4 research outputs found
Self-Structured Conductive Filament Nanoheater for Chalcogenide Phase Transition
Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>-based phase-change memories (PCMs), which undergo fast and reversible switching between amorphous and crystalline structural transformation, are being utilized for nonvolatile data storage. However, a critical obstacle is the high programming current of the PCM cell, resulting from the limited pattern size of the optical lithography-based heater. Here, we suggest a facile and scalable strategy of utilizing self-structured conductive filament (CF) nanoheaters for Joule heating of chalcogenide materials. This CF nanoheater can replace the lithographical-patterned conventional resistor-type heater. The sub-10 nm contact area between the CF and the phase-change material achieves significant reduction of the reset current. In particular, the PCM cell with a single Ni filament nanoheater can be operated at an ultralow writing current of 20 μA. Finally, phase-transition behaviors through filament-type nanoheaters were directly observed by using transmission electron microscopy
Chemical Structure–Physicochemical Property Relationships of Copolymers Utilizable for Negative-Tone Photoimaging via Chemical Amplification
We demonstrate an understanding of different physicochemical
properties
of copolymers induced by systematic changes in their structural parameters,
i.e., the chemical structure of the comonomer unit, composition, molecular
weight, and dispersity. The terpolymers were designed to be implemented
in a chemically amplified resist (CAR) to form negative-tone patterns.
With two basic repeating units of 4-hydroxystyrene and 2-ethyl-2-methacryloxyadamantane
as monomers for conventional CARs, the pendant group of the third
methacrylate comonomer was varied from aromatic, aliphatic lactone
to lactone rings to modulate the interaction capability of the copolymer
chains with n-butyl acetate, which is a negative-tone
developer. Along with these structures, the monomer composition, molecular
weight, and dispersity were also controlled. Physicochemical properties
of the synthesized copolymers having controlled structures, i.e.,
dissolution behaviors and quantified Hansen solubility parameters,
surface wetting characteristics, and surface roughness, which can
be important properties affecting patterning capability in high-resolution
lithography, were explored. Furthermore, the feasibility to use experimentally
determined Hansen solubility parameters of the copolymers for the
prediction of pattern formation using a coarse-grained model was assessed.
Our comprehensive studies on the correlation of the structural parameters
of the copolymers with final properties offer fundamental avenues
to attain effective designs of the complex CAR system toward the lithographic
process to achieve a sub-10 nm dimension, which is close to a single-chain
dimension
Flexible Multilevel Resistive Memory with Controlled Charge Trap B- and N-Doped Carbon Nanotubes
B- and N-doped carbon nanotubes (CNTs) with controlled
workfunctions
were successfully employed as charge trap materials for solution processable,
mechanically flexible, multilevel switching resistive memory. B- and
N-doping systematically controlled the charge trap level and dispersibility
of CNTs in polystyrene matrix. Consequently, doped CNT device demonstrated
greatly enhanced nonvolatile memory performance (ON–OFF ratio
>10<sup>2</sup>, endurance cycle >10<sup>2</sup>, retention
time >10<sup>5</sup>) compared to undoped CNT device. More significantly,
the
device employing both B- and N-doped CNTs with different charge trap
levels exhibited multilevel resistive switching with a discrete and
stable intermediate state. Charge trapping materials with different
energy levels offer a novel design scheme for solution processable
multilevel memory
<i>In Vivo</i> Silicon-Based Flexible Radio Frequency Integrated Circuits Monolithically Encapsulated with Biocompatible Liquid Crystal Polymers
Biointegrated electronics have been investigated for various healthcare applications which can introduce biomedical systems into the human body. Silicon-based semiconductors perform significant roles of nerve stimulation, signal analysis, and wireless communication in implantable electronics. However, the current large-scale integration (LSI) chips have limitations in <i>in vivo</i> devices due to their rigid and bulky properties. This paper describes <i>in vivo</i> ultrathin silicon-based liquid crystal polymer (LCP) monolithically encapsulated flexible radio frequency integrated circuits (RFICs) for medical wireless communication. The mechanical stability of the LCP encapsulation is supported by finite element analysis simulation. <i>In vivo</i> electrical reliability and bioaffinity of the LCP monoencapsulated RFIC devices are confirmed in rats. <i>In vitro</i> accelerated soak tests are performed with Arrhenius method to estimate the lifetime of LCP monoencapsulated RFICs in a live body. The work could provide an approach to flexible LSI in biointegrated electronics such as an artificial retina and wireless body sensor networks