Organic Molecular Memory Asymmetric Dipole Rectification
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Solution Overview
Problem
Designing an organic molecular memory cell that effectively combines both rectifying and memory properties is challenging due to the need for a large ON/OFF ratio in the variable resistive element and appropriate voltage distribution across the memory cell components, which is difficult to achieve with existing organic molecules.
Innovation Solution
An organic molecular memory structure is proposed, featuring a π conjugated chain with electron-accepting or donating groups arranged asymmetrically, a phenyl group with specific substituents, and a linker group to create a dipole moment that enhances rectification and memory properties by varying resistance based on electric field presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single organic molecule is designed to provide both rectifying and memory properties, then device complexity is reduced, but it is difficult to achieve both sufficient rectification and high ON/OFF ratio simultaneously
Solution Approach 1:
The organic molecule is divided into distinct functional segments: a rectifying portion (with electron-donating and electron-accepting groups) and a memory portion (with specific molecular structure for resistance switching). This segmentation allows each part to optimize its specific function while being integrated in a single molecule, resolving the contradiction between device simplicity and performance reliability.
Solution Approach 2:
Different regions of the molecule are assigned different electronic properties: the rectifying portion has asymmetric electron distribution with donor and acceptor groups, while the memory portion has structures optimized for resistance switching. This local differentiation enables simultaneous achievement of rectification and memory effects with high performance.
2Use of energy by moving object
If the resistance value of the rectifying element is made sufficiently smaller than the variable resistive element in low resistance state, then operating voltage is reduced, but the ON/OFF ratio of the memory element must be maintained at high levels
Solution Approach 1:
The molecule's electronic parameters are precisely tuned through molecular design: the HOMO level, electron affinity, and dipole moment are optimized to achieve appropriate resistance ratios between rectifying and memory portions. This parameter optimization enables low operating voltage while maintaining high ON/OFF ratio for reliable signal reading.
3Volume of moving object
If organic molecules are used to reduce element size for higher density, then miniaturization is achieved, but designing molecules with appropriate rectification and memory properties becomes more difficult
Solution Approach 1:
The designed organic molecule serves multiple functions simultaneously: rectification, memory storage, and size reduction. By integrating these functions into a single molecular structure with specific arrangements of donor/acceptor groups and memory portions, the patent achieves miniaturization without proportionally increasing design complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure achieves a high ON/OFF ratio and efficient rectification, allowing for a compact, high-density memory cell with improved reliability and reduced operating voltage, effectively addressing the limitations of existing organic molecular memory designs.
Implementation Method 1
a donor group D tends to release an electron, and thus tends to accept a hole but does not accept an electron. Thus, a hole flows from an electrode to D, but an electron does not. On the other hand, an acceptor group A tends to accept an electron but does not tend to release an electron, and does not constitute a hole. Thus, an electron flows from an electrode to A, but a hole does not. Thus, a current flows only in a direction from D to A, developing rectification.
Implementation Method 2
there is a report that a self-assembled monolayer of molecules each having an acceptor nitro group and a donor amino group on a phenylene ethynylene skeleton exhibits a negative differential resistance, and develops a memory property that the ON/OFF ratio (the ratio of a current flowing when the same voltage is applied before switching to that after switching) is 1000 or greater.
Data Source
AI summary
An organic molecular memory in an embodiment includes a first conducive layer, a second conductive layer, and an organic molecular layer provided between the first conductive layer and the second conductive layer, the organic molecular layer having an organic molecule, the organic molecule having a linker group bonded to the first conductive layer, a π conjugated chain bonded to the linker group, and a phenyl group bonded to the π conjugated chain opposite to the linker group and facing the second conductive layer, the π conjugated chain including electron-accepting groups or electron-donating groups arranged in line asymmetry with respect to a bonding direction of the π conjugated chain, the phenyl group having substituents R0, R1, R2, R3, and R4 as shown in the following formula, the substituent R0 being an electron-accepting group or an electron-donating group.