Characterisation of implanted surface layers in ion-thinned semiconductors by transmission electron microscopy

Transmission electron microscopy (TEM) rocking curves diffracted from inclined planes in argon ion-thinned Si and III–V semiconductors display a significant asymmetry around the Bragg condition. The simulation of the rocking curves shows that such an unexpected asymmetry can be attributed to the dilation of coherent crystalline surface layers implanted with argon atoms. The dark-field rocking curve asymmetry is shown to be directly related to the density of implanted argon atoms in the surface layers. Calculations also show that the rocking curve asymmetry is only observed for intermediate values of strain in the layer of a few percent, which corresponds to argon concentrations of a few at.% in the case of silicon or III–V semiconductors. This type of analysis is also relevant for the study of the strain state and chemical composition of coherently strained epitaxial layers.