0000000000335712
AUTHOR
J. Pellicer-porres
Observation of the Cinnabar Phase in ZnSe at High Pressure
In this paper we describe the results of an energy dispersive X-ray diffraction experiment carried out in the ZnSe 1 m x Te x alloy and pure ZnSe under high pressure. In the downstroke the cinnabar phase is observed between the rocksalt and the zincblende phases. The analysis of the whole series of compositions ( x =0, 0.05, 0.1 and 0.2) enables us to establish its lattice parameters in ZnSe ( a =3.785 + and c =8.844 + at 10.5 GPa). The X-ray diffraction pattern simulation suggests that the internal parameters u and v are close to 0.5, indicating that the cinnabar phase in ZnSe is similar to that observed in GaAs and ZnTe. The cinnabar's stability range decreases as the Te content is reduce…
Structural Metastability and Quantum Confinement in Zn1–xCoxO Nanoparticles
This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nanoparticles (NPs) by means of optical measurements under pressure (up to 25 GPa), X-ray absorption, and transmission electron microscopy. W-NPs were chemically synthesized at ambient conditions and RS-NPs were obtained by pressure-induced transformation of W-NPs. In contrast to the abrupt phase transition in W-Zn1-xCoxO as thin film or single crystal, occurring sharply at about 9 GPa, spectroscopic signatures of tetrahedral Co(2+) are observed in NPs from ambient pressure to about 17 GPa. Above this pressure, several changes in the absorption spectrum reveal a gradual and irreversible W-to-RS pha…
Experimental demonstration of the physics of resonant cavities
We describe an undergraduate experiment that demonstrates the physics of cavity resonators. A mobile wall lets students alter the position of the nodes, thus changing the mode pattern. The nodal structure is made apparent by placing a metallic plate at different positions inside the cavity. A technique for dielectric characterization also is introduced, which helps students understand the boundary conditions in dielectrics, as well as highlighting the characteristics of fields in cavities.