The adsorption of carboxy-terminated deuterated polystyrene chains to a surface from a polymer melt has been studied using helium (3) nuclear reaction analysis. These chains are initially uniformly distributed in a matrix of (protonated) polystyrene. On annealing above the glass transition temperature they physically end-adsorb onto the native oxide layer on a silicon substrate. We have measured adsorbed amounts and concentration profiles of the adsorbed layer as a function of the annealing time and the molecular weight of the matrix. A depletion region is initially observed behind the adsorbed layer which persists for long times in some cases. The width and depth of the depletion layer depends strongly on the molecular weight of the matrix polymer and cannot be simply explained in terms of simple diffusion of the functionalized chains.