The determination of the refractive index and the thickness of thin films of aluminium oxide on aluminium by the polarimetric method

Formulas for the reflection of light from glass (i. e. a dielectric) coated with a thin non-metallic film are generalized for the case of the reflection of light from a metal coated with a thin non-metallic film, e. g. a film of aluminium oxide on aluminium. It is shown how the refractive index and the thickness of the aluminium oxide film on an aluminium mirror can be determined by measurements in polarized light. In conclusion the results of Drude's classical theory of thin non-metallic films on metallic mirrors are compared with the results obtained by the author on the basis of the interference of light in thin films.     

Dependence of wavDependence of wavefront errors on nonuniformity of thin films

In contrast to uncoated substrate, a nonlinear relationship of phase shift with the thicknesses of the thin film makes the calculation of wavefront aberration complicated. A program is compiled to calculate the wavefront aberration of multilayer thin film produced by thickness nonuniformity. The physical thickness and the optical phase change on reflection are considered. As an example, the wavefront aberration of the all-dielectric mirror is presented in ArF excimer lithography system with a typical thickness distribution. In addition, the wavefront errors of the thin film at wavelengths of 193 and 633 nm are compared in the one-piece and two-piece arrangements. Results show that the phase shift upon reflection of the thin film produced by thickness nonuniformity is very sensitive to the incident angle, wavelength, and polarization.     

Full X-ray pattern analysis of vacuum deposited pentacene thin films

Pentacene thin films with thicknesses ranging from 10 nm to 180 nm are investigated by specular X-ray diffraction in the reflectivity regime and in the wide angular regime. The results of the reflectivity measurements show a clear shift of the 001 reflection of the thin film phase depending on the layer thickness. It is shown that this shift can be explained by the dynamical scattering theory. The wide angular regime measurements show the 00L of the thin film phase. Williams-Hall plots are used to extract information on the crystallite size and mean micro strain of the thin film phase. The crystallite size is in good agreement with the results obtained by the reflectivity measurements. From this it can be concluded that the thin film phase crystallites are extended over the entire film thickness down to the substrate. Additionally an increase of the micro strain with increasing film thickness is observed.     

超重反冲余核时间探测器性能测试

介绍了一种铝制内椭球面反射镜闪烁薄膜探测器,对其探测效率、光收集效率和时间性能的测试. 结果分析表明采用1 μm厚的BC498闪烁薄膜探测器测量实验中超重反冲余核, 探测效率接近100％, 时间分辨好于200 ps, 其性能满足超重反冲余核时间测量的要求. A thin plastic scintillator film detector with an inner ellipsoidal reflection mirror made of aluminum is introduced. Detection efficiency and light collection efficiency of the detector have been investigated. The time resolution of the detector has been also studied. The testing results show that the detection efficiency of BC498 with the thickness of 1 micron to be used in the coming superheavy synthesis experiments is approximately 100%, and the time resolution is better than 200 ps (σ). The performances of the thin plastic scintillator film detector meet the requirements for the time measurement of the superheavy element synthesis.     

玻璃衬底二氧化钒薄膜的宽频带太赫兹波调制特性

针对二氧化钒（VO2）薄膜在可调谐太赫兹功能器件中的应用, 采用磁控溅射法在K9玻璃衬底上制备了VO2薄膜, 并用X射线衍射（XRD）对薄膜的晶相进行表征。利用配备加热装置的太赫兹时域光谱系统（THz-TDS）研究了薄膜样品在变温过程中的THz反射、透射光谱特性及其变化规律。实验结果表明, 随着加热温度的升高, VO2薄膜发生半导体-金属相变并对宽频段THz波产生显著的调制作用。调制深度明显依赖于THz频率, 薄膜样品对THz波反射功率、透射率的幅度调制深度在0.3~0.5 THz范围波动较大;对THz波的透射率在低频处较大, 高频处较小, 调制深度在35%~65%之间变化。该薄膜制备简单, 质量高, 可应用于太赫兹开关和调制器等功能器件。     

Planar quarter wave stacks prepared from chalcogenide Ge-Se and polymer polystyrene thin films

Planar quarter wave stacks based on amorphous chalcogenide Ge-Se alternating with polymer polystyrene (PS) thin films are reported as Bragg reflectors for near-infrared region. Chalcogenide films were prepared using a thermal evaporation (TE) while polymer films were deposited using a spin-coating technique. The film thicknesses, d∼165 nm for Ge₂₅Se₇₅ (n=2.35) and d∼250 nm for polymer film (n=1.53), were calculated to center the reflection band round 1550 nm, whose wavelengths are used in telecommunication. Optical properties of prepared multilayer stacks were determined in the range 400-2200 nm using spectral ellipsometry, optical transmission and reflection measurements. Total reflection for normal incidence of unpolarized light was observed from 1530 to 1740 nm for 8 Ge-Se+7 PS thin film stacks prepared on silicon wafer. In addition to total reflection of light with normal incidence, the omnidirectional total reflection of TE-polarized light from 8 Ge-Se+7 PS thin film stacks was observed. Reflection band maxima shifted with varying incident angles, i.e., 1420-1680 nm for 45° deflection from the normal and 1300-1630 nm for 70° deflection from the normal.     

