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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

Diagram used to determine bandgap of PbS CBD sample with growth time of 3 h. The value of D corresponds to optical density.
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Figure 2: Diagram used to determine bandgap of PbS CBD sample with growth time of 3 h. The value of D corresponds to optical density.

Mentions: For CBD-made materials obtained after long deposition time (which resulted into dense films with crystallite size of about 20 nm), we observed a blueshift of the fundamental absorption edge relative to the bulk material data [16] in all cases with the following shift values: 0.06 eV for CdS [7], 0.15 eV for CdSe [6] (see also Figure 1), and 0.1 to 0.4 eV for different samples of PbS (Figure 2). This effect was accompanied by reduction of refractive index n (in comparison with bulk crystal data, see Figure 3 for CdSe and Figure 4 for PbS). This reduction is larger for samples obtained with small deposition times, but it is always present in the films discussed here. We connect both effects with pronounced porosity of the films obtained by CBD method. In particular, the blueshift in the dense CBD films is attributed to the quantum confinement in pores.


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)

Diagram used to determine bandgap of PbS CBD sample with growth time of 3 h. The value of D corresponds to optical density.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Diagram used to determine bandgap of PbS CBD sample with growth time of 3 h. The value of D corresponds to optical density.
Mentions: For CBD-made materials obtained after long deposition time (which resulted into dense films with crystallite size of about 20 nm), we observed a blueshift of the fundamental absorption edge relative to the bulk material data [16] in all cases with the following shift values: 0.06 eV for CdS [7], 0.15 eV for CdSe [6] (see also Figure 1), and 0.1 to 0.4 eV for different samples of PbS (Figure 2). This effect was accompanied by reduction of refractive index n (in comparison with bulk crystal data, see Figure 3 for CdSe and Figure 4 for PbS). This reduction is larger for samples obtained with small deposition times, but it is always present in the films discussed here. We connect both effects with pronounced porosity of the films obtained by CBD method. In particular, the blueshift in the dense CBD films is attributed to the quantum confinement in pores.

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