Quantitative depth profile study of polyaniline films by photothermal spectroscopies

In this study, we carried out a quantitative depth profile analysis of the optical properties of slightly and strongly doped polyaniline (PANI) films, using both photoacoustic and photopyroelectric spectroscopies. As the thermal diffusion length varies inversely to chopper modulation frequency, then at high chopping frequencies information about the sample near the surface is obtained, while at low chopping frequencies the data come from deeper within the sample. The objective of this study is to analyze how the polyaniline doping process in acidic media occurs in the polymeric chain using the photothermal techniques. The results showed that polymeric chains of the doped samples are composed of undoped regions, while polymeric chains of slightly doped samples present doped regions to a lesser degree. These conclusions are in accordance with published results in which doped PANI films exhibit a granular conductive regions in a quasi undoped matrix. In addition, the photothermal spectra showed that the doping process of PANI, in which films are dipped in hydrochloric acid solution, is more effective in the external surface of the films. PACS 61.82.Pv; 82.35.Cd; 82.35.Lr     

用共线光热偏转技术测量光学薄膜的微弱吸收

用具有高灵敏的共线光热偏转技术研究SiO_2、ZrO_2、MgF_2、ZnS等单层光学薄膜的吸收特性,测得它们的吸收率.实验结果与激光量热法及横向光热偏转技术符合良好,表明共线光热偏转技术是测量光学薄膜弱吸收的较理想方法.     

Imaging photothermal microscopy for absorption measurements of optical coatings

For absorption measurement of large-aperture optical coatings, a novel method of imaging photothermal microscopy based on image lock-in technique is presented. Detailed theoretical analysis and numerical calculation are made based on the image photothermal technique. The feasibility of this imaging method is proved through the coincidence between the theoretical results of single spot method and multi-channel method. The measuring speed of this imaging method can be increased hundreds of times compared with that of the raster scanning. This technique can expand the applications of photothermal technique.     

Measurement of surface absorption in optical materials by the method of laser photothermal radiometry

The present work is devoted to the development of the method of laser photothermal radiometry with a view to increasing its spatial resolution over the depth of the specimen when surface layers of the substance of thickness about 1 μm or less are to be investigated. As an example, results of an investigation of radiation absorption in the surface layer of a lithium niobate crystal are presented. The absorption index measured at a wavelength of 1.08 μm was ∼0.6 cm⁻¹. “Polyus” Research Institute, 3, Vernadskii Ave., Moscow, 117342, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 82–84, January–February, 1997.     

利用光热偏转技术实施光学薄膜弱吸收的多波长测量

介绍了光热表面形变光束偏转技术用于测量光学薄膜弱吸收的基本原理,简述多波长吸收测量装置的建立和测试过程,最后给出简单的测量实例.     

Study of polycrystalline boron-doped diamond films by Raman spectroscopy and optical absorption spectroscopy

The effect of the degree of doping polycrystalline diamond films by boron on their Raman and absorption spectra has been studied in the visible region (from 200 to 1000 nm). As the boron concentration increases in a polycrystalline diamond film, its Raman spectrum exhibits a number of new specific features caused by the effect of boron atoms on the diamond lattice. The dependences that relate these features to the boron concentration in the films are given. Moreover, the absorption spectra of the films have revealed a peak whose maximum corresponds to photons with an energy near 2 eV.     

Investigation of electronic states of infinite-layer SrFeO2 epitaxial thin films by X-ray photoemission and absorption spectroscopies

We investigated the electronic states of a single-crystal SrFeO₂ epitaxial thin film in the valence-band and conduction-band regions using synchrotron-radiation X-ray photoemission and absorption spectroscopies. Fe 2p–3d resonant photoemission measurements revealed that the Fe 3d states have higher densities of states at binding energies of 3–5 eV and 5–8.5 eV in the valence-band region. The O K-edge X-ray absorption spectrum exhibited three peaks in the Fe 3d-derived conduction band hybridized with O 2p states; these can be assigned to Fe 3d_xy, 3d_xz + 3d_yz, and 3d_x²_–y². In addition, the indirect bandgap value of the SrFeO₂ film was determined to be 1.3 eV by transmission and absorption spectroscopies.     

