In this work, the ion-matrix sheaths near planar targets with infinitely long, semicylindrical grooves are studied analytically to optimize ion implantation, concerning a broad range of industrial products. The potential profiles inside and outside the groove are derived and the velocity components inside the groove are estimated. The variation of the angle of incidence on the surface of the groove and the constant potential contours outside the groove are obtained. Results are observed to be in good agreement with the numerical simulations. Finally, suggestions for improving the uniformity of implantation on the surfaces of such grooves are stated. (C) 2003 American Institute of Physics.