N-nH complexes in GaAs studied at the atomic scale by cross-sectional scanning tunneling microscopy

Douwe Tjeertes (Corresponding author), Tom Verstijnen, Alicia Gonzalo, Jose M. Ulloa, M.S. Sharma, M. Felici, A. Polimeni, F. Biccari, M. Gurioli, G. Pettinari, C. Sahin, Michael E. Flatté, Paul M. Koenraad

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Hydrogenation of nitrogen (N) doped GaAs allows for reversible tuning of the band gap and the creation of site controlled quantum dots through the manipulation of N−nH complexes, N−nH complexes, wherein a nitrogen atom is surrounded by n hydrogen (H) atoms. Here we employ cross-sectional scanning tunneling microscopy (X-STM) to study these complexes in the GaAs (110) surface at the atomic scale. In addition to that we performed density functional theory (DFT) calculations to determine the atomic properties of the N−nH complexes. We argue that at or near the (110) GaAs surface two H atoms from N−nH complexes dissociate as an H2 molecule. We observe multiple features related to the hydrogenation process, of which a subset is classified as N-1H complexes. These N-1H related features show an apparent reduction of the local density of states (LDOS), characteristic to N atoms in the GaAs (110) surface with an additional apparent localized enhancement of the LDOS located in one of three crystal directions. N−nH features can be manipulated with the STM tip. Showing in one case a switching behavior between two mirror-symmetric states and in another case a removal of the localized enhancement of the LDOS. The disappearance of the bright contrast is most likely a signature of the removal of an H atom from the N−nH complex.
Original languageEnglish
Article number125304
Number of pages10
JournalPhysical Review B
Issue number12
Publication statusPublished - 11 Sept 2020


We acknowledge S. Rubini (IOM-CNR, Italy) for providing samples at an early stage of the research. A.G. and J.M.U. acknowledge funding from the Spanish MINECO through project MAT2016-77491-C2-1-R. M.S., M.F., and A.P. acknowledge funding from the European Unions Horizon 2020 Research and Innovation Program under the Marie Skodowska-Curie Grant Agreement No. 641899 (PROMIS), from the Regione Lazio Program Progetti di Gruppi di ricerca legge Regionale n. 13/2008 (SINFONIA project, prot. n. 85-2017-15200) via LazioInnova spa, and from Sapienza Università di Roma via Fondi Ateneo 2018-2019, SapiExcellence, and Avvio alla Ricerca. C.S. and M.E.F. acknowledge support from the NSF DMREF program through Award No. DMR-1921877.

FundersFunder number
Marie Skłodowska‐Curie
Horizon 2020 Framework Programme641899
Ministerio de Economía y CompetitividadMAT2016-77491-C2-1-R
Horizon 2020


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