TeO(x) layers with controlled Te/0 ratio and thickness are prepared by thermal coevaporation of TeO2 and Te. Using various transmission and scanning electron microscopy techniques it is shown that the as-deposited layers represent a composite system, consisting of finely dispersed, partly agglomerated crystalline Te particles embedded in an amorphous TeO2 matrix with columnar structure and fine-grained substructure. The effect of annealing and laser exposure on the layers is investigated. A strong correlation of the change in transmission and the Te redistribution is found. It is shown that the variations in the optical properties of the TeOx layers are caused by aggregation of the crystalline Te particles and migration of Te to the upper free surface of the layer.