Wide process temperature of atomic layer deposition for In2O3thin-film transistors using novel indium precursor (N,N'-di-tert butylacetimidamido)dimethyllindium.

This study introduces a novel heteroleptic indium complex, which incorporates an amidinate ligand, serving as a high-temperature atomic layer deposition (ALD) precursor. The most stable structure was determined using density functional theory and synthesized, demonstrating thermal stability up to 375 °C. We fabricated indium oxide thin-film transistors (In2O3TFTs) prepared with DBADMI precursor using ALD in wide range of window processing temperature of 200 °C, 300 °C, and 350 °C with an ozone (O3) as the source. The growth per cycle of ALD ranged from 0.06 to 0.1 nm cycle-1at different deposition temperatures. X-ray diffraction and transmission electron microscopy were employed to analyze the crystalline structure as it relates to the deposition temperature. At a relatively low deposition temperature of 200 °C, an amorphous morphology was observed, while at 300 °C and 350 °C, crystalline structures were evident. Additionally, x-ray photoelectron spectroscopy analysis was conducted to identify the In-O and OH-related products in the film. The OH-related product was found to be as low as 1% with an increase the deposition temperature. Furthermore, we evaluated In2O3TFTs and observed an increase in field-effect mobility, with minimal change in the threshold voltage (Vth), at 200 °C, 300 °C, and 350 °C. Consequently, the DBADMI precursor, given its stability at highdeposition temperatures, is ideal for producing high-quality films and stable crystalline phases, with wide processing temperature range makeing it suitable for various applications.

Dual-Functional Self-Attachable and Stretchable Interface for Universal Three-Dimensional Modular Electronics.

Stretchable electronics have become essential for custom-built electronics, self-assembling robotics, and wearable devices. Although many stretchable electronics contain integrated systems, they still limit bulky connection systems. We introduce a new dual-functioned self-attachable and stretchable interface (SASI), allowing a direct and instant interconnection between rigid and soft electronics. The SASI consists of a sticky and stretchable substrate and surface-embedded serpentine conductors with the single-sided polyimide fabricated using the embedded transfer process. The adhesion property of the SASI is controlled by the mixed elastomer ratio. The resulting sticky and conductive SASI can instantly adhere to a metal surface and create conductive paths. The SASI serpentine conductors exhibit high stretchability (∼290%) and provide self-attachable, re-attachable, and low-resistant electrical contacts (0.85 ohms in 0.25 mm2) between interfaces without pressure, heat, or extra solder. In addition, three-dimensional curved and modular electronics can be formed with the SASI by compiling functional blocks. SASI provides a novel strategy for assembling functional chips or modules for stretchable electronics, opening a path to onboard integrated electronics that are customizable by users for real-world stretchable electronics.

Synergetic contribution of fluorinated azide for high EQE and operational stability of top-illuminated, semitransparent, photomultiplication-type organic photodiodes.

In this study, it is shown that fluorinated azide, employed as a functional additive to photomultiplication-type organic photodiodes (PM-OPDs), can not only enhance the operational stability by freezing the morphology consisting of matrix polymer/localized acceptor but also stabilize the trapped electron states such that the photomultiplication mechanism can be accelerated further, leading to exceptionally high external quantum efficiency (EQE). The consequent semitransparent OPD consisting of molybdenum oxide (MoO3)/Au/MoO3/photoactive layer/polyethyleneimine ethoxylated/indium tin oxide (ITO) rendered a maximum EQE of over 500 000% and 370 000% under bottom and top illumination, respectively. Owing to the remarkably high EQE, high specific detectivity of 5.6 × 1013 Jones and low noise-equivalent power of 5.35 × 10-15 W Hz-0.5 were also demonstrated. Furthermore, the OPD demonstrated stable performance during 20 h of continuous operation and minimal performance degradation even after the damp heat test. To fully visualize the advantages of the proposed high-EQE, top-illuminated, semitransparent OPD with spectral asymmetry between absorption and detection, a reflection-type fingerprint platform consisting of 1 OPD-1 oxide field-effect transistor complementary metal-oxide-semiconductor backplane (300 ppi) is designed and fabricated. The successful recognition of the fingerprint of one of the authors is demonstrated, which indicates the feasibility of the proposed PM-OPD for sensing weak light intensity.

