Improving the thermal stability and operation speed of Sb7Se3 films via carbon nanolayers

The C/Sb7Se3 superlattice-like film was prepared by magnetron sputtering technology, and the effects of carbon nanolayers on the film and device properties were studied. The C/Sb7Se3 superlattice-like films show excellent thermal stability and data retention, especially the [C(3 nm)/Sb7Se3(3 nm)]5 film. The analysis of transmission electron microscopy and x-ray diffraction reveal that the high-quality multilayer structure of [C(3 nm)/Sb7Se3(3 nm)]5 is maintained. The segmentation of phase change material by amorphous carbon layer reduces the size of crystalline region, thus accelerates the crystallization rate. Element mapping indicates that C atoms and Se atoms in the annealed [C(3 nm)/Sb7Se3(3 nm)]5 films show obvious interlayer diffusion. The results of x-ray photoelectron spectroscopy and density functional theory manifest that atomic diffusion results in the formation of strong C-Sb and C-Se bonds in the phase transition layer and C atom prefers to occupying interstitial site in the center of the periodic structural unit of Sb2Se3 phase. Carbon atoms can effectively suppress grain growth and gradually move to the boundary of the grain, refining grain size, thus improving the stability of the amorphous phase. This study indicates that carbon nanolayers play an important role in improving the thermal stability and operation speed, reducing power consumption and resistance drift in Sb7Se3 films.