Electrical and Photoelectrical Properties of Reduced Graphene Oxide—Porous Silicon Nanostructures
© The Author(s). 2017
Received: 23 December 2016
Accepted: 4 April 2017
Published: 13 April 2017
In this work, the hybrid structures were created by electrochemical etching of silicon wafer and deposition of reduced graphene oxide (RGO) on the porous silicon (PS) layer. With the help of SEM and AFM, the formation of hybrid PS–RGO structure was confirmed. By means of current–voltage characteristic analysis and impedance spectroscopy, we studied electrical characteristics of PS–RGO structures. The formation of photosensitive electrical barriers in hybrid structures was revealed. Temporal parameters and spectral characteristics of photoresponse in the 400–1100-nm wavelength range were investigated. The widening of spectral range of photosensitivity of the hybrid structures in short-wavelength range in comparison with single-crystal silicon was revealed. The obtained results broaden the prospects of application of the PS–RGO structures in photoelectronics.
KeywordsPorous silicon Reduced graphene oxide Hybrid structure Photosensitivity Current–voltage characteristics Impedance spectroscopy
PACS73.63.-b 78.67.-n 81.05.Rm
The rapid development of electronics is associated with the search for new functional nanomaterials. Unusual properties of hybrid material combining graphene and porous semiconductors, in particular porous silicon (PS), have caused the emergence of potential applications, ranging from photoreceivers and biochemical sensors to field effect transistors and electrodes for power sources [1–5].
Graphene and graphene-based materials have been attracting great research interest with regard to their outstanding electronic and optical properties. Graphene is a two-dimensional sheet composed of sp2-bonded single-layer carbon atoms with the honeycomb lattice structure [6–8]. This conical shape of the electron spectrum of two-dimensional hexagonal lattice causes the most unique properties of graphene as a gapless semiconductor [9, 10]. In particular, the electrons in graphene behave like massless Dirac particles, and their mobility is almost two orders of magnitude higher than the mobility of free electrons in silicon [10–12]. In addition, the positions of the Fermi level and hence the concentration of free charge carriers in graphene are conveniently managed by external electrical voltage [10, 13]. With this approach, it is easy to inject carriers with positive or negative charge in graphene. Besides superior electric conductivity, graphene is characterized by high thermal conductivity and optical transparency [7, 12, 14]. One of the promising methods for producing graphene is via chemical exfoliation and oxidations of graphite to produce graphene oxide (GO) followed by subsequent reduction [15–17]. Reduced graphene oxide (RGO) is usually obtained through chemical reactions with the use of hydrazine, hydrogen, sodium tetrahydroborate, or other reducing agents [17, 18].
On the other hand, PS is recognized as an attractive material for photoelectrical devices because of high surface to volume ratio and high light absorption [19–22]. PS is prepared by etching a single crystal with the formation of small cavities and silicon nanostructures (nanowires and nanowalls) [23, 24]. Changing the band energy structure of silicon when moving from bulk to nanocrystals due to quantum confinement allows to significantly widen the absorption spectra of photonic devices based on the PS. Using multilayered photosensitive structures based on silicon nanomaterials allows to achieve a notable improvement in sunlight to energy conversion efficiency and to design the new generation photodetectors [25–27]. Also, PS is a perfect candidate for deposition and infiltration of graphene nanosheets and GO into sponge-like geometrical structure of the substrate [28, 29]. The photoreceivers with PS surface coated by RGO have high sensitivity and quantum efficiency over a wide spectral range—from near UV to IR . Some previous researches have shown the effectiveness of using graphene as a transparent electrode in displays and photonic devices [14, 30, 31]. In this regard, the formation of PS–RGO structures is promising for their applications in photodetectors and energy conversion devices.
In this work, we created the hybrid PS–RGO structures in order to investigate their electrical and photoelectrical properties. Electrical parameters of obtained structures have been studied in alternating and direct current modes. It has been demonstrated that hybrid PS–RGO nanosystems have the potential for application in electronic and photoelectric devices.
