Date of Award

5-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Materials Science and Engineering

Advisor

Richardson, Kathleen

Committee Member

Kornev , Konstantin

Committee Member

Luzinov , Igor

Committee Member

Dussauze , Marc

Abstract

The results in this thesis are from our efforts to modify the optical properties of solution-derived chalcogenide glass films by the incorporation of nanomaterials. First, the composition Ge23Sb7S70 was selected as the appropriate glass matrix for testing because solution-derived films of this composition have been well-studied in our group. Additionally, this composition was found to be less sensitive to certain processing parameters than As2S3, another well-studied, candidate chalcogenide glass composition, making Ge23Sb7S70 more suitable for the addition of nanomaterials. Optimization of film process parameters was performed to obtain high-quality films appropriate for doping with nanomaterials. This consisted of determining the maximum solubility of glass in propylamine solvent to obtain films of adequate thickness, as well as optimizing the water content in the propylamine to minimize surface roughness and cracking. Two classes of nanomaterials were used to investigate the principles of doped films, spherical metallic nanoparticles (MNPs), and spherical semiconductor nanoparticles, also known as quantum dots (QDs). Gold was the particular type of MNP used, and is characterized by its surface plasmon resonance (SPR) absorption band, which is tunable and environment sensitive, and leads to interesting properties such as magneto-optic effects. Two types of QDs were used, CdSe and PbS. QDs are widely known for their high photostability and luminescence, which is tunable by varying the size of the QD. CdSe exhibits luminescence in the visible spectral region, while PbS emits in the near-infrared (NIR).
With Au nanoparticles, experiments were performed to determine the maximum nanoparticle concentration in the glass solution by utilizing UV-vis-NIR spectroscopy. Films were then deposited and characterized by their absorption spectra. In the case of QDs, solutions were not stable for long enough periods of time, so only the films deposited from the solutions could be analyzed. UV-vis-NIR spectroscopy and photoluminescence measurements were used to observe the intensity and location of the characteristic absorption and luminescence bands of the QDs. Quantum yield and luminescence lifetime were used to quantitatively characterize the behavior of the QDs in different environments when possible. Different organic ligands on the surface of the QDs were tested and compared to evaluate their effect on the behavior of the QD. The results show that small amounts of Au MNPs can be dispersed in a chalcogenide glass solution with minimal aggregation, as quantified by the absorption spectra. Comparison of the optical behavior of the films to that of the solutions showed that the concentration of Au MNPs was too low to observe the characteristic SPR band. The results of the QD testing show that luminescence can be observed from a deposited film, and that the behavior of the QDs, characterized by quantum yield and lifetime, varies greatly in different environments. Furthermore, it was found that different capping agents led to different behavior of the QDs in the glass solution, affecting the properties of the deposited film.

Share

COinS