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Nucleation and growth of primary nanostructures in SrTiO3 homoepitaxy.

Phark SH, Chang YJ - Nanoscale Res Lett (2015)

Bottom Line: Second, one-dimensional SrTiO3 islands of a 4 uc width grew along the crystal symmetry directions.These observations suggest that 4 × 4-uc (2) islands act as a minimum nucleation seed, and the addition of SrTiO3 molecular species of the same width is the primary and dominant growth process in SrTiO3 homoepitaxy.A close inspection of the surface of the substrate during the deposition process revealed possible connections between surface reconstruction and energetically favorable nucleation of SrTiO3 islands.

View Article: PubMed Central - PubMed

Affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul National University, Seoul, 151-747 Republic of Korea ; Department of Physics and Astronomy, Seoul National University, Seoul, 151-747 Republic of Korea.

ABSTRACT
SrTiO3 nanoislands on SrTiO3 (001) in a diffusion-limited growth regime were studied using in situ scanning tunneling microscopy (STM). The STM images revealed two characteristic features of nucleation stages. First, the minimum lateral size of the one-unit-cell (uc)-high SrTiO3 islands was 4 × 4 uc (2). Second, one-dimensional SrTiO3 islands of a 4 uc width grew along the crystal symmetry directions. These observations suggest that 4 × 4-uc (2) islands act as a minimum nucleation seed, and the addition of SrTiO3 molecular species of the same width is the primary and dominant growth process in SrTiO3 homoepitaxy. A close inspection of the surface of the substrate during the deposition process revealed possible connections between surface reconstruction and energetically favorable nucleation of SrTiO3 islands.

No MeSH data available.


Related in: MedlinePlus

STM images for a coverage dependence of SrTiO3homoepitaxy. The 50 × 50-nm2 STM images of (a) 0.6-ML, (b) 0.3-ML, and (c) 0.1-ML SrTiO3 films grown on (2 × 1) reconstructed 0.1% Nb-doped SrTiO3 (001) surfaces at Tsub = 580°C. The crystallographic axes are shown by the yellow arrows in (c), and some larger islands are indicated by the dotted yellow circles. All STM images were obtained with VS = 2.5 V and Iset = 50 pA. (d) The height profile along the yellow line in (a).
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Fig1: STM images for a coverage dependence of SrTiO3homoepitaxy. The 50 × 50-nm2 STM images of (a) 0.6-ML, (b) 0.3-ML, and (c) 0.1-ML SrTiO3 films grown on (2 × 1) reconstructed 0.1% Nb-doped SrTiO3 (001) surfaces at Tsub = 580°C. The crystallographic axes are shown by the yellow arrows in (c), and some larger islands are indicated by the dotted yellow circles. All STM images were obtained with VS = 2.5 V and Iset = 50 pA. (d) The height profile along the yellow line in (a).

Mentions: Figure 1 shows STM topographic images for SrTiO3 films that were 0.6-, 0.3-, and 0.1-monolayer (ML) thick grown at Tsub = 580°C. The height profile across the surface reveals that the deposited layer is 1 uc high (i.e., approximately 0.4 nm), as shown in Figure 1d. When the surface coverage was greater than that of a critical coverage of approximately 0.5 ML, coalescence of islands occurred, and the film exhibited relatively homogeneous 2D growth patterns, as shown in Figure 1a, which were maintained until the coverage reached approximately 1 ML (not shown). However, the growth pattern was inhomogeneous in terms of both size and shape when the coverage was less than that required for coalescence (i.e., <0.5 ML), as can be seen for the 0.3-ML film shown in Figure 1b. The STM image of the 0.1-ML sample shown in Figure 1c reveals islands with a spatial extent of a few nanometers, which were less homogeneous with greater anisotropy than those in the 0.3-ML film. Some islands were elongated along the <100 > crystal axes of SrTiO3. Larger islands appear to be produced by 2D aggregation of smaller square formations.Figure 1


Nucleation and growth of primary nanostructures in SrTiO3 homoepitaxy.