PS was manufactured by means of electrochemical etching performed in ethanol solution of hydrofluoric acid (the volume ratio of the components HF:C2H5OH = 1:1) on single-crystalline silicon substrates with the typical thicknesses of 400 μm and the crystallographic orientation (100). The silicon substrates had electronic type of conductivity (n-Si), with the specific resistance of 4.5 Ω cm. In order to obtain homogeneous layers of the PS, gold films were preliminarily deposited on a back surface of the substrates with the aid of a thermo-vacuum technique. These films served also as contacts for further measurements. The anodic current density was equal to 20 mA/cm2, and the etching time was 5–10 min. To ensure availability of holes in the surface layer of n-Si, which were necessary for occurrence of anodic reactions and formation of the PS, the working surface of a silicon plate was irradiated by 500-W filament lamp during the whole process of electrochemical etching . As a result, narrow pores were formed that tend to direct towards the inside of the silicon crystal. After electrochemical processing, the working surface of sample was washed with distilled water and dried in air.
To obtain the hybrid PS–RGO nanostructures, graphene oxide produced by Biotool (Germany) in the form of an aqueous suspension (concentration of basic substance was 2 mg/ml) was used. A stable homogeneous suspension of the RGO was prepared by the reduction of aqueous dispersion of GO under action of hydrazine and treatment in an ultrasonic bath. The obtained RGO suspension was deposited onto a surface of porous layer and then dried at the room temperature during 48 h under dynamic vacuum.
Topology of hybrid PS–RGO structure was characterized by atomic-force microscope (AFM) “Solver Pro” and scanning electron microscope (SEM) “Selmi.” The electrical and photoelectrical properties of the samples were measured experimentally with standard techniques. The electrical current flowed through the structures in the direction perpendicular to their surfaces. The electrical parameters of the obtained nanosystems were investigated in both DC and AC regimes. The current–voltage characteristics (I-V curves) of sandwich structures based on PS were measured using AFM tip which was positioned on PS surface or RGO plate and using the indium tin oxide (ITO) contact, too. Impedance spectroscopy of the experimental samples was performed using R, L, and C measuring device E7-20 (“Kalibr,” Belarus) at room temperature in the frequency range of 25 Hz–1 MHz.
Photoelectric phenomena were investigated by irradiating the structures from the side of the porous layer with 1-W white LED (FYLP–1W–UWB–A) that provide light flux of 76 lm. Spectral dependencies of the photoresponse were measured using standard optical equipment, including a diffraction monochromator and a filament lamp (2800 K). Obtained spectra were normalized with respect to 2800 K black body radiation curve and were corrected taking into account the spectral sensitivity of our instrument. The spectral dependence of the photoinduced signal of an industrial silicon photodiode was also measured for a comparison. Kinetics of the photoresponse of hybrid PS–RGO structures to rectangular light pulses was examined using Hantek 1008B oscilloscope. UV–vis absorbance and transmittance spectra of the GO and RGO films on the glass substrate were measured in 220–1000-nm range using CM2203 spectrofluorometer (“Solar,” Belarus).
Results and Discussion
Meanwhile, we observed the decrease in light absorption in the RGO film as compared to GO in the near UV and blue part of the studied spectral range. It is usually attributed to n → π* transition of the carbonyl groups of GO [29, 32, 33]. This may indicate a high reduction degree of the GO in the RGO films. Such films have quite high optical transmittance in the visible region of the spectrum that allows their use as a protective coating and optically transparent electrode.
Under the influence of radiation with white light (76 lm flux), a photovoltage generation was observed and I-V curves of PS–RGO structures were changed similar to those of photodiodes (see Fig. 4b). The increase of the reverse current confirmed the photogeneration of free carriers in the structures under study. In the open-circuit regime, the photogenerated electron–hole pairs were separated at the potential barrier creating photovoltaic signal. The PS structure is characterized by lower photosensitivity compared to hybrid PS–RGO structures.
One has to note that infiltration of RGO nanosheets into PS can cause the formation of additional paths for current flowing through the porous layer and can ensure efficiency in collecting photogenerated carriers and extracting them from the bulk of PS layer.
