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Kinetics of Si and Ge nanowires growth through electron beam evaporation.

Artoni P, Pecora EF, Irrera A, Priolo F - Nanoscale Res Lett (2011)

Bottom Line: Moreover, Si NWs growth requires a higher evaporated fluence before the NWs become to be visible.These differences arise in the different kinetics behaviors of these systems.The authors investigate the microscopic growth mechanisms elucidating the contribution of the adatoms diffusion as a function of the evaporated atoms direct impingement, demonstrating that adatoms play a key role in physical vapor deposition (PVD) NWs growth.

View Article: PubMed Central - HTML - PubMed

Affiliation: MATIS IMM-CNR, Via Santa Sofia 64, I-95123 Catania, Italy. alessia.irrera@ct.infn.it.

ABSTRACT
Si and Ge have the same crystalline structure, and although Si-Au and Ge-Au binary alloys are thermodynamically similar (same phase diagram, with the eutectic temperature of about 360°C), in this study, it is proved that Si and Ge nanowires (NWs) growth by electron beam evaporation occurs in very different temperature ranges and fluence regimes. In particular, it is demonstrated that Ge growth occurs just above the eutectic temperature, while Si NWs growth occurs at temperature higher than the eutectic temperature, at about 450°C. Moreover, Si NWs growth requires a higher evaporated fluence before the NWs become to be visible. These differences arise in the different kinetics behaviors of these systems. The authors investigate the microscopic growth mechanisms elucidating the contribution of the adatoms diffusion as a function of the evaporated atoms direct impingement, demonstrating that adatoms play a key role in physical vapor deposition (PVD) NWs growth. The concept of incubation fluence, which is necessary for an interpretation of NWs growth in PVD growth conditions, is highlighted.

No MeSH data available.


Related in: MedlinePlus

Si (red dots) and Ge (blue squares) NWs measured length as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2.
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Figure 2: Si (red dots) and Ge (blue squares) NWs measured length as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2.

Mentions: Figure 2 reports the Si (red dots) and Ge (blue squares) NWs lengths as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2. The measured NWs length increases as the temperature increases up to a maximum value which is obtained at 450°C for the Ge and 480°C for the Si NWs. At higher temperatures, the length saturates and, as is well evident for Ge NWs, it decreases, and NWs growth is eventually inhibited. This trend resembles a bell-shaped behavior, with the length reaching its maximum value at an intermediate temperature. This is the result of the competition between two different and opposite temperature-dependent processes, both related to the adatoms contribution to the axial growth. The first one is the adatoms diffusion which is brought about by increasing the substrate temperature. As a consequence, the adatoms surface diffusivity increases, and the collecting area enlarges. The axial NWs growth increases because of the increased number of the contributing adatoms. Instead, adatoms can desorb from the substrate and come back into the gaseous phase; the rate of this process is increased by further increasing the substrate temperature, making it detrimental for the growth.


Kinetics of Si and Ge nanowires growth through electron beam evaporation.

Artoni P, Pecora EF, Irrera A, Priolo F - Nanoscale Res Lett (2011)

Si (red dots) and Ge (blue squares) NWs measured length as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211214&req=5

Figure 2: Si (red dots) and Ge (blue squares) NWs measured length as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2.
Mentions: Figure 2 reports the Si (red dots) and Ge (blue squares) NWs lengths as a function of the growth temperature for an evaporated fluence of 1.75 × 1018 cm-2. The measured NWs length increases as the temperature increases up to a maximum value which is obtained at 450°C for the Ge and 480°C for the Si NWs. At higher temperatures, the length saturates and, as is well evident for Ge NWs, it decreases, and NWs growth is eventually inhibited. This trend resembles a bell-shaped behavior, with the length reaching its maximum value at an intermediate temperature. This is the result of the competition between two different and opposite temperature-dependent processes, both related to the adatoms contribution to the axial growth. The first one is the adatoms diffusion which is brought about by increasing the substrate temperature. As a consequence, the adatoms surface diffusivity increases, and the collecting area enlarges. The axial NWs growth increases because of the increased number of the contributing adatoms. Instead, adatoms can desorb from the substrate and come back into the gaseous phase; the rate of this process is increased by further increasing the substrate temperature, making it detrimental for the growth.

Bottom Line: Moreover, Si NWs growth requires a higher evaporated fluence before the NWs become to be visible.These differences arise in the different kinetics behaviors of these systems.The authors investigate the microscopic growth mechanisms elucidating the contribution of the adatoms diffusion as a function of the evaporated atoms direct impingement, demonstrating that adatoms play a key role in physical vapor deposition (PVD) NWs growth.

View Article: PubMed Central - HTML - PubMed

Affiliation: MATIS IMM-CNR, Via Santa Sofia 64, I-95123 Catania, Italy. alessia.irrera@ct.infn.it.

ABSTRACT
Si and Ge have the same crystalline structure, and although Si-Au and Ge-Au binary alloys are thermodynamically similar (same phase diagram, with the eutectic temperature of about 360°C), in this study, it is proved that Si and Ge nanowires (NWs) growth by electron beam evaporation occurs in very different temperature ranges and fluence regimes. In particular, it is demonstrated that Ge growth occurs just above the eutectic temperature, while Si NWs growth occurs at temperature higher than the eutectic temperature, at about 450°C. Moreover, Si NWs growth requires a higher evaporated fluence before the NWs become to be visible. These differences arise in the different kinetics behaviors of these systems. The authors investigate the microscopic growth mechanisms elucidating the contribution of the adatoms diffusion as a function of the evaporated atoms direct impingement, demonstrating that adatoms play a key role in physical vapor deposition (PVD) NWs growth. The concept of incubation fluence, which is necessary for an interpretation of NWs growth in PVD growth conditions, is highlighted.

No MeSH data available.


Related in: MedlinePlus