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Department Library

### 2020

Abstract

Our team is focused on testing mirrors and other phenomena in the Extreme Ultraviolet (XUV). For this, we need a way to select wavelengths used for testing. A grazing incidence monochromator is one way to achieve this goal, and so one is installed in our system. The focus of this project was to automate the positioning of the monochromator and thus automate wavelength selection. Over the course of this project, a system was designed to attach a motor to the micrometer knob controlling the position of the monochromator. Once designed, the system was constructed and installed in the overall system. The system was then calibrated to correlate motor position to wavelength selected. The motor accurately positions the micrometer knob to within 0.001mm, which translates to within 0.008nm of the desired wavelength, and the support system meets all design goals.

### 2017

Margaret Miles (Masters Thesis, December 2017, Advisor: Steve Turley )

Abstract

The aluminum oxide growth rate for aluminum protected with 2.4 nm of aluminum fluoride has been determined. We show that a 2.4 nm aluminum fluoride layer does not prevent aluminum from oxidation but does significantly retard the oxide growth – decreasing the oxide layer thickness from 1 nm in less than an hour to 0.9 nm over 116 hours. Additionally, the optical constants for aluminum oxide growing under an aluminum fluoride barrier layer have been determined – showing an increase in absorption at high energies for Al2O3 forming at room temperature as compared to highly ordered Al2O3 formed at high temperatures.

Spencer Thevenin (Senior Thesis, April 2017, Advisor: Steve Turley )

Abstract

If the scale of surface roughness is on the order of the wavelength of incident light, traditional optics methods like ray tracing and physical optics fail to adequately model reflectance. In this project, boundary integral techniques were chosen because they provide direct solutions only limited by computer memory. Discretizing Maxwell's equations across a surface yields an $Ax=b$ matrix equation relating the surface current to electric field over a net of points. Reflectance calculations for transverse-magnetic (TM) waves on a perfect conductor in two dimensions are analyzed in depth to model the effects of scattering from surface roughness. Root mean square (rms) furface roughness more than a hundredth the wavelength of the incident beam is noticeable and anything larger than a tenth the wavelength dominates the reflectance. These calculations allow for comparison with previous approaches --such as the scalar correction factors of Debye-Waller -- at various spatial frequencies. The Debye-Waller models the smaller roughness but loses precision as roughness increases. The effects of spatial frequencies are also analyzed are compared to the current work of Stearn in showing additional surface parameters affecting roughness. The results of altering spatial frequency supports the work of stern suggesting additional parameters like spatial frequency are factors that affect overall reflectance. Optimizing the calculation through generating and solving the matrix equation are analyzed. Nonsingular, off-diagonal elements of the relation matrix are relatively slow to calculate in the generation process. A method using the multipole expansion is theorized to combat this inefficiency.

### 2015

Benjamin Smith (Senior Thesis, August 2015, Advisor: Steve Turley )

Abstract

Abstract Text: The optical constants for yttrium oxide are presented for the 8.5-31 nm range. \mbox{Y}_{2}\mbox{O}_{3} thin films have shown promise as a non-volatile reflector for EUV light at \lambda 30.4 nm. Samples were prepared using e-beam vapor deposition and annealed at 800 K and 825 K. Optical constants were measured using reflectance methods at the Advanced Light Source. Measured values are compared to similar data taken in 2009 as well as calculations from the CXRO atomic scattering factors. I also present an experimental system to produce and measure the reflectance of aluminum films in the VUV range of 70-95 nm with applications in space-based astrophysical research. A hollow cathode He+ plasma discharge source was constructed and attached to a recommissioned monochromator and a variable-angle reflectometer. I provide some preliminary spectral and spatial characterizations of the UV light.

### 2014

Joshua Marx (Senior Thesis, April 2014, Advisor: Steve Turley )

Abstract

I used extreme ultraviolet light to find the surface roughness of three Uranium Oxide thin films of approximate thicknesses 140 nm, 114 nm, and 40-45 nm. The wafers were first scanned to measure the non-specular reflectance of each sample. I combined the scans with the same angle of incidence, and then normalized the combined data to calculate the reflectance per unit angle using diffuse reflection. Next, I compared the data to Huygens' and geometrical optics calculations to estimate surface RMS height and the spatial frequency distribution. I have also compared the roughness height and frequency distribution to measurements taken on the SEM. By comparing our non-specular curves to geometrical optics, Huygens' calculations and physical measurements we are able to create a model accurate enough to describe the non-specular scattering from surfaces with roughness having spatial frequencies much less than one over the wavelength. Our research group hopes to be able to use this data make smoother samples in the future and find new and better ways to model thin film surfaces.

