Ion Treatments on Two-Dimensional Molybdenum Disulfide

Abstract

Two-dimensional molybdenum disulfide (2D MoS 2 ) has gained significant attention due to its unique electronic and optical properties, making it a promising material for various applications, such as optoelectronic devices and energy storage systems. This thesis investigates methods to enhance the photoluminescence (PL) emission of monolayer MoS 2 through different treatments. The experiments performed aimed to achieve this by creating defects on the crystal structure in a controlled manner, attacking the 2D MoS 2 with ions. The samples were obtained via Chemical Vapor Deposition (CVD). The changes in morphology and electro-optical features were assessed via Atomic Force Microscopy (AFM), Resonant Raman Spectroscopy, and Photoluminescence (PL) Spectroscopy.The first round of experiments employed a Nitrogen Plasma treatment. AFM evidence of the integrity of the morphology is presented, although the PL signal was significantly quenched for the parameters used. Raman Spectroscopy shows an evolution of key features as defects are progressively created, namely the second-order 2LA(K) and 2LA(M) vibrational modes Full Width at Half Maximum (FWHM).Afterwards, a Helium ion beam treatment was applied, yielding positive results when controlling treatment time and energy. Photoluminescence emission spectra revealed the signal intensity was enhanced by up to a factor of 2. Resonant Raman measurements indicated a controlled defect creation was achieved (with practically unchanged second-order features). AFM analysis demonstrated no change in the micrometer scale dut to the treatments. This treatment constitutes a facile method for enhancing CVD grown monolayer MoS 2 samples PL emission for future device applications.