Structural and Photoelectric Properties of Epitaxially Grown Vanadium Dioxide Thin Films on c-Plane Sapphire and Titanium Dioxide

Creeden, Jason A.; Madaras, Scott; Beringer, Douglas; Beebe, Melissa; Novikova, Irina; Lukaszew, R. A.

doi:10.1038/s41598-019-45806-8

Cited by 12 publications

(8 citation statements)

References 27 publications

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“…The sharpness of the VO 2 peak was consistent with previous studies for epitaxial VO 2 on TiO 2 substrates . Additionally, the previous studies on VO 2 grown on TiO 2 substrates with reflection high energy electron diffraction (RHEED) reaffirm the epitaxy of the film growth . The XRD was additionally used to characterize the mosaicity (degree of crystallite order), grain size of the crystallites, and lattice parameter as shown in Table .…”

Section: Methodssupporting

confidence: 85%

Growth and Characterization of Vanadium Dioxide/Niobium Doped Titanium Dioxide Heterostructures for Ultraviolet Detection

Creeden

Madaras

Beringer

et al. 2019

Advanced Optical Materials

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heterostructures from many other materials recently proposed for highly efficient UV detection such as AlGaN, [6][7][8][9] β-Ga 2 O 3 , [10,11] GaN, [7,12] TiO 2 , [13] Zn 2 GeO 4 , [14] ZnMgO, [15] and ZnO. [16,17] These materials tend to have properties that are a detriment for practical commercial implementations, as they tend have narrow detection bandwidths, [7][8][9][10]12,14] require a voltage bias, [7,8,10,[12][13][14][15][16][17] and/or may require complicated fabrication methods hindering production scalability. [6,10,11,16] On a contrary, the deposition of the VO 2 films via magnetron sputtering is a cost efficient, scalable production technique being suitable for practical device development and production. That fact, in addition to its highefficiency broadband UV detection with zero bias at convenient temperature range asserts the VO 2 /TiO 2 :Nb heterostructure as a novel, promising approach to addressing the need for efficient UV detection.To determine the photoconductive properties of our detectors, we used a four-point probe measurement system for photocurrent detection via four beryllium copper probes on the surface of the VO 2 film under 0 V bias. Typical photocurrent and dark current measurements are shown in Figure 1a), where we define the dark current as a residual low current measured in absence of any illumination; typically, it is associated with thermal fluctuations within the sample. [18] By subtracting the dark current from the photocurrent ΔI, we calculated the EQE and responsivity R λ of the heterojunction using the following equations [19][20][21][22][23] EQE hcR eλ = λ (1)Here P is the total detected light power, λ is the excitation wavelength, h is the Plank constant, e is the electron charge, and c is the speed of light in vacuum. Figure 1b shows the quantum efficiency measured for a 15 nm VO 2 film, measured for both, near UV (NUV) and UV-C light with varied optical powers. While we observed a gradual increase in EQE for lower powers, we consistently measured EQE above 100% in The properties of VO 2 /TiO 2 :Nb heterostructures are engineered for their potential use in ultraviolet (UV) detection and observed external quantum efficiency (EQE) exceeding 100% in both near UV (405 nm) and UV-C (254 nm) spectral regions. The proposed UV detection scheme is based on vanadium dioxide (VO 2 ) thin films epitaxially grown on niobium doped titanium dioxide (TiO 2 :Nb). Such VO 2 /TiO 2 :Nb heterostructure exhibits enhanced photocurrent due to cation doping engineering in a space-charge region thus yielding favorable conditions for hole tunneling from TiO 2 :Nb into VO 2 . The heterostructure is engineered and photocurrent is optimized by varying the VO 2 film thickness, reaching up to 5000% EQE for 405 nm and up to 17 000% EQE for 254 nm light, indicating that the VO 2 /TiO 2 :Nb system can be fine-tuned for efficient UV photodetection.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901143.Wide bandgap semiconductors f...

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Section: Methodssupporting

confidence: 85%

Growth and Characterization of Vanadium Dioxide/Niobium Doped Titanium Dioxide Heterostructures for Ultraviolet Detection

Creeden

Madaras

Beringer

et al. 2019

Advanced Optical Materials

Self Cite

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“…A high resolution TEM image of VO x particles (Figure 1c, inset) shows a lattice spacing of 0.27 nm, indicating the presence of monoclinic vanadium dioxide (M1) in agreement with literature. [31,32] Next, we use x-ray diffraction (XRD) to assess the homogeneity of the crystalline structure across a large area drop cast film (Figure 1d). The peaks identified are in alignment with monoclinic VO 2 (JCPDS, No.…”

Section: Resultsmentioning

confidence: 99%

“…The existence of V 5+ is due to the rapid surface oxidation of VO 2 and is commonly seen in non‐passivated VO x films. [ 31,32 ] At the O1 s peak, a shoulder corresponding to OH is also seen, due to adsorption of moisture on the surface. Figure 1f plots the Raman spectrum of the VO x film.…”

Section: Resultsmentioning

confidence: 99%

Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature

Balendhran

Taha

Wang

et al. 2023

Adv Funct Materials

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Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VOx nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 µm. This ink is synthesized using a simple and scalable wet‐chemical process. These photodetectors operate at room temperature and exhibit minimal variance in performance even when bent at angles of up to 100 ° at a bend radius of 6.4 mm. In addition, rigorous strain testing of 100 bend and release cycles revealed a photoresponse with a standard deviation of only 0.55%. This combination of mechanical flexibility, wide spectral response, and ease of fabrication makes these devices highly desirable for a wide range of applications, including low‐cost wearable sensors and hyperspectral imaging systems.

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“…The grain size in the films on sapphire substrates decreases from 153 nm to 108 nm as T S is lowered from 600 to 500 °C. Indeed, near-epitaxial growth on sapphire films has been reported in the literature [ 37 ]. On the other hand, the grain size of the films prepared on Si substrates, within experimental uncertainties, does not exhibit any compelling dependence on T S , even though there is seemingly a maximum average grain size at T S = 600 °C.…”

Section: Resultsmentioning

confidence: 99%

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films

et al. 2022

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This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that TS below 500 °C favors the growth of V2O5 phase, whereas higher TS (≥500 °C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (Tt), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at TS lower than 650 °C presents significant challenges.

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Structural and Photoelectric Properties of Epitaxially Grown Vanadium Dioxide Thin Films on c-Plane Sapphire and Titanium Dioxide

Cited by 12 publications

References 27 publications

Growth and Characterization of Vanadium Dioxide/Niobium Doped Titanium Dioxide Heterostructures for Ultraviolet Detection

Growth and Characterization of Vanadium Dioxide/Niobium Doped Titanium Dioxide Heterostructures for Ultraviolet Detection

Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films

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