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Structural and optical properties of germanium nanostructures on Si(100) and embedded in high-k oxides.

Ray SK, Das S, Singha RK, Manna S, Dhar A - Nanoscale Res Lett (2011)

Bottom Line: The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented.The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented.The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Meteorology, Indian Institute of Technology Kharagpur 721302, India. physkr@phy.iitkgp.ernet.in.

ABSTRACT
The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented. The infrared photoluminescence (PL) signal from Ge islands has been studied at a low temperature. The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented. The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied. Transmission electron micrographs have revealed the formation of isolated spherical Ge nanocrystals in high-k oxide matrix of sizes ranging from 4 to 18 nm. Embedded nanocrystals in high band gap oxides have been found to act as discrete trapping sites for exchanging charge carriers with the conduction channel by direct tunneling that is desired for applications in floating gate memory devices.

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Raman spectra of Ge nanocrystals embedded in (a) Al2O3 and (b) HfO2 matrix in the as-grown and annealed state.
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Figure 6: Raman spectra of Ge nanocrystals embedded in (a) Al2O3 and (b) HfO2 matrix in the as-grown and annealed state.

Mentions: Quantitative structural examinations of Ge nanocrystals have been carried out using Raman spectroscopy. Figure 6a, b shows the Raman spectra of Ge nanocrystals embedded in Al2O3 and HfO2 matrix, respectively, in the as-grown state and after post-growth thermal annealing at 800 and 900 C for 30 min in N2 atmosphere. Raman spectra of nanocrystals are characterized by the size-dependent phonon confinement effects which, for the case of Si and Ge, are manifested by asymmetric line broadening and a red shift of the peak due to breakdown of the k = 0 selection rule for Stokes scattering. The Raman peak at around 300 cm-1 is attributed to the crystalline Ge-Ge phonon vibration mode, indicating the formation of Ge nanocrystals. A blue shift of Raman spectra of silica-embedded [17], sapphire-embedded [18], and Hafnia-embedded [19] Ge NCs has been reported, which has been attributed to the matrix-induced compressive stress on embedded nanocrystals. This blue shift of the peak position with respect to that of the bulk reference spectrum is in disagreement with the prediction of phonon confinement theory. The stress may also arise due to the volumetric expansion of Ge during solidification [17], fast growth rate experienced by nanocrystals as a result of enhanced diffusivity [20] and from the interface energy. The hydrostatic pressure P in the nanocrsytals can be estimated as [21],(3)


Structural and optical properties of germanium nanostructures on Si(100) and embedded in high-k oxides.

Ray SK, Das S, Singha RK, Manna S, Dhar A - Nanoscale Res Lett (2011)

Raman spectra of Ge nanocrystals embedded in (a) Al2O3 and (b) HfO2 matrix in the as-grown and annealed state.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211282&req=5

Figure 6: Raman spectra of Ge nanocrystals embedded in (a) Al2O3 and (b) HfO2 matrix in the as-grown and annealed state.
Mentions: Quantitative structural examinations of Ge nanocrystals have been carried out using Raman spectroscopy. Figure 6a, b shows the Raman spectra of Ge nanocrystals embedded in Al2O3 and HfO2 matrix, respectively, in the as-grown state and after post-growth thermal annealing at 800 and 900 C for 30 min in N2 atmosphere. Raman spectra of nanocrystals are characterized by the size-dependent phonon confinement effects which, for the case of Si and Ge, are manifested by asymmetric line broadening and a red shift of the peak due to breakdown of the k = 0 selection rule for Stokes scattering. The Raman peak at around 300 cm-1 is attributed to the crystalline Ge-Ge phonon vibration mode, indicating the formation of Ge nanocrystals. A blue shift of Raman spectra of silica-embedded [17], sapphire-embedded [18], and Hafnia-embedded [19] Ge NCs has been reported, which has been attributed to the matrix-induced compressive stress on embedded nanocrystals. This blue shift of the peak position with respect to that of the bulk reference spectrum is in disagreement with the prediction of phonon confinement theory. The stress may also arise due to the volumetric expansion of Ge during solidification [17], fast growth rate experienced by nanocrystals as a result of enhanced diffusivity [20] and from the interface energy. The hydrostatic pressure P in the nanocrsytals can be estimated as [21],(3)

Bottom Line: The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented.The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented.The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Meteorology, Indian Institute of Technology Kharagpur 721302, India. physkr@phy.iitkgp.ernet.in.

ABSTRACT
The structural and optical properties of Ge quantum dots (QDs) grown on Si(001) for mid-infrared photodetector and Ge nanocrystals embedded in oxide matrices for floating gate memory devices are presented. The infrared photoluminescence (PL) signal from Ge islands has been studied at a low temperature. The temperature- and bias-dependent photocurrent spectra of a capped Si/SiGe/Si(001) QDs infrared photodetector device are presented. The properties of Ge nanocrystals of different size and density embedded in high-k matrices grown using radio frequency magnetron sputtering have been studied. Transmission electron micrographs have revealed the formation of isolated spherical Ge nanocrystals in high-k oxide matrix of sizes ranging from 4 to 18 nm. Embedded nanocrystals in high band gap oxides have been found to act as discrete trapping sites for exchanging charge carriers with the conduction channel by direct tunneling that is desired for applications in floating gate memory devices.

No MeSH data available.


Related in: MedlinePlus