Study of the CVD diamond growth mechanism in the presence of a metal-based interlayer

This thesis is composed of 4 parts. Part I of the thesis is sub-sectioned into two chapters. Chapter 1 overviews diamond properties and its synthesis. Chapter 2 introduces the concept of interlayers and its use in the context of NCD growth. It states current knowledge and understanding on diamond nucleation through transition metal-based interlayers. Thus it gives a short introduction of the use of TiO2 based layers for NCD growth when nanodiamonds (NDs) are not in contact with plasma. The attention is made to introduce the reader to the concept of the Ti and TiO2 interlayer application for the diamond nucleation through the buried nanodiamonds with the Ti and TiO2 layer. Part II of this thesis is sub-sectioned into two chapters. Chapter 3 is dedicated to sample preparation and is meant to acquaint the reader to state-ofthe- art seeding technique. It compares the influence of the various parameters to the general method used to spread NDs onto surfaces during deposition. Moreover, it shows the possible pitfalls when one evaluates ND seeding density values, and compares several methods that can be used to estimate the ND seeding density value. Chapter 4 deals with preparation and characterization methods used to carry out experiments discussed further on in the thesis. Part III is sub-sectioned into two chapters. Chapter 5 describes the study of the diamond nucleation from the NDs that are buried underneath thin TiO2 layer. In this chapter ND nucleation through TiO2 are compared. The TiO2 that is used to cover NDs are prepared by three distinct synthesis techniques. Certainly not fully understood mechanism (model) of the diamond growth from buried nuclei stimulates to investigate the diamond nucleation and growth when NDs are buried underneath metal-based layers. Chapter 6 is devoted to unravel the peculiarities of the diamond growth, when NDs are covered with thin transition metal Cr coating instead of TiO2. Part IV of this thesis is dedicated to the investigation of diamond growth on thin sputter-deposited transition metal (IV-VI groups) layers. It is subsectioned into three separate and closely interconnected Chapters. Chapter 7 collates the ND seeding onto various (IV-VI groups) metals. Various aspects that possibly influence seeding density are evaluated. The effects of surface roughness and wetting properties are discussed in this regard. The van der Waals force is believed to be responsible for the adhesion of the NDs to the surface. Therefore its proportionality over the metal surfaces is evaluated. It is shown that, indeed, roughening of the surface follows the theoretically adapted model that accounts for adhesion force variation as a relation of seed density versus roughness, if the same surface is considered. However study carried out in chapter 8 hints that electrostatic interaction forces are responsible forces due to improved ND seed density on the Cr surface. No correlation due to seed density and roughness was found, thus hinting towards the idea that van der Waals forces can only be considered as important, when no strong electrostatic interaction forces are involved. On the other hand, low surface roughness variation implies that electrostatic interaction forces are the main responsible forces for the ND-tosurface interaction. Eventually, chapter 9 shows ND seeding on the plasma modified Ta surface. Contrary to the outcome displayed in chapter 8 it is shown that, despite the surface treatment with plasmas, seeding density values remain constant, thus, it is not dependent on the treatment conditions. Finally the thesis concludes with chapter 10 that summarizes the most important findings and the concluding remarks. It also gives an outlook regarding further research.

Jaar van publicatie:2015

Toegankelijkheid:Open