Desorption and lithographic patterning of halogen-terminated Si(100)-(2x1) using STM

Scanning tunneling microscopy (STM)-based hydrogen depassivation lithography is a well-established technique used for fabricating atomic-scale devices in Si. Incorporation of donor atoms from PH₃ into lithographic patterns in a Si surface allows for the formation of metallic wires, electrostatically defined quantum dots, and precise placement of donor atom qubits for quantum information (QI) research. However, interest in acceptor dopants and hole-based devices in QI and other fields necessitates the development of alternate precursor and/or resist chemistries for STM device fabrication. Here, we present results on the passivation and selective depassivation characteristics of halogen resists (Cl and Br) used for STM lithography on Si(100)-(2x1) at low and elevated temperatures (77 K, 300 K, 400 K). We explore STM tip-induced desorption and lithography as a function of tip bias, tunnel current, and electron dose. Through these studies, we demonstrate halogen lithography in an atomically precise mode where single Si dimer-wide features are depassivated, as well as a field emission mode for patterning larger areas of the halogen-terminated Si surface. This work moves us closer to realizing a resist and acceptor combination for fabricating atomic-scale, hole-based devices for QI.