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Efficient visible luminescence of nanocrystalline silicon prepared from amorphous silicon films by thermal annealing and stain etching.

Timoshenko VY, Gonchar KA, Mirgorodskiy IV, Maslova NE, Nikulin VE, Mussabek GK, Taurbaev YT, Svanbayev EA, Taurbaev TI - Nanoscale Res Lett (2011)

Bottom Line: In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature.The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching.The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991, Russia. timoshen@phys.msu.ru.

ABSTRACT
Films of nanocrystalline silicon (nc-Si) were prepared from hydrogenated amorphous silicon (a-Si:H) by using rapid thermal annealing. The formed nc-Si films were subjected to stain etching in hydrofluoric acid solutions in order to passivate surfaces of nc-Si. The optical reflectance spectroscopy revealed the nc-Si formation as well as the high optical quality of the formed films. The Raman scattering spectroscopy was used to estimate the mean size and volume fraction of nc-Si in the annealed films, which were about 4 to 8 nm and 44 to 90%, respectively, depending on the annealing regime. In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature. The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching. The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics.

No MeSH data available.


Reflection spectra of a-Si:H film (solid line), sample #2 after SE (squares), and c-Si wafer (dotted line), for comparison.
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Figure 2: Reflection spectra of a-Si:H film (solid line), sample #2 after SE (squares), and c-Si wafer (dotted line), for comparison.

Mentions: The reflection spectra of the prepared nc-Si films (see Figure 2) reveal two reflection bands at 274 and 368 nm, which are well known for c-Si and can be explained by the optical transitions near the direct band gap [2]. The interference patterns in the VIS-NIR ranges indicate the high optical quality of the films. The refractive indices of the films after RTA evaluated from the interference pattern can be explained by contributions of both amorphous and crystalline phases of Si. Note the quantitative analysis of the data is complicated because of unknown partial volume of pores formed in the films due to the annealing-induced hydrogen evolution. On the one hand, the SE procedure decreases the optical density of the RTA-treated films. This effect is evidently related to an increase of the film porosity because of the chemical dissolution of material. On the other hand, the refraction bands in the UV regions were always observed for the thermally annealed films independently of the duration and type of SE. This fact gives evidence of preferential dissolution of a-Si phase in the annealed samples.


Efficient visible luminescence of nanocrystalline silicon prepared from amorphous silicon films by thermal annealing and stain etching.

Timoshenko VY, Gonchar KA, Mirgorodskiy IV, Maslova NE, Nikulin VE, Mussabek GK, Taurbaev YT, Svanbayev EA, Taurbaev TI - Nanoscale Res Lett (2011)

Reflection spectra of a-Si:H film (solid line), sample #2 after SE (squares), and c-Si wafer (dotted line), for comparison.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211438&req=5

Figure 2: Reflection spectra of a-Si:H film (solid line), sample #2 after SE (squares), and c-Si wafer (dotted line), for comparison.
Mentions: The reflection spectra of the prepared nc-Si films (see Figure 2) reveal two reflection bands at 274 and 368 nm, which are well known for c-Si and can be explained by the optical transitions near the direct band gap [2]. The interference patterns in the VIS-NIR ranges indicate the high optical quality of the films. The refractive indices of the films after RTA evaluated from the interference pattern can be explained by contributions of both amorphous and crystalline phases of Si. Note the quantitative analysis of the data is complicated because of unknown partial volume of pores formed in the films due to the annealing-induced hydrogen evolution. On the one hand, the SE procedure decreases the optical density of the RTA-treated films. This effect is evidently related to an increase of the film porosity because of the chemical dissolution of material. On the other hand, the refraction bands in the UV regions were always observed for the thermally annealed films independently of the duration and type of SE. This fact gives evidence of preferential dissolution of a-Si phase in the annealed samples.

Bottom Line: In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature.The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching.The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991, Russia. timoshen@phys.msu.ru.

ABSTRACT
Films of nanocrystalline silicon (nc-Si) were prepared from hydrogenated amorphous silicon (a-Si:H) by using rapid thermal annealing. The formed nc-Si films were subjected to stain etching in hydrofluoric acid solutions in order to passivate surfaces of nc-Si. The optical reflectance spectroscopy revealed the nc-Si formation as well as the high optical quality of the formed films. The Raman scattering spectroscopy was used to estimate the mean size and volume fraction of nc-Si in the annealed films, which were about 4 to 8 nm and 44 to 90%, respectively, depending on the annealing regime. In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature. The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching. The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics.

No MeSH data available.