Plasmonic hot electrons are electrons with high kinetic energy, generated from the
plasmonic nanostructures. The application of hot electrons has been widely studied in the
community of photochemistry and optoelectronics. Many applications like photoelectrochemistry
and photodetector involve semiconductors, and these applications are plagued by low hot
electron injection efficiency in the metal-semiconductor junctions which hinders the wider
applications for the hot electrons.
Since the exfoliation of graphene with scotch tape in 2004, two dimensional (2D) materials
have been widely studied for their unique properties when the thickness scales down to atomically
thin. Transition metal dichalcogenides are a class 2D materials, they are semiconductors, and
they have the different band structures with different material compositions. For each type of the
transition metal dichalcogenide, its few-layer counterparts have both direct band transition and
the indirect band transition, this unique band structure of the few-layer 2D transition metal
dichalcogenides opens up the possibilities for studying the relationship between the hot electron
injection and the band structure in the metal-semiconductor junction.
Inspired by the unique band structure of the 2D semiconductors, we design the structure
formed with plasmonic nanostructures and 2D semiconductors as a model system to explore
plasmonic hot electron injection process at the metal-semiconductor junction, in which we employ
high mobility 2D semiconductor to capture the hot electrons. Due to the high photoluminescence
quantum yield WSe2, photoluminescence spectra are sued to probe the hot electron injection
mechanism between the gold and few-layer WSe2. We demonstrated that the hot electrons tend
to at first inject into the energy lower L point, and then to the K point of the of the few-layer WSe2.
Another question considered in this dissertation is how to modulate the hot electron
injection to improve hot electron collection in the semiconductor. We employed self-assembled
monolayer alkane thiols with different chain lengths as the interlayer, and polymethyl methacrylate
(PMMA) as protection layer to tune hot electron transfer process. The insight derived provides
valuable guidance for the rational design and performance optimization of the relevant plasmonic
hot electron devices.