Investigation of single boron acceptors at the cleaved Si:B(111) surface

Abstract

The cleaved and (2×1) reconstructed (111) surface of p-type Si is investigated by scanning tunneling microscopy (STM). Single B acceptors are identified due to their characteristic voltage-dependent contrast which is explained by a local energetic shift of the electronic density of states caused by the Coulomb potential of the negatively charged acceptor. In addition, detailed analysis of the STM images shows that apparently one orbital is missing at the B site at sample voltages of 0.4 − 0.6 V, corresponding to the absence of a localized dangling-bond state. Scanning tunneling spectroscopy (STS) confirms a strongly altered density of states at the B atom due to the different electronic structure of B compared to Si.

Atomically precise impurity identification and modification on the manganese doped GaAs(110) surface with scanning tunneling microscopy

“…Examples are phosphorus 3 and boron in silicon, 4 beryllium, carbon, and zinc 5,6 as shallow acceptors in GaAs and silicon ͑Si Ga ͒ ͑Ref. 7͒ as a shallow donor in GaAs.…”

Electronic disorder of P- and B-doped Si at the metal–insulator transition investigated by scanning tunnelling microscopy and electronic transport

“…The high density of surface states and the heavy doping of Si:P also give rise to a charge accumulation at the surface and a space charge that subsides into volume within a depth of 9-10 nm, slightly depending on the type of buckling [19]. For Si:B, similar estimates lead to a depletion layer with a depth of 3-4 nm [33]. In the bulk, the bandgap of Si is 1.1 eV at RT and 1.2 eV at LT.…”

“…On the cleaved surface of heavily doped Si, a number of defects are generally observed. Apart from several adsorbate-induced features, one species exhibits a voltage-dependent contrast: an apparent protrusion at positive voltage and an apparent indentation at negative voltage for Si:P [25,34] and vice versa for Si:B [33]. Features with such characteristic voltage-dependent contrasts have been observed on a number of P-or B-doped samples with various doping levels and are attributed to individual dopant atoms at the cleaved Si(111)-2×1 surface [25,33,34].…”

Quantum phase transitions

“…This has been achieved by using scanning tunneling spectroscopy (STS), as demonstrated for Si:P [296,297], Si:B [298] and GaAsiSioa [299] and «-doped InAs [300]. Clustering or short-range ordering could drastically affect the behavior of the MI transition.…”