\chapter{Overview of Theory}

I will use this section to introduce general concepts of solid state physics. The Experimental Methods section will concentrate on the theory of each method, and how this relates to the overall theory.

\begin{itemize}
	\item {\bf What a nanostructured film is, how it differs from the bulk material}
	\begin{itemize}
		\item The surface of a solid is the interface for physical/chemical interactions with it's surrounding environment
		\item The physical and chemical properties of a material are largely determined by the electron spectra at the surface
		\begin{itemize}
			\item Electron spectra is determined by the lattice potential
			\item Characterised by
			\begin{enumerate}
				\item Band structure of energy states - due to periodic lattice potential
				\item Density of States
			\end{enumerate}
			\item Surface differs from bulk due to
			\begin{enumerate}
				\item Termination of periodic lattice
				\item Adsorbed particles on surface (thin films)
				\item Relocation of lattice sites near the surface
			\end{enumerate}
			\item Band structure for Metal's vs Semi-conductors
			\begin{enumerate}
				\item Metals: 
				\item Semiconductors:
			\end{enumerate}
		\end{itemize}
		
		
	\end{itemize}
	\item {\bf Surface Plasmons}
	\begin{itemize}
		\item A collective oscillation of the electron gas in a metal
		\item Surface plasmons are confined to the surface region; 2 dimensional, differs from bulk plasmons
		\begin{itemize}
			\item In nanostructured materials, plasmons can be localised
		\end{itemize}
		\item Bohms and Ritchie
		\item Past studies at CAMSP and UWA
		\item May be caused due to excitations from
		\begin{enumerate}
			\item Electrons - refer to next section
			\item Photons
			\begin{itemize}
				\item Only light polarised in the plane of the surface can excite plasmons
				\item Need to provide an extra wavevector to ``match'' the momenta of the photon and plasmon
				\item Possibility for rough structure of metallic films to provide this wavevector
				\begin{itemize}
					\item Refer to papers on ``artificially'' blackened films
					\item Similar topic to Nikita's thesis; look at some of his references
				\end{itemize}
			\end{itemize}
		\end{enumerate}
	\end{itemize}
	\item {\bf Interactions between Electrons and Metallic Thin Films}
	\begin{enumerate}
		\item Electron-Surface Interaction
		\begin{itemize}
			\item How an incoming electron interacts with the surface as a whole
			\item Elastic reflection from potential barrier
			\item Phonon vibrations of lattice (quasi-elastic - low energy losses)
		\end{itemize}
		\item Electron-Electron Interaction
		\begin{itemize}
			\item Inelastic scattering processes determined by interaction of primary electron with the electron gas
			\item Low energy interactions (focus of low energy TCS)
			\begin{itemize}
				\item Outer electron transitions between valence and conduction band (result of interaction between primary electron and an individual bound electron)
				\item Plasmon excitation (result of interaction between incoming electron and the electron gas as a whole)
			\end{itemize}
			\item Higher energy interactions (focus of other forms of 2nd Electron Spectroscopy)
			\begin{itemize}
				\item Auger processes due to excitation of inner band electrons
				\item ``True'' secondary electrons; bound electrons given sufficient energy to leave the surface
			\end{itemize}
		\end{itemize}
		\item General structure of secondary electron energy distribution (not investigated by TCS)
		\item Mention that secondary electrons have an angular distribution (not investigated by TCS)
		
	\end{enumerate}
\end{itemize}
