POLYCRYSTALLINE IRIDIUM SILICIDE FILMS - PHASE-FORMATION, ELECTRICAL AND OPTICAL-PROPERTIES

Electrical and optical properties of thin Ir(x)Si1-x films are investi gated in the composition range 0.25 less-than-or-equal-to x less-than- or-equal-to 0.55 in dependence on the crystallization stage. The films are prepared by dc-magnetron codeposition and annealed at temperature s between 400 and 1170 K. The X-ray diffraction measurements show phas e formation sequences in dependence on annealing which are in general agreement with the phase diagram of Ir-Si bulk material. According to the dominant phases (IrSi, Ir4Si5, Ir3Si5, and IrSi3 with decreasing x ) films are obtained with metallic or semiconducting properties. Films with the semiconducting compound Ir3Si5 as main phase show a large th ermopower only in a small composition range depending on grain size. T he optical gap of Ir3Si5 is determined by absorption measurements to b e 1.56 eV.