Electron Paramagnetic Resonance of Two Stoichiometry‐Induced Intrinsic Defect Centres in CuGaS 2

Related to the sulphur annealing conditions, two different EPR signals are observed in CuGaSg 2 With liquid sulphur, an isotropic photosensitive line is observed at g = 2.024 ± 0.002. With gaseous sulphur, an anisotropic spectrum, independent of light excitation, is recorded with g ∥[001] = 2.114 ± 0.005 and g ⊥ [001] = 2.005 ± 0.005. The suggested models for the intrinsic centres correspond respectively to a hole trapped on a copper vacancy and to a S   2 −molecule ion. The formation of both centres, important for the electrical compensation processes in CuGaS, is justified by the molecular composition of sulphur as a function of its physical state.