Project Details
Projekt
Understanding the Limits of Switching Endurance in Nitride Ferroelectrics Through Advanced Analytic Methods: Towards Fatigue-Free AlScN -Devices [UNLimit]
Subject Area
Synthesis and Properties of Functional Materials
Experimental Condensed Matter Physics
Experimental Condensed Matter Physics
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 563148605
The limited switching endurance of the novel nitride ferroelectrics (NF) currently represents the most significant challenge with respect to the operation of all-nitride ferroelectric devices. Although the phenomenon of performance loss as a function of device cycling (referred to as "fatigue") in NF devices has been empirically investigated, the underlying microscopic mechanisms remain unclear. Moreover, there has been no knowledge-driven attempt to address the underlying physical issues. The "UNLimit" project employs a synergistic combination of advanced analytical techniques, namely in-situ transmission electron microscopy (TEM) and operando hard X-ray photoelectron spectroscopy (HAXPES), in conjunction with cutting-edge thin film deposition of AlN-based NFs. The objective is to elucidate the fundamental microscopic mechanisms underlying functional "fatigue" and to enhance the NF and defect properties through materials engineering. This will ultimately lead to a significant increase in the switching endurance of NFs. At the microscopic level, this necessitates the capacity to examine structural alterations on the atomic scale, the discernment of crystalline defect configurations, and the monitoring of chemical interface phenomena within the NF. This is essential to comprehend the genesis of critical degradation. Ex situ, in situ, and operando investigations will establish a link between the ferroelectric properties and the atomistic and electronic changes at the device level, with a focus on the single-digit nanometer range and below. This will be achieved by making use of the different length and energy scales that can be probed through TEM and HAXPES. These results will then be integrated with advanced growth techniques that revolve around the epitaxial sputter deposition of NFs, particularly AlScN. The "UNLimit" project aims to provide a comprehensive scientific understanding of the following key questions through this feedback loop: (I) What is the effect of structural defects on ferroelectric switching, and can their impact be controlled, for example, by improving the quality of the epitaxial film? (II) Does nitrogen scavenging by the electrodes contribute to the aging of NFs, and which electrodes are effective in preserving interfaces during cycling? (III) What role do oxygen contaminants play, and what passivation schemes can be identified to suppress the accumulation and migration of oxygen? (IV) What type of charge carriers are generated during repeated ferroelectric switching? Where are they formed? Do they accelerate the breakdown of a device? Is it possible to suppress their formation through materials engineering? Answers to the above questions will provide an ideal platform to solve the most significant issue with respect to the performance of the emerging NFs. Thus, 'UNLimit' is well positioned to make a key contribution towards the first generation of all-nitride ferroelectric devices with unprecedented functionality.
DFG Programme
Priority Programmes
