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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 7 — Mar. 26, 2012
  • pp: 6974–6979
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Fast visible light photoelectric switch based on ultralong single crystalline V2O5 nanobelt

Jianing Lu, Ming Hu, Ye Tian, Chuanfei Guo, Chuang Wang, Shengming Guo, and Qian Liu  »View Author Affiliations


Optics Express, Vol. 20, Issue 7, pp. 6974-6979 (2012)
http://dx.doi.org/10.1364/OE.20.006974


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Abstract

A photoelectric switch with fast response to visible light (<200μs), suitable photosensitivity and excellent repeatability is proposed based on the ultralong single crystalline V2O5 nanobelt, which are synthesized by chemical vapor deposition and its photoconductive mechanism can well be explained by small polaron hopping theory. Our results reveal that the switch has a great potential in next generation photodetectors and light-wave communications.

© 2012 OSA

1. Introduction

Recently, V2O5 nanowires have been extensively studied because of their promising applications in lithium-ion batteries, field-emitters, waveguide and so on [4

4. L. Q. Mai, X. Xu, L. Xu, C. H. Han, and Y. Z. Luo, “Vanadium oxide nanowires for Li-ion batteries,” J. Mater. Res. 26(17), 2175–2185 (2011). [CrossRef]

6

6. B. Yan, L. Liao, Y. M. You, X. J. Xu, Z. Zheng, Z. X. Shen, J. Ma, L. M. Tong, and T. Yu, “Single crystalline V2O5 ultralong nanoribbon waveguides,” Adv. Mater. (Deerfield Beach Fla.) 21(23), 2436–2440 (2009). [CrossRef]

]. Here we report a photoelectric switch with fast response time to visible light (<200μs), based on high-quality ultralong single crystalline V2O5 nanobelt (20–500nm wide, several centimeters long; aspect ratio >105) fabricated by using chemical vapor deposition (CVD), in which Vanadium powder is initially used instead of conventional VO2 or V2O5 powder to make the fabrication easier, more timesaving and less harmful. Moreover, a switching test circuit, including a LED light, displays the practicality of the switch (Fig. 1
Fig. 1 Single-frame excerpts from video recordings (Media 1) of V2O5 nanobelt photoelectric switching test. (a) and (b) The LED is turned on/off when the red laser (671nm) irradiates on/off the switch. (c) and (d) The LED is turned on/off when the green laser (532nm) irradiates on/off the switch.
, single-frame excerpts from Media 1).

2. Experiments

V2O5 nanobelts were grown by CVD. Vanadium powder (0.5 g, 99.9%) was placed at the center of a horizontal vacuum tube (vacuumized to 4.6 × 10−3 Pa) furnace as a source. By directly heating the source to 1000 °C at 1000 Pa with an Ar/O2 gas flow of 4.8 SCCM (standard cubic centimeter per minute) and 0.2 SCCM, respectively, for duration of 5h, V2O5 nanobelts were grown at Si substrate downstream in a lower temperature region 16 cm from the source. The synthesized products were characterized by a field emission scanning electron microscope (FE-SEM)(Hitachi S4800) and a transmission electron microscope (Tecnai G2 F20 U-TWIN) equipped with selected-area electron diffraction (SAED).

For electrical transport measurements, the ultralongV2O5 nanobelts were first dispersed on a SiO2 (200nm thick)/Si wafer with a desired density. Two electrodes together with their bonding pads were patterned by UV lithography. After the development, a Ti/Au (10 nm/100 nm) film was deposited on the structure followed by a lift-off process. The single V2O5 nanobelt device had a channel length of 2 mm.

The spectral responses for different wavelengths (365-680 nm) were recorded at room temperature by measuring a DC current, by means of using a 50W xenon lamp (the relative xenon lamp light distribution is considered and normalized) and a visible light spectrometer. The bias voltage is 1V.

A red laser with a 671 nm wavelength in continuous wave operation (and a green laser with a 532 nm wavelength was used as substitute) and an Acoustic Optic Modulator with 30 ns pulse were used to test the photoresponse speed. The circuit was supplied by 2 V constant voltage source. To detect the current changing, V2O5 nanobelt was in series with a 1 KΩ resistor which was far less than the resistance of the nanobelt. Thus, the V2O5 nanobelt was under the constant bias of 2V. A low-noise voltage preamplifier (SR 560 with 1MHz bandwidth) was used to amplify the voltage of the 1 KΩ resistor, and connected to the oscilloscope (Tektronix DPO 4104 with 1GHz bandwidth) to acquire the response curve. The whole test was at room temperature in air.

