Related Experiment Video
Updated: Aug 28, 2025
08:58
Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation
Published on: December 21, 2015
8.5K
Semimetal to semiconductor transition in Bi/TiO2 core/shell nanowires
M Kockert1, R Mitdank1, H Moon2
1Novel Materials Group, Humboldt-Universität zu Berlin 10099 Berlin Germany kockert@physik.hu-berlin.de sfischer@physik.hu-berlin.de.
Nanoscale Advances
|September 22, 2022
Summary
Strain engineering in bismuth-based (Bi-based) core/shell nanowires significantly alters thermoelectric properties. Compressive strain from titanium dioxide (TiO2) shells can enhance the Seebeck coefficient by opening a band gap in Bi, improving thermoelectric performance.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Thermoelectric materials convert heat to electricity and vice versa.
- Bismuth (Bi)-based nanostructures are promising for thermoelectric applications.
- Strain engineering offers a route to tune material properties.
Purpose of the Study:
- To characterize thermoelectric and structural properties of Bi-based core/shell nanowires.
- To investigate the influence of strain on thermoelectric transport in Bi/TiO2 nanowires.
- To compare strain effects in Bi/TiO2, Bi/Te, and pure Bi nanowires.
Main Methods:
- Full thermoelectric and structural characterization of individual nanowires.
- Temperature-dependent measurements of electrical conductivity, Seebeck coefficient, and thermal conductivity.
- Comparative analysis of nanowires with varying diameters and compositions.
Main Results:
- Surface scattering in core/shell nanowires significantly reduces electrical and thermal conductivity compared to bulk Bi.
- Compressive strain in Bi/TiO2 nanowires leads to decreased electrical conductivity with decreasing temperature.
- Strain-induced band opening in Bi/TiO2 increases the Seebeck coefficient by 10-30% compared to bulk Bi.
Conclusions:
- Strain engineering is an effective method to enhance thermoelectric properties of Bi-based nanowires.
- The TiO2 shell's compressive strain can induce a semiconducting state in Bi, boosting the Seebeck coefficient.
- Lattice relaxation under excessive strain recovers the semimetallic state, impacting thermoelectric performance.
More Related Videos
Related Concept Videos
01:24Metal-Semiconductor Junctions
449
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...
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...
449
01:27Biasing of Metal-Semiconductor Junctions
322
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...
322
01:20Types of Semiconductors
890
Intrinsic semiconductors are highly pure materials with no impurities. At absolute zero, these semiconductors behave as perfect insulators because all the valence electrons are bound, and the conduction band is empty, disallowing electrical conduction. The Fermi level is a concept used to describe the probability of occupancy of energy levels by electrons at thermal equilibrium. In intrinsic semiconductors, the Fermi level is positioned at the midpoint of the energy gap at absolute zero. When...
890
02:58Properties of Transition Metals
26.9K
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
26.9K
01:22MOSFET: Enhancement Mode
454
Enhancement-mode MOSFETs are pivotal components in electronics, distinguished by their capacity to act as highly efficient switches. They are part of the larger family of metal-oxide Semiconductor Field-Effect Transistors (MOSFETs). They are available in two types: p-channel and n-channel, each tailored to specific polarity operations.
In their basic form, enhancement-mode MOSFETs are typically non-conductive when the gate-source voltage (Vgs) is zero. This default 'off' state means no...
In their basic form, enhancement-mode MOSFETs are typically non-conductive when the gate-source voltage (Vgs) is zero. This default 'off' state means no...
454
01:12Fermi Level Dynamics
328
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...
328