In parallel with our studies of the mechanisms of pulsed laser deposition (PLD) of thin films, we characterize the nanostructures grown by PLD methods using electron microscopy and other techniques. This activity builds on our earlier work demonstrating the potential of 193 nm PLD as a catalyst-free route to growing uniform arrays of ultrathin ZnO nanorods, and the use of PLD-grown, patterned thin films of ZnO as templates for selected area growth of aligned nanorods (by PLD) and of aligned nanorods and nanotubes (by hydrothermal methods). Our attention has now turned to studying the frictional properties of such nanorod arrays (in collaboration with Dr Wuge Briscoe) and to identifying process conditions appropriate for growing nanostructures of other oxide materials (MoO3, WO3, etc.).
TEM images of ZnO films.
The images above show (a) low and (b) high resolution TEM images of a single ZnO nanorod broken from a nanorod array deposited by diffusive PLD. Panels (c) and (d) show SEM images (overview and detail, respectively) illustrating selective area growth of ZnO nanorods by using a TEM grid as a shadow mask during seed layer deposition.
SEM images of WOx nanostructures grown on a copper substrate.
The figure above shows progressively higher resolution SEM images of WOx nanorods grown on a Cu substrate by PLD. (a) as-grown tangle of dendritic nanorods; (b) ‘single’ nanorod demonstrating the emergence of first (and in some cases second) generation daughter nanorods, (c) detail of the tip of a single nanorod shaft.
Representative publications:
Incident fluence dependent morphologies, photoluminescence and optical oxygen sensing properties of ZnO nanorods grown by pulsed laser deposition, X. Liu, Ye Sun, M. Yu, Y. Yin, B. Yang, W. Cao and M.N.R. Ashfold, J. Mater. Chem. C, 3, 2557-62 (2015).
Tungsten oxide nanorod growth by pulsed laser deposition: influence of substrate and process conditions, P. Huang, M.M.A. Kalyar, R.F. Webster, D. Cherns and M.N.R. Ashfold, Nanoscale 6, 13586-97, (2014).
Sustained frictional instabilities on nanodomed surfaces: stick-slip amplitude coefficient, B. Quignon, G.A. Pilkington, E. Thormann, P.M. Claesson, H. Leese, D. Mattia, M.N.R. Ashfold, S.A. Davis and W.H. Briscoe, ACS Nano 7, 10850-62, (2013).
Arrays of nanorods composed of ZnO nanodots exhibiting enhanced UV emission and stability, Y. Yin, Y. Sun, M. Yu, X. Liu, B. Yang, D. Liu, S. Liu, W. Cao and M.N.R Ashfold, Nanoscale 6, 10746-51, (2014).
Ultrathin aligned ZnO nanorod arrays grown by diffusive pulsed laser deposition, G.M. Fuge, T.M.S. Holmes and M.N.R. Ashfold, Chem. Phys. Lett.479, 125-7 (2009).
