类金刚石薄膜光学常数拟合模型的合理性研究

由于椭偏光谱测量结果不能直接反映所测量样品材料的结构和光学性质，所以需要利用最小二乘法来拟合分析椭偏光谱数据得到光学常数。而椭偏光谱分析依赖于构建的模型，且可能存在多模型解，因此考虑模型的合理性就显得十分必要。本文采用椭偏法测量了类金刚石薄膜(DLC)的光学常数，分析并拟合了脉冲真空电弧离子技术镀制的类金刚石薄膜的椭偏光谱．获得了光学常数，并对拟合模型的合理性和测量结果的可靠性进行了分析。     

基片温度对PLD制备ZnO薄膜光学常数的影响

光谱椭偏仪被用来研究用脉冲激光沉积方法在Si(100)基片上,温度分别为400,500,600,700 ℃制备的ZnO薄膜的特性。利用三层Cauchy散射模型拟合椭偏参数,计算了每个温度下制备的ZnO薄膜在400~800 nm波长范围内的折射率(n)和消光系数(k)。发现基片温度对光学常数有很大的影响。通过分析XRD表征的晶体结构和 AFM表征的薄膜表面形貌,发现折射率的变化归因于薄膜堆积密度的变化。为了获得具有较好的光学和薄膜质量的ZnO薄膜,相比与其他沉积温度600 ℃或许是最佳的沉积温度。     

射频功率对PECVD制备类金刚石薄膜光学性能的影响

采用射频等离子体增强化学气相沉积(RF-PECVD)法在石英片上生长类金刚石薄膜。通过紫外可见分光光度计、椭偏仪测试手段,研究不同射频功率条件下类金刚石薄膜的光学性能的变化。结果表明,射频功率对类金刚石薄膜的生长具有重要影响,在较低功率下生长的类金刚石薄膜,具有较高的光学透过率和较大的光学带隙。     

基于CVD方法生长在硅基底上立方碳化硅的拉曼散射研究（英文）

立方碳化硅(3C-SiC)薄膜通过化学气相沉积(CVD)制备在Si(100)衬底上。本论文主要通过椭偏光谱仪(SE)和拉曼散射仪对3C-SiC薄膜的微观结构和光学性能进行进一步的研究。根据SE的分析获得3CSiC薄膜厚度;根据拉曼散射的分析:可从TO模式和LO模式的线形形状的拟合得到样品的相关长度和载流子浓度。结果表明:该碳化硅(3C-SiC)薄膜质量随膜厚度增加而得到提高,同时分析了外延层厚度对薄膜特性的影响。     

金刚石薄膜的红外椭圆偏振光谱研究

采用红外椭圆偏振光谱对微波等离子体化学气相沉积法（MPCVD）和热丝化学气相沉积法（H-FCVD）制备的金刚石薄膜在红外波长范围（2.5—12.5μm）的光学参数进行了测量.建立了不同的光学模型，且在模型中采用Bruggeman有效介质近似方法综合考虑了薄膜表面和界面的椭偏效应.结果表明，MPCVD金刚石膜的椭偏数据在模型引入了厚度为77.5nm的硅表面氧化层、HFCVD金刚石膜引入879nm粗糙层之后能得到很好的拟合.最后对两种模型下金刚石薄膜的折射率和消光系数进行了计算，表明MPCVD金刚石薄膜的红外 关键词： 金刚石薄膜 红外椭圆偏振光谱 光学参数 有效介质近似     

双离子束溅射沉积HfO­­2光学薄膜的研究

 用双离子束溅射沉积氧化铪光学薄膜，并对此工艺下制备的氧化铪薄膜进行了光学性质、残余应力、结构特性以及激光损伤特性的研究。实验结果表明，用双离子束溅射沉积的氧化铪薄膜不仅结构均匀,膜层致密,无定形结构，而且具有极低的散射和吸收,均匀的非晶结构,杂质缺陷少,激光损伤阈值高。     

