等离子体特性对薄膜性能的影响。尝试了利用准分子激光制备非晶硅薄膜，研究了实验参数对非晶硅薄膜制备的影响，并分析了制备具有良好电学和光学性能的非晶硅薄膜的条件。     

Optical and Electrical Properties Evolution of Diamond-Like Carbon Thin Films with Deposition Temperature

Optical and electrical properties of diamond-like carbon （DLC） films deposited by pulsed laser ablation of graphite target at different substrate temperatures are reported. By varying the deposition temperature from 400 to 25℃, the film optical transparency and electrical resistivity increase severely. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting the deposition temperature, which is critical to many applications. DLC films deposited at low temperatures show excellent optical transmittance and high resistivity. Over the same temperature regime an increase of the spa bonded C content is observed using visible Raman spectroscopy, which is responsible for the enhanced transparency and resistivity properties.     

脉冲准分子激光淀积薄膜的实验研究

利用两种脉宽 (30ns,5 0 0fs)的KrF准分子激光展开了淀积类金刚石薄膜的实验研究 ,并且成功地制备了大面积不含氢成分的HF DLC薄膜 ,运用时空分辨的等离子体发射光谱诊断系统和离子探针系统研究了等离子体特性对薄膜性能的影响。尝试了利用准分子激光制备非晶硅薄膜 ,研究了实验参数对非晶硅薄膜制备的影响 ,并分析了制备具有良好电学和光学性能的非晶硅薄膜的条件     

Pulsed laser deposition and characterization of multilayer metal-carbon thin films

Cobalt-DLC multilayer films were deposited with increasing content of cobalt, keeping carbon content constant by pulsed laser deposition technique. A cobalt free carbon film was also deposited for comparison. Excimer laser was employed to ablate the materials onto silicon substrate, kept at 250 °C, while post-deposition annealing at 400 °C was also performed in situ. The formation of cobalt grains within the carbon matrix in Co-DLC films can be seen through scanning electron and atomic force micrographs while no grains on the surface of the cobalt-free DLC film were observed. Raman spectra of all the films show D- and G-bands, which is a confirmation that the films are DLC in nature. According to Vibrating sample magnetometer (VSM) measurements, the DLC films with cobalt revealed ferromagnetic behaviour whereas the cobalt free DLC film exhibited diamagnetic behaviour. The pure DLC film also shows ferromagnetic nature when diamagnetic background is subtracted. Spectroscopic Ellipsometry (SE) analysis showed that the optical band gaps, refractive indices and extinction coefficients of Co-DLC films can be effectively tuned with increasing content of cobalt.     

Effects of the ion-beam voltage on the properties of the diamond-like carbon thin film prepared by ion-beam sputtering deposition

Diamond-like carbon(DLC) thin film is one of the most widely used optical thin films.The fraction of chemical bondings has a great influence on the properties of the DLC film.In this work,DLC thin films are prepared by ion-beam sputtering deposition in Ar and CH4 mixtures with graphite as the target.The influences of the ion-beam voltage on the surface morphology,chemical structure,mechanical and infrared optical properties of the DLC films are investigated by atomic force microscopy(AFM),Raman spectroscopy,nanoindentation,and Fourier transform infrared(FTIR) spectroscopy,respectively.The results show that the surface of the film is uniform and smooth.The film contains sp2 and sp3hybridized carbon bondings.The film prepared by lower ion beam voltage has a higher sp3 bonding content.It is found that the hardness of DLC films increases with reducing ion-beam voltage,which can be attributed to an increase in the fraction of sp3 carbon bondings in the DLC film.The optical constants can be obtained by the whole infrared optical spectrum fitting with the transmittance spectrum.The refractive index increases with the decrease of the ion-beam voltage,while the extinction coefficient decreases.