通过脉冲腐蚀形成的多孔硅薄膜的径向微结构和光学特性研究

使用反射光谱、光致发光光谱和SEM研究了通过脉冲腐蚀形成的多孔硅薄膜的径向折射率、光学和物理厚度。详细分析了沿径向方向多孔硅薄膜的径向折射率(n)和光学厚度(nd)与腐蚀中心之间的关系。实验结果表明：随着远离腐蚀中心,SEM图像表明：多孔硅样品的物理厚度缓慢变小,在腐蚀边缘,在径向58μm距离里,薄膜的物理厚度从2.48μm减少到1.72μm;此外,径向折射率n增加,即多孔度变小,同时,反射光谱强度显示出干涉振荡减弱,这意味着多孔硅薄膜的均匀性和界面的平整度变坏。光致发光谱的包络线显示蓝移的趋势,显示纳米微粒的尺寸减少。多孔硅微腔被制备用来研究多孔硅膜的径向光学特性,结果证实：在腐蚀中心,多孔硅膜的均匀性比边缘好。     

平面光波回路用均匀折射率厚SiO2膜制备技术研究

通过优化多孔硅氧化工艺制备了高质量的均匀折射率厚SiO2薄膜,该方法具有高效、低成本的显著优点.通过高倍光学显微观察与棱镜耦合仪分析得到多孔硅氧化形成的SiO2膜厚度达到13μm且厚度均匀;折射率为1.444 8;折射率不均匀度小于0.0‰.     

脉冲腐蚀法制备多孔硅及其光学特性研究

Labview软件控制腐蚀条件,用脉冲电化学腐蚀法制备多孔硅薄膜,其表面形貌用原子力显微镜观察并分析。用可见-紫外分光光度仪测量其反射谱,通过计算得出各种制备条件下,多孔硅薄膜的其它光学参数,即有效折射率neff,吸收系数α,有效介电常数的实部εer和虚部εei,消光系数K。研究了入射光波长和孔隙率对这些光学常数的影响。     

脉冲腐蚀法制备多孔硅及其光学特性研究

Labview软件控制腐蚀条件,用脉冲电化学腐蚀法制备多孔硅薄膜,其表面形貌用原子力显微镜观察并分析。用可见-紫外分光光度仪测量其反射谱,通过计算得出各种制备条件下,多孔硅薄膜的其它光学参数,即有效折射率neff,吸收系数α,有效介电常数的实部εer,和虚部εei,消光系数K,研究了入射光波长和孔隙率对这些光学常数的影响。     

倍频分离薄膜中的半波孔抑制研究

经典短波通膜堆(0.5LH0.5L)n会由于薄膜的折射率不均匀性而产生半波孔现象.在进行膜系结构设计时,通常将薄膜假定为均匀折射率材料,当薄膜的光学厚度为1/2中心波长时,薄膜可被视为虚设层.而在实际制备时,薄膜的折射率通常存在一定的不均匀性,薄膜的光学厚度与设计值不符,从而产生半波孔.对薄膜的基本周期结构进行了优化,优化后的膜系结构在半波处的光学导纳不再受折射率不均匀性的影响.在此基础上,设计并制备了倍频分离薄膜,有效消除了半波孔现象,理论和实验光谱曲线具有很好的一致性.     

一维纳米硅光子晶体的制备与优化

采用双槽电化学腐蚀法制备了纳米多孔硅,主要研究了腐蚀时间和腐蚀电流对重掺杂p型(100)硅衬底上制备的多孔硅层有效光学厚度的影响,采用U-4100光谱仪、场发射扫描电子显微镜(FESEM)技术对所制备的多孔硅光子晶体的结构和有效光学厚度进行了分析表征。研究结果表明,通过合理地选择腐蚀时间和腐蚀电流,可以比较精确地制备特定有效光学厚度的多孔硅薄膜,此方法可广泛应用于纳米多孔硅光子晶体的制备中。     

