Quantum-confined stark effect in single CdSe nanocrystallite quantum dots

Area of Science:

• Materials Science
• Quantum Mechanics
• Nanotechnology

Background:

• The quantum-confined Stark effect (QCSE) describes the influence of electric fields on the optical properties of quantum-confined systems.
• Cadmium selenide (CdSe) nanocrystallites, or quantum dots (QDs), exhibit unique quantum confinement effects due to their small size.
• Understanding the behavior of QDs under electric fields is crucial for their application in optoelectronic devices.

Purpose of the Study:

• To investigate the quantum-confined Stark effect in single cadmium selenide (CdSe) quantum dots.
• To characterize the electric field dependence of the single-dot spectrum and identify key properties of the excited states.

Main Methods:

• Studying the quantum-confined Stark effect in individual CdSe quantum dots.
• Analyzing the spectral changes of single dots under applied electric fields.
• Measuring the polarizability of excited states and Stark shifts relative to linewidth.

Main Results:

• Observed a highly polarizable excited state in CdSe quantum dots, with a volume of approximately 10^5 cubic angstroms.
• Characterized the presence of randomly oriented, time-varying local electric fields influencing the QD spectra.
• Measured Stark shifts of the lowest excited state that were more than two orders of magnitude larger than the linewidth.

Conclusions:

• The large Stark shifts and high polarizability of CdSe quantum dots suggest their potential for use in electro-optic modulation.
• Spontaneous spectral diffusion and ensemble inhomogeneous broadening are linked to the observed local electric fields.
• Single-dot spectroscopy provides critical insights into the electro-optic properties of nanomaterials.