THE FORMATION OF SPUTTERED TA A-SI AND A-SI/TA INTERFACES IN A-SI/TA/A-SI/C-SI STRUCTURE/

The atomic structure of tantalum (Ta)-amorphous silicon (a-Si) interfa ces has been investigated using a-Si/Ta/a-Si multilayers, sputtered on unheated crystalline silicon (c-Si) substrates without breaking the v acuum. The back and the top Si layers were respectively 1000 and 500 A ngstrom thick, while the Ta thickness was 250 Angstrom. The concentrat ion profiles and the crystallographic structure were obtained using th ree complementary techniques: X-ray photoelectron spectroscopy, grazin g incidence X-ray diffraction and specular X-ray reflectometry. In par ticular, we demonstrate that Ta/a-Si and a-Si/Ta interfaces are diffus e with an interpenetration-depth of the order of 20 Angstrom. The Ta l ayer is not well crystallised and its density is 12% lower than in the bulk material.