Etch-pit method

Described below are the-three main methods of determining orientation back-reflection Laue, transmission Laue, and diffractometer. Nor should the old etch-pit method be overlooked. This is an optical method, involving the reflection of visible light from the flat sides, of known Miller indices, of etch pits in crystal surfaces. Although not universally applicable, this method is fast and requires only simple apparatus [G.25]. 

The etch pit method is usually best when dislocation densities are low (<10 mm ). If the dislocation densities are too high the etch pits overlap each other and it is very difficult to resolve their shape and count densities. 

Dislocations in a tilt boundary on the (011) plane in silicon lie 200 nm apart. What is the misorientation of the two grains. Would the etch-pit method be a good way to examine this boundary Explain your answer. 

Unlike the main minerals with the rock salt structure, fluorite cleaves on 111 planes and slips on 100 in the (0 11 direction [189]. Above 200 °C, slip on jl 10 (11 0) is also possible. Above 320 °C, polycrystalline plasticity is observed with the [10 0 planes providing three independent slip systems and the 110 planes giving two more [190]. Dislocations in fluorite have been studied by etch-pitting methods, and by TEM [191] but the latter is not without difficulty, since the mineral rapidly damages under electron and ion irradiation. A cubic symmetry void superlattice can be formed in TEM if the radiation flux is not restricted [192]. 

A very accurate measurement of Ccrjt would allow back-calculation of the surface energy for a given crystal. Because Ccrjt is dependent on the square of Y, such a measurement could be a very sensitive method of measuring interfacial energy at dislocation outcrops. The calculated interfacial energy from our experiments is 280+ 90 mJm- for the rhombohedral face of quartz at 300°C. Parks (10) estimated 25°C value of 360 + 30 mJm is well within the experimental error of our measurement. The best way to determine the value of Ccrjt would be to measure etch pit nucleation rate on... 

Ill) face quite slowly. The difference in etch rates is 300 1. The wafer is immersed in the etch and, by carefully controlling the etch time or using an etch stop method, a deep pit is generated. Depending on the thickness of the wafer and the size of the etch window, a thin membrane of single-crystal silicon can be formed at the bottom. 

In the 6H polytype, with the stacking sequence ABCACB, the (0001) carbon face and the (0001) silicon face etch differently because the SiC bond is slightly ionic. Many researchers use this fact to determine the difference between the two faces. Koga et al [9] used KOH to study three kinds of etch pits in 6H-SiC single crystal grown by the sublimation method. They observed that by increasing the pressure they could reduce one type of etch pit. 

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