ADSORPTION STUDIES ON BORON-NITRIDE SUBSTRATES

We report here the results of a study of the substrate quality of boro n nitride powder samples subjected to different cleaning treatments. A rgon vapor pressure isotherms were used to determine the resulting qua lity. We found that washing the BN powder in methanol prior to heating it under vacuum to 900 degrees C is an effective treatment for produc ing high-quality substrates. On the other hand, we found that vacuum h eat treatment to 900 degrees C, alone, is not always sufficient to eli minate all the impurities present in the BN powder. We have also used cycles of adsorption followed by desorption measurements to investigat e the occurrence of capillary condensation for Ar on BN. We found hyst eresis loops characteristic for this phenomenon.