Research Interest

Low dimensional magnetotransport phenomenon in 2D semiconductors (III-V heterostructures, Graphene and TMDCs) Classically the effect of a magnetic field applied perpendicular to the plane of the 2DEG is to cause the electrons to move in circles. For low fields, the electrons undergoes scattering before completing one complete revolution and hence the transport is diffusive. In this case, the Hall resistance has a linear dependence on magnetic field as expected semi classically and diagonal resistivity is approximately constant. At higher fields the electrons are able to complete one complete cyclotron orbit without scattering resulting in the formation of equally spaced energy levels called Landau levels and the nature of the transport changes drastically. The linear dependence of Hall resistance is interrupted by plateaux which extend for a range of magnetic field and diagonal resistivity almost goes to zero in those regions. This is the integer quantum Hall effect . The term integer quantum Hall effect is assigned to represent the above mentioned behavior because the plateaux and minima are centered on integer filling factor (the number of Landau levels that are filled with electrons) and the plateaux resistances are equal to the ratio of two fundamental constants (h/e²) divided by the nearest integer filling factor.

Nanostructures and their device application To widen the scope of the semiconducting devices the structural, optical, and electrical properties of materials can be physically and chemically engineered to bring in novel results that are absent in the conventional material systems. Transition Metal Dichalcogenides and Metal Oxides are two important classes of materials that are widely investigated due to their diverse functionalities and a wide variety of electrical, optical, thermal, and magnetic properties. All these properties can be modified to suit different applications by physical and chemical engineering. The research work presented in this thesis focuses on tailoring the structural, electrical, and optical characteristics of transition metal dichalcogendies and Metal Oxide nanostructures.

Two terminal memory devices for next generation computation:

In the era of artificial intelligence, the realization of “universal memory” devices has stimulated great interest in developing thinnest memory storage device capable of offering high storage density, high energy efficiency, great durability, fast access operation, and low cost. Many new types of non-volatile memory(NVM) devices has been emerged such as ferroelectric random access memory (Fe-RAM), phase change memory (PCM), spin-transfer torque random access memory (STT RAM), and resistive random-access memories (RRAMs). Out of this, RRAMs (also called as memristors) exhibits outstanding characteristics that provides simultaneously fast processing and permanent storage of large volumes of data and the scalable nanoscale dimension of memristor (atomristor) making it possible for high density and large-scale integration. Memristors have entered a stage of rapid development with the discovery of first working titanium dioxide(TiO₂) based memristive device which has fast bipolar non-volatile switching behaviour. They have offered captivating performances which includes in-memory computing,femtojoule energy consumption, and sub-nanosecond switching speed.

Since 2D MoS₂ based memristors are most stable and widely studied 2D semiconductor having good flexibility, high transparency, and tunable memory windows for memristor application,we created MoS₂ based atomristor, which can further be extended to other monolayer TMDCs based atomristors. Large area single layer MoS₂ was obtained via photo-exfoliation by applying potential difference across bulk MoS₂ which is placed on a conducting surface. This photo-exfoliated monolayer MoS₂ which is the functional layer is sandwiched between indium tin oxide and Tallium di-sulphide(TaS₂) electrodes using lithographic-free technique and exhibits memristor-like behavior.

BITS Pilani

Research Interest

Research Interest

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