Cody Petrie (Senior Thesis, August 2014, Advisor: Steve Turley )

Abstract

We have developed a method to measure the roughness of thin films using extreme ultraviolet (EUV) light. This method is more sensitive to roughness with characteristic features on the length scale of a wavelength of light (a few nm) than existing methods like atomic force microscopy (AFM). We have used EUV reflection, geometrical optics (GO), and physical optics (PO) calcula- tions to determine the roughness of UOx thin films. The two samples we have used had thicknesses of 44 and 412 nm respectively. We have generated random rough surface models and used PO to calculate the reflection that we should see from these surfaces. These calculations were compared to reflection measurements taken on each sample at the Advanced Light Source to determine the roughness of each sample. We were not able to fit PO calculations to the 44 nm data, but were able to get some insight into the topography of the surface with GO. Four measurements were taken on the 412 nm sample at different incident angles and with different wavelengths of EUV light. We modeled the surface with the rms roughness height and the width of the Gaussian packet of spatial frequencies. We determined the rms height to be 0.78±0.15 nm and the width of the Gaussian packet to be 8.3 × 10−5 ± 2.7 × 10−5 nm−1. For the 412 nm sample the AFM determined the rms roughness heights to be 9.39 nm. This shows that our method has potential to provide more reso- lution than AFM in measuring surface roughness. This also demonstrates that optical techniques provide a potential means for measuring roughness when other methods are inaccurate.

Liz Scott (Senior Thesis, August 2014, Advisor: Steve Turley )

Abstract

The index of refraction of Y2O3 was measured in the extreme ultraviolet region of 2 nm to 49 nm. Using these measurements, we have demonstrated the potential use of Y2O3 as a reflective surface in the extreme ultraviolet range. The primary sample studied was grown using radio frequency sputtering and annealed at 800 K for 9 hours. Measurements were made at the Advanced Light Source at the Lawrence Berkeley National Laboratory using beamline 6.3.2. This data represents an improvement over the previous data calculated using atomic scattering factors and shows that the previous work done at BYU, that an Al/Y2O3 multilayer mirror should be effective at maximizing reflectance at 30.4 nm is indeed correct.

### 2012

Gregory Hart (Senior Thesis, August 2012, Advisor: Steve Turley )

Abstract

We quantitatively characterized the effect surface roughness has on extreme ultraviolet radiation. This was done by taking the ratio of the reflectance of a surface with random roughness and the reflectance from a perfectly smooth surface of the same composition and size. The reflectance was calculated by numerically solving the exact integral equations for the electric and magnetic fields for s polarization. The surfaces had low spatial-frequency noise in one direction and were invariant in the other. The reflectance for the rough surface was averaged from many different random surfaces. In order to determine the parameters that affect this ratio, we varied angle of incidence, rms height of the roughness, thickness of the substance, real and imaginary parts of the index of reflection, and frequency cut-off for the random noise on the surface. We determined that in the extreme ultraviolet only the angle and rms height mattered. We did a fit to create a correction factor and compared it to Debye-Waller and Nevot-Croce correction factors.

Zephne Vaterlaus (Senior Thesis, April 2012, Advisor: Steve Turley )

Abstract

### 2011

Samuel Keller (Senior Thesis, December 2011, Advisor: Steve Turley )

Abstract

Alex Rockwood (Senior Thesis, April 2011, Advisor: Steve Turley )

Abstract

The reflectance of light off a surface can be significantly reduced by surface roughness when the height of the roughness is close to a wavelength. Our group is interested in extreme ultraviolet of wavelength of 1nm to 100nm. I used an atomic force microscope (AFM) to measure the height of surfaces with different roughness. The surfaces were of sputtered yttrium oxide with roughness heights ranging from less then a tenth of a wavelength to two wavelengths. From the AFM measurement I calculated the power spectral density (PSD) and the root mean square (rms) roughness height. Using this, and the phase of the Fourier transform (FT), I recreated surfaces that have the same characteristics of the original surfaces. Then I calculated the reflection using the physical optics approximation of many similar surfaces to see how reflection is decreased due to different roughness and different wavelengths. From this I produced a general formula relating reflection reduction to AFM surface characteristics.

