  The adsorption of AlCl$_{3}$ on Si(100) and the effect of annealing the
AlCl$_{3}$-dosed substrate was studied to reveal key surface processes for the
development of atomic-precision acceptor-doping techniques. This investigation
was performed via scanning tunneling microscopy (STM), X-ray photoelectron
spectroscopy (XPS), and density functional theory (DFT) calculations. At room
temperature, AlCl$_{3}$ readily adsorbed to the Si substrate dimers and
dissociated to form a variety of species. Annealing of the AlCl$_{3}$-dosed
substrate at temperatures below 450 $^{\circ}$C produced unique chlorinated
aluminum chains (CACs) elongated along the Si(100) dimer row direction. An
atomic model for the chains is proposed with supporting DFT calculations. Al
was incorporated into the Si substrate upon annealing at 450 $^{\circ}$C and
above, and Cl desorption was observed for temperatures beyond 450 $^{\circ}$C.
Al-incorporated samples were encapsulated in Si and characterized by secondary
ion mass spectrometry (SIMS) depth profiling to quantify the Al atom
concentration, which was found to be in excess of 10$^{20}$ cm$^{-3}$ across a
$\sim$2.7 nm thick $\delta$-doped region. The Al concentration achieved here
and the processing parameters utilized promote AlCl$_{3}$ as a viable gaseous
precursor for novel acceptor-doped Si materials and devices for quantum
computing.
