Pulsed laser deposition of Y₂O₃ on Si: Characteristics of the interfacial layer

Thin Y₂O₃ films were directly grown on (100) Si substrates by the pulsed laser deposition technique. It has been found by high resolution cross-section transmission electron microscopy, x-ray reflectometry and x-ray photoelectron spectroscopy (XPS) that at the interface between Si and the grown layer, an interfacial layer always formed. Depth-profiling and angle-resolved XPS investigations showed that this layer consists of a mixture of substoichiometric SiO_x (x<2) and the deposited Y₂O₃ layer, without forming an yttrium silicate. The thickness of this interfacial layer depended on the oxygen pressure and temperature used during the deposition. The main oxygen source for its formation is the physisorbed oxygen which is trapped inside the grown layer during the laser ablation process. When the thickness of this low-k SiO_x was reduced by decreasing the oxygen pressure during laser ablation below the optimum value, a marked degradation of the electrical properties of the structure was noticed.