多样品法确定类金刚石薄膜的光学常数与厚度

采用乙烷气体辉光放电法在单晶Si衬底上制备了名义厚度分别为75,150和250nm的类金刚石碳(DLC)薄膜,除沉积时间外其他工艺参数完全一致。使用可变入射角光谱型椭偏仪(VASE)测量了380～1700nm波段的椭偏谱。该研究发现,对单一DLC样品的椭偏数据进行分析时,一定的范围内,假定不同的薄膜厚度均可以得到非常好的拟合结果。结果表明,采用单样品椭偏法拟合时,厚度与光学常数呈现出强烈的关联性,无法快速获得准确的结果。采用多样品椭偏法,对三个样品建立相同的物理模型,假定他们的光学常数相同,进行数据拟合。分析发现该方法可以快速、简便地获得精确的折射率、消光系数以及厚度值。经过检验,结果具有非常好的唯一性。     

利用总积分散射仪对光学薄膜表面散射特性的研究

利用总积分散射仪对不同条件下制备的金属银膜、Y₂O₃稳定ZrO₂（YSZ）薄膜、TiO₂薄膜和1064 nm与532 nm双波长增透膜的表面均方根（RMS）粗糙度和散射特性的变化规律进行了系统研究,并与样品的制备条件、生长过程、材料组成及光学特性等各方面相结合,对测量结果做出了合理解释,从而使总积分散射测量在其他领域的研究得以扩展和应用. 关键词： 光学薄膜 表面散射 总积分散射仪     

椭偏与光度法联用精确测定吸收薄膜的光学常数与厚度

介绍了一种同时利用椭偏仪和分光光度计精确测量薄膜光学常数的方法, 并详细比较了该方法与使用单一椭偏仪拟合结果的可靠性.采用可变入射角光谱型椭偏仪（VASE）表征了250—1700 nm波段辉光放电法沉积的类金刚石薄膜,研究发现当仅用椭偏参数拟合时,由于厚度与折射率、消光系数的强烈相关性,无法得到吸收薄膜光学常数的准确解.如果加入分光光度计测得的透射率同时拟合,得到的结果具有很好的惟一性.该方法无需设定色散模型即可快速拟合出理想的结果,特别适合于确定透明衬底上较薄吸收膜的光学常数. 关键词： 光学常数 光谱型椭偏仪 吸收薄膜 透射率     

椭偏与光度法联用精确测定吸收薄膜的光学常数与厚度

介绍了一种同时利用椭偏仪和分光光度计精确测量薄膜光学常数的方法, 并详细比较了该方法与使用单一椭偏仪拟合结果的可靠性.采用可变入射角光谱型椭偏仪（VASE）表征了250—1700 nm波段辉光放电法沉积的类金刚石薄膜,研究发现当仅用椭偏参数拟合时,由于厚度与折射率、消光系数的强烈相关性,无法得到吸收薄膜光学常数的准确解.如果加入分光光度计测得的透射率同时拟合,得到的结果具有很好的惟一性.该方法无需设定色散模型即可快速拟合出理想的结果,特别适合于确定透明衬底上较薄吸收膜的光学常数.     

银薄膜对光学基底表面粗糙度及光散射的影响

为了研究金属银薄膜与光学基底表面粗糙度和光散射的关系,提出了通过对光学薄膜矢量散射公式积分来获得界面粗糙度完全相关模型和完全非相关模型下其表面的总反射散射的方法.理论计算了光学基底上两种模型在不同厚度银膜下的总反射散射和双向反射分布函数.结果表明,当沉积在光学基底上的银薄膜的厚度大于80 nm后,两种模型下计算的银薄膜的表面总反射散射都等于基底的总积分散射,银薄膜能较好地复现出基底的粗糙度轮廓.实验研究表明为了复现基底的粗糙度,银薄膜的最佳厚度应在80~160 nm之间.     

