Showing papers by "Tsing-Hua Her published in 2019"
TL;DR: These results establish SWCNT films as novel and promising ultrafast photocathode material.
Abstract: Ultrashort bunches of electrons, emitted from solid surfaces through excitation by ultrashort laser pulses, are an essential ingredient in advanced X-ray sources, and ultrafast electron diffraction and spectroscopy. Multiphoton photoemission using a noble metal as the photocathode material is typically used but more brightness is desired. Artificially structured metal photocathodes have been shown to enhance optical absorption via surface plasmon resonance but such an approach severely reduces the damage threshold in addition to requiring state-of-the-art facilities for photocathode fabrication. Here, we report ultrafast photoelectron emission from sidewalls of aligned single-wall carbon nanotubes. We utilized strong exciton resonances inherent in this prototypical one-dimensional material, and its excellent thermal conductivity and mechanical rigidity leading to a high damage threshold. We obtained unambiguous evidence for resonance-enhanced multiphoton photoemission processes with definite power-law beh...
12 citations
05 May 2019
TL;DR: In this paper, the authors report ultrafast photoelectron emission from aligned single-wall carbon nanotubes utilizing strong exciton resonances inherent in this prototypical one-dimensional material.
Abstract: We report ultrafast photoelectron emission from aligned single-wall carbon nanotubes utilizing strong exciton resonances inherent in this prototypical one-dimensional material. These results establish SWCNT films as novel and promising ultrafast photocathode material. © 2019 The Author(s)
Patent•
12 Feb 2019TL;DR: In this paper, the valence band maximum of the second material is higher than a conduction band minimum of the first semiconductor material, thereby allowing a flow of a majority of free carriers across the semiconductor junction between the first and second layers to be diffusive.
Abstract: A semiconductor junction may include a first layer and a second layer. The first layer may include a first semiconductor material and the second layer may be deposited on the first layer and may include a second material. The valence band maximum of the second material is higher than a conduction band minimum of the first semiconductor material, thereby allowing a flow of a majority of free carriers across the semiconductor junction between the first and second layers to be diffusive.
05 May 2019
TL;DR: In this paper, single-shot femtosecond laser ablation of monolayer molybdenum disulfide is demonstrated, and an ablation threshold was found 0.9 nJ/um2' which is too low for two-photon photoionization alone.
Abstract: Single-shot femtosecond laser ablation of monolayer molybdenum disulfide is demonstrated. An ablation threshold was found 0.9 nJ/um2’, which is too low for two-photon photoionization alone. We show that surface defects and avalanche ionization are important. © 2019 The Author(s)