1. Generation and Measurement of Surface Plasmon Coupled Emission Kathleen Hamilton Defense of the Masters Thesis University of New Hampshire June 15th, 2007

2. SPCE signals have been measured with novel material sets A compact apparatus has been constructed to measure these signals Depending on step size, a full 180º scan can be completed in < 5 minutes Reproducible scans can be made with resolutions up to 0.5˚ 2 Main Results

3. Outline Introduction Sample Preparation Apparatus Design and Construction Results Conclusions and Future Work 3

4. Introduction Fluorescence Surface Plasmons Surface Plasmon Resonance (SPR) Surface Plasmon Coupled Emission (SPCE) 4

5. Fluorescence Process of light emission from a molecule Repeatable Emission wavelength is characteristic of the dye Emission is isotropic green: excitation red: emission black: non-radiative processes 5

6. Surface Plasmons Oscillations of surface electrons in a metal Act as a wave propagating along interface Decay rapidly into the metal volume Can be used to transfer energy through thin films 6

7. Surface Plasmon Resonance (SPR) Absorption of incident energy into surface plasmons Prism is rotated, reflectance is measured as a function of  7 Excitation of SPR through a glass prism, incident on a silver film (grey) and dielectric overlayer (pink)

8. Describe reflection/transmission of light at dielectric and metal surfaces Boundary Conditions: Tangential E continuous Tangential B continuous Wave phases are equal Used to identify SPR angle Fresnel Equations 8

9. Four phase Fresnel Equations Affected by Thickness of silver films Thickness of dielectric overlayer Wavelength of incident light 9  mm 22 11 00

10. Calculated SPR curves for Ag films Films of thickness: 0 nm (blue), 50 nm (black), 20 nm (red), 80 nm (green), 100 nm (lt. blue) curves calculated using four-phase Fresnel programs from the research group of Robert M. Corn: http://unicorn.ps.uci.edu/calculations/fresnel/fcform.html 10

11. Effect of Dielectric Layer Thickness on SPR Angle SPR curves with dielectric overlayer thicknesses of: 5 nm (blue), 10 nm (black), 20 nm (red), 50 nm (green), 100 nm (lt. blue) curves calculated using four-phase Fresnel programs from the research group of Robert M. Corn: http://unicorn.ps.uci.edu/calculations/fresnel/fcform.html 11

12. Effects of Wavelength on SPR angle Calculated SPR curves for wavelengths: 532 nm (black), 550 nm (blue), 575 nm (red), 600 nm (green), 660 nm (lt. blue) curves calculated using four-phase Fresnel programs from the research group of Robert M. Corn: http://unicorn.ps.uci.edu/calculations/fresnel/fcform.html 12

13. SPCE “Inverse” process to SPR SPCE uses surface plasmons for emission at wavelength dependent angles Fluorescing molecules above a metal will induce plasmons in the metal Plasmons will couple to photons via glass interface 13

14. Methods of Generation Left: Reverse Kretschmann configuration (RK) Right: Kretschmann configuration (KR) 14

15. SPCE generation with the RK configuration Incident light excites fluorescence Fluorescing molecules induce plasmons on metal surface Plasmons are coupled to photons at glass interface Resulting light is emitted at angles determined by plasmon wavenumber 15

16. Outline Introduction Sample Preparation Apparatus Design and Construction Results Conclusions and Future Work 16

17. Sample Preparation a: adhesion layer b: passivation layer Two Components Thin films deposited by sputtering Thin fluorescent dye deposited by spin coating 17

18. Sputter Deposition Physical vapor deposition Deposition under vacuum reduced impurities in films Rotation of substrate creates films of uniform thickness Reactive gas sputtering creates material for passivation layer 18

19. Thin Film Stacks 19

20. Spin Coating Small volume of dye deposited on substrate Rotated at high speeds (2200- 3000 rpm) Result is thin, uniform coating 20

