Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in

May 9, 2017 - *E-mail for P.X.: [email protected]., *E-mail for X.W.: ... that the inversion layer at the a-MoS2/Si interface made a good contribution to...
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Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in Amorphous MoS2/Si Junctions Chang Hu, Xianjie Wang, Peng Miao, Lingli Zhang, Bingqian Song, Weilong Liu, Zhe Lv, Yu Zhang, Yu Sui, Jinke Tang, Yanqiang Yang, Bo Song, and Ping Xu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 09 May 2017 Downloaded from http://pubs.acs.org on May 10, 2017

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Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in Amorphous MoS2/Si Junctions Chang Hu†, Xianjie Wang*,†, Peng Miao‡, Lingli Zhang†, Bingqian Song†, Weilong Liu†,Zhe Lv†, Yu Zhang†, Yu Sui†, Jinke Tang‖, Yanqiang Yang#, Bo Song*,†,§and Ping Xu*,‡ †

Department of Physics, Harbin Institute of Technology, Harbin 150001, China School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China § Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150001, China ‡



Department of Physics & Astronomy, University of Wyoming, Laramie, WY 82071, USA National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China

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ABSTRACT: The lateral photovoltaic (LPV) effect has attracted much attention for a long time due to its application in position–sensitive detectors (PSD). Here, we report the ultrafast response of the LPV in amorphous MoS2/Si (a-MoS2/Si) junctions prepared by pulsed laser deposition (PLD) technique. Different orientations of the built-in field and the breakover voltages are observed for a-MoS2 films deposited on p- and n-type Si wafers, resulting in the induction of positive and negative voltages in the a-MoS2/n-Si and a-MoS2/p-Si junctions upon laser illumination, respectively. The dependence of the LPV on the position of the illumination shows very high sensitivity (183 mV mm-1) and good linearity. The optical relaxation time of LPV with a positive voltage was about 5.8 μs in a-MoS2/n-Si junction while the optical relaxation time of LPV with a negative voltage was about 2.1 μs in a-MoS2/p-Si junction. Our results clearly suggested that the inversion layer at the a-MoS2/Si interface made a good contribution to the ultrafast response of the LPV in a-MoS2/Si junctions. The large positional sensitivity and ultrafast relaxation of LPV may promise the a-MoS2/Si junction’s applications in fast position– sensitive detectors. Keywords: Amorphous MoS2/Si junctions; lateral photovoltaic (LPV); pulsed laser deposition (PLD); ultrafast relaxation; position–sensitive detectors; inversion layer

1. INTRODUCTION Intensive research on the lateral photovoltaic (LPV) effect has been pursued for a long time due to its practical application as position–sensitive detectors (PSDs) with high sensitivity for very small displacements. The LPV had been observed in various junctions.1-8 A large LPV with good linearity and short relaxation time is necessary for PSDs with high performance. The simple metalsemiconductor (MS) junctions show a large LPV, but the induced LPV is sensitive to the thickness of the metal layer.9-12 Cascales et al. investigated the time dependent transient LPV in the Co/Si structure and explain the sign inversion of the LPV after the laser has been powered off using a modification of the drift-diffusion model.13 The fast response of the LPV is observed in Si p-n junctions, but the position sensitivity is much smaller than that observed in MS structures, which limits the use of Si junctions in PSD.14 Very recently, we observed large position sensitivity and a short relaxation time for the LPV in Fe3O4/Si and SnSe/Si junctions, and suggested that the inversion layer at the interface of film/Si junction had a major contribution to the fast relaxation time.15-16 The large LPV and fast response speed made the Si-based

junctions promising candidates for many fast optoelectronic applications. MoS2 has garnered great interest in recent years due to its unique electronic and optical properties,17-21 but the large area growth of MoS2 is a key requirement to realize its application in PSD. Recently, there have been reports of large area growth of MoS2 films using pulsed laser deposition (PLD) and the observation of photodiode-like behavior in (n- and p- type) Si/MoS2 heterostructures.22-26 Compared with the MoS2 single crystal film, the amorphous MoS2 (a-MoS2) film can be prepared easily over a large area on a Si wafer. The carrier mobility of n-type aMoS2 is much lower than that of Si. The bandgap of MoS2 single crystal is about 1.3 eV, and p-n or n-n junctions will be formed once the MoS2 thin film is deposited on the pSi or n-Si wafers. As a result, different orientations of the built-in field and the breakover voltages will be achieved in the a-MoS2/n-Si and a-MoS2/p-Si junctions, and thus the laser excited holes and electrons will flow to the aMoS2 sides in the a-MoS2/n-Si and a-MoS2/p-Si junctions, respectively. Therefore, the a-MoS2/Si junctions are good candidates to explore the true origin of the ultrafast response of LPV properties in Si-based devices.

