טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentTkach Leonid
SubjectAssembling of a Novel Setup Combined of an AFM and Confocal
Microscopes for Optical Characterization of a
Single Quantum Dot
DepartmentDepartment of Chemistry
Supervisor Professor Efrat Lifshitz
Full Thesis textFull thesis text - English Version


Abstract

This work focuses on developing and characterizing a new instrument for measuring a single quantum dot spectroscopy, which is based on a combination of an AFM with confocal microscopes. The purpose of such a combination is to measure the optical reaction of a single colloidal quantum dot (QD) to local perturbation induced on it. The optical response will be measured by the confocal microscope, while the AFM tip will be used to introduce the local perturbations.

Quantum dots are one of the most interesting systems to investigate because of their three dimensional confinement of the charge carriers, which splits the energy bands into size dependent, atomic like energy states. This gives them tunable luminescence properties.

In this work the QDs will be synthesized using the colloidal synthesis method. Colloidal quantum dots can be synthesized with a high degree of reproducibility and with a small size distribution (5-10%). This synthesis results in free standing particles in a solution capped by organic molecules (ligands). Furthermore, those ligands can be changed through well established procedures, providing the QDs with high chemical functionality. Those qualities made them candidates for many applications.

There is a great importance of single quantum dot studies.

When measuring an ensemble of QDs with standard optical methods the size distribution of the particles in the solution results in broadening of the spectra and lost of spectral information. Single dot research enables us to get rid of the size distribution broadening revealing by that previously hidden spectral information.

The work presents a quick review on quantum dots, its physics, synthesis method, and few aspects of single dot spectroscopy novelty. The instrument is explained in details, both the AFM and the confocal modules. The novelty and the reason for the choices and changes of each part from the commercial ones available on the market are explained. Preliminary results of each part and the combination of both of them together are presented.