Optimization of thickness uniformity of coatings on spherical substrates using shadow masks in a planetary rotation system

A model is developed to improve thickness uniformity of coatings on spherical substrates rapidly and au- tomatically using fixed shadow masks in a planetary rotation system. The coating thickness is accurately represented by a function composed of basic thickness, self-shadow effect, and shadow mask function. A type of mask with parabolic contours is proposed, and the thickness uniformity of coatings on spheri- cal substrates can be improved in a large range of ratios of clear aperture （CA） to radius of curvature （RoC） by optimizing shadow masks using a numerical optimization algorithm. Theoretically, the thick- ness uniformity improves to more than 97.5% of CA/RoC from -1.9 to 1.9. Experimentally, the thickness uniformities of coatings on a convex spherical substrate （CA/RoC = 1.53） and on a concave spherical substrate （CA/RoC=-1.65） improve to be better than 98.5% after corrected by the shadow masks.     

Self-assembled triangular and labyrinth buckling patterns of thin films on spherical substrates

We investigated the possibility of controlling thin film buckling patterns by varying the substrate curvature and the stress induced therein upon cooling. The numerical and experimental studies are based on a spherical Ag core/SiO(2) shell system. For Ag substrates with a relatively larger curvature, the dentlike triangular buckling pattern comes out when the film nominal stress exceeds a critical value. With increasing film stress and/or substrate radius, the labyrinthlike buckling pattern takes over. Both the buckling wavelength and the critical stress increase with the substrate radius.     

Influence of thickness on the domain structure of barium-strontium-titanate films on MgO substrates

Ba_0.8Sr_0.2TiO₃/MgO(001) heterostructures are studied using atomic-force spectroscopy in several modes (the contact and semicontact modes and that of piezoelectric response) to obtain information on the relief and the distribution of the electric potential on the surface. Based on data obtained for films with different thicknesses, the correlation between the domain sizes and orientations and the film thickness and the surface relief is established. It is shown that the films with thicknesses less than 36 nm contain only aa domains whose dimensions decrease with increasing film thickness. The films with thicknesses greater than 36 nm contain only c domains whose dimensions increase with increasing film thickness.     

Measurement of the thickness of thin films deposited on smooth non-planar substrates.

A simple Tolansky interferometer has been built under a low power microscope for measuring the thickness of thin films. A new procedure of evaluating the interferograms has been developed which is applicable whenever the substrate carrying the film is not plane but smoothly curved.     

Effects of epitaxial films of nanometric thickness on the X-ray photoelectron diffraction intensities from substrates

The effects on the X-ray photoelectron diffraction intensities from the substrate produced by epitaxial NiO(0 0 1) films of various thickness deposited on Ag(0 0 1) were investigated. The variations in the Ag XPD curves induced by the NiO films can be explained in terms of multiple scattering of the electrons emitted by the substrate atoms along the close-packed rows of the overlayer. Intensity minima in the XPD curves from the substrate in correspondence to intensity maxima in the XPD curves from the overlayer are observed when the thin film is commensurate with the substrate. For films of suitable thickness, the analysis of XPD curves from the substrate allows one to get information about the structure of the film and of the film–substrate interface.     

弯月面涂胶均匀性改进

针对大面积衍射光学元件制作过程中对光刻胶均匀涂覆的困难,研究弯月面均匀涂胶方法。利用沟槽型弯月面涂胶机,分析影响光刻胶厚度和厚度均匀性的因素。从实验上验证了光刻胶的胶厚和涂覆扫描速率的正相关关系。分析了光刻胶的浓度、基片与涂覆器刀口间隙、供胶速率等因素对胶厚及胶厚均匀性的影响。利用非接触式的激光微位移传感器监测基片和涂覆器刀口间隙,控制此间隙的抖动小于15 m,优化系统运行的稳定性,提升了弯月面涂覆胶厚的均匀性,实现了胶厚峰谷值偏差3%和标准偏差0.5%的均匀光刻胶涂覆,能够满足脉宽压缩光栅等制作过程中对光刻胶均匀涂覆的需求。     

Improvement of thickness uniformity and elements distribution homogeneity for multicomponent films prepared by coaxial scanning pulsed laser deposition technique

In conventional pulsed laser deposition(PLD) technique, plume deflection and composition distribution change with the laser incident direction and pulse energy, then causing uneven film thickness and composition distribution for a multicomponent film and eventually leading to low device quality and low rate of final products. We present a novel method based on PLD for depositing large CIGS films with uniform thickness and stoichiometry. By oscillating a mirror placed coaxially with the incident laser beam,the laser's focus is scanned across the rotating target surface. This arrangement maintains a constant reflectance and optical distance, ensuring that a consistent energy density is delivered to the target surface by each laser pulse. Scanning the laser spot across the target suppresses the formation of micro-columns, and thus the plume deflection effect that reduces film uniformity in conventional PLD technique is eliminated.This coaxial scanning PLD method is used to deposit a CIGS film, 500 nm thick, with thickness uniformity exceeding ±3% within a 5 cm diameter, and exhibiting a highly homogeneous elemental distribution.     

