Manipulating Polycrystalline Silicon Nanowire FET Characteristics by

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Manipulating Polycrystalline Silicon Nanowire FET Characteristics by Light Illumination Chien-Hung Chen, Chih-Heng Lin, Yuh-Shyong Yang, and Chi-Hung Hwang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b12631 • Publication Date (Web): 23 Feb 2016 Downloaded from http://pubs.acs.org on February 28, 2016

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The Journal of Physical Chemistry

Manipulating Polycrystalline Silicon Nanowire FET Characteristics by Light Illumination

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Chien-Hung Chen , Chih-Heng Lin , Yuh-Shyong Yang*, Chi-Hung Hwang*,†

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Institute of Biological Science and Technology, National Chiao Tung University,

Hsinchu 300, Taiwan †

Instrument Technology Research Center, National Applied Research Laboratories,

Hsinchu 300, Taiwan

Corresponding authors: E-mail [email protected], Tel: 886-3-5729287 (Y.-S.Y.). E-mail [email protected], Tel: 886-3-5779911 (C.-H.H.).

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ABSTRACT Polycrystalline silicon nanowire field-effect transistor (Poly-SiNW FET) has attracted many attentions in last decade due to its ultrasensitive, label-free, and real-time response for potential sensing applications particular for bio-sensors. In this paper, the changes of the electric characteristic of poly-SiNW FET introduced by light illumination are studied systematically. Particularly, the red light (635 nm) and UV light (365 nm) are employed as light sources. Both lights are projected on the poly-SiNW FETs installed and tested in air or in a vacuum (0.1 Torr) chamber.

The

results show that both light sources can change the electric characteristic of poly-SiNW FET which indicates that the photoelectronic effect can manipulate both n- and p-type device of poly-SiNW FET; meanwhile, results also support the potential of poly-SiNW FET in air and in the vacuum environment for optoelectronic sensing applications.

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INTRODUCTION Polycrystalline silicon (poly-Si) nanostructure has attracted great attention because the poly-Si nanostructure can be manufactured by the conventional Complementary Metal-Oxide Semiconductor (CMOS)-compatible semiconductor process. Over the past decade, nanowires (NWs) have been devoted to the biological applications. Integrating functional units of organisms, such as DNA, proteins, and even the cells, with nanoelectronic elements, yield biochemoelectronic devices which have greater potential for future biomedical applications1-5. also serves as electrics’ pathway.

In practice, the one-dimensional NW

The NWs can integrate with field effect transistor

(FET) into a sensor device for biological and chemical sensing applications. Implementing the poly-SiNW FET device on biological sensing applications have been proposed6-9.

Regarding biological sensing, the bio-receptor is always binding

on the surface of poly-SiNW FET device to catch the specified bio-target. Whenever the target and receptor interaction occurring, the surface electric potential of the NW is changed and the channel conductance must be modulated to conduct the electronic signal to ensure the signal can be detected by detecting circuit or instrument. Considering the electric characteristics of bio-organism units are different when the NW FET device is implemented for biological sensing; in principle, the NW FET characteristics need to be adjusted in advance to have the best detecting performances (highest sensitivity). Whenever the sensing targets are captured by the NWs, the FET electric characteristic is changed and always be treated as a signal which is the common operation principle for sensing applications.

Nevertheless, most of the proposed approaches, such as

NW FET gate voltage adjusting and drain-to-source voltage control are merely applied to contact measurement. For instance, to the best knowledge of authors, there is no research report on the development of poly-SiNW FET for non-contact sensing 3



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application, for example, the light detection; nor about how the light illuminating impacts on contact measurement. Opto-electrical properties of NWs with various materials, such as ZnO, SnO2, CdTe, and InP have been reported10-13. Unfortunately, the mechanism of the photo-effect on poly-SiNW FET is still unclear. In this paper, both n- and p- type poly-SiNW FETs are fabricated and then illuminated with Red light (central wavelength is 635 nm) and UV light (central wavelength is 365 nm) to evaluate the photo-effect on the poly-SiNW FET electric characteristics. Meanwhile, considering the UV light delivery less thermal energy than Red light, the thermal effect on poly-SiNW FET electric characteristic change is investigated by illuminated with UV light and the photo-effect on the poly-SiNW FET in a vacuum chamber is studied to understand the effects of oxygen and moisture on the electric characteristics changes of the n- and p- type poly-SiNW and feasibility to manipulate the poly-SiNW FET by light in the vacuum environment.

