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The effects of porosity on optical properties of semiconductor chalcogenide films obtained by the chemical bath deposition.

Vorobiev YV, Horley PP, Hernández-Borja J, Esparza-Ponce HE, Ramírez-Bon R, Vorobiev P, Pérez C, González-Hernández J - Nanoscale Res Lett (2012)

Bottom Line: The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement.Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials.The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: CINVESTAV-IPN Unidad Querétaro, Libramiento Norponiente 2000, Fracc, Real de Juriquilla, Querétaro, Qro, CP 76230, México. vorobiev@qro.cinvestav.mx.

ABSTRACT
This paper is dedicated to study the thin polycrystalline films of semiconductor chalcogenide materials (CdS, CdSe, and PbS) obtained by ammonia-free chemical bath deposition. The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement. Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials. Both effects are attributed to the material porosity which is a typical feature of chemical bath deposition technique. The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction. Quantum mechanical description of the nanopores in semiconductor is given based on the application of even mirror boundary conditions for the solution of the Schrödinger equation; the results of calculations give a reasonable explanation of the experimental data.

No MeSH data available.


Related in: MedlinePlus

Dependence of the grain size of PbS CBD samples on growth time. The line is given as eye guide only.
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Figure 5: Dependence of the grain size of PbS CBD samples on growth time. The line is given as eye guide only.

Mentions: The case of PbS requires more attention. Figure 5 presents the dependence of the crystallite size upon the deposition time. Figure 4 shows the spectra for optical constants (refractive index n and extinction coefficient k) measured for four PbS films deposited with growth time ranging from 1 to 4 h; in the latter case, the result was a 100-nm-thick film. It is clear that for larger deposition time, the film becomes denser so that refraction index and extinction coefficients increase. Their spectral behavior follows qualitatively the corresponding curves of the bulk material, but the values are essentially lower, even when deposited film has a considerable thickness. For example, the refractive index for film is 4 at most for the wavelength 450 nm, whereas for the bulk material, the corresponding value is 4.3. As for extinction coefficient k, the maximum of 2.75 is achieved at the wavelength of 350 nm, with the corresponding bulk value of 3.37.


The effects of porosity on optical properties of semiconductor chalcogenide films obtained by the chemical bath deposition.

Vorobiev YV, Horley PP, Hernández-Borja J, Esparza-Ponce HE, Ramírez-Bon R, Vorobiev P, Pérez C, González-Hernández J - Nanoscale Res Lett (2012)

Dependence of the grain size of PbS CBD samples on growth time. The line is given as eye guide only.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475102&req=5

Figure 5: Dependence of the grain size of PbS CBD samples on growth time. The line is given as eye guide only.
Mentions: The case of PbS requires more attention. Figure 5 presents the dependence of the crystallite size upon the deposition time. Figure 4 shows the spectra for optical constants (refractive index n and extinction coefficient k) measured for four PbS films deposited with growth time ranging from 1 to 4 h; in the latter case, the result was a 100-nm-thick film. It is clear that for larger deposition time, the film becomes denser so that refraction index and extinction coefficients increase. Their spectral behavior follows qualitatively the corresponding curves of the bulk material, but the values are essentially lower, even when deposited film has a considerable thickness. For example, the refractive index for film is 4 at most for the wavelength 450 nm, whereas for the bulk material, the corresponding value is 4.3. As for extinction coefficient k, the maximum of 2.75 is achieved at the wavelength of 350 nm, with the corresponding bulk value of 3.37.

Bottom Line: The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement.Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials.The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: CINVESTAV-IPN Unidad Querétaro, Libramiento Norponiente 2000, Fracc, Real de Juriquilla, Querétaro, Qro, CP 76230, México. vorobiev@qro.cinvestav.mx.

ABSTRACT
This paper is dedicated to study the thin polycrystalline films of semiconductor chalcogenide materials (CdS, CdSe, and PbS) obtained by ammonia-free chemical bath deposition. The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement. Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials. Both effects are attributed to the material porosity which is a typical feature of chemical bath deposition technique. The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction. Quantum mechanical description of the nanopores in semiconductor is given based on the application of even mirror boundary conditions for the solution of the Schrödinger equation; the results of calculations give a reasonable explanation of the experimental data.

No MeSH data available.


Related in: MedlinePlus