Transmission electron microscopy rocking curves diffracted from inclined planes in argon ion-thinned Si and III-V semiconductors display a significant asymmetry around the Bragg condition. Kinematical and dynamical calculations of the rocking curves show that such an asymmetry can be attributed to the dilation of coherent crystalline surface layers implanted with argon atoms. The surface layers are characterized with two parameters, their width h and the strain component epsilon (z) normal to the thin foil plane. The dark-field rocking curve asymmetry is shown, for sufficiently high values of h (> approximately 2 nm), to strongly depend on epsilon (z) which is directly related to the density of implanted argon atoms in the surface layers. Calculations also show that a significant rocking curve asymmetry is only observed for intermediate values of epsilon (z) of about a few percentage points.