3 research outputs found
Flexible, Low-Power Thin-Film Transistors Made of Vapor-Phase Synthesized High‑<i>k</i>, Ultrathin Polymer Gate Dielectrics
A series
of high-<i>k</i>, ultrathin copolymer gate dielectrics
were synthesized from 2-cyanoethyl acrylate (CEA) and diÂ(ethylene
glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization
via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD)
method. The chemical composition of the copolymers was systematically
optimized by tuning the input ratio of the vaporized CEA and DEGDVE
monomers to achieve a high dielectric constant (<i>k</i>) as well as excellent dielectric strength. Interestingly, DEGDVE
was nonhomopolymerizable but it was able to form a copolymer with
other kinds of monomers. Utilizing this interesting property of the
DEGDVE cross-linker, the dielectric constant of the copolymer film
could be maximized with minimum incorporation of the cross-linker
moiety. To our knowledge, this is the first report on the synthesis
of a cyanide-containing polymer in the vapor phase, where a high-purity
polymer film with a maximized dielectric constant was achieved. The
dielectric film with the optimized composition showed a dielectric
constant greater than 6 and extremely low leakage current densities
(<3 × 10<sup>–8</sup> A/cm<sup>2</sup> in the range
of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding
thickness for down-scalable cyanide polymer dielectrics. With this
high-<i>k</i> dielectric layer, organic thin-film transistors
(OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free
transfer characteristics with an operating voltage of less than 3
V. Furthermore, the flexible OTFTs retained their low gate leakage
current and ideal TFT characteristics even under 2% applied tensile
strain, which makes them some of the most flexible OTFTs reported
to date. We believe that these ultrathin, high-<i>k</i> organic
dielectric films with excellent mechanical flexibility will play a
crucial role in future soft electronics
Direct Observation of a Carbon Filament in Water-Resistant Organic Memory
The memory for the Internet of Things (IoT) requires versatile characteristics such as flexibility, wearability, and stability in outdoor environments. Resistive random access memory (RRAM) to harness a simple structure and organic material with good flexibility can be an attractive candidate for IoT memory. However, its solution-oriented process and unclear switching mechanism are critical problems. Here we demonstrate iCVD polymer-intercalated RRAM (i-RRAM). i-RRAM exhibits robust flexibility and versatile wearability on any substrate. Stable operation of i-RRAM, even in water, is demonstrated, which is the first experimental presentation of water-resistant organic memory without any waterproof protection package. Moreover, the direct observation of a carbon filament is also reported for the first time using transmission electron microscopy, which puts an end to the controversy surrounding the switching mechanism. Therefore, reproducibility is feasible through comprehensive modeling. Furthermore, a carbon filament is superior to a metal filament in terms of the design window and selection of the electrode material. These results suggest an alternative to solve the critical issues of organic RRAM and an optimized memory type suitable for the IoT era
Functional Circuitry on Commercial Fabric via Textile-Compatible Nanoscale Film Coating Process for Fibertronics
Fabric-based electronic
textiles (e-textiles) are the fundamental components of wearable electronic
systems, which can provide convenient hand-free access to computer
and electronics applications. However, e-textile technologies presently
face significant technical challenges. These challenges include difficulties
of fabrication due to the delicate nature of the materials, and limited
operating time, a consequence of the conventional normally on computing
architecture, with volatile power-hungry electronic components, and
modest battery storage. Here, we report a novel polyÂ(ethylene glycol
dimethacrylate) (pEGDMA)-textile memristive nonvolatile logic-in-memory
circuit, enabling normally off computing, that can overcome those
challenges. To form the metal electrode and resistive switching layer,
strands of cotton yarn were coated with aluminum (Al) using a solution
dip coating method, and the pEGDMA was conformally applied using an
initiated chemical vapor deposition process. The intersection of two
Al/pEGDMA coated yarns becomes a unit memristor in the lattice structure.
The pEGDMA-Textile Memristor (ETM), a form of crossbar array, was
interwoven using a grid of Al/pEGDMA coated yarns and untreated yarns.
The former were employed in the active memristor and the latter suppressed
cell-to-cell disturbance. We experimentally demonstrated for the first
time that the basic Boolean functions, including a half adder as well
as NOT, NOR, OR, AND, and NAND logic gates, are successfully implemented
with the ETM crossbar array on a fabric substrate. This research may
represent a breakthrough development for practical wearable and smart
fibertronics