Thin films of the element bismuth — an environmentally friendly and scalable material — can exhibit a tunable room-temperature nonlinear Hall effect, which could be of use in the development of optoelectronic devices. The scanning electron microscopy image on the cover shows a bismuth Hall cross device, which is used to explore magnetotransport and the nonlinear Hall effect in the polycrystalline thin films.

See Makushko et al. and News & Views by Belosevich et al.

Spectral processors for wireless communication can be created using acoustic resonators made from 3D silicon nano-fins with hafnia–zirconia ferroelectric gates wrapped around them. The scanning electron microscopy image on the cover shows an array of filters created by electrically coupling 3D resonators with different frequencies, with the different devices highlighted by different false colours.

See Hakim et al.

With the help of processes that can recycle organic conductors, semiconductors and dielectrics, flexible electronic devices can be created in which each component of the device can be recaptured and reused. The computer-generated image on the cover shows a flexible electronic device developed using this closed-loop recycling approach.

See Park et al.