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In this paper, we report a large LPV with an ultrafast response time in a-MoS2/Si structures prepared using PLD on p- and n-Si wafers. The LPV exhibits a linear dependence on the distance between the electrodes attached to the structures and the site of the laser illumination with position sensitivity as high as 183 mV mm-1. The optical relaxation times of the LPV were approximately 5.8 μs and 2.1 μs in the a-MoS2/n-Si and a-MoS2/p-Si junctions, respectively, which clearly suggests that most of the excited carriers diffuse laterally in the inversion layer that is formed at the a-MoS2/Si interface instead of in the a-MoS2 film.

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POS7102T) was used to measure the variation of the LPV with time at room temperature.

3. RESULTS AND DISCUSSION XPS of the surface of the MoS2 film was performed to identify the corresponding chemical valence states, as shown in Figure 1 (a) and (b). The signals of Mo4+ and S2were clearly observed with a content ratio of Mo/S of about 1:2, which suggested the stoichiometric growth of the MoS2 film, here the C peak was used to align the energy axis. Raman spectroscopy has been extensively used to characterize the quality of MoS2 film. Only two features were observed in the Raman spectroscopy of MoS2, as shown in Figure 1 (c). The E12g mode results from the inplane vibrations of the two sulfur atoms in opposite directions with respect to the Mo atom, and the A1g mode is a result of the vibration of the S atomic sheets in opposite directions with respect to Mo layer. But the broadening of the peaks corresponding to the E12g and A1g modes suggests that the MoS2 films contain an amorphous phase. In order to confirm the crystallinity of the MoS2 film, the MoS2/Si structure was investigated with high-resolution transmission electron microscopy (HRTEM) with the cross-sectional sample. A dense and disordered morphology without long-range order is apparent at the interface between the MoS2 film and Si wafer, indicating that the MoS2 film is amorphous with no observable layered structure, as shown in Figure 1 (d).

Figure 1. (a) XPS data for Mo 3d in a-MoS2/Si; (b) XPS data for S 2p in a-MoS2/Si; (c) Raman spectroscopy data for an a-MoS2 film; (d) high-resolution TEM pattern of a-MoS2/Si structure.

2. EXPERIMENTAL SECTION Fabrication of a-MoS2/Si junctions. The a-MoS2 (15 nm) thin films were prepared using PLD on both n- and p-type Si(100) wafers with Hall bar mask. The native SiO2 layer on the wafer surface was not removed. MoS2 (99.9%, Alfa Aesar) was the target and the resistivity of Si wafer is about 10-80 Ω cm. The films were prepared at 10-7 Torr and 500 ℃. The pulsed excimer laser used KrF gas (λ = 248 nm), which produced laser pulses (1 Hz) of intensity of 1-2 J/cm2. Characterization. Ultraviolet photoemission spectroscopy (UPS) was measured using Specs UVLS (He I excitation, 21.22 eV). X-ray photoelectron spectroscopy (XPS) was measured using ESCALAB 250Xi. Raman scattering analysis for the samples was performed with the Dispersive Raman Microscope (Senterra R200-L, Bruker Optics). I-V curves were obtained using a Keithley 2601. The LPV was done using different laser and a Keithley 2000 multimeter. The high-resolution transmission electron microscopy (HRTEM) measurement is carried out using a JEOL Model 2010 TEM. The Hall data was measured using HALL8800. The laser system (λ = 532 nm) with 100 ns pulse duration and a 100 MHz oscilloscope (Owon

Figure 2. (a) The UPS spectrum of a-MoS2; (b) the longitudinal I-V curve measured in the a-MoS2/n-Si junction and (c) the aMoS2/p-Si junction. The insets show the drawing of the junction and circuit as well as the energy-band of the a-MoS2/Si junctions.

