Optical constants of absorbing films

Nagendra, C. L.; Thutupalli, G. K. M.

doi:10.1016/0042-207x(81)90004-x

Cited by 26 publications

(9 citation statements)

References 2 publications

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“…(n,k) can be solved for by Newton-Raphson iteration. [5][6][7][8][9] This technique requires an initial (n i ,k i ) value and the expansions of the R and T equations up to first order in (⌬n,⌬k):…”

Section: Determination Of the Optical Properties Of The Gaas:c Fmentioning

confidence: 99%

“…5 This approach, embodied in software ͑OptiCon͒ developed by Tsu,6 combines a graphical technique with Newton-Raphson iteration. 7 At each wavelength, this technique uses the measured (R,T) values to determine (n,k), the refractive index and extinction coefficient. (n,k) then determine the other optical properties, including the optical absorption coefficient ␣.…”

Section: Introductionmentioning

confidence: 99%

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Intervalenceband and plasmon optical absorption in heavily doped GaAs:C

Songprakob

Zallen

Tsu³

et al. 2002

Journal of Applied Physics

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By using direct numerical-solution techniques for the reflectance (R) and transmittance (T) equations of a multilayer structure, we have analyzed infrared R and T measurements on heavily doped p-type GaAs:C films grown by molecular beam epitaxy. The optical properties, for films with hole concentrations up to 1.4ϫ10 20 cm Ϫ3 , were determined for photon energies from 0.07 to 0.6 eV, in which region plasmon ͑intraband͒ and intervalenceband contributions are in competition. Our results for the optical absorption coefficient resolve two separate peaks located ͑at high doping͒ at about 0.1 and 0.2 eV. By carrying out calculations of the intervalenceband ͑IVB͒ absorption processes for our dopings, we identify the peak near 0.2 eV with light-hole to heavy-hole IVB transitions, and we attribute the lower-energy peak to hole-plasmon excitations. Our experimental absorption spectra are very well described by a model combining the IVB contribution to the dielectric function with a plasmon contribution. The hole-plasmon parameters we obtain for highly doped p-GaAs yield an infrared mobility which ͑unlike the too-small IVB-entangled infrared mobility implied by the use of the usual effective-plasmon model͒ is in substantial agreement with the dc mobility.

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Section: Determination Of the Optical Properties Of The Gaas:c Fmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intervalenceband and plasmon optical absorption in heavily doped GaAs:C

Songprakob

Zallen

Tsu³

et al. 2002

Journal of Applied Physics

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“…15 Two methods were used 15 to solve Eqs. ͑1͒ and ͑2͒, one based on a two-dimensional Newton-Raphson ͑NR͒ iteration, 14 and another based on a graphical technique. It was found that the NR method could not always find all the expected solutions.…”

Section: A Obtaining Optical Constants †Nk ‡ or †⑀ј⑀љ ‡mentioning

confidence: 99%

“…In spite of the apparent analytical difficulty, numerical solutions can readily be carried out. [14][15][16] Although we initially applied the numerical technique to obtaining the optical constants pertaining to electronic transitions ͑i.e., over the ultraviolet to near IR spectral range͒ in Ge x Sb y Te z Chalcogenide thin films, 15 the numerical strategies available in the ''OptiCon'' software 16 used for that analysis can also be applied to the analyses of vibrational transitions which occur in the mid to far IR range. This is because the thin film expressions relating ͓R,T͔ to ͓n,k͔ are the same, whether analyzing the UV or the far-IR.…”

Section: Introductionmentioning

confidence: 99%

Infrared optical constants of silicon dioxide thin films by measurements of R and T

Tsu¹

2000

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Optical constants [n,k] of 30–300 nm SiO2 films, thermally grown on c-Si substrates, are obtained numerically from [R,T] data. The calculations are done at each wavelength, no a priori assumptions regarding dispersion relations are needed. The technique also provides the film thickness, whose values agree with ellipsometric measurements. The optical constants are compared to those of bulk fused silica glass (FSG) and are found to differ in subtle but important ways. The principal absorption band due to the Si–O TO stretching vibrations, and measured by the ε″ (imaginary dielectric) band, is slightly greater in magnitude and 12 cm−1 narrower for the film than for the bulk material. We interpret this to indicate a simpler strain field within the film compared to the bulk material. We find, however, that the integrated intensities are identical, indicating similar densities. We show that the shift in peak position of the absorbance band with changes in film thickness is almost entirely an optical thin film effect. The absorbance band’s character gradually changes from resembling the ε″ band for very thin samples (⩽30 nm) to resembling the corresponding [k] band for thicker samples. Although ε″ and [k] are intimately related, their positions and widths differ, thus accounting for the systematic changes in width and position of the absorbance band. Only the 30 nm sample appears to differ in any significant way from thicker samples. This difference is mainly in the low magnitude of ε″ (indicating low density for that sample). There is a modest 2 cm−1 shift in the peak position of ε″.

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“…Ceneration of the 'n' and 'k' data instantaneously, utilising minimal time For exanple, in a majority of the spectrophotcixetric methods [5,8,9], it is seen that there exists unwanted imiltiple solutions, the elimination of which require SPIE Vol. Ceneration of the 'n' and 'k' data instantaneously, utilising minimal time For exanple, in a majority of the spectrophotcixetric methods [5,8,9], it is seen that there exists unwanted imiltiple solutions, the elimination of which require SPIE Vol.…”

Section: Introductfcmmentioning

confidence: 99%

Determination of optical constants of absorbing and nonabsorbing coatings: a computer-aided approach

Rao

Annapurna

Nagendra

et al. 1990

Electro-Optical Materials for Switches, Coatings, Sensor Optics, and Detectors

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A dual stage, closed loop and self scanning algoritFin has been proposed for precise determination of optical constants i.e., refractive index, 'n', and absorption Index, 'k ' , together with thickness ' of thin film coatings . In the first stage , refractive index solutics over a knc.zn range are generated for a given set of nasured paranters , nanely, reflectance , R and trannittance , T, and preset thickness of the coating , where as in the seccd stage a merit function, defined in terms of mean square of the difference between refractive index values at consecutive wavelengths, is miriimised with respect to thickness. It is seen that while the algorithn can estimate the 'n ' , ' and ' d ' to an accuracy better than 0.005, 0.002 and 5/50 A0 (5 A0 for visible region coatings and 50 A0 for infrared coatings ) for an experinntal error of +0 . 005 in R arid T and it is able to overccme the ambiguity of ns.iltiple solutions, inherent in the existing methods.Apart from this, the required data can be generated faster, dispensing the cunbersane and expensive graphic systems. The algoritFin has been successfully appi ied to determine the optical constants of absorbing and transparent films.

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Optical constants of absorbing films

Cited by 26 publications

References 2 publications

Intervalenceband and plasmon optical absorption in heavily doped GaAs:C

Intervalenceband and plasmon optical absorption in heavily doped GaAs:C

Infrared optical constants of silicon dioxide thin films by measurements of R and T

Determination of optical constants of absorbing and nonabsorbing coatings: a computer-aided approach

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