Spectroscopic ellipsometry study of non-hydrogenated fully amorphous silicon films deposited by room-temperature radio-frequency magnetron sputtering on glass: Influence of the argon pressure

Márquez, E.; Blanco, E.; Vázquez, Concepción García; Diaz, Jose Mario A.; Saugar, Elías

doi:10.1016/j.jnoncrysol.2020.120305

Cited by 14 publications

(14 citation statements)

References 36 publications

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“…Our computed TLUC parameters are consistent with those reported by some of the authors of this paper, in a previous work concerning with the study of a-Si semiconducting material, by the VASE technique [34]. Moreover, they are also comparable with the best-fit values of the TL-parameters, calculated from the evaporated amorphous silicon (e-a-Si) data compiled in the Palik's Handbook of Optical Properties [35], by Jellison and Modine [29].…”

Section: Data Referencesupporting

confidence: 91%

“…Note that the broad peak of the imaginary part of the dielectric function, 2 , whose highest value, 2,max , is associated with the splitting of bonding and antibonding electron states, and it is located at an energy position, E( 2,max ), of nearly 3.71 eV (see Table 2), almost coincident with the calculated value of the TLUC parameter E 0 . This single smeared peak of 2 is usually shown by tetrahedrally bonded amorphous semiconductors [34], like the cases of elemental Si and Ge.…”

Section: Absorption Edge and Dielectric Function Of Rfms-a-simentioning

confidence: 89%

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Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

et al. 2021

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Several, nearly-1-µm-thick, pure, unhydrogenated amorphous-silicon (a-Si) thin layers were grown at high rates by non-equilibrium rf-magnetron Ar-plasma sputtering (RFMS) onto room-temperature low-cost glass substrates. A new approach is employed for the optical characterization of the thin-layer samples, which is based on some new formulae for the normal-incidence transmission of such a samples and on the adoption of the inverse-synthesis method, by using a devised Matlab GUI environment. The so-far existing limiting value of the thickness-non-uniformity parameter, Δd, when optically characterizing wedge-shaped layers, has been suppressed with the introduction of the appropriate corrections in the expression of transmittance. The optical responses of the H-free RFMS-a-Si thin films investigated, were successfully parameterized using a single, Kramers–Krönig (KK)-consistent, Tauc–Lorentz oscillator model, with the inclusion in the model of the Urbach tail (TLUC), in the present case of non-hydrogenated a-Si films. We have also employed the Wemple–DiDomenico (WDD) single-oscillator model to calculate the two WDD dispersion parameters, dispersion energy, Ed, and oscillator energy, Eso. The amorphous-to-crystalline mass-density ratio in the expression for Ed suggested by Wemple and DiDomenico is the key factor in understanding the refractive index behavior of the a-Si layers under study. The value of the porosity for the specific rf-magnetron sputtering deposition conditions employed in this work, with an Ar-pressure of ~4.4 Pa, is found to be approximately 21%. Additionally, it must be concluded that the adopted TLUC parameterization is highly accurate for the evaluation of the UV/visible/NIR transmittance measurements, on the H-free a-Si investigated. Finally, the performed experiments are needed to have more confidence of quick and accurate optical-characterizations techniques, in order to find new applications of a-Si layers in optics and optoelectronics.

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Section: Data Referencesupporting

confidence: 91%

Section: Absorption Edge and Dielectric Function Of Rfms-a-simentioning

confidence: 89%

Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

et al. 2021

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“…The much more preferred upper film thickness limit for most visible-to-near infrared is well below 5 µm. Even for films that are 1 µm up to well under 5 µm thick, it is best measure with multiple angles of incidence to be able to gain the necessary confidence that you have a unique film thickness solution [14]. However, with the novel approach proposed in the present work we have been able to accurately films thicker than up to 5 µm, having a notable lack of thickness uniformity, and using the normal-incidence transmission spectrum only.…”

