3 research outputs found
Transparent and Flexible Graphene Charge-Trap Memory
A transparent and flexible graphene charge-trap memory (GCTM) composed of a single-layer graphene channel and a 3-dimensional gate stack was fabricated on a polyethylene naphtalate substrate below eutectic temperatures (∼110 °C). The GCTM exhibits memory functionality of ∼8.6 V memory window and 30% data retention per 10 years, while maintaining ∼80% of transparency in the visible wavelength. Under both tensile and compressive stress, the GCTM shows minimal effect on the program/erase states and the on-state current. This can be utilized for transparent and flexible electronics that require integration of logic, memory, and display on a single substrate with high transparency and endurance under flex
Reliable Multivalued Conductance States in TaO<sub><i>x</i></sub> Memristors through Oxygen Plasma-Assisted Electrode Deposition with in Situ-Biased Conductance State Transmission Electron Microscopy Analysis
Transition
metal oxide-based memristors have widely been proposed
for applications toward artificial synapses. In general, memristors
have two or more electrically switchable stable resistance states
that device researchers see as an analogue to the ion channels found
in biological synapses. The mechanism behind resistive switching in
metal oxides has been divided into electrochemical metallization models
and valence change models. The stability of the resistance states
in the memristor vary widely depending on: oxide material, electrode
material, deposition conditions, film thickness, and programming conditions.
So far, it has been extremely challenging to obtain reliable memristors
with more than two stable multivalued states along with endurances
greater than ∼1000 cycles for each of those states. Using an
oxygen plasma-assisted sputter deposition method of noble metal electrodes,
we found that the metal-oxide interface could be deposited with substantially
lower interface roughness observable at the nanometer scale. This
markedly improved device reliability and function, allowing for a
demonstration of memristors with four completely distinct levels from
∼6 × 10<sup>–6</sup> to ∼4 × 10<sup>–8</sup> S that were tested up to 10<sup>4</sup> cycles per
level. Furthermore through a unique in situ transmission electron
microscopy study, we were able to verify a redox reaction-type model
to be dominant in our samples, leading to the higher degree of electrical
state controllability. For solid-state synapse applications, the improvements
to electrical properties will lead to simple device structures, with
an overall power and area reduction of at least 1000 times when compared
to SRAM
Palladium-Decorated Hydrogen-Gas Sensors Using Periodically Aligned Graphene Nanoribbons
Polymer residue-free graphene nanoribbons (GNRs) of 200 nm
width at 1 μm pitch were periodically generated in an area of
1 cm<sup>2</sup> via laser interference lithography using a chromium
interlayer prior to photoresist coating. High-quality GNRs were evidenced
by atomic force microscopy, micro-Raman spectroscopy, and X-ray photoelectron
spectroscopy measurements. Palladium nanoparticles were then deposited
on the GNRs as catalysts for sensing hydrogen gases, and the GNR array
was utilized as an electrically conductive path with less electrical
noise. The palladium-decorated GNR array exhibited a rectangular sensing
curve with unprecedented rapid response and recovery properties: 90%
response within 60 s at 1000 ppm and 80% recovery within 90 s in nitrogen
ambient. In addition, reliable and repeatable sensing behaviors were
revealed when the array was exposed to various gas concentrations
even at 30 ppm