Polarity determination by atomic location by channeling-enhanced microanalysis

Abstract

In this letter, an alternative approach to determine the polarity of GaN thin films based on the atomic location by channeling-enhanced microanalysis technique is described. Theoretical calculations provide a straightforward criterion for polarity determination that is a major advantage of this method. At the Bragg position, the thickness-averaged incident electron intensity, and hence, electron induced characteristic x-ray yield, is higher on the N plane than on the Ga if the g vector of the diffraction beam is parallel to the Ga–N bond direction, and vice versa. Experimental results support the theoretical predictions. The possible errors in the experiments are also discussed.

Polarity determination of ZnO thin films by electron holography

“…2 The polarity is closely related to the film quality such as surface morphology and electronic properties, 2,3 it is important to determine polarity of such a thin film. Many methods, such as energydispersive x-ray spectroscopy, 4 coaxial impact-collision ion scattering spectroscopy, 5 convergent beam electron diffraction, 6 high-resolution transmission electron microscopy ͑HRTEM͒, 7 and electron energy loss spectroscopy 2 have been developed for the polarity determination.…”

Polarity determination for GaN thin films by electron energy-loss spectroscopy

“…6 Recently, Jiang et al demonstrated the method using x-ray energy dispersion spectroscopy ͑EDS͒. 7 The polarity can be determined by comparison of two or more element-characteristic x-ray intensities, which will always enhance at one Bragg orientation, and diminish at the opposite. However, the count rate of characteristic x rays is very low because the fluorescence yield is very small.…”

“…The direction of the cation ͑Ga͒ to the anion ͑N͒ is defined as ͓0001͔ in the real space. [1][2][3][4]7 The EELS experimental studies were carried out using a Philips CM200 field emission gun TEM equipped with a Gatan image filtering system, operated at 200 kV. The energy resolution is about 1.0 eV according to the measured full width at half maximum of the zero-loss peak.…”

“…14 At the two-beam condition, the thickness-averaged electron distribution is localized near some special atomic planes, as a consequence of the interference between the Bloch waves. The thickness-averaged electron current intensity ͑TAECD͒ close to Bragg condition ḡ , without absorption, has been given as 7,15 I͑r ͒ϭ 1…”

“…Similar to the case in the x-ray EDS experiment, several experimental factors should be considered in the EELS experiment, such as the orientation of the sample deviated from the exact two-beam Bragg condition, beam convergence effects, and the effect of absorption. 7,16 Furthermore, the delocalization of inelastic scattering associated with the width of the interaction potential is an important factor, which may affect the determination of the polarity, especially when using a low energy-loss characteristic edge. The delocalization is represented by the impact parameter b of the incident electron.…”