Electronics & Semiconductors

Bulky additives could make cheaper solar cells last longer

An insight into preventing perovskite semiconductors from degrading quickly, discovered at the University of Michigan, could help enable solar cells estimated to be two to four times cheaper than today's thin-film solar panels.

Engineering

New 3D printing method creates a steel-aluminum fusion hybrid

Steel and aluminum are key players in supporting economic growth, yet materials joining them remain unexplored due to their fusion zones' brittleness. A new 3D printing method's fix may be a step toward a steel-aluminum hybrid ...

Hardware

Detecting manipulations in microchips

Attackers have the ability not only to manipulate software, but also to tamper with the hardware. A team from Bochum is devising methods to detect such tampering.

Energy & Green Tech

Making materials for the next generation of electric car batteries

As drivers around the world switch to electric cars, new batteries that can store more energy, translating to longer driving distances before a car needs recharging, can't come soon enough. But researchers at NTNU have discovered ...

Scanning electron microscope

The scanning electron microscope (SEM) is a type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample's surface topography, composition and other properties such as electrical conductivity.

The types of signals produced by an SEM include secondary electrons, back scattered electrons (BSE), characteristic x-rays, light (cathodoluminescence), specimen current and transmitted electrons. These types of signal all require specialized detectors that are not usually all present on a single machine. The signals result from interactions of the electron beam with atoms at or near the surface of the sample. In the most common or standard detection mode, secondary electron imaging or SEI, the SEM can produce very high-resolution images of a sample surface, revealing details about 1 to 5 nm in size. Due to the way these images are created, SEM micrographs have a very large depth of field yielding a characteristic three-dimensional appearance useful for understanding the surface structure of a sample. This is exemplified by the micrograph of pollen shown to the right. A wide range of magnifications is possible, from about x 25 (about equivalent to that of a powerful hand-lens) to about x 250,000, about 250 times the magnification limit of the best light microscopes. Back-scattered electrons (BSE) are beam electrons that are reflected from the sample by elastic scattering. BSE are often used in analytical SEM along with the spectra made from the characteristic x-rays. Because the intensity of the BSE signal is strongly related to the atomic number (Z) of the specimen, BSE images can provide information about the distribution of different elements in the sample. For the same reason, BSE imaging can image colloidal gold immuno-labels of 5 or 10 nm diameter which would otherwise be difficult or impossible to detect in secondary electron images in biological specimens. Characteristic X-rays are emitted when the electron beam removes an inner shell electron from the sample, causing a higher energy electron to fill the shell and release energy. These characteristic x-rays are used to identify the composition and measure the abundance of elements in the sample.

This text uses material from Wikipedia, licensed under CC BY-SA