[en] A study has been made of the dependence of electrical conductivity and structure on the target temperature of C⁺-ion implanted diamonds. C⁺ ions were chosen in order to restrict the effects of implantation principally to surface damage. Implantation was performed at 150 keV into natural Ia-type diamonds, held at temperatures of -100 or 200degC, with doses of 3x10¹⁵-5x10¹⁶ ions/cm². The sheet resistivity was measured by a four-point probe method at room temperature. Sheet resistivity was found to vary, depending on the implantation temperature, by four orders of magnitude. Raman spectra were obtained and analyzed by means of a conventional backscattering geometry, using an argon laser at 514.5 nm and 200 mW. The modified Raman spectra contained three broad peaks. The broad peak at 1360 cm^-1 is assigned to disordered graphite, while that at 1585 cm^-1 is assigned to graphite, and that at approximately 1500 cm^-1 is considered to be due to amorphous carbon. The peak intensities at 1360 and 1585 cm^-1 revealed few differences at target temperatures of -100 and 200degC. However, that at approximately 1500 cm^-1 showed large differences in intensity. We think that the amorphous structure assigned to the peak at 1500 cm^-1 is primarily responsible for the variant sheet resistivity, which can be explained by percolation processes. (orig.)