21. Outline Introduction Sample Preparation Apparatus Design and Construction Results Conclusions and Future Work 21

22. Apparatus Design and Construction Three Mechanical Components Excitation Rotation Detection Computer Interface and Control 22

23. Excitation with 5 mW laser ( = 532 nm) Driven by 2.85 V (DC) Beam divergence < 0.069º 23

24. Rotational motion is driven by a stepper motor Step resolution: 0.0281º Accuracy: <1º Repeatability: < 0.1º 24

25. Fluorescence detection made by a photomultiplier Wavelength filter 200  m aperture PMT amplifier Amplifier is needed to convert PMT output from current to voltage 25

26. Data acquisition module (DAQ) converts analog PMT signal to digital DAQ signal is read by LabVIEW program DAQ also controls voltage applied to the PMT Computer Control 26

27. Four part LabVIEW program PMT Voltage Specified Motor sent to home position Step size and number of steps specified Motor advances and DAQ signal is read on alternate iterations Angle and DAQ signal are written to file 27

28. Data from LabVIEW is imported to Matlab, plotted and fitted with Gaussian curves 28 Theta (deg.)

29. Outline Introduction Sample Preparation Apparatus Design and Construction Results Conclusions and Future Work 29

30. SPCE has been qualitatively observed from different material sets SPCE has been measured from different material sets SPCE signals have been measured with 4 different film stacks, made from 3 different material sets Depending on step size, a full 180º scan can be completed in < 5 minutes Results 30

31. SPCE Measurement 31

32. First detected SPCE signal 32 Theta (deg.) Signal Intensity (V)

33. Scans begin at 0˚ and traces out an angle  Peaks are measured in the regions:  90˚ Geometry of an SPCE scan

34. Repeated scans with increasing PMT voltage: 0.79 V (green), 0.81 V (blue), 0.84 V (black), 0.84 V (red) 34 Signal Intensity (V) Theta (deg.)

35. 5 repeated scans at 0.84 V Run  SPCE 0157.8 ± 1.4 122.8 ± 0.3 0258.3 ± 0.6 122.7 ± 0.2 0356.6 ± 1.6 124 ± 0.9 0458.0 ± 1.1 122.9 ± 0.8 0557.7 ± 1.0 123.2 ± 0.3 First (red), second (blue), third (black), fourth (green), fifth (magenta) 35 Theta (deg.) Signal Intensity (V)

36. 3 scans at 0.84 V Scan  SPCE 0167.9 ± 11.9 118.7 ± 0.4 0264.2 ± 6.2118.7 ± 0.3 0363.8 ± 5.3118.3 ± 0.2 36 Theta (deg.) Signal Intensity (V)

37. Angular Reproducibility High uncertainty in fits due to poor fitting of small peaks Variant peaks at same voltage Altering the voltage of consecutive scans led to uniformity Repeated Scan Characteristics 37

38. Tests of Si/Ag/Si-O(x) (5% O 2 ) Scans with PMT voltages: 0.75 V (blue), 0.79 V (green), 0.84 V (red), 0.84 V (black) Run  SPCE 0.75V68.4 ± 0.2 127.1 ± 0.8 0.79V69.5 ± 0.2 129.9 ± 0.6 0.83V64.2 ± 0.2 124.9 ± 0.5 0.84V66.2 ± 0.2 126.4 ± 0.4 38 Theta (deg.) Signal Intensity (V)

39. Tests of Si/Ag/Si-O(x) (10% O 2 ) Scan  SPCE 0.75 V47.4 ± 2.2105.3 ± 5.4 0.81 V53.3 ± 0.7112.9 ± 2.3 0.84 V55.2 ± 1.3115.1 ± 2.1 PMT Voltages: 0.75 V (black), 0.81 V (red), 0.84 V (blue) 39 Theta (deg.) Signal Intensity (V)

40. Higher Resolution Scans Previous scans were made with step sizes of 1.0º Scans were made with smaller step sizes, 0.75º, 0.5º, 0.25º, 0.2º, 0.1º Step sizes > 0.5º show similar angular reproducibility as the 1.0º step size scans Step sizes < 0.5º show poor angular reproducibility 40

