Increased Power Handling of Vanadium Dioxide T/R Switches Using a Resonant Topology

Estes, N. J.; Chisum, Jonathan

doi:10.1109/mwsym.2019.8701088

Cited by 4 publications

(6 citation statements)

References 8 publications

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“…Furthermore, starting with a film with high conductivity values in dc, we may expect a larger dielectric constant. Knowing these exact values plays an important role in estimating correctly the resonance frequencies of filters, self-resonance frequencies of rf inductors, and OFF state switches performances − overall to adapt the designs to the thin-film properties and focus on the frequency bands where the losses or dielectric changes do not critically affect the overall circuit performances.…”

Section: Resultsmentioning

confidence: 99%

“…Subject of many controversies, it is currently agreed that the phase transition in VO 2 is probably a combined effect of lattice distortion and Coulomb correlations. Because of its ease of integration, reversible insulator to metal transition (IMT), fast switching time, and device-size shrinking capabilities, the employment of VO 2 as a reconfigurable radio-frequency (rf) material has been recently investigated for a variety of rf-reconfigurable devices on various substrates such as sapphire, − or cheaper SiO 2 − among others, in the frequency (f) range of 1–35 GHz. The relatively low transition temperature of VO 2 of T c = 68 °C when deposited on silicon (Si) CMOS compatible substrates hinders its usability for developing rf switches because for most rf applications, it is required to have a switching temperature above 80 °C .…”

Section: Introductionmentioning

confidence: 99%

“…In most cases, for the modeling of the off-state conductivity in rf VO 2 thin films used for switches, the authors usually consider the material as a constant valued sheet resistance while seldom simulating it as a lossy dielectric, as depicted in Table . The conductivity, σ dc_OFF values measured at room temperature are then assumed as representative for the whole range of rf performances (σ ac ( f ) = σ dc_OFF ), and VO 2 is modeled as sheet resistance or resistance. − On the other hand, for thin VO 2 films deposited on SiO 2 –Si CMOS compatible substrates, these films are simulated as a lossy dielectric, − the σ dc_OFF being considered as the conductivity value at the central frequency ( f 0 ) of the analyzed frequency band of the simulations (σ ac ( f 0 ) = σ dc_OFF ), whereas a fixed empirical value of 30 is used for the dielectric constant, of VO 2 at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

Müller

Khadar

Abel

et al. 2020

ACS Appl. Electron. Mater.

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This work investigates and reports on the radio-frequency (rf) behavior in the frequency range of 5–35 GHz of germanium-doped vanadium dioxide (Ge-doped VO2) thin films deposited on silicon substrates via sputtering and pulsed laser deposition (PLD) with estimated Ge concentrations of 5 and 5.5%. Both films exhibit critical transition temperatures (T c) of 76.2 and 72 °C, respectively, which are higher compared to that of the undoped VO2 which undergoes reversible insulator-to-metal phase transition at 68 °C. Both types of Ge-doped films show low hysteresis (<5 °C) in their conductivity versus temperature characteristics and preserve high off-state dc-conductivities (corresponding to the insulating state of the phase change material) of 13 S/m for the sputtered and 55 S/m for the PLD-deposited film, respectively. The dc on-state (corresponding to the conductive state of the phase change material) conductivity reaches 145,000 S/m in the case of the PLD film, which represents a significant increase compared to the state-of-the art values measured for undoped VO2 thin films deposited on identical substrates. In order to further understand the off-state dissimilarities and rf behavior of the deposited Ge-doped VO2 films, we propose an original methodology for the experimental extraction of the dielectric constant (εr) in the GHz range of the films below 60 °C. This is achieved by exploiting the frequency shift of resonant filters. For this purpose, we have fabricated coplanar waveguide structures incorporating ultracompact Peano space-filling curves, each resonating at a different frequency between 5 and 35 GHz on two types of substrates, one with the Ge-doped VO2 thin films and another one using only SiO2 to serve as the reference. The reported results and analysis contribute to the advancement of the field of metal–insulator–transition-material technology with high T c for rf industrial applications.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

Müller

Khadar

Abel

et al. 2020

ACS Appl. Electron. Mater.