热蒸发紫外LaF3薄膜光学常数的表征

薄膜光学常数的精确测定对于设计和制备多层薄膜具有重要意义。在JGS1型熔融石英基底上,采用热蒸发沉积方法制备了不同厚度的LaF3单层薄膜样品,利用光度法来获取弱吸收薄膜和基底的光学常数,计算得到其在185～450nm范围内折射率n和消光系数k的色散曲线。实验结果表明,当膜层厚度较薄时,LaF3薄膜折射率表现出不均匀性现象。随着薄膜厚度的增加,薄膜折射率不均匀性减小。在求解过程中选用不均匀模型后,拟合结果与实际测试光谱曲线吻合得很好,提高了薄膜光学常数的计算精度。     

微传感器制备中多孔硅牺牲层技术的研究

采用双槽电化学腐蚀法成功的制备了多孔硅,从多孔硅的SEM照片中发现,孔径尺寸小,均匀性好,腐蚀深度大(超过100μm),在极稀的弱碱溶液中就可以得到去除,然后对双槽化学腐蚀法中腐蚀时间及电流对腐蚀速率的影响进行了研究,最后进一步探讨了多孔硅外貌与硅衬底晶向之间的关系。     

直流磁过滤电弧沉积氮化铝薄膜的研究

利用直流电弧技术在硅基片上制备氮化铝薄膜,研究了薄膜的折射率、消光系数、透过率和沉积速率.薄膜的光学折射率、消光系数、厚度通过椭偏法测试并拟合得到;薄膜的透过率谱通过傅里叶变换红外光谱仪测试,薄膜的沉积速率通过厚度的相应时间计算得到;利用柯希模型来拟合测试得到可见区光学常数,外推得到薄膜在整个近红外、中远红外的光学常数.结果表明:薄膜的折射率随工艺参数的不同有较大的变化范围,并且薄膜在较宽的光谱范围内消光系数为零;薄膜的沉积速率达到85 nm-min-1,单面镀制氮化铝薄膜的硅样片的峰值透过滤达到了69.2%.     

离子束溅射参数与Ta2O5薄膜特性的关联性

离子束溅射技术是制备Ta2O5薄膜的重要技术之一。采用正交试验设计方法,系统研究了Ta2O5薄膜的折射率、折射率非均匀性、消光系数、沉积速率和应力与工艺参数（基板温度、离子束压、离子束流和氧气流量）之间的关联性。通过使用分光光度计和椭圆偏振仪测量Ta2O5薄膜透过率光谱和反射椭偏特性,再利用全光谱反演计算的方法获得薄膜的折射率、折射率非均匀性、消光系数和物理厚度。Ta2O5薄膜的应力通过测量基底镀膜前后的表面变形量计算得到。实验结果表明:基板温度是影响Ta2O5薄膜特性的共性关键要素,其他工艺参数的选择与需求的薄膜特性相关。研究结果对于制备不同应用的Ta2O5薄膜制备工艺参数选择具有指导意义。     

Downward uniformity and optical properties of porous silicon layers

Porous silicon (PS) samples were fabricated by pulse current etching using different times. The downward uniformity and optical properties of the PS layers have been investigated using reflectance spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). The relationship between the refractive index and the optical thickness of PS samples and the etching depth has been analyzed in detail. As the etching depth increases, the average refractive index decreases, indicating that the porosity becomes higher, and the formation rate of the optical thickness decreases. Meanwhile, the reflectance spectra exhibit less intense interference oscillations,which mean the uniformity and interface smoothness of the PS layers become worse. In addition, the intensity of PL emission spectra is slightly increased.     

