Flexible Selenium Nanowires with Tuneable Electronic Bandgaps.

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Tuning semiconductor properties without chemical alteration is crucial for advanced materials.
• Characterizing nanomaterials is difficult due to their size and polydispersity.
• Understanding structure-property relationships in elemental semiconductors at the nanoscale is key.

Purpose of the Study:

• To investigate the structural plasticity and electronic bandgaps of selenium nanowires.
• To correlate atomic structures of selenium with their tunable electronic properties.
• To develop a predictive phase diagram for selenium nanostructures.

Main Methods:

• Utilized boron nitride nanotubes (BNNTs) as nano test tubes to confine selenium.
• Employed aberration-corrected scanning transmission electron microscopy (STEM) and ultra-low-loss electron energy loss spectroscopy (EELS).
• Performed real-time transmission electron microscopy (TEM) imaging of phase transitions.

Main Results:

• Observed distinct phases of selenium with structural plasticity between 0.4 and 3.0 nm.
• Correlated structural phases with electronic bandgaps ranging from 2.2 to 2.5 eV.
• Developed a 1D phase diagram predicting selenium structure based on nanotube diameter, independent of host nanotube chemistry.

Conclusions:

• Selenium's bandgap variation diverges from bulk and is non-monotonic with nanotube diameter, indicating counteracting effects of conformational distortions and quantum confinement.
• The developed phase diagram provides a roadmap for controlling selenium nanostructures.
• Findings enable the design of tuneable nanoscale electronic and optical devices.