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DEVICES PREPARATION AND ELECTRIC CHARACTERISTICS Poly-SiNW FET devices were fabricated by using fully CMOS-compatible processes and facilities in the National Nano Device Laboratories (Hsinchu, Taiwan). Either n-type or a p-type FET consists of two 60 nm wide, around 50 nm height and 1.6 µm long poly-SiNWs which serve as conducting channels fabricated by sidewall spacer technique9, 14-16. Figure1 (a) and (b) show the schematic diagram of NW FET device and an SEM top-view image. The structure of NW FET device was developed with special consideration for applications of biological sensing17-18.

In practice, the

radius of NW is one of the key parameters of the electric characteristics of the NW FET19-20.

The electric characteristic of a typical n-type poly-SiNW FET device used for this study is shown in Fig. 2.

Where Fig. 2(a) shows the log scales electric characteristic

(drain current (IDS) versus gate-source voltage (VGS) curve, IDS–VGS) of n-type poly-SiNW FET determined by increasing back-gate voltage (VGS) from -1 to 3 V with 0.2 V increment per step, and the drain–source voltage (VDS) has been fixed at 0.5 V.

The linear scale IDS–VGS curve is also shown at upper-left corner of Fig. 2(a’).

From Fig. 2 (a), the IDS is increased by increasing VGS, the result shows the electric characteristics of the n-type poly-SiNW FET used for study is similar to the electric characteristic of a typical n-channel enhancement-mode (E-mode) FET. The n-type poly-SiNW FET on-off ratio is about 8.3 × 103 and the threshold voltage, Vth, is about 1.51 V.

The transconductance, gm, of device can be calculated from the following

equation: 5



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g =

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(1)

The transconductance above the Vth is estimated to be 3.52 nS (S, Siemens). The electron mobility (µe) of the poly-SiNW FET device can be calculated according to the following equation 21:

=

g

(2)

Where is the mobilityof SiNW, is the distance between source and drain electrodes, is the diameter of poly-SiNW (1.6 m), and is the gate capacitance per unit area which can be calculated by Equation (3):

!3%

= !"/

%$Here, ℎ is the thickness of the dielectric SiO2 and Si3N4 layer (150 nm), ( is the radius of poly-SiNW (30 nm), ) is the relative dielectric constant of SiO2 () = 3.9) and Si3N4 () = 7.5), and )* is the vacuum dielectric constant (8.85 × 10-12 F m-1). From the Equations (2) and (3) and the data of IDS–VGS curve is plotted in Fig. 2(a), the capacitance and effective mobility of n-type poly-SiNW FET can be estimated to be 1.13 × 10-16 F and 155.75 cm2v-1s-1, respectively.

Figure 2 (b) is the IDS–VGS of p-type poly-SiNW FET in log scales with varied VGS ranging from 1 to -3 V with 0.2 V interval. The linear scale of ID–VG curve with the p-type device is also displayed in inset figure on the upper-left corner of Fig. 2(b). The VDS is also set at 0.5 V. The on-off ratio is about 5.9 × 103, the Vth is about -2.1 V and the gm above the Vth is 103.63 nS.

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RESULTS AND DISCUSSIONS SiNW FET Response to Light Illumination Figure 3 (a) displays the log scales of IDS–VGS curve of n-type poly-SiNW FET at the drain voltage (VDS) is fixed at 0.5 V measured in the dark state and illuminated by a red Light-Emitting Diode (LED); the associated linear scale of IDS–VGS curve is plotted in Fig. 3(a’).

