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Broadband optical ultrafast reflectivity of Si, Ge and GaAs. Sci Rep 2020; 10:17363. [PMID: 33060665 PMCID: PMC7567120 DOI: 10.1038/s41598-020-74068-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/21/2020] [Indexed: 11/09/2022] Open
Abstract
AbstractUltrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM, $$\lambda $$
λ
= 400 nm) as a pump and broadband 340–780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/$$\hbox {cm}^2$$
cm
2
for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the $$E_1$$
E
1
, $$E_1+\Delta $$
E
1
+
Δ
singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.
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Catone D, Di Mario L, Martelli F, O'Keeffe P, Paladini A, Stefano Pelli Cresi J, Sivan AK, Tian L, Toschi F, Turchini S. Ultrafast optical spectroscopy of semiconducting and plasmonic nanostructures and their hybrids. NANOTECHNOLOGY 2020; 32:025703. [PMID: 32937606 DOI: 10.1088/1361-6528/abb907] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). Indeed, improvement of photocatalytic efficiencies by combining semiconductor and plasmonic nanostructures is one of the reasons why their ultrafast dynamics are intensively studied. In this work, we will review our activity on ultrafast spectroscopy in nanostructures carried out in the recently established EuroFEL Support Laboratory. We have investigated the dynamical plasmonic responses of metal NPs both in solution and in 2D and 3D arrays on surfaces, with particular attention being paid to the effects of the NP shape and to the conversion of absorbed light into heat on a nano-localized scale. We will summarize the results obtained on the carrier dynamics in nanostructured perovskites with emphasis on the hot-carrier dynamics and in semiconductor nanosystems such as ZnSe and Si nanowires, with particular attention to the band-gap bleaching dynamics. Subsequently, the study of semiconductor-metal NP hybrids, such as CeO2-Ag NPs, ZnSe-Ag NPs and ZnSe-Au NPs, allows the discussion of interaction mechanisms such as charge carrier transfer and Förster interaction. Finally, we assess an alternative method for the sensitization of wide band gap semiconductors to visible light by discussing the relationship between the carrier dynamics of TiO2 NPs and V-doped TiO2 NPs and their catalytic properties.
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Affiliation(s)
- Daniele Catone
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Lorenzo Di Mario
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Faustino Martelli
- CNR-IMM, Area della Ricerca di Roma Tor Vergata, 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Patrick O'Keeffe
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 00015 Monterotondo Scalo, Italy
| | - Alessandra Paladini
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 00015 Monterotondo Scalo, Italy
| | - Jacopo Stefano Pelli Cresi
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 00015 Monterotondo Scalo, Italy
| | - Aswathi K Sivan
- CNR-IMM, Area della Ricerca di Roma Tor Vergata, 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Lin Tian
- CNR-IMM, Area della Ricerca di Roma Tor Vergata, 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Francesco Toschi
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 00015 Monterotondo Scalo, Italy
| | - Stefano Turchini
- Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), 100 Via del Fosso del Cavaliere, 00133 Rome, Italy
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