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Photoresponsive and gas sensing field-effect transistors based on multilayer WS₂ nanoflakes.

Huo N, Yang S, Wei Z, Li SS, Xia JB, Li J - Sci Rep (2014)

Bottom Line: The photoelectrical properties of multilayer WS₂ nanoflakes including field-effect, photosensitive and gas sensing are comprehensively and systematically studied.The ethanol and NH₃ molecules can serve as electron donors to enhance the Rλ and EQE significantly.Under the NH3 atmosphere, the maximum Rλ and EQE can even reach 884 A/W and 1.7 × 10(5)%, respectively.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of SciencesP.O. Box 912, Beijing 100083, China.

ABSTRACT
The photoelectrical properties of multilayer WS₂ nanoflakes including field-effect, photosensitive and gas sensing are comprehensively and systematically studied. The transistors perform an n-type behavior with electron mobility of 12 cm(2)/Vs and exhibit high photosensitive characteristics with response time (τ) of <20 ms, photo-responsivity (Rλ) of 5.7 A/W and external quantum efficiency (EQE) of 1118%. In addition, charge transfer can appear between the multilayer WS₂ nanoflakes and the physical-adsorbed gas molecules, greatly influencing the photoelectrical properties of our devices. The ethanol and NH₃ molecules can serve as electron donors to enhance the Rλ and EQE significantly. Under the NH3 atmosphere, the maximum Rλ and EQE can even reach 884 A/W and 1.7 × 10(5)%, respectively. This work demonstrates that multilayer WS₂ nanoflakes possess important potential for applications in field-effect transistors, highly sensitive photodetectors, and gas sensors, and it will open new way to develop two-dimensional (2D) WS₂-based optoelectronics.

No MeSH data available.


Related in: MedlinePlus

The effect of gas molecules on photoresponsive parameters.The column diagram of (a) photosensitive on/off ratio, (b) Rλ and EQE of our device based on the multilayer WS2 nanoflakes at various gas atmospheres. The used incident light is 40 mW/cm2 with wavelength of 633 nm.
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f5: The effect of gas molecules on photoresponsive parameters.The column diagram of (a) photosensitive on/off ratio, (b) Rλ and EQE of our device based on the multilayer WS2 nanoflakes at various gas atmospheres. The used incident light is 40 mW/cm2 with wavelength of 633 nm.

Mentions: The gas molecules play an important role in the photosensitive properties. As on/off ratio, Rλ and EQE are critical parameters to evaluate the performance of a phototransistor, the effects of various gas molecules adsorption on the photosensitive properties are demonstrated with these parameters (Figure 5). Table 2 summarizes the performance parameters of our device at different gas atmospheres. The on/off ratio at all the gas atmospheres is lower than that in vacuum (Figure 5a). As mentioned above, poorly O2 molecules are adsorbed in dark, but the adsorption capacity of O2 is increased under light illumination. Thus, the reduction of photocurrent outweighs the reduction of dark current, leading to the reduced on/off ratio. As high sensitive gases for our device, the ethanol and NH3 have been strongly adsorbed in dark, leading to that the dark current becomes very large. When the light illuminates the device, the proportion of increased photocurrent is smaller among the total current, so that the on/off ratio is also decreased. However, the Rλ and EQE of our device are increased significantly in the presence of the ethanol and NH3 as shown in Figure 5b. The reason is that more ethanol or NH3 molecules will be adsorbed and donate more electrons when the light illuminated the device, and the number of photo-induced electrons detected per incident photons is overall increased. On the contrary, the oxidizing gases like O2 serving as electron acceptors will deplete the photo-induced electrons, leading to the decreased Rλ and EQE. Remarkably, the device even reaches a high Rλ of 884 A/W and EQE of 1.7 × 105 % at low illumination power density (50 μW/cm2) under NH3 atmosphere.


Photoresponsive and gas sensing field-effect transistors based on multilayer WS₂ nanoflakes.

Huo N, Yang S, Wei Z, Li SS, Xia JB, Li J - Sci Rep (2014)

The effect of gas molecules on photoresponsive parameters.The column diagram of (a) photosensitive on/off ratio, (b) Rλ and EQE of our device based on the multilayer WS2 nanoflakes at various gas atmospheres. The used incident light is 40 mW/cm2 with wavelength of 633 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048886&req=5

f5: The effect of gas molecules on photoresponsive parameters.The column diagram of (a) photosensitive on/off ratio, (b) Rλ and EQE of our device based on the multilayer WS2 nanoflakes at various gas atmospheres. The used incident light is 40 mW/cm2 with wavelength of 633 nm.
Mentions: The gas molecules play an important role in the photosensitive properties. As on/off ratio, Rλ and EQE are critical parameters to evaluate the performance of a phototransistor, the effects of various gas molecules adsorption on the photosensitive properties are demonstrated with these parameters (Figure 5). Table 2 summarizes the performance parameters of our device at different gas atmospheres. The on/off ratio at all the gas atmospheres is lower than that in vacuum (Figure 5a). As mentioned above, poorly O2 molecules are adsorbed in dark, but the adsorption capacity of O2 is increased under light illumination. Thus, the reduction of photocurrent outweighs the reduction of dark current, leading to the reduced on/off ratio. As high sensitive gases for our device, the ethanol and NH3 have been strongly adsorbed in dark, leading to that the dark current becomes very large. When the light illuminates the device, the proportion of increased photocurrent is smaller among the total current, so that the on/off ratio is also decreased. However, the Rλ and EQE of our device are increased significantly in the presence of the ethanol and NH3 as shown in Figure 5b. The reason is that more ethanol or NH3 molecules will be adsorbed and donate more electrons when the light illuminated the device, and the number of photo-induced electrons detected per incident photons is overall increased. On the contrary, the oxidizing gases like O2 serving as electron acceptors will deplete the photo-induced electrons, leading to the decreased Rλ and EQE. Remarkably, the device even reaches a high Rλ of 884 A/W and EQE of 1.7 × 105 % at low illumination power density (50 μW/cm2) under NH3 atmosphere.

Bottom Line: The photoelectrical properties of multilayer WS₂ nanoflakes including field-effect, photosensitive and gas sensing are comprehensively and systematically studied.The ethanol and NH₃ molecules can serve as electron donors to enhance the Rλ and EQE significantly.Under the NH3 atmosphere, the maximum Rλ and EQE can even reach 884 A/W and 1.7 × 10(5)%, respectively.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of SciencesP.O. Box 912, Beijing 100083, China.

ABSTRACT
The photoelectrical properties of multilayer WS₂ nanoflakes including field-effect, photosensitive and gas sensing are comprehensively and systematically studied. The transistors perform an n-type behavior with electron mobility of 12 cm(2)/Vs and exhibit high photosensitive characteristics with response time (τ) of <20 ms, photo-responsivity (Rλ) of 5.7 A/W and external quantum efficiency (EQE) of 1118%. In addition, charge transfer can appear between the multilayer WS₂ nanoflakes and the physical-adsorbed gas molecules, greatly influencing the photoelectrical properties of our devices. The ethanol and NH₃ molecules can serve as electron donors to enhance the Rλ and EQE significantly. Under the NH3 atmosphere, the maximum Rλ and EQE can even reach 884 A/W and 1.7 × 10(5)%, respectively. This work demonstrates that multilayer WS₂ nanoflakes possess important potential for applications in field-effect transistors, highly sensitive photodetectors, and gas sensors, and it will open new way to develop two-dimensional (2D) WS₂-based optoelectronics.

No MeSH data available.


Related in: MedlinePlus