China
Africa
Explore chapters and articles related to this topic
Nanosensor Laboratory
Published in Vinod Kumar Khanna, Nanosensors, 2021
What factors determine the suitability of an etching technique for a particular application? Appropriateness of a particular technique for a specific application is governed by several factors. Techno-economic aspects, such as the extent of control over etching profile vis-à-vis equipment cost, installation, maintenance, and infrastructural expenses are prime considerations. Anisotropic wet etching of <100> -oriented silicon is an established technique that has been widely used for realization of microstructures. For defining the crystal orientation, the Miller indices of a plane of atoms in the crystal lattice are determined. The Miller indices comprise a set of three numbers obtained by finding the intercepts of the plane with the crystallographic axis and expressing them in terms of unit cell dimensions. Then reciprocals of intercepts are taken and fractions are cleared to write the Miller indices <hkl>, e.g. the Miller indices of a plane parallel to two axes but intersecting the third axis at a distance equal to one edge of unit cell are <100>, <010> and <001> depending on the axis cut.
The Structure of Solids
Published in Joseph Datsko, Materials Selection for Design and Manufacturing, 2020
The Miller indices are used to designate specific crystallographic planes within a space lattice. They specify the orientation of the planes with respect to the axes of the unit cell. They do not fix the position in terms of distance from the origin: thus parallel planes have the same designation. The Miller indices are determined from the three intercepts that the plane makes with the three axes of the crystal. Actually, it is the reciprocal of the distance between the intercepts with the axis and the origin measured in terms of multiples of fractions of the unit cell lengths a, b, and c that is used in the determination. The final step in calculating the Miller indices is to reduce the three reciprocals to the lowest integers having the same ratio. The indices are expressed in parentheses. As is true with the direction indices, the sequence of the integers relates to the distances along the x, y and ζ axis, respectively. The following examples make this procedure clear.
Crystalline Structure of Metals
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
The specification of directions and planes within crystalline solids is of great technological importance to a metallurgist since some materials’ properties strongly depend on their crystallographic orientations. Miller indices are used as the notation system for defining planes and directions in crystal lattices. In order to define a crystallographic plane, three integers l, m, and n, known as Miller indices, are used. The three integers are written as (hkl) for the crystallographic plane whereas the crystallographic directions are represented by [hkl]. By convention, a negative integer is represented by a bar (e.g. negative h = h¯).
Fabrication of GaAs micro-optical components using wet etching assisted femtosecond laser ablation
Published in Journal of Modern Optics, 2020
Xiaoyan Sun, Fang Zhou, Xinran Dong, Fan Zhang, Chang Liang, Lian Duan, Youwang Hu, Ji’an Duan
XRD and EDX measurements were carried out to further investigate the mechanism of femtosecond laser ablation on the GaAs corrosion rate. The detection was divided into three types of samples, ‘Not irradiated’, ‘Irradiated’, and ‘Corroded’. Figure 8(a) shows that after laser irradiation, a new diffraction peak appeared at 59.02°. This indicates that gallium trioxide (Ga2O3) was produced after laser irradiation. Figure 8(b) shows that 4.11% oxygen appeared on the GaAs sample after laser irradiation. This is because when GaAs is in the air and is irradiated by a laser, it is oxidized with oxygen, and oxides such as Ga2O3 form. The oxide is more soluble in the corrosion solution, and therefore, the GaAs corrosion rate increased after laser irradiation. In addition, after corrosion a new diffraction peak appeared at 53.75°, and this is a because of the presence of the crystal direction (311) of GaAs in the sample. The GaAs crystal is anisotropic; the corrosion rates of different crystal directions are different, and this is one of the reasons for the changes in corrosion rate. The diffraction peaks near 66° show that the diffraction peak of the ‘Irradiated’ sample shifted to the left of the diffraction peak of the ‘Not irradiated’ sample; also, the spacing index d increased. The crystal of GaAs is a sphalerite structure, and the relationship between the lattice constant a and index spacing d is as follows: where h, k, and l are the Miller indices.