A method for measuring low-level oxygen concentration in thin silicon crystals by photoluminescence (PL) is investigated using a radiative carbon-oxygen complex (C center : 0.79 eV) formed by supplementing carbon-lean silicon crystal with carbon through carbon implantation. Oxygen concentrations between 1 x 10(15) and 1 x 10(18) atom/cm(3) in thin crystal (<1 mu m) can be determined by measuring photoluminescence intensity of the C center in as-implanted samples implanted at fluences between 1 x 10(13) and 1 x 10(15) ion/cm(2) of carbon. Although the possibility of detecting very low oxygen gen concentrations (<1 x 10(13) atom/cm(3)) is seen for a thick sample prepared through the sequence of implanting carbon, high temperature annealing makes the preparation unsuitable for the quantitative measurements of oxygen concentrations in a thin crystal of micrometer thickness.