The origin of sub-diffraction-limit apertures in Sb-based thin films is discussed. Electromagnetic energy can be channeled by these apertures thus allowing near-field focussing- the Super-RENS effect. The aperture formation within Sb, Sb2Te3, Sb2Te, SbTe and Ge2Sb2Te5 is investigated by time resolved optical pump-probe techniques and found to occur without melting. Density functional calculations have shown that these materials exhibit a thresholdlike change in their optical properties below their melting temperatures. The threshold is shown to be a consequence of thermally induced misalignment of p-orbital bonds. It is the non-linearity of this process that leads to the formation of the sub-diffraction-limit apertures.