Study of Silicon Nanostructures

Research Area: Ultrafast Spectroscopy
Status: Finished
Project leaders: Othonos, Andreas
Members: Haralambos Tsangaris
Elena Vahou
Constantina Kanari
Emmanouil Lioudakis
In cooperation with Nanowires
Proposed start date: 2006-01-01
Proposed end date: 2009-01-01
Funded by: Research Promotion Foundation
Funding: 150000.00 EUR

The quest for silicon-based semiconductor material suitable for fabricating light emitting devices and lasers is of immense scientific and commercial interest. Silicon nanocrystals are a promising candidate material for such light emitting devices as well as modulators, optical amplifiers and other optoelectronic devices. Fabrication of these semiconductor materials and devices requires specialized and costly infrastructure that is not available in Cyprus at the moment. This project aimed to study in detail the fabrication and improvement of novel silicon nanocrystal based optoelectronic devices through the access of infrastructure at the Institute of Microelectronics (IMEL) at National Centre for Scientific Research “Demokritos” in Greece. A consortium of researchers from the University of Cyprus and IMEL combined their efforts toward this goal. The linear and non-linear optical properties of the nanocrystals were investigated and studied in depth. Emphasis was placed on understanding the ultrafast carrier dynamics using non-degenerate excite and probe techniques.

Description:

The nanocrystals used in this work were be fabricated using Low Pressure Chemical Vapor Deposition of amorphous silicon, followed by oxidation and annealing at high temperatures, or based on electrochemical dissolution of bulk crystalline silicon in the transition regime. This fabrication technique became possible through the access to the infrastructure facilities at the Institute of Microelectronics. Researchers from the Center of Ultrafast Science at the University of Cyprus in close collaboration with the IMEL research team were actively involved in the fabrication of high quality silicon nanocrystals samples. We were able in this project to make use of the facilities at IMEL, to further develop and study complex nanocrystals structures with final objective their use in optoelectronic devices. Optimization of the nanocrystal structural and surface properties was achieved through continuous feedback of surface and electrical measurements to the fabrication team. Optical characterization has been carried out at the University of Cyprus by the Centre of Ultrafast Science. We have used transient degenerate and non-degenerate absorption measurements using femtosecond ultrafast amplifiers in conjunction with an optical parametric amplifier and white light super continue generation to study in detail the ultrafast dynamics of photo-excited carriers in these novel silicon based nanostructures.

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