Abstract-Equilibrium and non-equilibrium free carrier dynamics in two-dimensional Ti3C2Tx MXenes: THz spectroscopy study

Guangjiang Li, Kateryna Kushnir, Yongchang Dong, Sergii Chertopalov, Apparao M Rao, Vadym Mochalin, Ramakrishna Podila,  Lyubov Titova

http://iopscience.iop.org/article/10.1088/2053-1583/aacb9e/pdf


MXenes is an emerging class of two-dimensional transition metal carbides, nitrides and carbonitrides which exhibit large conductivity, ultrahigh volumetric capacitance, high threshold for light induced damage and nonlinear optical transmittance, making them attractive candidates for a variety of optoelectronic and electrochemical applications. Here, we report on equilibrium and non equilibrium free carrier dynamics of Ti3C2Tx gleaned from THz spectroscopic studies for the first time. Ti3C2TX showed high (~ 2x1021 cm-3) intrinsic charge carrier density and relatively high (~34 cm2/Vs) mobility of carriers with an exceptionally large, ~ 46,000 cm-1 absorption in the THz range, which suggests that Ti3C2Tx is well suited for THz detection. We also demonstrate that Ti3C2Tx conductivity and THz transmission can be manipulated by photoexcitation, as absorption of near-infrared, 800 nm pulses is found to cause transient suppression of the conductivity that recovers over hundreds of picoseconds. The possibility of control over THz transmission and conductivity by photoexcitation suggests the promise for application of Ti3C2Tx Mxenes in THz modulation devices and variable electromagnetic shielding.

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Abstract-Enhanced Terahertz Shielding of MXenes with Nano-Metamaterials

Geunchang Choi, Faisal Shahzad, Young-Mi Bahk, Young Min Jhon, Hyunchul Park, Mohamed Alhabeb, Babak Anasori, Dai-Sik Kim, Chong Min Koo, Yury Gogotsi, Minah Seo,

http://onlinelibrary.wiley.com/doi/10.1002/adom.201701076/full

Terahertz (THz) shielding becomes increasingly important with the growing development of THz electronics and devices. Primarily materials based on carbon nanostructures or polymer–carbon nanocomposites have been explored for this application. Herein, significantly enhanced THz shielding efficiencies for 2D titanium carbide (Ti3C2 MXene) thin films with nanoscale THz metamaterials are presented. Nanoscale slot antenna arrays with strong resonances at certain frequencies enhance THz electromagnetic waves up to three orders of magnitude in transmission, which in turn enormously increases the shielding performance in combination with MXene films. Drop-casting of a colloidal solution of MXene (a few micrograms of dry material) can produce an ultrathin film (several tens of nanometers in thickness) on a slot antenna array. Consequently, THz waves strongly localized in the near-field regime by the slot antenna undergo enhanced absorption through the film with a magnified effective refractive index. Finally, the combination of an ultrathin MXene film and a nano-metamaterial shows excellent shielding performance in the THz range.

Abstract-Enhanced Terahertz Shielding of MXenes with Nano-Metamaterials

Geunchang Choi, Faisal Shahzad, Young-Mi Bahk, Young Min Jhon, Hyunchul Park, Mohamed Alhabeb, Babak Anasori, Dai-Sik Kim, Chong Min Koo, Yury Gogotsi,

http://onlinelibrary.wiley.com/doi/10.1002/adom.201701076/abstract

Terahertz (THz) shielding becomes increasingly important with the growing development of THz electronics and devices. Primarily materials based on carbon nanostructures or polymer–carbon nanocomposites have been explored for this application. Herein, significantly enhanced THz shielding efficiencies for 2D titanium carbide (Ti3C2 MXene) thin films with nanoscale THz metamaterials are presented. Nanoscale slot antenna arrays with strong resonances at certain frequencies enhance THz electromagnetic waves up to three orders of magnitude in transmission, which in turn enormously increases the shielding performance in combination with MXene films. Drop-casting of a colloidal solution of MXene (a few micrograms of dry material) can produce an ultrathin film (several tens of nanometers in thickness) on a slot antenna array. Consequently, THz waves strongly localized in the near-field regime by the slot antenna undergo enhanced absorption through the film with a magnified effective refractive index. Finally, the combination of an ultrathin MXene film and a nano-metamaterial shows excellent shielding performance in the THz range.