Unexploited Information from Luminescence Spectra
Luminescence is a highly sensitive technique to monitor the presence of impurities, imperfections and lattice distortions. To fully exploit it requires sensitive detection systems with high resolution spectral data and temperature control. This review notes both how detector technology has advanced, and mentions simple routes to generate more efficient use of existing photomultipliers. Modern detectors enable wavelength multiplexed spectrometer systems, which are prerequisites for both detailed thermoluminescence analyses and newer applications. These include recording the spectral changes from different crystalline phases, and capturing their characteristic intensity signatures at the phase transition temperature. Less expected is that the luminescence intensity is strongly influenced by the presence of impurities, even when they are not dispersed in the host lattice, but are grouped as nanoparticle inclusions. Spectacular host intensity changes can occur when the inclusions undergo phase transitions. Luminescence is also frequently used to monitor ion implanted materials, but for examples reported here, the spectra can be seriously distorted by absorption and reflectivity properties of the implant layer. Further, luminescence data have demonstrated that the underlying host material can be stressed and then relax into new structural phases. These aspects of spectral distortion and lattice relaxations may be far more common than has been noted in the previous literature. Finally, because the techniques are multi-disciplinary, brief mentions of systematic errors in signal analysis are noted.
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Townsend, P. D., “Photocathodes – Past performance and future potential”, Contemp. Phys. 44, 17-34 (2003).
Townsend, P.D., Downey, R., Harmer, S.W., Wang, Y., Cormack, A., McAlpine, R, Bauer, T. “Designs for waveguide and structured photocathodes with high quantum efficiency”, J. Phys. D: Appl. Phys. 39, 1525-1536 (2006).
Harmer, S. W., Townsend, P. D., Bowring, J., “Enhancement of photomultiplier sensitivity with anti-reflective layers”, J. Phys. D: Appl. Phys. 45, 055102 (2012).
Harmer, S.W., Townsend, P.D., “Improving the performance of photomultiplier tubes”, J. Phys. D: Appl. Phys. 43, 415101 (2010).
Townsend, P.D., Valberg, L., Momchilov, N., Harmer, W. S., Downey, R., Cormack, A. J., “Optimization of photomultiplier spectral sensitivity with a graded thickness photocathode”, J. Phys D: Appl. Phys. 41, 185504 (2008).
Harmer, S. W., Townsend, P. D., “Low cost enhancements of photomultiplier sensitivity”, Proc. SPIE, 7747, 77470A-5 (2011).
Townsend, P. D., Hallensleben, S.,Phillips, M., Downey, R. J., Brooks, R. J., Howorth, J., Milnes, J., “Improvements in sensitivity and response times of photon imaging tubes”, J. Phys. D : Appl. Phys. 39, 4331-4336 (2006).
Townsend, P. D., Crespillo, M. L., “An ideal system for analysis and interpretation of ion beam induced luminescence”, Physics Procedia, 66, 345-351 (2015).
Can, N., Townsend, P. D., Hole, D. E., Snelling, H. V., Ballesteros, J. M., Afonso, C. N., “Enhancement of luminescence by pulse laser annealing of ion implanted europium in Sapphire and Silica”, J. Appl. Phys. 78, 6737- 6744 (1995).
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Holgate, S. A., Sloane, T. H., Townsend, P. D., White, D. R., Chadwick, A. Y., “Thermoluminescence of calcium fluoride doped with neodymium”, J. Phys. Condens. Matter 6, 9255-9266 (1994).
Yang, B., Townsend, P. D., Rowlands, A. P., “Low temperature thermoluminescence of rare earth doped lanthanum fluoride”, Phys. Rev. B 57, 178-188 (1998).
Yang, B., Townsend, P. D., “Patterns of peak movement in rare earth doped lanthanum fluoride”, J. Appl. Phys. 88, 2103-2122 (2000).
Maghrabi, M., Karali, T., Townsend, P. D., Lakshmanan, A. R., “Luminescence spectra of CaSO4 with Ce, Dy, Mn and Ag co-dopants”, J. Phys. D: Appl. Phys. 33, 477-484 (2000).
Raymond, S. G., Townsend, P. D., “The influence of rare earth ions on the low temperature thermoluminescence of Bi4Ge3O12”, J. Phys: Condens. Matter 12, 2103-2122 (2000).
Karali, T., Can, N., Townsend, P. D., Rowlands, A. P., Hanchar, J., “Radioluminescence and thermoluminescence of rare earth element and phosphorus-doped zircon”, Am. Mineral. 85, 668-681 (2000).
Townsend, P. D., Maghrabi, M., Yang, B., “Luminescence detection of phase transitions”, Nucl. Instrum. Meth. B 191, 767-771 (2002).
Townsend, P. D., Yang, B., Wang, Y., “Luminescence detection of phase transitions, local environment and nanoparticle inclusions”, Contemp. Phys. 49:4, 255-280 (2008).
Wang, Y., Townsend, P. D., “Structural changes and relaxations monitored by luminescence”, Luminescence 28, 253-258 (2013).
Yang, B., Townsend, P. D., Fromknecht, R., “Radioluminescence detection of bulk effects in SrTiO3 induced by surface ionimplantation”, Nucl. Instrum. Meth. B 217, 60-64 (2004).
Yang, B., Townsend, P. D., Fromknecht, R., “Low temperature detection of phase transitions and relaxation processes in SrTiO3 by means of cathodoluminescence”, J. Phys: Condens. Matter 16, 8377-8386 (2004).
Yang, B., Townsend, P. D., Fromknecht, R., “Effects of the ion-implantation on the thermoluminescence spectra of strontium titanate’’, Nucl. Instrum. Meth. B 226, 549 (2004).
Wang, Y., Ma, B., Zhang, W., Li, D., Zhao, Y., Finch, A. A., Townsend, P. D., “Substrate lattice relaxations, spectral distortions and nanoparticle inclusions of ion implanted zinc oxide”, J. Appl. Phys. 118, 095703 (2015).
Ege, A., Wang, Y., Townsend, P. D., “Systematic errors in thermoluminescence”, Nucl. Instrum. Meth. A 576, 411-416 (2007).
Wang, Y., Townsend, P. D., “Potential problems in collection and data processing of luminescence signals”, J. Lumin. 142, 202-211(2013).