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Enhancement of X-ray detection by single-walled carbon nanotube enriched flexible polymer composite.

Han H, Lee S, Seo J, Mahata C, Cho SH, Han AR, Hong KS, Park JH, Soh MJ, Park C, Lee T - Nanoscale Res Lett (2014)

Bottom Line: However, this benefit was counterbalanced by the slow and unstable time-dependent response at high SWNT concentrations, arising from reduced Schottky barrier heights between the active layer and electrodes.At high SWNT concentration, the dark current also increased due to the reduced Schottky barrier height, leading to decrease the signal-to-noise ratio (SNR) of the device.Experimental results indicated that 0.005 wt.% SWNT in the composite was the optimum composition for practical X-ray detector operation because it showed enhanced performance in both sensitivity and SNR.

View Article: PubMed Central - PubMed

Affiliation: Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 120-749, Republic of Korea, kamacoon@yonsei.ac.kr.

ABSTRACT

Unlabelled: Although organic-based direct conversion X-ray detectors have been developed, their photocurrent generation efficiency has been limited by recombination of excitons due to the intrinsically poor electrical properties of organic materials. In this report, we fabricated a polymer-based flexible X-ray detector and enhanced the X-ray detection sensitivity using a single-walled carbon nanotube (SWNT) enriched polymer composite. When this SWNT enriched polymer composite was used as the active layer of an X-ray detector, it efficiently separated charges at the interface between the SWNTs and polymer, preventing recombination of X-ray-induced excitons. This increased the photocurrent generation efficiency, as measured from current-voltage characteristics. Therefore, X-ray-induced photocurrent and X-ray detection sensitivity were enhanced as the concentration of SWNTs in the composite was increased. However, this benefit was counterbalanced by the slow and unstable time-dependent response at high SWNT concentrations, arising from reduced Schottky barrier heights between the active layer and electrodes. At high SWNT concentration, the dark current also increased due to the reduced Schottky barrier height, leading to decrease the signal-to-noise ratio (SNR) of the device. Experimental results indicated that 0.005 wt.% SWNT in the composite was the optimum composition for practical X-ray detector operation because it showed enhanced performance in both sensitivity and SNR. In mechanical flexibility tests, the device exhibited a stable response up to a bending radius of 0.5 cm, and the device had no noticeable change in diode current after 1,000 bending cycles.

Pacs code: 8.67.Sc.

No MeSH data available.


Device stability tests under various bending conditions. (a) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device as a function of bending radius. The dark current remained similar despite the bending radius, but the X-ray-induced current changed slightly. (b) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device after repeated bending cycles. The device showed a stable response for up to 1,000 bending cycles.
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Fig5: Device stability tests under various bending conditions. (a) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device as a function of bending radius. The dark current remained similar despite the bending radius, but the X-ray-induced current changed slightly. (b) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device after repeated bending cycles. The device showed a stable response for up to 1,000 bending cycles.

Mentions: Figure 5a shows dark currents and X-ray-induced currents of the 0.005 wt.% SWNT device under bending conditions with various radii. In this measurement, the X-ray dose rate was 7 mGy/s and the reverse bias voltage was 120 V. It should be noted that the dark currents exhibited no discriminable response to changes in the bending radius, even though the X-ray-induced currents were slightly changed. The different responses may be attributed to the changes in surface morphology and the effective intensity of X-ray irradiation on the device [26]. Figure 5b shows the bending stability of the device in the same condition as that of Figure 4a. The device was bent 1,000 times, with a bending radius of 0.5 cm in the positive direction, and both dark current and X-ray-induced current were measured after every 100 cycles of bending. These results confirm that the device exhibited a stable X-ray response with good mechanical flexibility.Figure 5


Enhancement of X-ray detection by single-walled carbon nanotube enriched flexible polymer composite.

Han H, Lee S, Seo J, Mahata C, Cho SH, Han AR, Hong KS, Park JH, Soh MJ, Park C, Lee T - Nanoscale Res Lett (2014)

Device stability tests under various bending conditions. (a) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device as a function of bending radius. The dark current remained similar despite the bending radius, but the X-ray-induced current changed slightly. (b) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device after repeated bending cycles. The device showed a stable response for up to 1,000 bending cycles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493992&req=5

Fig5: Device stability tests under various bending conditions. (a) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device as a function of bending radius. The dark current remained similar despite the bending radius, but the X-ray-induced current changed slightly. (b) Dark current and X-ray-induced current of the 0.005 wt.% SWNT device after repeated bending cycles. The device showed a stable response for up to 1,000 bending cycles.
Mentions: Figure 5a shows dark currents and X-ray-induced currents of the 0.005 wt.% SWNT device under bending conditions with various radii. In this measurement, the X-ray dose rate was 7 mGy/s and the reverse bias voltage was 120 V. It should be noted that the dark currents exhibited no discriminable response to changes in the bending radius, even though the X-ray-induced currents were slightly changed. The different responses may be attributed to the changes in surface morphology and the effective intensity of X-ray irradiation on the device [26]. Figure 5b shows the bending stability of the device in the same condition as that of Figure 4a. The device was bent 1,000 times, with a bending radius of 0.5 cm in the positive direction, and both dark current and X-ray-induced current were measured after every 100 cycles of bending. These results confirm that the device exhibited a stable X-ray response with good mechanical flexibility.Figure 5

Bottom Line: However, this benefit was counterbalanced by the slow and unstable time-dependent response at high SWNT concentrations, arising from reduced Schottky barrier heights between the active layer and electrodes.At high SWNT concentration, the dark current also increased due to the reduced Schottky barrier height, leading to decrease the signal-to-noise ratio (SNR) of the device.Experimental results indicated that 0.005 wt.% SWNT in the composite was the optimum composition for practical X-ray detector operation because it showed enhanced performance in both sensitivity and SNR.

View Article: PubMed Central - PubMed

Affiliation: Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 120-749, Republic of Korea, kamacoon@yonsei.ac.kr.

ABSTRACT

Unlabelled: Although organic-based direct conversion X-ray detectors have been developed, their photocurrent generation efficiency has been limited by recombination of excitons due to the intrinsically poor electrical properties of organic materials. In this report, we fabricated a polymer-based flexible X-ray detector and enhanced the X-ray detection sensitivity using a single-walled carbon nanotube (SWNT) enriched polymer composite. When this SWNT enriched polymer composite was used as the active layer of an X-ray detector, it efficiently separated charges at the interface between the SWNTs and polymer, preventing recombination of X-ray-induced excitons. This increased the photocurrent generation efficiency, as measured from current-voltage characteristics. Therefore, X-ray-induced photocurrent and X-ray detection sensitivity were enhanced as the concentration of SWNTs in the composite was increased. However, this benefit was counterbalanced by the slow and unstable time-dependent response at high SWNT concentrations, arising from reduced Schottky barrier heights between the active layer and electrodes. At high SWNT concentration, the dark current also increased due to the reduced Schottky barrier height, leading to decrease the signal-to-noise ratio (SNR) of the device. Experimental results indicated that 0.005 wt.% SWNT in the composite was the optimum composition for practical X-ray detector operation because it showed enhanced performance in both sensitivity and SNR. In mechanical flexibility tests, the device exhibited a stable response up to a bending radius of 0.5 cm, and the device had no noticeable change in diode current after 1,000 bending cycles.

Pacs code: 8.67.Sc.

No MeSH data available.