We have modified the properties of diamondlike atomic-scale composite (DLASC) material of various thicknesses (5–70 &mgr;m) by means of cw Ar-ion laser annealing using a focused beam (∼2 &mgr;mspot size). These DLASC films [amorphous “diamondlike/quartzlike”a-(C:H/Si:O)] constitute a novel class of diamond-related materials. The laser annealing effects were investigated by micro-Raman scattering. The structure of these films can be altered locally from amorphous to nanocrystalline depending not only on the parameters of the annealing process (annealing time, laser intensity) but also the mechanical properties (hardness, stress) of the films. For comparison purposes we also measured the effects of thermal annealing. ©1997 American Institute of Physics.