3. Results and discussion

3.1 The morphologies and crystallinity of the V2O5 nanobelts

The photograph of the V2O5 nanobelts is shown in Fig. 2(a)
Fig. 2 (a) The centimeter-scale single crystalline V2O5 nanobelts. (b) SEM image of the V2O5 nanobelts. The inset is the cross section of a V2O5 nanobelt. (c) TEM image of a V2O5 nanobelt. (d) HRTEM image of a V2O5 nanobelt. The insert shows selected area electron diffraction pattern indexed with the [010] zone axis.
. At the edge of the substrate, most of them are with a length up to several centimeters, which suits for tailoring and constructing practical switch. Figure 2(b) and its inset exhibit the FE-SEM images which demonstrate that the V2O5 nanobelts have very smooth surfaces, which correspond to specific crystallographic planes. An individual nanobelt in Fig. 2(c) was further investigated by high resolution transmission electron microscopy (HRTEM) as shown in Fig. 2(d). The well-resolved lattice fringes of (200) planes of the orthorhombic V2O5 with the interplanar distance of 0.58 nm reflect that the V2O5 nanobelt is single crystallinity one grown along the [001] direction. The inset of Fig. 2(d) depicts the SAED pattern of the nanobelt, the diffraction spots could be indexed to the {200}, {101}, {1¯01} families of orthorhombic V2O5 structure.

3.2 The performance of the photoelectric switch based on V2O5 nanobelt

As mentioned earlier, photosensitivity, photoresponse speed and repeatability are often used to judge performance of a photoelectric switch. We fabricated the metal contacts by photolithography to make a photoelectric switch based on a V2O5 nanobelt for these measurements.

3.2.1 Photosensitivity

The photosensitivity is usually described by spectra response and radiation-intensity response, and it is defined as
Rλ=(IphID)/PλS=I/PλS
(1)
where Rλ refers to the photosensitivity, Iph the current under the light irradiation, ID the dark current, I the photocurrent, Pλ the light power density, and S the laser facula area. Figure 3(a)
Fig. 3 (a) Testing scheme of spectra response. (b) The spectra response of the V2O5 nanobelt at different wavelengths (365-680 nm). (c) I–V curves of nanobelts unirridiated and irradiated with constant laser (671 nm and 532 nm) power density of 30.57 mW cm−2. (d) Curves of photocurrent versus light power density at deferent wavelength.
is the testing scheme of the spectra response for different wavelengths (365-680 nm). The result as shown in Fig. 3(b) indicates that the photosensitivity of the nanobelt increases with an increase in wavelength. Since measurements were performed at a constant light power density, the photon density decreases as the wavelength decreases. Consequently the photon-induced carrier concentration also decreases. However, the photosensitivity normalized for constant photon density drops to about zero at short wavelengths, suggesting that photons of higher energies are preferentially adsorbed at or near the semiconductor surface where the recombination rate is much higher [7

7. N. V. Joshi, Photoconductivity: Art, Science, and Technology (Marcel Dekker, 1990), Chap. 1.

]. Figure 3(c) shows the current Iph under laser irradiation increases by 1.85 times (671nm) and 1.65 times (532nm) than the dark current ID for a laser power density of 30.57 mW cm−2. Radiation-intensity response experiment shows from Fig. 3(d) that photocurrent (I) is nearly saturated when power density exceeds 10 mW cm−2, indicating a wide power density range for working.

3.2.2 Photoresponse speed

I=Imax[1exp(t/τr)]
(2)
I=Imaxexp(t/τd)
(3)

Figures 4(b) and 4(c) reveal the photocurrent (the data are normalized to the highest photocurrent under laser irradiation) of the red laser (671 nm) can repeatedly switch at different light power density. Both the rising and falling edges of the V2O5 nanobelt can be well fitted by the relationship mentioned above. The photocurrent of the V2O5 nanobelt also depends on light power density. Figures 4(b)-(d) show the photocurrent of the nanobelt irradiated with light (wavelength 671 nm) power density for 2.55, 5.10, 10.19, 15.29, 20.38 and 30.57 mW cm–2, respectively. The photocurrent increases by small margin as the light power density rises up, especially for light power density of above 10.19 mW cm−2. Fitting the data from Fig. 4(b)-(c), the photoresponse time of the V2O5 nanobelt photoelectric switch under different light power density (red laser with a wavelength of 671 nm) is shown in Table 1

