SCHOOL OF NANO SCIENCE

Seminar

Realisation of the smart chemical and biological sensing systems with high sensitivities necessitates the combination of complementary metal oxide semiconductor (CMOS) technology with other established technologies providing new functionalities. In this work, the suspended silicon nanowires (SSiNWs) were investigated to be used as the sensing head. The surface modification with self-assembled monolayers, which provides the selectivity ofdetection, was found to make the electrical conduction almost temperature independent in 10-115oC range. This protects the charge-based sensors against the temperature variations.A novel transistor structure was proposed including a SSiNW and two side gates with a uniform high level of doping concentration across the device. A 2D model was developed to explain the transistor behaviour of device by taking the field fringing into account. The cross-sectional aspect ratio of the SiNW and its thickness were shown to be the key factors, which control the 2D depletion of SiNW channel. Two lines along the SiNW on the top and bottom surfaces are the most charge sensitive parts of device demonstrating its potential to be used in highly sensitive charge-based sensors. The sensitivity can be optimised by applying two different voltages to the side gates individually. To improve the sensitivity towards single molecule detection, a modification in the device geometry was suggested to convert it into a suspended silicon singleelectron transistor. A hybrid simulation approach was developed to design and optimise such devices. It was shown that the suspension is an important factor to reduce the total capacitance of the island and consequently increasing the operating temperature. These achievements pave the way towards a new generation of smart chemical and biological sensors with ultra-high sensitivities on the nano-electromechanical system (NEMS)-CMOS integration platform.

Seminar Speaker:
Dr. Adel Ghiass
Date :
27 Feb. 2013
Time :
11:00 - 12:30