Figure 2 (a) shows the UPS spectrum of a-MoS2 to conclude its band position. The inelastic electron cutoff (Ecutoff) locates at 15.85 eV. The UPS of clean Au film on a Si wafer was used for the Fermi level (EF) and the binding energy calibrations (Figure S1).27 Obviously, the Fermi energy of Au was -0.21 eV, thus, the work function (Ф) of a-MoS2 should be obtained as Ф=21.22-(15.85+0.21)=5.16 (eV). According to the value of the highest occupied states (HOS), as shown in the inset of Figure 2 (a), ionization potential (Ip) could be obtained as Ip=21.22-(15.85-

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0.79)=6.16 (eV). The distance between the valence band maximum and the Fermi energy was calculated as 1.0 eV. The bandgap of a-MoS2 is approximately 1.37 eV that was concluded from the transmittance spectra of a-MoS2 on SiO2 substrate (Figure S2). Figure 2 (b) and (c) show the longitudinal I-V curve of the a-MoS2/Si junction measured at 300 K. The longitudinal I-V curves exhibit a diode-like rectifying character in the a-MoS2/n-Si and a-MoS2/p-Si junctions. The current increases drastically with increasing forward bias voltage in the a-MoS2/n-Si junction and with increasing reverse bias in the a-MoS2/p-Si junction. Thus the breakover voltages are positive and negative for the a-MoS2/n-Si and aMoS2/p-Si junctions, respectively. The band gap of a-MoS2 and Si are approximately 1.37 eV and 1.2 eV, respectively. A large built-in field forms at the a-MoS2/Si junction once the a-MoS2 thin film has been deposited on the Si wafer. The Fermi surfaces of n-Si and p-Si are different, which results in the different orientations of the built-in field and the breakover voltages in the a-MoS2/n-Si and aMoS2/p-Si junctions, as shown in the inset of Figure 2 (b) and (c). The electron-hole pairs will be excited by the laser and then separated by the built-in field. Therefore, the excited holes and electrons will flow to the a-MoS2 sides in the a-MoS2/n-Si and a-MoS2/p-Si junctions, respectively, as shown in the inset of Figure 2 (b) and (c).

tive, suggesting the lateral diffusion of excited electrons within the a-MoS2 film side. In the a-MoS2/n-Si junction, the voltage between electrodes A and B is negative, suggesting the lateral diffusion of holes within the a-MoS2 film side. These results are consistent with the different orientations of the built-in field and the breakover voltages in the a-MoS2/n-Si and a-MoS2/p-Si junctions, as shown in the inset of Figure 2 (b) and (c). Figure 3 shows the dependence of the LPV on the laser illumination spot position for the a-MoS2/Si junctions. The LPV shows a good linearly dependence on the distance between the electrodes attached to the structures and the largest positional sensitivity of 183 and 145 mV mm-1 was observed in the a-MoS2/p-Si and a-MoS2/n-Si junctions, respectively. The LPV of a-MoS2/Si with a thickness of 60 nm is smaller than that of the junction with a thickness of 15 nm (Figure S4). The LPV data of Figure 3 fit well with the traditional LPV = K [exp(− L − x / d ) − exp(− L + x / d )]

0 theory: , where K0 is a proportionality coefficient, 2L is the distance between the electrodes, d is the electron/hole diffusion length and x is the distance between the laser spot position and the middle of electrodes.28-29 The fit to the data clearly suggests that the LPV in both the a-MoS2/n-Si and a-MoS2/pSi junctions arises from the lateral diffuse flow and recombination of the excited carriers away from the illumination site. The linearity of the LPV strongly depends on the distance of two electrodes. When the distance is larger than 2 mm, the linear between the electrodes A and B would be broken (Figure S5). The electron diffusion length in the film play a key role on the linearity of LPV.11 The perfect linearity can only be achieved in the case of short electrodes’ distance, and the linearity deteriorates when two electrodes’ distance is longer than the electron diffusion length. Furthermore, the most of light absorption took place in the Si wafer (Figure S2). The excited electrons and holes’ migration rates in Si are different, and the recombination of the excited-holes in n-Si is much larger than that of the excited-electrons in p-Si due to the small migration rate of holes in n-Si. So the position sensitivity of a-MoS2/p-Si is larger than that of aMoS2/n-Si.

