Anharmonicity and impurities have a significant impact on the dynamic and optical properties of crystalline solids. In this report, we have performed temperature-dependent Raman spectroscopy in the range of 300–800 K for hydrothermally synthesized titanium dioxide (TiO2) nanorod composed microflowers doped with Cu. X-ray diffraction and high resolution transmission electron microscopy confirm the pure rutile phase of both pristine and Cu doped TiO2. The most intense Eg and A1g modes exhibit a frequency redshift, and the linewidth increases with temperature, which leads to Fano line shape type asymmetry. The anharmonicity induced phonon frequency shift as a function of temperature was well fitted using the Klemens model by combining three and four-phonon coupling processes. The Raman modes soften with the increasing concentration of Cu doping. The Cu dopant acts as an impurity, which manifests defect states to tune the bandgap and shorten the phonon lifetime and anharmonicity. Such an anharmonic effect can lead to applications in the sensing devices with suitable thermal and electrical conductivities.

Manipulating light at the sub-wavelength level is a crucial feature of surface plasmon resonance (SPR) properties for a wide range of nanostructures. Noble metals like Au and Ag are most commonly used as SPR materials. Significant attention is being devoted to identify and develop non-noble metal plasmonic materials, whose optical properties can be reconfigured for plasmonic response by structural phase changes. Chromium(Cr) which supports plasmon resonance, is a transition metal with shiny finished, highly non-corrosive, and bio-compatible alloys, making it an alternative plasmonic material. We have synthesized Cr micro-rods from a bi-layer of Cr/Au thin films, which evolves from Face Centered Cubic (FCC) to Hexagonal Close Packed (HCP) phase by thermal activation in a forming gas ambient. We employed optical absorption spectroscopy and cathodoluminescence (CL) imaging spectroscopy to observe the plasmonic modes from the Cr micro-rod. The origin of three emission bands that spread over UV-Vis-IR wavelength is established theoretically by considering the critical points of the second-order derivative of the macroscopic dielectric function obtained from density functional theory (DFT) matches with interband/intraband transition of electrons observed in density of states vs. energy graph. The experimentally observed CL emission peaks closely match the s-d and d-d band transition obtained from DFT calculations. Our findings on plasmonic modes in Cr(HCP) phase can expand the range of plasmonic material beyond noble metal with tunable plasmonic emissions for plasmonic-based optical technology.

The thin films of Ni and Bi are known to form NiBi3 and NiBi compounds spontaneously at the interface, which become superconducting below 4.2 K and show ferromagnetism either intrinsically...

Layered transition-metal dichalcogenides (TMDs) are gaining significant attention because they exhibit unconventional magnetic properties due to crystal imperfections in their usually nonmagnetic 2D structure and are pertinent for the development of spintronic devices. This work aims to investigate the magnetic response of self-engineered Se-deficient TiSe2 thin films, synthesized using chemical vapor deposition. We demonstrate the tunability of the ferromagnetic order with the introduction of Au atoms using low-energy Au-ion implantation, which works as a controlling knob to vary the stoichiometry of Se in TiSe2–x . The corresponding isothermal field–magnetization curves fit well with a modified Brillouin J function with J values of 1.5 for Ti3+ and 4 for Au3+, accounting for the diamagnetism that arises from Au implantation. We propose a qualitative model for the experimentally observed magnetization as a function of the ion fluence, corroborated with high-resolution transmission electron microscopy. Depending on the Au nanoparticle size in the implanted samples, magnetization saturates faster at a much lower applied magnetic field than that with the pristine sample. Our findings hold the potential to expand the range of 2D ferromagnetic materials for spintronic and magnetic-sensing device applications.