Film-thickness-dependent conduction in ordered Si quantum dot arrays.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Silicon nanostructures, particularly silicon quantum dots (Si QDs) in SiO(2), are crucial for photonic and photovoltaic applications.
• Previous fabrication methods for ordered Si QDs in SiO(2) relied on complex multiple bilayer stacks, limiting control over inter-dot distance and size.

Purpose of the Study:

• To demonstrate, for the first time, the fabrication of spatially well-ordered Si QDs in SiO(2) without using a multilayer approach.
• To investigate the impact of film thickness and QD ordering on electrical conduction mechanisms and photocarrier generation.

Main Methods:

• Fabrication of Si QDs in SiO(2) using a single-layer deposition technique.
• Characterization using Transmission Electron Microscopy (TEM) for structural ordering.
• Grazing Incidence X-ray Diffraction (GIXRD) to confirm QD crystallinity.
• Photoluminescence spectroscopy to analyze bandgap properties.
• Low-temperature current-voltage (I-V) measurements to study conduction mechanisms.

Main Results:

• Demonstrated the fabrication of spatially well-ordered 5 nm Si QDs in SiO(2) via a single-layer deposition method, dependent on initial film thickness.
• Confirmed QD crystallinity using GIXRD and observed augmented bandgap values via photoluminescence.
• Observed film thickness and order-dependent conduction mechanisms, transitioning from temperature-dependent to temperature-independent tunneling in ordered nanocrystals.
• Reported significant conduction and photocarrier generation in Si QDs embedded in SiO(2), contrary to expectations for dielectric materials.

Conclusions:

• The single-layer fabrication method offers precise control over Si QD ordering and inter-dot distance.
• The observed electrical conduction and photocarrier generation in ordered Si QDs are highly promising for their integration into advanced photovoltaic devices.
• This work paves the way for developing novel silicon-based nanomaterials for efficient energy conversion applications.