Surface and buried interface layer studies on challenging structures as studied by ARXPS

Previous extensive studies were performed at Surface Science Western on the treatment of III-V semiconductors to produce surfaces suitable for subsequent epitaxial growth. XPS was used to study oxide formation, capping techniques and to monitor changes that would occur upon thermal desorption. The effects of a remote plasma on these surfaces was studied as well as to apply thin dielectric films of Si3N4 in order to study interfacial properties. ARXPS was performed in many cases to ascertain oxide layer thickness, uniformity and structure. For the types of surfaces studied – mirror finished semi-conductors, ARXPS is straightforward and the angular dependence is obtained by physically altering the surface orientation with respect to the analyser. While the sample can be repositioned with care to analyse the same spot, changing the angle will effectively change the sampling area, further, surface topography can preclude the use of ARXPS. Use of parallel angle-resolved XPS (PARXPS), now available on recent instrumentation, can alleviate these problems. In this case photoelectrons are collected simultaneously from a large angle. A multichannel detector allows this to be split into smaller angles thereby giving the PARXPS spectra without physically tilting the sample. Further, since the sample is not tilted, topographical effects are minimised allowing meaningful data to be extracted from not so perfect samples. To illustrate this a detailed PARXPS study on a gallium Indium eutectic (EGaIn) will be presented. Various methods of extracting the depth information from these spectra will be discussed. Finally, the application of using PARXPS to study buried interfaces will be briefly discussed.