Thin film semiconductor nanomaterials and nanostructures prepared by physical vapour deposition: An atomic force microscopy study

Amorphous/nanocrystalline SiOx/CdSeSiOx/CdSe, GeS2/CdSeGeS2/CdSe, SiOx/ZnSeSiOx/ZnSe and Se/CdSeSe/CdSe amorphous multilayers (MLs) were grown by consecutive physical vapour deposition of the constituent materials at room substrate temperature. A step-by-step manner of deposition was applied for the preparation of each layer (2–10nm thick) of MLs. Surface morphology has been investigated by atomic force microscopy (AFM) in order to get information about ML interfaces. For a scanned area of 3.4×4μm2SiOx/CdSeSiOx/CdSe and GeS2/CdSeGeS2/CdSe MLs showed surface roughness which is around three times greater than the roughness of SiOx/ZnSeSiOx/ZnSe MLs. This observation has been connected with effects of both film composition and deposition rate. For a scanned area of 250×250nm2 the roughness determined in all MLs displayed close values and a similar increase with the ML period. The latter has been related to the flexible structure of amorphous materials. The AFM results, in good agreement with previous X-ray diffraction and high resolution electron microscopy data, indicate that the application of step-by-step physical vapour deposition makes possible fabrication of various amorphous/nanocrystalline MLs with smooth interfaces and good artificial periodicity at low substrate temperatures.