Open Access
Add to BibSonomy
Abstract
Vanadium dioxide nanoparticles (VO2) NPs have been demonstrated to create a thin film based for photodetectors which are controlled by size, shape, and morphology of materials in nanoscale by using hydrothermal method. Analyses from XRD, AFM and FT-IR showed that crystallite size = 12.92 nm, particle size = 16 nm, root mean-square of roughness = 21.3 respectively as well as, the transmittance reaches 96%. The results agree with optical properties where energy gap of samples = 1.36. The proposed results, for the Ag/VO2/PSi/n-Si/Ag heterojunction photo-detector are considerably better than other photodetectors. Responsivity of detector 0.9A/W at 915 nm and maximum value of detectivity D* 3.3 × 1012 W-1. cm. Hz0.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Most of the research areas in this field based on nanotechnology. Due to their nanoscale of the size for the nanoparticles (NPs) which, displayed considerably innovative and enhanced the physical, and the chemical capabilities and effect the characteristics of the form for practical`s size and distortions when compared to the form of bulk materials. There are many approaches have been advanced to create nanoparticles with higher surface area according to a significant progress in recent years for many applications employ nanoparticles and nanomaterials [1,2]. Typically, different etching techniques result in layers of porous silicon being created on the surface of a silicon substrate. Porous silicon (PS) is silicon that is penetrated by air gaps and has a complicated, spongy structure. Because of its superior optical, mechanical, and electrical properties and low cost, it is a promising in many applications [3]. The silicon in this situation is utilized as anode and metal as a cathode (Au, Pt) with a solution of hydrogen fluoride (HF) to be an electrolyte [4]. Therefore, the etching process changes in the porosities caused by changing the current densy, etching time, HF concentration, illumination strength, and the wavelength. A well-known “smart substance,” vanadium dioxide (VO2) has gained popularity since Morin work in 1959 [5] near room temperature, its monoclinic M1 phase displays a metal-insulator transition (MIT), which supplemented by significant alterations in the structural, electrical, and optical characteristics [6]. In addition, there are many ranges of V: O ratios that the vanadium oxides can yield, leading to various structural motifs. More than 15 additional stable vanadium oxides phases can be found in vanadium oxides, VO2 such as, (VO, V2O3, V3O5 etc.). several stoichiometric VO2 polymorphs have been become stable via methods such as pulsed laser deposition (PLD), sputtering, reactive evaporation, sol–gel deposition, and metal–organic chemical vapor deposition (MOCVD) etc. [7,8]. A solution-based deposition approach is always plagued by several processes, small-scale manufacturing, and inferior purity. Vapor deposition is an effective method for producing high-quality VO2-films, but the equipment needed is typically expensive and complicated [9–11]. Furthermore, vanadium dioxide is a usual metal-insulator conversion (MIT) material, which can be altered at room-temperature from insulating phase to metallic phase. This means the transition of VO2 is rapidly changes in conductance and optical transmittance due to the characteristics of VO2, so that, it has been widely used in smart windows, sensors, and actuators [12–14]. Several nanostructures of material fabrication technology, such as, low- dimensional structures (LDSs), nanorods (NRs), nanosheets (NSs), nanowire(NWs) and nanobelts (NBs), show that the feature of the electrical, the mechanical and the optical properties changed according to the size and the surface of the interface effect, therefore, it become one of significant a metal oxide in the recent years. Hydrothermal has made significant strides in managing the properties of VO [15,16]. The purpose of the work is to manufacture VO2 nanoparticles using a hydrothermal method to synthesize VO2: PVP in CH3 OH at various concentrations and placed on porous silicon. The presence of Vanadium dioxide (VO2) nanoparticles on the surface produces composites with increased surface area of exposed electrolyte, which ultimately enhances electro-optical performance. Implementation and experimental tested to prepare the characteristics of vanadium dioxide nanostructures and its application for Nano phonics devices. Finally, a significant enhancement in photo response of VO2 photodetectors could be achieved by optimizing the VO2 devices size and substrates type. The broadband photo-response VO2 opens opportunities for designing and controlling the performance of VO2 for scalable Micro and Nano-scale devices.
