Negative-charge-functionalized carbon nanodot: a low-cost smart cold emitter

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Carbon nanomaterials are extensively studied for electron emission applications.
• Understanding the relationship between material properties and emission performance is crucial for device development.

Purpose of the Study:

• To investigate the size-dependent cold emission properties of carbon nanodots (CNDs).
• To correlate electron emission characteristics with the work function and surface charge of CNDs.
• To theoretically predict and experimentally verify the field emission performance of CNDs.

Main Methods:

• Theoretical calculations using ANSYS Maxwell software and density functional theory.
• Experimental determination of work function using ultraviolet photoelectron spectroscopy.
• Evaluation of field emission properties including current density, turn-on field, and field enhancement factor.

Main Results:

• Cold emission properties of CNDs are confirmed to be size-dependent.
• Work function is found to depend on the charge state of functional groups on the CND surface.
• The smallest CND (2.5 nm) exhibited the lowest work function (5.18 eV) and superior field emission characteristics.
• High current density (∼1.45 mA cm^-2), low turn-on field (0.04 V μm^-1), and high field enhancement factor (2.7 × 10⁵) were achieved.

Conclusions:

• Zero-dimensional CNDs demonstrate superior field emission activity compared to higher-dimensional carbon nanomaterials.
• The study provides a comprehensive understanding of CNDs' field emission mechanisms.
• CNDs are promising candidates for advanced electron emission applications.