Formation and characterization of semiconductor Ca2Si layers prepared on p-type silicon covered by an amorphous silicon cap

Formation of calcium silicide on three types of templates: Si(111)7 x 7, 2D Mg2Si, and 3D Mg2Si, was studied during Ca deposition at 120 A degrees C in situ by Auger and electron energy loss spectroscopy, and by differential optical reflectance spectroscopy. A continuous Ca2Si layer is formed on 2D and 3D Mg2Si templates; but, on an atomically clean silicon surface (Si(111)7 x 7), a mixture of Ca2Si with another Ca silicide was found. The growth of a Si cap layer over the Ca silicide layers at about 100 A degrees C studied by in situ methods demonstrated the full embedding of Ca silicide in amorphous silicon, independent of the used template. Transmission electron microscopy, Rutherford backscattering spectrometry, atomic force microscopy, and electrical characterization of Schottky junctions revealed the Ca2Si and Mg2Si nanoparticles and the redistribution of Mg and Ca during the silicon cap growth and its effect on the electronic properties of the structures. Reproduction of the experiments on higher doped and better purity substrates is needed to understand better the role of Mg- and Ca-related defects, and defects of silicon generated by the growth process.