TABLE OF CONTENTS A.G. Cullis
September 1997
Since the discovery [1] of intense visible photoluminescence (PL) given by anodised porous Si, an extremely large amount of analytical work has been carried out on the material world-wide. This has been driven to a substantial extent by the potential for the fabrication of light-emitting optoelectronic devices, although there is also a deep fundamental interest in the mechanism of light emission. Many of the factors [2 7] which have influenced this progress are considered in this book. The present Datareview focuses on the underlying structure of the porous material and considers the way in which this critically determines the luminescence behaviour.
The structural characteristics of porous Si have been studied by a range of techniques. Direct imaging of the material can be carried out by scanning electron microscopy [8] (SEM), although the resolution achievable (down to <2 nm) and the available contrast make it difficult to visualise the smallest structures. The latter are generally imaged by transmission electron microscopy (TEM), which permits studies with resolution down to atomic dimensions [9]. However, samples for assessment must be thinned to electron transparency and it is vital that the technique employed (usually ion milling or direct cleavage) introduces as little atomic-scale damage and disorder as possible. Indeed, rapid transfer of freshly-prepared samples to the vacuum of the microscope is essential to limit or even prevent unwanted surface oxidation [7], Of course, once a specimen is loaded into an...
