At present, CVD plays vital role in microelectronics, wear and radiation resistant coatings, fiber optics, and the purification and fabrication of exotic materials, from ultra-low expansion glasses to high purity refractory metals. CVD has four major advantages over most other thin film deposition techniques. First, the process allows tight control over gas stream flow rate and composition which leads to predictable and repeatable film composition and graded structures, if desired. Second, the thermal activation of the reaction establishes thermal equilibrium at the site of film deposition, producing tight, highly coordinated structures. Third, the throwing power of CVD is excellent, allowing for the coating of less accessible surfaces such as the inside of tubes. Last, the techniques are especially well suited to the deposition of refractory materials which techniques are difficult by other techniques.