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+%\title{\bf Characterisation of nanostructured thin films}
+%\author{Sam Moore\\ School of Physics, University of Western Australia}
+%\date{April 2012}
+%\maketitle
+
+\begin{center}
+ B.Sc. (Hons) Physics Project \par
+ {\bf \Large Thesis} \par
+ Samuel Moore \\
+ School of Physics, University of Western Australia \\
+ April 2012
+\end{center}
+\section*{Characterisation of Nanostructured Thin Films}
+{\bf \emph{Keywords:}} surface plasmons, nanostructures, spectroscopy, metallic-blacks \\
+{\bf \emph{Supervisers:}} W/Prof. James Williams (UWA), Prof. Sergey Samarin (UWA) \\
+
+
+%\tableofcontents
+
+\section*{Acknowledgements}
+\begin{itemize}
+ \item Sergey Samarin
+ \item Jim Williams
+ \item Paul Guagliardo
+ \item Nikita Kostylev
+ \item Workshop (for producing electron gun mount?)
+ \item Peter Hammond (?)
+\end{itemize}
+
+\section{Introduction}
+\begin{itemize}
+ \item Waffle about motivation for the project
+ \begin{itemize}
+ \item Metal-Black films may have application for ... something.
+ \begin{itemize}
+ \item Radiometer vanes, IR detectors
+ \item Number of applications where high absorbance into IR is required
+ \item These have all been studied before though.
+ \end{itemize}
+ \item The electron spectra of metal-blacks have not yet been examined.
+ \item Remarkable difference between Metal-Black films (bad vacuum) and normal metal films (UHV)
+ \begin{itemize}
+ \item No (detailed/satisfactory) explanation (that I can find...) for difference
+ \end{itemize}
+ \item Talk about plasmonic based computing? Moore's law? Applications to thin film solar cells?
+
+ \end{itemize}
+ \item Specific aims of project
+ \begin{enumerate}
+ \item Surface density of states / band structure of Black-Au films using TCS (The main aim)
+ \item Identification of plasmonic effects in Black-Au films (?) (If they even exist!)
+ \begin{itemize}
+ \item Identify plasmonic effects in Au and Ag films with Ellipsometry (this is fairly simple to do)
+ \end{itemize}
+ \item Combination of Ellipsometry and TCS to characterise thin films (not just Black-Au)
+ \begin{itemize}
+ \item Ie: How can one technique be used to support the other?
+ \end{itemize}
+ \end{enumerate}
+ \item Structure of thesis
+\end{itemize}
+
+\section{Overview of Theory}
+Summarise the literature, refer to past research etc
+
+\subsection{Electron structure of surface}
+\begin{itemize}
+ \item Overview of electron spectrum properties
+ \begin{itemize}
+ \item Density of states $n(E)$
+ \item Energy band structure $E(\vect{k})$
+ \end{itemize}
+ \item Properties of surface region
+ \begin{itemize}
+ \item Difference between potential of surface and bulk
+ \begin{itemize}
+ \item Change between the two limits in the ``near-surface'' region
+ \end{itemize}
+ \item Theoretical models for the potential, 1D vs 3D
+ \begin{itemize}
+ \item Simplest case is a step potential.
+ \item Various improvements on this model, discussed in Komolov's book.
+ \begin{itemize}
+ \item Possibly adapt CQM project to model these potentials, if I get time
+ \end{itemize}
+ \end{itemize}
+ \item Limitations of theoretical models
+ \begin{itemize}
+ \item Real surface is not a step potential
+ \item Adsorption of foreign particles onto the surface also plays a large role in determining the electron spectrum.
+ \end{itemize}
+ \end{itemize}
+ \item Main reference: Komolov "Total Current Spectroscopy"
+ \item "Solid State Physics" textbooks and "Electron Spectroscopy" textbooks
+\end{itemize}
+
+\subsection{Plasmonics}
+I really think I should actually find plasmonic effects before writing too much about them...
+\begin{itemize}
+ \item Charge density oscillations
+ \item Surface and bulk plasmons
+ \item Pines and Bohm
+ \item Review article from T.W.H Oates et al about using Ellipsometry to characterise plasmonic effects
+\end{itemize}
+
+\subsection{Metallic-Black Thin Films}
+\begin{itemize}
+ \item How they are made (bad vacuum, in air or a noble gas)
+ \begin{itemize}
+ \item If made in air, there are usually tungsten oxides present (from filament). Refer to paper by Pfund.
