Energy efficient two-dimensional process-in-memory devices

The motion of negatively charged electrons generates charge current in solid state conductors and nowadays electronic elements and devices such as diodes, transistors and even computer processors function due to the manipulation of the charge current. Electrons, beside orbiting the positive nucleus in an atom, also spin about their own axis, giving rise to a quantum mechanical degree of freedom known as spin. Depending on the sense of rotation clock-wise or counter-clock-wise the spin of an electron is visualized as pointing up or down. The magnetic devices used extensively in memory applications like hard disk drives or magnetic random access memories exploit the spin of electrons by manipulating a spin polarized charge current, where the current has a majority of the up or down spin electrons, unlike the pure charge current. Spin based memories are attractive for their non-volatility and high durability but offer low resistance changes, whereas semiconductor logic transistors, such as the field effect transistors, provide large resistance tunability but do not provide memory function. In both approaches, non-volatility of data and energy efficiency remain major issues to resolve. However, a tie-up of the spin and orbital motion of electrons, known as spin-orbit coupling in solids has the capability of generating, in non-magnetic materials like metals and semiconductors, dissipationless pure spin currents, where only the spins move and not the charges. This approach of utilizing the spin -orbit coupling is expected to lead to the development of a new technology addressed as spin-orbitronics by using spin-orbit torque at interfaces of magnetic and non-magnetic layers through which non-volatile, energy efficient electronic devices will be realized. In particular, the emergence of atomically thin two-dimensional (2D) materials, has led to the emergence of quantum devices that are not only energy efficient, but also complement the existing silicon technology. In this project, a spin-orbit torque driven field-effect transistor (SOTdFET) fabricated from 2D van der Waals heterostructure is designed and realized, in the perspective of practical process- in-memory (PiM) devices with low power consumption, sustainability, endurance and integrability with the existing complementary metal-oxide-semiconductor (CMOS) architecture. The outcome of the project will provide alternative approaches to Boolean logic operations, by exploiting hybrid 2D materials in building-blocks for prospective quantum processors and quantum spintronic devices.