2. Experimental part
The preparation of nanoparticles material by hydrothermal method. Firstly, by using 1.8 g powder of material was added into (100) ml of distilled water, the solution sited on magnetic stirrer for 15 min at (50) C°, after preservation to room temperature. (1) g polyvinylpyrrolidone PVP added to 50ml of CH3 OH where preparation different concentration of materials (1:9,1.5:8.5 and 2:8). Also, (2) g PVP added to 50ml of CH3 OH to prepare other concentrations of materials (1:9,1.5:8.5 and 2:8) as shown in Fig. 1, the silicon wafer was chosen n-type with orientation (111), resistivity (1.5-°4) Ω.cm.
Fig. 1. Preparation of VO2 NPs with different concentrations (1:9, 1.5:8.5 and 2:8) by hydrothermal method.
Secondly, silicon wafer cutting into small slides with dimensions (1.5 × 1.5) cm and rinsed with CH3 OH to remove dirt and remove the native oxide layer on the samples for 10 sec. After cleaning, it immerses in HF (40%)-CH3 OH (99.99) (1:1) mixture at room temperature. The cell used in this process is made of Teflon that resistive against Hydrofluoric acid. The shiny surface of the slide placed toward the light source; the holes were prepared (positive charge) necessary to carry out the etching process to prepare PSi.
Thirdly, Au ring used as an electrode and the light source used a Halogen lamp with a light intensity of the amount (100) mW/m, which provides lighting intensity with a uniform distribution to ensure homogeneity of the etch layer, where the intensity of the lighting is controlled by moving the light source as shown in Fig. 2, 10 mA/cm2 current density applied for the period (10 min) to yields an imprinted area of the sample around (0.785 cm2).
To prepare thin films by drop casting method as shown in Fig. 3. An amount of the solutions is withdrawn by pipette, where four drops of solution are placed on glass substrates at 60C° to form thin films. Thin films of compounds (VO2) deposited on a PSi slide.
Finally, Ag electrodes deposited on the top and bottom surface and connected to the circuit as shown in Fig. 4 in order to measure the properties of photodetectors. When the light strikes the sensor or the detector, the photons excited the electrons to upper energy levels resulting toward the formation of electrical charge carriers (e or h) that keep on inside the device. This detector converts photons in a straight line into free current carriers. For the valence electrons to be excited, the incident photon's energy must be equivalent to or larger than band gap energy.
3. Results and discussion
The structural, electrical and optical properties of VO2 have been studied, and the optoelectronic properties of VO2: PVP/PSi/and-Si Heterojunction have been analyzing the photodetector parameters properties. Figure 5, display the results of X-ray diffraction for that VO2 thin film which, placed on the glass substrate by using the drop casting method. It observed that the film polycrystalline structure, with 14 peaks in the diffraction spectrum which are (001), (110), (002), (-401),(-311), (401), (112),(-601), (020), (113), (-711), (403), (023) and (712). This match with [17]. The robust and fine peak may be certified to the special growing along (110) plane of VO2 crystallites.
The crystallite size (D) value of VO2 film calculated by Scherer equation was 12.92 nm is given by Eq. (1):
The measuring of half width of peak maximum intensity (FWHM), and (2θ) of the directions peaks. The micro strain (δ) and dislocation density (η) were calculated and listed in Table 1, are given by Eqs. (2) and (3), respectively:
Table 1. Summery of XRD characterization for VO2 powder
Atomic force microscopy (AFM) analysis investigated surface morphology VO2 where the atomic force microscopy analysis showed a porous free morphology with homogeneity on the sample surface. Figure 6 displays the 3D AFM micrographs and the histogram of VO2 film. The film surface didn't seem to be cracked. Large, neatly separated conical columnar growth coupled grains were presented across the surface of the grains, with some of the columnar grains. coalescing a few spots. It had a root mean square(RMS) roughness 21.3 nm and an average particle size 1nm. To calculate the indirect bandgap (Eg) of the films, Tauc relation is used as shown Fig. 7. The optical bandgap was calculated by the plot of (αhν)2 against (hν), are given by Eqs. (4) and (5). The energy band gap (Eg) was estimated by extrapolating the line. Eg value = (1.36) Ev.
