The Effect of Surface Energy on Atomic Layer Deposited Al2O3 Dielectric on MoS2 crystals

Molybdenum disulfide (MoS₂) is a promising two-dimensional semiconductor for thin-film transistors (TFTs) because of the high field-effect mobility, low subthreshold swing, and high on/off ratio. For the fabrication of high-performance MoS₂ TFTs, it is essential to integrate a high dielectric constant (high-k) gate insulator such as HfO₂ or Al₂O₃ on MoS₂. However, the absence of dangling bonds or functional groups on MoS₂ basal plane often requires the pretreatment of MoS₂ surface by O₂ plasma or ultraviolet (UV)-O₃, which will inevitably influence the surface energy. In this presentation, we report a systematic investigation on the effect of MoS₂ surface energy on the atomic layer deposited (ALD) Al₂O₃. We correlate the surface coverage and morphology of ALD Al₂O₃ dielectric with the MoS₂ surface energy based on the measurement with scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. We also provide electrical properties of functionalized Al₂O₃/MoS₂ interface with current-voltage (I-V) and capacitance-voltage (C-V) characteristics.