The red LED has 635 nm central wavelength and the power of

light is 258 µW/cm2 which was measured by a power meter (PM100D, Thorlabs). Each time of experiment, the LED will be keeping on around 10 minute for stability of light illumination and installed with holder in order to maintain light source and nanowire at a fixed distance. The power of light will be measured before determination of poly-SiNW FET electric characteristic. Keithley 4200 was employed for I-V curve characteristic determination. As the light illuminates on the n-type poly-SiNW FET, the Vth shifts towards higher gate-bias from around 1.2 V to 1.3 V, the sub-threshold slope decreases from 23.853 to 17.103, and the on-off ratio decreases from around 7270 to 4870. The electric characteristic of p-type poly-SiNW FET illuminated with the same LED and power of light is shown in the Fig. 3 (b) and the corresponding linear scale IDS– VGS curve is plotted in Fig. 3 (b’). The Vth shifts towards positive gate-bias from around -2.5 V to -1.85 V, the sub-threshold slope increases from 3.45 to 35.42, and the on-off of ratio increases from 32.265 to 310.301. Effects of Light Intensity Figure 4(a) is the IDS–VGS curve of n-type poly-SiNW FET illuminated by a red light LED (center wavelength= 635 nm) with different light intensities, the light intensities are varied from dark (LED was turned off), 0.1 µW, 0.2 µW, 1 mW, 1.5 mW, to 2.7 mW and the VDS is set to be 0.5 V. The results show that the Vth of the NW FET is always increased in conjunction with light intensity increased. The Vth of the device 7



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has been shifted by light intensity from around 1.0 V in dark condition to 1.5 V as the NW FET illuminated with 2.7 mW red LED light, and the corresponding on-off ratio decreased from 394 to 216. The electric characteristic reveals that the red light will deteriorate the electric characteristic of n-type NW-FET. Figure 4 (b) shows IDS of n-type poly-SiNW FET versus light intensity with VGS is set to be 3 V. The light intensity is varied from 0 to 2.7 mW. The IDS (nA)-light intensity (mW) curve can be approximated by an exponential function (+,- = ./ 0 1"2 223 , R2=0.974) as the light intensity is less than 1 mW; and the IDS-light intensity curve of n-type poly-SiNW FET is can be approximated by a linear function when the illuminating red LED light power is beyond 1 mW that means the poly-SiNW FET is a potential red light photo-sensor by detecting IDS change as the light intensity is higher than 1 mW and VGS is set to be 3 V.

In contract to implement the poly-SiNW

FET as a photo-sensor; according to the obtained IDS - light intensity curve, in this study, for a giving VGS, the electric characteristic of an n-type poly-SiNW FET can be manipulated by illuminating red light on the NW with light from 1.0 mW to 2.7 mW.

To verify the poly-SiNW FET can be either used for photo-sensor or manipulated by the light intensity, a continuous light intensity switching experiment is engaged in understanding the light illuminating dynamic response of the poly-SiNW FET. An n-type poly-SiNW FET is operated as VGS is 1.0 V and VDS is 0.5 V, illuminated with a red light, the light intensity is first increased from dark to 0.1 µW, 1 µW, 10 µW, to the maximum 250 µW, and then the light intensity is decreased from 250 µW, 10 µW, 1 µW, 0.1 µW and then turn off.

The electronic response of an n-type

poly-SiNW FET is continuously recorded and the corresponding results are shown in Fig. 5. Obviously, for an n-type device, increasing light intensity will cause the IDS decreased.

Oppositely, decreasing light intensity will cause IDS increased.

From 8


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the time scale, for the first 100 seconds, the light intensity has been increased and all the resulted IDS are similar to Fig. 3 (a).

Figure 5 also shows that the IDS of the

n-type poly-SiNW has no significant difference between dark and illuminated by the red light of 0.1 µW, that means to change the IDS of a poly-SiNW FET the light intensity must higher than a threshold and then the change of IDS will become significant and will be increased as light intensity increased.

Considering a poly-SiNW FET is controlled by VGS and VDS, to understand the possible light manipulations of poly-SiNW FET by causing the electric characteristic change, a four-quadrant analysis based on parameters VGS and VDS are implemented to divide the study into four experimental controlling conditions. The experiments consist of “Turn ON (VGS=-3.5 V)” state of FET with VDS = 0. V (red curve), “Turn ON (VGS= -3.5 V)” state of FET with VDS = 0.5 V (blue curve), “Turn OFF (VGS= 0. V)” state of FET with VDS = 0 V (black curve), as well as “Turn OFF (VGS=0.0 V)” state of FET with VDS = 0.5 V (green curve).