Table 1. Response Time for Red Laser (671nm) and Green Laser (532nm)

table-icon
View This Table
. In contrast with the red laser, the relevant photoresponse time of the V2O5 nanobelts under green laser (wavelength 532 nm) irradiation is also shown in Table 1, respectively. Generally, although the photoresponse time under red laser irradiation is a little shorter than that under the green laser irradiation, they are of the same magnitude (100 μs to 300 μs). The time is shorter by 2–6 orders of magnitude than that of the existing 1D metal-oxide nanostructures under the visible light irradiation [8

8. L. C. Hsu, Y. P. Kuo, and Y. Y. Li, “On-chip fabrication of an individual α-Fe2O3 nanobridge and application of ultrawide wavelength visible-infrared photodetector/optical switching,” Appl. Phys. Lett. 94(13), 133108 (2009). [CrossRef]

11

11. X. Y. Xue, T. L. Guo, Z. X. Lin, and T. H. Wang, “Individual core-shell structured ZnSnO3 nanowires as photoconductors,” Mater. Lett. 62(8–9), 1356–1358 (2008). [CrossRef]

]. Even though we break through wavelength limit, the rapidest response time, so far, based on a ZnO Nanowire photodetector can only reach 0.4 ms under UV illumination [12

12. J. B. K. Law and J. T. L. Thong, “Simple fabrication of a ZnO nanowire photodetector with a fast photoresponse time,” Appl. Phys. Lett. 88(13), 133114 (2006). [CrossRef]

]. It should also be noted that the photoresponse speed is meaningful and efficient only when photoresponse time can follow switching frequencies. Additionally, decrease of photocurrent for an excellent switch should not be lower than 50% for a desired switching frequency. The photoelectric switch is found to work with excellent stability in a wide frequency range. For a certain light power density, the photocurrent (I) decreases by <10% when the frequency changes from 10 [Fig. 4(b)] to 1000 Hz [Fig. 4(c)]. As depicted in Fig. 4(d), the device still function well ((I5000Hz - I10Hz) / I10Hz > 70%) for a switching frequency up to 5000 Hz.

3.2.3 Switching repeatability

Beside the photosensitivity and photoresponse speed, an excellent switching repeatability is another important parameter for a practical switch. As shown above [Figs. 4(b)-(d)], after all switching frequencies and light power densities, the photoelectric switch still function well. Moreover, although millions of times of switching and several hours continuous irradiation (repeat every week and last for two months) have been carried out, the photocurrent of V2O5 nanobelt has little change.

3.3 Photoconductive mechanism

4. Conclusion

In summary, a visible light photoelectric switch has been investigated based on the centimeter-scale single crystalline V2O5 nanobelts fabricated by CVD, in which the Vanadium powder was used for making the fabrication easier, timesaving and less harmful. The excellent photosensitivity, photoresponse speed and repeatability of the switch indicate that it is a good candidate of photoelectric switches for photodetectors and light-wave communications. Particularly, photoresponse time of the photoelectric switch can be shorter than 200 μs, which is 2–6 orders of magnitude shorter than other 1D metal-oxide nanostructures under visible light irradiation.

Acknowledgment

This work is supported by NSFC (10974037, 61006078), NBRPC (2010CB934102), the International S&T Cooperation Project (2010DFA51970), and the Eu-FP7 Project (No. 247644).

References and links

1.

Y. Jiang, W. J. Zhang, J. S. Jie, X. M. Meng, X. Fan, and S. T. Lee, “Photoresponse properties of CdSe single-nanoribbon photodetectors,” Adv. Funct. Mater. 17(11), 1795–1800 (2007). [CrossRef]

2.

E. Comini, G. Baratto, G. Faglia, M. Ferroni, A. Vomiero, and G. Sberveglieri, “Quasi-one dimensional metal oxide semiconductors: preparation, characterization and application as chemical sensors,” Prog. Mater. Sci. 54(1), 1–67 (2009). [CrossRef]

3.

T. Zhai, X. Fang, M. Liao, X. Xu, H. Zeng, B. Yoshio, and D. Golberg, “A comprehensive review of one-dimensional metal-oxide nanostructure photodetectors,” Sensors (Basel Switzerland) 9(8), 6504–6529 (2009). [CrossRef]

4.