Analyzing the obtained dependencies, one can conclude that hybrid PS–RGO structures have slightly smaller photoresponse times to green light as compared to IR radiation. The observed temporal parameters of the photoresponse to light pulses of different wavelengths can serve as an additional argument in favor of our hypothesis that various layers of the hybrid structure are responsible for the absorption of light quanta of different energy.
where Q is the CPE and n characterizes the heterogeneity of the electrical properties of the structure (−1 ≤ n ≤ 1). In case n = 1, CPE corresponds to the pure capacitance, and when n = 0, CPE transforms into the simple active resistance. In case of the R–CPE model, the approximation parameters of the PS impedance are R 2 = 16.4 MΩ, Q = 9.8 × 10−10 and n = 0.74. Analysis of the results shows that the electrical properties of the PS nanostructures are described better using the CPE in the equivalent circuit.
As it is evident from Fig. 7b, the contribution of active resistance R 0 of the silicon substrate and the supply contacts is negligibly small (real axis value intercept at ω = ∞ is about zero). Therefore, we do not consider this resistance in the impedance models for experimental PS–RGO structures.
Based on the approximation of the impedance spectra of PS–RGO structures, R V and R B values were determined to be 0.41 and 1.01 MΩ, respectively. Capacitance C V was about 5.1 nF. Parameters of CPE were Q = 1.27 × 10−7 and n = 0.37. We envisage that graphene sheets provide better connection between PS nanocrystals to improve electrical conductivity of PS–RGO nanosystem. This expands the prospect of hybrid structures as active materials for storage and conversion of energy.
In this study, we focused on novel technical solutions relevant for the design of photosensitive structures based on porous silicon. Photosensitive hybrid PS–RGO structures were created by the method of electrochemical etching of silicon wafer and deposition on the porous silicon layer of reduced graphene oxide prepared from water dispersion. Sponge-like morphology of PS favors the incorporation of RGO nanosheets into its bulk forming additional pathways for current flow through the porous layer. As a result, there are changes in electrical parameters of PS structures.
The internal resistance and electrical capacitance of PS-based structures were determined using the approximation of the impedance spectra. It was shown that the impact of RGO on electrical characteristics of PS manifests a reduction (about and order in magnitude) of the internal resistance of hybrid structures. By means of impedance spectroscopy, it was found that experimental structures show a decrease in electrical capacitance and internal resistance with increasing the frequency from the 25 Hz to 1 MHz.
The photovoltaic processes in hybrid nanostructures have been studied by means of comprehensive research of I-V curves and spectral and temporal dependencies of photoresponse of PS–RGO structures. The hybrid PS–RGO structures demonstrate the photovoltaic effect in the wide spectral range but have some peculiarities. Beside the intense band near 820 nm, the weak band of photosensitivity is observed in 500–600-nm range. It was found that the rise time and attenuation of photoinduced signal of experimental structures depends on the wavelength of the light pulses and is about 1 ms. A large surface area of PS provides effective absorption of light quanta of different energy and hence high photosensitivity of hybrid structures over a wide spectral range. The obtained experimental results can be used for the design of photodetectors and other optoelectronic devices based on PS nanocrystals.
Constant phase element
Indium tin oxide
- I-V curve:
Reduced graphene oxide
Scanning electron microscope
