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@ARTICLE{Kerfoot:634412,
      author       = {Kerfoot, James and Legge, Elizabeth J. and Collins, Amy and
                      Chauhan, Jasbinder and Rossnagel, Kai and Beton, Peter H.
                      and Mellor, Christopher J. and Pollard, Andrew J. and Rance,
                      Graham A. and George, Michael W.},
      title        = {{B}enchmarking {TERS} and {TEPL} probes: towards a
                      reference sample for quantification of near-field
                      enhancement factors in gap and non-gap modes},
      journal      = {The analyst},
      volume       = {150},
      number       = {14},
      issn         = {0003-2654},
      address      = {Cambridge},
      publisher    = {Soc.},
      reportid     = {PUBDB-2025-02495},
      pages        = {3077 - 3088},
      year         = {2025},
      note         = {JK, GAR and MWG acknowledge funding from the Engineeringand
                      Physical Science Research Council (EPSRC) (Project:
                      EP/V053884/1) and support from the Nanoscale and
                      MicroscaleResearch Centre (nmRC). EJL and AJP would like to
                      acknowl-edge the National Measurement System (NMS) of
                      theDepartment for Science, Innovation and Technology
                      (DSIT),UK ( projects #128826) for funding. The authors
                      thankDongkuk Kim and Sebastian Wood at the National
                      PhysicalLaboratory, U.K., for discussion associated with
                      themanuscript.},
      abstract     = {Benchmarking the near-field signal enhancement attained
                      using plasmonic metal-coated atomic force microscopy (AFM)
                      probes for tip-enhanced Raman spectroscopy (TERS) and
                      tip-enhanced photoluminescence (TEPL) measurements is
                      challenging given the absence of a suitable reference sample
                      that is simple to prepare, easy to use and compatible with
                      different instrument configurations. To this end, in this
                      study, we have fabricated a flake of monolayer tungsten
                      diselenide (1L-WSe$_2$) stamped across the interface of gold
                      and silver thin films on silicon dioxide and glass. We have
                      demonstrated these samples to be effective for the facile
                      determination of near-field Raman and photoluminescence
                      contrast factors in both gap and non-gap mode, respectively.
                      We show that the near-degenerate E$^1$$_{2g}$ + A$_{1g}$ and
                      2LA(M) peaks in the Raman spectra of WSe$_2$2 enable
                      quantification of Raman contrast factors, with a ∼1.6-fold
                      increase in TERS signal enhancement in gap mode, relative to
                      non-gap mode, observed for a typical probe. Similar
                      differences in the photoluminescence contrast factors were
                      observed comparing in-contact and out-of-contact signal
                      intensity ratios from gap and non-gap mode TEPL
                      measurements. Moreover, in developing a reference
                      methodology we found that the line shape of the TEPL profile
                      was dependent upon the magnitude of the signal enhancement,
                      with a disproportionate increase in the longer wavelength
                      shoulder of the emission observed in gap mode. As this
                      contribution to the asymmetric line shape is tentatively
                      assigned to a dark exciton, which possesses an out-of-plane
                      transition dipole moment, our TEPL measurements indicate
                      that the directionality of the near-field enhancement
                      provides a further handle enabling quantification of probe
                      performance. Using samples prepared on glass, and comparing
                      results obtained from two different instruments, each with a
                      different excitation laser wavelength and optical access, we
                      demonstrate the universal applicability of our reference
                      material for sensitivity benchmarking of metallised AFM
                      probes in both gap and non-gap mode, suitable for both
                      reflection and transmission geometries, and across the range
                      of laser wavelengths typically used for TERS and TEPL.},
      cin          = {FS-SXQM},
      ddc          = {540},
      cid          = {I:(DE-H253)FS-SXQM-20190201},
      pnm          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632)},
      pid          = {G:(DE-HGF)POF4-632},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:40525753},
      doi          = {10.1039/D5AN00456J},
      url          = {https://bib-pubdb1.desy.de/record/634412},
}