Atom Probe Tomography of a-Axis GaN Nanowires: Analysis of Nonstoichiometric Evaporation Behavior
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- 作者：James R. Riley ; Rodrigo A. Bernal ; Qiming Li ; Horacio D. Espinosa ; George T. Wang ; Lincoln J. Lauhon
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：May 22, 2012
- 年：2012
- 卷：6
- 期：5
- 页码：3898-3906
- 全文大小：497K
- 年卷期：v.6,no.5(May 22, 2012)
- ISSN：1936-086X
文摘
GaN nanowires oriented along the nonpolar a-axis were analyzed using pulsed laser atom probe tomography (APT). Stoichiometric mass spectra were achieved by optimizing the temperature, applied dc voltage, and laser pulse energy. Local variations in the measured stoichiometry were observed and correlated with facet polarity using scanning electron microscopy. Fewer N atoms were detected from nonpolar and Ga-polar surfaces due to uncorrelated evaporation of N2 ions following N adatom diffusion. The observed differences in Ga and N ion evaporation behaviors are considered in detail to understand the influence of intrinsic materials characteristics on the reliability of atom probe tomography analysis. We find that while reliable analysis of III鈥揘 alloys is possible, the standard APT procedure of empirically adjusting analysis conditions to obtain stoichiometric detection of Ga and N is not necessarily the best approach for this materials system.