IBO designed the experiment, participated in the investigations of photoelectrical properties of the samples, and drafted the manuscript. OIA analyzed the optical properties of structures and finalized the manuscript. LSM analyzed the electrical properties of the samples. YYH synthesized the hybrid structures. MVP did the AFM investigations. All the authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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- Kim J, Joo SS, Lee KW, Kim JH, Shin DH, Kim S, Choi S-H (2014) Near-ultraviolet-sensitive graphene/porous silicon photodetectors. ACS Appl Mater Interfaces 6:20880–20886View ArticleGoogle Scholar
- Joo J, Kwon EJ, Kang J, Skalak M, Anglin EJ, Mann AP, Ruoslahti E, Bhatia SN, Sailor MJ (2016) Porous silicon–graphene oxide core–shell nanoparticles for targeted delivery of siRNA to the injured brain. Nanoscale Horiz 1:407–414View ArticleGoogle Scholar
- Ge D, Qian D, Chen G, Zhang L, Ren N (2016) Fabrication of graphene/porous silicon nitride material for field-effect transistors. ECS Trans 72(4):257–262View ArticleGoogle Scholar
- Jiao L-S, Liu J-Y, Li H-Y, Wu T-S, Li F, Wang H-Y, Niu L (2016) Facile synthesis of reduced graphene oxide-porous silicon composite as superior anode material for lithium-ion battery anodes. J Power Sources 315:9–15View ArticleGoogle Scholar
- Ge M, Rong J, Fang X, Zhang A, Lu Y, Zhou C (2013) Scalable preparation of porous silicon nanoparticles and their application for lithium-ion battery anodes. Nano Res 6(3):174–181View ArticleGoogle Scholar
- Geim AK, Novoselov KS (2007) The rise of graphene. Nat Mater 6:183–191View ArticleGoogle Scholar
- Shahil KMF, Balandin AA (2012) Thermal properties of graphene and multilayer graphene: applications in thermal interface materials. Solid State Commun 152:1331–1340View ArticleGoogle Scholar
- Erickson K, Erni R, Lee Z, Alem N, Gannett W, Zettl A (2010) Determination of the local chemical structure of graphene oxide and reduced graphene oxide. Adv Mater 22:4467–4472View ArticleGoogle Scholar
- Chakraborty T (2006) Graphene: a nanoscale quantum playing field. Phys Can 63:351–354Google Scholar
- Novoselov KS, Geim AK, Morozov SV, Jiang D, Katsnelson MI, Grigorieva IV, Dubonos SV, Firsov AA (2005) Two-dimensional gas of massless Dirac fermions in graphene. Nature 438:197–200View ArticleGoogle Scholar
- Zhang Y, Tan Y-W, Stormer HL, Kim P (2005) Experimental observation of quantum Hall effect and berry’s phase in graphene. Nature 438:201–204View ArticleGoogle Scholar
- Kim KS, Zhao Y, Jang H, Lee SY, Kim JM, Kim KS, Ahn J-H, Kim P, Choi J-Y, Hong BH (2009) Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457:706–710View ArticleGoogle Scholar
- Zhu Y, Murali S, Cai W, Li X, Suk JW, Potts JR, Ruoff RS (2010) Graphene and graphene oxide: synthesis, properties, and applications. Adv Mater 22:3906–3924View ArticleGoogle Scholar
- Shin DH, Lee CW, Lee JS, Kim JH, Kim S, Choi S-H (2014) Enhancement of the effectiveness of graphene as a transparent conductive electrode by AgNO3 doping. Nanotechnology 25:125701View ArticleGoogle Scholar
- Park S, Ruoff RS (2009) Chemical methods for the production of graphenes. Nat Nanotechnol 4:217–224View ArticleGoogle Scholar
- Eda G, Fanchini G, Chhowalla M (2008) Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material. Nat Nanotechnol 3:270–274View ArticleGoogle Scholar
- Li D, Müller MB, Gilje S, Kaner RB, Wallace GG (2008) Processable aqueous dispersions of graphene nanosheets. Nat Nanotechnol 3:101–105View ArticleGoogle Scholar
- Stankovich S, Dikin DA, Piner RD, Kohlhaas KA, Kleinhammes A, Jia Y, Wu Y, Nguyen ST, Ruof RS (2007) Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide. Carbon 45:1558–1565View ArticleGoogle Scholar
- Bisi O, Ossicini S, Pavesi L (2000) Porous silicon: a quantum sponge structure for silicon based optoelectronics. Surf Sci Rep 38:1–126View ArticleGoogle Scholar
- Ünal B, Parbukov AN, Bayliss SC (2001) Photovoltaic properties of a novel stain etched porous silicon and its application in photosensitive devices. Opt Mater 17:79–82View ArticleGoogle Scholar
