Three new silicon/silicon oxide interfaces have been synthesized using the spherosiloxane clusters H-8-Si8O12, H12Si12O18, H14Si14O21, and Si(100)-(2x1). The structure of the interfaces have been characterized by Si 2p core level photoemission spectroscopy. Reactions of H8Si8O12 with Si(111)-(7x7) and Ge(100)-(2x1) were also explored. The use of the cluster derived interfaces as spectroscopic models for thermal Si/SiO2 interfaces is discussed in terms of current methods for assigning photoemission spectra at solid/solid interfaces and the structural models proposed for the Si/SiO2 interface.