Indium–Gallium–Zinc Oxide Schottky Diodes Operating across the Glass Transition of Stimuli‐Responsive Polymers

Abstract

Implementing stable electronic components on smart, soft materials can facilitate increasingly complex functionality in body‐worn and implanted devices for biomedical applications. The fabrication and characterization of indium–gallium–zinc oxide (IGZO)‐based Schottky diodes on a thiol–ene/acrylate shape memory polymer (SMP) that softens in response to physiological stimuli, including temperature and moisture, are presented. A platinum–IGZO Schottky junction is formed on the softening polymer assisted by ultraviolet‐ozone (UV‐O3) surface treatment. The effects of the UV‐O3 treatment conditions on the Schottky barrier properties are examined. The diode operation is evaluated in dry and wet conditions with varying temperatures up to 75 °C, revealing that the fabricated diodes preserve their performance even after the softening effect (i.e., an orders‐of‐magnitude modulus change) is induced in the polymer substrate. Additionally, high‐frequency diode operation up to 1 GHz is demonstrated for devices with an active area of 10 000 µm2 at 0 V bias. These devices can serve as building blocks for high‐frequency rectifying circuits and in more sophisticated arrangements toward applications in, for example, wireless bioelectronic implants.

Indium-gallium-zinc oxide Schottky diodes on softening substrates for rectifying bioelectronic circuits

“…The present work expands on the previous study of the Schottky diodes fabricated on this emerging polymer material [49], and further elaborates on the ability of these devices to rectify RF signals under pseudo-physiological conditions for potential wireless bioelectronic applications. Specifically, we demonstrate IGZO Schottky diodes in half-wave rectification circuits that rectify RF signals upon softening of the polymer substrate, after enduring cyclic mechanical stresses, and after being aged in a simulated physiological medium, under load resistances approximating that of biological tissue.…”

“…Besides, these polymers are non-cytotoxic and compatible with cleanroom microfabrication processes [43][44][45]. Leveraging these favorable properties, efforts have been made to use these materials as substrates for softening electronics including neural probes, thin-film transistors, high-k dielectric capacitors, and thin-film Schottky diodes [46][47][48][49][50].…”

Rapid safety assessment and mitigation of radiofrequency induced implant heating using small root mean square sensors and the sensor matrix Qs

“…Thus, ensuring maximum sensitivity, while avoiding measurements at current null positions, which do not necessarily correspond to a tip current null, eg, due to wavelength effects. Even though designs exist to eg, integrate diodes in electrodes, 88 positioning of RMS sensors at the implant tip may not be feasible without impairing the functionality of the medical implant. However, sensor location is not necessarily restricted to the implant tip.…”

Flexible a‐IGZO TFT‐Based Circuit for Active Addressing in Neural Stimulation Electrode Arrays

“…Consequently, they have been widely used as substrates for neural interfaces and soft electronics. [14,[20][21][22] Implementing the proposed stimulation system on these polymers, not only flexible but also softening and conformable, offers an advantage over conventional rigid silicon technology. In terms of the TFT active material, we utilize amorphous-indium-galliumzinc-oxide (a-IGZO) due to its proven compatibility with thiolene/acrylate polymer substrates.…”