Fabrication and AC performance of flexible Indium-Gallium-Zinc-Oxide thin-film transistors

The internet of things or foldable phones call for a variety of flexible sensor conditioning and transceiver circuits. However, the realization of high-performance, large-area, and deformable analog circuits is limited by the materials and the processes compatible with mechanically flexible substrates. Among the different semiconductors, InGaZnO is one of the most promising materials to realize high-frequency flexible thin-film transistors (TFTs) and circuits. In this work, the effect of different geometries, including self-aligned, vertical, and double-gate structures on the AC behaviour of flexible IGZO TFTs is presented. All TFTs are based on Al2O3 insulating layers, InGaZnO semiconductor, and polyimide substrates. The presented TFTs exhibit state-of-the-art performance including a field-effect mobility up to 15 cm2 /Vs and a mechanical bendability down to radii of 3.5 mm. Due to different trade-offs required in the fabrication, flexible IGZO TFTs with the shortest channel length of 160 nm do not exhibit the highest measured frequency, whereas exceptional maximum oscillation and transit frequencies of 304 MHz and 135 MHz are demonstrated for 500 nm long self-aligned TFTs. Such optimized transistors can be used to realize entirely flexible analog circuits leading towards imperceptible electronic systems

Biomimetic microelectronics for regenerative neuronal cuff implants

Smart biomimetics, a unique class of devices combining the mechanical adaptivity of soft actuators with the imperceptibility of microelectronics, is introduced. Due to their inherent ability to self‐assemble, biomimetic microelectronics can firmly yet gently attach to an inorganic or biological tissue enabling enclosure of, for example, nervous fibers, or guide the growth of neuronal cells during regeneration

Oxide thin-film electronics on carbon fiber reinforced polymer composite

In this letter, the direct fabrication of amorphous indium-gallium-zinc-oxide thin-film transistors (TFTs) and circuits on a commercial carbon fiber reinforced polymer (CFRP) substrate is demonstrated. The CFRP is encapsulated with a ≈10.6−μm -thick resin layer, although the surface roughness and temperature sensitivity of the substrate are not ideal for the fabrication of electronic devices, we present depletion mode TFTs exhibiting a field effect mobility of 18.3 cm2V−1s−1 , and a common source amplifier, providing a voltage gain of 8 dB and a −3 dB cutoff frequency of 11.5 kHz. The amplifier does not require any input bias voltage and can, hence, be directly used to condition signals originating from various transducers, e.g., piezoelectric strain sensors used to monitor the structural integrity of CFRP elements. This opens the way to the fabrication of smart mechanical CFRP parts with integrated structural integrity monitoring system

Design of bendable high-frequency circuits based on short-channel InGaZnO TFTs

A unique requirement of flexible electronic systems is the need to simultaneously optimize their electrical and mechanical performance. Amorphous InGaZnO thin-film transistors (TFTs) fabricated on free-standing large-area plastic substrates address this issue by providing a carrier mobility >10 cm 2 /Vs, and bendability down to radii as small as 25 μm. At the same time, limitations such as a constrained minimum lateral feature size, the lack of appropriate p-type materials, or the influence of strain have to be considered when designing circuits. Here, models describing the scaling and bending behavior of flexible InGaZnO TFTs, together with the design of strain insensitive circuits operating at megahertz frequencies are presented

Positive charge trapping phenomenon in n-channel thin-film transistors with amorphous alumina gate insulators

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Entirely flexible on-site conditioned magnetic sensorics

The first entirely flexible integrated magnetic field sensor system is realized consisting of a flexible giant magnetoresistive bridge on‐site conditioned using high‐performance IGZO‐based readout electronics. The system outperforms commercial fully integrated rigid magnetic sensors by at least one order of magnitude, whereas all components stay fully functional when bend to a radius of 5 mm

Solution-processed p-type copper(I) thiocyanate (CuSCN) for low-voltage flexible thin-film transistors and integrated inverter circuits

We report on low operating voltage thin-film transistors (TFTs) and integrated inverters based on copper(I) thiocyanate (CuSCN) layers processed from solution at low temperature on freestanding plastic foils. As-fabricated coplanar bottom-gate and staggered top-gate TFTs exhibit hole-transporting characteristics with average mobility values of 0.0016 cm2 V1 s 1 and 0.013 cm2 V1 s 1 , respectively, current on/off ratio in the range 102 –104 , and maximum operating voltages between 3.5 and 10 V, depending on the gate dielectric employed. The promising TFT characteristics enable fabrication of unipolar NOT gates on flexible free-standing plastic substrates with voltage gain of 3.4 at voltages as low as 3.5 V. Importantly, discrete CuSCN transistors and integrated logic inverters remain fully functional even when mechanically bent to a tensile radius of 4 mm, demonstrating the potential of the technology for flexible electronics

Flexible green perovskite light emitting diodes

Flexible perovskite light-emitting diodes (LEDs) have attracted increasing interest to realize ultrathin, light weight, highly conformable and nonfragile vivid displays. Solution-processed lead halide perovskite offers numerous distinctive characteristics such as pure emission color, tunable bandgaps, and low fabrication cost. In this work, green perovskite LEDs (PeLEDs) are fabricated on 50 μm thick polyimide substrates. Using colloidal 2D formamidinium lead bromide perovskite emitter, the PeLEDs show a high current efficiency (ηCE) of 5.3 cd A-1 with a peak emission at 529 ± 1 nm and a narrow width of 22.8 nm. The resultant green emission shows color saturation > 95%, in the Rec. 2020 standard gamut area. To demonstrate mechanical flexibility, the device functionality is tested by dynamic bending experiments down to 10 mm for up to 5000 cycles, resulting in device lifetime over 36 h in a glove box and a drop of ηCE and external quantum efficiency (ηext) as low as 15% and 18%, respectively. For the selective activation of multiple PeLEDs, 7 × 7 passive arrays on rigid and flexible substrates are demonstrated. Moreover, preliminary results of active matrices show the compatibility of PeLEDs with oxide-based Thin-Film Transistors (TFTs) for display applications