Enhancement of the Er3+luminescence in Er-doped silica by few-atom metal aggregates

Gold-based nucleation in implanted silica studied by x-ray absorption spectroscopy

“…It is worth noting that, although this equation derives from theoretical calculations (mainly DFTbased) for Au clusters in vacuum, data available in the literature on supported or embedded Au clusters agree with it [9,22].…”

“…In some cases, a triple implantation energy scheme for each implanted ion species was used, to obtain a homogeneous concentration depth profile in the implanted region. Since these systems were produced to investigate the interaction of metal clusters with rare-earth ions (not reported here) [9,15], a selection of samples was previously implanted with Er ions and annealed at 800 1C for 1 h in N 2 to activate the 1.54 μm Er emission. The total implantation fluence was measured by Rutherford Backscattering Spectrometry.…”

“…The possible presence of dispersed oxide phases is also detectable, as well as the interatomic correlation of atoms at the cluster surface with atoms of the surrounding matrix [9]. To experimentally investigate the very early steps of metal nucleation, implanted layers (usually less than 100 nm thick) have a very low metal concentration i.e., in implanted silica metal nucleation occurs for metal density in the range of E1 at%: the XAS experiments are very demanding in terms of needed photon flux, integration time and required experimental setup [17,18].…”

“…In the last years it has been shown that, by reducing the metal implantation fluence and for moderate annealing conditions, the average cluster size could be reduced down to the size critical for the thermodynamic stability, corresponding to few atom aggregates [9,10]. This is very interesting for a number of reasons.…”

“…Nevertheless, it is known that for cluster nucleation in a matrix the energy barrier to be overcome for heterogeneous nucleation is lower than for the corresponding homogeneous nucleation, but it is not easily determined quantitatively. About the possible practical applications of molecule-like clusters and as a final point, it has been shown that sub-nanometer Au clusters embedded into Er-doped silica, when excited in the UV-vis range, can transfer part of the absorbed energy to the Er ions, dramatically increasing the effective cross section for 1.54 μm Er 3 þ emission, with promising application in photonics [9,15]. This energy transfer process has been tentatively related with the photoluminescence band at 890 nm of small Au clusters, whose origin is thought to be the electronic surface states of gold clusters [13].…”