+ \end{itemize}
+ \item Structural difference between Black-Au and ``Shiny'' (need a better term) Au
+ \begin{itemize}
+ \item Can include electron microscopy images?
+ \item An actual photograph of a Black-Au film? Not necessary?
+ \end{itemize}
+ \item Pfund (earliest publisher, preparation and general properties)
+ \item Louis Harris (most research in 50s and 60s)
+ \begin{itemize}
+ \item L. Harris mostly did transmission spectroscopy in the far infra red (well beyond the ellipsometer and Ocean Optics spectrometer ranges)
+ \item The really crappy measurements I did with the Ocean Optics spectrometer seem to agree with these measurements
+ \begin{itemize}
+ \item L. Harris' $\lambda$ has a range of 1nm to $100\mu$m; my measurements are only to $1\mu$m
+ \item Agreement in first $1\mu$m anyway
+ \item I should probably re-do those measurements with a less crappy setup, if I actually want to use them
+ \end{itemize}
+ \item Harris related the optical properties to the structure of the film (condensor strands) via the electronic properties
+ \end{itemize}
+ \item Plasmonic effects - Deep R. Panjwani (honours thesis)
+ \begin{itemize}
+ \item Not sure if I can use an honours thesis as a reference.
+ \item Concluded that surface plasmon resonance in Black-Au film on solar cells lead to increase in solar cell efficiency
+ \item Used simulation that modelled Black-Au film as spherical balls to show E field increased by plasmon resonance
+ \begin{itemize}
+ \item Was this model appropriate? Black-Au is more ``smoke'' or ``strand'' like according to other references. Images also do not show ``blob'' like structure.
+ \end{itemize}
+ \item Need to read this reference more thoroughly
+ \end{itemize}
+\end{itemize}
+
+\section{Experimental Techniques}
+
+\subsection{Preparation of samples}
+\begin{itemize}
+ \item Black-Au - 1e-2 mbar vacuum
+ \item ``Shiny'' - 1e-6 / 1e-7
+ \item Current of ~3.5A through W wire filament spot welded onto Ta strips in turn spot welded to Mo posts
+ \item Voltage through filament is ~1 V; quote the power?
+ \item Filament isotropically coats sample with desired material.
+ \item Possibly get a curve of Au thickness estimated with Ellipsometry vs exposure time?
+ \begin{itemize}
+ \item Probably too much work and too unreliable
+ \item Maybe do it, but only use 2/3 data points
+ \item Low priority
+ \end{itemize}
+\end{itemize}
+
+\subsection{Total Current Spectroscopy}
+\begin{itemize}
+ \item Overview of technique
+ \begin{itemize}
+ \item Low energy beam of electrons incident on sample
+ \item Measure slope of resulting I-V curve
+ \item Relate to density of states and electron band structure (Komolov chapter 3.2)
+ \end{itemize}
+ \item Description of apparatus
+ \begin{itemize}
+ \item Electron gun and filament
+ \item Electron gun control box
+ \item ADC/DAC control box and data processing
+ \end{itemize}
+ \item Photographs vs Diagrams
+ \begin{itemize}
+ \item Prefer diagrams to photographs
+ \item Especially for the ADC/DAC control box circuit. Because it looks like a horrible mess.
+ \end{itemize}
+\end{itemize}
+
+\subsection{Ellipsometry and Transmission Spectroscopy}
+\begin{itemize}
+ \item Overview of techniques
+ \item Description of apparatus (use VASE manual)
+ \item Ocean Optics spectrometer? Usable?
+ \item Application of Ellipsometry to finding plasmonic effects
+ \begin{itemize}
+ \item Surface plasmons = E oscillation parallel to surface $\implies$ only $p$ component of light excites plasmons
+ \end{itemize}
+\end{itemize}
+
+\section{Experimental Results and Discussion}
+\subsection{TCS Measurements}
+\begin{itemize}
+ \item TCS for Si
+ \item TCS for Si + Au
+ \item TCS for Si + Black-Au
+ \item Affect of preparation pressure on TCS for Si + Black-Au
+ \item Repeat for Si + Ag and Si + Black-Ag (?)
