SEM-CL presentation at ICOM 2015 - Budva Montenegro
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Examples of SEM-CL in combination with EDX, for use in phosphor research. From phosphor evaluation at the microscopic scale to single particle analysis
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SEM-CL presentation at ICOM 2015 - Budva Montenegro
- 1. Cathodoluminescence in electron microscopy: from phosphor evaluation to single particle analysis Philippe F. Smet, Lisa I.D.J. Martin, Jeroen Wattez, Filip Strubbe, Jonas J. Joos, Jonas Botterman, Katleen Korthout, Sofie Abé, Heleen Sijbom, Dirk Poelman http://LumiLab.UGent.be http://tiny.cc/amazingCL philippe.smet@ugent.be @pfsmet ICOM 2015 – Budva/Montenegro – September 1 2015
- 2. ‘Cold light’: generation of light in a non-thermal way • Photoluminescence (PL) • Cathodoluminescence (CL) • Electroluminescence (EL) • Chemoluminescence • Bioluminescence • Radioluminescence (RL) • Triboluminescence • Sonoluminescence • Thermoluminescence (TL) (?) CL: a brief introduction
- 3. Focused electron beam (1 to 30 keV) Heat Light (CL) White x-rays Characteristic x-rays Auger e- Secondary e- Backscattered e- Transmitted e- Diffracted e- Sample CL: a brief introduction
- 4. CL: a brief introduction Cathode ray tube (CRT) Field emission display (FED/SED)
- 5. CL CL: a brief introduction 4µm 4µm 25keV SrS Casino
- 6. CL: Spatial resolution STEM-CL Zagonel et al, Nano Letters 2011(11) 568-573 Nanometer scale spectral imaging of quantum emitters in nanowires Halfgeleiders? 20nm
- 7. EDX detector Electron detectors Spectrograph CCD SEM chamber Optical fiber Setup - 1. Add light collection and analysis to SEM-EDX
- 8. Data collection method 51200 spectra
- 9. Phosphor (nm) FWHM (nm) 400 nm 445 nm (K) (ns) SrSi2O2N2:Eu2+ 541 74 ++ + 0.62 450 905 Ba3Si6O12N2:Eu2+ 524 75 + - 0.39 435 1270 ZnGa2S4:Eu2+ 542 50 + ++ 0.14 242 135 SrGa2S4:Eu2+ 534 49 ++ ++ 0.71 460 450 Case 1: ZnGa2S4:Eu
- 11. ZnGa2S4:Eu (1%) EuGa2S4 Case 1: ZnGa2S4:Eu
- 12. Saturated green emission, but... • Severe thermal quenching • Short lifetime • Low quantum efficiency (<20%) Origin of green luminescence? Case 1: ZnGa2S4:Eu
- 13. EDX: chemical composition at the microscopic scale Zn in green, Eu in red J.J. Joos et al, Optical Materials Express 3 (2013) 1338 Case 1: ZnGa2S4:Eu
- 14. Zn in green, Eu in red Formation of EuGa2S4 percipitates J.J. Joos et al, Optical Materials Express 3 (2013) 1338 Case 1: ZnGa2S4:Eu CL mapping EDX mapping Optical behaviour Chemical composition
- 18. Case 2: Sr0.25Ba0.75Si2O2N2:Eu PL, 10K PL, 295K
- 19. Case 2: Sr0.25Ba0.75Si2O2N2:Eu 3 2 1
- 21. Temperature stage EDX detector Electron detectors Spectrograph CCD SEM chamber Optical fiber Setup - 2. Add a temperature stage
- 22. Case 3: Thermal quenching in SrGa2S4:Eu SrSi2O2N2:Eu2+ Ba3Si6O12N2:Eu2+ ZnGa2S4:Eu2+ SrGa2S4:Eu2+
- 23. 5µm Total CL intensity Peak emission wavelength l(nm) FWHM nm Case 3: Thermal quenching in Sr0.9Eu0.1Ga2S4
- 24. 2.5µm Total CL intensity (-20°C) CL (100°C)/CL (-20°C) 60% 100% 80% EDX Eu-L signal Total CL intensity (100°C) Case 3: Thermal quenching in Sr0.9Eu0.1Ga2S4
- 25. Recording CL maps at different temperatures Aligning all maps by appropriate shifting/skewing 5µm Temperature (K) Local variations in Eu concentration affect global thermal quenching Case 3: Thermal quenching in Sr0.9Eu0.1Ga2S4
- 26. Case 4: Lifetimes in SEM-CL D. den Engelsen et al., Ultramicroscopy 2015 http://dx.doi.org/10.1016/j.ultramic.2015.05.009
- 27. Temperature stage EDX detector Electron detectors Spectrograph ICCD SEM chamber Optical fiber Beam blanker Pulse generator Setup - 3. Add a fast beam blanker
- 28. Eu-rich Ca-rich t-mapping Case 4: Luminescence lifetime in (Ca,Eu)2SiS4 D. Poelman and P.F. Smet, Physica B 439 (2014) 35-40
- 29. 3 points are sufficient to calculate t - saves time! Case 4: Luminescence lifetime in (Ca,Eu)2SiS4 D. Poelman and P.F. Smet, Physica B 439 (2014) 35-40
- 30. Eu-rich Ca-rich t-mapping Case 4: Luminescence lifetime in (Ca,Eu)2SiS4 D. Poelman and P.F. Smet, Physica B 439 (2014) 35-40
- 31. Temperature stage EDX detector Electron detectors Spectrograph ICCD SEM chamber Optical fiber Setup - 4. Collecting optics. Let’s integrate?
- 32. Case 5: Single particle analysis – SrS:Eu K. Korthout et al. / Optical Materials 33 (2011) 1128–1130
- 33. Case 5: Single particle analysis – SrS:Eu
- 34. Case 5: Single particle analysis – SrS:Eu
- 35. Case 5: Single particle analysis – SrS:Eu
- 36. Case 5: Single particle analysis – Ray tracing simulation
- 37. Case 5: Single particle analysis - Ray tracing simulation
- 38. Case 5: Single particle analysis - Ray tracing simulation
- 39. Case 5: Single particle analysis 620nm 622nm 624nm CL intensity Emission barycenter Reabsorption plays a role!
- 40. Application notes Type of materials • Impurity doped phosphors: + to ++ • Quantum dots: - • Organic compounds: -- Spatial resolution • Depends on sample morphology • Thickness and composition • Accelerating voltage Collection optics: integrating setup or fiber? • CL emission intensity • Need for BSE/EDX • Topic of interest K2SiF6:Mn4+
- 41. Case 6: Hybrid conversion layers (phosphor + quantum dots) CdSe/CdS core-shell quantum dots SrGa2S4:Eu phosphor Organic binder
- 42. Conclusions • ‘Standard’ photoluminescence research at microscale • Discriminates between bulk and local behaviour • Interesting add-on in phosphor research • Standalone for single-particle analysis CL in electron microscopy
- 43. Acknowledgments Thank you for your attention! http://LumiLab.UGent.be http://tiny.cc/amazingCL philippe.smet@ugent.be @pfsmet