L. Q. Mai, X. Xu, L. Xu, C. H. Han, and Y. Z. Luo, “Vanadium oxide nanowires for Li-ion batteries,” J. Mater. Res. 26(17), 2175–2185 (2011). [CrossRef]

5.

T. Y. Zhai, H. M. Liu, H. Q. Li, X. S. Fang, M. Y. Liao, L. Li, H. S. Zhou, Y. Koide, Y. Bando, and D. Golberg, “Centimeter-long V2O5 nanowires: from synthesis to field-emission, electrochemical, electrical transport and photoconductor properties,” Adv. Mater. (Deerfield Beach Fla.) 22(23), 2547–2552 (2010). [CrossRef]

6.

B. Yan, L. Liao, Y. M. You, X. J. Xu, Z. Zheng, Z. X. Shen, J. Ma, L. M. Tong, and T. Yu, “Single crystalline V2O5 ultralong nanoribbon waveguides,” Adv. Mater. (Deerfield Beach Fla.) 21(23), 2436–2440 (2009). [CrossRef]

7.

N. V. Joshi, Photoconductivity: Art, Science, and Technology (Marcel Dekker, 1990), Chap. 1.

8.

L. C. Hsu, Y. P. Kuo, and Y. Y. Li, “On-chip fabrication of an individual α-Fe2O3 nanobridge and application of ultrawide wavelength visible-infrared photodetector/optical switching,” Appl. Phys. Lett. 94(13), 133108 (2009). [CrossRef]

9.

L. Peng, J. L. Zhai, D. J. Wang, P. Wang, Y. Zhang, S. Pang, and T. F. Xie, “Anomalous photoconductivity of cobalt-doped zinc oxide nanobelts in air,” Chem. Phys. Lett. 456(4–6), 231–235 (2008). [CrossRef]

10.

Y. J. Chen, C. L. Zhu, M. S. Cao, and T. H. Wang, “Photoresponse of SnO2 nanobelts grown in situ on interdigital electrodes,” Nanotechnology 18(28), 285502 (2007). [CrossRef]

11.

X. Y. Xue, T. L. Guo, Z. X. Lin, and T. H. Wang, “Individual core-shell structured ZnSnO3 nanowires as photoconductors,” Mater. Lett. 62(8–9), 1356–1358 (2008). [CrossRef]

12.

J. B. K. Law and J. T. L. Thong, “Simple fabrication of a ZnO nanowire photodetector with a fast photoresponse time,” Appl. Phys. Lett. 88(13), 133114 (2006). [CrossRef]

13.

J. Muster, G. T. Kim, V. Krstic, J. G. Park, Y. W. Park, S. Roth, and M. Burghard, “Electrical transport through individual Vanadium Pentoxide nanowires,” Adv. Mater. (Deerfield Beach Fla.) 12(6), 420–424 (2000). [CrossRef]

14.

T. M. Searle and B. Bowler, “Optical study of the excited state of the V′ centre in MgO,” J. Phys. Chem. Solids 32(3), 591–602 (1971). [CrossRef]

15.

N. F. Mott and A. M. Stoneham, “The lifetime of electrons, holes and excitons before self-trapping,” J. Phys. C Solid State Phys. 10(17), 3391–3398 (1977). [CrossRef]

16.

D. Berben, K. Buse, S. Wevering, P. Herth, M. Imlau, and Th. Woike, “Lifetime of small polarons in iron-doped lithium–niobate crystals,” J. Appl. Phys. 87(3), 1034–1041 (2000). [CrossRef]

OCIS Codes
(040.5150) Detectors : Photoconductivity
(230.0250) Optical devices : Optoelectronics
(250.6715) Optoelectronics : Switching

ToC Category:
Optoelectronics

History
Original Manuscript: December 7, 2011
Revised Manuscript: February 27, 2012
Manuscript Accepted: March 6, 2012
Published: March 12, 2012

Citation
Jianing Lu, Ming Hu, Ye Tian, Chuanfei Guo, Chuang Wang, Shengming Guo, and Qian Liu, "Fast visible light photoelectric switch based on ultralong single crystalline V2O5 nanobelt," Opt. Express 20, 6974-6979 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-7-6974


