3:45 PM - 4:00 PM
[5p-A204-6] New structure of Cu4 complex in silicon
Keywords:Cu impurity, defect complex, electronic structure
Cu complex Cu4 is formed in silicon under appropriate conditions. The structure was believed to be a triangular pyramid with the substitutional Cu at the center surrounded by three interstitial Cu atoms. The local symmetry is C3v. Recently, we have found a more stable structure of Cu4 complex. The new structure is called U-type, while the previous one is called N-type. In this talk, we present the electronic properties of these types, and discuss the stability of U-type on this basis.
In U-type, the substitutional Cu(s) is largely displaced toward an anti-bonding site, forming Cu4 tetrahedron together with other interstitial Cu atoms. In addition, this Cu tetrahedron together with four neighboring Si atoms constructs a dodecahedron Cu4Si4 with Td symmetry. The formation energy of U-type is 0.5 eV less than that of N-type. The electronic structure of U-type is characterized as being more metallic bonding than usual covalent bonds of the substitutional Cu(s).
In U-type, the substitutional Cu(s) is largely displaced toward an anti-bonding site, forming Cu4 tetrahedron together with other interstitial Cu atoms. In addition, this Cu tetrahedron together with four neighboring Si atoms constructs a dodecahedron Cu4Si4 with Td symmetry. The formation energy of U-type is 0.5 eV less than that of N-type. The electronic structure of U-type is characterized as being more metallic bonding than usual covalent bonds of the substitutional Cu(s).