where B is absorption coefficient and n equal 0.5 is the exponent determines the transition type.And :
(t) the thickness and (hv) photon energy.The transmittance spectra of the prepared VO2 NPs, as shown Fig. 8 at range (200-1100) nm at room temperature, it observed that the VO2 NPs is capable of absorbing a small amount of visible light; because of the average transmittance of the thin films transmittance reach 96%, where the high transmittance in visible spectrum is preferred in solar-cell fabrications [18–20]. The transmittance can vary depending on the surface roughness, grain size and defects in the prepared thin films.
The spontaneous emission of the light from a substance under the optical stimulation is known as photoluminescence (PL). The majority of semi-conductors have been subjected to PL measurement, which is a form of effective and nondestructive approach. When a substance is irradiated by the light with enough energy, photons are absorbed and excitations are produced. These energized carriers release a photon as they unwind. However, absorption in materials is only possible when the photon energy is greater than the band gap or equal to it [21]. The peak at wavelength 900 nm of the PL spectra exhibited. Figure 9 shows the absorption of the edge signified that luminescence VO2 thin film. where energy gap of the samples was (1.36) eV, are in agreement with the optical characteristics.
The Fourier transform infrared (FTIR) spectra of VO2 thin film as shown Fig. 10 the distinctive wide absorption bands at 3450 and 3431 (1/cm) in the sample are attributed to the stretching and the bending vibrations of the hydroxyl group (OH), which are caused by the absorbed H2O molecules on the surface of VO2, respectively. The C = C bond is responsible for the absorption band at wavelengths of 2362 and 2358 (1/cm). The peaks at (1652, 1655), 1658 and 1617(1/cm) due to vibration of C = O, N-O and C = C respectively. While the peak at (1457, 1143), 1138 and 1056 (1/cm) are ascribed to the C = H, C-N and C-O respectively. the V-O symmetric stretch around 500,540 cm-1 and the V-O-V asymmetric stretch at 770 (1/cm) [22,23].
Optoelectronic properties of photodetector due to the absorption edge of VO2. The spectral responsivity of structures investigated in the wavelength range of (350–1000) nm with 1.5V bias using the equation below.
where Iph: photocurrent and pin input power.The structure consists of two heterojunctions. In the first place, heterojunction is between the VO2 layer and porous silicon (VO2/PSi) and, the second heterojunction is between the porous silicon layer and crystalline (substrate) silicon (PSi/n-Si). Therefore, the VO2 /PSi/n-Si have two depletions regions. The obtained results to characterized the parameter responsivity depends on the photocurrent and dark current. Firstly, Fig. 11(a-c). Display the spectral responsivity as a function of wavelength (350–1000) nm of structure VO2/PSi/n-Si with diverse concentration (1:9,1.5:8.5 and 2:8) with (1) g PVP:CH3 OH. It also observed the spectral responsivity curve consists of three peaks of response. The first peak is 750 nm due to the PSi nanoparticles absorption edge. Whereas, another region is 850 nm due to the silicon absorption edge and last peak at 908- 915 nm due to absorption edge of VO2. As well as, Fig. 12(d-f) shows the spectral responsivity as a function of wavelength (350–1000) nm of structure VO2/PSi/n-Si with diverse concentration (1:9,1.5:8.5 and 2:8) with (2) g PVP:CH3 OH.
Fig. 11. (a) Responsivity against wavelengths of VO2/PSi/ n- Si photo detector at (1:9) with (1) g PVP:CH3 OH. (b) Responsivity against wavelengths of VO2/Posi/ n- Si photo detector at (1.5:8.5) with (1) g PVP:CH3 OH. (c) Responsivity against wavelengths of VO2/PSi/ n- Si photodetector at (2:8) with (1) g PVP:CH3 OH.
