Enhanced magneto-optical rotation of probe field in thermal medium via spontaneous generated coherence.

A four-level double lambda closed atomic configuration is considered to study the polarization plane rotation of the probe beam through cold as well as thermal Rb[Formula: see text] atomic medium by varying the spontaneously generated coherence (SGC). Magnetic field and strong coupling field are applied to the atomic configuration. The light-matter interaction leads to enhanced the magneto-optical rotation. The intensity of the applied fields plays promising role in the generation and enhancement of birefringence. It ultimately enhances the polarization plane rotation of the probe beam in the Doppler medium. In the presence of both SGC and Doppler broadening effects, the optical rotation and transmission of the weak light beam are modified and controlled as well, which have potential applications in magnetometery and laser frequency stabilization.

Defect-mediated photoluminescence enhancement in ZnO/ITO via MeV Cu++ ion irradiation.

Zinc oxide (ZnO) nanowires play a pivotal role in the nanoworld due to their broad range of characteristics and applications. In this work, structural and optical properties of ZnO nanowires grown on indium doped tin oxide (ITO) coated glass have been modified by copper (Cu++) ions irradiation at constant energy of 0.7 MeV. The X-ray diffraction (XRD), photoluminescence (PL), and field emission scanning electron microscope (FESEM) are used to examine changes in the nanowires. XRD results show that the crystallite size first decreases and then increases with high ion dose while peaks' intensity decreases continuously with increasing the dose. The absence of (102) plane after irradiation depicts the defects formation. FESEM clearly shows the damage that occurred in the density of nanowires and also depicts the reduced charging effect with increasing dose. The PL spectra indicate the strong near-band edge peak and green luminescence enhancement has been recorded due to low dose ion irradiation.

Synthesis of enriched boron nitride nanocrystals: A potential element for biomedical applications.

The shortcomings in Boron neutron capture therapy (BNCT) and Hyperthermia for killing the tumor cell desired for the synthesis of a new kind of material suitable to be first used in BNCT and later on enable the conditions for Hyperthermia to destroy the tumor cell. The desire led to the synthesis of large band gap semiconductor nano-size Boron-10 enriched crystals of hexagonal boron nitride (10BNNCs). The contents of 10BNNCs are analyzed with the help of x-ray photoelectron spectroscopy (XPS) and counter checked with Raman and XRD. The 10B-contents in 10BNNCs produce 7Li and 4He nuclei. A Part of the 7Li and 4He particles released in the cell is allowed to kill the tumor (via BNCT) whereas the rest produce electron-hole pairs in the semiconductor layer of 10BNNCs suggested to work in Hyperthermia with an externally applied field.

Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite.

In this work, we have studied new double perovskite materials, A2 1+B2+B3+X6 1-, where A2 1+ = Cs, B2+ = Li, Na, B3+ = Al, Ga, In, and X6 1-. We used the all electron full-potential linearized augmented plane wave (FP-LAPW+lo) method within the framework of density functional theory. We used the mBJ approximation and WC-GGA as exchange-correlation functionals. We optimized the lattice constants with WC-GGA. Band structures were calculated with and without spin-orbit coupling (SOC). Further, band structures for Cs2LiGaBr6 and Cs2NaGaBr6 were calculated with SOC + mBJ to correct the band gap values with respect to experimental value. We obtained direct bandgaps at Γ-point of 1.966 eV for Cs2LiGaBr6 and 1.762 eV for Cs2NaGaBr6, which are similar to the parent organic-inorganic perovskite (MAPI) CH3NH3PbI3 (E g = 1.6 eV). Total and partial density of states were analyzed to understand the orbital contribution of Cs, Na, Li, Ga and Br near the Fermi level. The optical properties in terms of real and imaginary ε, refractive index n, extinction coefficient k, optical conduction σ, absorption I, and reflectivity R were calculated. A study of the elastic and mechanical properties shows that both materials are thermodynamically stable. A stable, direct bandgap and a gap value close to those of MAPI make Cs2NaGaBr6 a great competitor in the Pb-free hybrid perovskite solar cells world.

Correction: Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite.

[This corrects the article DOI: 10.1039/D0RA01764G.].

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes.

The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2-3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells.