Retrieval of Optical Constants of Undoped Flash-Evaporated Lead Iodide Films from an Analysis of Their Normal Incidence Transmission Spectra Using Swanepoel’s Transmission Envelope Theory of Non-Uniform Films

2021 ◽  
Vol 14 (4) ◽  
pp. 359-378
Keyword(s):  
Refractive Index ◽  
Optical Constants ◽  
Normal Incidence ◽  
Lead Iodide ◽  
Glass Slides ◽  
Envelope Method ◽  
Width Effect ◽  
Film Substrate ◽  
Spectrometer Slit ◽  
A Minor

Abstract: Normal-incidence transmission-wavelength (T_exp (λ)-λ) spectra of 1 and 1.2 m thick flash-evaporated lead iodide (PbI2) films on 1.1 mm thick glass slides held at 200 ℃ display well-spaced several interference-fringe maxima and minima in the λ-range 520-900 nm, without exhibiting a transparent region and with the maxima lying well below the substrate transmission. Below 520 nm, these T_exp (λ)-λ curves drop steeply to zero (at λ ≼ 505 nm), signifying crystalline-like PbI2 film absorption. As corrections of measured (PbI2 film/substrate) transmittance data for substrate absorption and spectrometer slit-width effect were marginal over the studied λ-range, the observed low transmittance of (PbI2 film/substrate) system was related to PbI2 film thickness non-uniformity (∆d), which causes shrinkage of both maxima and minima and leads to significant film optical absorption that reduces both maxima and minima. The McClain ENVELOPE algorithm was utilized, with a minor modification, to construct maxima T_M (λ_max/λ_min) and minima T_m (λ_min/λ_max) envelope curves, which were analyzed by Swanepoel’s envelope method of non-uniform films using an approach that takes account of dispersive substrate refractive index n_s (λ) and circumvents the non-availability of a high-λ transparency region. In such analytical approach, ∆d was varied till a re-generated T_gen (λ)-λ curve matches the T_exp (λ)-λ curve. An average thickness d ̅ of the film, besides its refractive index n(λ) and absorption coefficient α(λ) in the weak, medium and strong absorption regions, were then obtained. The energy-dependence of α(λ) is discussed in view of interband electronic transition models. The obtained results are consistent with other literature studies on similar flash-evaporated PbI2 films. Keywords: PbI2, Optical constants and bandgap, Swanepoel's transmission envelope method, Non-uniform films.

Optical Constants of Annealed a-Si:H from Transmittance at Normal Incidence

2001 ◽  
Vol 692 ◽  
Author(s):  
Atsutoshi Doi ◽  
Yoshiyuki Matsumoto
Keyword(s):  
Refractive Index ◽  
Network Structure ◽  
Optical Constants ◽  
Solid Phase ◽  
Refractive Index Change ◽  
Normal Incidence ◽  
Solid Phase Crystallization ◽  
Index Change ◽  
Temperature Changes ◽  
Interference Fringes

AbstractWe study changes in the optical constants of a-Si:H films caused by the thermal annealing involved in solid phase crystallization. The aim is to examine the growth mechanism, since changes in refractive index are most probably caused by a change in the network structure. The refractive index change was studied from interference fringes in transmitted light at normal incidence, and shows differing dependence on temperature in different thermal ranges. DSC measurement was also performed to examine changes in the network structure with temperature. Changes in optical and thermal properties induced by an increase of temperature reveal frequent network changes of a-Si:H below 470°C and of a-Si in the range 470 to 570°C. We also found crystallization at about 570°C, and grain growth above the crystallization temperature. Knowledge of network changes in a-Si film allows orientation control by an external seed.