Wave reflection and transmission from a thin film with one-dimensional disorder

This paper deals with a TE plane wave reflection and transmission from a thin film with one-dimensional disorder by means of the stochastic functional approach. The relative permittivity of the thin film is written by a Gaussian random field in the horizontal direction with infinite extent, and is uniform in the vertical direction with finite thickness. Arandomwavefield is obtained in terms of a Wiener-Hermite expansion representation with approximate expansion coefficients (Wiener kernels) under a small fluctuation case. For a SiC thin film and a glass thin film having one-dimensional disorder with Gaussian correlation or an exponential correlation, numerical examples of the first-order incoherent scattering cross section and the optical theorem are illustrated in the figures. It is then found that ripples and four major peaks appear in angular distributions of the incoherent scattering. Such four peaks may occur in the directions of forward scattering, specular reflection, backscattering and in the symmetrical direction of forward scattering with respect to the normal to surface of the thin film. Physical processes that yield such ripples and peaks are discussed.     

Optical parameters of epitaxial GaN thin film on Si substrate from the reflection spectrum

A method has been proposed for determining the optical properties of a thin film layer on absorbing substrates. The film optical parameters such as thickness, refractive index, absorption coefficient, extinction coefficient and the optical energy gap of an absorbing film are retrieved from the interference fringes of the reflection spectrum at normal incidence. The envelopes of the maxima of the spectrum E_M and of the minima E_m are introduced in analytical forms to find the reflectance amplitudes at the interfaces and approximate values of the thin film refractive index. Then, the interference orders and film thickness are calculated to get accurate values of the needed optical parameters. There are no complex fitting procedures or assumed theoretical refractive index dispersion relations. The method is applied to calculate the optical properties of an epitaxial gallium nitride thin film on a silicon (1 1 1) substrate. Good agreement between our results and the published data are obtained.     

Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

We present and apply a new method to measure directly weak magnetization in thin films. The polarization of a neutron beam channeling through a thin film structure is measured after exiting the structure edge as a microbeam. We have applied the method to a three-layer thin film structure acting as a planar waveguide for polarized neutrons. The middle guiding layer is a rare earth based ferrimagnetic material TbCo₅ with a low magnetization of about 20 mT. We demonstrate that the channeling method is more sensitive than the specular neutron reflection method.     

Infrared spectroscopy of self-assembled monolayer films on silicon

Infrared vibrational spectroscopy in an attenuated total reflection (ATR) geometry has been employed to investigate the presence of organic thin layers on Si-wafer surfaces. The phenomena have been simulated to show there can be a field enhancement with the presented single-reflection ATR (SR-ATR) approach which is substantially larger than for conventional ATR or specular reflection. In SR-ATR, a discontinuity of the field normal to the film contributes a field enhancement in the lower index thin film causing a two order of magnitude increase in sensitivity. SR-ATR was employed to characterize a single monolayer of undecylenic acid self-assembled on Si(1 1 1) and to investigate a two monolayer system obtained by adding a monolayer of bovine serum albumin protein.     

Origin of the large polarization in multiferroic YMnO3 thin films revealed by soft- and hard-X-ray diffraction

We investigated the magnetic structure of an orthorhombic YMnO(3) thin film by resonant soft x-ray and hard x-ray diffraction. We observed a temperature-dependent incommensurate magnetic reflection below 45 K and a commensurate lattice-distortion reflection below 35 K. These results demonstrate that the ground state is composed of coexisting E-type and cycloidal states. Their different ordering temperatures clarify the origin of the large polarization to be caused by the E-type antiferromagnetic states in the orthorhombic YMnO(3) thin film.     

Photoinduced changes in optical properties of Ga-Sb-Ge-Se glasses

The kinetics of photoinduced effects on Ga₅Sb₁₀Ge₂₅Se₆₀ thin film exposed to continuous wave laser radiations are studied as a function of exposure time and laser intensity. The transmission and reflection spectra of thin films before and after exposure are investigated. The optical band gap and the refractive index are derived from the above spectra. Generalized Miller's rule and linear refractive index are used to find the nonlinear susceptibility and nonlinear refractive index of the thin films. The studies show a red shift in the band gap with increase in exposure time and laser power which is attributed to the photoinduced darkening in the films.     

Reflection interferometer based on the Troitsky thin film for frequency selection in fiber lasers

A two-mirror multiple-beam interferometer with a noninverted response function in reflection is used for the frequency selection and tuning in fiber lasers. The simplest version of the interferometer is based on a thin metal (Troitsky) film. Such a reflection interferometer corresponds to an external (with respect to a fiber) two-mirror cavity that consists of a spherical highly reflective (99.8%) mirror and a plane mirror represented by the thin metal film deposited on the fiber end face. Tuning to the selected frequency is performed due to a variation in the distance between the mirrors.     

