Experimental study of MgB2 decomposition

The thermal stability of MgB2 has been studied experimentally to determine the role of thermodynamic and kinetic barriers in the decomposition process . The MgB2 decomposition rate approaches one monolayer per second at 650 de greesC and has an activation energy of 2.0 eV. The evaporation coefficient is inferred to be similar to 10(-4), indicating that this process is kineti cally limited. These values were inferred from in situ measurements using a quartz crystal microbalance and a residual gas analyzer, in conjunction wi th ex situ measurements of redeposited material by Rutherford backscatterin g spectroscopy and secondary ion mass spectroscopy. The presence of a large kinetic barrier to decomposition indicates that the synthesis of MgB2 thin films conditions may be possible with vacuum processing, albeit within a n arrow window in the reactive growth conditions. (C) 2001 American Institute of Physics.