Hot filament chemical vapor deposition of crystalline boron films

Abstract

This article reports on the conditions required for the growth of crystalline boron films on silicon substrates by hot filament chemical vapor deposition method. The reactive gas was 3% diborane diluted in hydrogen. The films were characterized by optical, electronic, and atomic force microscopies; x-ray diffraction; and energy dispersive, electron energy loss, Raman, x-ray photoelectron, and Auger spectroscopies. The parameters that affect the morphologies of the films have been investigated. It was concluded that faceted crystals are produced at low B2H6 flows and working pressures below 200 mT. α-boron is produced between 530 and 600°C. Deposition outside this range produces thin films with a wide variety of morphologies. This result indicates that the films crystallize through a process called abnormal or discontinuous grain growth. It is assumed that this is due to the anisotropic surfaces of boron allotropes.