The stability and surface reactivity of gallium phosphide nanocrystals

The stability and surface reactivity of GaP nanocrystals were characterized by TG-DTA, XRD and XPS measurements. The samples were heated in O-2 and N- 2 atmospheres respectively. The experimental curve which describes the mass change as a function of temperature shows that the mass decreases under 33 0 degrees C but increases in two stages between 330 degrees C and 550 degre es C. The curves obtained in O-2 and N-2 are obviously different. The resul ts of XPS indicate that the density of oxygen atoms bonded chemically to th e gallium atoms on the surface increases when the sample is heated in O-2 u p to 200 degrees C, whereas the density of nitrogen atoms increased when he ated to 330 degrees C in N-2. It can be concluded that the N-2 could be act ivated on the surface of GaP nanocrystals at a rather low temperature, and highly reactive nitrogen atoms formed. Our result obtained makes it possibl e to synthesize a series of nitrogen-containing compounds in N-2 gas under moderate conditions.