Figure 3. The dependence of the LPV on the illumination position relative to the location of the electrodes in the a-MoS2/n-Si (blue) and a-MoS2/p-Si (black) junctions.

The different band structure of a-MoS2/n-Si and aMoS2/p-Si junctions will result in different LPV properties. A Hall bar structure was used for the LPV measurement (Figure S3). Obviously, a large LPV was observed in a-MoS2/Si junctions once the a-MoS2 surface was partially illuminated by a laser. Electrodes A and B were connected to the positive and negative probes of a Keithley 2000 multimeter, respectively. When the laser illuminates the a-MoS2 surface near electrode B in the a-MoS2/p-Si junction, the light-induced voltage between A and B is posi-

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Figure 4. The dependence of the LPV on the laser power and laser wavelength in the a-MoS2/n-Si (a-b) and a-MoS2/p-Si (c-d) junctions.

Figure 4 shows the LPV as a function of the laser power and wavelength used to illuminate the a-MoS2/n-Si and aMoS2/p-Si junctions. Obviously, the LPV increases drastically with increasing the laser power initially, but then slowly saturates when the power further increases. This saturation may origin from the rapidly increasing recombination rate of the excited carriers with increasing laser intensity in the illuminated region.1 There is an optimum wavelength for obtaining the highest LPV. The laser was absorbed in a-MoS2 and Si with different probabilities because the absorption probability is strongly affected by both the thickness and the bandgap of the semiconductors. The a-MoS2 film has a low absorption probability because of its smaller thickness (15 nm) and larger bandgap compared with the Si wafer in a-MoS2/Si junctions (Figure S2). Thus, most of absorption took place in the Si wafers. The electron-hole pairs are excited in the aMoS2 and Si wafer by the laser. The electron-hole pairs can be only excited at the illuminated area and separated by the built-in field in the junctions. The excited electrons (holes) flow to the a-MoS2 film side in the a-MoS2/p-Si (aMoS2/n-Si) junction, and then laterally diffuse away to the two electrodes because the illuminated area is very small. The concentration of the excited carriers at the two electrodes is different for different distances between the electrodes and the illuminated spot; thus, a lateral field is built up and the LPV is observed.

Figure 5. The variation of the LPV with time in the a-MoS2/n-Si (a) and a-MoS2/p-Si (b) junctions; the inset shows the schematic circuit of the measurement.

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The excited electrons and holes will flow to the a-MoS2 film side in the a-MoS2/p-Si and a-MoS2/n-Si junctions, respectively, which will result in a huge difference in response and relaxation times of the LPV in the a-MoS2/n-Si and a-MoS2/p-Si junctions. Figure 5 shows variation of the LPV with time in the a-MoS2/Si junctions. The diagram of the experimental setup for the time response of LPV is shown in the inset of Figure 5 and Figure S6. The rise time is approximately 1.0 μs, and the full width at half maximum (FWHM) of the curve is about 22.5 μs (8.9 μs) when the LPV is directly measured using an oscilloscope in the a-MoS2/n-Si (a-MoS2/p-Si) junctions. The FWHM can usually be considered as the relaxation time of the LPV.2, 30-32 It is well-know that fast response time of laserinduced voltage can also be induced by the thermoelectric effect.33-35 But we think that the LPV in a-MoS2/Si junctions originates from the laser-induced voltage because most of light absorption took place in the Si wafers instead of the a-MoS2 film (Figure S2). Furthermore, the LPV should increase with increasing laser power if the LPV originates from the thermoelectric effect.34 However, we find that the LPV is proportional to the laser power initially, but then slowly saturates as the power increases (Figure 4), which is attributed to the rapidly increasing recombination rate of the carriers with increasing laser intensity in the illuminated region.1 Therefore, the sharp initial rise in the voltage curves of Figure 5 indicates that the LPV didn’t come from the thermoelectric effect. The resistors with different resistances were connected to simulate the ideal circuit, as shown in the inset of Figure 5. With this setup, the rise times dramatically decrease to approximately 200 ns and the relaxation time is reduced to about 5.8 μs in the a-MoS2/n-Si junction. In the aMoS2/p-Si junction, the rise time is approximately 150 ns and the relaxation time is about 2.1 μs, nearly three times faster than that in the a-MoS2/n-Si junction. The optical relaxation time increases with increasing the thickness of a-MoS2 film (Figure S7). The carrier mobility of the inversion layer in a-MoS2/p-Si is similar with that of SnSe/p-Si. Therefore, the response and relaxation times of a-MoS2/pSi structure are nearly the same with that of SnSe/Si structure because the excited electrons in both junctions lateral diffuse flow away in the inversion layer from the laser spot.15 If the resistance is smaller than 0.3 kΩ, the relaxation time should be faster, however, the LPV would be so small that the oscilloscope couldn’t read it. So we suggest that the rise and relaxation times under 0.3 kΩ are the response times of a-MoS2/Si junctions. The linear I-V curves of p-Si wafer and a-MoS2 film on SiO2 substrate are observed (Figure S8), suggesting the Ohmic contact between the electrode and the Si (or aMoS2 film). However, the I-V curves measured on the surface of the a-MoS2 film in a-MoS2/Si junctions at room temperature show nonlinear increase in current with increasing voltage, indicating the formation of an inversion layer at the a-MoS2/Si interface because the inversion lay-

