Pyramidal pits

Jordan, M., Diaz, R. E., and Hirleman, E. D. (2002). Semi-empirical model of light scattering from submicron pyramidal pits. Opt. Eng. 41, 518-528. 

Use KOH solution to etch the part of the silicon wafer exposed through the square opening. The etch self-terminates at the Si(lll) planes, and a pyramidal pit is formed. 

FIGURE 8.10. (A) A schematic illustration showing the step-by-step formation of (lOO)-oriented 3D opaline lattice by templating against a 2D array of square pyramidal pits. (B, C) Two SEM images of square pyramidal templates with different spacing between pits. 

FIGURE 8.11. (A, B) SEM images of (100)-oriented colloidal crystals generated by templating 1.0-jxm polystyrene beads against a 2D array of 4-i.im wide square pyramidal pits. The crystals belong to die same sample that happened to stick to the bottom (A) and top (B) substrate when die top glass substrate was separated from the cell. 

Case II of Fig. 1 shows the cross-section of a pit formed by a preferential etch at a dislocation on a material whose planes form closed figures, such as the cubic system or the pyramidal planes of the hexagonal system. The relative etch rates are Rd > Ra > Ry F°r example, if the dislocation is normal to a 111 surface, triangular pyramidal pits will be formed. These pits have smooth, rather than terraced, sides as shown in Fig. 3. If, however, the dislocation line is at an angle to a ill surface, the triangular pyramidal pit is lopsided (Fig. 

Case in of Fig. 1 illustrates the cross-section of a pit formed in crystal systems, such as hexagonal, that have sets of planes that do not form closed figures. For hexagonal materials, Ryis the etch rate of the 0001 planes and R the rate of a set of prism planes. The relationship between the various etch rates is R(j > %J> Ry planes revealed depend to some extent on the etchant. Fig. 4 shows this type pit produced on a SiC by molten Na202 (17). The pyramidal pits are at the dislocations. Here the sides of the pits run in the... 

When the dislocation leaves the confines of the pit in either case n or in, the faster rate is no longer present and the pit will, on further etching, grow in a manner dictated by Ry, Rj, and Ra. For example, a triangular pyramidal pit formed at a dislocation normal to a 111 surface by an etchant... 

Fig. 4. Etch pits on o SiC. Pyramidal pits are associated with dislocations truncated pyramidal pits are not associated with dislocations. Etchant molten Na-O-.

Figure 6.7 Scanning electron microscopy image of part of a Klarite substrate showing some of the Au-coated inverted pyramidal pits. Reprinted from Ignat, T., Munoz, R., Irina, K. et al. (2009) Superlattices and Microstructures, 46, 451, with permission from Elsevier.

Pyramidal pits of 20 mn were formed at the surface of annealed Al. This technique allowed us to form an individual carbon nanotube (CNT) in PAA template. CNT deposition was performed by commonly used PECVD process. Also, we formed the arrays of vertically aligned CNT in PAA with cathodically deposited and evaporated metal catalyst. 

Figure 15.10 (a] SEM images of 1 j.m PS beads on the surface of a template containing an array of 4 pm wide pyramidal pits. Assembly was performed by evaporating the solvent slowly at room temperature. (b) Evolution of the packing S5nnmetry in 2D multiple layers of 1.1 pm PS particles as a function of the number of layers. ... 

A disposable plastic SERS sensor capable of achieving a 10 Raman response enhancement was fabricated by Oo et al. (2013) using roll-to-roll and nanoimprint techniques. The geometry used was based on the industry standard Klarite and was subsequently optimized for better performance. The original substrate consisted of an array of gold-coated inverted square pyramidal pits that were altered to form rectangular cones as well as varying their pitch an 8-fold improvement of sensitivity was achieved. 

---