A review of bipolar magnetic semiconductors from theoretical aspects

Spintronics, which employs electrons' spin degree of freedom in data storage and transmission, acts as a promising candidate for next-generation information technology owing to its improved processing speed and reduced power consumption. To seek and design materials with highly spin polarized carriers and find an efficient way to control the spin polarization direction of carriers are critical and urgent to spintronics applications. In this aspect, the bipolar magnetic semiconductor (BMS) serves as an ideal solution since it can generate currents with 100% spin polarization, and the direction of spin polarization is easily tunable by an external gate voltage. Up to now, there have been lots of BMSs predicted by first-principles calculations, however, most of them are extrinsically induced by chemical or physical modifications, and a generalized scheme for designing BMS materials is still lacking. This paper is aimed to briefly review the existing BMS materials designed by theoretical simulations, analyze the main obstacles to experimental realization, and put forward suggestions for future development.

The stability, structural, electronic, and optical properties of hydrogenated silicene under hydrostatic pressures: a first-principle study

The structural, electronic, and optical properties of hydrogenated silicene have been studied under different hydrostatic pressures using first-principle calculations. The binding energy and band structure have been calculated for chair (C-) and boat (B-) structures, which are having good stability at 0 GPa, 3 GPa, 6 GPa, 9 GPa, 12 GPa, 15 GPa, and 18 GPa hydrostatic pressures. Stability has been verified using binding energy and phonon calculations. The C- and B-structures have become metallic and unstable at 21 GPa. The optical properties of B-configuration have been studied in the energy range of 0-20 eV. Five optical parameters such as conductivity threshold (σ_th), dielectric constant ε(0), refractive index n(0), birefringence Δn(0), and plasmon energy (ħω_p) have been calculated for the first time under different hydrostatic pressures. The calculated values are in good agreement with the reported values at 0 GPa.

Rise of silicene and its applications in gas sensing

Reviewing a subject is done to provide an insight into theoretical and conceptual background of the study. Looking back into the history of an emerging field and summarizing it in a few pages is a herculean task. Anyway, it was imperative to write a few words about the rise of silicene, its properties, and its applications as gas sensors. Currently, silicene is a growing field of interest. It is probably one of the most studied materials nowadays and scientists and researchers are studying it because of its intriguing electronic properties and potential applications in nanoelectronics. Various experimental and theoretical investigations are going on worldwide to explore the various aspects of this field. It is essential to review the literature based on investigations by various scientists in this field.

Individual Gas Molecules Detection Using Zinc Oxide–Graphene Hybrid Nanosensor: A DFT Study

Surface modification is a reliable method to enhance the sensing properties of pristine graphene by increasing active sites on its surface. Herein, we investigate the interactions of the gas molecules such as NH3, NO, NO2, H2O, and H2S with a zinc oxide (ZnO)–graphene hybrid nanostructure. Using first-principles density functional theory (DFT), the effects of gas adsorption on the electronic and transport properties of the sensor are examined. The computations show that the sensitivity of the pristine graphene to the above gas molecules is considerably improved after hybridization with zinc oxide. The sensor shows low sensitivity to the NH3 and H2O because of the hydrogen-bonding interactions between the gas molecules and the sensor. Owing to observable alterations in the conductance, large charge transfer, and high adsorption energy; the sensor possesses extraordinary potential for NO and NO2 detection. Interestingly, the H2S gas is totally dissociated through the adsorption process, and a large number of electrons are transferred from the molecule to the sensor, resulting in a substantial change in the conductance of the sensor. As a result, the ZnO–graphene nanosensor might be an auspicious catalyst for H2S dissociation. Our findings open new doors for environment and energy research applications at the nanoscale.

Edge functionalized germanene nanoribbons: impact on electronic and magnetic properties

The spin-polarized calculations of fluorinated a₁₁doped with a B atom indicate that it is semiconducting in both channels with band gaps of 0.4254 and 0.3932 eV for spin-up (α) and spin-down (β) channels.

A theoretical study of gas adsorption on silicene nanoribbons and its application in a highly sensitive molecule sensor

Silicene nanoribbon is a promising material to detect individual gas molecules with high sensitivity.