Low-Temperature Associated Interface Influence on the Black Phosphorus Nanoflakes

The temperature-dependent structure properties of few-layer black phosphorus (BP) nanoflakes supported on the Si substrate and suspended on the holes are investigated using the Raman spectroscopy in the range of 77-293 K. The temperature coefficients of three main Raman modes for supported BP are larger than those of suspended BP because of the interface effects, mainly the tensile strain and the different thermal expansion coefficients (TEC) between the substrate and BP nanoflakes. The out-of-plane vibration is more apt to be affected by the initial strain, whereas the influence on the in-plane vibrations is negligible. During the varied temperature circulation, the temperature coefficients in the heating process are much larger than those in the cooling process because of the interface influences. Thus, the interfacial interaction between BP and the substrate plays an important role in the thermal-mechanical properties of BP. These findings pave a way for the further study of thermal-mechanical related applications of flexible BP nanodevices.