Fig. 12. (d) Responsivity against wavelengths of VO2/PSi/ n- Si photo-detector at diverse concentrations (1:9) with (2) g PVP:CH3 OH. (e) Responsivity against wavelengths of VO2/PSi/ n- Si photodetector at (,1.5:8.5) with (2)g PVP:CH3 OH. (f) Responsivity against wavelengths of VO2/PSi/ n- Si photo-detector at (2:8) with (2)g PVP:CH3 OH.
Secondly, Fig. 13(a-c) and Fig. 14(d-f) represent the relationship between the specific detectivity with wavelengths for VO2/PSi/n-Si and VO2/PSi/n-Si photodetectors at diverse concentration (1:9,1.5:8.5 and 2:8) with (1) g PVP:CH3 OHs and (1:9,1.5:8.5 and 2:8) with (2) g PVP:CH3 OH respectively. It shows very clear that the detectivity depend directly on the responsivity. Where, specific detectivity curve consists of three peaks are located visible and near infrared region. The highest value of the detectivity is found to be 3.3 × 1012 W-1 cm. Hz1/2 at wavelength 919 nm for sample (c) as indicated in Fig. 13(c), which represented VO2/PSi/n-Si photodetector at (2:8) with (1) g PVP:CH3 OH. While in the second case, maximum value of detectivity D* is found to be 1.4 × 1013 W-1 cm. Hz1/2 at wavelength 915 nm for sample (d), as indicated Fig. 14(d), which represented VO2/PSi/n-Si photodetector at (1:9) with (2) g PVP:CH3 OH.
Fig. 13. (a) Spectral detectivity plots for VO2/PSi/n-Si photodetector at (1:9) with (1) g PVP:CH3 OH. (b) Spectral detectivity plots for VO2/PSi/n-Si photodetector at (1.5:8.5) with (1) g PVP:CH3 OH. (c) spectral detectivity plots for VO2/PSi/n-Si photodetector at (2:8) with (1) g PVP:CH3 OH.
Fig. 14. (d) Spectral detectivity plots for VO2/PSi/n-Si Photodetector at (1:9) with (2) g PVP:CH3 OH. (e) Spectral detectivity plots for VO2/PSi/n-Si photodetector at (1.5:8.5) with (2) g PVP:CH3 OH. (f) Spectral detectivity plots for VO2/PSi/n-Si photodetectors at (2:8) with (2) g PVP:CH3 OH.
Figure 15(a-c) represents lifetime of structure VO2/PSi/n-Si heterojunction with different concentration (1:9,1.5:8.5 and 2:8) with (1) g PVP:CH3 OH. Lifetime is the charge carriers, which can be defined as the time required for not accrue recombination between the electrons and the holes, which providing the time required for both the holes current and the electrons current to generate the necessary current. Figure 16(d-f) represents lifetime of VO2/PSi/n-Si heterojunction with different concentration (1:9,1.5:8.5 and 2:8) with (2) g PVP:CH3 OH. Time calculated from the inverse of the frequency. Results are summarized for VO2/PSi/n-Si heterojunction with different conditions in Table 2. By using open circuit voltage decay (OCVD) which defined as an advancing analysis with a simple construction test. Today`s the carrier lifetime is an important parameter for semiconductor and MIT industry since it impacts on the performances of many devices, such as silicon-on-insulator (SOI), power devices, photodetectors and solar cells. The forward current flows through the device, then the circuit is abruptly opened and the forward voltage drop decay is measured. The accuracy of the OCVD measurement depends on the precision of the oscilloscope, the temperature measurement and, the affected noise.
Fig. 15. (a-c) Images lifetime of structure VO2/PSi/n-Si at different concentrations (1:9,1.5:8.5 and 2:8) with (1) g PVP:CH3 OH.
Fig. 16. (d- f) Images lifetime of structure VO2/PSi/n-Si at different concentrations (1:9,1.5:8.5 and 2:8) with (2) g PVP:CH3 OH.
