17 research outputs found
Stable Field Emission from Layered MoS2 Nanosheets in High Vacuum and Observation of 1/f Noise
Field emission and current noise of hydrothermally synthesized MoS2 nanosheets are investigated in ultra-high-vacuum and industrially suited high-vacuum conditions. The study reveals that the emission turn-on field is pressure dependent. Moreover, the MoS2 nano‐sheets exhibit more stable field-electron emission in high- vacuum than in ultra-high-vacuum conditions. The investigations on field-emission current fluctuations show features of 1/f-type noise in ultra-high-vacuum and high-vacuum conditions, attributed to adsorption and desorption processes. The post-field-emission results indicate the MoS2 nanosheets are a robust field emitter in high-vacuum conditions
Temperature Dependent Phonon Shifts in Single-Layer WS<sub>2</sub>
Atomically
thin two-dimensional tungsten disulfide (WS<sub>2</sub>) sheets have
attracted much attention due to their potential for future nanoelectronic
device applications. We report first experimental investigation on
temperature dependent Raman spectra of single-layer WS<sub>2</sub> prepared using micromechanical exfoliation. Our temperature dependent
Raman spectroscopy results shows that the E<sup>1</sup><sub>2g</sub> and A<sub>1g</sub> modes of single-layer WS<sub>2</sub> soften as
temperature increases from 77 to 623 K. The calculated temperature
coefficients of the frequencies of 2LA(M), E<sup>1</sup><sub>2g</sub>, A<sub>1g</sub>, and A<sub>1g</sub>(M) + LA(M) modes of single-layer
WS<sub>2</sub> were observed to be −0.008, −0.006, −0.006,
and −0.01 cm<sup>–1</sup> K<sup>–1</sup>, respectively.
The results were explained in terms of a double resonance process
which is active in atomically thin nanosheet. This process can also
be largely applicable in other emerging single-layer materials