Louise Vrielink

1. 1 Good afternoon My name is Louise Vrielink. Since quite some years I�m responsible for the XRF analysis. I�m working in the group Catalytic Processes and Materials. However these analysis can also be performed for others within or outside the University. Good afternoon My name is Louise Vrielink. Since quite some years I�m responsible for the XRF analysis. I�m working in the group Catalytic Processes and Materials. However these analysis can also be performed for others within or outside the University.

2. XRF: a versatile analyzing technique Composition of bulk materials All elements from Boron Powder, liquid or solid 2 XRF has proven to be an accurate analyzing technique for bulk materials. Measurements can be done at all elements from boron up to uranium Samples can be powder, liquid and solid. Over the past years I analyzed a lot of different elements, nearly the complete periodic system! To give an idea I marked all elements I measure once ore more times In the past I measured sulfur in oil, Cd in house hold plastic. During open days I analyze the carat of jewelry Within the University all different kinds of oxides are analysed For our group, CPM, noble elements like Pt, Pd, Rh etc are measured often. Also Zr, Ce, Mo, Mg, Ta, Ir and so on XRF has proven to be an accurate analyzing technique for bulk materials. Measurements can be done at all elements from boron up to uranium Samples can be powder, liquid and solid. Over the past years I analyzed a lot of different elements, nearly the complete periodic system! To give an idea I marked all elements I measure once ore more times In the past I measured sulfur in oil, Cd in house hold plastic. During open days I analyze the carat of jewelry Within the University all different kinds of oxides are analysed For our group, CPM, noble elements like Pt, Pd, Rh etc are measured often. Also Zr, Ce, Mo, Mg, Ta, Ir and so on

3. Measurements and calculations on multi-layers 3 This is the apparatus Although the equipment is a bit old, it�s in a perfect condition and I use the most sophisticated software from Panalytical. This includes the FPMULTI module, that is used to perform calculations on thin layers. A sample changer makes it possible to measure up to 12 samples in a row. This is often used for measuring during the night Today I will focus on the measurements and calculations that are done on thin metal multi-layers. The first calculations on multi layers were very promising and thicknesses were found that correspond quite well with SEM and TEM results. Together with Roald Tiggelaar from the Mesoscale Chemical Systems group we considered a series of thin multi-layers that are used in both groups. We wanted to find out if XRF with the FPMULTI software could be useful to analyze these thicknesses. This is the apparatus Although the equipment is a bit old, it�s in a perfect condition and I use the most sophisticated software from Panalytical. This includes the FPMULTI module, that is used to perform calculations on thin layers. A sample changer makes it possible to measure up to 12 samples in a row. This is often used for measuring during the night Today I will focus on the measurements and calculations that are done on thin metal multi-layers. The first calculations on multi layers were very promising and thicknesses were found that correspond quite well with SEM and TEM results. Together with Roald Tiggelaar from the Mesoscale Chemical Systems group we considered a series of thin multi-layers that are used in both groups. We wanted to find out if XRF with the FPMULTI software could be useful to analyze these thicknesses.

4. Schematic representation of multi-layer configuration 4 This is the model of the multi-layers that we produced As the substrate we used Silica and Silicon nitride The adhesion layer consists of 10-20 nm Cr, Ta, Ti or Ti-tungsten The functional layer was chosen to be 10-150 nm of Au, Ta, Rh, Pd, Pt or Ni The layers were sputtered or evaporated. For the XRF measurements a 10 by 10 mm piece of the sample was used. One in the middle and one at the edge As a comparison the pieces from the middle of the stack were used to perform SEM and surface profilometry measurements. First I will give 2 examples to show how the analysis is performed This is the model of the multi-layers that we produced As the substrate we used Silica and Silicon nitride The adhesion layer consists of 10-20 nm Cr, Ta, Ti or Ti-tungsten The functional layer was chosen to be 10-150 nm of Au, Ta, Rh, Pd, Pt or Ni The layers were sputtered or evaporated. For the XRF measurements a 10 by 10 mm piece of the sample was used. One in the middle and one at the edge As a comparison the pieces from the middle of the stack were used to perform SEM and surface profilometry measurements. First I will give 2 examples to show how the analysis is performed

5. Qualitative parts of the XRF spectrum 5 I always start measuring a qualitative spectrum. For that I made an application that takes half an hour and all present elements will show up. 5 As an example I�ll show this multi layer with the K alfa lines of Si, Ti and Ni. The X-as shows the 2 teta edge, so the energy. The Y-as shows the intensity of the signal Even the oxygen from the silica can be seen, but with very low intensity. The signal Cu is due to the Cu mask, this mask is smaller than the internal mask of the system. Subsequently counts are measured quantitatively by counting a longer time at the top of the peak to get a better signal to noise ratio. As XRF is a comparison technique, standards have to measured at the same time. For these kinds of measurements pure metals are used as standards I always start measuring a qualitative spectrum. For that I made an application that takes half an hour and all present elements will show up. 5 As an example I�ll show this multi layer with the K alfa lines of Si, Ti and Ni. The X-as shows the 2 teta edge, so the energy. The Y-as shows the intensity of the signal Even the oxygen from the silica can be seen, but with very low intensity. The signal Cu is due to the Cu mask, this mask is smaller than the internal mask of the system. Subsequently counts are measured quantitatively by counting a longer time at the top of the peak to get a better signal to noise ratio. As XRF is a comparison technique, standards have to measured at the same time. For these kinds of measurements pure metals are used as standards