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er can provide a low resistive path for carrier transport,15as shown in Figure 6. So the measured resistance on the a-MoS2 surface is the parallel resistance of the a-MoS2 film and the inversion layer, and the lateral diffuse flow of the excited carriers should travel in a-MoS2 and the inversion layer, The thickness of inversion layer is less than 5 nm and the room temperature mobility of hole and electron in inversion layer at SiO2/Si interface were about 400 and 700 cm2V-1s-1, respectively.39-40 The electron mobility of a-MoS2 film deposited on SiO2 glass is about 0.2 cm2V1 -1 s . However, the carriers’ mobility measured on the surface of the a-MoS2 films deposited on n- and p- Si wafers is 154 and 415 cm2V-1s-1, respectively. This result suggested that most of the excited-electrons diffuse laterally in the inversion layer at the a-MoS2/Si interface rather than in the a-MoS2 layer because the carriers’ mobility of inversion layer is much higher than that of the a-MoS2 film. The excited-electrons are separated towards the a-MoS2 side by the built-in field in the a-MoS2/p-Si junction. The lower electron mobility of a-MoS2 film will make lateral diffusion of electrons in the a-MoS2 film difficultly and result in a very slow relaxation of the LPV. However, a fast LPV relaxation can be observed if most of the excited electrons diffuse laterally in the inversion layer instead of in the a-MoS2 film because of the high electron mobility of the inversion layer at the interface. Furthermore, the relaxation time of the LPV in a-MoS2/n-Si junction is about three times as large as that in a-MoS2/p-Si junction, which is consistent with different motilities of electrons and holes in inversion layer. These results clearly suggest that most of the excited-carriers diffuse laterally in the inversion layer at the a-MoS2/Si interface instead of the aMoS2 film. Therefore, the inversion layer at the interface of a-MoS2/Si is responsible for the fast response and relaxation times of the LPV. 16, 36-38

that of the excited-electrons in p-Si due to the small migration rate of holes, which results in the larger position sensitivity of a-MoS2/p-Si. The LPV relaxation time in aMoS2/n-Si junction (5.8 µs) is nearly triple that that in aMoS2/p-Si junction (2.1 µs), consistent with the differing mobility of electrons and holes in inversion layer. These results clearly suggested that most of the excited-carriers diffuse laterally in the inversion layer at the MoS2/Si interface instead of in the a-MoS2 film, leading to the observation of an ultrafast response of the LPV.

ASSOCIATED CONTENT Supporting Information. UPS and transmittance spectra, optical image of the device, and additional validation. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (P.X.) [email protected] (X.W.); [email protected] (B. S.); ACKNOWLEDGMENT This work is supported by National Natural Science Foundation of China (Nos. 51472064, 21471039, 51372056, 21671047), International Science & Technology Cooperation Program of China (2012DFR50020) and the Program for New Century Excellent Talents in University (NCET-13-0174), Fundamental Research Funds for the Central Universities and Program for Innovation Research of Science in Harbin Institute of Technology (PIRS of HIT A201502 and 201616).

