Metal oxides, once a scientific curiosity,1 have evolved into a transformative technology for modern electronics.2 Their applications span energy, lighting, information displays, microelectronics, and sensors.3–7 The ability of metal oxides to deliver semiconducting channels in thin-film transistors (TFTs) over large-area substrates with enhanced performance has propelled them from a mere curiosity to an enabling technology for a continuously expanding range of applications.

The flat panel display industry is a prime example of the pivotal role played by metal oxide TFTs, offering numerous attractive attributes absent from competing technologies.2,8,9 Recent efforts have been focused on new semiconducting and dielectric materials, with the primary goal of enhancing the device's field-effect mobility and operational stability. However, the emergence of oxide-based resistive switching devices has opened up exciting new avenues of research, extending the application space to memory and memristive devices for neuromorphic computing applications.10,11

Metal oxides stand out in the field of thin film electronics due to their unique physical attributes. Their optical transparency, eco-friendly nature, and compatibility with energy-efficient manufacturing techniques set them apart from other technologies. These characteristics are gaining increasing importance in light of the harmful environmental effects of the traditional semiconductor industry. To this end, metal oxides offer the potential for a shift toward more environmentally responsible products that can help reduce society's dependence on incumbent technologies, promising to revolutionize our fast-paced, high-tech world.

This special topic in Applied Physics Letters attempts to capture the latest developments in metal oxide-based materials and their applications in the broader field of electronics. It covers the research and exploration of functional materials, cutting-edge manufacturing techniques, advanced device designs, and a plethora of applications. The key highlights from different contributions to this special issue are organized based on their specific area of research:

  1. transistors with improved functionalities;12–29 

  2. memory and memristive devices;30–42 

  3. detectors, energy storage, and lighting devices;43–51 

  4. fundamental studies.52–68 

Several papers focus on advancing the TFT performance via device and channel engineering approaches. AlGhamdi et al.22 and Abe et al.20 explore low-dimensional channel architectures that exhibit energy quantization phenomena and study their impact on electron transport across the channel. Yu et al.13 report tri-channel Ga2O3 FinFET for radio frequency (RF) applications, while Hu et al.24 demonstrated flexible RF transistors and mixers based on ultrathin layers of In2O3 as the channel.

The bias stability has also been investigated in different metal oxide TFTs. Shi et al.21 used amorphous Ga2O3 to passivate a-ITZO channels in TFTs and improve their bias stability. Cai et al.15 applied La-doping to both enhance the performance and stability of InZnO TFTs, while Hu et al.28 explored W:F co-doped ZnSnO channels to demonstrate stable, solution-processed top-gate TFTs. Ding et al.14,23 used In2O3 nanofibers to develop transistors with improved stability and higher electron mobility, while Chang et al.27 studied channel migration phenomena that are critical for device degradation, using dual channel a-InGaZnO TFTs. The passivation of In2O3 channels with fluorine was explored by Zhang et al.,16 which improved the electrical characteristics of the TFTs. Sheleg and Tessler12 propose a spatial-doping method for double injection function oxide TFT and use simulation to highlight the operating characteristics of this new type of device.

The gate leakage conduction mechanism through a bilayer dielectric comprised of HfO2/SiNx in a-IGZO TFTs has been studied by Wang et al.,17 providing key insights into this important process. Scheideler and Subramanian29 review recent developments in printing metal oxide TFTs, while Hu et al.26 focus on low-temperature growth methods for high electron mobility InSnO TFTs. The development of flexible electrodes using silver nanowire-networks was reported by Yang et al.19 Kim et al.18 reported on the development of hole-transporting (p-channel) SnO TFTs, while Mashooq et al.25 integrated ambipolar SnO TFTs to realize high-gain complementary-like NOT gates.

The significant areas of memory and memristive devices and their applications have also been covered with important contributions. Representative studies include developing multi-terminal devices with memristive functionality using different materials and device architectures.30,34,36–38,40,41 Kim et al.31 described the development of a vertical ferroelectric TFT array with nanometer-scale gate electrodes for high-density three-dimensional memory applications. Several other groups have reported different device architectures and material concepts for memory applications.32,33,35,39,42

Several studies report the application of metal oxides in various detector technologies. These include the development of photodetectors,43,46,50,51 chemical sensors,44,48 and thermal detectors.49 Moreover, Chen et al.45 used metal oxide heterojunctions to demonstrate capacitors with high-energy storage efficiency and temperature stability, while Ide et al.47 developed amorphous oxide semiconductor-based phosphors for light-emitting diode applications, further highlighting the enormous potential of metal oxides for a broad range of applications.

Several studies have focused on investigating fundamental processes in various material systems using various experimental techniques.52–68 Some representative highlights include the study of the intrinsic spin Hall effect in Pt/magnetic oxide heterostructures,52 the in-plane anisotropy in MoS2 layers grown on molybdenum oxide,68 phase structure-dependent ionic conductivity in Sm2O3,54 self-heating phenomena in SrSnO3 films,55 photoinduced conductivity in the two-dimensional electron gas at the SrTiO3/BiFeO3 interface,62 and the low-temperature crystallization of In2O3 using a photoactive additive.64 

In conclusion, this special topic highlights recent advancements in the science and technology of metal oxides. Despite the huge diversity in materials and uses, metal oxides continue to surprise with the development of new knowledge and innovative applications. Moreover, the prospect for more circular products makes metal oxides a timely technology for our society.

We would like to thank all the authors for submitting their work to this Special Topic and the journal editors and editorial staff who assisted us in completing this timely collection of articles.

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