A Comparative Study of Pt/AlScN/Pt-Based Thin-Film Metal-Ferroelectric-Metal Capacitors on GaN and Si Substrates.

AlScN is a nitride-ferroelectric compatible with both CMOS and GaN technology. The origin of ferroelectricity in these ternary nitrides relies on the full inversion of nitrogen atom positions, which is a significantly different structural mechanism than conventional perovskites. Therefore, its ferroelectric characteristics exhibit a high remanent polarization and a tunable coercive field but suffer heavily from leakage currents during the switching event.

In-Grain Ferroelectric Switching in Sub-5 nm Thin Al Sc N Films at 1 V.

Analog switching in ferroelectric devices promises neuromorphic computing with the highest energy efficiency if limited device scalability can be overcome. To contribute to a solution, one reports on the ferroelectric switching characteristics of sub-5 nm thin Al Sc N films grown on Pt/Ti/SiO /Si and epitaxial Pt/GaN/sapphire templates by sputter-deposition. In this context, the study focuses on the following major achievements compared to previously available wurtzite-type ferroelectrics: 1) Record low switching voltages down to 1 V are achieved, which is in a range that can be supplied by standard on-chip voltage sources.

Thermal Stability of the Ferroelectric Properties in 100 nm-Thick AlScN.

The discovery of ferroelectricity in aluminum scandium nitride (AlScN) opens technological perspectives for harsh environments and space-related memory applications, considering the high-temperature stability of piezoelectricity in aluminum nitride. The ferroelectric and material properties of 100 nm-thick AlScN are studied up to 873 K, combining both electrical and in situ X-ray diffraction measurements as well as transmission electron microscopy and energy-dispersive X-ray spectroscopy. The present work demonstrates that AlScN can achieve high switching polarization and tunable coercive fields in a 375 K temperature range from room temperature up to 673 K.

AlScN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion.

Ferroelectric thin films of wurtzite-type aluminum scandium nitride (Al1−xScxN) are promising candidates for non-volatile memory applications and high-temperature sensors due to their outstanding functional and thermal stability exceeding most other ferroelectric thin film materials. In this work, the thermal expansion along with the temperature stability and its interrelated effects have been investigated for Al1−xScxN thin films on sapphire Al2O3(0001) with Sc concentrations x (x = 0, 0.09, 0.

Growth of Highly c-Axis Oriented AlScN Films on Commercial Substrates.

In this work, we present a method for growing highly -axis oriented aluminum scandium nitride (AlScN) thin films on (100) silicon (Si), silicon dioxide (SiO) and epitaxial polysilicon (poly-Si) substrates using a substrate independent approach. The presented method offers great advantages in applications such as piezoelectric thin-film-based surface acoustic wave devices where a metallic seed layer cannot be used. The approach relies on a thin AlN layer to establish a wurtzite nucleation layer for the growth of -AlScN films.

Thin-Film-Based SAW Magnetic Field Sensors.

In this work, the first surface acoustic-wave-based magnetic field sensor using thin-film AlScN as piezoelectric material deposited on a silicon substrate is presented. The fabrication is based on standard semiconductor technology. The acoustically active area consists of an AlScN layer that can be excited with interdigital transducers, a smoothing SiO layer, and a magnetostrictive FeCoSiB film.

A spiking and adapting tactile sensor for neuromorphic applications.

The ongoing research on and development of increasingly intelligent artificial systems propels the need for bio inspired pressure sensitive spiking circuits. Here we present an adapting and spiking tactile sensor, based on a neuronal model and a piezoelectric field-effect transistor (PiezoFET). The piezoelectric sensor device consists of a metal-oxide semiconductor field-effect transistor comprising a piezoelectric aluminium-scandium-nitride (AlScN) layer inside of the gate stack.

Complex Magnetic Exchange Coupling between Co Nanostructures and Ni(111) across Epitaxial Graphene.

We report on the magnetic coupling between isolated Co atoms as well as small Co islands and Ni(111) mediated by an epitaxial graphene layer. X-ray magnetic circular dichroism and scanning tunneling microscopy combined with density functional theory calculations reveal that Co atoms occupy two distinct adsorption sites, with different magnetic coupling to the underlying Ni(111) surface. We further report a transition from an antiferromagnetic to a ferromagnetic coupling with increasing Co cluster size.