REFERENCES

Figure 6. The transverse I-V curve of the a-MoS2/n-Si (a) and aMoS2/p-Si (b) junctions measured at room temperature; the inset shows the schematic setup for the measurement.

4. CONCLUSIONS In conclusion, we fabricated the a-MoS2/n-Si and aMoS2/p-Si junctions using PLD and investigated the LPV in these junctions. The dependence of the LPV on the position of the laser illumination spot shows very high sensitivity (183 mV mm-1) and good linearity. The recombination of the excited-holes in n-Si is much larger than

(1) Willens, R. H. Photoelectronic and Electronic Properties of Ti/Si Amorphous Superlattices. Appl. Phys. Lett. 1986, 49, 663. (2) Jin, K.-J.; Zhao, K.; Lu, H.-B.; Liao, L.; Yang, G.-Z. Dember effect Induced Photovoltage in Perovskite p-n Heterojunctions. Appl. Phys. Lett. 2007, 91, 081906. (3) Xiao, S. Q.; Wang, H.; Zhao, Z. C.; Gu, Y. Z.; Xia, Y. X.; Wang, Z. H. The Co-film-thickness Dependent Lateral Photoeffect in Co-SiO2-Si Metal-oxide-semiconductor Structures. Opt. Express 2008, 16, 3798. (4) Zhao, K.; Jin, K. J.; Lu, H. B.; Huang, Y. H.; Zhou, Q. L.; He, M.; Chen, Z. H.; Zhou, Y. L.; Yang, G. Z. Transient Lateral Photovoltaic Effect in p-n Heterojunctions of La0.7Sr0.3MnO3 and Si. Appl. Phys. Lett. 2006, 88, 141914. (5) Henry, J.; Livingstone, J. Thin-Film Amorphous Silicon Position-Sensitive Detectors. Adv. Mater. 2001, 13, 10231026. (6) Wallmark, J. T. A New Semiconductor Photocell Using Lateral Photoeffect. Proc. IRE 1957, 45, 474. (7) Levine, B. F.; Willens, R. H.; Bethea, C. G.; Brasen, D. Lateral Photoeffect in Thin Amorphous Superlattice

