Phase transitions occurring at surfaces of solids are of special interest both for basic reasons related to the onset of bulk transitions and study of ordering and disordering of 2D structures and for applications related to possible use of surfaces under non-standard conditions for example in electronic and optoelectronic devices. An important issue addressed in several recent studies is the structural transition of a class of silicon and germanium surfaces taking place at high-temperatures. The metallization of those surfaces, usually interpreted as due to incomplete surface melting, has been subject of intense research. In particular, in a recent study, we have shown that high-temperature metalization can be studied by using EELS (Electron Energy Loss Spectroscopy) and AES (Auger Electron Spectroscopy) at different probing depths with a fine regulation and a precise calibration of the sample temperature. Use of photoemission with synchrotron radiation energy tunable sources will be discussed as a way to obtain complementary and quantitative information on the systems of interest but also in important technological study of high temperature melting and oxidation of metals and alloys and melting of highly covalent solids surfaces.