Organic FET Electrode Interfaces Using Dual Admolecule Layers
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Solution Overview
Problem
Existing organic FETs face challenges in increasing ON-state current and reducing contact resistance due to insufficient conductivity and grain size of the semiconductor layer at electrode interfaces, which are not adequately addressed by prior techniques using short molecule admolecule layers.
Innovation Solution
The implementation of a specific organic molecule layer structure, where a first alkanethiol molecule layer is formed on the top surfaces of the source and drain electrodes, and a second organic molecule layer, consisting of p-thiocresol or thiophenol molecules, is formed on the side surfaces, enhancing the grain size and contact between electrodes and the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short molecule admolecule layer is used to improve carrier injection efficiency, then contact resistance is reduced, but the grain size of the semiconductor layer at the electrode interface remains insufficient
Solution Approach 1:
The single admolecule layer is segmented into two distinct layers: a first admolecule layer (short molecule like octadecanethiol) that improves carrier injection efficiency and reduces contact resistance, and a second admolecule layer (long molecule like hexadecyltrimethylammonium bromide) that promotes grain growth of the semiconductor layer. This segmentation allows each layer to specialize in one function, resolving the contradiction between reducing contact resistance and increasing grain size.
Solution Approach 2:
Different regions of the electrode interface are assigned different properties through the two-layer structure. The first admolecule layer provides low contact resistance properties at the metal-semiconductor interface, while the second admolecule layer provides grain growth promotion properties in the semiconductor layer formation region. This local differentiation of functional properties resolves the contradiction between improving carrier injection and increasing grain size.
2Object-affected harmful factors
If the immersion time is extended to improve water repellence of the electrode surface, then the contact angle increases, but the thickness of the admolecule layer increases and carrier injection efficiency decreases
Solution Approach 1:
The water repellence function is segmented from the carrier injection function. The first admolecule layer (formed by short immersion) provides carrier injection efficiency, while the second admolecule layer (formed by extended immersion) provides water repellence. This segmentation allows the electrode surface to achieve high water repellence (contact angle 101°) without compromising carrier injection efficiency, as the second layer's water-repellent properties do not interfere with the first layer's electronic properties.
3Ease of manufacture
If a single type of admolecule layer is used to simplify the fabrication process, then the manufacturing complexity is reduced, but both contact resistance and grain size cannot be optimized simultaneously
Solution Approach 1:
The fabrication process is segmented into two sequential immersion steps, each optimized for a specific function. The first immersion in short molecule solution is simple and quick, while the second immersion in long molecule solution builds upon the first. This segmented approach maintains relative fabrication simplicity while achieving dual optimization of contact resistance and grain size that a single admolecule layer cannot provide.
Solution Approach 2:
The electrode interface structure is made composite with two different admolecule layers having distinct chemical and physical properties. The first layer uses short molecules for electronic coupling, while the second layer uses long molecules for grain growth promotion. This composite structure at the nanoscale enables simultaneous optimization of multiple interface properties without significantly complicating the overall fabrication process.
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
This configuration significantly increases the ON-state current and reduces contact resistance, enabling the organic FET to operate effectively at low voltages, such as in wireless ID tags, with improved carrier injection efficiency.
Implementation Method 1
The first organic molecule layer is formed between a top surface of a metal source electrode and a semiconductor layer and between a top surface of a metal drain electrode and the semiconductor layer
Implementation Method 2
The second organic molecule layer is formed between an opposing side surface of the source electrode and the semiconductor layer and between an opposing side surface of the drain electrode and the semiconductor layer
Data Source
AI summary
An organic FET in which the interfaces (electrode interfaces) between a semiconductor layer and a source electrode and between a semiconductor layer and a drain electrode are improved by employing a technique to increase ON-state current (driving current) and to reduce contact resistance. The organic FET includes a substrate; a gate insulating film disposed on the substrate; a metal source electrode and a metal drain electrode disposed on the gate insulating film in such a manner that they face each other in a horizontal direction; and an organic semiconductor layer covering the gate insulating film, the source electrode and the drain electrode, wherein a first organic molecule layer and a second organic molecule layer are formed on the interfaces (electrode interfaces) between a semiconductor layer and a source electrode and between a semiconductor layer and a drain electrode.