### 2010

Alex Rockwood (Senior Thesis, April 2010, Advisor: Steve Turley )

Abstract

Anthony Willey (Senior Thesis, October 2010, Advisor: Steve Turley )

Abstract

In an effort to get higher EUV intensity, a hollow cathode plasma light source was wrapped in a solenoid to create a magnetic eld in the plasma region. Confining the plasma toward the center of the source was expected to increase the intensity of the He II 304Å and He 584Å lines. An applied magnetic field of about 150 gauss increased intensity of the 584Å line, but decreased intensity at the 304Å line.

### 2009

Joseph Muhlestein (Senior Thesis, February 2009, Advisor: Steve Turley )

Abstract

The index of refraction of Y<sub>2</sub>O<sub>3</sub> has been measured in the extreme ultraviolet region of 5 nm to 30 nm. These measurements demonstrate the potential use of Y<sub>2</sub>O<sub>3</sub> as a reflective material in the extreme ultraviolet. Y<sub>2</sub>O<sub>3</sub> is also a very stable material in vacuum and in atmosphere/ which further distinguishes it as a practical choice for an EUV mirror. The sample studied was grown using electron beam evaporation and later heated for 29 hours at 623 °C. This represents the first experimental measurement of Y<sub>2</sub>O<sub>3</sub> in this wavelength range and represents an improvement over previous data calculated using atomic scattering factors. Measurements were taken at the Advanced Light Source at the Lawrence Berkeley National Laboratory using Beamline 6.3.2. Previous work done at BYU has shown that an Al/Y<sub>2</sub>O<sub>3</sub> multilayer mirror should be effective at maximizing reflectance at 30.4 nm and minimizing reflectance at 58.4 nm, a useful combination for detecting the relatively weak 30.4 nm line of He<sup>+</sup> over the stronger 58.4 nm line of neutral He.

### 2008

W. Todd Doughty (Senior Thesis, August 2008, Advisor: Steve Turley )

Abstract

I modeled the re ectance from rough conductive surfaces for tranverse magnetic (TM) and tranverse electric (TE) polarization. The Nystrom technique was applied in order to solve the Electric Field Integral Equation (EFIE) in the TM case and the Magnetic Field Integral Equation (MFIE) in the TE case. We studied 2.4 million sample surfaces with varied roughness heights and frequencies from various incident angles and compared the results to the predictions of the Debye-Waller Factor (DWF). As predicted, the attenuation is directly correlated with the qh factor, but di ers from the DWF in both form and magnitude. There was also a signi cant dependance on both spatial frequency and polarization. We developed our own model by tting the results to a cubic correction function. In addition to the predicted quadratic term, our simulations showed signi cant linear and cubic terms in the roughness correction function.

### 2007

Abstract

Researchers at Wayne State’s Smart Sensors and Integrated Microsystems program are developing wireless retinal implants, but worry that these implants might be depositing aluminum into the soft surrounding tissue. Laser-Induced Breakdown Spectroscopy (LIBS) is an excellent tool for trace elemental analysis and was therefore studied as a method of detecting small amounts of aluminum in tissue. Tissue was modeled using 2% agarose gelatin and doped using nanoparticle aluminum oxide solution. LIBS was effective at detecting very low concentrations of aluminum in this model biological tissue. A calibration curve created from standardized samples with well-known Al concentrations was made and determined to be linear. A limit of detection, extrapolated from the calibration curve, was found to be less than 1 ppm. Also studied were rates of false negatives and false positives for a much more realistic testing methodology: few v accumulations on a low aluminum concentration sample. For a 2 ppm aluminum sample, 45% of the measurements gave false negatives for a single accumulation measurement, but only 20% gave false negatives for a two accumulation measurement. The low limit of detection and relative sensitivity at few accumulations show that LIBS is an excellent tool for detecting aluminum in a tissue stimulant. This method should be further investigated for use as an in vivo analysis tool.

Amy Grigg (Honors Thesis, August 2007, Advisor: Steve Turley )

Abstract

This thesis examines a method for taking oxidation gradients into consider- ation when determining optical constants from re ectance and transmission measurements. The oxidation gradients were measured by two techniques that use x-ray photoelectron spectroscopy: sputtering, where data are taken at various depths in the sample after removing the surface by sputtering; and variable angle scans, where depth information is obtained by placing the detec- tor at several angles. X-ray photoelectron spectroscopy sputtering was found to give better results for our purposes. This method resulted in very good ts of theoretical data.

