Limits...
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.

No MeSH data available.


Related in: MedlinePlus

Plan-view TEM micrograph of Ge NCs embedded in high-k matrix for (a) A-800, (b) A-900, (c) F-800, and (d) F-900 samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211282&req=5

Figure 5: Plan-view TEM micrograph of Ge NCs embedded in high-k matrix for (a) A-800, (b) A-900, (c) F-800, and (d) F-900 samples.

Mentions: Figure 5a, b shows the plane-view TEM images of Ge NCs embedded in Al2O3 and annealed at 800 and 900°C, respectively. The samples are hereafter referred as A-800 and A-900, respectively. The dark patches seen are Ge nanocrystals embedded in amorphous Al2O3 matrix. The nanocrystals are almost spherical and are well dispersed in the host matrix. The estimated size distribution of the nanocrystals for A-800 sample can be approximated by a Gaussian distribution with an average diameter of 7.6 nm. For A-900 sample, the distribution of the nanocrystals throughout the film is not uniform and the diameter varies from 9 to 17 nm. Figure 5c, d shows the plane-view TEM images of Ge NCs embedded in HfO2 and annealed at 800°C (sample F-800) and 900°C (sample F-900), respectively. The image resolution in Figure 5d for F-900 sample is comparatively higher. The average diameter of the Ge NCs for F-800 sample is about 3.9 nm, whereas for F-900 sample it varies from 7 to 13 nm. The change in Gibbs free energy of formation of GeO (111.8 kcal/mol) is much smaller than that of high-k oxides, such as HfO2 (260.1 kcal/mol) and Al2O3 (378.2 kcal/mol) [15], which results in the oxidation of Hf or Al and agglomeration of Ge atoms into nanocrystals in HfO2 or Al2O3 matrix during thermal annealing at high temperatures. It is observed that when annealed at 800°C, which is well below the melting temperature of Ge (938.3°C), only Ge nucleation occurs. Whereas for both 900°C annealed samples (A-900 and F-900), Ge nanocrystals usually show nonuniform distribution of size and density within high-k oxide matrix due to the high diffusion rate of Ge atoms, in consistent with the previously reported results [16]. Furthermore, a higher annealing temperature is expected to result in increased critical nucleus size.


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)

Plan-view TEM micrograph of Ge NCs embedded in high-k matrix for (a) A-800, (b) A-900, (c) F-800, and (d) F-900 samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Plan-view TEM micrograph of Ge NCs embedded in high-k matrix for (a) A-800, (b) A-900, (c) F-800, and (d) F-900 samples.
Mentions: Figure 5a, b shows the plane-view TEM images of Ge NCs embedded in Al2O3 and annealed at 800 and 900°C, respectively. The samples are hereafter referred as A-800 and A-900, respectively. The dark patches seen are Ge nanocrystals embedded in amorphous Al2O3 matrix. The nanocrystals are almost spherical and are well dispersed in the host matrix. The estimated size distribution of the nanocrystals for A-800 sample can be approximated by a Gaussian distribution with an average diameter of 7.6 nm. For A-900 sample, the distribution of the nanocrystals throughout the film is not uniform and the diameter varies from 9 to 17 nm. Figure 5c, d shows the plane-view TEM images of Ge NCs embedded in HfO2 and annealed at 800°C (sample F-800) and 900°C (sample F-900), respectively. The image resolution in Figure 5d for F-900 sample is comparatively higher. The average diameter of the Ge NCs for F-800 sample is about 3.9 nm, whereas for F-900 sample it varies from 7 to 13 nm. The change in Gibbs free energy of formation of GeO (111.8 kcal/mol) is much smaller than that of high-k oxides, such as HfO2 (260.1 kcal/mol) and Al2O3 (378.2 kcal/mol) [15], which results in the oxidation of Hf or Al and agglomeration of Ge atoms into nanocrystals in HfO2 or Al2O3 matrix during thermal annealing at high temperatures. It is observed that when annealed at 800°C, which is well below the melting temperature of Ge (938.3°C), only Ge nucleation occurs. Whereas for both 900°C annealed samples (A-900 and F-900), Ge nanocrystals usually show nonuniform distribution of size and density within high-k oxide matrix due to the high diffusion rate of Ge atoms, in consistent with the previously reported results [16]. Furthermore, a higher annealing temperature is expected to result in increased critical nucleus size.

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