Section: Introductionmentioning

confidence: 94%

“…Thin films of amorphous semiconductor materials have been very widely employed in all types of electronic devices, as integrated-microelectronic and optoelectronic devices, acousto-optic devices, optical fabrication of micro-lenses in chalcogenide glasses, optical phase-change materials for chalcogenide thin-film transistors and electronic memories, materials exhibiting reversible and irreversible photo-induced refractive-index changes, photovoltaic solar cells, and, very recently, in the area of chalcogenide photonics, among other important technological applications (see the following, quite ample set of illustrative references, covering all the aforementioned technological applications, [1][2][3][4][5][6][7][8][9][10][11][12][13][14]). Consequently, the optical characterization of such thin non-crystalline semiconducting films deposited onto thick transparent substrates, has been widely performed during the last decades [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Optical Transmittance for Strongly-Wedge-Shaped Semiconductor Films: Appearance of Envelope-Crossover Points in Amorphous As-Based Chalcogenide Materials

Ruiz-Pérez

Navarro

2020

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In this work, we study the influence of the geometry of a thin film on its transmission spectrum, as measured on amorphous As-based chalcogenide layers grown onto 1-mm-thick soda-lime-silica glass substrates. A new method is suggested for a comprehensive optical characterization of the film-on-substrate specimen, which is based upon some novel formulae for the normal-incidence transmittance of such a specimen. It has to be emphasized that they are not limited to the usual cases, where the refractive index, n, of the film and that of the thick transparent substrate, s, must obey: n2>>k2 and s2>>k2, respectively, where k stands for the extinction coefficient of the semiconductor. New expressions for the top and bottom envelopes of the transmission spectrum are also obtained. The geometry limitation usually found when characterizing strongly-wedge-shaped films, has been eliminated with the introduction of an appropriate parameter into the corresponding equations. The presence of crossover points in the top and bottom envelopes of the transmission spectrum, for these strongly-wedge-shaped chalcogenide samples, has been both theoretically predicted and experimentally confirmed.

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“…This difference could be attributed to a change in the film structure, i.e., a possible ordered structure embedded in an amorphous matrix. In addition, at high working Ar pressures, the self-shadowing effects due to the lower mean free path due to the greater number of collisions produced in the plasma during the deposition, were more evident [ 29 ]. This would lead to the formation of more porous films, as demonstrated the lower value of the refractive index of the sample A3, of 3.17 in comparison to that calculated for samples A1 and A2.…”

Section: Resultsmentioning

confidence: 99%

Sputtered Non-Hydrogenated Amorphous Silicon as Alternative Absorber for Silicon Photovoltaic Technology

et al. 2021

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Non-hydrogenated amorphous-silicon films were deposited on glass substrates by Radio Frequency magnetron sputtering with the aim of being used as precursor of a low-cost absorber to replace the conventional silicon absorber in solar cells. Two Serie of samples were deposited varying the substrate temperature and the working gas pressure, ranged from 0.7 to 4.5 Pa. The first Serie was deposited at room temperature, and the second one, at 325 °C. Relatively high deposition rates above 10 Å/s were reached by varying both deposition temperature and working Argon gas pressure to ensure high manufacturing rates. After deposition, the precursor films were treated with a continuous-wave diode laser to achieve a crystallized material considered as the alternative light absorber. Firstly, the structural and optical properties of non-hydrogenated amorphous silicon precursor films were investigated by Raman spectroscopy, atomic force microscopy, X-ray diffraction, reflectance, and transmittance, respectively. Structural changes were observed in the as-deposited films at room temperature, suggesting an orderly structure within an amorphous silicon matrix; meanwhile, the films deposited at higher temperature pointed out an amorphous structure. Lastly, the effect of the precursor material’s deposition conditions, and the laser parameters used in the crystallization process on the quality and properties of the subsequent crystallized material was evaluated. The results showed a strong influence of deposition conditions used in the amorphous silicon precursor.

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Spectroscopic ellipsometry study of non-hydrogenated fully amorphous silicon films deposited by room-temperature radio-frequency magnetron sputtering on glass: Influence of the argon pressure

Cited by 14 publications

References 36 publications

Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

Optical Transmittance for Strongly-Wedge-Shaped Semiconductor Films: Appearance of Envelope-Crossover Points in Amorphous As-Based Chalcogenide Materials

Sputtered Non-Hydrogenated Amorphous Silicon as Alternative Absorber for Silicon Photovoltaic Technology

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