Composition Analysis by STEM-EDX of Ternary Semiconductors by Internal References

A practical method to determine the composition within ternary heterostructured semiconductor compounds using energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy is presented. The method requires minimal external input factors such as user-determined or calculated sensitivity factors by incorporating a known compositional relationship, here a fixed stoichiometric ratio in III–V compound semiconductors. The method is demonstrated for three different systems; AlGaAs/GaAs, GaAsSb/GaAs, and InGaN/GaN with three different specimen geometries and compared to conventional quantification approaches. The method incorporates absorption effects influencing the composition analysis without the need to know the thickness of the specimen. Large variations in absorption conditions and assumptions regarding the reference area limit the accuracy of the developed method.

Theoretical investigation of ternary semiconductors half-Heusler RhTaZ (Z = Si, Ge and Sn) for thermoelectric applications

The structural, electronic, elastic, thermodynamic and thermoelectric properties of RhTaZ (Z = Si, Ge and Sn) half-Heusler materials have been studied using density functional theory. We have found that the compounds studied can be experimentally synthesized. Also, RhTaZ (Z = Si, Ge and Sn) alloys exhibit a semiconductor behavior following the Slater–Pauling rule. The elastic properties calculated confirm that our compounds are mechanically stable. Using Debye’s quasi-harmonic model, the thermodynamic properties of these half-Heusler alloys were investigated. For the study of thermoelectric properties, the semi-classical Boltzmann theory, as implemented in the BoltzTraP code, has been used. The high values obtained from the figure of merit for RhTaZ (Z = Si, Ge and Sn) compounds suggest that they are promising candidates for thermoelectric applications at low and high temperatures.

Update on Interfacial Charge Transfer (IFTC) Processes on Films Inactivating Viruses/Bacteria under Visible Light: Mechanistic Considerations and Critical Issues

This review presents an update describing binary and ternary semiconductors involving interfacial charge transfer (IFCT) in composites made up by TiO2, CuO, Ag2O and Fe2O3 used in microbial disinfection (bacteria and viruses). The disinfection mechanism, kinetics and generation of reactive oxygen species (ROS) in solution under solar/visible light are discussed. The surface properties of the photocatalysts and their active catalytic sites are described in detail. Pathogenic biofilm inactivation by photocatalytic thin films is addressed since biofilms are the most dangerous agents of spreading pathogens into the environment.

Domain formation and phase transitions in the wurtzite-based heterovalent ternaries: a Landau theory analysis

Characterizing the crystalline disorder properties of heterovalent ternary semiconductors continues to challenge solid-state theory. Here, a Landau theory is developed for the wurtzite-based ternary semiconductor ZnSnN2. It is shown that the symmetry properties of two nearly co-stable phases, with space groups Pmc21 and Pbn21, imply that a reconstructive phase transition is the source of crystal structure disorder via a mixture of phase domains. The site exchange defect, which consists of two adjacent antisite defects, is identified as the nucleation mechanism of the transition. A Landau potential based on the space-group symmetries of the Pmc21 and Pbn21 phases is constructed from the online databases in the ISOTROPY software suite and this potential is consistent with a system that undergoes a paraelectric to antiferroelectric phase transition. It is hypothesized that the low-temperature Pbn21 phase is antiferroelectric within the c-axis basal plane. The dipole arrangements within the Pbn21 basal plane yield a nonpolar spontaneous polarization and the electrical susceptibility derived from the Landau potential exhibits a singularity at the Néel temperature characteristic of antiferroelectric behavior. These results inform the study of disorder in the broad class of heterovalent ternary semiconductors, including those based on the zincblende structure, and open the door to the application of the ternaries in new technology spaces.

Using resonant energy X-ray diffraction to extract chemical order parameters in ternary semiconductors

Resonant energy X-ray diffraction was used to quantify cation site ordering in ZnGeP2 thin films.