Phark SH, Chang YJ - Nanoscale Res Lett (2015)

STM images for a coverage dependence of SrTiO3homoepitaxy. The 50 × 50-nm2 STM images of (a) 0.6-ML, (b) 0.3-ML, and (c) 0.1-ML SrTiO3 films grown on (2 × 1) reconstructed 0.1% Nb-doped SrTiO3 (001) surfaces at Tsub = 580°C. The crystallographic axes are shown by the yellow arrows in (c), and some larger islands are indicated by the dotted yellow circles. All STM images were obtained with VS = 2.5 V and Iset = 50 pA. (d) The height profile along the yellow line in (a).
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Related In: Results  -  Collection

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Show All Figures
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Fig1: STM images for a coverage dependence of SrTiO3homoepitaxy. The 50 × 50-nm2 STM images of (a) 0.6-ML, (b) 0.3-ML, and (c) 0.1-ML SrTiO3 films grown on (2 × 1) reconstructed 0.1% Nb-doped SrTiO3 (001) surfaces at Tsub = 580°C. The crystallographic axes are shown by the yellow arrows in (c), and some larger islands are indicated by the dotted yellow circles. All STM images were obtained with VS = 2.5 V and Iset = 50 pA. (d) The height profile along the yellow line in (a).
Mentions: Figure 1 shows STM topographic images for SrTiO3 films that were 0.6-, 0.3-, and 0.1-monolayer (ML) thick grown at Tsub = 580°C. The height profile across the surface reveals that the deposited layer is 1 uc high (i.e., approximately 0.4 nm), as shown in Figure 1d. When the surface coverage was greater than that of a critical coverage of approximately 0.5 ML, coalescence of islands occurred, and the film exhibited relatively homogeneous 2D growth patterns, as shown in Figure 1a, which were maintained until the coverage reached approximately 1 ML (not shown). However, the growth pattern was inhomogeneous in terms of both size and shape when the coverage was less than that required for coalescence (i.e., <0.5 ML), as can be seen for the 0.3-ML film shown in Figure 1b. The STM image of the 0.1-ML sample shown in Figure 1c reveals islands with a spatial extent of a few nanometers, which were less homogeneous with greater anisotropy than those in the 0.3-ML film. Some islands were elongated along the <100 > crystal axes of SrTiO3. Larger islands appear to be produced by 2D aggregation of smaller square formations.Figure 1

Bottom Line: Second, one-dimensional SrTiO3 islands of a 4 uc width grew along the crystal symmetry directions.These observations suggest that 4 × 4-uc (2) islands act as a minimum nucleation seed, and the addition of SrTiO3 molecular species of the same width is the primary and dominant growth process in SrTiO3 homoepitaxy.A close inspection of the surface of the substrate during the deposition process revealed possible connections between surface reconstruction and energetically favorable nucleation of SrTiO3 islands.

View Article: PubMed Central - PubMed

Affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul National University, Seoul, 151-747 Republic of Korea ; Department of Physics and Astronomy, Seoul National University, Seoul, 151-747 Republic of Korea.

ABSTRACT
SrTiO3 nanoislands on SrTiO3 (001) in a diffusion-limited growth regime were studied using in situ scanning tunneling microscopy (STM). The STM images revealed two characteristic features of nucleation stages. First, the minimum lateral size of the one-unit-cell (uc)-high SrTiO3 islands was 4 × 4 uc (2). Second, one-dimensional SrTiO3 islands of a 4 uc width grew along the crystal symmetry directions. These observations suggest that 4 × 4-uc (2) islands act as a minimum nucleation seed, and the addition of SrTiO3 molecular species of the same width is the primary and dominant growth process in SrTiO3 homoepitaxy. A close inspection of the surface of the substrate during the deposition process revealed possible connections between surface reconstruction and energetically favorable nucleation of SrTiO3 islands.

No MeSH data available.


Related in: MedlinePlus