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Ordered Arrays of SiGe Islands from Low-Energy PECVD.

Bollani M, Bonera E, Chrastina D, Fedorov A, Montuori V, Picco A, Tagliaferri A, Vanacore G, Sordan R - Nanoscale Res Lett (2010)

Bottom Line: Although most of the works in literature are based on MBE, one of the possible advantages of low-energy plasma-enhanced chemical vapor deposition (LEPECVD) is a wider range of deposition rates, which in turn results in the possibility of growing islands with a high Ge concentration.We will show that LEPECVD can be effectively used for the controlled growth of ordered arrays of SiGe islands.Island morphology was characterized by AFM, while μ-Raman was used to analyze the Ge content inside the islands and the composition differences between islands on patterned and unpatterned areas of the substrate.

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ABSTRACT
SiGe islands have been proposed for applications in the fields of microelectronics, optoelectronics and thermoelectrics. Although most of the works in literature are based on MBE, one of the possible advantages of low-energy plasma-enhanced chemical vapor deposition (LEPECVD) is a wider range of deposition rates, which in turn results in the possibility of growing islands with a high Ge concentration. We will show that LEPECVD can be effectively used for the controlled growth of ordered arrays of SiGe islands. In order to control the nucleation of the islands, patterned Si (001) substrates were obtained by e-beam lithography (EBL) and dry etching. We realized periodic circular pits with diameters ranging from 80 to 300 nm and depths from 65 to 75 nm. Subsequently, thin films (0.8-3.2 nm) of pure Ge were deposited by LEPECVD, resulting in regular and uniform arrays of Ge-rich islands. LEPECVD allowed the use of a wide range of growth rates (0.01-0.1 nm s(-1)) and substrates temperatures (600-750°C), so that the Ge content of the islands could be varied. Island morphology was characterized by AFM, while μ-Raman was used to analyze the Ge content inside the islands and the composition differences between islands on patterned and unpatterned areas of the substrate.

No MeSH data available.


Related in: MedlinePlus

AFM gradient images of a patterned area following the deposition of 2.8 nm of Ge at 600°C (a), 700°C (b) and 750°C (c). The growth rate was 0.1 nm s−1. At low temperature (a), we have formation of small SiGe 3D structures around pits. They are also observed at intermediate temperature (b), although in smaller quantity. At high temperature (c), only very few islands are formed which are not on the top of pits, and some pits appear to be uncapped with islands
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Figure 2: AFM gradient images of a patterned area following the deposition of 2.8 nm of Ge at 600°C (a), 700°C (b) and 750°C (c). The growth rate was 0.1 nm s−1. At low temperature (a), we have formation of small SiGe 3D structures around pits. They are also observed at intermediate temperature (b), although in smaller quantity. At high temperature (c), only very few islands are formed which are not on the top of pits, and some pits appear to be uncapped with islands

Mentions: At low temperature (600°C) as shown in Fig. 2a, the mobility of Ge atoms was too low, and we obtained small islands between patterned areas. Increasing the temperature (750°C), the Ge mobility increases [14,15], and we obtained 3D islands positioned correctly (Fig. 2c) with only very few islands between the pits. At this temperature, we varied the amount of deposited Ge to investigate the trapping effect of the holes [16]. In the range of amount of deposited Ge (0.9–3.2 nm), we did not observe islands in the region between the holes. Following models reported in literature [14,17], this means that the migration length of Ge adatoms ( with D the diffusion coefficient) is greater than the distance between the holes. For a fixed patterning dimension, the island volume increases proportionally to the thickness of the deposited Ge. From high-resolution AFM scans, we can identify {105}, {113} and {15 3 23} facets at the sides of the islands and {1 1 10} facets near their tops, while the tops themselves are parallel to (001).


Ordered Arrays of SiGe Islands from Low-Energy PECVD.

Bollani M, Bonera E, Chrastina D, Fedorov A, Montuori V, Picco A, Tagliaferri A, Vanacore G, Sordan R - Nanoscale Res Lett (2010)

AFM gradient images of a patterned area following the deposition of 2.8 nm of Ge at 600°C (a), 700°C (b) and 750°C (c). The growth rate was 0.1 nm s−1. At low temperature (a), we have formation of small SiGe 3D structures around pits. They are also observed at intermediate temperature (b), although in smaller quantity. At high temperature (c), only very few islands are formed which are not on the top of pits, and some pits appear to be uncapped with islands
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2991192&req=5

Figure 2: AFM gradient images of a patterned area following the deposition of 2.8 nm of Ge at 600°C (a), 700°C (b) and 750°C (c). The growth rate was 0.1 nm s−1. At low temperature (a), we have formation of small SiGe 3D structures around pits. They are also observed at intermediate temperature (b), although in smaller quantity. At high temperature (c), only very few islands are formed which are not on the top of pits, and some pits appear to be uncapped with islands
Mentions: At low temperature (600°C) as shown in Fig. 2a, the mobility of Ge atoms was too low, and we obtained small islands between patterned areas. Increasing the temperature (750°C), the Ge mobility increases [14,15], and we obtained 3D islands positioned correctly (Fig. 2c) with only very few islands between the pits. At this temperature, we varied the amount of deposited Ge to investigate the trapping effect of the holes [16]. In the range of amount of deposited Ge (0.9–3.2 nm), we did not observe islands in the region between the holes. Following models reported in literature [14,17], this means that the migration length of Ge adatoms ( with D the diffusion coefficient) is greater than the distance between the holes. For a fixed patterning dimension, the island volume increases proportionally to the thickness of the deposited Ge. From high-resolution AFM scans, we can identify {105}, {113} and {15 3 23} facets at the sides of the islands and {1 1 10} facets near their tops, while the tops themselves are parallel to (001).

Bottom Line: Although most of the works in literature are based on MBE, one of the possible advantages of low-energy plasma-enhanced chemical vapor deposition (LEPECVD) is a wider range of deposition rates, which in turn results in the possibility of growing islands with a high Ge concentration.We will show that LEPECVD can be effectively used for the controlled growth of ordered arrays of SiGe islands.Island morphology was characterized by AFM, while μ-Raman was used to analyze the Ge content inside the islands and the composition differences between islands on patterned and unpatterned areas of the substrate.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
SiGe islands have been proposed for applications in the fields of microelectronics, optoelectronics and thermoelectrics. Although most of the works in literature are based on MBE, one of the possible advantages of low-energy plasma-enhanced chemical vapor deposition (LEPECVD) is a wider range of deposition rates, which in turn results in the possibility of growing islands with a high Ge concentration. We will show that LEPECVD can be effectively used for the controlled growth of ordered arrays of SiGe islands. In order to control the nucleation of the islands, patterned Si (001) substrates were obtained by e-beam lithography (EBL) and dry etching. We realized periodic circular pits with diameters ranging from 80 to 300 nm and depths from 65 to 75 nm. Subsequently, thin films (0.8-3.2 nm) of pure Ge were deposited by LEPECVD, resulting in regular and uniform arrays of Ge-rich islands. LEPECVD allowed the use of a wide range of growth rates (0.01-0.1 nm s(-1)) and substrates temperatures (600-750°C), so that the Ge content of the islands could be varied. Island morphology was characterized by AFM, while μ-Raman was used to analyze the Ge content inside the islands and the composition differences between islands on patterned and unpatterned areas of the substrate.

No MeSH data available.


Related in: MedlinePlus