Temperature: a critical parameter affecting the optical properties of porous silicon

The optical properties of porous silicon (PS) samples fabricated by pulse etching in a temperature rangefrom -40 to 50 ℃ have been investigated using reflectance spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). The dependence of the optical parameters, such as the refractive index n and the optical thickness (nd) of PS samples, on the etching temperature has been analyzed in detail. As the etching temperature decreases, n decreases, indicating a higher porosity, and the physical thickness of PS samples also decreases. Meanwhile, the reflectance spectra exhibit a more intense interference band and the interfaces are smoother.In addition, the intensity of the PL emission spectra is dramatically increased.     

温度：影响多孔硅光学特性的一个关键参数

The optical properties of porous silicon（PS） samples fabricated by pulse etching in a temperature range from-40 to 50-C have been investigated using reflectance spectroscopy,photoluminescence spectroscopy,and scanning electron microscopy（SEM）.The dependence of the optical parameters,such as the refractive index n and the optical thickness（nd） of PS samples,on the etching temperature has been analyzed in detail.As the etching temperature decreases,n decreases,indicating a higher porosity,and the physical thickness of PS samples also decreases.Meanwhile,the reflectance spectra exhibit a more intense interference band and the interfaces are smoother.In addition,the intensity of the PL emission spectra is dramatically increased.     

Radial microstructure and optical properties of a porous silicon layer by pulse anodic etching

This paper investigates the radial refractive index and optical and physical thicknesses of porous silicon (PS) layers prepared by pulse etching by means of reflectance spectroscopy,photoluminescence spectroscopy and scanning electron microscopy(SEM).The relationship between the radial refractive index and optical thickness of the PS sample and the position away from the etched centre along the radial direction has been analyzed in detail. With the position farther away from the etched centre,the SEM image shows that the physical thickness of the PS sample decreases slowly,whereas intensely decreases from 2.48 to 1.72μm near the edge at a distance of 58μm.Moreover,the radial refractive index increases,indicating that the porosity becomes smaller.Meanwhile,the reflectance spectra exhibit the less intense interference oscillations,which mean that the uniformity and interface smoothness of the PS layers become worse,and the envelope curves of photoluminescence spectra exhibit a trend of blue-shift,indicating a reduction in nanocrystal dimensions.The PS micro-cavity is prepared to study the radial optical properties of the PS layer,and the results verify that the uniformity and smoothness of the PS layer in the centre are better than those at the edge.     

Porous silicon multilayer stacks for optical biosensing applications

Porous silicon (PS) multilayer stacks were developed for their use as interference filters in the visible range. The optical behavior of these structures was previously simulated by the use of a computational program, from which the optical constants and thickness of the individual PS layers were determined. The possibility of using these structures as biosensors has been explored, based on the significant changes in the reflectance spectra before and after exposing the PS multilayer to proteins (antibodies). In particular, it is shown that there is a notably reduction of reflectance from PS structures when this material is exposed to polyclonal mouse antibodies. Thus, the experimental results open the possibility of developing biosensors based on the variation of the shape and/or position of the optical or photoluminescent spectrum from PS.     

Characterization of the structure and optical properties of micron porous layers on antimony-doped silicon substrates

A real structure and optical properties of micron porous silicon layers on Si(111) (Sb) substrates were studied by the two-crystal X-ray diffractometry and reflectometry, scanning electron microscopy, and infrared spectroscopy methods in a 4000- to 12000-cm^?1 frequency range. The porous silicon layers were formed by the electrochemical etching method at a 50-mA/cm² current in a hydrofluoric acid/ethanol mixture in a ratio of 1: 1. The structural parameters of the layers are determined, namely, the thickness is 6?C66 ??m, the average deformation is ??4.5 × 10^?4, and the density is ??0.72. It is shown that the studied porous layers can be considered uniform only to some extent. The optical transmission spectra were analyzed within the frameworks of the effective medium model and the refractive index n of the substrate was estimated. It is determined that the Si(111) (Sb) substrates have a pronounced transmission band in the spectral range of 1.05?C1.5 ??m. To restore the dispersion of optical constants from transmission spectra, the procedure, based on the mathematical treatment with regard to real geometric and physical parameters of several transmission spectra by minimizing functional ?? ², was proposed. Possibilities of applying the proposed procedure for determinations of optical characteristics of thin layers and heterostructures are discussed.     

