Abstract:
Early and rapid detection of biomarkers indicative of various diseases has been an intensive
field of research for past few decades. A wide variety of biosensing devices that employ
nanoparticles or nanostructures have been investigated in a number of studies throughout the
world. Potentiometric biosensors based on field-effect transistors have shown excellent
performance due to several advantages like rapid electrical detection without the need for
labeling the biomolecules, low power consumption, portability, inexpensive mass production,
and the possibility of on-chip integration of both sensor and measurement systems. The 2D
materials like graphene and transition metal dichalcogenides are highly promising, as they not
only can provide excellent electrostatics due to their atomically thin structures but also possess
planar nature, which is amenable to large-scale integrated device processing and fabrication.
In this thesis, we develop a comprehensive theoretical framework to study 2D material based
nanoscale sensors and correlate the geometry and physical properties of these sensors to their
sensing performance of target molecules. The main objective of this work is to set some
guidance for future design, implementation and optimization of these novel biosensors. A part
of this work focuses on the scope of 2D material based FETs in sensing solution pH and
detection of biomolecule in wet environment. TMDC monolayer materials show good
sensitivity as pH sensor while operating above Nernst limit with back gate operation. With
proper surface functionalization, monolayer TMDC FETs can be used for highly sensitive and
selective detection of biomolecule in subthreshold regime. It is found that performance of the
TMDC pH and Biosensors can be optimized through careful design of physical and operating
parameters in Double-Gated Field Effect Transistor. In addition, this work also investigates
the prospect of electrical biosensing in dry environment with state of the art devices structure
like Junctionless Double Gate MOSFET and 2D material like MoS2 by developing analytical
model for surface potential and current in such devices. The detection of both charged and
neutral biomolecules have been analyzed under dry environment situation by investigating the
electrical characteristics of n-type Junctionless Double Gate MOSFET. Bio-sensing
application in dry environment using DMFET can be a viable alternative to overcome the
screening limited sensitivity in electrolyte based systems and it can used to detect even charge
neutral biomolecule. In addition, this work also offers a comparative study of sensor
performance as a function of device physical parameters to maximize detection capability
under dry environment condition.
