Additional Homework Problems

CDP10-EB

  Titanium nitride films are used in decorative coatings as well as in wear-resistant tools. There is increasing interest in TiN because of its thermal stability, good diffusion barrier properties, and its low electrical resistivity
[J. Electrochem. Soc., 138, 500 (1991)]. Titanium nitride films were formed by CVD from a mixture of TiCl 4 , NH 3 , H 2 and Ar. The following observations can be made from the article:
     
   
  • The rate of deposition is independent of Ar and H 2.
  • At low partial pressures of both TiCl 4 and NH 3 the deposition rate appears to be first-order in TiCl 4 and second-order in NH 3 .
  • At high partial pressures of NH 3 the rate varies inversely with TiCl 4 The following mechanism has been suggested for the reaction:
     

image 10eq18.gif

     
   

It is believed that the gas-phase reaction to form the complex TiCl4 (NH 3 ) 2 is in equilibrium.

(a) Determine the rate expression for the suggested mechanism. Does it agree with experimental observations?
(b) Determine the reaction rate parameters.
(c) Do the data selected from the article agree with the data given below?

     

image 10eq20.gif