Ultrafast dynamic ellipsometry measurements of early time laser ablation of titanium thin films

The dynamics of laser ablated titanium thin films are investigated using a recently developed technique that measures time-resolved and one-dimensional spatially-resolved ablation dynamics in a single shot. Ultrafast dynamic ellipsometry, a technique based on space-shifted spectral interferometry, uses the time-dependent frequency of a chirped laser pulse to provide time encoding, allowing the picosecond probing of material dynamics in a single shot. With this technique, the sample is probed at two different incident angles with both s- and p-polarized light, which measures the motion of the material and any change in its complex refractive index. Ultrafast dynamic ellipsometry is applied to study the mechanism of initiation by laser-based optical detonators that employ the ablation of titanium thin films. The resulting data indicate that the titanium is ablated as a fragmented flyer and not as an expanding plasma.     

The influence of gas flow rate on the structural,mechanical, optical and wettability of diamond-like carbon thin films

In this research, diamond-like carbon (DLC) thin films were deposited on silicon substrates by radio-frequency plasma enhanced chemical vapor deposition method using gas mixture of CH₄ and Ar. The effect of different CH₄/Ar gas ratio on the structure, refractive index, transmission and hardness of the DLC thin films were investigated by means of Raman spectroscopy, ellipsometry, Fourier transform Infrared Spectroscopy and nano-indentation methods, respectively. Nuclear resonant reaction analysis was used to measure the amount of hydrogen and carbon in the thin films. Furthermore, wettability of the thin films was achieved by measuring of water contact angle (WCA). The results indicated that the structural properties of the diamond-like carbon thin films are strongly dependent on the composition of gas mixture. Based on ellipsometry results, refractive index of the thin films varied in the range of 1.89–2.06 at 550 nm. FTIR results determined that deposition of DLC thin films on silicon substrate led to an increase of the light transmission in IR region and these films have the potential to be used in silicon optics as the antireflective coatings in this region. Nano-indentation analysis showed that the thin films hardness changed in the range of 7.5–11 GPa. On the other hand hydrogen content and fraction of C?H bonds in the samples increased by an increase in the gas ratio of CH₄/Ar. Also, WCA measurements indicated that WCA for thin films with gas ratio of 3/7 is the most and equal to 79°.     

He-Ne散射光检测光学薄膜激光损伤阈值

准确测定光学薄膜的激光损伤阈值可以衡量光学薄膜的抗激光损伤能力,测定损伤阈值的关键是准确地判定损伤的发生与否。建立了He-Ne散射光检测光学薄膜激光损伤阈值系统。通过测量同一样品点的He-Ne散射光能量变化来判断薄膜表面发生的损伤,并对制备的类金刚石薄膜与HfO₂/SiO₂反射膜进行了阈值测试。与等离子体闪光法的阈值测试结果进行比较,具有较好的一致性。分析表明：He-Ne散射光测试系统能有效地判断出激光诱导损伤,易于实现在线检测。     

Investigation of interface roughness cross-correlation properties of optical thin films from total scattering losses

The interface roughness and interface roughness cross-correlation properties affect the scattering losses of high-quality optical thin films. In this paper, the theoretical models of light scattering induced by surface and interface roughness of optical thin films are concisely presented. Furthermore, influence of interface roughness cross-correlation properties to light scattering is analyzed by total scattering losses. Moreover, single-layer TiO₂ thin film thickness, substrate roughness of K9 glass and ion beam assisted deposition (IBAD) technique effect on interface roughness cross-correlation properties are studied by experiments, respectively. A 17-layer dielectric quarter-wave high reflection multilayer is analyzed by total scattering losses. The results show that the interface roughness cross-correlation properties depend on TiO₂ thin film thickness, substrate roughness and deposition technique. The interface roughness cross-correlation properties decrease with the increase of film thickness or the decrease of substrates roughness. Furthermore, ion beam assisted deposition technique can increase the interface roughness cross-correlation properties of optical thin films. The measured total scattering losses of 17-layer dielectric quarter-wave high reflection multilayer deposited with IBAD indicate that completely correlated interface model can be observed, when substrate roughness is about 2.84 nm.     

