Influence of ion-implantation on physical properties of silicon

Full text: Last years the ion-implantation is widely used for creation heteroepitaxial films, diffusion barriers and ohmic contacts. In this connection, scientific and practical interest represents studying physical properties ion-implanted materials. In this work the specific resistance and Schottky barrier height of Si surface, implanted by Ba+, Na+ and Co+ ions is investigated. Ions energy are E0=1-5 keV. In all cases high doses ion-implantation (D≥1016 cm-2) in combination with annealing result in formation of compounds such as BaSi2, NaSi2, and CoSi2. Measuring has shown, that resistance silicides films prove lower in comparison with the surface resistance of a substrate (silicon). It is shown, that values of a specific resistance and Schottky barrier height for all studied silicides films are given. These data apply to monocrystal films, obtained at optimum conditions. As evident, that among silicides films the greatest specific resistance has Mn2Si3. Besides it is necessary to note, that value ρ not always strongly depends on correlation of concentration of atoms Me/Si. Apparently, it depends also on type of bond between atoms Me-Si, crystalline and electronic structure of silicide. On dependence, ρ(T) for film Mn2Si3/Si which in area T=300-1100 K, little increases ρ, two obvious maximums are detect at T1=600 and T2=750 K, it is probably the bound with depletion of impurity levels. It is necessary to note, that such maximums for thick sample silicides are not detect. It is possible, that in Mn2Si3 forbidden zone is present two impurity levels located near to a bottom of conduction band (Eg=0.056 and 0.064 eV). In interval T=1100-1300 K are occurred small decrease ρ. The last is bound to some decomposition Mn2Si3 and enrichment of surface by metal atoms. With increase T, starting with T=1300 K intensive decomposition Mn2Si3 and evaporation of silicide components from surface is observed, that result in sharp increases ρ. By formula Eg=T·K·ln(NcNv/Nd2) we size up Mn2Si3 forbidden gap. Thus it was supposed, that values Nc and Nv for silicide visibly do not differ from those for silicon. Impurity density Nd size up on sensitivity optical absorption method. In that case Nd=1022 m3. Calculation has shown, that for Mn2Si3 value Eg=0.6-0.7 eV. These experimental data are satisfactory fit with the results obtained by ultraviolet photoelectron spectroscopy. It is visible, that values Schottky barrier height for all investigated systems to lie in the range of 0.6-0.65, that essentially does not differ from known data obtained for thick films