Z. TITL AND SUBTITLE S. FUNDING NUMBERS Pt and Ir Contacts to Si FINAL REPORT A FOSR-90-0342

13 ABSTRACT (Maxmmum 200 wove) Si and group IV based Schottky barriers (SB) below about 0.2eV are of considerable technological importance since detectors based upon them will be able to probe deep into thuv infrared while maintaining well established processing techniques. Investi-S gations relating to this problem have been..carried out using ultra-high vacuum. to techniques and X-ray photoelectron spectroscopy. Two approaches have been persued, on ^ by tailoring the interface geometric and hence electronic structure and the other by using a reduced band gap material. The systems studied were Sn on SiX 111) and Pt on Ge(111). Sn invokes several surface reconstructions oni Si(lil) one of which, the 2/3 structure has an associated electronic structunre with the Fermi level situated (3.14+ J.1U)eV above the valence band maximum (VBIM). This means that the corresrnondincr p-typf 3B is also (0.14±O.1OeV, well below the value of fl.22eV found at the PtSi/Si(10)) qt interface. Similarly, when Pt was deposited onto Ge(lflO), the Fermi level was positio ed _ _ ('~.12±".04)eV above the VBM, again resulting in a p-type SB significantly lower than that at the PtSi/Si(lor)) interface. Chemical interactions at the Pt/Ge interface ar