Nanoscale thickness silicon -on -insulator field effect devices for bio-chemical sensing and heat mediated chemical reactions

Abstract

Semiconductor field effect sensors have been shown to enable the possibility of realizing cost effective, highly dense label-free sensors for the detection of chemical and biological species. Such sensors can be readily integrated with existing platforms for micro total analysis systems, or lab-on-a chip systems. Field effect devices realized using nanowires, or other materials and structures have proven to provide detection sensitivity and selectivity far surpassing current clinical alternatives. In addition, if silicon field effect transistors could be used as nanoscale temperature controllers in a fluidic environment, this would add a new dimension to the versatility of these nanoscale devices. These multi-functional transistors will find broad applications in many systems that had thus far required separate components for each function. Such systems may range from the realization of densely integrated sensors with active surfaces to rapid and local polymerase chain reaction (PCR) systems with integrated sensing. In this dissertation, the fabrication and operation of silicon-on-insulator field effect devices utilizing conventional microfabrication techniques is demonstrated towards realizing such sensor/heater hybrids. The fabrication technique makes the devices amenable for large scale fabrication and seamless integration with existing platforms. Optimization of the device operation is performed by utilizing the inherent pH sensitivity of the devices. Bio-molecular sensing is demonstrated using DNA detection as a model system. The additional functionality of localized heating in fluid using the same devices is also shown, and characterized by temperature dependent fluorescence intensity modulation. Selective functionalization of DNA molecules as well as heat mediated localized exchange reactions on the devices are demonstrated as model applications