Table 2. Result lifetime of structure VO2/PSi/n-Si with different conditions
4. Performance of VO2/PSi/n-Si photodetector devices
The performance parameters included external quantum efficiency (%EQE), responsivity, and specific detectivity are calculated. EQE is photodetector `s electrical sensitivity to light in order to determine the number of photo induced carriers per incident photons is given by Eq. (7):
where, Rλ the responsivity of the photodetector, h is the plank`s constant, c is the velocity of the light, λ is the wavelength of light illumination, and e is the charge of electrons. In the term of the responsivity and specific detectivity of the fabricated VO2/PSi/n-Si photodetectors at room temperature and, biasing voltage 1.5 V, (%EQE) = 96.818. The performance parameters of VO2 photodetectors are enhanced significantly beyond transition when compared with other parameters of ($R\lambda ,\,D *$, and wavelengths) to commercial photodetectors of diverse references are presented in Table 3.Table 3. Performance of photodetectors: key performance parameters of different photodetectors
5. Conclusion
In conclusion, this work demonstrated how to create VO2 thin films in a simple method and, low-cost to fabricate photodetectors which apply in many applications. Our results allow us to conclude that, the vanadium dioxide VO2 NPs which are prepared by hydrothermal approach have been shown a good specific responsivity and a good specific detectivity for all samples. And an average transmittance of that film reaches 96%, The results are encouraging to study VO2 in the future more extensively for the explore its potential in solar cell applications as window layer because of high transparency at wavelength larger than >400 nm, and also, in the window of the optical communications network at the wavelength equal and larger more than ≥ 850 nm.
Acknowledgments
Dr. S. M. Thahab conceived the experiments. Dr. S. M. Thahab and Dr. Alaa H. Ali planned and supervised the project. Dr Maysoon H. Ismail carried out the experiments. Dr. Alaa H. Ali and Dr Maysoon H. Ismail contributed to samples preparation. Dr. Maysoon H. Ismail contributed to the interpretation of the results and, took the lead in writing the manuscript. All authors provided critical feedback and helped shape the research, analysis and manuscript.
Disclosures
The authors declare that they have no conflicts of interest.
Data availability
Data underling the results presented in this paper are not publicly available at this time but be obtained from the corresponding author upon reasonable request.
References
1. Bhushan Bharat, Springer Handbook of Nanotechnology: Springer Science and Business MediaSpringer, 2nd ed.,Springer (2010).
2. F. Allhoff, P. Lin, and D. Moore, “What is nanotechnology and why does it matters: from science to ethics,” Journal of Bioethical Inquiry 8(2), 209–211 (2011). [CrossRef]
3. U. M. Nayef and M. W. Muayad, “Typical of Morphological Properties of Porous Silicon,” International Journal of Basic and Applied Sciences 13(2), 15–17 (2013).
4. H. S. Mavi, B. G. Rasheed, A. K. Shukla, and S. C. Abbi, “Spectroscopic Investigations of Porous Silicon Prepared by Laser-Induced Etching of Silicon,” J. Phys. D: Appl. Phys. 34(3), 292–298 (2001). [CrossRef]
5. S. Majid, D. Shukla, K. Rahman, F. Khan, and S. Gautam, “Insulator-metal transitions in the T Phase Cr doped and M1 phase undoped VO2 thin films,” Phys. Rev. B 98(7), 075152 (2018). [CrossRef]
6. Ming Li, Shlomo Magdassi, Yanfeng Gao, and Yi Long, “Hydrothermal synthesis of VO2 polymorph Advantages, challenges and prospects for the application of energy efficient smart windows,” Small 13(36), 1701147 (2017). [CrossRef]
7. A. Srivastava, H. Rotella, and S. Saha, “Selective growth of single phase VO2(A, B, and M) polymorph thin,” APL Mater. 3(2), 026101 (2015). [CrossRef]
8. M. M. Seyfouri and R. Binions, “Sol-gel approaches to thermochromic vanadium dioxide coating for smart glazing application,” J. Sol Mat. 159, 52–65 (2016). [CrossRef]
9. S. Wanga, M. Liua, L. Kongb, et al., “Recent progress in VO2 smart coatings: Strategies to improve the thermochroic properties,” Prog. Mater. Sci. 81, 1–54 (2016). [CrossRef]
10. L. Yan, P. Gopinath, and S.C.P. Anbu, “Characterization and anti-bacterial potential of iron oxide nanopsarticle processed eco-friendly by plant extract,” Prep. Biochem. Biotechnol. 50(10), 1053–1062 (2020). [CrossRef]
11. K. Sieradzka, D. Wojcieszak, and D. Kaczmarek, “Structural and optical properties of vanadium oxides prepared by microwave-assisted reactive magnetron sputtering,” Opt. Appl. 41(2), 463–469 (2011).
