Oxide thin film properties

Chapter 4 focuses on the various physico-chemical properties of thin films, and in particular on their thickness dependence. It aims at bridging the gap between the well established knowledge acquired on oxide surfaces and truely two-dimensional oxides. It reviews the consequences of the reduced local environment of their atoms and of the confinement effects due to their finite thickness. It analyzes the various manifestations of structural, electronic, vibrational, ferroelectric and magnetic modifications. A special focus is put on the interaction of thin films with metal or oxide substrates, possibly leading to interfacial dislocations, electron transfer or mixing, with consequences on their chemical reactivity.

Структура межфазной границы alpha-beta в твердом растворе PdCu

In accordance with the orientation relation (110),<001>β || (111),<110> α, established by the fast electron diffraction method between ordered (β) and disordered (α) phases in the Pd – 57 at .% Cu solid solution foil , the atomic structure of the interface is modeled by molecular dynamics. It is found that the structural and dimensional mismatch is compensated by interfacial dislocations with Burgers vectors a / 2 <111> in β-phase coordinates.

Microstructure of Interfacial Basal Plane Dislocations in 4H-SiC Epilayers

As SiC power devices are being developed toward ultrahigh-voltage bipolar structures, the density of basal plane dislocations in SiC epilayers has to be minimized. In this work, a special category of basal plane dislocations, i.e. interfacial dislocations, was investigated. Their etch pits were detected at the interface and the microstructure was revealed by cross-section transmission electron microscope analysis.

Improvement of Quality of Thick 4H-SiC Epilayers

The epitaxial growth of ~250 μm thick 4H-SiC epilayers has been demanded for ultra-high-voltage power devices. We have attempted to improve the quality of thick epilayers. At the edge of wafer, stacking faults, epi-crown and interfacial dislocations could be well suppressed by controlling the distribution of growth rate. Investigation of carrier concentration depth profile revealed that increasing surface roughness increased the carrier concentration during thick epitaxial growth. Under N2-doped growth condition, memory effect by accumulation of by-products containing dopant element is also one of the reasons of the carrier concentration increasing during the growth.