Defect distribution and compositional variations in a light-emitting material revealed by CL imaging and spectrum imaging

By David Stowe and Simon Galloway, Gatan

The increasing use of opto-electronic materials and devices is core technology to our modern world. Emitting, amplifying and sensing devices enable high-speed telecommunications whether through fibre optic, mobile or wireless.

There are also growing fields like optical data storage, energy efficient solid-state lighting and photovoltaics. In order to develop and manufacture devices with novel performance and suitable lifetimes, it is important to understand the material science governing the opto-electrical behaviour. Included in this, is an understanding of problems associated with scaling from laboratory prototypes to high yield, large-scale manufacturing. Characterisation plays a pivotal role at all stages in this process, especially when it comes to identifying the role defects play in limiting the performance or lifetime. Thus, a technique which enables spectroscopic characterisation of opto-electronic properties at high spatial resolution is extremely powerful. Cathodoluminescence (CL) is such a technique and Gatan’s MonoCL3 system remains at the forefront of this disciplin

Do you see PPM level differences in mineral chemistry

By Paul Mainwaring, Gatan

Cathodoluminescence (CL) occurs when an electron beam strikes a material and causes it to luminesce. During the process of electron bombardment, electron-hole pairs are created and their radiative recombinations give rise to the observed emission in an attempt to relax the increased energy imparted to the specimen

This emission is commonly observed in the light optical system of the electron microprobe during the chemical analysis of minerals but rarely ever seen in the SEM due to the lack of suitable optics. Although not always seen or noticed due to low emission intensity, the CL signal can be put to important uses in the chemical characterization of minerals. The example below suggests that CL is an indispensable tool for the understanding of the subtle compositional variations that cannot quickly and easily be imaged in any other way in an electron microprobe or SEM.

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Preparation of a cross-sectional semiconductor IC device sample for SEM observations

By Prashanth Prasad, Gatan

Obtaining high resolution data from a large volume of brain tissue in an automated and reliable process

By Christel Genoud, Gatan

Morphometry is an important and growing discipline within neuroscience. Theoretical models of neuronal circuits require 3D information over extensive volumes. Current models are based on real data obtained from serial sectioning brain tissue and subsequent reconstruction to show components present, for example synapses, axons, dendrites. Realistic and meaningful analysis requires morphometric analysis at the ultrastructural level over large sample volumes. Large volumes are required in order to be statistically relevant and usable for model building.

Electron microscopy is key to providing information at the ultrastructural level.

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Gain variation effects and correction in CCD cameras for TEM

By Bill Mollon, Gatan

As technology evolves, more and more people are taking the course towards replacing conventional film with the newer CCD cameras created for TEM applications. With this progression towards CCD camera use on TEM’s, is the need to fully understand all the parameters that can affect the final image quality. Gain normalization is a common procedure to correct for any artificial defects from the CCD camera and has greatly improved the image quality. However, little attention has been paid to the dependence of the gain reference image on TEM magnification.

The purpose of this article is to first demonstrate such dependence and show how it can affect the image quality. Then we show a new patented procedure to make gain reference image TEM magnification dependent.

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