Figure 6 shows the real-time measured

IDS of a p-type poly-SiNW FET as light intensities varied. The light intensities are switched from dark (0 W) to 250 µW and return to dark. Again, the same red light LED has been employed as the light source. The results indicate that the IDS in the blue line, where VGS = -3.5 V and VDS= 0.5 V, is significantly influenced by the illuminating light but for the other three IDS, there is no clear change can be observed by illuminating red light. Comparing the red and blue curves, in both cases, there is gate voltage (VGS = -3.5 V) of p-type poly-SiNW applied across the oxide layer of the transistor, the associated results are shown in blue and red curves with respect to drain-source voltage applied (VDS = 0.5 V) and no drain-source voltage applied respectively, that indicates the change of IDS becomes significant by illuminating light 9



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on the poly-SiNW only when p-type poly-SiNW FET is switched on (ie., VGS is applied) and VDS is set to be 0.5 V. When VGS is 0 (VGS is turn off), the light cannot change the electric characteristic of poly-SiNW FET even the VDS is increased to 0.5 V. Meanwhile, whenever VDS is zero, there is no strong evidence indicates that IDS is available.

In compared with n-type

poly-SiNW-FET shown in Fig. 5, the IDS of p-type poly-SiNW FET under light illumination has an inverse response to an n-type FET; as for p-type, the IDS is increased as the light intensity increased and IDS is decreased as the light intensity decreased which is identical to the result of Fig 3 (b). In similar to n-type poly-SiNW FET, Fig 6 also reveals that the IDS of a p-type poly-SiNW FET can also be manipulated by varying light intensities, and the change of IDS is also determined by the conducting channel of poly-SiNW FET which connects the source and drain via the field effect.

It is noteworthy that the bias

voltages must be applied to act both conducting channels of a poly-SiNW FET; afterwards, the IDS of poly-SiNW FET can be manipulated by illuminating varied light intensity. Because the intrinsic property of poly-SiNW, such as resistance, is stable; therefore if the FET device has no bias voltages to act the channel then no IDS can be generated even though the light intensity is increased to 250 µW.

Wavelength and Environment Effects According to the discussion in the previous section, the electric characteristic of the poly-SiNW FET can be manipulated by illuminating red light with different intensities on the poly-SiNW FET; the manipulation might need to be operated by using short-wavelength light and in vacuum environment. To know the possible application conditions of light manipulation on the poly-SiNW FET electric 10


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characteristic, two experiments have been performed; the poly-SiNW FETs are exposed to ultraviolet (UV) light to explore the light manipulation by wavelength, and the poly-SiNW FETs are illuminated by red light in a vacuum chamber to explore the role of oxygen and moisture on poly-SiNW FET manipulation by light. Manipulating poly-SiNW FET by UV light The infrared (IR) heating is the possible ways to deliver the energy to the device when the light illuminates on the poly-SiNW FET. The IR covers wavelength ranges from 780 nm to 1 mm which can heat an object by conduction and radiation ways. Considering the electric characteristic changes might be introduced by thermal effect, to clarify the possible thermal effect introduced by illuminating light on the poly-SiNW FET an UV light has been employed as light source for the thermal effect testing. In comparison with IR, UV light can deliver less thermal energy to the poly-SiNW. The wavelength spectrum of UV light is from 100 nm to 400 nm, the spectrum of UV light source used in this study is shown in Fig. 7(a). The power of UV light source is 1.0 µW and the center peak of wavelength is 365 nm which is measured by a spectrometer (USB2000+, Ocean Optics).

The range of VGS is

extended to cover from -1.0 V to 8 V with 0.2 V increment. The resulted VGS–IDS curve is plotted in linear scale as shown in Fig. 7(b).

