We show how to obtain gold thin films with nanometric twins inside a single crystalline matrix, such that the twin volume fraction varies over one order of magnitude. The films are deposited by sputtering on rock salt single crystals at temperatures T_s between 200 °C and 400 °C. There is an orientation epitaxy with the substrate, so that the matrix has (001) planes parallel to the surface. Twins appear with four orientations which are obtained by mirror symmetry about the four {111} matrix planes. Transmission electron microscopy is used to determine the twin width (distance between the two coherent twin boundaries); an average of 4.0+-0.5 nm is obtained. Then, plane-views give the twin surface fraction, so that the volume fraction (total twin volume over total matrix volume) can be determined for each sample. The values are compared with those obtained from X-ray diffraction pole figures, and the agreement between the two methods is excellent. The twin volume ratio decreases from almost 2% at T_s=200 °C to 0.1% at T_s=400 °C. This aligns with models suggesting that twins form when nuclei coalesce during film growth, rather than during cooling back to room temperature. Furthermore, it is observed that the twins have a trapezoidal shape, that is, their length at the free surface is larger than at the interface with the substrate. Finally, it is shown that twin and matrix pole widths decrease with the deposition temperature, suggesting that the defect density is lower at high T_s.