Elastic stiffness and thermal expansion coefficient of BN films

Room temperature stresses were found to be tensile for chemical vapor deposition films of the composition B2N and compressive for BN, with all films becoming more tensile with heating. Analyses of the stress-temperature curves of identical films of BN deposited on two different substrate materials yield values of 1.3×1012 dynes/cm2 for the elastic stiffness parameter E/(1−ν) and 1.0 ppm/°C for the thermal expansion coefficient. This technique is of general applicability to thin films and it is believed to be the first practical (nondestructive) means of determining both the elastic stiffness parameter and thermal expansion coefficient of a film.