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Low-temperature fabrication of layered self-organized Ge clusters by RF-sputtering.

Pinto SR, Rolo AG, Buljan M, Chahboun A, Bernstorff S, Barradas NP, Alves E, Kashtiban RJ, Bangert U, Gomes MJ - Nanoscale Res Lett (2011)

Bottom Line: In this article, we present an investigation of (Ge + SiO2)/SiO2 multilayers deposited by magnetron sputtering and subsequently annealed at different temperatures.The clusters are ordered in a three-dimensional lattice, and they have very small sizes (about 3 nm) and narrow size distribution.The crystallization of the clusters was achieved at annealing temperature of 700°C.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physics Department, University of Minho, 4710-057 Braga, Portugal. sarapinto@fisica.uminho.pt.

ABSTRACT
In this article, we present an investigation of (Ge + SiO2)/SiO2 multilayers deposited by magnetron sputtering and subsequently annealed at different temperatures. The structural properties were investigated by transmission electron microscopy, grazing incidence small angles X-ray scattering, Rutherford backscattering spectrometry, Raman, and X-ray photoelectron spectroscopies. We show a formation of self-assembled Ge clusters during the deposition at 250°C. The clusters are ordered in a three-dimensional lattice, and they have very small sizes (about 3 nm) and narrow size distribution. The crystallization of the clusters was achieved at annealing temperature of 700°C.

No MeSH data available.


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2D GISAXS maps. 2D GISAXS maps. of (a) as deposited film (b) film annealed at 700°C, and (c) film annealed at 800°C. The second row shows the corresponding simulated GISAXS maps.
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Figure 3: 2D GISAXS maps. 2D GISAXS maps. of (a) as deposited film (b) film annealed at 700°C, and (c) film annealed at 800°C. The second row shows the corresponding simulated GISAXS maps.

Mentions: GISAXS technique was applied to study the clusters' size and their arrangement properties. It gives data from a much larger sample volume compared to the TEM technique. Furthermore, the data are provided in the reciprocal space, so possible spatial correlations would appear as extra diffraction (Bragg) spots, well visible in GISAXS maps. GISAXS maps of the as-deposited and of the annealed multilayers with the corresponding simulations are shown in Figure 3. In the GISAXS map of the as-deposited film, strong Bragg spots are visible. They appear because of the existence of a 3D correlation in the cluster positions [11]. Similar to the 3D clusters reported in [11], the clusters are ordered in a distorted FCC-like lattice defined by primitive vectors a1,2,3. Vectors a1,2 are in the plane parallel to the substrate surface, and they form a distorted 2D hexagonal lattice. The vertical component of a3 equals the multilayer period T. The regular ordering appears in domains which are randomly oriented with respect to the normal to the multilayer surface. As is explained in [11], such regular ordering is a result of interplay of diffusion-mediated nucleation and surface morphology effects. The most important point is that nanoclusters in each new layer nucleate within the minima of the existing surface, while the positions of minima are correlated to the positions of the nanoclusters in the layer underneath. The experimentally measured GISAXS map was fitted to the model described in [11] to obtain the cluster size and arrangement parameters. The results of the analysis give the following parameters for the formed nanoclusters lattice: spacing of clusters within the layers, /a1/ = /a1/ = 6.5 ± 0.2 nm, and the multilayer period T = 6.9 ± 0.1 nm, in agreement with the HRTEM results. The root mean square deviations of the clusters positions from the ideal ones are given by disorder parameters σL and σV describing deviations in directions parallel and perpendicular to the multilayer surface, respectively. These values are also found by GISAXS fit: σL = 3.4 ± 0.2 nm and σV = 0.5 ± 0.1 nm. The size distribution shown in Figure 4 is found to be very narrow for the as-deposited multilayer. Narrowing of the size distribution is a consequence of the regular ordering of the QDs [12].


Low-temperature fabrication of layered self-organized Ge clusters by RF-sputtering.

Pinto SR, Rolo AG, Buljan M, Chahboun A, Bernstorff S, Barradas NP, Alves E, Kashtiban RJ, Bangert U, Gomes MJ - Nanoscale Res Lett (2011)

2D GISAXS maps. 2D GISAXS maps. of (a) as deposited film (b) film annealed at 700°C, and (c) film annealed at 800°C. The second row shows the corresponding simulated GISAXS maps.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211430&req=5

Figure 3: 2D GISAXS maps. 2D GISAXS maps. of (a) as deposited film (b) film annealed at 700°C, and (c) film annealed at 800°C. The second row shows the corresponding simulated GISAXS maps.
Mentions: GISAXS technique was applied to study the clusters' size and their arrangement properties. It gives data from a much larger sample volume compared to the TEM technique. Furthermore, the data are provided in the reciprocal space, so possible spatial correlations would appear as extra diffraction (Bragg) spots, well visible in GISAXS maps. GISAXS maps of the as-deposited and of the annealed multilayers with the corresponding simulations are shown in Figure 3. In the GISAXS map of the as-deposited film, strong Bragg spots are visible. They appear because of the existence of a 3D correlation in the cluster positions [11]. Similar to the 3D clusters reported in [11], the clusters are ordered in a distorted FCC-like lattice defined by primitive vectors a1,2,3. Vectors a1,2 are in the plane parallel to the substrate surface, and they form a distorted 2D hexagonal lattice. The vertical component of a3 equals the multilayer period T. The regular ordering appears in domains which are randomly oriented with respect to the normal to the multilayer surface. As is explained in [11], such regular ordering is a result of interplay of diffusion-mediated nucleation and surface morphology effects. The most important point is that nanoclusters in each new layer nucleate within the minima of the existing surface, while the positions of minima are correlated to the positions of the nanoclusters in the layer underneath. The experimentally measured GISAXS map was fitted to the model described in [11] to obtain the cluster size and arrangement parameters. The results of the analysis give the following parameters for the formed nanoclusters lattice: spacing of clusters within the layers, /a1/ = /a1/ = 6.5 ± 0.2 nm, and the multilayer period T = 6.9 ± 0.1 nm, in agreement with the HRTEM results. The root mean square deviations of the clusters positions from the ideal ones are given by disorder parameters σL and σV describing deviations in directions parallel and perpendicular to the multilayer surface, respectively. These values are also found by GISAXS fit: σL = 3.4 ± 0.2 nm and σV = 0.5 ± 0.1 nm. The size distribution shown in Figure 4 is found to be very narrow for the as-deposited multilayer. Narrowing of the size distribution is a consequence of the regular ordering of the QDs [12].

Bottom Line: In this article, we present an investigation of (Ge + SiO2)/SiO2 multilayers deposited by magnetron sputtering and subsequently annealed at different temperatures.The clusters are ordered in a three-dimensional lattice, and they have very small sizes (about 3 nm) and narrow size distribution.The crystallization of the clusters was achieved at annealing temperature of 700°C.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physics Department, University of Minho, 4710-057 Braga, Portugal. sarapinto@fisica.uminho.pt.

ABSTRACT
In this article, we present an investigation of (Ge + SiO2)/SiO2 multilayers deposited by magnetron sputtering and subsequently annealed at different temperatures. The structural properties were investigated by transmission electron microscopy, grazing incidence small angles X-ray scattering, Rutherford backscattering spectrometry, Raman, and X-ray photoelectron spectroscopies. We show a formation of self-assembled Ge clusters during the deposition at 250°C. The clusters are ordered in a three-dimensional lattice, and they have very small sizes (about 3 nm) and narrow size distribution. The crystallization of the clusters was achieved at annealing temperature of 700°C.

No MeSH data available.


Related in: MedlinePlus