In this thesis, the electronic and optical properties of MoS2 is studied. MoS2 TFTs by using SiO2 and h-BN substrate are fabricated. Finally, MoS2 rectifying diode and MoS2-BP heterostructure n-p junction would also be fabricated.
In Chapter 3, the MoS2 film thickness are calibrated and measured by optical microscopy and AFM. The optical and vibrational properties of MoS2 are explored by Raman and PL spectra. XPS is not only used to study the stability issue of ambient water and oxygen on MoS2 surface but also measured the fermi level shift before and after the RIE doping for MoS2 film. It shows that the Fermi level of MoS2 film would shift about 0.4 eV toward the valence band after RIE doping by using CHF3 plasma. Finally, UPS is also used to study the work function difference before and after RIE doping for MoS2
film.
In Chapter 4, back-gated MoS2 TFTs using SiO2 and h-BN substrate are fabricated.
Ohmic contacts are achieved by both substrates. MoS2 TFT on h-BN substrate shows better mobility and lower hysteresis which is 63.5 cm2/V-s and 0 V than that MoS2 TFT on SiO2 substrate which is 21.0 cm2/V-s and 46.2 V. The best mobility of MoS2 TFT on h-BN substrate is up to 117 cm2/V-s. In order to further discuss the mechanism of the
hysteresis, MoS2 TFT on SiO2 substrate is measured in atmosphere and vacuum after annealing in N2 at 200℃. It shows that the molecules such as H2O and O2 absorbed on MoS2 surface would not cause hysteresis and the molecules between MoS2 and SiO2
interface would cause hysteresis seriously. However, the molecules such as H2O and O2
absorbed on MoS2 surface would degrade the characteristics of MoS2 TFT. Therefore, the h-BN passivation layer is used to passivated the MoS2 TFT and it shows it has better reliability and stability by using h-BN passivation layer. Finally, the MoS2 rectifying diode which is used RIE to generate p-region and MoS2-BP heterostructure n-p junction are fabricated. The ideality factor is 2.44 for MoS2 rectifying diode and 1.84 for MoS2 -BP heterostructure n-p junction. By using Xe lamp to measure optical properties, although the responsivity of MoS2 rectifying diode is better than that of MoS2-BP heterostructure n-p junction, MoS2-BP heterostructure n-p junction has better photodetect ability than that of MoS2 rectifying diode.
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