Atomically-precise, delta-doped structures forming electronic devices in silicon can be fabricated using depassivation lithography in a scanning tunneling microscope (STM). The use of halogen chemistries on the Si(100) surface, in particular, offers a promising path towards atomic-scale manufacturing of acceptor-based devices. It has been well established that incorporation of P atoms from PH₃ into lithographically patterned H resists on Si enables metallic wires and precisely placed donor atom qubits to be fabricated for quantum information (QI) research. Interest in acceptor dopants for hole-based devices and novel materials such as superconducting Si necessitates the development of halogenated acceptor precursors and corresponding halogen resists compatible with STM fabrication. Here, we present results studying the adsorption and incorporation of Al from AlCl₃ and B from BCl₃ onto the Si(100) surface. We show that AlCl₃ readily adsorbs onto bare Si(100) and forms novel chlorinated Al chains at annealing temperatures below 450^oC. Al then becomes incorporated into the surface at higher annealing temperatures. Likewise, BCl₃ also readily adsorbs and we show it is selective to H- and Cl-based resists, which are both patterned using STM. We explore the effect of annealing temperatures on B incorporation into the surface and the resulting electrical activation of B-delta layers with peak concentrations greater than 10²⁰ B/cm³_, as measured by secondary ion mass spectrometry. Finally, we perform low-temperature electrical characterizations of B-delta layers and demonstrate the fabrication of atomic-scale, B-doped devices using STM. This work moves us closer to demonstrating superconducting Si as well as atomic scale, hole-based devices for QI.

Kevin Dwyer

University of Maryland at College Park

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