Tunable RF Phase Shifters Based on Vanadium Dioxide Metal Insulator Transition

Phys. Chem. Chem. Phys.

et al. 2020

Section: Imentioning

confidence: 99%

Modelling the enthalpy change and transition temperature dependence of the metal–insulator transition in pure and doped vanadium dioxide

Clark

Phys. Chem. Chem. Phys.

et al. 2020

“…Pure vanadium dioxide (VO 2 ) has two phases; below 340 K it has the monoclinic or M 1 phase with a band gap, whereas above 340 K it has the metallic rutile form, called the R phase [1][2][3]. The phase transition is fully reversible so that it is a promising material for various applications [4] such as smart windows [5], optical [6] or rf switches [7,8], and as a component of steep slope transistors [9][10][11]. Although the structural change at 340 K has been heavily studied, the electronic structures and especially the magnetic ground states of both R and M 1 phases are still debated [1,3,12].…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of metallic and insulating phases of vanadium dioxide and its oxide alloys

Robertson

2019

Phys. Rev. Materials

VO 2 attracts much attention due to its metal-insulator transition. Alloying VO 2 with MgO and GeO 2 allows the band gap and the transition temperature to be varied. We find that the spin order plays a key role in creating the band gap in the low-temperature M 1 phase. For MgO alloying, the alloying fraction n (Mg n V 1−n O 2−n) is varied from 12.5 to 33.3%. The minimum band gap does not change without a structural rearrangement because both band edges of insulating VO 2 consist of only V 3d states on sixfold-coordinated V sites. A crystal search finds that if the Mg fraction in the alloy is large enough (>20%), fivefold-coordinated V sites can have lower energy than the sixfold sites, and the band gaps are doubled. For GeO 2 alloying, the insulating M 1 structure reverts to rutile because GeO 2 has a rutile phase. The result matches the experimental observation and is very important in guiding VO 2 's applications such as smart coating and nonlinear resistor.

“…Vanadium dioxide (VO 2 ) undergoes a metal-insulator transition (MIT) from insulating monoclinic (M1) phase at lower temperatures to a metallic rutile phase above ~340 K [1][2][3]. This makes VO 2 useful as a thermochromic material in smart windows [4], RF switches [5], and steep slope transistors [6]. The latter application uses a field effect transistor (FET) device [7][8][9], with a gate oxide, but features different mechanisms than metal-oxide-semiconductor FET [10,11].…”

Section: Introductionmentioning

confidence: 99%

Band alignment calculation of dielectric films on VO2

Zhang

Chen

Microelectronic Engineering

et al. 2019

The chemical bonding and band edge line-up of several gate insulators on monoclinic (M1) phase VO 2 are studied based on hybrid density functional calculations. High dielectric constant HfO 2 and ZrO 2 , wide band gap oxide Al 2 O 3 , and narrower band gap TiO 2 are considered. The insulating interface supercells with a clean bandgap are built and adapted to analysis the band alignment. All the gate insulators show the type-I band alignment with VO 2. The valence band offset are all larger than 1 eV. The calculated conduction band offsets for HfO 2 , ZrO 2 and Al 2 O 3 are all larger than 2 eV. In terms of the band alignment, these three insulators can work as suitable gate dielectrics for VO 2-based device application, but more accurate line-up analysis on TiO 2 /VO 2 interface is still needed.