Ultrahigh Infrared Photoresponse in Titanium Sesquioxide at Mott‐Insulator Transition

Abstract

tage in collection ability of photocarriers over a wide range from ultraviolet to terahertz wavelengths. Hence, the photoresponsivity for graphene has been limited between 10 −6 and 10 7 A W −1. [13-17] Only TMDs (transition metal dichalcogenides) based photo detectors, e.g., MoS 2 , MoSe 2 , WS 2 , and WSe 2 and VII-TMDs, e.g., ReS 2 and ReSe 2 were reported to exhibit photoresponsivity between 10 4 and 10 7 A W −1 for the radiation wavelength in a limited spectrum range. [18-20] The ability to detect IR in vdW interfaces was further explored by combining ReS 2 and ReSe 2 to achieve a maximum responsivity of 3.64 × 10 5 A W −1 at λ = 980 nm. [21] Overall, vdW photodetectors reported so far pose a difficulty in achieving both the high photoresponsivity and wide range detection together mainly for the IR radiation. Moreover, although IR detection was obtained using several narrow bandgap vdW materials but the photodetectors showed drawbacks such as, slow response speed and environmental instability along with low photoresponsivity (e.g., black phosphorous based heterostructures). [22] Recently, Li et al. reported multifunctional properties in the thin film of titanium sesquioxide (Ti 2 O 3), showing both ferromagnetic and even superconducting nature in their two separate studies. [23,24] Moreover, Ti 2 O 3 has also demonstrated a wide range of IR detection capability (due to a bandgap of ≈0.09-0.1 eV) in conjunction with the graphene due to its surface and interface properties. [25] The conductivity at the interface could possibly be due to the Fermi level pinning in the conduction band, which is unusual with narrow bandgap materials. [25] Pearson in 1958 reported an interesting conductivity transition in Ti 2 O 3 under heating conditions [26] and followed by many other reports. Further, in 1981 Mott indicated occurrence of interesting metal−insulator transition in Ti 2 O 3 at 400 K. [27] So far there are no reports on exploiting IR detection capability of Ti 2 O 3 at its transition temperature. Our study provides an exceptional phototransition in granular Ti 2 O 3 upon IR illumination during its transitional state. We report an abrupt enormously large increase in the photoresponsivity for the IR radiation that further provides a deep insight into the transition phenomena in Ti 2 O 3 at 400 K.

Anomalous electrochemical capacitance in Mott-insulator titanium sesquioxide

“…1(m)) was also observed that could be originated from the distorted Ti 2 O 3 structure. 5,8 Similar to the Ti peak shifts, there are no observable peak shift noted with O at different annealing temperatures, e.g. the lattice peak of O at 529.7 eV at RT (Fig.…”

“…1(m)) owing to its origin from Ti–O bonds in the lattice of Ti 2 O 3 . 4,8 In addition, a secondary peak (non-lattice) at 531.5 eV (Fig. 1(m)) was also observed that could be originated from the distorted Ti 2 O 3 structure.…”

“…1(a) and S2 †). 3,8,9 The remaining peaks indicated by * are identied as other thermally stable TiO x phases and do not reveal any variations due to annealing at any temperature. 10 Moreover, in agreement with the previous studies, 5 no additional peaks are observed in Ti 2 O 3 aer annealing at 200 C and 300 C (Fig.…”

“…1(a) and S2†). 3,8,9 The remaining peaks indicated by * are identified as other thermally stable TiO x phases and do not reveal any variations due to annealing at any temperature. 10 The lattice parameters a , b and c of a trigonal cell in the R 3̄ c corundum crystal of Ti 2 O 3 deduced from the XRD analysis at RT are a = b = 5.146 Å and c = 13.636 Å.…”

Photothermal conversion of Ti2O3 film for tuning terahertz waves

“…graphene/Ti 2 O 3 interface (Yu et al, 2018). In addition, Ti 2 O 3 has attracted considerable attention because it exhibits intriguing metal-insulator transition (MIT) in the temperature range of 300-450K, which is accompanied by significant changes in optical, electric, and magnetic properties (Honig and Reed, 1968;Nandi et al, 2020). During the transition, the changes in optical, electric and magnetic properties can be attributed to the lattice parameter alteration (Yan et al, 2012).…”