Electron spin resonance identification di-carbon-related centers in irradiated silicon

A previously unreported electron spin resonance (ESR) spectrum was found in γ-ray irradiated silicon by the detection of the change in microwave photoconductivity arising from spin-dependent recombination (SDR). In the specially prepared silicon crystals doped by ¹³C isotope, a well resolved hyperfine structure of SDR-ESR lines due to the interaction between electrons and two equivalent carbon atoms having nuclear spin I = 1/2 was observed. The Si-KU4 spectrum is described by spin Hamiltonian for spin S = 1 and of g and D tensors of orthorhombic symmetry with principal values g₁ = 2.008, g₂ = 2.002, and g₃ =2.007; and D₁ = ± 103 MHz, D₂ = 170 MHz, and D₃ = ± 67 MHz where axes 1, 2, and 3 are parallel to the [11-0], [110], and [001] crystal axes, respectively. The hyperfine splitting arising from ¹³C nuclei is about 0.35 mT. A possible microstructure of the detect leading to the Si-KU4 spectrum is discussed.