Optical Properties of Bismuth Telluride Thin Films, Bi2Te3/Si(100) and Bi2Te3/SiO2/Si(100)

Kaddouri, El. H.; Maurice, T.; Gratens, X.; Charar, S.; Bénet, S.; Mefleh, A.; Tedenac, Jean‐Claude; Liautard, B.

doi:10.1002/(sici)1521-396x(199912)176:2<1071::aid-pssa1071>3.0.co;2-e

Cited by 28 publications

(12 citation statements)

References 18 publications

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“…Extinction coefficients and refractive indices are relatively high compared to the data reported by Dheepa [12], due to the optically thick films [27], and increase with wavelength for Se and Fe doped films of 150 nm thickness ( Fig. 8(a)) which is in accord with the literature [12,27,28]. …”

Section: Fig7: Spectral Dependence Of Transmittance (T) and Reflectasupporting

confidence: 89%

Influence of doping on structural and optical properties of Bi2Te3 thin films

2015

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Section: Fig7: Spectral Dependence Of Transmittance (T) and Reflectasupporting

confidence: 89%

Influence of doping on structural and optical properties of Bi2Te3 thin films

2015

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“…Such features have already been observed by Kaddouri et al in reflectance spectra for 3-m samples obtained by hot-wall epitaxy. 21 In Fig. 7 Theoretical predictions do not agree with the experimental literature values obtained from transmission and reflection measurements.…”

Section: Resultsmentioning

confidence: 82%

“…[14][15][16][17][18] More recently, thin films were characterized by classical optical methods. [19][20][21][22] Only one work 20 was reported on thin films obtained by metallorganic chemical vapor deposition using spectroscopic ellipsometry ͑SE͒ in the visible range. Ellipsometry is an optical method for surface analysis based on the measurement of the change of the polarization state of a light beam during reflection.…”

mentioning

confidence: 99%

Infrared and Visible Dielectric Function of Electroplated Bi[sub 2±x]Te[sub 3±x] Films Determined by Spectroscopic Ellipsometry

Zimmer

Stein

Johann

et al. 2005

J. Electrochem. Soc.

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The pseudodielectric functions of electroplated Bi 2±x Te 3±x thin films with atomic bismuth content varying from 1.8 to 2.2 were determined using spectroscopic ellipsometry in the energy range of 0.03-3.10 eV. The experimental dielectric functions show differences with the literature bulk single-crystal data which may be explained by a ca. 50% porosity in the electroplated films. In the visible range, the optical constants did not seem to depend on the film composition while in the infrared range a rough tendency can be established: the real part of the dielectric function shifted to lower values with increasing bismuth content while the imaginary part shifted toward higher values. In the infrared range, Tauc-Lorentz combined with Drude dispersion relations were successfully used. The energy bandgap E g was found to be about 0.11 eV independent of the film composition. This result is related to the minor evolution of the film composition. Moreover, the fundamental absorption edge was described by an indirect optical band-to-band transition. The thickness of the thinner films were estimated, which are comprised between 1.77 and 1.99 m following the samples. Electrical resistivity and energy-independent scattering time were found to be related to the bismuth content.V-VI binary compounds such as Bi 2 Te 3 , Sb 2 Te 3 , and Bi 2 Se 3 are narrow bandgap semiconductors. They are becoming quite interesting as materials for thermoelectric devices. Due to their high figureof-merit at room temperature, bismuth telluride ͑Bi 2 Te 3 ͒ and its selenide and antimony-doped compounds are considered to be the best materials for thermoelectric applications. 1 Many deposition techniques, such as sputtering, 2-4 metallorganic chemical vapor deposition, 5,6 and molecular beam epitaxy, 7-9 have been used to obtain thin films of bismuth telluride compounds. These deposition techniques have as drawback a rather high production cost. Electrodeposition 10-12 may offer a low-cost film growth method with a high deposition rate. Several electrochemical processes have been developed, leading to different compositions of Bi 2 Te 3 binary compounds. 12,13 The stoichiometry of these thermoelectric films directly influences their electronic and transport properties.Due to both experimental interest and theoretical importance, the optical properties of Bi 2 Te 3 were studied using crystals or thin films. The first results were performed on ingots with transmittance and reflectance measurements methods. 14-18 More recently, thin films were characterized by classical optical methods. [19][20][21][22] Only one work 20 was reported on thin films obtained by metallorganic chemical vapor deposition using spectroscopic ellipsometry ͑SE͒ in the visible range. Ellipsometry is an optical method for surface analysis based on the measurement of the change of the polarization state of a light beam during reflection. 23 From ellipsometry, the dielectric function of bulk materials is obtained analytically, while for thin films appropriate fitting is needed. Th...

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“…The IR annealing (0.5 kW IR source: 1500–5600 nm, i.e. 0.2214–0.8266 eV, corresponding to ∼20,000–100,000 cm –1 of absorption coefficient on Bi–Te film , ) was initially conducted in the same condition but with the sample held statically under the IR source to determine the effect of the maximum irradiation temperature. To measure the dynamic temperature on the film surface (i.e.…”

Section: Experimental Detailsmentioning

confidence: 99%

Static and Dynamic Postannealing Strategies for Roll-to-Roll Fabrication of DC Magnetron Sputtered Bismuth Telluride Thin Films onto Polymer Webs

Tao

Stuart

Wan

et al. 2021

ACS Appl. Mater. Interfaces

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High-throughput roll-to-roll processes are desirable to scale up the manufacture of flexible thermoelectric generators. Whilst vacuum deposition onto a heated dynamic substrate presents a considerable engineering challenge, viable post-deposition in-line annealing processes are considered as an alternative to improve the functional performance of as-deposited films. The effect of infrared and electron-beam irradiations of 1-𝜇m thick bismuth telluride thin films, produced by a vacuum roll-to-roll process for use as thermoelectric materials, were examined. Static vacuum oven and pulsed high-energy electron beam were also studied as control groups. All annealing strategies increased the crystallite size, and decreased the Te content. Only the static vacuum oven treatment was shown to significantly improve the film's crystallinity. After 1-hour annealing, the power factor improved by 400% (from 2.8 to 14 × 10 -4 W/mK 2 ), which, to the knowledge of the authors, is the highest reported thermoelectric performance of post-annealed or hot-deposited Bi-Te films. As for inline annealing, infrared and electron-beam post treatments improved the power factor by 146% (from 2.8 to 6.9 × 10 -4 W/mK 2 ) and 64% (from 2.8 to 4.6 × 10 -4 W/mK 2 ), respectively.

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Optical Properties of Bismuth Telluride Thin Films, Bi2Te3/Si(100) and Bi2Te3/SiO2/Si(100)

Cited by 28 publications

References 18 publications

Influence of doping on structural and optical properties of Bi2Te3 thin films

Influence of doping on structural and optical properties of Bi2Te3 thin films

Infrared and Visible Dielectric Function of Electroplated Bi[sub 2±x]Te[sub 3±x] Films Determined by Spectroscopic Ellipsometry

Static and Dynamic Postannealing Strategies for Roll-to-Roll Fabrication of DC Magnetron Sputtered Bismuth Telluride Thin Films onto Polymer Webs

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