Enhanced crystallinity, optical conductivity and terahertz cutoff frequency of stacked layers of FeSe2 by Al nanosheets

Herein, thin films of FeSe are coated onto glass and semitransparent Pb substrate of thicknesses of 200 nm. The produced glass/FeSe (GFS) and Pb/FeSe (PFS) are structurally, compositionally, and optically characterized. It is observed that Pb substrates induced the crystallinity of cubic FeSe and cubic PbSe. On average, 21% of the phases in FeSe films are identified as PbSe. Due to the strong orbital overlapping between Pb and FeSe, Pb substrate increases the light absorption, the dielectric constant, the optical conductivity, and the terahertz cutoff frequency by ≈150 %, 180 %, 263 %, and 101 %, respectively. In addition the direct and indirect energy bandgaps shrink from 2.49 and 2.80 to 2.41 and 2.50 eV, respectively. Moreover, treating GFS and PFS as terahertz optical resonators have shown that Pb substrates enhanced the drift mobility and increased the plasmon frequency making it adequate for 6G technology applications. An important feature of the PFS optical resonator is the stability of the terahertz cutoff frequency at 16 THz in the visible range of light. This feature together with the enhanced optical absorption in the visible light region makes the PFS films attractive for visible light communication technology.

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations

Pb/FeSe Interfaces Designed for Optical Communication Technology

Alharbi,

Qasrawi,

Algarni

2023

Formation, Enhanced Crystallization, Optical Absorption and Electrical Conduction in Copper Indium Selenide Thin Films Prepared via Pulse Laser Welding Technique

Khusayfan,

Khanfar,

Alharbi

2023

In this study, thin films of CuInSe2 (CIS) are expeditiously fabricated within 1 s utilizing the pulsed laser welding (PLW) technique. Preceding the PLW process, thin films of InSe (500 nm) are coated with Cu nanosheets of 60 and 120 nm thicknesses using vacuum coating systems. The optimal PLW parameters leading to the formation of CIS films include a pulse width of 1.0 ms, a spot diameter of 2.0 mm, and a repetition frequency of 10 Hz. The resulting CIS films exhibited a well‐crystalline cubic structure with lattice parameters of 5.265 Å. Surface morphology analyses revealed the preferential formation of porous films with varying stoichiometry, a characteristic that can be manipulated by adjusting laser welding parameters. The energy band gap and room temperature electrical conductivity display values of 1.80 eV and 2.06 × 10−5 (Ωcm)−1, respectively. Cu‐rich samples exhibit a wider energy band gap of 1.94 eV and lower electrical conductivity values of 4.78 × 10−7 (Ωcm)−1. The CIS film demonstrates n‐type conductivity attributed to the formation of donor levels centered at 0.24 and 0.10 eV. This study presents an ultrafast method for fabricating CIS films with physical properties compatible with those produced using traditional methods.

In Situ Monitoring of Crystallinity of FeSe₂ Thin Films During Thermal Annealing and the Annealing Effects on the Structural, Optical and Dielectric Properties

Gaabour,

Qasrawi,

Alharbi

2024

Herein stacked layers of iron selenide (FeSe2) thin films are deposited by the physical evaporation technique and thermally annealed. An in situ monitoring of the crystallinity during the annealing process has shown that the crystallinity is reached at 100 °C. The crystallinity of the films that preferred the orthorhombic phase is enhanced with increasing annealing temperature. Evidences about the improved crystallinity are presented by the increased crystallite and grain sizes, decreased microstrain values, decreased stacking faults, and decreased defect densities with increasing annealing temperature. Optical investigations have shown impressive effect of the annealing process on the optical reflectance, optical contrast, and light absorbability. Namely, respective improvement percentages exceeding 170%, 64%, and 140% is achieved near E≈2 eV for samples annealed at 200 °C for 20 min. Both direct and indirect optical transitions are dominant in the film. In addition the annealing increased the dielectric constant in the spectral range of 1.17–4.20 eV. Maximum dielectric enhancement by 214% is reached near ≈2.10 eV. Moreover, the annealing process increases the optical conductivity and drift mobility of the FeSe2 films. The improvement in the crystallinity that resulted in enhanced optical properties makes the thermally annealed FeSe2 films promising for optoelectronic technology applications.