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DTSTART:20230621T130000Z
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LOCATION:ICFO Auditorium and Online (Teams)
SUMMARY:ICFO | DANIEL MARTÍNEZ CERCÓS
CLASS:PUBLIC
DESCRIPTION:There is currently significant scientific and technological int
 erest in ultrathin materials\, with at least one dimension in the nm range
  or even smaller\, since they possess features not achievable with their t
 hicker counterparts. The large electrical tunability and extreme field con
 finement in graphene and other two-dimensional (2D) materials provide a cl
 ear example of unique electrical and optical properties that can be used t
 o demonstrate unprecedented devices. Besides 2D materials\, ultra-thin met
 al films (UTMFs) are emerging as potential game-changers in the field of o
 ptoelectronics. However\, the standard deposition of metals via scalable f
 abrication methods\, such as sputtering or evaporation\, results in the fo
 rmation of disconnected metal islands at small thicknesses. Therefore\, su
 bstrate surface energy modification techniques are generally required to p
 romote early percolation of the metal films. In addition\, the tuning of t
 he physical properties of UTMFs after fabrication has been elusive for a l
 ong time due to the large charge carrier density of metals together with t
 he difficulties in obtaining continuous films at sufficiently small thickn
 esses. Recently\, nm-thick silver (Ag) and gold (Au) UTMFs have been obtai
 ned by using seed layers. Thanks to the small film thickness achieved thro
 ugh this technique\, large electro-optical tunability of plasmons supporte
 d by UTMFs through electrolyte gating was demonstrated for the first time.
 \nFollowing these advances\, throughout this thesis we introduce\, for the
  first time to our knowledge\, a new deposition technique consisting of se
 eding noble metal films with a sub-nanometric layer of cupric oxide. Such 
 a technique promotes the early percolation of Ag and Au on silicon dioxide
  and calcium fluoride while leaving unaltered the optical properties of th
 e substrate. The reported technique is scalable and is potentially expanda
 ble to the growth of other noble metals\, therefore showing great potentia
 l for use in actual technological applications. The morphological\, electr
 ical and optical properties of the resulting Ag and Au UTMFs are also stud
 ied as a function of the thickness\, demonstrating their high quality when
  conductive films with high transparency and/or ultra-smooth surfaces are 
 required.\nRegarding UTMF tunability\, firstly we show a new way to tune A
 u UTMFs by photoreduction. This technique is used to demonstrate that tran
 sparent conductive and IR plasmonic surfaces can be continuously tuned and
 \, if oxidation is added\, can be cycled back and forth. The functional tu
 ning enables reconfigurable UTMF structures to be achieved\, and also has 
 the potential to trimming their response to specific working points. This 
 method is thus important for the large-scale deployment of such surfaces a
 s one can compensate for material non-uniformity\, as well as morphologica
 l and structural dimension errors occurring during fabrication. Secondly\,
  we demonstrate reversible changes to the optical properties of infra-red 
 (IR) semi-reflective and plasmonic surfaces by combining Au UTMFs with ele
 ctrolyte gating\, particularly focusing on measurements in a reflection ge
 ometry. The results demonstrate the potential of the method for electro-op
 tical tunable devices in the IR regime\, and extend its applicability to s
 ituations in which working in a reflection configuration is required or be
 neficial. Examples include smart windows or chemical- or bio-sensing appli
 cations such as surface-enhanced infra-red absorption (SEIRA).\nThesis Dir
 ectors: Prof Dr. Valerio Pruneri and Dr. Bruno Paulillo
DTSTAMP:20260405T123130Z
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