A compositionally graded alloy in the PbTe-Sb2Te3-Ag2Te system was fabricated by the Bridgeman method. In the sample obtained for analysis, the length of the graded area was of the order of several tens of nanometers. Its thermal effusivity was measured with a thermal microscope, which required sputtering of a Mo film on the surface of the sample. The measured values of thermal effusivity depended on the thickness of the Mo film. However, it was difficult to sputter the Mo film uniformly in the wide area. Even though a relatively large target was used in the sputtering apparatus on the laboratory scale, the thickness of the Mo film just under the center of the target was larger than that in other areas. In this study, the measured thickness of the Mo film was calibrated with a high degree of accuracy against the reference glass slide. The thermal effusivity of the PbTe-Sb2Te3-Ag2Te alloy was in the range of 400-800 Ws(0.5)m(-2) K-1.