AlCl3-Dosed Si(100)-2 × 1: Adsorbates, Chlorinated Al Chains, and Incorporated Al
The adsorption of AlCl3 on Si(100) and the effect of annealing the AlCl3-dosed substrate were 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, AlCl3 readily adsorbed to the Si substrate dimers and dissociated to form a variety of species. Annealing the AlCl3-dosed substrate at temperatures below 450 °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 °C and above, and Cl desorption was observed for temperatures beyond 450 °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 1020 cm-3 across a ∼2.7 nm-thick δ-doped region. The Al concentration achieved here and the processing parameters utilized promote AlCl3 as a viable gaseous precursor for novel acceptor-doped Si materials and devices for quantum computing.