Electroluminescence and high-frequency voltage-capacitance methods are used to study Si/SiO₂ structures obtained by thermal oxidation of KÉF-5 (100)Si wafers at 950°C in wet oxygen (oxide thickness 250 nm). The structures are irradiated by 130-keV argon ions with doses in the range of 10¹³-3.2 × 10¹⁷ cm^-2. A correlation between the origin, properties, and formation mechanism of implantation-induced defects in the oxide layer is established, and a model of defect formation is proposed.