Noise-driven optical absorption coefficients of impurity doped quantum dots

We make an extensive investigation of linear, third-order nonlinear, and total optical absorption coefficients (ACs) of impurity doped quantum dots (QDs) in presence and absence of noise. The noise invoked in the present study is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field acts as a source of confinement and a static external electric field has been applied. The AC profiles have been studied as a function of incident photon energy when several important parameters such as optical intensity, electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength take on different values. In addition, the role of mode of application of noise (additive/multiplicative) on the AC profiles has also been analyzed meticulously. The AC profiles often consist of a number of interesting observations such as one photon resonance enhancement, shift of AC peak position, variation of AC peak intensity, and bleaching of AC peak. However, presence of noise alters the features of AC profiles and leads to some interesting manifestations. Multiplicative noise brings about more complexity in the AC profiles than its additive counterpart. The observations indeed illuminate several useful aspects in the study of linear and nonlinear optical properties of doped QD systems, specially in presence of noise. The findings are expected to be quite relevant from a technological perspective.     

Quantitative measurements of optical absorption in CVD-grown ZnS with the phase-shift photothermal method

A technique of measuring weak bulk optical absorption at a wavelength of 10.6 μm in polished plates made of CVD-grown polycrystalline ZnS was developed on the basis of the phase-shift photothermal method. The results obtained are in good agreement with the data on the absorption of the samples under investigation, calculated from calorimetric and transmittance measurements. The possibility of highly sensitive local quantitative measurements of the optical-absorption coefficient using the phase-shift photothermal method is demonstrated.     

Uranium oxides investigated by X-ray absorption and emission spectroscopies

X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO₂, U₃O₈ and UO₃ are presented. The spectral shapes of the O Kα X-ray emission spectra of UO₃ exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO₂ and U₃O₈. This energy dependence is attributed to a significant difference in the oxygen-uranium hybridization between two different sites in the crystal structure of UO₃. The spectral shapes of UO₂ and U₃O₈ are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.     

掺Er/Er+O的GaN薄膜光学性质的研究

利用Raman散射谱研究了GaN注Er以及Er+O共注样品的振动模，并讨论了共注入O对Er离子发光的影响. 在Raman散射谱中，对于注Er的GaN样品出现了300 cm^-1和670 cm^-1两个新的Raman峰，而对于Er+O共注样品，除了上述两个峰外，在360 cm^-1处出现了另外一个新的峰，其中300 cm^-1峰可以用disorder-activated Raman scattering (DARS)来解释，670 cm^-1峰是由于与N空位相关的缺陷引起的，而360 cm^-1峰是由O注入引起的缺陷络合物产生的. 由于360 cm^-1模的缺陷出现，从而导致Er+O共注入GaN薄膜红外光致发光(PL)强度的下降. 关键词： GaN Er Raman散射 光致发光     

Optical absorption and linear/nonlinear parameters of polyvinyl alcohol films doped by fullerene

New polymeric films were developed for optoelectronic devices by an interaction between Fullerene (C60) and polyvinyl alcohol (PVALC) via the casting method. The structure analysis was studied by Gaussian fitting of XRD patterns and SAED (Selected area electron diffraction). Using HRTEM and SEM, the particle shape and the nanocomposite surface on PVALC are investigated. The change in the functional group of the composites was observed via FT-IR and Raman spectroscopy. In this work, we calculated the bandgap and localized state's width, in the forbidden band, via the absorption coefficient obtained from the Beer-Lambert relation. The bandgap of nanocomposite films was reduced to 4.05 eV. Moreover, due to the surface plasmon absorption in nanocomposite films, k (Extinction index) increases with the doping concentration. The bandgap and refractive index (n) relations were studied via various empirical formulas to calculate the average value of n. The linear optical parameters, such as 1^st-order susceptibility (χ⁽¹⁾), high-frequency dielectric (e_∞), and static dielectric (e_o) constants, were calculated. The nonlinear susceptibility χ⁽³⁾ raised from 0.928 × 10⁻¹² esu to 1.779 × 10⁻¹² esu. Also, the refractive index (n₂) enhanced from 1.665 × 10⁻¹¹ esu to 2.993 × 10⁻¹¹ esu. The optical limiting performance and the ability of nanocomposite to absorb laser beams were tested. The result suggests that C60 has a considerable effect on the PVALC matrix, and the samples have the necessary guidance for laser CUT-OFF and photonic applications.     

