Quantitative counting of Zn and O atoms by atomic resolution off-axis and in-line electron holography

Abstract

Quantitative atom counting of Zn and O atoms in zinc oxide(ZnO)epitaxial thin film by three different routes; reconstruction of phase from side and central band of atomic resolution off-axis and in-line electron holography are presented. It is found that the reconstructed phase from both side and central band and corresponding atom number for both Zn (Z = 30) and O (Z = 8) atom columns are in close agreementalong with the systematic increase in thickness for thinner sample area.However, complete disagreement is observed for thethicker sample area. On the other hand,the reconstructed phase obtained via in-line holography showsno systematic change with thickness.Phase detection limits and atomic model used to count the atoms are discussed.Corresponding author e-mail address: 2 I.

Direct methods applied to phase retrieval in high resolution transmission electron microscopy

“…The reconstructed phase numbers calculated by equation (9) for Zn and O atoms in ZnO are in good agreement with the earlier report using atomic resolution off-axis electron holography [6]. However, the reconstruction from the HRTEM through focus series using the Gerchberg-Saxton scheme as implemented in MacTempas package did not yield expected variation in phase with sample thickness unlike the application of equation (9) yield systematic variation in phase with sample thickness [6,17]. For thicker sample, channeling theory and diffraction imaging based reconstructions are being utilized at present [20,21,27].…”

“…For more details on associated twin image wave functions and applicability of equation (8), see section 4. The results based on the existing schemes can be found in [6,17] and do not show any systematic trends with the sample thickness.…”

“…HRTEM images were recorded in an aberration corrected FEI TITAN 3TM 80-300 kV transmission electron microscope operating at 300 kV at optimum settings of C S and defocus [36,37]. ZnO epitaxial thin film was grown homoepitaxially on a (0001) ZnO substrate by pulsed laser deposition (PLD) following a specific growth procedure as described in [6,38].…”

“…Phase ( ) f is the fundamental quantity in quantitative high-resolution transmission electron interferometry [1][2][3][4][5][6]. The change in phase ( ) f D of the probe electron wave after interacting with the object potential leads to the formation of specific intensity patterns in the respective image and diffraction planes.…”