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References

  1. Y. Jiang, W. J. Zhang, J. S. Jie, X. M. Meng, X. Fan, S. T. Lee, “Photoresponse properties of CdSe single-nanoribbon photodetectors,” Adv. Funct. Mater. 17(11), 1795–1800 (2007). [CrossRef]
  2. E. Comini, G. Baratto, G. Faglia, M. Ferroni, A. Vomiero, G. Sberveglieri, “Quasi-one dimensional metal oxide semiconductors: preparation, characterization and application as chemical sensors,” Prog. Mater. Sci. 54(1), 1–67 (2009). [CrossRef]
  3. T. Zhai, X. Fang, M. Liao, X. Xu, H. Zeng, B. Yoshio, D. Golberg, “A comprehensive review of one-dimensional metal-oxide nanostructure photodetectors,” Sensors (Basel Switzerland) 9(8), 6504–6529 (2009). [CrossRef]
  4. L. Q. Mai, X. Xu, L. Xu, C. H. Han, Y. Z. Luo, “Vanadium oxide nanowires for Li-ion batteries,” J. Mater. Res. 26(17), 2175–2185 (2011). [CrossRef]
  5. T. Y. Zhai, H. M. Liu, H. Q. Li, X. S. Fang, M. Y. Liao, L. Li, H. S. Zhou, Y. Koide, Y. Bando, D. Golberg, “Centimeter-long V2O5 nanowires: from synthesis to field-emission, electrochemical, electrical transport and photoconductor properties,” Adv. Mater. (Deerfield Beach Fla.) 22(23), 2547–2552 (2010). [CrossRef]
  6. B. Yan, L. Liao, Y. M. You, X. J. Xu, Z. Zheng, Z. X. Shen, J. Ma, L. M. Tong, T. Yu, “Single crystalline V2O5 ultralong nanoribbon waveguides,” Adv. Mater. (Deerfield Beach Fla.) 21(23), 2436–2440 (2009). [CrossRef]
  7. N. V. Joshi, Photoconductivity: Art, Science, and Technology (Marcel Dekker, 1990), Chap. 1.
  8. L. C. Hsu, Y. P. Kuo, Y. Y. Li, “On-chip fabrication of an individual α-Fe2O3 nanobridge and application of ultrawide wavelength visible-infrared photodetector/optical switching,” Appl. Phys. Lett. 94(13), 133108 (2009). [CrossRef]
  9. L. Peng, J. L. Zhai, D. J. Wang, P. Wang, Y. Zhang, S. Pang, T. F. Xie, “Anomalous photoconductivity of cobalt-doped zinc oxide nanobelts in air,” Chem. Phys. Lett. 456(4–6), 231–235 (2008). [CrossRef]
  10. Y. J. Chen, C. L. Zhu, M. S. Cao, T. H. Wang, “Photoresponse of SnO2 nanobelts grown in situ on interdigital electrodes,” Nanotechnology 18(28), 285502 (2007). [CrossRef]
  11. X. Y. Xue, T. L. Guo, Z. X. Lin, T. H. Wang, “Individual core-shell structured ZnSnO3 nanowires as photoconductors,” Mater. Lett. 62(8–9), 1356–1358 (2008). [CrossRef]
  12. J. B. K. Law, J. T. L. Thong, “Simple fabrication of a ZnO nanowire photodetector with a fast photoresponse time,” Appl. Phys. Lett. 88(13), 133114 (2006). [CrossRef]
  13. J. Muster, G. T. Kim, V. Krstic, J. G. Park, Y. W. Park, S. Roth, M. Burghard, “Electrical transport through individual Vanadium Pentoxide nanowires,” Adv. Mater. (Deerfield Beach Fla.) 12(6), 420–424 (2000). [CrossRef]
  14. T. M. Searle, B. Bowler, “Optical study of the excited state of the V′ centre in MgO,” J. Phys. Chem. Solids 32(3), 591–602 (1971). [CrossRef]
  15. N. F. Mott, A. M. Stoneham, “The lifetime of electrons, holes and excitons before self-trapping,” J. Phys. C Solid State Phys. 10(17), 3391–3398 (1977). [CrossRef]
  16. D. Berben, K. Buse, S. Wevering, P. Herth, M. Imlau, Th. Woike, “Lifetime of small polarons in iron-doped lithium–niobate crystals,” J. Appl. Phys. 87(3), 1034–1041 (2000). [CrossRef]

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