Excimer-laser photofragmentation of boron trichloride and its implications for laser vapour deposition and doping processes

Abstract

The photolysis of BCl₃ at the excimer-laser wavelengths of 193 and 248 nm has been investigated by mass spectroscopic and fluorescence techniques. At 193 nm, the BCl (A¹Π), excited B (B*) and BCl_x⁺(x= 0, …, 3) species are detected, whereas at 248 nm, BCl (A ¹Π), B*, Cl₂(2³Π_g) and BCl_x⁺(x= 1, 2) are detected. The pressure and fluence dependences of the signals are determined. At 193 nm, BCl₃ is proposed to undergo one- and two-photon excitations, the former resulting in BCl₂ and the latter in BCl (A ¹Π) and BCl_x⁺(x= 3, 2). In the case of the 248 nm excitation, the observed emitting species are shown to derive from secondary reactions that take place following two-photon photoexcitation/fragmentation of BCl₃. Implications of the observations herein for the vapour and doping processing by laser of BCl₃ are discussed. In particular, for processing at 248 nm, the observed photoinduced reactivity may be significant and should be considered in addition to any pyrolytic mechanism.