Highlights
A zero-reflection-induced phase singularity is achieved through precisely controlling the resonance characteristics using two-dimensional nanomaterials.
An atomically thin nano-layer ...having a high absorption coefficient is exploited to enhance the zero-reflection dip, which has led to the subsequent phase singularity and thus a giant lateral position shift.
We have improved the detection limit of low molecular weight molecules by more than three orders of magnitude compared to current state-of-art nanomaterial-enhanced plasmonic sensors.
Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer, monitoring treatment and detecting relapse. Here, a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial. By precisely engineering the configuration with atomically thin materials, the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect. Based on our knowledge, it is the first experimental demonstration of a lateral position signal change > 340 μm at a sensing interface from all optical techniques. With this enhanced plasmonic effect, the detection limit has been experimentally demonstrated to be 10
–15
mol L
−1
for TNF-α cancer marker, which has been found in various human diseases including inflammatory diseases and different kinds of cancer. The as-reported novel integration of atomically thin Ge
2
Sb
2
Te
5
with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.
•Growth of epitaxial VO2 films on sapphire by DC Reactive magnetron sputtering.•Films exhibit state of the art five orders of magnitude electrical resistivity change.•Electrical performances highly ...influenced by the deposition and annealing temperatures.•Excellent reproducibility and stability of thermal switching.
Epitaxial vanadium dioxide (VO2) films exhibiting an abrupt metal-insulator transition with resistivity ratios of five orders of magnitude have been grown on (001)-oriented sapphire substrates by reactive magnetron sputtering. The influence of deposition and annealing temperature on the structure and morphology of the layers are discussed as well as their impact on the films’ electrical properties. Thus, the VO2 layers obtained using the optimal experimental conditions have electrical resistivity ratios over 105 and can be obtained on substrates as large as three-inch in diameter. The combination of the scalability of magnetron sputtering and the high quality of the films enables the large-scale industrial applications of high quality VO2 layers.
In this paper, we demonstrated the ability of a plasmonic metasensor to detect ultra-low refractive index changes (in the order of ∆n = 10−10 RIU), using an innovative phase-change material, vanadium ...dioxide (VO2), as the sensing layer. Different from current cumbersome plasmonic biosensing setups based on optical-phase-singularity measurement, our phase signal detection is based on the direct measurement of the phase-related lateral position shift (Goos–Hänchen) at the sensing interface. The high sensitivity (1.393 × 108 μm/RIU for ∆n = 10−10 RIU), based on the Goos–Hänchen lateral shift of the reflected wave, becomes significant when the sensor is excited at resonance, due to the near-zero reflectivity dip, which corresponds to the absolute dark point (lower than 10−6). GH shifts in the order of 2.997 × 103 μm were obtained using the optimal metasurface configuration. The surface plasmon resonance (SPR) curves (reflectivity, phase, GH) and electromagnetic simulations were derived using the MATLAB programming algorithm (by the transfer matrix method) and Comsol modeling (by finite element analysis), respectively. These results will provide a feasible way for the detection of cancer biomarkers.
Abstract
The mid-infrared spectral region opens up new possibilities for applications such as molecular spectroscopy with high spatial and frequency resolution. For example, the mid-infrared light ...provided by synchrotron sources has helped for early diagnosis of several pathologies. However, alternative light sources at the table-top scale would enable better access to these state-of-the-art characterizations, eventually speeding up research in biology and medicine. Mid-infrared supercontinuum generation in highly nonlinear waveguides pumped by compact fiber lasers represents an appealing alternative to synchrotrons. Here, we introduce orientation-patterned gallium arsenide waveguides as a new versatile platform for mid-infrared supercontinuum generation. Waveguides and fiber-based pump lasers are optimized in tandem to allow for the group velocities of the signal and the idler waves to match near the degeneracy point. This configuration exacerbates supercontinuum generation from 4 to 9 µm when waveguides are pumped at 2750 nm with few-nanojoule energy pulses. The brightness of the novel mid-infrared source exceeds that of the third-generation synchrotron source by a factor of 20. We also show that the nonlinear dynamics is strongly influenced by the choice of waveguide and laser parameters, thus offering an additional degree of freedom in tailoring the spectral profile of the generated light. Such an approach then opens new paths for high-brightness mid-infrared laser sources development for high-resolution spectroscopy and imaging. Furthermore, thanks to the excellent mechanical and thermal properties of the waveguide material, further power scaling seems feasible, allowing for the generation of watt-level ultra-broad frequency combs in the mid-infrared.
Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal-insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches ...based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal-insulator transition in VO
thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO
switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO
-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO
-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.
Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal-insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches ...based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal-insulator transition in VO
2
thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO
2
switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO
2
-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO
2
-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.
This paper presents the development of tunable filters using ohmic contact microelectromechanical system switches. It is shown that this type of switch is very well suited for the fabrication of ...low-loss high tuning-range microwave filters. Two sets of tunable Ku-band microstrip filters and resonators have been fabricated, with measured tuning ranges of 20% and 44%, and unloaded quality factors better than 75 in all cases. The 2-bit 5.7% fractional bandwidth, tunable bandpass filters exhibit insertion losses lower than 3.2 dB in all states.
The increase in frequency spectrum for wireless communication system has led to the growing interest in thin film electroacoustic technology that scales favorably upon miniaturization. ...Non-ferroelectric piezoelectric thin films such as Zinc Oxide is one of the most promising material for Complementary Metal Oxide Semiconductor-Microelectromechanical system (CMOS-MEMS) integration due to its silicon compatibility and good piezoelectric properties. This paper compares ZnO and Al doped ZnO (AZO) thin films performance characteristics when applied as CMOS-based surface acoustic wave (SAW) resonators. The interdigitated electrodes were fabricated using 0.35 μm CMOS technology followed by piezoelectric thin film deposition and probe pad patterning. Pure ZnO and AZO with 2 wt% Al
2
O
3
have been prepared by pulse laser deposition and RF magnetron sputtering respectively. Both deposited ZnO and AZO thin films exhibited preferential crystalline growth in 002 direction. EDS analysis confirmed the incorporation of aluminium in zinc oxide thin films. High frequency electrical measurement results revealed that the devices with AZO thin film have enhanced performances as compared to devices based on ZnO thin film. It is shown that the insertion loss for AZO thin film was reduced from −65.1 to −53.5 dB and the quality factor was enhanced from 11.33 to 25.81. More significantly, the electromechanical coupling coefficient and piezoelectric coefficient were enhanced from
κ
= 0.044–0.069% and
d
31
= 5.00 to 5.41 pm/V for AZO devices compared to those based on ZnO devices, respectively. One possible explanation of these enhanced piezoelectric properties comes from the almost ideal c-axis orientation of AZO thin film as compared to pure ZnO thin films. Our results suggest that the AZO thin film can be a better candidate for surface acoustic wave resonator using the CMOS-MEMS platform.
► We have grown TiO2 thin films by PLD on c-sapphire substrate with pre-patterned out-plane capacitor structures. ► Raman and XRD analyses indicate an evolution from “amorphous” to anatase and rutile ...phase. ► Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements. ► Permittivity measurements reveal high dielectric constant ɛr=120 of 600°C-grown TiO2 thin films.
Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30–120, showing the potentialities of the deposited material for capacitive switches applications.
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