Ultrafast dynamics of BixSb1-x film studied by femtosecond pump–probe technique

The BixSb1-x film is an important phase change material. The ultrafast dynamics of BixSb1-x film is studied by the femtosecond pump–probe technique with an 80 fs pulsed laser. Experimental results show that the reflectivity change increases with the fluence of the pump laser. The fast increase of the reflectivity occurs between 100 and 800 fs. Subsequently, the slower recovery of the reflectivity on a time scale of 1.24–18.3 ps is detected. We also found that the reflectivity change can be greatly affected by the ratio between Bi and Sb composition in BixSb1-x materials with x = 0.2 and 0.88. These experimental results should be helpful for developing new devices with ultrafast dynamics of BixSb1-x film and ultrafast optical switching.