Low-energy electron diffraction from heated porous silicon surfaces

We have found that low-energy electron diffraction patterns can be obtained from porous silicon samples made with various silicon orientations, resistivities and anodisation treatments, after specimens have been heated in an ultra-high vacuum to around 850°C for (100) samples and 950°C for (111) samples. The results show that at least some of the surfaces of porous silicon are, in all cases studied, parallel to the original surface before anodising. The (100) surfaces show a clean surface 2×1 reconstruction, but fractional order spots appear only as streaks in the (111) surface patterns. For significant portions of samples, the underlying silicon crystal lattice is continuous to the very top of the porous region.