6. Calculations with FPMULTI 6 After the quantitative measurements calculations can be performed: First a model is made: The number of layers is chosen The elements are entered, as well as the density, expected thickness and composition Subsequently a choice is made what has to be calculated In this case only the thickness. And then the iteration can be started: Matrix effects occur from one to another layer. During the iteration process in every step the software calculates in every step the counts accompanying that multi-layer and compares that with the measured counts. If the measured and calculated counts are the same, it exact multi layer is found. This was the first multi-layer I measured and I found an adhesion layer twice as thick as expected. I became curious about the value of my calculations and to find out about it I asked for a TEM analysis. Which result is shown here. After the quantitative measurements calculations can be performed: First a model is made: The number of layers is chosen The elements are entered, as well as the density, expected thickness and composition Subsequently a choice is made what has to be calculated In this case only the thickness. And then the iteration can be started: Matrix effects occur from one to another layer. During the iteration process in every step the software calculates in every step the counts accompanying that multi-layer and compares that with the measured counts. If the measured and calculated counts are the same, it exact multi layer is found. This was the first multi-layer I measured and I found an adhesion layer twice as thick as expected. I became curious about the value of my calculations and to find out about it I asked for a TEM analysis. Which result is shown here.

7. Expected multi-layer: 7 Another example was the analysis of this multi layer. A group member expected to have these elements and thicknesses In our group a Ni top layer is used to grow CNF on it. As this person was not able to do this, he expected something strange with this sample. After analyzing and calculating with FPMULTI it turned out the thickness of Ni was only 1.4 nm instead of the expected 25! Note that for this sample also the composition of the TiW is analyzed! It was after these 2 notable examples that we decided to analyze a complete seriesAnother example was the analysis of this multi layer. A group member expected to have these elements and thicknesses In our group a Ni top layer is used to grow CNF on it. As this person was not able to do this, he expected something strange with this sample. After analyzing and calculating with FPMULTI it turned out the thickness of Ni was only 1.4 nm instead of the expected 25! Note that for this sample also the composition of the TiW is analyzed! It was after these 2 notable examples that we decided to analyze a complete series

8. Comparison XRF with surface profilometry and SEM 8 This slide shows all the different layers that were measured. It looks a bit confusing so I will focus first on one of the multi layers These are the thicknesses of this multi layer measured with the 3 different methods XRF however, gives extra information about the thickness of each sub-layer. Back to the complete set of measurements. Having a good look it is seen that in XRF the thickness is a bit lower than the other techniques. Here�s a very good explanation: The SEM measurements from the layers containing gold are not reliable The sample has top be cut and the edges gave problems because of the softness of gold Another method to compare the SEM with the XRF results is the next slide This slide shows all the different layers that were measured. It looks a bit confusing so I will focus first on one of the multi layers These are the thicknesses of this multi layer measured with the 3 different methods XRF however, gives extra information about the thickness of each sub-layer. Back to the complete set of measurements. Having a good look it is seen that in XRF the thickness is a bit lower than the other techniques. Here�s a very good explanation: The SEM measurements from the layers containing gold are not reliable The sample has top be cut and the edges gave problems because of the softness of gold Another method to compare the SEM with the XRF results is the next slide

9. Parity plot 9 On the X-ax the HR-SEM results are drawn and on the Y-ax the XRF results Quite well is seen that there�s a good correlation between both methods. Because this y-value is about 1. You can say it�s somewhat lower, as the XRF thicknesses are lower from nearly all the measured multi-layers On the X-ax the HR-SEM results are drawn and on the Y-ax the XRF results Quite well is seen that there�s a good correlation between both methods. Because this y-value is about 1. You can say it�s somewhat lower, as the XRF thicknesses are lower from nearly all the measured multi-layers

10. Conclusions 10 XRF is quick, especcially when a series of samples has to be analysed. Only once a calibration has to be made and without any sample preparation thin layers can be measured Non destructive, which makes it possible for example to perform analysis before and after an experimentXRF is quick, especcially when a series of samples has to be analysed. Only once a calibration has to be made and without any sample preparation thin layers can be measured Non destructive, which makes it possible for example to perform analysis before and after an experiment

11. Acknowledgement Thanks, Roald Tiggelaar, for manufacturing the thin films and the enthusiastic discussions 11

12. Welcome in Meander room 306! 12

13. Questions? 13