Automatic commit. Tue Aug 14 00:00:03 WST 2012

[matches/honours.git] / thesis / thesis.tex

diff --git a/thesis/thesis.tex b/thesis/thesis.tex
index abb8d05..a008234 100644 (file)
--- a/thesis/thesis.tex
+++ b/thesis/thesis.tex
@@ -74,6 +74,7 @@
 %\tableofcontents
 
 \section*{Acknowledgements}
+
 \begin{itemize}
        \item Sergey Samarin
        \item Jim Williams
@@ -119,7 +120,14 @@
 \section{Overview of Theory}
 Summarise the literature, refer to past research etc
 
-\subsection{Electron Spectra of a Surface}
+\subsection{Electron Spectra of Solids and Surface}
+
+
+
+
+
+
+
 \begin{itemize}
        \item Description of the near surface region
        \begin{itemize}
@@ -231,7 +239,45 @@ I really think I should actually find plasmonic effects before writing too much
 
 \section{Experimental Techniques}
 
-\subsection{Preparation of samples}
+\subsection{Secondary Electron Spectroscopy}
+
+Secondary Electron Spectroscopy encompasses a large group of techniques used for studying the electron spectra of surfaces and solids. In these methods a beam of primary electrons is directed at the surface of a solid. The interactions between primary electrons and the surface give rise to a flux of secondary electrons scattered from the surface. Analysis of this secondary electron flux gives information about the interaction between primary electrons and the surface.
+
+\subsubsection{Electron-Surface Interactions}
+
+
+\subsubsection{Methods of Secondary Electron Spectroscopy}
+
+Energy-resolved methods of Secondary Electron Spectroscopy are based upon observation of the secondary electron energy distribution at a fixed primary electron energy. The primary electron energy determines which processes are possible, whilst the observed distribution can be related to the probability distribution for the possible processes.
+
+In contrast to Energy-resolved methods, Total Current (or Yield) methods are based on observation of the total current of secondary electrons as a function of primary electron energy. As the primary electron energy is increased, the threshold energies for particular processes are passed. This 
+
+Both Energy-resolved and Total Current methods can be performed 
+
+\subsection{Total Current Secondary Electron Spectroscopy}
+
+Figure \ref{} shows a simplified schematic for the Total Current Spectroscopy experiments conducted during this study. Electrons are emitted from a cathode held at negative potential relative to the target. The electron beam is focused and accelerated onto the target by the electric field of an electron gun. A detector is used to measure the total current passing through the target.
+
+\subsubsection{Electron Optics}
+
+The electron gun used for this experiment was repurposed from an old Cathode-Ray Oscilloscope (CRO). Figure \ref{} shows a simplified diagram of the electron gun, whilst Figure \ref{} shows a photograph of the gun. 
+
+
+
+The full circuit diagram for the electron gun control circuit is shown in Appendix A.
+
+\subsubsection{Automatic Data Acquisition}
+
+In order to collect data on the large number of planned samples for the study, some form of automation was required. The automated system needed to be able to incrementally set the initial energy by controlling a power supply, and record the total current measured by an ammeter.
+
+The available power supplies at CAMSP only featured analogue inputs for external control. This meant that a Digital to Analogue Convertor (DAC) card was needed to interface between the control computer and the power supply. In addition, the available instruments for current measurement at CAMSP produced analogue outputs. As a result, Analogue to Digital Convertors (ADCs) would be required to automate the recording of total current.
+
+Although an external DAC/ADC box was already available for these purposes, initial tests showed that the ADCs on the box did not function. The decision was made to design and construct a custom DAC/ADC box, rather than wait up to two months for a commercial box to arrive. The design of the custom DAC/ADC box is discussed in detail in Appendix B, and the software written for the on-board microprocessor and the controlling computer are presented in Appendix C.
+
+
+
+
+
 \begin{itemize}
        \item Black-Au - 1e-2 mbar vacuum
        \item ``Shiny'' - 1e-6 / 1e-7
@@ -246,9 +292,9 @@ I really think I should actually find plasmonic effects before writing too much
        \end{itemize}
 \end{itemize}
 
-\subsection{Secondary Electron Spectroscopy}
-
+\subsection{Electron Spectroscopy}
 
+Secondary electron spectroscopy methods are a broad class of methods which investigate surface electron spectra through observing processes in which the surface electrons participate directly \cite{komolov}. 
 
 Total Current Spectroscopy is a group of electron secondary