Multi-scale Investigation of the Nitride perovskite LaWN3: towards a functional integration in thin films

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MINd-LWN is a research project that will pave the way to controlling polar nitride perovskites by providing design strategies for theirintegration into semiconductor devices without the loss of their intrinsic functionalities. Lanthanum tungsten nitride (LWN) is a polarmaterial in the emerging class of nitride perovskites. This new class of materials is of great interest for developing oxygen-freefunctional materials, integrable in microelectronic devices and able to operate at a lower voltage. However, little is known about theirstability in thin films. LWN is theoretically predicted to be ferroelectric and thus able to display stable and ordered electric dipoles,controllable through an electric field; therefore promising for memory applications in electronics. This material has recently beensynthesised in thin films but did not hold its promises: no ferroelectricity was experimentally verified, and measurements of itsstoichiometry revealed the presence of a significant concentration of nitrogen vacancies, likely interfering with its functionalities.While control parameters such as temperature, defects, strain, and electrostatics have a crucial effect on electric dipoles, their role inthe context of nitride perovskites is unrevealed. Therefore, I propose a thorough theoretical study of the atomistic and electronicstructures and the polarisation properties of LWN thin films using advanced density functional theory and machine learningtechniques. Specifically, I will study the interplay between thickness, defect concentration, and temperature to understand andcontrol their influence on the ferroelectric stability. This project will set the scene for possible breakthroughs in the semiconductorindustry by allowing to merge decades of discoveries in perovskite materials with the intensive industrial development ofsemiconductors. MINd-LWN will allow future the design of more efficient devices, which will have direct technological and economicconsequences.