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  1. Razeghi, Manijeh ; Jarrahi, Mona (Ed.)
    GeS and GeSe are 2D semiconductors with band gaps in the near infrared and predicted high carrier mobility. We find that excitation with 800 nm pulses results in long-lived free photocarriers, persisting for hundreds of picoseconds, in GeS and GeSe noribbons. We also demonstrate that zerovalent Cu intercalation is an effective tool for tuning the photoconductive response. Intercalation of ~ 3 atomic % of zerovalent Cu reduces the carrier lifetime in GeSe and GeS. In GeS, it also shortens the photoconductivity rise and improves carrier mobility. 
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  2. Betz, Markus ; Elezzabi, Abdulhakem Y. (Ed.)
  3. Betz, Markus ; Elezzabi, Abdulhakem Y. (Ed.)
  4. Betz, Markus ; Elezzabi, Abdulhakem Y. (Ed.)
  5. We use transient optical absorption and time-resolved terahertz THz spectroscopy to investigate photoexcitations in Ti3C2, Mo2Ti2C3, and Nb2C. Measurements reveal pronounced plasmonic effects. Monitoring them provides insights into thermal relaxation processes and low thermal conductivity.

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  6. Abstract

    Above‐band gap optical excitation of non‐centrosymmetric semiconductors can lead to the spatial shift of the center of electron charge in a process known as shift current. Shift current is investigated in single‐crystal SnS2, a layered semiconductor with the band gap of ≈2.3 eV, by THz emission spectroscopy and first principles density functional theory (DFT). It is observed that normal incidence excitation with above gap (400 nm; 3.1 eV) pulses results in THz emission from 2H SnS2() polytype, where such emission is nominally forbidden by symmetry. It is argued that the underlying symmetry breaking arises due to the presence of stacking faults that are known to be ubiquitous in SnS2single crystals and construct a possible structural model of a stacking fault with symmetry properties consistent with the experimental observations. In addition to shift current, it is observed THz emission by optical rectification excited by below band gap (800 nm; 1.55 eV) pulses but it requires excitation fluence more than two orders of magnitude higher to produce same signal amplitude. These results suggest that ultrafast shift current in which can be excited with visible light in blue–green portion of the spectrum makes SnS2a promising source material for THz photonics.

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