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show abstract

“…VO 2 is a phase change material, which can behave as an insulator or a metal; it undergoes an abrupt change in conductivity from ∼10 S/m to 10 5 S/m within 4 to 6 ∘ C 24‐26 around the critical temperature of 68 ∘ C. For electrically switched VO 2 , this phase transition can occur within 100 nanoseconds 27 ; however, thermal switching times depend upon circuit geometry, RF power, 28 and DC bias and can range from 0.01–35 ms 22,29 . Given the compact size of the proposed VO 2 structure and the possibility for co‐planar heater placement <1 ms switching times may be possible.…”

Section: Introductionmentioning

confidence: 99%

“…In this letter, we demonstrate a class of highly configurable antennas based upon a VO 2 PCM which, if paired with a spatially addressable micro-heater array, 22,23 would be capable of quasi-continuous, high-speed, wideband antenna tuning and pattern/polarization reconfiguration. VO 2 is a phase change material, which can behave as an insulator or a metal; it undergoes an abrupt change in conductivity from 10 S/m to 10 5 S/m within 4 to 6 ∘ C [24][25][26] around the critical temperature of 68 ∘ C. For electrically switched VO 2 , this phase transition can occur within 100 nanoseconds 27 ; however, thermal switching times depend upon circuit geometry, RF power, 28 and DC bias and can range from 0.01-35 ms. 22,29 Given the compact size of the proposed VO 2 structure and the possibility for co-planar heater placement <1 ms switching times may be possible.…”

Section: Introductionmentioning

confidence: 99%

VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Connelly

Chisum

2020

Micro & Optical Tech Letters

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In this article, we demonstrate a reconfigurable antenna concept based upon a film of vanadium dioxide (VO2) with embedded metallic surface inclusions to increase radiation efficiency. We fabricate a monopole antenna with the proposed film, demonstrate a good match between measurement and simulation, and propose methods for increasing performance. We show that the addition of metallic inclusions in the VO2 film results in a 37‐fold increase in the radiation efficiency. This concept, if paired with a spatially addressable micro‐heater array, could enable extremely flexible and low‐loss frequency‐agile cognitive radio antennas for dynamic spectrum applications as well as polarization and pattern reconfiguration for operation in 5G and beyond systems where spectrum is congested and coexistence is compulsory.

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Modeling Phase Changing Property of VO₂ for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

2023

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Vanadium dioxide (VO2) is characterized using the time-resolved microwave conductivity (TRMC) method for applications requiring reconfigurable microwave frequency selection. We demonstrate that TRMC is a flexible method for determining the microwave conductivity of thin film compounds of varied thicknesses that are both phase-changing and non-phase changing in nature. The method makes use of Ka-band microwave resonant waveguides to examine how thermally excited samples' microwave conductivity changes in response to microwave-transmitted power through the system's sensitivity factor. The sensitivity factor is illustrated by a study of incident waves (electromagnetic fields) on medium and waveguide perturbation analysis in VO2 thin films. The TRMC measurements show a low regime in the microwave conductivity below the transition temperature (Tc) of VO2 where Tc occurs near 65°C; this is associated with the dielectric characteristics of the charge carriers and points to the presence of shallow trap electron states. Longer electron hops enhance charge mobility and, consequently, the barrier energy above Tc, where these states are thermally discharged, resulting in a high thermally triggered microwave conductivity regime. The activation energy may come from a variety of complex contributions, like polaronic self-localizations, as well as a dynamic disorder brought on by the thermal oscillations of VO2 molecules. The calculated conductance values are simulated in CST Studio as plane wave incidence on medium to ascertain the fields' microwave transmission behavior and contrast it with the experimental results to validate the model. Additionally, using the derived conductivities, the characteristics of well-known materials like copper (Cu) were confirmed.

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Increased Power Handling of Vanadium Dioxide T/R Switches Using a Resonant Topology

Cited by 4 publications

References 8 publications

Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Modeling Phase Changing Property of VO₂ for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

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Increased Power Handling of Vanadium Dioxide T/R Switches Using a Resonant Topology

Cited by 4 publications

References 8 publications

Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

Radio-Frequency Characteristics of Ge-Doped Vanadium Dioxide Thin Films with Increased Transition Temperature

VO2 antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Modeling Phase Changing Property of VO2 for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

Contact Info

Product

Resources

About

VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Modeling Phase Changing Property of VO₂ for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity