We report high-resolution X-ray diffraction studies of combinatorial epitaxial Ge (0 0 1) thin-films with varying doping concentrations of Co and Mn grown on Ge (0 0 1) substrates. The crystalline structure of the epitaxial thin-film has been determined using crystal-truncation rod (CTR) measurements and fitting analysis. By analyzing the fine interference fringes in the CTR intensity profile, strain sensitivity of similar to 0.003% has been achieved. Using this method, the evolution of interfacial structures has been quantified as a function of doping concentration. (C) 2007 Elsevier B.V. All rights reserved.