Properties of highly oriented spray-deposited fluorine-doped tin oxide thin films on glass substrates of different thickness

Transparent conducting thin films of fluorine-doped tin oxide (FTO) have been deposited onto the preheated glass substrates of different thickness by spray pyrolysis process using SnCl₄·5H₂O and NH₄F precursors. Substrate thickness is varied from 1 to 6 mm. The films are grown using mixed solvent with propane-2-ol as organic solvent and distilled water at optimized substrate temperature of 475 °C. Films of thickness up to 1525 nm are grown by a fine spray of the source solution using compressed air as a carrier gas. The films have been characterized by the techniques such as X-ray diffraction, optical absorption, van der Pauw technique, and Hall effect. The as-deposited films are preferentially oriented along the (2 0 0) plane and are of polycrystalline SnO₂ with a tetragonal crystal structure having the texture coefficient of 6.19 for the films deposited on 4 mm thick substrate. The lattice parameter values remain unchanged with the substrate thickness. The grain size varies between 38 and 48 nm. The films exhibit moderate optical transmission up to 70% at 550 nm. The figure of merit (φ) varies from 1.36×10⁻⁴ to 1.93×10⁻³ Ω⁻¹. The films are heavily doped, therefore degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) of 7.5 Ω is obtained for a typical sample deposited on 4 mm thick substrate. The resistivity (ρ) and carrier concentration (n_D) vary over 8.38×10⁻⁴ to 2.95×10⁻³ Ω cm and 4.03×10²⁰ to 2.69×10²¹ cm⁻³, respectively.     

大口径光学元件薄膜厚度均匀性修正

 研究了2.2 m高真空箱式镀膜机镀膜时的实际膜厚分布情况。对非球面和平面光学元件,分别采用行星夹具和平面公转夹具并利用修正板调节膜厚均匀性。从实验上实现了大口径薄膜均匀性的调节,并获得较为理想的结果。口径在700 mm范围内,对于凹面均匀性可以控制在0.7%以内,平面均匀性在1%以内;口径在1 200 mm范围内凹面元件均匀性可控制在1%以内,平面1 300 mm口径以内窗口均匀性可控制在1%以内。镀制了口径在400~1 300 mm的多种天文观测上使用的反射镜、增透膜等,获得了理想的光谱曲线与较好的使用效果。     

大口径光学元件薄膜厚度均匀性修正

研究了2.2 m高真空箱式镀膜机镀膜时的实际膜厚分布情况。对非球面和平面光学元件,分别采用行星夹具和平面公转夹具并利用修正板调节膜厚均匀性。从实验上实现了大口径薄膜均匀性的调节,并获得较为理想的结果。口径在700 mm范围内,对于凹面均匀性可以控制在0.7%以内,平面均匀性在1%以内;口径在1 200 mm范围内凹面元件均匀性可控制在1%以内,平面1 300 mm口径以内窗口均匀性可控制在1%以内。镀制了口径在400~1 300 mm的多种天文观测上使用的反射镜、增透膜等,获得了理想的光谱曲线与较好的使用效果。     

Influence of various thickness metallic interlayers on opto-electric and mechanical properties of AZO thin films on PET substrates

Various thickness metallic interlayers to improve the opto-electric and mechanical properties of aluminum-doped zinc oxide (AZO) thin films deposited on flexible polyethylene terephtalate (PET) substrates are studied. The effects of the interlayers on the resistance and transmittance of the AZO thin films are discussed. The result shows that the metallic interlayers effectively improve the electric resistance but reduce the optical transmittance of the AZO thin films. These phenomena become more obvious as the interlayer thickness increases. However, the AZO with an aluminum interlayer still behaves an acceptable transmittance. Moreover, mechanical tests indicate that the aluminum interlayer increases the hardness and modulus, and reduce the residual stress of the AZO thin films. In contrast, the silver and copper interlayers decrease the AZO's mechanical properties. Comparing to those without any interlayer, the results show that the best interlayer is the 6 nm thick aluminum film.     

Formation and thickness evolution of periodic twin domains in manganite films grown on SrTiO3(001) substrates

We present an extended synchrotron x-ray scattering study of the structure of thin manganite films grown on SrTiO3(001) substrates and reveal a new kind of misfit strain relaxation process which exploits twinning to adjust lattice mismatch. We show that this relaxation mechanism emerges in thin films as one-dimensional twinning waves which freeze out into a twin domain pattern as the manganite film continues to grow. A quantitative microscopic model which uses a matrix formalism is able to reproduce all x-ray features and provides a detailed insight into this novel relaxation mechanism. We further demonstrate how this twin angle pattern affects the transport properties in these functional films.     

A new method for the determination of the thickness and the refractive index of thin dielectric films evaporated on metal substrates

A new ellipsometrical method for the accurate determination of the thickness and the refractive index and hence the dispersion for thin transparent films evaporated on metal substrates is put forward. Results for zinc sulphide thin films evaporated in vacuum, 10⁻⁵ mm Hg, on antimony are reported.     

