Excitation and Desorption of Nano-crystalline ZrO2
EMSL Project ID
44699
Abstract
This project is focused on integrated theoretical and experimental studies of the interaction of light with nanoscale oxide materials of fundamental interest to the fields of photo-catalysis, microelectronics, sensor technology, and materials processing. Previously, we have demonstrated that highly dispersed alkaline earth oxides exhibit many different local surface structures, which allow for site-selective photo-induced processes. Self-trapping and decomposition of surface excitons are major factors driving the photo-induced structure modification in these materials. On the basis of combined theoretical and experimental research, we developed atomic scale mechanisms of photo-induced desorption of neutral atoms from MgO and CaO nano-particles. The aim of this project is to extend the concept of interacting localized excitations to a more complex material (ZrO2) and to investigate the mechanisms of laser-induced desorption of different material phases. Our previous theoretical results, obtained for a structurally similar material (HfO2), suggest that desorption of neutral oxygen atoms should be observable in ZrO2. In this project, we will model photo-physical processes for ZrO2 and use the EMSL User Facility to test our models by laser-stimulated desorption measurements of neutral O and Zr atoms.
The main challenges to be addressed by this project are: i) to predict and statistically characterize the structure of nano-crystallites and their surfaces, ii) to accurately calculate the electronic structure of surfaces and to study the possibility of electron, hole and exciton localization at surfaces, iii) to accurately predict the photon energies which may lead to desorption of oxygen and metal species, iv) to test the theoretical prediction by experimental detection of desorption and measurement of atomic kinetic energy distributions for neutral metal and neutral O-atoms.
We will use a shape-dependent thermodynamic model to investigate the relationship between nano-morphology and phase stability. By calculating the free energy of formation for tetragonal and monoclinic nano-crystals with a variety of shapes, we will study the dependence of their morphology on the prevalence of particular surface facets. We will then investigate the localization of electrons, holes and excitons at surfaces of nano-crystalline monoclinic and Y-stabilized cubic ZrO2 as well as the mechanisms and pathways to desorption of O and Zr atoms from these surfaces. We will analyze the dependence of neutral atom kinetic energy distributions on the photon energies and energy densities.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2011-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members