Doctorate in Applied and Engineering Physics  

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Thesis Proposal for the

Doctorate Program in Applied and Engineering Physics (DAEPHYS)

Starting in the Academic Year 2016/2017


Proposal 032


Title:Development of a state-of-the-art double crystal wavelength dispersive X-ray fluorescence spectrometer for nanolayered samples characterization
 
Objectives (recommended length: 2000-3000 char):
Wavelength Dispersive X-ray fluorescence (WDXRF) techniques, have been used for many years as a way to quantify trace elements in many types of systems, from biological to geological [1]. These systems make use of a crystal in a Bragg geometry to separate the characteristic X-rays coming from the X-ray irradiated sample, and feature a very high energy resolution when compared to energy dispersive XRF which uses solid state detectors [2].
The quantification method using these type of spectrometers is, however, somewhat difficult, as it requires some knowledge on the depth profile of the elemental distribution in the samples. The easiest way to perform such quantifications, is to use standard reference materials, which should mimic the absorption of the incident and characteristic X-rays in the bulk sample.

For nanolayered materials, such as silicon wafers, these reference materials do not exist, and the only way to perform depth profiling and quantification studies on such samples is by having a well-characterized monochromatic incident beam whose energy can be scanned through the absorption edges of each layer in the sample [3].

The aim of this work is to design and build a state-of-the-art double crystal wavelength dispersive X-ray fluorescence spectrometer, in which the first crystal acts as a monochromator of the incident radiation, and the second crystal as a wavelength selector. Thus it combines the very high resolution of a WDXRF with the capabilities of a monochromatic high brilliance source.

The X-ray tube which will drive the system is a Philips PW1400, with 100 kV 80 mA, with a Rh anode, and the X-ray detector is a Amptek XR-100CR Si-PIN with a uncollimated 7mm2 detection area and 300 µm thickness and a 25 µm Be window.

The nanolayered samples for the spectrometer characterization and testing will be manufactured by Chemical Vapour Deposition and their depth profile will be measured independently at INESC.


[1] E. Marguí, M. Hidalgo, I. Queralt, “Multielemental fast analysis of vegetation samples by wavelength dispersive X-ray fluorescence spectrometry: Possibilities and drawbacks”, Spectrochimica Acta Part B: Atomic Spectroscopy, 60, (9–10), 1363-1372, (2005)
[2] M. Guerra, M. Manso, S. Longelin, S. Pessanha and M. L. Carvalho, “Performance of three different Si X-ray detectors for portable XRF spectrometers in cultural heritage applications”, Journal of Instrumentation, 7, C10004 (2012)
[3] M. Kolbe, B. Beckhoff, M. Krumrey, G. Ulm, “Thickness determination for Cu and Ni nanolayers: Comparison of reference-free fundamental-parameter based X-ray fluorescence analysis and X-ray reflectometry”, Spectrochimica Acta Part B: Atomic Spectroscopy, 60, 505-510 (2005)
 
Framework (recommended length: 500-2000 char):
The Atomic Physics Group of LIBPhys-UNL has several decades of expertise in X-ray spectrometry in the fields of highly charged ion plasmas, toxicology, material analysis, cultural heritage and forensic science.
The required equipment, such as the X-ray tube and detector already exists in the Departments of Physics of the Universidade Nova de Lisboa (UNL).
 
Tasks (recommended length: 1000-3000 char):
1. Bibliographic study of WDXRF systems
2. Simulation of the system with a Monte-Carlo ray tracing code
3. Design of the spectrometer geometry and sample support
4. Construction of the spectrometer
5. Testing and characterization of the X-ray beam (shape, flux, etc..)
6. Quantification assessment of a high matrix range of reference materials
7. Depth profile studies of nanolayered samples
8. Dissertation writing
 
Research centre/lab or R&D unit hosting the thesis project:
LIBPhys-UNL
 
University to which the thesis project will be presented:
UNL - Universidade Nova de Lisboa
 
DAEPHYS Scientific Domain in which the project fits:
Instrumentation
 
Relation of the project to the Scientific Domains of DAEPHYS:
The project aims at designing and building a wavelength dispersive X-ray fluorescence spectrometer. The X-ray tube and detector will be adapted from an existing spectrometer at FCT UNL, while the two crystal rotation stages will be built and designed by the candidate. The control systems for the step motors and the control and acquisition software will also be developed by the candidate.
 
Candidate profile:
It is expected that the candidate is proficient in electronics and programming.
 
Does this proposal involve more than one University?:
no
 
Synergies between the two Universities participating in the proposal:
DAEPHYS strongly encourages the presentation of thesis projects in co-supervision by researchers from two of the universities participating in the Program. In this field, explain the benefits resulting from the proposed co-supervision and the involvement of elements from the two universities, e.g. building critical mass teams, profiting from existing infrastructures or advanced equipments, profiting from expert technical know-how, etc. If the proposal involves only one University, write n/a.
(recommended length: 500-1000 char)
: n/a
 
Does this proposal involve a company?:
no
 
Proposals involving a company:
DAEPHYS strongly encourages the presentation of thesis projects involving a company, preferably a high-tech company. These proposals have to: 1) be centered on a technological problem in which the partner company has been (or plan / would like to be) involved; 2) have a co-supervisor on the enterprise; 3) include part of the project to be carried out in the company.
(recommended length: 500-1000 char)
:

 

Supervisor

Name:Mauro António Moreira Guerra
Institution:Universidade Nova de Lisboa
email:mguerra@fct.unl.pt
 
link to CV or indication of ORCID ID:
0000-0001-6286-4048

 

Co-Supervisor

Name:José Paulo Moreira dos Santos
Institution:Universidade Nova de Lisboa
email:jps@fct.unl.pt
 
link to CV or indication of ORCID ID:
0000-0002-5890-0971

 

Uploaded PDF document: proposal-032.pdf