The VGS–IDS curve shows that

when UV light illuminates on the n-type poly-SiNW FET device, the Vth would shift from 4.0 V to 4.5 V; the electric characteristic change is similar as shown in Fig. 3 of which the n-type poly-SiNW FET is illuminated by red light. Meanwhile, this result also shows the strong evidence that the IDS of poly-SiNW FET can be modulated by illuminating the device with the light has no IR radiation energy. In fact, the UV light source has been proved, by previous studies, can affect the electric characteristic of NW FET devices fabricated by the other metals. 11, 22-23.

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In Vacuum Environment It is well known that the conduction of NWs is governed by the electrons which trapping at the surface state

24-25

. In previous studies, researchers highlighted that the

oxygen plays an important role in regulating the current charge in metrical of semiconductor structure

10, 26-27

. The photo generates electron-hole pairs by photos

with a higher energy the bandgap could recombine with the electrons trapped near the surface of NW to liberate the surface-adsorbed oxygen, and results hole concentration increasing. Thus, the electric characteristic of poly-SiNW FET will be changed. Meanwhile, moisture effects have also be proposed, Lin et al. have reported dramatic improvement in device performance by exposing field-effect transistors with polycrystalline silicon nanowire channels to a wet environment 16. In order to verify the assumption about the role of oxygen and moisture in the electric characteristic change of the poly-SiNW FET introduced by light illumination; the poly-SiNW FET light illuminating test is performed in a vacuum chamber (pressure is ~0.1 Torr).

Figure 8 shows the log scale electric characteristics (IDS–VGS) of an

n-type poly-SiNW FET measured at the condition that the VGS varied from -3 to 8 V with 0.2 V increment, VDS is fixed at 0.5 V, and no light illuminates on the FET device. The on/off ratio of an n-type poly-SiNW FET operation in air is evaluated to be around 3294 and the on/off ratio dropping to be about 11.5 in a vacuum. The dynamic IDS response of the n-type poly-SiNW FET illuminated with red light both in air and in a vacuum are illustrated in Fig 9.

The inset figure of Fig. 9

displayed the raw data of IDS measured at 3 V VGS and 0.5 V VDS bias, the IDS is high-low modulated upon the light-on and light-off, respectively. on/off ratio with

Defining the IDS

|+,- !on% − +,- !off%| 9+ !off%, the evaluated IDS on/off ratio is about ,12


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0.2 in air and 0.1 in a vacuum state (0.1 Torr), respectively; as shown in Fig. 9, The IDS on/off ratio in a vacuum environment is near half value as the device in air. Considering the concentration of oxygen is only around 5 × 10-5 mol/L (estimated by ideal gas equation of state) at 0.1 Torr, the results reveal that the light can well manipulate the electric characteristic of poly-SiNW FET by illuminating luight on the surface of device in a low oxygen concentration environment. It is noteworthy that the moisture in a vacuum chamber is also been drawn out, therefore, the IDS response in a vacuum under light illumination indicates that the oxygen and moisture may not the factors which introduce the photocurrent in poly-SiNW FET. However, based on the measured results, the poly-SiNW FET electric characteristic can also be manipulated in a vacuum environment and it can extend for future applications.

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CONCLUSION In this paper, it should be the first time to demonstrated, to our best knowledge, that light can manipulate the electric characteristics of both n- and p-type poly-SiNW FET devices by modulating the illuminating power. Both red and UV lights can adjust, in a non-contact way, the electric characteristics of poly-SiNW FET device, particular for the IDS. It has been clearly observed that the photo-effect appears in the conducting channel of FET device. The conducting channel plays an important role in photo-effect of poly-SiNW FET. We also demonstrate that the vacuum state of photo-effect of poly-SiNW FET. Our finding is of great importance in affording opportunities to further understand surface effects on optoelectronic properties of poly-SiNW FET and also create a new possibility for manipulating the electric characteristics of poly-SiNW FET for biosensing applications, particular for detecting the electrical change introduced by photoelectric effect of poly-SiNW channels after the NW and bio-target interacted.

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ACKNOWLEDGMENT The NW-FET devices were prepared at National Nano Device Laboratories, Taiwan. This work was supported by Ministry of Science and Technology National Science Council (MOST-103-2221-E-492-004- & 104-2627-M-009 -001 -104-2627-M-009 -001 - ).

