UCLA

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.