Graphene has aroused large interest in optoelectronic applications because of its broad band absorption and ultrahigh electron mobility. However, the low absorption of 2.3% seriously limits its photoresponsivity and restricts the relevant applications. In this paper, a method to enhance the sensitivity of graphene photodetector is demonstrated by introducing electron trapping centers and creating a bandgap structure in graphene. The carrier lifetime obviously increases, and more carriers are collected by the electrodes. Compared with intrinsic graphene detector, the defective graphene photodetector possesses high photocurrent and low-driving-voltage, which gives rise to great potential applications in photodetector area.
We studied thermal stability and its relationship to the glass-forming ability （GFA） of the Ni62Nb38-xTax （x=5, 10, 15, 20, 25） bulk metallic glasses （BMG） fi＇om a kinetic point of view. By fitting the heating-rate dependence of glass transition temperature （Tgonsct） and crystallization temperatures （Txonset and Txpcak） of the Ni62Nb38_xTax BMG using the Vogel-Fulcher-Tammann （VFT） equation, we obtained the ideal glass transition and crystallization temperatures （Tg0 and Tx2） and the fragility parameter （m）, and also constructed continuous heating transition （CHT） diagrams for crystallization of the BMG. The CHT diagrams of the BMG indicate enhanced thermal stability by Ta addition; the Tg~ as well as the Tx~ also illustrates this improved stability limit. The compositional dependence of m, which agrees well with that of the reduced glass-transition temperature, indicates a strong correlation between liquid fragility and glass-forming ability in the present alloy system. These results provide new evidence for understanding thermal stability, liquid fragility, and GFA in BMG.
