Premium
STM–STS investigation of vacuum annealed ZnO nanoribbons
Author(s) -
Maffeis T. G. G.,
Penny M. W.,
Garbutt J. D. W.,
Wilks S. P.
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200982485
Subject(s) - band bending , annealing (glass) , scanning tunneling microscope , materials science , band gap , fermi level , quantum tunnelling , analytical chemistry (journal) , optoelectronics , condensed matter physics , chemistry , nanotechnology , metallurgy , physics , chromatography , quantum mechanics , electron
We present a scanning tunneling microscopy and spectroscopy (STM–STS) investigation of the effects of ultra high vacuum annealing and oxygen exposure onto ZnO nanoribbons synthesised by chemical vapour deposition. STM imaging revealed a width to height ratio for the nanoribbons between 2:1 and 3:1 and average width and height of 90 and 40 nm, respectively. Imaging before annealing showed the presence of surface contaminants, which were removed after annealing at 800 °C. Analysis of the STS data before annealing shows n‐type behaviour with a band gap of 3.4 eV and an upward band bending of 0.9 eV. Annealing up to 700 °C induced a reduction in surface band bending, towards a near flat band behaviour. After the 800 °C anneal the surface electronic properties were significantly altered, with a large increase of tunnelling current at negative sample bias leading to a narrowing of the apparent surface band gap and a mid gap Fermi level. This change was attributed to a loss of surface lattice oxygen and was found to be reversible upon O 2 exposure at room temperature. The anneal/O 2 exposure process could lead to a way of cleaning the ZnO nanoribbons without using ion bombardment techniques.