A new algorithm for layer thickness and index step estimation in multi-layer hetero-epitaxial structures

Closed-form mathematical expressions are derived in this work enabling one to obtain both thickness and refractive index steps from the measured optical reflectance of an arbitrary number of layers on a substrate. The theory is based on the assumption that the normalized index steps are small, making this new technique particularly appropriate to the non-destructive analysis of hetero-epitaxial layers. Despite the fact that the derivation is quite involved, experimental data can be analyzed with very modest computer requirements. If the reflectance data is available at equi-spaced wavenumber intervals, each data point is pre-processed by an algebraic transform requiring one addition, one subtraction, and a division, followed by a fast Fourier transform. It is shown theoretically that the Fourier spectrum of the transformed reflectance possesses spectral peaks only at positions corresponding to the interfaces, and in the same sequence as the actual positions of the interfaces in the multilayer structure. The structural determination is therefore totally unambiguous, requiring no time consuming interactive procedures. It is also shown that the relative refractive index steps between adjacent layers may be calculated directly from the amplitude of the discrete Fourier components by direct substitution. The thickness and refractive index estimation technique is demonstrated by both simulated and experimental data on AlGaAs-GaAs structures comprising up to five layers on a substrate. It is demonstrated by these examples that the thickness dynamic range of the method is very wide, ranging in these examples from 1 to 50. The minimum thickness which can be resolved is determined by the frequency resolution of the Fourier transform, which for AlGaAs-GaAs is approximately 150 to 200 nm. However, if this new method is used in conjunction with a curvefit procedure, for the thin layers, it is possible to improve the resolution. Analysis of the simulated data shows that the accuracy in the determination of thickness and refractive index is better than 3% in most instances.     

高性能193nm反射膜的制备与误差分析

分析了膜厚控制误差对反射膜设计曲线的影响,发现高低折射率材料厚度反方向变化时(高折射率膜层厚度增加,低折射率膜层厚度减小),反射膜的反射率变化不明显,设计的膜系结构对这种膜厚变化方式的制造误差宽容.在此基础上制备了193nm反射膜,结果表明退火前光学损耗相对较大,实验结果与理论计算结果存在一定差距,并且散射损耗在总的光学损耗中所占比例很小,而吸收损耗占光学损耗的主要部分,起主导作用.退火后光学损耗明显下降,实验结果与理论计算结果更为接近,193nm反射膜的反射率达98%以上.散射损耗增加至接近吸收损耗的水平,不过在总的光学损耗中仍然占比较小的比例.说明当吸收损耗下降到一定程度时,散射损耗所起的作用也是不可忽视的.     

垂直腔面发射激光器DBR结构参数的优化设计

采用光学传递矩阵法 ,研究了生长偏差对分布布拉格反射 (DBR)结构反射特性的影响 ,并探讨了两种DBR结构改进方案。结果表明 ,周期厚度偏差将使DBR反射谱发生较大偏移 ,在相位匹配条件下减小高折射层厚度可以降低DBR吸收损耗、提高反射率 ,反向改变顶层和底层DBR周期厚度可以提高垂直腔面发射激光器边模抑制比     

同步辐射光刻的X射线反射谱表征

采用X射线反射（XRR）谱对同步辐射导致的氧化物薄膜的刻蚀进行了在位测试,结果表明波长为0．154nm的单色X光在室温下可对MgO和Cr2O3产生轻微的刻蚀。与文献中大量报道的同步辐射X射线光刻及烧蚀不同．这是单色X射线光刻的首次报道。尽管刻蚀速率极慢,但利用XRR谱的高分辨率,成功地检测到了膜厚的减薄。