TY - JOUR
T1 - Optical, Structural, and Charge Transport Properties of Individual Ti3C2TxMXene Flakes via Micro-Ellipsometry and Beyond
AU - Kenaz, Ralfy
AU - Ghosh, Saptarshi
AU - Lounasvuori, Mailis
AU - Sharma, Namrata
AU - Remennik, Sergei
AU - Vakahi, Atzmon
AU - Steinberg, Hadar
AU - Petit, Tristan
AU - Rapaport, Ronen
AU - Furchner, Andreas
N1 - Publisher Copyright:
© 2025 The Authors. Published by American Chemical Society
PY - 2025/10/14
Y1 - 2025/10/14
N2 - MXenes have attracted significant attention in recent years due to their remarkable properties for electrochemical and optoelectronic applications. While the physical properties of MXene thin films, consisting of stacked delaminated flakes, have been extensively studied, the intrinsic MXene properties can only be derived from individual flakes. Indeed, flake interconnectivity, intercalated species, and film morphology introduce extrinsic factors that affect charge transport and optical properties. In this work, we quantitatively characterize the intrinsic optical, structural, and transport properties of micrometer-sized Ti3C2TxMXene flakes by employing our non-invasive, advanced spectroscopic micro-ellipsometry (SME) technique in the visible–near-infrared spectral range. SME exploits back-focal-plane imaging in a reflection microscopy geometry to simultaneously capture the spectral and incidence-angle-dependent optical response of individual flakes with up to diffraction-limited lateral resolution. Through a comprehensive multi-flake analysis, encompassing flakes from mono- to 32 layers, we reveal thickness-dependent variations in the complex refractive index and charge transport properties of ultrathin flakes, where resistivity increases as the number of Ti3C2Txlayers (NoLs) decreases. Flake thicknesses, non-uniformities, and NoLs, determined via SME with sub-nm precision, closely match nanoscale observations from atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). Additionally, charge transport properties derived from SME agree with four-probe measurements performed on single-flake devices. Unveiling the intrinsic optical, structural, and charge transport properties of Ti3C2TxMXene single flakes, this study establishes SME as a robust platform for quantitative MXene analyses, enabling precise optical metrology of MXene-based optoelectronic and electrochemical devices.
AB - MXenes have attracted significant attention in recent years due to their remarkable properties for electrochemical and optoelectronic applications. While the physical properties of MXene thin films, consisting of stacked delaminated flakes, have been extensively studied, the intrinsic MXene properties can only be derived from individual flakes. Indeed, flake interconnectivity, intercalated species, and film morphology introduce extrinsic factors that affect charge transport and optical properties. In this work, we quantitatively characterize the intrinsic optical, structural, and transport properties of micrometer-sized Ti3C2TxMXene flakes by employing our non-invasive, advanced spectroscopic micro-ellipsometry (SME) technique in the visible–near-infrared spectral range. SME exploits back-focal-plane imaging in a reflection microscopy geometry to simultaneously capture the spectral and incidence-angle-dependent optical response of individual flakes with up to diffraction-limited lateral resolution. Through a comprehensive multi-flake analysis, encompassing flakes from mono- to 32 layers, we reveal thickness-dependent variations in the complex refractive index and charge transport properties of ultrathin flakes, where resistivity increases as the number of Ti3C2Txlayers (NoLs) decreases. Flake thicknesses, non-uniformities, and NoLs, determined via SME with sub-nm precision, closely match nanoscale observations from atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). Additionally, charge transport properties derived from SME agree with four-probe measurements performed on single-flake devices. Unveiling the intrinsic optical, structural, and charge transport properties of Ti3C2TxMXene single flakes, this study establishes SME as a robust platform for quantitative MXene analyses, enabling precise optical metrology of MXene-based optoelectronic and electrochemical devices.
KW - 2D materials
KW - TiCTMXenes
KW - charge transport
KW - dielectric function
KW - micro-ellipsometry
KW - optical constants
KW - structural properties
UR - https://www.scopus.com/pages/publications/105018670408
U2 - 10.1021/acsnano.5c06938
DO - 10.1021/acsnano.5c06938
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C2 - 41026932
AN - SCOPUS:105018670408
SN - 1936-0851
VL - 19
SP - 35414
EP - 35424
JO - ACS Nano
JF - ACS Nano
IS - 40
ER -