No abstract

No abstract

Boron doping of chemical vapor deposited (CVD) diamond films plays an important role for modification of their electrical properties, as well as it improves crystallinity of the resulting films. A comparative study of crystalline quality has been made for boron doped and undoped CVD diamond. It is also found that the edge emission near 240 nm in cathodoluminescence (CL) is significantly intensified by boron incorporation. It is observed that the hydrogen plasma etching rate of B-doped CVD diamond is much smaller than the etching rate of undoped diamond. This proves the fact, that boron incorporation during CVD growth of diamond films can lead to better crystal quality.

)}. We give a necessary and sufficient condition for the existence of a strongly closed subgraph which is (c r +1 + a r +1 )-regular of diameter r + 1 containing a given pair of vertices at distance r + 1.

Let 1 be a distance-regular graph of diameter d and valency k>2. If b t =1 and 2t d, then 1 is an antipodal double-cover. Consequently, if f >2 is the multiplicity of an eigenvalue of the adjacency matrix of 1 and if 1 is not an antipodal doublecover then d 2f&3. This result is an improvement of Godsil's bound. 1996Academic Press, Inc.