  BCl$_3$ is a promising candidate for atomic-precision acceptor doping in Si,
but optimizing the electrical properties of structures created with this
technique requires a detailed understanding of adsorption and dissociation
pathways for this precursor. Here, we use density functional theory and
scanning tunneling microscopy (STM) to identify and explore these pathways for
BCl$_3$ on Si(100) at different annealing temperatures. We demonstrate that
BCl$_3$ adsorbs selectively without a reaction barrier, and subsequently
dissociates relatively easily with reaction barriers $\approx$1 eV. Using this
dissociation pathway, we parameterize a Kinetic Monte Carlo model to predict B
incorporation rates as a function of dosing conditions. STM is used to image
BCl$_{3}$ adsorbates, identifying several surface configurations and tracking
the change in their distribution as a function of the annealing temperature,
matching predictions of the kinetic model well. This straightforward pathway
for atomic-precision acceptor doping helps enable a wide range of applications
including bipolar nanoelectronics, acceptor-based qubits, and superconducting
Si.
