Research
Currently the activities of the group focus on the following:
A) Materials
a) Si nanowires,and their applications
The activity on semiconductor nanostructures started within this research group at the early nineties and is conducted within different EU projects. Worldwide pioneering results of the group in this field include the following: Light emitting Si nanopillars were first developed (APL 66(9), 1114 (1995), an electroluminescent device based on vertical Si nanowires was first developed (APL 69(15), 2267 (1996), the growth and investigation of the properties of single and multilayers of two-dimensional arrays of Si nanocrystals (NCs) with controllable size, embedded in SiO2was developed, Si NC memories with good characteristics using LPCVD Si nanocrystal synthesis was developed.
Currently, the group focuses on the following activities:
- Fabrication and properties of two-dimensional arrays of Si nanocrystals embedded in SiO2 for solar cell applications
- SiNWs by metal-assisted chemical etching: synthesis, characterization and applications in nanowire solar cells
b)Porous Si material technology and applications
The group has important expertise and know-how, as well as different proprietary processes in the field of porous Si material and technology. Existing processes include the fabrication of porous Si thick films formed locally on the Si substrate, porous Si free standing close-type membranes over cavity fabricated in a single electrochemical process and porous Si cantilevers and suspended membranes fabricated by electrochemistry. The porous material is composed of either randomly distributed pores or straight vertical pores. Pioneering results of the group in this field include the development of efficient porous Si micro-hotplate technology on the Si wafer, a low power Si flow sensor, a flow meter for the car engine and a system for respiration control using the low power flow sensor.
Currently the group develops applications of porous Si as a local substrate on the Si wafer for the on–chip integration of RF passive devices on the Si wafer.
c) Fabrication, properties and applications of porous anodic alumina thin films on Si
Porous anodic alumina thin films on Si with highly ordered hexagonally arranged pores are fabricated by electrochemistry and used either as template materials for growing nanowires and other nanostructures within the pores or as masking materials for Si nano-patterning. Porous anodic alumina is also used as a high-k dielectric material in memory devices and in metal-oxide-metal (MIM) capacitors.
B) Devices and systems
a) RF passive devices
The Head of the group coordinates the RF activity within the European Network of Excellence FP7 ICT "Nanofunction" (http://www.nanofunction.eu/), devoted to the following:
- On-chip RF substrate technologies
- CMOS-integrated RF transmission lines, inductors, filters and antennas
- Nanowire interconnects and nano-antennas
The group focuses on the investigation of the porous Si platform as a local substrate on Si for the on-chip integration of RF passive devices. It also investigates novel device topologies. In addition, it investigates the use of metal nanowires in RF interconnects and nano-antennas.
b) Flow sensors and their application in the medical and the automotive fields
A high performance miniaturized flow sensor was developed that was used in a system for respiration control and in a flow meter for measuring air flow at the inlet of car engine.
c) Memory devices
The group has a long expertise in nanocrystal memories using Si nanocrystals in SiO2 layers fabricated by LPCVD of Si and high temperature annealing/oxidation. More recently it studied WORM memories using porous anodic alumina dielectric.