Potentiality of the photothermal surface-displacement technique for precisely performed absorption measurement of optical coatings

The influence of sample properties on the measured signal has to be investigated, so that measurements of the optical absorption in thin-film coatings by means of the photothermal surface-displacement technique may be precisely performed. Carrying out simultaneously absorption measurements on metal coatings at =10.6 m by using laser calorimetry as well as the surface-displacement technique, the aforementioned influence and the validity of assumptions of the theoretical model, respectively, can be proven. It can be demonstrated that, in contrast to the model, thermophysical coating properties contribute to the probed surface displacement.     

Mn掺杂ZnO薄膜的结构及光学性能研究

通过脉冲激光沉积(PLD)法在SiO₂基片上制备了不同含量的Mn掺杂ZnO薄膜.X射线衍射、X射线能谱、原子力显微镜与紫外-可见分光光度计测试结果表明：少量的Mn离子的掺杂并没有改变薄膜的结构，薄膜具有(103)面的择优取向；PLD法制备的ZnO薄膜的成分与靶材基本一致，实现了薄膜的同组分沉积；薄膜表面比较平坦，起伏度小于80nm，颗粒尺寸主要集中在25nm附近；但是Mn离子的掺杂改变了ZnO薄膜的禁带宽度，随Mn掺杂含量的增加，ZnO薄膜的禁带宽度增加；当薄膜中Mn含量从6%增加到 关键词： PLD ZnO薄膜 Mn掺杂 吸收谱     

Analysis on absolute measurement of optical coating absorption loss based on photothermal detuning technique

Based on the photothermal detuning technique, the three linear relations among reflectance （or trans- mittance）, temperature rise, and pump beam power are studied to achieve the absolute measurement of absorption loss. The relation between temperature and reflectance and the calculation accuracy of tem- perature rise on sample surface have great impacts on the measured result. The influences of parameters involved in the method and the relation between temperature and reflectance and the temperature model of sample surface are also studied. The results show that the absolute absorption loss of optical coatings can be achieved by the proposed method. The measurement accuracy depends on the temperature model and the relation between temperature and reflectance. The linear relation between reflectance and temper- ature rise has largest slope when probe beam wavelength is 632.8 nm and incident angle is 28°. The linear relation slope between temperature rise and pump beam power decreases with the growing of beam size and modulation frequency. The results provide theoretical and experimental supports for the perfection and further application of the photothermal detuning technique.     

X-ray absorption and emission spectroscopic investigation of Mn doped ZnO films

The electronic structure of (Zn,Mn)O films with different Mn concentrations has been investigated by element-selective soft X-ray absorption and emission spectroscopy. The band gap narrowing of (Zn,Mn)O with increase of Mn concentration (<20% Mn) is attributed to the Mn doping and sp-d exchange interactions. According to analysis of the O Kα and resonant Mn L_2,3 X-ray emission spectra, the splitting of Mn 3d subbands is related to Mn-derived states. It indicates that ferromagnetic coupling in (Zn,Mn)O can be taken into account to be carrier-induced. The presence of antiferromagnetism in the heavier Mn-doped films can be explained in terms of the existence of MnO secondary phases.     

纳米CdS-磺化聚苯胺（SPAn）多层复合膜的光学特性研究

研究了利用层-层自组织生长法制备的磺化聚苯胺-CdS纳米晶体复合膜的光学特性.研究发现，随样品中CdS 纳米晶体尺寸的减小，量子尺寸效应明显增强；在紫外吸收谱中表现为吸收边出现了明显蓝移；在光致发光谱中，不仅激子直接复合产生的带边发射产生了蓝移，而且陷阱态复合产生的宽带发射也发生了蓝移.还发现样品经低温退火处理后，激子复合产生的带边发射显著增强，发射带宽随纳米尺寸的减小而变窄.这说明退火后CdS 纳米晶粒的有序性和均匀度显著增加. 关键词： CdS 纳米晶体 SPAn 吸收 发光