We have investigated a chromium–platinum pair in silicon by electron spin resonance measurement. A new ESR spectrum originating from a chromium–platinum pair has been detected in both n- and p-type silicons diffused with chromium and platinum. The anisotropic g-tensor obtained by analyzing the angular dependence of the ESR spectrum shows a monoclinic (C 1h ) symmetry with g-values of g 1=4.67, g 2=2.99, and g 3=1.80. The g 1 axis is along the <110 > direction. The g 2 and g 3 axes are perpendicular to the g 1 axis, and the g 2 axis is rotated from the <100 > direction to the <111 > direction at an angle of 20°. The anisotropic character of monoclinic (C 1h ) symmetry results from the nearest-neighbor configuration consisting of a Pt atom at a substitutional site distorted by the displacement of Pt along the <100 > direction and a Cr atom at the nearest-neighbor interstitial site. The ESR measurement under illumination suggests that a chromium–platinum pair forms a donor like electron trap level.

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