Related Experiment Video
Updated: Jul 7, 2026
11:42
Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
Biased bilayer graphene: semiconductor with a gap tunable by the electric field effect
Eduardo V Castro1, K S Novoselov, S V Morozov
1CFP and Departamento de Física, Faculdade de Ciências Universidade do Porto, P-4169-007 Porto, Portugal.
Physical Review Letters
|February 1, 2008
Summary
We show that an electric field can tune the electronic band gap in graphene bilayers. This control allows for tunable mid-infrared energies, observed clearly in the quantum Hall regime.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Graphene bilayers exhibit unique electronic properties.
- Controlling the electronic band gap is crucial for novel electronic devices.
- External electric fields offer a promising method for tuning material properties.
Purpose of the Study:
- To demonstrate external control of the electronic band gap in graphene bilayers.
- To quantify the band gap tunability as a function of electronic density.
- To explore the potential for mid-infrared energy applications.
Main Methods:
- Magnetotransport measurements, specifically Shubnikov-de Haas oscillations.
- Cyclotron mass determination from experimental data.
- Application of a tight-binding model for theoretical analysis.
Main Results:
- The electronic band gap of graphene bilayers is controllable via gate bias.
- The band gap can be tuned from zero to mid-infrared energies.
- Fields below 1 V/nm are sufficient for significant gap modulation.
- Gap opening is evident in the quantum Hall regime.
Conclusions:
- External electric fields provide an effective means to engineer the electronic band gap in graphene bilayers.
- This tunability opens possibilities for applications in optoelectronics and tunable infrared devices.
- The findings are consistent with theoretical predictions and experimental observations in condensed matter physics.
Related Concept Videos
01:22Semiconductors
There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
01:24Metal-Semiconductor Junctions
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
01:12Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
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...
01:22Biasing 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...
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...