Optical Properties of RF-Sputtered a-SiGe:H:O Alloys

1986 ◽  
Vol 77 ◽  
Author(s):  
J. M. T. Pereira ◽  
P. K. Banerjee ◽  
S. S. Mitra
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Optical Constants ◽  
Rf Sputtering ◽  
Normal Incidence ◽  
Reflection And Transmission ◽  
Amorphous Thin Films ◽  
Optical Gap ◽  
Transmission Measurements ◽  
Substrate Temperatures

ABSTRACTAmorphous thin films of SixGe1-x:O (x = 0.70) were prepared by RF-sputtering at several substrate temperatures. The structural properties of these films were studied by IR spectroscopy and revealed features characteristic of hydrogen and/or oxygen bonded to silicon. The optical constants (n,k) were determined from reflection and transmission measurements at near-normal incidence for photon energies in the range of 1 eV and 2.6 eV. The optical gap was derived from the Taue plot and correlated with the composition of the samples. The increase of hydrogen and/or oxygen decreases the value of the refractive index and increases the optical gap.

scholarly journals Determination of Optical Constants and Thickness of Nanostructured ZnO Film by Spin Coating Technique

2021 ◽  
Vol 7 (2) ◽  
pp. 119-125
Author(s):  
R. R. Ghimire ◽  
Y. P. Dahal ◽  
K. B. Rai ◽  
S. P. Gupta
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Spin Coating ◽  
Optical Constants ◽  
Complex Refractive Index ◽  
Visible Region ◽  
Spin Coating Technique ◽  
Transmittance Spectrum ◽  
Coating Technique ◽  
Envelope Method

In this report, we have investigated optical constants and thickness of nanostructured ZnO films grown on a glass substrate by sol-gel spin coating technique using zinc acetate as precursor. Optical constants such as complex refractive index ñ and dielectric constant ϵ determined from the transmittance spectrum in the ultraviolet, visible, near infrared (UV-VIS, NIR) region by envelope method. The value of refractive index decreases from 2.34 to 1.86 and extinction coefficient increases from 0.28 to 0.64 with increasing wavelength. The decreasing behavior of refractive index is attributed due to the increase in transmission and decrease in absorption coefficient with increasing wavelength. The film exhibits reasonably high transmittance (>80%) in the visible region. Absorbance coefficient α and film thickness (d) were calculated from the interference of fringes of transmittance spectrum. The band gap and thickness of the film were found 3.02 eV and 275nm, respectively. The thickness of the film measured by envelope method is validated with cross-section micrograph of SEM images which is about 285 nm. The real part of the dielectric function of nanostructured ZnO decreases with increasing wavelength where as the imaginary part of dielectric constant increases with increasing wavelength. The observed high value of refractive index n and real part of dielectric constant ϵ at lower wavelength is due to band edge absorption of carriers. The dispersion relation shows the increase of complex refractive index and dielectric constant at the high frequency regime is due to the discharging of defect levels using optical excitation of carriers in the visible region.

Envelope Method Applied on the AZO Thin Films

2012 ◽  
Vol 268-270 ◽  
pp. 202-206
Author(s):  
Ying Xu ◽  
Peng Hua Ma ◽  
Mo Ning Liu
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Film Thickness ◽  
Optical Constants ◽  
Light Transmittance ◽  
Incident Wavelength ◽  
Weak Absorption ◽  
Transmittance Spectra ◽  
Glass Substrates ◽  
Envelope Method

The AZO thin films had been prepared on glass substrates by APCVD process .The transmittance spectra of AZO thin films was measured with S-600 UV-Vis spectrophotometer . The visible light transmittance values of AZO thin films are about 85% and the thickness of the thin films well-distributed by the transmittance spectra of AZO films. Using the envelope method, the film thickness d is calculated about 964.43nm and the discrepancy is only 0.56% compared with the result of instrument measurements. The curve about the refractive index n with the incident wavelength is consistent with the reported literature results. The envelope method is suitable for the optical constants processing of some similar AZO films where exist weak absorption ranges (T≥0.4).

Determination of the Optical Constants of Gallium Oxide Films

2014 ◽  
Vol 986-987 ◽  
pp. 42-46
Author(s):  
Chang Long Sun ◽  
Zhen Ping Wu ◽  
Shi Jie Lu ◽  
Zhen Ren ◽  
Yue Hua An ◽  
...  
Keyword(s):  
Thin Film ◽  
Refractive Index ◽  
Transmission Spectrum ◽  
Optical Constants ◽  
Reflectance Spectrum ◽  
Spectrum Measurement ◽  
Dispersion Constant ◽  
Influence Of Substrate ◽  
Film Substrate

Transmission spectrum and reflectance spectrum have long been used to characterize gap semiconductor. Transmission spectrum can be measured very directly, but the influence of substrate absorption is often unavoidable. However, when using the reflectance spectrum measurement, the absorption of thin film, substrate absorption, and coherent interference will make the reflectance spectrum much more complicated. In this paper, Considering the absorption of thin film, substrate absorption, and coherent interference, we use the envelope curves algorithm to achieve the calculation formula of refractive index deduced from the reflectance spectrum. Through the analysis of the reflectance spectrum of Ga2O3film, we achieved thickness of the film, refractive index, extinction and absorption coefficient and dispersion constant.