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10. Shaygan, M.; Davami, K.; Kheirabi, N.; Baek, C. K.; Cuniberti, G.; Meyyappan, M.; Lee, J.-S., Single-Crystalline Cdte Nanowire Field Effect Transistors as Nanowire-Based Photodetector. Physical Chemistry Chemical Physics 2014, 16, 22687-22693. 11. Kao, T.-H.; Chen, J.-Y.; Chiu, C.-H.; Huang, C.-W.; Wu, W.-W., Opto-Electrical Properties of Sb-Doped P-Type ZnO Nanowires. Applied Physics Letters 2014, 104, 111909. 12. Chen, G.; Liang, B.; Liu, Z.; Yu, G.; Xie, X.; Luo, T.; Xie, Z.; Chen, D.; Zhu, M.-Q.; Shen, G., High Performance Rigid and Flexible Visible-Light Photodetectors Based on Aligned X(in, Ga)P Nanowire Arrays. J. Mater. Chem. C 2014, 2, 1270-1277. 13. Wu, H.-C.; Huang, Y.-C.; Ding, I. K.; Chen, C.-C.; Yang, Y.-H.; Tsai, C.-C.; Chen, C.-D.; Chen, Y.-T., Photoinduced Electron Transfer in Dye-Sensitized Sno2 Nanowire Field-Effect Transistors. Advanced Functional Materials 2011, 21, 474-479. 14. Ming-Pei, L.; Cheng-Yun, H.; Wen-Tsan, L.; Yuh-Shyong, Y., Probing the Sensitivity of Nanowire-Based Biosensors Using Liquid-Gating. Nanotechnology 2010, 21, 425505. 15. Lin, C. H.; Hung, C. H.; Hsiao, C. Y.; Lin, H. C.; Ko, F. H.; Yang, Y. S., Poly-Silicon Nanowire Field-Effect Transistor for Ultrasensitive and Label-Free Detection of Pathogenic Avian Influenza DNA. Biosens Bioelectron 2009, 24, 3019-24. 16. Lin, H.-C.; Su, C.-J.; Hsiao, C.-Y.; Yang, Y.-S.; Huang, T.-Y., Water Passivation Effect on Polycrystalline Silicon Nanowires. Applied Physics Letters 2007, 91, 202113. 17. Tian, B.; Cohen-Karni, T.; Qing, Q.; Duan, X.; Xie, P.; Lieber, C. M., Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized Bioprobes. Science 2010, 329, 830-834. 18. Rahong, S., et al., Three-Dimensional Nanowire Structures for Ultra-Fast Separation of DNA, Protein and Rna Molecules. Scientific Reports 2015, 5, 10584. 19. Chang, P.-C.; Chien, C.-J.; Stichtenoth, D.; Ronning, C.; Lu, J. G., Finite Size Effect in ZnO Nanowires. Applied Physics Letters 2007, 90, 113101. 20. Bangsaruntip, S., et al. In High Performance and Highly Uniform Gate-All-around Silicon Nanowire MOSFETs with Wire Size Dependent Scaling, Electron Devices Meeting (IEDM), 2009 IEEE International, 7-9 Dec. 2009; 2009; pp 1-4. 21. Snow, E. S.; Novak, J. P.; Campbell, P. M.; Park, D., Random Networks of Carbon Nanotubes as an Electronic Material. Applied Physics Letters 2003, 82, 16