Elise Martin (Senior Thesis, April 2007, Advisor: Steve Turley )

Abstract

There are several traditional methods of accounting for the way that the roughness of a surface changes how light reflects. This paper introduces a new method based on arbitrarily exact solutions of Maxwell’s equations solved computationally for reflectance from rough surfaces. This method leads to a correction factor for the changed reflectance and is compared to the oft-used Debye-Waller factor. Where the Debye-Waller factor contains only a quadratic factor in the exponential, the computational fitting of reflectance data demonstrates the need for cubic and linear terms in addition to a quadratic term.

Marie Stellman (Senior Thesis, August 2007, Advisor: Steve Turley )

Abstract

At Brigham Young University optical constants for thin films are calculated by reflectance versus angle of incidence measurements using a reflectometer. This project focuses on the reflectometer’s automation by a computer and the generation of documentation for that program.

### 2006

Jedediah Edward Jensen Johnson (Masters Thesis, December 2006, Advisor: Steve Turley )

Abstract

Electromagnetic scattering from a rough two dimensional homogeneous scatterer was computationally modeled. The scatterer is intended to simulate re- flection from a two interface multilayer. The rough scatterer was created from Gaussian random points centered about an ideal interface. The points were connected with a third order spline interpolant which accounts for correlation between neighboring surface atoms. The scalar electric field integral equation (EFIE) and magnetic field integral equation (MFIE) were solved using the Nystrom method to obtain the reflected intensity as a function of observation angle. Verification of the accuracy of the code was obtained by means of comparison with well-known analytic solutions and approximations. The predicted Nevot-Croce factor drop in reflectance was found to be in general agreement with the computed decrease in reflectance due to surface roughness. However, an angle dependent difference was also noticed, indicating the Nevot-Croce factor might need revision. The code is being modified to run on a supercomputing cluster where longer, more realistic surfaces can be analyzed to determine whether an improved roughness correction factor is needed.

### 2005

Nicole Brimhall (Farnsworth) (Honors Thesis, January 2005, Advisor: Steve Turley )

Abstract

Jeffery Hallstrom (Capstone, August 2005, Advisor: Steve Turley )

Abstract

The purpose of this guide is to help the user understand and effectively use the Mirror Designer program. Mirror Designer is a Java-based computer program that uses a genetic algorithm to design multilayer mirrors that optimize reflectance at wavelengths specified by the user. The genetic algorithm used by Mirror Designer is described, as well as the method used to calculate the reflectivity of multilayer mirrors.

### 2004

Marie Urry (Senior Thesis, April 2004, Advisor: Steve Turley )

Abstract

n/a

### 2003

Danelle Elaine Brown (Senior Thesis, April 2003, Advisor: Steve Turley )

Abstract

Elke Jackson (Senior Thesis, April 2003, Advisor: Steve Turley )

Abstract

Matthew McDonald (Senior Thesis, August 2003, Advisor: Steve Turley )

Abstract

### 2002

Ryan Robert Anderson (Senior Thesis, April 2002, Advisor: Steve Turley )

Abstract

Shannon Lunt (Masters Thesis, December 2002, Advisor: Steve Turley )

Abstract

We have determined the indices of refraction of reactively sputtered thin film UO2 for the first time below 300 A. Our measured indices for UO2 differ from those calculated by atomic scattering factors by about 2. This results in UO2 thin films with an oxide on top reflecting as well as or better than theoretical calculations for UO2 thin films. We report the measured indices of refraction for UO2 and the oxide that formed on top as well as fabrication and characterization techniques used.

Fabian Thomas Walter (Senior Thesis, August 2002, Advisor: Steve Turley )

Abstract

### 2001

David Paul Balogh (Masters Thesis, April 2001, Advisor: Steve Turley )

Abstract

A web-based version of a general education physical science course has been developed and implemented at Brigham Young University. Student attitudes, performance, and website interactions were measured during the initial pilot course in Spring 2000 and the second implementation which followed in Fall semester 2000. Control groups consisted of traditional lecture-based sections with enrollments exceeding 300 students. The web-based experimental sections had enrollments of 25 to 50 students. Results of an analysis of the Fall 2000 data is presented here. Students did not use the web pages to the degree that was intended by course architects, thus limiting he effect that the online learning environment may have had on attitude and performance. There was no statistical difference in performance between control and experimental groups, however there were observed meaningful differences. There is no evidence for self-selection among students in the web-based section. The web-based course was rated slightly lower by students than the traditional sections, an artifact of technical problems encountered early in the course. An analysis of learning style and orientation showed no correlation with gathered data, suggesting that the web-based course is suited for a wide variety of learning styles.