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Films of Si and Ti Grown on a Si Substrate. Appl. Phys. Lett. 1986, 49, 1537. (8) Wang, S.; Wang, W.; Zou, L.; Zhang, X.; Cai, J.; Sun, Z.; Shen, B.; Sun, J. Magnetic Tuning of the Photovoltaic Effect in Silicon-based Schottky Junctions. Adv. Mater. 2014, 26, 8059-8064. (9) Liu, S.; Wang, H.; Yao, Y. J.; Chen, L.; Wang, Z. L. Lateral Photovoltaic Effect Observed in Aano Au Film Covered Two-dimensional Colloidal Crystals. Appl. Phys. Lett. 2014, 104, 111110. (10) Du, L.; Wang, H. Infrared Laser Induced Lateral Photovoltaic Effect Observed in Cu2O Nanoscale Film. Opt. Express 2010, 18, 9113-9118. (11) Yu, C. Q.; Wang, H.; Xiao, S. Q.; Xia, Y. X. Direct Observation of Lateral Photovoltaic Effect in Nanometal-films. Opt. Express 2009, 17, 21712-21722. (12) Yu, C. Q.; Wang, H.; Xia, Y. X. Giant Lateral Photovoltaic Effect Observed in TiO2 Dusted Metal-semiconductor Structure of Ti/TiO2/Si. Appl. Phys. Lett. 2009, 95, 141112. (13) Cascales, J. P.; Martínez, I.; Díaz, D.; Rodrigo, J. A.; Aliev, F. G. Transient Lateral Photovoltaic Effect in Patterned Metal-oxide-semiconductor Films. Appl. Phys. Lett. 2014, 104, 231118. (14) Henry, J.; Livingstone, J. Aging Effects of Schottky Barrier Position Sensitive Detectors. IEEE Sens. J. 2006, 6, 1557. (15) Wang, X. J.; Zhao, X. F.; Hu, C.; Zhang, Y.; Song, B. Q.; Zhang, L. L.; Liu, W. L.; Lv, Z.; Zhang, Y.; Tang, J. K.; Sui, Y.; Song, B. Large Lateral Photovoltaic Effect with Ultrafast Relaxation Time in SnSe/Si Junction. Appl. Phys. Lett. 2016, 109, 023502. (16) Wang, X. J.; Song, B. Q.; Huo, M. X.; Song, Y. F.; Lv, Z.; Zhang, Y.; Wang, Y.; Song, Y. L.; Wen, J. H.; Sui, Y.; Tang, J. K. Fast and Sensitive Lateral Photovoltaic Effects in Fe3O4/Si Schottky Junction. RSC Adv. 2015, 5, 6504865051. (17) Gan, L.-Y.; Zhang, Q.; Cheng, Y.; Schwingenschlögl, U. Photovoltaic Heterojunctions of Fullerenes with MoS2 and WS2 Monolayers. J. Phys. Chem. Lett. 2014, 5, 14451449. (18) Wu, C.-C.; Jariwala, D.; Sangwan, V. K.; Marks, T. J.; Hersam, M. C.; Lauhon, L. J. Elucidating the Photoresponse of Ultrathin MoS2 Field-Effect Transistors by Scanning Photocurrent Microscopy. J. Phys. Chem. Lett. 2013, 4, 2508-2513. (19) Ataca, C.; Şahin, H.; Aktürk, E.; Ciraci, S. Mechanical and Electronic Properties of MoS2 Nanoribbons and Their Defects. J. Phys. Chem. C 2011, 115, 3934-3941. (20) Splendiani, A.; Sun, L.; Zhang, Y. B.; Li, T. S.; Kim, J. W.; Chim, C.-Y.; Galli, G.; Wang, F. Emerging Photoluminescence in Monolayer MoS2. Nano Lett. 2010, 10, 1271-1275. (21) Radisavljevic, B.; Radenovic, A.; Brivio, J.; Giacometti, V.; Kis, A. Single-layer MoS2 Transistors. Nat. Nanotechnol. 2011, 6, 147-150. (22) Ho, Y.-T.; Ma, C.-H.; Luong, T.-T.; Wei, L.-L.; Yen, T.-C.; Hsu, W.-T.; Chang, W.-H.; Chu, Y.-C.; Tu, Y.-Y.; Pande, K. P.; Chang, E. Y. Layered MoS2 Grown on c-sapphire by Pulsed Laser Deposition. Phys. Status Solidi-R 2015, 9, 187-191.