12. K. Abbas, J. Hwang, and G. Bae, “Control of multilevel resistance in dielectrics vanadium dioxide by electric field using hybrid,” ACS Appl. Mater. Interfaces 9(15), 13571–13576 (2018). [CrossRef]
13. S. Chen, Z. Wang, and H. Ren, “Gate-controlled VO2 phase transition for high-performance smart windows,” Sci. Adv. 5(3), 6815 (2019). [CrossRef]
14. J.C. Wu, Z. Wu X, and J. Wang, “Terahertz transmittance and metal-insulator phasetransition properties of M2 phase VO2 films induced by Cr doping,” Appl. Surf. Sci. 455, 622–628 (2018). [CrossRef]
15. Z. Zhang, H. Guo, and W. Ding, “Nanoscale engineering in VO2 nanowires via direct electron writing process,” Nano Lett. 17(2), 851–855 (2017). [CrossRef]
16. Clarke H. Caraway, B.D. Sellers, and D.G. Braham, “Nucleation controlled hysteresis in unstrained hydrothermal VO2 particles,” Phys. Rev. Mater. 2(10), 103402 (2018). [CrossRef]
17. Yifu Zhang, “VO2(B) Conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties,” Mater. Sci.-Pol. 34(1), 169–176 (2016). [CrossRef]
18. A. Boutlala, F. Bourfaa, and M. Mahtili, “Deposition of Co-doped TiO2 thinfilmmethod,” IOP Conf. Ser. Mater. Sci. Eng. 108, 12048 (2016). [CrossRef]
19. Krystyna Schneider, “Optical properties and electronic structure of V2O5, V2O3 and VO2,” J. Mater. Sci.: Mater. Electron. 31(13), 10478–10488 (2020). [CrossRef]
20. M. Benhaliliba, C. E. Benouis, and F. Yakuphanoglu, “Luminescence and physical properties of copper doped CdO derived nanostructures,” J. Lumin. 132(10), 2653–2658 (2012). [CrossRef]
21. Majid Farahmandjou and Nilofar Abaeiyan, “Chemical synthesis of vanadium oxide (V2O5) nanoparticles prepared by sodium metavanadate,” Journal of Nanomedicine Research 5, 1 (2017). [CrossRef]
22. N. Naresh, R. Kumuthini, and A.T. Helen, “Low temperature synthesis of Vanadium chalcogenide nanostructures from VOx nanostructures,” International Journal of ChemTech Research 7(3), 1569–1573 (2015).
23. Shan Liang, Qiwu Shi, Hongfu Zhu, and Bo. Peng, “One-Step,” https://www.researchgate.net/scientific-contributions/Bo-Peng-2113503145 (2016).
24. J. D. Yao, Z. Zheng, and J. M. Shao, “Stable, highly-responsive and broadband photodetection based onlarge-area multilayered WS2 films grown by pulsed-laser deposition,” Nanoscale 7(36), 14974–14981 (2015). [CrossRef]
25. M. M. Samani, “Pulsed laser deposition of photoresponsive two-dimensional GaSe nanosheetnetworks,” Adv. Funct. Mater. 24(40), 6365–6371 (2014). [CrossRef]
26. H. J. Song, “High-performance copper oxide visible-light photodetector via grainstructure model,” Sci. Rep. 9(1), 1–10 (2019). [CrossRef]