Splitting of an electromagnetic pulse on resonant reflection from a plasma film

It is found theoretically that the temporal profile of a quasimonochromatic electromagnetic pulse is strongly distorted on reflection from a thin (on the wavelength scale) film of a plasma-like (semiconductor, metallic) medium under plasma-resonance conditions. It is shown that an incident Gaussian pulse splits with time (completely or partially) into two reflected pulses, whose amplitudes can be controlled by varying the relationships among the parameters of the incident pulse and the film. Zh. Tekh. Fiz. 67, 65–68 (June 1997)     

On the reflection and transmission of light through thin transparent films

A formula is deduced for the reflection and transmission of light through one thin film. The direction of the passing rays of light (right and left) is taken into account whereby a formula is obtained which is more general than that usually used. The former was used as the starting point for the deduction of formulae for the reflection and transmission of light through two and more thin films which were published by the author some years ago. An explanation is given of the complication of the formulae when the reflection of light from the upper film, adjacent to the air, is computed. The auxiliary phase deduced by the author in a previous paper is also explained as a necessary consequence.     

Magnon scattering by a symmetric atomic well in free standing very thin magnetic films

A theoretical model is presented for the study of the scattering of magnons at an extended symmetric atomic well in very thin magnetic films. The thin film consists of three cubic atomic planes with ordered spins coupled by Heisenberg exchange, and the system is supported on a non-magnetic substrate, and considered otherwise free from magnetic interactions. The coherent transmission and reflection scattering coefficients are derived as elements of a Landauer type scattering matrix. Transmission and reflection scattering cross sections are hence calculated specifically, as a function of the varying local magnetic exchange on the inhomogeneous boundary. Detailed numerical results for the individual incident film magnons, and for the calculated overall magnon conductance, show characteristic transmission properties, with associated Fano resonances, depending on the magnetic boundary conditions and on the magnon incidence.     

Fast and Ultrafast Energy-Dispersive X-Ray Reflectrometry Based on Prism Optics

Interference spectra of X-ray reflection from thin films have been obtained for the first time by the decomposition of the spectrum of a polychromatic beam by means of a diamond prism. The measurements of film nanostructures and reference absorption spectra have been performed at the ESRF synchrotron. The proposed spectrometric scheme allows obtaining the interference pattern in a wide range of the scattering vector length q without angular scanning. This makes it possible to study ultrafast processes in layered nanostructures at an intense external action of laser pulses or charged particles with a time resolution of about the duration of an X-ray pulse.     

Oxidation behavior with quantum dots formation from amorphous GaAs thin films

ABSTRACT

We investigated the oxidation behaviour of an amorphous GaAs thin film deposited onto a micro/nanotextured Si surface by an electron beam. After the deposited film was exposed to air, microcrystallites were formed with octahedral cubic and monoclinic structures of arsenic oxides. Short time exposure after thin film deposition showed the formation of cubic arsenolite while long time exposure showed the formation of monoclinic claudetites as well as cubic arsenolites. These oxide microcrystallites at the GaAs thin film surface disappeared after the sample annealing process. However, the amorphous GaAs thin film included high-density GaAs nanodots. From UV and inverse photoemission spectroscopies, the thin film showed n-type band structure with an energy gap of 2.73?eV. Photoluminescence measurement showed an emission peak at (450–513)?nm with the energy of (2.41–2.75)?eV corresponding to dot size of (4.1–4.5)?nm.     

New interferometric method for determining the refractive index of thin dielectric film,its thickness,the phase shift,and the order of interference

A new interferometric method is proposed, using white light fringes of equal chromatic order to determine simultaneously the following paramcters:

1. The refractive index of a thin dielectric film, and hence its dispersion.
2. The film thickness.
3. The correct value of the order of interference.
4. The phase shift occuring due to reflection at the dielectric/metal interface. In the present work, doubly silvered zinc sulphide (ZnS) thin dielectric film was used as an example in applying the proposed method.

     

嵌入式薄片模型在时域有限差分算法中的应用

将一等效薄片模型嵌入到时域有限差分算法（FDTD）中,以快速而有效地解决复合材料薄片在电磁计算中的多尺度问题。在该嵌入式薄片模型中,薄片不需要被剖分网格,而是被嵌入到相邻的网格间,从而可以使用相对较大的网格剖分周围物体,进而可节省大量的计算资源。在这一模型中,薄片被等效为一段传输线,并用其频域的导纳矩阵代替。使用数字滤波器理论以及逆Z变换可将频域的导纳矩阵转换到时域,并将其嵌入到时域有限差分算法中。该嵌入式薄片模型被用来计算一单层碳纤维复合材料薄片的反射以及透射性能,并与其解析解进行对比,从而验证该模型的准确性、收敛性以及高效性。该模型被用来计算三种具有不同电参数的单层碳纤维复合材料薄片的屏蔽性能,以研究各电参数对其屏蔽性能的影响。