+\end{itemize}
+
+\subsection{Ellipsometric Measurements}
+\begin{itemize}
+ \item Ellipsometry to estimate thickness of SiO2 layer on Si
+ \item Estimate thickness of Au/Ag on Si+SiO2
+ \item Ellipsometric measurements of Si+Black-Au/Ag
+ \begin{itemize}
+ \item Modelling procedures to characterise Black-Au/Ag
+ \end{itemize}
+ \item Ellipsometric measurements of Glass+Black-Au/Ag (?)
+ \item Transmission spectra of Glass+Black-Au/Ag from earlier in year (?)
+\end{itemize}
+
+\section{Achievements}
+\begin{itemize}
+ \item Deposition of thin films of Au and Black-Au in vacuum chamber
+ \item Ellipsometric and spectroscopic measurements on these films
+ \item Repurpose vacuum chamber for sample preparation and TCS experiments
+ \item Designed and built electronics for TCS experiments
+ \begin{itemize}
+ \item Electron gun control box
+ \item ADC/DAC box
+ \end{itemize}
+ \item Wrote software for data aquisition and data processing
+\end{itemize}
+
+\section{General notes}
+\subsection{TCS}
+\begin{itemize}
+ \item Optimise setup of gun
+ \begin{itemize}
+ \item Emission current. How much does it vary, why does it vary.
+ \item Why does Is/Ie curve shift with successive sweeps? Does sweep modify sample's surface?
+ \item Is sample holder acceptable? Are ceramic washers accumulating charge?
+ \item How do I tell when the setup is optimised...
+ ``The setup was optimised by looking for an S curve''. Very scientific.
+ \item The gun was focused on the phosphor screen... and then I turned it around, changing the distance from the gun to the sample. Brilliant.
+ \end{itemize}
+ \item Obtain TCS spectra for Si that compares well with literature
+ \begin{itemize}
+ \item How to relate TCS spectrum to $n(E)$ and $E(\vect{k})$
+ \end{itemize}
+ \item Prepare Au films, obtain TCS spectra that compares with literature
+ \item Obtain TCS spectra of Black-Au films
+ \item Use results to compare properties of films with results from other methods in the literature
+ \item Uncertainties
+ \begin{itemize}
+ \item Oscilloscope measurements of inputs to ADC channels under controlled conditions
+ \begin{itemize}
+ \item Expected values are +/-3mV due to ADC channel, +/-300mV due to 610B, +/-1mV due to 602
+ \item 610B and 602 will probably be worse because they are ancient
+ \item There is about 200mV of noise between the GND of the ADC box and the electron control box.
+ \item How to reduce ground loops? Not much I can do. Rack is now also grounded to water pipe, but this doesn't seem to make a difference.
+ \end{itemize}
+ \item Stupid 50Hz AC noise... how to reduce with filters and/or averaging
+ \end{itemize}
+ \item Create circuit diagrams for Electron gun circuit
+ \item Create circuit diagrams for ADC/DAC box
+ \begin{itemize}
+ \item Simulate behaviour of circuit
+ \item Use of instrumentation amplifier on ADC5 to make off-ground measurements
+ \item Use of low pass filter on ADC5
+ \end{itemize}
+ \item Include references to all datasheets, etc
+ \item Vacuum chamber
+ \begin{itemize}
+ \item Base pressure with rotary pump? Was 1e-3 after 30 minutes at start of year, but probably introduced leaks since then
+ \item Lowest pressure achieved with turbo pump is 1.1e-7 mbar as of 25/07.
+ \item Viton gaskets on some seals. Copper on other.
+ \item Flanges:
+ \begin{enumerate}
+ \item View window (large, view of sample \& sputtering filaments)
+ \item Rotation manipulator \& sample mount
+ \item Pump inlet
+ \item Filament flanges 1 (used earlier in year, not anymore) and 2
+ \item Inlet with leak valve (for introducing gases into chamber)
+ \item Vent valve on turbo pump
+ \item Electron gun flange
+ \item View window (small, view of back of electron gun)
+ \end{enumerate}
+ \end{itemize}
+\end{itemize}
+
+\pagebreak
+\bibliographystyle{unsrt}
+\bibliography{thesis}
+
+\end{document}
+
git.ucc.asn.au / matches / honours.git / blobdiff
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