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(23) Serna, M. I.; Yoo, S. H.; Moreno, S. E.; Xi, Y.; Oviedo, J. P.; Choi, H.; Alshareef, H. N.; Kim, M. J.; MinaryJolandan, M.; Quevedo-Lopez, M. A. Large-Area Deposition of MoS2 by Pulsed Laser Deposition with In Situ Thickness Control. ACS Nano 2016, 10, 6054-6061. (24) Choudhary, N.; Park, J.; Hwang, J. Y.; Choi, W. Growth of Large-Scale and Thickness-Modulated MoS2 Nanosheets. ACS Appl. Mater. Inter. 2014, 6, 21215-21222. (25) Late, D. J.; Shaikh, P. A.; Khare, R.; Kashid, R. V.; Chaudhary, M.; More, M. A.; Ogale, S. B. Pulsed LaserDeposited MoS2 Thin Films on W and Si: Field Emission and Photoresponse Studies. ACS Appl. Mater. Inter. 2014, 6, 15881-15888. (26) Loh, T.-A. J.; Chua, D.-H. C. Growth Mechanism of Pulsed Laser Fabricated Few-Layer MoS2 on Metal Substrates. ACS Appl. Mater. Inter. 2014, 6, 15966-15971. (27) Liu, X.; Chen, J.; Luo, M.; Leng, M.; Xia, Z.; Zhou, Y.; Qin, S.; Xue, D. J.; Lv, L.; Huang, H.; Niu, D.; Tang, J. Thermal Evaporation and Characterization of Sb2Se3 Thin Film for Substrate Sb2Se3/CdS Solar Cells. ACS Appl. Mater. Inter. 2014, 6, 10687-10695. (28) Yu, C.; Wang, H. Large Lateral Photovoltaic Effect in Metal-(oxide-) semiconductor Structures. Sensors 2010, 10, 10155-10180. (29) Boeringer, D. W.; Tsu, R. Lateral Photovoltaic Effect in Porous Silicon. Appl. Phys. Lett. 1994, 65, 2332. (30) Xiong, J.; Jin, K.J; He, M..; Lu, H.B.; Liu, G.Z.; Yang, G.Z.. Ultrafast and High-sensitivity Photovoltaic Effects in TiN/Si Schottky Junction. J. Phys. D: Appl. Phys. 2008, 41, 195103. (31) Lu, H.-B.; Jin, K.-J.; Huang, Y.-H.; He, M.; Zhao, K.; Cheng, B.-L.; Chen, Z.-H.; Zhou, Y.-L.; Dai, S.-Y.; Yang, G.-Z. Picosecond Photoelectric Characteristic in La0.7Sr0.3MnO3∕Si p-n Junctions. Appl. Phys. Lett. 2005, 86, 241915. (32) Zhao, K.; Jin, K.-j.; Lu, H.; Huang, Y.; Zhou, Q.; He, M.; Chen, Z.; Zhou, Y.; Yang, G. Transient Lateral Photovoltaic Effect in p-n Heterojunctions of La0.7Sr0.3MnO3 and Si. Appl. Phys. Lett. 2006, 88, 141914. (33) Zhang, P. X.; Lee, W. K.; Zhang, G. Y. Time Dependence of Laser-induced Thermoelectric Voltages in La1−xCa xMnO 3 and YBa2Cu 3O7−δ Thin Films. Appl. Phys. Lett. 2002, 81, 4026. (34) Wang, S.; Cheng, J.; Zhao, X.; Zhao, S.; He, L.; Chen, M.; Yu, W.; Wang, J.; Fu, G. Laser-induced Voltage Characteristics of Bi2Sr2Co2Oy Thin films on LaAlO3 Substrates. Appl. Surf. Sci. 2010, 257, 157-159. (35) Sun, J. R.; Xiong, C. M.; Shen, B. G.; Wang, P. Y.; Weng, Y. X. Manganite-based Heterojunction and Its Photovoltaic Effects. Appl. Phys. Lett. 2004, 84, 2611. (36) Tang, J. K.; Dai, J. B.; Wang, K. Y.; Zhou, W. L.; Ruzycki, N.; Diebold, U. Current-controlled Channel Switching and Magnetoresistance in an Fe3C Island Film Supported on a Si substrate. J. Appl. Phys. 2002, 91, 8411-8413. (37) Wang, X. J.; Sui, Y.; Tang, J. K.; Wang, C.; Zhang, X. Q.; Lu, Z.; Liu, Z. G.; Su, W. H.; Wei, X. K.; Yu, R. C. Amplification of Magnetoresistance of Magnetite in An Fe3O4–SiO2–Si Structure. Appl. Phys. Lett. 2008, 92, 012122. (38) Wang, H.; Xiao, S. Q.; Yu, C. Q.; Xia, Y. X.; Jin, Q. Y.; Wang, Z. H. Correlation of Magnetoresistance and

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Lateral Photovoltage in Co3Mn2O/SiO2/Si Metal–oxide– semiconductor Structure. New J. Phys. 2008, 10, 093006. (39) Takagi, S.; Toriumi, A.; Iwase, M.; Tango, H. On the Universality of Inversion Layer Mobility in Si Mosfets: Part 1-Effects of Substrate Impurity Concentration. IEEE T. Electron Dev. 1994, 41, 2357-2362.

(40) Fischetti, M. V.; Neumayer, D. A.; Cartier, E. A. Effective Electron Mobility in Si Inversion Layers in Metal–oxide– semiconductor Systems with a High-κ Insulator: The role of Remote Phonon Scattering. J. Appl. Phys. 2001, 90, 4587-4608.

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