银薄膜对光学基底表面粗糙度及光散射的影响

为了研究金属银薄膜与光学基底表面粗糙度和光散射的关系,提出了通过对光学薄膜矢量散射公式积分来获得界面粗糙度完全相关模型和完全非相关模型下其表面的总反射散射的方法．理论计算了光学基底上两种模型在不同厚度银膜下的总反射散射和双向反射分布函数．结果表明,当沉积在光学基底上的银薄膜的厚度大于80nm后．两种模型下计算的银薄膜的表面总反射散射都等于基底的总积分散射,银薄膜能较好地复现出基底的粗糙度轮廓．实验研究表明为了复现基底的粗糙度,银薄膜的最佳厚度应在80～160nm之间．     

Ellipsometry investigation of the effects of annealing temperature on the optical properties of indium tin oxide thin films studied by Drude-Lorentz model

Float glass substrates covered by high quality ITO thin films (Balzers) were subjected for an hour to single thermal treatments at different temperature between 100 °C and 600 °C. In order to study the electric and optical properties of both annealed and not annealed ITO-covered float glasses, ellipsometry, spectrophotometry, impedance analysis, and X-ray measurements were performed. Moreover, variable angle spectroscopic ellipsometry provides relevant information on the electronic and optical properties of the samples. ITO film is modeled as a dense lower layer and a surface roughness layer. The estimated optical density for ITO and the optical density of the surface roughness ITO layer increases with the annealing temperature. In the near-IR range, the extinction coefficient decreases while the maximum of the absorption in the near UV range shift towards low photon energy as the annealing temperature increases. Spectrophotometry was used to estimate the optical band-gap energy of the samples. The thermal annealing changes strongly the structural and optical properties of ITO thin films, because during the thermal processes, the ITO thin film absorbs oxygen from air. This oxygen absorption decreases the oxygen vacancies therefore the defect densities in the crystalline structure of the ITO thin films also decrease, as confirmed both by ellipsometry and X-ray measurements.     

椭偏精确测定透明衬底上吸收薄膜的厚度及光学常数

椭偏仪难以精确测量透明衬底上吸收薄膜光学常数的原因:1)衬底的背面反射光为非相干光, 它的存在会极大的增加拟合难度; 2)衬底光学常数(折射率和消光系数)的差异会影响测量的准确性, 而且会在吸收薄膜的光学常数中表现出来, 需要单独测量其光学常数; 3)厚度与光学常数之间呈现强烈的关联性. 针对以上三个问题, 选择石英玻璃、载玻片、盖玻片和普通浮法玻璃作为研究对象. 采用折射率匹配法消除上述衬底背面反射光的影响. 结果显示, 折射率匹配法能够有效消除折射率在1.43-1.64、波长范围为190-1700 nm波段的石英、浮法玻璃等透明衬底的背面反射光. 之后, 通过拟合椭偏参数ψ和垂直入射时的透过率T₀ 分别得到以上衬底的折射率和消光系数. 拟合得到的结果与文献报道的趋势一致. 最后, 采用椭偏参数和透过率同时拟合的方法(SE+T法)得到类金刚石薄膜(沉积在石英玻璃上)和非晶硅薄膜(沉积在载玻片、盖玻片上)光学常数和厚度的准确解.     

缺氧La0.6Ca0.4MnO3-δ薄膜的光响应特性

采用波长均为532 nm的连续激光和脉冲激光研究了缺氧La0.6Ca0.4MnO3-δ(LCMO)薄膜的光响应特性。分析了在金属态和绝缘态时,缺氧对LCMO薄膜光响应的不同影响。在脉冲宽度7 ns、峰值功率750 mW的脉冲激光作用下,缺氧LCMO薄膜在室温下呈现出明显的光响应信号,其光电导增大36.4%,上升时间约30 ns。由于光子能量大于LCMO的禁带宽度,光子注入在薄膜中产生了电子-空穴对,而电子很容易被氧空位俘获,从而在薄膜中产生大量额外的空穴载流子,大量的空穴载流子可能诱发局域绝缘-金属相变,从而在薄膜中产生明显的光电导效应。实验显示出缺氧钙钛矿薄膜在光电器件上的巨大应用潜力。