\chapter{Introduction}

% TODO: Broad general sweeping statements about thin films

Motivation:
\begin{itemize}
	\item The properties of solids can be understood in terms of an infinite periodic lattice
	\item In reality, every solid must have a finite spatial extent. The 
	\item Thin films can have extremely complicated and interesting properties. 
	\item The characterisation of thin films is important research in electronics as the surface to volume ratio increases.
	\item Most recent research has been into completely new technologies which exploit phenomena (
	\item Somehow link to metallic-black films (?)
\end{itemize}

So called metallic-black films are the result of deposition of metal elements at a relatively high pressure (of the order of $10^{-2}$ mbar). The films are named due to their high absorbance at visible wavelengths; they appear black to the naked eye. There is a remarkable contrast between such films and films deposited under low pressure (less than $10^{-6}$mbar), which are typically highly reflective and brightly coloured.

% First mentions and early research; Pfund
This phenomenom has been known since the early 20th century, with the first papers on the subject published by Pfund in the 1930s \cite{pfund1930}, \cite{pfund1933}. Pfund established the conditions for formation of metallic-blacks \cite{pfund1930}, and showed that the transmission spectrum of metallic black films is almost zero in visible wavelengths, but increases to a plateau in the far infrared \cite{pfund1933}. More extensive research on the structural and optical properties of these films by Louis Harris and others during the 1940s and 1950s \cite{harris1948}, \cite{harris1952}, \cite{harris1953}. 

% Research by Harris concluding ``condensor'' like structure
Harris et al. have produced experimental results of the transmission of metallic-black films from visible wavelengths to the far-infrared \cite{}. By modelling the film as a layer of metallic strands, acting as ``condensors'', Harris et al. arrived at an expression for the electron relaxation time of [element]-black \cite{}, leading to a a transmission spectrum in good agreement with experimental results.

% Mckenzie
Mckenzie has established that the presence of oxygen effects the optical and electrical properties of metallic-blacks \cite{mckenzie2006}.


% More recent research
More recently, it was shown that Au-black coatings increased the efficiency of thin film solar cells \cite{}. In this study, a simulation approximating an Au-black film as a layer of semi-spherical structures showed plasmonic behaviour which lead to an increase in electric field behind the film. 


% Artificially ``blackened'' thin films
Metallic-black films have proven useful in applications requiring efficient absorption of light, including the. Recently there has been interest in artificial ``blackening'' of metal surfaces in ways which simplify the characterisation of the surfaces for practical applications. 

Sondergaard et al. have produced metallic-black surfaces capable of suporting surface plasmon modes \cite{sondergaard2012}. These films exhibit similar optical properties to the previously considered ``evaporated'' metallic-black surfaces. 

% What I will be doing with metallic-black films
This project will employ several techniques, including:Total Current Specroscopy; Ellipsometry and Optical Spectroscopy to investigate the difference between metallic films deposited at low pressure, and high pressure (metallic-blacks). 