- Bilyalov R, Stalmans L, Beaucarne G, Loo R, Caymax M, Poortmans J, Nijs J (2001) Porous silicon as an intermediate layer for thin-film solar cell. Sol Energ Mat Sol C 65:477–485View ArticleGoogle Scholar
- Monastyrskii LS, Aksimentyeva OI, Olenych IB, Sokolovskii BS (2014) Photosensitive structures of conjugated polymer—porous silicon. Mol Cryst Liq Cryst 589:124–131View ArticleGoogle Scholar
- Cullis AG, Canham LT, Calcott PDJ (1997) The structural and luminescence properties of porous silicon. J Appl Phys 82:909–965View ArticleGoogle Scholar
- Föll H, Christophersen M, Carstensen J, Hasse G (2002) Formation and application of porous silicon. Mat Sci Eng R 39:93–141View ArticleGoogle Scholar
- Kim J, Moon IS, Lee MJ, Kim DW (2007) Formation of a porous silicon layer by electrochemical etching and application to the silicon solar cell. J Ceram Soc Jpn 115:333–337View ArticleGoogle Scholar
- Wu K-H, Li C-W (2015) Light absorption enhancement of silicon-based photovoltaic devices with multiple bandgap structures of porous silicon. Materials 8:5922–5932View ArticleGoogle Scholar
- Peng KQ, Lee ST (2001) Silicon nanowires for photovoltaic solar energy conversion. Adv Mater 23:198–215View ArticleGoogle Scholar
- Oakes L, Westover A, Mares JW, Chatterjee S, Erwin WR, Bardhan R, Weiss SM, Pint CL (2013) Surface engineered porous silicon for stable, high performance electrochemical supercapacitors. Sci Reports 3:3020. doi:10.1038/srep03020 Google Scholar
- Olenych IB, Aksimentyeva OI, Monastyrskii LS, Horbenko YY, Partyka MV, Luchechko AP, Yarytska LI (2016) Effect of graphene oxide on the properties of porous silicon. Nanoscale Res Lett 11:43View ArticleGoogle Scholar
- Bae S, Kim H, Lee Y, Xu X, Park J-S, Zheng Y, Balakrishnan J, Lei T, Kim HR, Song YI, Kim Y-J, Kim KS, Özyilmaz B, Ahn J-H, Hong BH, Iijima S (2010) Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nat Nanotechnol 5:574–578View ArticleGoogle Scholar
- Anagnostopoulos G, Pappas PN, Li Z, Kinloch IA, Young RJ, Novoselov KS, Lu CY, Pugno N, Parthenios J, Galiotis C, Papagelis K (2016) Mechanical stability of flexible graphene-based displays. ACS Appl Mater Interfaces 8(34):22605–22614. doi:10.1021/acsami.6b05227 View ArticleGoogle Scholar
- Dovbeshko GI, Romanyuk VR, Pidgirnyi DV, Cherepanov VV, Andreev EO, Levin VM, Kuzhir PP, Kaplas T, Svirko YP (2015) Optical properties of pyrolytic carbon films versus graphite and graphene. Nanoscale Res Lett 10:234View ArticleGoogle Scholar
- Kazi SN, Badarudin A, Zubir MNM, Ming HN, Misran M, Sadeghinezhad E, Mehrali M, Syuhada NI (2015) Investigation on the use of graphene oxide as novel surfactant to stabilize weakly charged graphene nanoplatelets. Nanoscale Res Lett 10:212View ArticleGoogle Scholar
- Olenych IB, Monastyrskii LS, Aksimentyeva OI, Sokolovskii BS (2013) Effect of bromine adsorption on the charge transport in porous silicon—silicon structures. Electron Mater Lett 9:257–260View ArticleGoogle Scholar
- Olenych I, Tsizh B, Monastyrskii L, Aksimentyeva O, Sokolovskii B (2015) Preparation and properties of nanocomposites of silicon oxide in porous silicon. Solid State Phenom 230:127–132View ArticleGoogle Scholar
- Bellucci S, Bolesta I, Karbovnyk I, Hrytskiv R, Fafilek G, Popov AI (2008) Microstructure of Ag2BI4 (B = Ag, Cd) superionics studied by SEM, impedance spectroscopy and fractal dimension analysis. J Phys Condens Matter 20:474211View ArticleGoogle Scholar
- Karbovnyk I, Borshchyshyn I, Vakhula Y, Lutsyshyn I, Klym H, Bolesta I (2016) Impedance characterization of Cr3+, Y3+ and Zr4+ activated forsterite nanoceramics synthesized by sol–gel method. Ceram Int 42:8501–8504View ArticleGoogle Scholar
- Karlach AY, Kuznetsov GV, Litvinenko SV, Milovanov YS, Skryshevsky VA (2010) The effect of the dynamic adsorption mode on impedance of composite structures with porous silicon. Semiconductors 44:1342–1348View ArticleGoogle Scholar