\section*{Acknowledgements}
+I am extremely grateful for the support offered to me by many individuals during this project.
+
\begin{itemize}
\item Sergey Samarin
\item Jim Williams
In this section, we will first introduce the basic concepts needed to describe the electron spectra of solids. A short description of methods for calculating the electron spectra will be given, and the results shown by these calculations. We will then discuss the electron spectra for the near surface region of solids, compared to the ``bulk'' spectra far from the surface.
-
\subsubsection{Description of Matter in the Solid State}
\begin{itemize}
\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.
+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 an energy distribution of secondary electrons scattered from the surface. Analysis of this secondary electron distribution gives information about the interaction between primary electrons and the surface.
-\subsubsection{Electron-Surface Interactions}
+%\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.
+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 secondary electron energy distribution can be related to the probability distribution for the possible processes. Figure \ref{} shows a typical distribution of secondary electron energy, taken from \cite{}. The spectrum shows a narrow peak centred upon the primary electron energy; this corresponds to elastic scattering. At the low energy end of the spectrum, a broad maximum results from inelastic processes. Fine structure on this part of the spectrum is due to the energy structure of empty states in the sample. Fine structure due to Augur electron emission and interaction with core electrons is visible in the high energy part of the spectrum. Typically the aim of a energy resolved secondary electron spectroscopy experiment is to study the properties of secondary electrons in a small energy interval.
-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
+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 is energy increased, the threshold energies for particular processes are passed.
\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.
+\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.
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.
+The available power supplies at CAMSP 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
Although the RS-232 is relatively simple to implement, which makes it ideal for non-proprietry microprocessor applications, most modern computers no longer feature RS-232 COM ports. Although a computer with COM ports was available at CAMSP, due to the extreme unreliability of this computer, it was quickly replaced with a laptop that did not possess COM ports, and a commercial RS-232 to USB converter was used to interface with the laptop.
+
+
+\section*{Appendix C - Pressure Monitoring}
+
+Over time, it was noticed that the pressure in the chamber was variable.
+
+
+
\pagebreak
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