Retrieval of optical constants of undoped amorphous selenium films from an analysis of their normal-incidence transmittance spectra using numeric PUMA method

2015 ◽  
Vol 27 (4) ◽  
pp. 3281-3291 ◽  
Author(s):  
Mousa M. Abdul-Gader Jafar ◽  
Mahmoud H. Saleh ◽  
Mais Jamil A. Ahmad ◽  
Basim N. Bulos ◽  
Tariq M. Al-Daraghmeh
Keyword(s):  
Optical Constants ◽  
Normal Incidence ◽  
Amorphous Selenium ◽  
Transmittance Spectra ◽  
Selenium Films

Soft X-ray refractive index by reconciling total electron yield with specular reflection: experimental determination of the optical constants of graphite

2018 ◽  
Vol 25 (5) ◽  
pp. 1433-1443
Author(s):  
C. Jansing ◽  
H. Wahab ◽  
H. Timmers ◽  
A. Gaupp ◽  
H.-C. Mertins
Keyword(s):  
Refractive Index ◽  
Optical Constants ◽  
Specular Reflection ◽  
Complex Refractive Index ◽  
Reflection Spectra ◽  
Total Electron Yield ◽  
Total Electron ◽  
X Ray ◽  
Electron Yield ◽  
Saturation Effects

The complex refractive index of many materials is poorly known in the soft X-ray range across absorption edges. This is due to saturation effects that occur there in total-electron-yield and fluorescence-yield spectroscopy and that are strongest at resonance energies. Aiming to obtain reliable optical constants, a procedure that reconciles electron-yield measurements and reflection spectroscopy by correcting these saturation effects is presented. The procedure takes into account the energy- and polarization-dependence of the photon penetration depth as well as the creation efficiency for secondary electrons and their escape length. From corrected electron-yield spectra the absorption constants and the imaginary parts of the refractive index of the material are determined. The real parts of the index are subsequently obtained through a Kramers–Kronig transformation. These preliminary optical constants are refined by simulating reflection spectra and adapting them, so that measured reflection spectra are reproduced best. The efficacy of the new procedure is demonstrated for graphite. The optical constants that have been determined for linearly polarized synchrotron light incident with p- and s-geometry provide a detailed and reliable representation of the complex refractive index of the material near π- and σ-resonances. They are also suitable for allotropes of graphite such as graphene.

scholarly journals Optical constants of sputtered beryllium thin films determined from photoabsorption measurements in the spectral range 20.4–250 eV

2020 ◽  
Vol 27 (1) ◽  
pp. 75-82
Author(s):  
Mikhail Svechnikov ◽  
Nikolay Chkhalo ◽  
Alexey Lopatin ◽  
Roman Pleshkov ◽  
Vladimir Polkovnikov ◽  
...  
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Synchrotron Radiation ◽  
Initial Data ◽  
Absorption Coefficient ◽  
Energy Range ◽  
Transmission Coefficient ◽  
Radiation Source ◽  
Optical Constants ◽  
Free Standing

In this work, the refractive index of beryllium in the photon energy range 20.4–250 eV was experimentally determined. The initial data include measurements of the transmittance of two free-standing Be films with thicknesses of 70 nm and 152 nm, as well as reflectometric measurements of similar films on a substrate. Measurements were carried out at the optics beamline of the BESSY II synchrotron radiation source. The absorption coefficient β was found directly from the transmission coefficient of the films, and the real part of the polarizability δ was calculated from the Kramers–Kronig relations. A comparison is carried out with results obtained 20 years ago at the ALS synchrotron using a similar methodology.

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