Flux-grown large Ti3AlC2 single crystals with well-defined structural and electronic properties toward millimetre-scale MXenes

Dataset containing raw and processed experimental data supporting the study on the growth of large, high-quality Ti3AlC2 single crystals using a TiAl3 flux-based synthesis route and their conversion to millimetre-scale Ti3C2Tx MXenes. The data cover materials synthesis, structural characterization, morphology, electronic and optical properties, and theoretical modeling, as described in the manuscript. The associated article abstract: Ti3AlC2, a typical MAX phase compound, serves as the parent structure of Ti3C2Tx MXenes, the most extensively studied member of the MXene family for diverse applications. Despite the growing interest, most experimental studies on Ti3AlC2 rely on polycrystalline samples, limiting the accurate determination of its intrinsic physical properties. The synthesis of large, high-quality single crystals remains a significant challenge, yet it is essential for probing fundamental electronic, optical, and transport behaviours. In this work, we report the first successful growth of high-quality centimetre-scale Ti3AlC2 single crystals via a TiAl3 flux-based approach. The crystals exhibit excellent structural quality, with individual flakes exceeding 1 cm in length and basal-plane surface areas reaching up to ~36 mm2. Hall measurements on individual flakes reveal a high carrier density of ~10²¹ cm⁻³, while polarisation-resolved Raman spectra show a nearly circular intensity pattern, indicating optical isotropy within the basal plane. To investigate surface characteristics, scanning tunnelling microscopy was performed on freshly cleaved crystals, revealing non-flat surface topography influenced by cleavage termination. First-principles calculations indicate that cleavage predominantly occurs between Ti–Al layers and reveal distinct surface-dependent band structures and Fermi surfaces. Chemical etching of these MAX phase crystals yields millimetre-scale Ti3C2Tx flakes, which can be mechanically exfoliated onto chips. Raman spectra exhibit a strong G-band peak at ~1550 cm⁻¹, with no discernible D-band, indicating low-defect sp²-like carbon structures. Two-terminal devices fabricated from these flakes display symmetric I–V characteristics and negligible gate modulation across 2.5 μm channels, confirming metallic behaviour and good electrical contact. This work establishes a scalable route to large Ti3AlC2 single crystals, offering new insights into their intrinsic properties and laying a solid foundation for future MXene-based device technologies.