Properties modification of chalcogenides by various external stimuli and the applications

Abstract

The main theme of this dissertation is to explore the possible methods to

achieve controllable and optimized modifications of the fundamental properties

of chalcogenides.

The first kind is about the structural modifications through light exposure. The

shape changes of the thin film are created when exposed to light pattern. We

then investigate the mechanisms of photo-induced surface relief formation. We

derive a generalized model to explain the spatial and temporal evolution of

photoinduced surface structure in photosensitive amorphous thin films. The model

describes these films as an incompressible viscous fluid driven by a

photoinduced pressure originating from dipole rearrangement. This derivation

requires only the polarizability, viscosity and surface tension of the

system. Using values of these physical parameters, the validity of the model is

checked by fitting to experimental data of arsenic sulfide and demonstrating good

agreement.

Another way of modifications is achieved by the doping of silver nanoparticles.

We achieve the in-situ and uniform generation of Ag nanoparticles in

chalcogenide solution using laser ablation. Ag-doped chalcogenide films are

fabricated by spin-coating the resulting solution. The prepared solution and

films are analyzed using transmission electron microscopy, dynamic light

scattering and UV-vis spectroscopy to investigate particle shape and size

distributions. Uniform doping has been achieved.

Besides, we are able to incorporate a variety of ions into chalcogenide glassy

matrices using in-situ wet chemistry processing. Various chlorides are

incorporated into chalcogenide matrices, leading to various property changes,

such as absorption and refractive indices.

In addition, we also explore modifications through photonic crystals. We use

silicon photonic crystals with angstrom surface roughness to spatially confine

the solution processed arsenic sulfide and achieve controllable modulations of

chalcogenides emission. A planar emitter array of chalcogenides is fabricated

based on this novel periodic hetero-structures of semiconductor.