Publications

2024

• Photochemistry of bismuth- and silver-containing glasses under femtosecond laser irradiation: energy transfers and 3D-localized background-free near-infrared fluorescence emission
  
  • Alassani Fouad
  • Ollier Nadège
  • Raffy Guillaume
  • Fargues Alexandre
  • del Guerzo André
  • Canioni Lionel
  • Cardinal Thierry
  • Petit Yannick
  Journal of Physical Chemistry C, American Chemical Society, 2024, 128 (20), pp.8296–8306. The tunable fluorescence property from the visible to near-infrared (NIR) region of high-localized 3D architecture down to the diffraction limit thanks to femtosecond (fs) Direct Laser Writing (DLW) in bismuth-doped, silver-containing glass is performed. Absorption and photoluminescent spectroscopy showed evidence of the homogeneous dispersion of bismuth ions (Bi3+) and silver ions in the glass matrix before DLW. High repetition rate fs DLW simultaneously inducing the photochemistry of silver ions and the photoredox reaction of bismuth ions has been obtained. Femtosecond DLW allows the creation of 3D fluorescence patterns formed by colocalization of a silver cluster and low valence bismuth ions, exhibiting an emission band covering the whole visible to the NIR wave range. The phenomena of electron transfer from silver atoms to bismuth ions and the nonradiative energy transfer from silver clusters to NIR-emitting bismuth ions are demonstrated. (10.1021/acs.jpcc.4c01036)
  DOI : 10.1021/acs.jpcc.4c01036
• Femtosecond laser activation of the photochemistry of Bismuth and associated threedimensional sub-micron fluorescence patterning
  
  • Alassani Fouad
  • Ollier Nadège
  • Canioni Lionel
  • Petit Yannick
  • Cardinal Thierry
  Journal of Luminescence, Elsevier, 2024, 275, pp.120728. Localized sub-micrometer-scale visible and near-IR fluorescence structures have been achieved in three-dimension (3D) thanks to femtosecond laser-activated photochemistry of Bismuth in a Bismuth-doped phosphate glass. These structures exhibit high fluorescence contrast with good spatial resolution with spectral emission in the red and near-IR ranges. These fluorescence properties arise from femtosecond laser-induced multi-photon absorption and the creation of free electrons, which activates local redox reactions of Bi3+ that allow for the dose-dependent formation of low valence Bismuth ions such as Bi2+ and Bi+. These new species promote not only new selective fluorescence emission properties in the VIS and near-IR spectral range but also co-localized positive refractive index changes. The thermal treatment of 3D patterns evidences the possibility of Bismuth cluster formation with good thermal stability up to the glass temperature transition. These observations open the way for laser-inscribed photonic integrated circuits for potential laser amplification devices in the second telecommunication windows around 1.3 μm. (10.1016/j.jlumin.2024.120728)
  DOI : 10.1016/j.jlumin.2024.120728
• Direct observation of electronic bandgap and hot carrier dynamics in GeAs semiconductor
  
  • Zhang Zailan
  • Zhang Jiuxiang
  • Zhou Gangqiang
  • Xu Jiyuan
  • Michel Ian-Evan
  • Dappe Yannick
  • Zhang Xiao
  • Oughaddou Hamid
  • Qi Weiyan
  • Papalazarou Evangelos
  • Perfetti Luca
  • Chen Zhesheng
  • Bendounan Azzedine
  • Marsi Marino
  Applied Physics Letters, American Institute of Physics, 2024, 125 (18). Germanium arsenide (GeAs) is a layered semiconductor with remarkably anisotropic thermoelectric and optical properties and a promising candidate for multifunctional devices based on in-plane polarization dependent response. Understanding the underlying mechanism of such devices requires knowledge of GeAs electronic band structure and of the hot carrier dynamics in its conduction band, whose details are still unclear. In this work, we investigate the properties of occupied and photoexcited states of GeAs, by combining scanning tunneling spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and time-resolved ARPES. We find that GeAs is an ∼0.8 eV indirect gap semiconductor, for which the conduction band minimum (CBM) is located at the Γ ¯ point while the valence band maximum is out of Γ ¯ . A Stark broadening of the valence band is observed immediately after photoexcitation, which can be attributed to the effects of the electrical field at the surface induced by inhomogeneous screening. Moreover, the hot electron relaxation time of 1.56 ps is down to the CBM, which is dominated by electron-phonon coupling. Besides their relevance for our understanding of GeAs, these findings present general interest for the design of high performance thermoelectric and optoelectronic devices based on 2D semiconductors. (10.1063/5.0233111)
  DOI : 10.1063/5.0233111