TIME-OF-FLIGHT NEUTRON-DIFFRACTION STUDY OF AMORPHOUS AND LIQUID GE-TE ALLOYS

The short-range structure in amorphous and liquid GexTe1-x alloys with x less than or equal to 0.33 has been investigated through time-of-fl ight neutron diffraction measurements. The first sharp diffraction pea k (FSDP) in the structure factor was observed in the amorphous state, implying that the structural units are partially connected each other, while, the FSDP was not obviously seen in the liquid state. The posit ion and area (relating the coordination number) of the first peak in t he amorphous distribution function were quite different from those in the liquid function. The difference function between distribution func tions at x=0.16 and 0.20, indicated that the first coordination shell in the alloy is composed of two nearest neighbor correlations, i.e., G e-Te and Te-Te. It was clarified from the first peak position of the d ifference function that both Ge-Te and Te-Te distances are 259 and 276 pm in the amorphous state, and 267 and 292 pm in the liquid state, re spectively. After all, it can be concluded that Ge-Te alloys have a di fferent local structure and different bonding nature among crystalline , amorphous and liquid states. These bonding differences result in a s harp change of electronic properties such as the magnetic susceptibili ty around crystallization and liquidus temperature.