Monitoring the formation of nanowires by line-of-sight quadrupole mass spectrometry: a comprehensive description of the temporal evolution of GaN nanowire ensembles

Line-of-sight quadrupole mass spectrometry (QMS) is a unique non-destructive technique that enables the measurement of the desorption of adatoms during the growth of films as well as nanostructures in a high-vacuum environment. In this work, we use QMS to investigate the temporal evolution of GaN nanowire ensembles during plasma-assisted molecular beam epitaxy.

Figure 1: (Left) Schematic diagram of the QMS system. (Right) Growth diagram depicting the dependence of the average delay time for nanowire formation (in minutes) on the growth temperature and the impinging Ga flux for a given active N flux of 10.5 nm/min. The delay time is displayed as a contour plot with a logarithmic scale.

We find that the temporal evolution of GaN nanowire ensembles is well described by a double logistic function. In contrast to existing growth models, this simple equation provides an empirical but comprehensive description of the entire growth process. We use this double logistic function for analyzing the formation rate of GaN nanowire ensembles prepared under a wide variety of growth conditions. This analysis allows us to construct a growth diagram in which we depict the average delay time that precedes nanowire formation as a function of the growth parameters. This diagram can be used as a guide to control the growth and properties of GaN nanowire ensembles as well as to envision novel growth approaches.

 

 

 

1 Autor S. Fernández-Garrido , J. K. Zettler , L. Geelhaar , O. Brandt
Titel

Monitoring the formation of nanowires by line-of-sight quadrupole mass spectrometry: a comprehensive description of the temporal evolution of GaN nanowire ensembles

Source Nano Lett. , 15 , 1930 ( 2015 )
DOI : 10.1021/nl504778s | 2684 Cite : Bibtex RIS
S. Fernández-Garrido, J. K. Zettler, L. Geelhaar, and O. Brandt