Ferroelectric Switching in Trilayer Al2O3/HfZrOx/Al2O3 Structure.

Since ferroelectricity has been observed in simple binary oxide material systems, it has attracted great interest in semiconductor research fields such as advanced logic transistors, non-volatile memories, and neuromorphic devices. The location in which the ferroelectric devices are implemented depends on the specific application, so the process constraints required for device fabrication may be different. In this study, we investigate the ferroelectric characteristics of Zr doped HfO2 layers treated at high temperatures. A single HfZrOx layer deposited by sputtering exhibits polarization switching after annealing at a temperature of 850 °C. However, the achieved ferroelectric properties are vulnerable to voltage stress and higher annealing temperature, resulting in switching instability. Therefore, we introduce an ultrathin 1-nm-thick Al2O3 layer at both interfaces of the HfZrOx. The trilayer Al2O3/HfZrOx/Al2O3 structure allows switching parameters such as remnant and saturation polarizations to be immune to sweeping voltage and pulse cycling. Our results reveal that the trilayer not only makes the ferroelectric phase involved in the switching free from pinning, but also preserves the phase even at high annealing temperature. Simultaneously, the ferroelectric switching can be improved by preventing leakage charge.

Ultraflexible and transparent electroluminescent skin for real-time and super-resolution imaging of pressure distribution.

The ability to image pressure distribution over complex three-dimensional surfaces would significantly augment the potential applications of electronic skin. However, existing methods show poor spatial and temporal fidelity due to their limited pixel density, low sensitivity, or low conformability. Here, we report an ultraflexible and transparent electroluminescent skin that autonomously displays super-resolution images of pressure distribution in real time. The device comprises a transparent pressure-sensing film with a solution-processable cellulose/nanowire nanohybrid network featuring ultrahigh sensor sensitivity (>5000 kPa-1) and a fast response time (<1 ms), and a quantum dot-based electroluminescent film. The two ultrathin films conform to each contact object and transduce spatial pressure into conductivity distribution in a continuous domain, resulting in super-resolution (>1000 dpi) pressure imaging without the need for pixel structures. Our approach provides a new framework for visualizing accurate stimulus distribution with potential applications in skin prosthesis, robotics, and advanced human-machine interfaces.

Graphene Electrode Enabling Electrochromic Approaches for Daylight-Dimming Applications.

For environmental reason, buildings increasingly install smart windows, which can dim incoming daylight based on active electrochromic devices (ECDs). In this work, multi-layered graphene (MLG) was investigated as an ECD window electrode, to minimize carbon dioxide (CO2) emissions by decreasing the electricity consumption for building space cooling and heating and as an alternative to the transparent conductor tin-doped indium oxide (ITO) in order to decrease dependence on it. Various MLG electrodes with different numbers of graphene layers were prepared with environmentally friendly poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) to produce ECD cells. Tests demonstrated the reproducibility and uniformity in optical performance, as well as the flexibility of the ECD fabrication. With the optimized MLG electrode, the ECD cells exhibited a very fast switching response for optical changes from transparent to dark states of a few hundred msec.

Transparent Fingerprint Sensor System for Large Flat Panel Display.

In this paper, we introduce a transparent fingerprint sensing system using a thin film transistor (TFT) sensor panel, based on a self-capacitive sensing scheme. An armorphousindium gallium zinc oxide (a-IGZO) TFT sensor array and associated custom Read-Out IC (ROIC) are implemented for the system. The sensor panel has a 200 × 200 pixel array and each pixel size is as small as 50 µm × 50 µm. The ROIC uses only eight analog front-end (AFE) amplifier stages along with a successive approximation analog-to-digital converter (SAR ADC). To get the fingerprint image data from the sensor array, the ROIC senses a capacitance, which is formed by a cover glass material between a human finger and an electrode of each pixel of the sensor array. Three methods are reviewed for estimating the self-capacitance. The measurement result demonstrates that the transparent fingerprint sensor system has an ability to differentiate a human finger's ridges and valleys through the fingerprint sensor array.

Room temperature fabrication of ZnO nanorod films: synthesis and application as a channel layer of transparent thin film transistors.

We report a single-step, solution-based synthesis even at room temperature utilizing a facile sonochemical method to fabricate ZnO nanocrystalline films consisting of well-aligned nanorods.