Internal stress induced in the process of boron coating

Internal stresses induced in boron films formed by vacuum deposition were s tudied to find the generation mechanism of compressive stresses by an optic ally levered laser method. It a as found that the internal stresses of boro n thin films changed from tensile to compressive with increasing substrate temperatures and decreasing deposition rates. Deliberate addition of oxygen gas in an atmosphere with a pressure of 0.02 mTorr did not clearly change internal stresses, though oxygen content was increased. According to the ob servation by a transmission electron microscope (TEM), the film structure w as in an amorphous state based on icosahedral subunits. An interatomic dist ance for the high deposition rate (0.5 nm/s) was slightly larger by 1.7% th an that for the low deposition rate (0.06 nm/s). This result seems consiste nt with a film formation model based on adatom migration. (C) 1999 Elsevier Science B.V. All rights reserved.