Home
People
Research
Publications
Facilities
Location
Projects
Events
Links
Services
|
Group-IV semiconductor nanostructures
| ||
Nanostructures constitute a fascinating field of research. The unusual properties of nanostructured materials compared with those exhibited by the same material under its bulk or thin film form have revolutionized the materials science. In particular, Si nanostructures are experiencing a growing impact in strategic fields such as microelectronics, photonics and photovoltaics. The demonstration that Si nanocrystals (nc) can efficiently emit light at room temperature or that they can store electrical charges has made them very attractive materials for the fabrication of Si-based light sources or non-volatile memories, respectively. More recently, Si nc and Si nanowires (NWs) have received a considerable attention for photovoltaic applications. An essential requirement for successful technological applications of Si nanostructures is the control of their size, shape, volume density, crystallinity, defect density, surface passivation, since most of their properties critically depend on all these parameters. This demand has required a great effort to convert some of the techniques traditionally used for thin film deposition (chemical vapour deposition, sputtering, electron beam evaporation) in advanced tools for a highly controlled synthesis of a wide range of Si nanostructures. In the last years cluster deposition, chemical vapour deposition and sputtering have been widely employed for the synthesis of Si nc (or amorphous Si nanoclusters) embedded in SiO2. The most established process involves the deposition of a SiOx film, followed by a thermal process to induce the phase separation between Si and SiO2. The deposition parameters, as well as the post-deposition annealing process, have been optimized to reach the high degree of control of the structural properties which is needed for the application of Si nanostructures in microelectronics or photonics. As an example, in order to efficiently emit photons, Si nc size must be smaller than 5 nm and their volume density needs to be carefully controlled to avoid the occurrence of non-radiative de-excitation phenomena. More recently, chemical vapour deposition and electron beam evaporation have been successfully used for the synthesis of Si NWs. By using a suitable metal catalyst, it is possible to grow epitaxial and defect-free NWs with selected orientation and length through the control of the substrate temperature and of the evaporated thickness of Si. |
||
RECENT HIGHLIGHTS by MATIS: |
||
| We demonstrated the heteroepitaxial growth of single-crystal faceted Ge nanowires by electron beam evaporation on top of (111) Si substrates. Despite the non-UHV growth conditions, SEM and TEM images show that NWs have specific crystallographic growth directions ([111], [110] and [112]) and that specific surface crystallographic planes ({111} or {110}) correspond to the [110] and [112] growth direction. Moreover, we studied in details the Ge NWs structural properties. The temperature dependence of the NWs length and of the frequency of each crystallographic orientation has been elucidated. Finally, the microscopic growth mechanisms have been investigated. Heteroepitaxial growth and faceting of Ge nanowires on (111) Si by electron beam evaporation Pecora E. F., Irrera A., Artoni P., Boninelli S., Bongiorno C., Spinella C., Priolo F. Electrochemical and Solid-State Letters 13, K53 (2010) - DOI: 10.1149/1.3339677 |
 |
|
| The growth mechanisms of epitaxial Si nanowires (NWs) grown by electron beam evaporation (EBE) and catalyzed through gold droplets are identifed. NWs with (111), (100) and (110) orientation have been found and the growth rate is observed to have a strong orientation dependence, suggesting a microscopic growth mechanism based on the atomic ordering along (110) ledges onto (111)-oriented terraces. By properly changing the range of experimental conditions we demonstrate how it is possible to favor the axial growth of the NWs, define their length and control their crystallographic orientation. Control of growth mechanisms and orientation in epitaxial Si nanowires grown by electron beam evaporation Irrera A., Pecora E. F., Priolo F. Nanotechnology 20, 135601 (2009) - DOI: 10.1088/0957-4484/20/13/135601 |
 |
|
| A comparison between the structural and optical properties of Si nanoclusters prepared by plasma enhanced chemical vapour deposition (PECVD) and magnetron sputtering has been performed. In PECVD films only around 30% of the Si excess agglomerates in clusters while an almost complete agglomeration occurs in sputtered films. This difference has a strong impact on the optical properties of the two systems. Microstructural evolution of SiOx films and its effect on the luminescence of Si nanoclusters Franzò G., Miritello M., Boninelli S., Lo Savio R., Grimaldi M.G., Priolo F., Iacona F., Nicotra G., Spinella C., Coffa S. J. Appl. Phys. 104, 094306 (2008) - DOI: 10.1063/1.3006735 |
 |
|
| Raman experiments were performed on Si quantum dots and a theory was developed accounting for the Raman energy shifts and for the linewidth enhancement. Modified Raman confinement model for Si nanocrystals Faraci G., Gibilisco S., Russo P., Pennisi A. R., La Rosa S. Phys. Rev. B 73, 33307 (2006) - DOI: 10.1103/PhysRevB.73.033307 |
 |
|
PARTICIPANTS |
||
| ARTONI Pietro | 095 3785239 | |
| FARACI Giuseppe | 095 3785337 | |
| FRANZò Giorgia | 095 3785346 | |
| GIBILISCO Santo | 095 3785235 | |
| IACONA Fabio | 095 3785288 | |
| IRRERA Alessia | 095 3785239 | |
| LO SAVIO Roberto | 095 3785239 | |
| MIRITELLO Maria | 095 3785239 | |
| PECORA Emanuele Francesco | 095 3785239 | |
| PENNISI Agata | 095 3785390 | |
| PRIOLO Francesco | 095 3785401 | |