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201807 https://hdl.handle.net/2286/R.2.N.201807 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2025 126 pages Doctoral Dissertation Academic theses en Hajra, Debarati Tongay, Seth Ariel Ponce, Fernando Botana, Antia Sanchez Singh, Arunima Arizona State University Partial requirement for: Ph.D., Arizona State University, 2025 Field of study: Physics Mn+1Xnenes are the layered Titanium Carbides and/or Nitrides where M is an early transition metal and X is Carbon and/or Nitrogen. Due to its excellent electrical conductivity, Ti3C2Tx, a 2D metal, with surface functionalized group Tx= O, OH and F, is emerging as a potential electrode for optoelectronic devices on conventional semiconductors. Much of the physics of Schottky barrier, which controls the current across the Schottky-interface at the MXene-semiconductor junction is not well-understood till date. This dissertation presents an experimental analysis of Schottky barrier formed at Ti3C2Tx and n-type GaAs interface from temperature-dependent current-voltage relationship. Schottky barrier using two different types of MXene Ti3C2TX: disordered multilayer nanoparticles and azimuthally aligned single-layers of MXene used for this study shows different Schottky barrier heights on n-GaAs. This study leads to the understanding of the factors dominating the Schottky barrier, and hence the current conduction across MXene-based metal-semiconductor interfaces.First, MXene Ti3C2Tx was synthesized in multilayer powder-form with optimal synthesis parameters from parent MAX phase Ti3AlC2 and delaminated into single-layers by intercalation. Characterization of as-synthesized MXene was performed by X-Ray diffraction (XRD), scanning electron microscopy (SEM), electron energy dispersive X-Ray spectroscopy (EDS) and atomic force microscopy (AFM). Second, two types of Schottky-interfaces using multilayer and delaminated Ti3C2TX were formed on n-type GaAs by facile drop-casting method. The current-voltage relationship across the Ti3C2TX/n-GaAs interface were found rectifying for both samples. Schottky Barrier heights at Ti3C2TX/n-GaAs were determined from current-voltage relationships which showed lower barrier heights for the delaminated MXene/n-GaAs Schottky-interfaces. While the multilayer MXene/n-GaAs interface showed an average barrier height of 0.75 eV, the average barrier height at delaminated MXene/n-GaAs interface was found to be 0.63 eV. Based on cross-sectional scanning transmission electron microscopy (STEM), Kelvin probe Force microscopy (KPFM) and annealing experiments, Schottky barrier heights in MXene/n-GaAs systems has been explained by reduced Fermi level pinning (FLP) and interlayer trapped water. Third, inhomogeneity in Schottky barrier height were analyzed by assuming Gaussian distribution model using temperature-dependent current-voltage data. Lastly, self-biased photodetection of both MXene-based diodes was demonstrated under 785nm wavelength. Delaminated MXene-based device shows superior photoresponsivity compared to multilayer MXene-based device. Materials Science Fermi Level Pinning MXene photodetector Schottky Barrier A Comparative Study of Current Conduction Across Multilayer and Delaminated Ti3C2Tx MXene/n-GaAs Schottky Interface and Their Application as Photodetectors