Electron irradiation induced vitrification at dislocations in quartz
Recent observations using the ‘weak beam’ electron microscopy technique of split images of dislocations in quartz have been interpreted as arising either from dissociation of the dislocations into partials1, or from a glassy (metamict) phase at the core2, resulting from irradiation damage. In this letter we describe observations of lattice images of near end-on dislocations in quartz, which enable us to distinguish between these two models.
Transmission electron microscopy of lattice planes in human alveolar bone apatite crystals
SummaryPeriodic fringes corresponding to six different lattice planes have been observed in apatite crystals of human normal alveolar bone by transmission electron microscopy. Three of these sets of fringes have spacings less than 3.5 Å corresponding to the Scherzer resolution of the microscope used. The (0002) lattice plane of hydroxyapatite of 3.4 Å d-spacings, the
$$\left( {21\bar 11} \right)$$
 lattice plane with a d-spacing of 2.81 Å, and the
$$\left( {30\bar 30} \right)$$
 lattice plane with a d-spacing of 2.72 Å have been identified. The (0002) and
$$\left( {21\bar 21} \right)$$
 lattice planes have been observed for the first time in bone microcrystals. Some of the crystals studied were characterized by a mean width/thickness ratio of 6.91, typical of platelike habit, whereas observations of crystals aligned along the
$$\left\langle {1\bar 210} \right\rangle $$
 and
$$\left\langle {1\bar 211} \right\rangle $$
 directions showed a needlelike habit. The mean length of the bone apatite crystals was 470 Å. A dark line similar to the one observed in enamel and dentine crystals was also seen. The bone microcrystals observed have shown a high sensitivity to beam damage.
Selective etching of InP in NaF solution
Abstract The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [ 0 1 ¯ 1 ], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1]B and [ 1 1 ¯ 1 ¯ ]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.