Matthew Byron Crookston (Senior Thesis, April 2001, Advisor: Steve Turley )

Abstract

Cynthia Mills (Honors Thesis, March 2001, Advisor: Steve Turley )

Abstract

### 2000

Derek Hullinger (Masters Thesis, April 2000, Advisor: Steve Turley )

Abstract

Strong sources of coherent and incoherent short wavelength radiation have been pursued for a variety of reasons. We have focused our efforts on one possible scheme for producing radiation in the soft x-ray regime – that of a capillary discharge with a water transmission line driver. Progress has been made in developing a capillary discharge sift x-ray source and in studying the discharge parameters and plasma evolution to better understand the optimum conditions for producing intense radiation. My work toward these goals fall into three main categories: modifications and enhancements, new designs and feasibility studies, and measurement of the current. I discovered that the electric field inside the case approaches the breakdown field for air (3 x 106 V/m) for the high charging voltages. I calibrated a new adjustable transmission line designed to regulate the breakdown voltage of the switch leading the capillary. Work directly relating to the spectrograph includes determining the film positions at which lines lie on the Rowland circle and as a result are in best focus, and determining the observable wavelengths from each grating and the dispersions expected in the spectra. Work on the microchannel plate collimator involved measuring the MCP parameters and determining the angle of half transmission and of zero transmission. It also involved calculating an approximate intensity reduction of 96% and designing of a mount. To produce longer current pulses, I designed two extensions for the transmission line. I monitored the current when the shorter extension was in place. Finally, I determined how the current evolves with time, measured the peak current through the capillary, and inferred the capillary resistance. These results will enable others to determine in more depth the discharge parameters and conditions favorable for producing an efficient EUV source.

David Toone Oliphant (Masters Thesis, December 2000, Advisor: Steve Turley )

Abstract

In order to understand discrepancies between calculated and measured values of reflectance for the IMAGE mirrors a characterization of the top layer of uranium was undertaken. To better understand this uranium oxide cap, single film layers of uranium were also studied. Physical and chemical properties of samples were studied with atomic force microscopy, X ray diffraction, X ray photoelectron spectroscopy, transmission electron microscopy and ellipsometry. It was determined that most of the uranium oxide cap is composed of uranium dioxide. However, there is a surface layer different than the pure dioxide. This layer is likely a hydroxide or hyperstoichiometric uranium oxide or both. It was also found that the bottom of the uranium oxide cap diffused into the amorphous silicon layer beneath it. Not far into the underlying silicon layer the uranium was found to stop oxidizing. A study of the oxidation rate of sputtered uranium thin films was also conducted. It showed a rate that varied with time, dissimilar to published uranium oxidation rates for bulk samples. In addition, a new method for analyzing X ray diffraction data was also formulated.

### 1999

Abstract

Shannon Lunt (Honors Thesis, March 1999, Advisor: Steve Turley )

Abstract

### 1998

Christopher Blair Crawford (Masters Thesis, April 1998, Advisor: Steve Turley )

Abstract

The discharge plasma in a 2 mm diameter x 2 cm long capillary was analyzed spectroscopically using a 1 m grazing incidence spectrograph with the purpose of searching for amplified stimulated emission (ASE). The electron temperature was determined to be Te ´20+30 eV. With the capillary under vacuum, CIII, CIV, OIII, OIV, OV, and OVI lines were observed from ablation of the polyacetal walls. With argon present in the capillary there were also ArV, ArVI, ArVII, and ArVIII lines were also observed. The line intensities were strongest with 100 mTorr of argon in the capillary, the line intensities increased strongly with higher voltage. Investigations were also made on whether it includes a preionization discharge, and changing the size of the capillary. It was concluded that it may be possible to observe ASE is the charging voltage of the Marx generator is increased from 40 kV to 60 kV. Recommendations are given on the improvement of the Marx generator, that it will be capable of producing such voltages.

David Oliphant (Senior Thesis, August 1998, Advisor: Steve Turley )

Abstract

### 1997

Renee George (Honors Thesis, February 1997, Advisor: Steve Turley )

Abstract