Related Experiment Video
Updated: Jul 15, 2026
10:36
Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating
Published on: April 12, 2018
Charge injection across self-assembly monolayers in organic field-effect transistors: odd-even effects
Pablo Stoliar1, Rajendra Kshirsagar, Massimiliano Massi
1Nanotechnology of Multifunctional Materials (NMM) Research Division, CNR-ISMN, Via Gobetti 101, I-40129 Bologna, Italy.
Journal of the American Chemical Society
|May 3, 2007
Summary
Self-assembled monolayers significantly alter organic field-effect transistor performance. Odd-even chain length effects in alkanethiols reveal through-bond tunneling, making transistors sensitive probes of monolayer charge transport.
Area of Science:
- Materials Science
- Organic Electronics
- Surface Chemistry
Background:
- Organic field-effect transistors (OFETs) are crucial for flexible electronics.
- Interface engineering is key to optimizing OFET performance.
- Self-assembled monolayers (SAMs) offer precise control over interfacial properties.
Purpose of the Study:
- To investigate how alkanethiol SAMs modulate pentacene OFET response.
- To elucidate the mechanism of charge carrier injection across organic-metallic interfaces.
- To explore the use of OFETs as sensitive probes for monolayer transport.
Main Methods:
- Fabrication of pentacene OFETs with alkanethiol SAMs on source/drain electrodes.
- Systematic variation of alkanethiol chain length (n).
- Measurement and analysis of charge carrier mobility (μ) and its correlation with chain length.
Main Results:
- Charge carrier mobility (μ) showed significant odd-even fluctuations with alkanethiol chain length (n).
- For short chains (n < 8), mobility increased due to reduced injection barriers and improved ordering.
- For long chains (n ≥ 8), mobility decayed exponentially (β = 0.6 Å⁻¹), indicating through-bond tunneling.
- An odd-even effect was observed, linked to anisotropic coupling between alkanethiol and pentacene.
Conclusions:
- Charge injection occurs via through-bond tunneling of holes mediated by the alkanethiol SAM.
- In the long-chain regime, SAM-mediated charge injection dictates OFET performance.
- OFETs serve as highly sensitive platforms for studying charge transport across single molecular layers.
Related Concept Videos
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
01:27Biasing of Metal-Semiconductor Junctions
Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
01:16Biasing of P-N Junction
The operation of a p-n junction diode involves various biasing conditions, including forward bias, reverse bias, and equilibrium.
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...
01:29Field Effect Transistor
Field-effect transistors (FETs) are integral to electronic circuits and distinguished by their three-terminal setup: the gate, drain, and source. These transistors operate as unipolar devices, which utilize either electrons or holes as charge carriers, in contrast to bipolar transistors, which use both types of carriers. The primary function of the FET is to modulate the flow of these carriers from the source to the drain through a channel. The voltage difference between the gate and source...
01:11P-N junction
A p-n junction is formed when p-type and n-type semiconductor materials are joined together. At the interface of the p-n junction, holes from the p-side and electrons from the n-side begin to diffuse into the opposite sides due to the concentration gradient. This diffusion of carriers leads to a region around the junction where there are no free charge carriers, known as the depletion region. The charge density within the depletion region for the n-side and p-side can be described by the...
01:22Biasing of FET
Biasing a Junction Field Effect Transistor (JFET) is crucial for setting operational parameters and ensuring efficient functioning in electronic circuits. JFETs are characterized by using a single carrier type in N-channel or P-channel configurations, where the channel is surrounded by PN junctions. These junctions are central to the device's ability to control current flow.
In an N-channel JFET, the structure consists of N-type material forming the channel on a P-type substrate, with the gate...
In an N-channel JFET, the structure consists of N-type material forming the channel on a P-type substrate, with the gate...