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research article

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

Muller, Andrei  
•
Khadar, Riyaz Abdul
•
Abel, Tobias
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April 16, 2020
ACS Applied Electronic Materials

This work investigates and reports on the radio-frequency (RF) behavior in the frequency range of 5 – 35 GHz of germanium-doped (Ge-doped VO2) vanadium dioxide 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 (Tc) 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 an 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 (ɛr) 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 (CPW) structures incorporating ultra-compact 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 reference. The reported results and analysis contribute to the advancement of the field of metal-insulator-transition material technology with high Tc for RF industrial applications.

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Type
research article
DOI
10.1021/acsaelm.0c00078
Author(s)
Muller, Andrei  
Khadar, Riyaz Abdul
Abel, Tobias
Negm, Nour
Rosca, Teodor  
Krammer, Anna  
Cavalieri, Matteo  
Schueler, Andreas  
Qaderi Rahaqi, Fatemeh  
Bolten, Jens
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Date Issued

2020-04-16

Published in
ACS Applied Electronic Materials
Volume

2

Issue

5

Start page

1263

End page

1272

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
NANOLAB  
FunderGrant Number

H2020

Phase Change Switch

Available on Infoscience
April 28, 2021
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/168277
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