A method for preparing a substrate for detaching a layer by irradiation of the substrate with a light flux for heating a buried region of the substrate and bringing about decomposition of the material of that region to detach the detachment layer. The method includes fabricating an intermediate substrate including a first buried layer, and a second covering layer that covers all or part of the first layer, with the covering layer being substantially transparent to the light flux and with the buried layer formed by implantation of particles into the substrate, followed by absorbing the flux, and selectively and adiabatically irradiating a treated region of the buried layer until at least partial decomposition of the material constituting it ensues.