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2145-2147. 22. Hong, W.-K.; Sohn, J. I.; Cha, S. N.; Kim, J. M.; Welland, M. E., Interplay between Temperature Effects and Surface Recombination Process in Uv Photoresponse of ZnO Nanowires. Applied Surface Science 2015, 324, 512-516. 23. Peretz-Soroka, H.; Pevzner, A.; Davidi, G.; Naddaka, V.; Kwiat, M.; Huppert, D.; Patolsky, F., Manipulating and Monitoring on-Surface Biological Reactions by Light-Triggered Local Ph Alterations. Nano Lett 2015, 15, 4758-4768. 24. Arnold, M. S.; Avouris, P.; Pan, Z. W.; Wang, Z. L., Field-Effect Transistors Based on Single Semiconducting Oxide Nanobelts. The Journal of Physical Chemistry B 2003, 107, 659-663. 25. Law, M.; Kind, H.; Messer, B.; Kim, F.; Yang, P., Photochemical Sensing of No2 with Sno2 Nanoribbon Nanosensors at Room Temperature. Angewandte Chemie International Edition 2002, 41, 2405-2408. 26. Chen, G., et al., Field-Effect Transistors: Single-Crystalline P-Type Zn3as2 Nanowires for Field-Effect Transistors and Visible-Light Photodetectors on Rigid and Flexible Substrates (Adv. Funct. Mater. 21/2013). Advanced Functional Materials 2013, 23, 2666-2666. 27. Soci, C.; Zhang, A.; Xiang, B.; Dayeh, S. A.; Aplin, D. P. R.; Park, J.; Bao, X. Y.; Lo, Y. H.; Wang, D., ZnO Nanowire Uv Photodetectors with High Internal Gain. Nano Lett 2007, 7, 1003-1009.

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Figure 1 (a) poly-SiNW FET with back gate configuration (b) an SEM top-view image of poly-SiNW FET device

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Figure 2, Electric characteristic of a poly-SiNW FET at VDS = 0.5 V (a) IDS–VGS of n-type poly-SiNW FET in log scale; (a’) IDS–VGS of n-type poly-SiNW FET in linear scale. (b) IDS–VGS of p-type poly-SiNW FET in log scales, (b’) IDS–VGS of p-type poly-SiNW FET in linear scale.

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Figure 3, IDS–VGS curve in dark and illuminating by a red light at VDS = 0.5 V (a) Log scale IDS–VGS of n-type poly-SiNW FET (a’) Linear scale IDS–VGS of n-type poly-SiNW FET (b) Log scale IDS–VGS of p-type poly-SiNW FET (b’) Linear scale IDS–VGS of p-type poly-SiNW FET 20


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Figure 4, Effects of light intensities on poly-SiNW FET (a) The IDS – VGS curve with various light illuminations with drain current of n-type poly-SiNW FET at 3 V VGS; (b) the IDS–light intensity relation approximated as exponential function 21



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Figure 5, IDS introduced by light with varied light intensities, 0.1 µW, 1 µW, 10 µW, and 250 µW, at VGS =1.0 V and VDS=0.5 V

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Figure 6, IDS–Time of various light intensities; including “Turn ON” state of FET with VDS = 0 V (red curve) and VDS = 0.5 V (blue curve), “Turn OFF” state of FET with VDS = 0 V (black curve) and VDS = 0.5 V (green curve).

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Figure 7, The electric characteristic behaviors of poly-SiNW FET illuminated by UV light (a) The spectrum of UV light (b)The VGS–IDS curve of a poly-SiNW FET at dark and illuminated with UV light source. The Vth of poly-SiNW FET trends to a positive voltage 24


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Figure 8, Log scale IDS–VGS curve of n-type poly-SiNW FET in air and in a vacuum environment

(0.1 Torr)

Figure 9, Ratio of IDS of ON/OFF light (illuminated by maximum 250 µW red light) 25



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the inset figure is the raw data of IDS–Time curve with light ON/OFF in air and vacuum (0.1 Torr)

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Figure 1 (a)(b) 114x37mm (300 x 300 DPI)



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Figure 2(a) 203x187mm (300 x 300 DPI)


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Figure 2(b) 245x212mm (300 x 300 DPI)



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Figure 3(a) 194x163mm (300 x 300 DPI)


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Figure 3(b) 202x163mm (300 x 300 DPI)



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Figure 4(a) 101x90mm (300 x 300 DPI)


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Figure 4(b) 207x145mm (300 x 300 DPI)



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Figure 5 168x130mm (300 x 300 DPI)


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Figure 6 194x150mm (300 x 300 DPI)



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Figure 7(a) 186x129mm (300 x 300 DPI)


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Figure 7(b) 107x83mm (300 x 300 DPI)



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Figure 8 287x201mm (150 x 150 DPI)


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81x37mm (300 x 300 DPI)


Manipulating Polycrystalline Silicon Nanowire FET Characteristics by

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