Pattern formation in PbTe multilayer films

Atomic force microscopy is used to study the surface morphology evolution o f PbTe films that have been grown by hot-wall epitaxy on BaF2(111) substrat es. We found that the morphology strongly depends on the doping type of the films. For film thicknesses of about 1500 nm, Te rich films (p-type) show uniform pyramids with hexagonal bases whereas Pb rich films (n-type) exhibi t irregularly shaped crystallites with (111) terraces on top. By growing np n multilayers we observe the formation of uniform triangular pyramids in th e second n-layer. The arrangement of the pyramids can be controlled by vary ing the thickness of the p-layer. In addition to this pattern formation, th e insertion of the p-layers reduces the surface roughness compared with tha t of the single n-layers. (C) 2000 Elsevier Science B.V. All rights reserve d.