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.     

靶丸壳层厚度及其分布的白光反射光谱测量技术

为了精密检测靶丸壳层厚度及其分布数据,开展了靶丸壳层厚度及其分布的白光反射光谱测量技术研究。介绍了靶丸壳层的白光反射光谱及其光谱数据处理方法（极值法、峰值拟合法、干涉级次校正法等）的基本原理,搭建了基于白光反射光谱的精密回转轴系测量装置;开展了GDP靶丸壳层厚度及其分布的白光反射光谱测量、数据处理和可靠性验证实验,获得了靶丸壳层厚度圆周分布曲线。结果表明,基于峰值拟合法和干涉级次校正的白光反射光谱技术可实现靶丸壳层厚度及其分布的准确测量,其测量误差小于0.1 μm。     

不同类型蒸发源对平面夹具薄膜均匀性的影响

 分析了几种可能的实际蒸发源与薄膜均匀性的关系,其中包括扩展的平面蒸发源和曲面蒸发源。通过实验论证了薄膜均匀性对蒸发源尺寸和蒸发特性的依赖关系。得到的分析结果表明：当蒸发源半径和夹具高度的比值小于1/17时,蒸发源可以被视为一个点面源;大于 1/10时,应当把蒸发源视为面面源进行考虑。当挖坑深度和蒸发源半径的比值介于0和0.5之间时,挖坑对薄膜均匀性造成的影响基本可以忽略;大于0.6时,挖坑效应明显影响薄膜的均匀性。     

Oscillating cracks in glassy films on silicon substrates

Cracks that propagate with near-perfect sinusoidal form are reported in amorphous silicon-rich silica films deposited onto (001) silicon substrates by plasma-enhanced chemical vapour deposition and subjected to thermal annealing. The cracks are shown to result from high tensile stresses that develop in the film during thermal annealing at temperatures in the range up to 700°C, a process shown to be correlated with the loss of hydrogen from the films. Two distinct modes of crack propagation are reported: straight cracks that propagate along directions parallel to [100] cube-edge directions in the substrate, and oscillating cracks that propagate with sinusoidal form parallel to [110] diagonal directions. Sections through the cracks show that the oscillating cracks have a complex three-dimensional structure that extends through the glassy film and into the underlying silicon substrate. This involves a correlated oscillation between the crystallographic orientation of the crack in the surface plane and that of the crack extension into the substrate. Whereas a complete theoretical treatment of this behaviour would be extremely complicated, a simple theory is developed to demonstrate that an oscillating crack has a minimum energy per unit length for a particular wavelength and amplitude that depends upon the physical parameters of both film and substrate. The energy at this minimum is shown to be lower than that of a straight crack for certain parameter ranges so that the oscillating geometry is preferred.     

光学膜层激光损伤阈值均匀性的实验研究

 镀制了多种氧化物介质薄膜。用R-on-1方法测定了膜层的激光损伤阈值。引入数据处理方法，对测试数据进行分析。结果表明，基片清洗后，若放置一段时间再镀膜，则会影响到镀膜后膜层损伤阈值的均匀性，但对损伤阈值自身大小没有影响。测试激光参数对阈值均匀性也有一定影响。     

改性剂对旋转法SiO2减反膜均匀性的影响

分析了采用旋转涂膜法制备溶胶-凝胶SiO2减反膜过程中条纹缺陷产生的机理,利用含氟醇类试剂对减反膜溶胶进行改性,使溶胶链段柔顺性及流动性得到改善。在光学显微镜下对改性前后的膜层进行了对比和分析,对膜层的表面形貌、表面粗糙度以及透射比等特性进行了表征。结果表明:溶胶改性之后的膜层未出现条纹缺陷,表面粗糙度均方根值从4.55 nm下降到小于1.00 nm,膜层表面质量有了较大提高;改性前后膜层的增透性能相当,在熔石英基片上制备的膜层峰值透射比为99.60%~99.89%,膜层激光损伤阈值为21.0~25.3 J/cm2。     

Effects of rotation on Landau states of electrons on a spherical shell

Based on a previously observed analogy between electromagnetic and non-inertial effects, we investigate the competition between magnetic field and rotation in the quantum motion of an electron constrained to the surface of a sphere. We solve numerically the Schrödinger equation of the problem for the energy eigenvalues and the eigenfunctions and compare the effects of the magnetic field and rotation. We obtain that, for a weak magnetic field, an electron can not distinguish between magnetic field and rotation, since they lead to equivalent behavior. But this is no longer true for strong magnetic fields. However, surprisingly, even though the rotation and magnetic fields play different roles in the electronic properties of the system, when together, each influence of the magnetic field on the energy levels can be separately balanced by rotation. We also show that no matter the intensity of the magnetic field, it is always possible to destroy the Landau levels in the sphere by rotation.