41. Smaller Step Scans Left: Step sizes of 1.0º (red), and 0.5º (black) Right: Step sizes of 0.1˚ (black), 0.15˚ (blue), and 0.2˚ (red) 41 Theta (deg.) Signal Intensity (V)

42. Reverse Scans Second LabVIEW program written Program will execute two scans in two directions First scan will be done in clockwise direction Second scan will be done in counter- clockwise direction Reversed direction scans were done to check angular reproducibility 42

43. Clockwise and Counter-clockwise scans at 1.0º step size Run  SPCE CW67.3 ± 0.1136 ± 0.3 CCW68.2 ± 0.3136 ± 0.3 Clockwise (red) and counterclockwise (black) SPCE scans with 1˚ step size. 43 Signal Intensity (V) Theta (deg.)

44. Clockwise and Counter-clockwise scans at 0.2º step size Run  SPCE CW48.2 ± 0.1 CCW56.1 ± 0.1 Clockwise (red) and counterclockwise (black) scans with step size of 0.2˚ 44 Theta (deg.) Signal Intensity (V)

45. Outline Introduction Sample Preparation Apparatus Design and Construction Results Conclusions and Future Work 45

46. Conclusions and Future Work SPCE can be generated with many different material sets Adhesion/Passivation materials may affect fluorescence intensities Scans with step sizes >0.5˚ are reproducible Fluorescent dye quality Symmetry of peaks 46

47. Acknowledgments Thanks to the current and former members of Jim Harper’s group: Amanda Brown, Don Carlson, Derya Deniz, Dana Filoti and Anne-Marie Shover Thanks to the current and former members of Tom Laue’s group: Brett Austin, Sue Chase, and Kari Hartmen for their help in early design of the apparatus and fluorescent dye preparation Thanks to Rudolf Seitz of the Chemistry Department for access to the spin coater Thanks to Rob Cinq-Mars of the UNH Instrumentation Center for help in LabVIEW programming and stepper motor operation Thanks to Ignacy and Zygmunt Gryczynski of the University of North Texas Thanks to the thesis committee members: Professors Tom Laue, Olof Echt and James Harper 47

48. Support This thesis was financially supported in part by NIH Grant 1-R33CA14460-01 48

50. Tests of AlSi/Ag/AlSi-N (15% N 2 ) Scan  SPCE 0.75 V50.8 ± 1.0108 ± 1.8 0.79 V48.3 ± 0.8106.2 ± 1.9 0.81 V54.4 ± 0.5114.1 ± 1.1 0.83 V50.0 ± 0.3111.9 ± 0.9 0.85 V54.3 ± 0.3117.5 ± 1.7 Scans with PMT voltage: 0.75 V (red), 0.79 V (green), 0.81 V (grey), 0.84 V (blue), 0.84 V (black) 50

51. Scans of Si/Ag/Si-O(x) (5% O 2 ), 20nm thick passivation layer PMT voltages 0.75 V (green), 0.77 V (blue), 0.84 V (red) and 0.84 V (black). Run  SPCE 0.75 V48.5 ± 0.5 109.4 ± 1.0 0.77 V52.2 ± 0.4 116.9 ± 4.7 0.83 V51.7 ± 1.4 110.5 ± 3.5 0.85 V54.8 ± 1.4 113.7 ± 1.0

52. Fluorescence Spectrum plot from Molecular Probes: http://probes.invitrogen.com/servlets/spectra?fileid=6393ph8

53. Semi-transparent and highly reflective slides AlSi/Ag/AlSi-N Si/Ag/Si-O(x) (5% O 2 ) Highly transparent and semi- reflective slides Si/Ag/Si-O(x) (10% O 2 ) 53

54. Theta (deg.) Signal Intensity (V) Signal Attenuation as films erode Left: Dye layer newly deposited Right: 18 hours later Sample: Si/Ag/SiO(x) (5% oxygen)