Our group utilizes XPS to quantify the oxidation of unstable semiconductors and to establish the coverage of organic molecules on a semiconductor surface. Bruce Brunschwig at Caltech also maintains a series of tutorials as well.
Venables lecture notes on Surfaces and Thin Films.
For instance, water adopts a particular structure in the liquid state so that it can form four hydrogen bonds, but at the surface, a water molecule wouldn’t be surrounded by water anymore! So, water molecules at the surface rearragnge to make the best of a bad situation, and this one reason why water has such a high surface tension! Even the atoms in a solid rearrange at a surface, and if that’s the case, being able to quantify exactly what atoms are where may be critically important to that material’s behavior!įor a detailed description of surface processes and measurement techniques, see John A. Materials rearrange at their surfaces and that makes surface quantification very important in material science. The second aspect of XPS that is useful is that it reveals quantitative ratios of the atomic species at that surface. This may be a feature or a bug depending on your point of view, but for a group like ours where we could make a “perfect” semiconductor right up until it reacts with oxygen in the air, surface sensitivity is absolutely critical for understanding what happened. The first thing is that it’s surface sensitive. There are a couple of features that make XPS so valuable as an analytical technique. For those keeping track the other big X-ray techniques out there are X-ray diffraction (XRD) which is the scattering of X-ray light (so X-rays in and X-rays out), and X-ray fluorescence where an atom is excited to a high energy level and it emits X-rays in falling back down to its ground state (usually electrons in and X-rays out). Some of this electrons manage to escape, so it’s X-rays in and electrons out.
This is a technique in which X-rays hit a sample and interact with core-level electrons. X-ray Photoelectron Spectroscopy (XPS) is the grandaddy of electron spectroscopies, and one of many techniques that involves X-ray light. XPS and UPS Background – Grimmgroup Research
0 kommentar(er)
