THESIS
2016
xiii, 94 pages : illustrations ; 30 cm
Abstract
Since the disclosure of the excellent carrier mobility in ultrathin monolayer graphene in
2004, an astounding amount of attention in the area of ultrathin two-dimensional (2D)
semiconductor materials has been aroused. Molybdenum disulfide (MoS
2), as a typical
member of 2D transition-metal dichalcogenides (TMDs), has attracted significant research
interest due to it prevailing over graphene in terms of acquiring a semiconducting band gap
with layer-number-dependent properties. Most of the findings on MoS
2-based devices were
usually firstly demonstrated by exfoliated MoS
2 because this is a fast and easy method of
investigating the properties of MoS
2 prototypes. Nevertheless, devices fabricated using
micro-mechanical exfoliation or layer transfer are not preferred in manufacturing...[
Read more ]
Since the disclosure of the excellent carrier mobility in ultrathin monolayer graphene in
2004, an astounding amount of attention in the area of ultrathin two-dimensional (2D)
semiconductor materials has been aroused. Molybdenum disulfide (MoS
2), as a typical
member of 2D transition-metal dichalcogenides (TMDs), has attracted significant research
interest due to it prevailing over graphene in terms of acquiring a semiconducting band gap
with layer-number-dependent properties. Most of the findings on MoS
2-based devices were
usually firstly demonstrated by exfoliated MoS
2 because this is a fast and easy method of
investigating the properties of MoS
2 prototypes. Nevertheless, devices fabricated using
micro-mechanical exfoliation or layer transfer are not preferred in manufacturing as the
processes involved are complicated and result in an uncertain size, layer number and location
of transferred MoS
2. Chemical vapor deposition (CVD) has been indicated as a reliable and
promising synthesis method of MoS
2 with a comparable electrical performance to that of its
natural crystals. This method can be used for deposited monolayers, discrete triangular
islands and also continuous films from thin layers to thick layers.
In this thesis, MoS
2 isolated triangular islands on SiO
2/Si substrate and large area
continuous thin film on SiO
2/p-GaN/Si substrate were grown independently using selectable CVD growth of MoS
2 in a home-built furnace set-up. Back-gated FETs as well as top-gated
FETs based on as-grown MoS
2 triangular islands were fabricated and investigated on SiO
2/Si
substrate, while top-gated FETs and semiconductor/insulator/semiconductor (SIS)
heterojunction diodes constructed from as-grown MoS
2 few-layer film were also prepared
and studied on SiO
2/p-GaN/Si substrate. The FET devices on both substrates show a clear
current saturation characteristic, which is crucial for its utilization in most circuit applications.
For the SIS heterojunction diodes on SiO
2/p-GaN/Si substrate, clear current-rectifying
characteristics were shown, which are barely seen for devices based on as-grown MoS
2
without layer transfer. This sheds light on future applications for large scale 2D
heterostructure devices.
Post a Comment