Search

Temperature-dependent capacitance–voltage and conductance–voltage measurements of 200-nm-thick germanium telluride (GeTe) thin films deposited via direct current magnetron sputtering were investigated. Measurements were performed across a temperature range of 27–357 °C, with a sweep of voltage values from −20 to +20 V at an operating frequency of 1 MHz. An amorphous–crystalline transition temperature (Tc) of 197 °C was found. Below Tc, the GeTe films were highly resistive, and their capacitance was insensitive to the applied bias voltage and temperature. Above Tc, the capacitance showed strong dependence on temperature, owing to the triggering of GeTe crystallization incorporating nucleation and growth processes. Applied bias voltage did not show a profound impact on the GeTe capacitance even after crystallization, but it had an observable impact on the film conductance beyond 250 °C. Moreover, the GeTe thin film capacitance increased by a factor of 13 upon crystallization. Hall-effect measurements revealed that the film conductivity increased upon crystallization, as did the hole concentration and mobility. Cross-sectional transmission electron microscopy demonstrated that the GeTe thin films crystallize via a nucleation-dominated crystallization mechanism.

Engineering cobalt ferrites for application in health and biomedical science poses a challenge in terms of nanoscale morphology with a controlled size, shape, and thermochemical stability coupled with controlled properties for biocompatibility. Here, we report a simple one-step, low temperature approach to produce crystalline, nanosized cobalt ferrites (CFO) with a size ∼4.7 nm and demonstrate their applicability in breast cancer treatment. Inherent physiochemical and magnetic properties, which are quite important for biomedical applications, along with cytotoxicity of CFO nanoparticles (NPs) are investigated in detail. X-ray diffraction analyses confirm the cubic spinel phase with the tensile strain in crystalline CFO NPs. Chemical bonding analyses using infrared and Raman spectroscopic studies also support the cubic spinel phase. Electron microscopy and small-angle X-ray scattering revealed the narrow particle-size distribution and spherical-shape morphology. The as-synthesized CFO NPs exhibit superparamagnetic character. Unsaturated magnetization behavior suggests the existence of disordered spins in the surface layers. The temperature dependence of the magnetic parameters, namely, saturation magnetization, coercivity, retentivity, and squareness ratio, also supports the surface-localized spins. Cytotoxic activity of the as-synthesized CFO NPs against the human breast cancer (MCF-7) cell line and normal human peripheral blood mononuclear cells (PBMC) has been evaluated. The mild response of CFO NPs in terms of their antiproliferative nature against cancer cells and negligible Cytotoxicity reflecting their human-safe-and-friendly nature makes them suitable for bioapplications. Moreover, assessment of toxicity toward human red blood cells (RBC) revealed (<3%) hemolysis as compared to the positive control, suggesting potential applications of CFO NPs for human cells.

This study investigates the influence of molybdenum (Mo) doping on the local atomic structure, morphology, and electrical properties of amorphous germanium telluride (GeTe) thin films. Structural and morphological studies show that Mo-doping inhibits the crystallization of amorphous GeTe thin films. Moreover, the crystallization temperature of the GeTe thin film increases from 197 to 317 °C with increasing Mo dopant concentration. The electrical properties of Mo-doped GeTe thin films are discussed in terms of the capacitance–voltage characteristics in temperatures range 27–357 °C. The optical bandgap values decrease from 0.67 to 0.55 eV when increasing Mo doping in GeTe thin film. Mo integration significantly impacts the Ge–Te bond lengths and structural symmetry, increasing the degree of disorder in amorphous GeTe thin films. This study demonstrates the effectiveness of Mo doping in enhancing the thermal stability of the amorphous phase of GeTe for its envisioned memory and brain-inspired computing applications.