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MICROSCOPY IMAGING AND SAMPLE PREPARATION
Scanning Electron Microscopy (SEM)
SEM magnifies and produces image of sample surface using a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample.
Unlike others, our SEM has the ability to work under low vacuum without affecting the image quality. It is the most significant advantages when come to inspect non-conductive samples.
Another variant of SEM, Field Emission Scanning Electron Microscope (FE-SEM) uses field emission electron gun that is a strong electron source coupled with smaller beam size than a typical SEM. FESEM can provide a clearer image and magnification of imaging up to 500K times. FE-SEM at Quasi-S is capable of performing high resolution imaging with very low accelerating voltages.
CZTS Thin Film Surface Morphology
Metal Cross Section
Scanning Electron Microscopy (SEM) analysis
Quasi-S is one of the leading experts in the Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) analysis. Our laboratory staffs have more than 10 years of experience with microscopy analysis especially in identifying failure mechanism and discontinuities:
- Fatigue
- Overload
- Ductile & Brittle Fractures
- Pitting Corrosion
- Stress Corrosion
- Crevice Corrosion
- Intergranular Fracture
- Hydrogen Embrittlement
- Intergranular Corrosion
- Erosion
- Microbiological Corrosion
- Galvanic Corrosion
Our laboratory experts in SEM can provide useful information related to the material and with the aid of EDX we are able to provide a semi-quantitative elemental analysis of the material. This EDX analysis method (surface analysis scan) is very useful to characterize the chemical composition of the foreign material (inclusions or discontinuity) found in the sample while observing it microscopically using SEM.
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Transmission Electron Microscopy (TEM)
TEM is another type of electron microscopy that uses a very energy of electron beam that transmitted through the sample to form an image. The sample needs to be ultrathin with less than 100 nm. TEM is capable of imaging a significantly higher resolution than SEM and can produce up to 1M times magnification.
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Energy-dispersive X-ray spectroscopy (EDX)
EDX is usually equipped together with electron microscopes and it’s an analytical technique used for the elemental composition analysis or characterization on sample. EDX detects and analyses X-ray generated from the interaction of the sample atom and the electron beam.
Application: elemental composition analysis, elemental composition mapping
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Atomic force microscopy (AFM)
AFM is a very high-resolution, high-sensitive type of scanning probe microscopy capable of quantifying surface roughness down to angstrom-scale. It can perform qualitative mapping/imaging of 2D and 3D surface topographic and quantifying the surface roughness, grain size, step height, and pitch.
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Mechanical Cross-Section
Cross-section preparation is one of the most effective ways in examining how a material is laminated or component is assembled and produced. From cross section, we can determine the different layers' interaction. And from close observations layer after layer we can easily zoom into the failure mechanism. Good cross-section preparation will not smear or alter the specimen. Therefore the skill and experience of the person preparing the sample is crucial and Quasi-S possessed the expertise in Cross-section sample preparation. Mechanical cross-section involves sample cutting, moulding, grinding, polishing and finishing.
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Ion Milling
Conventional mechanical polishing or cutting techniques on soft, composite materials apply significant lateral sheer forces to the sample and often result in cross-section surface artefacts such as scratches, smearing, wash-out of softer materials, delamination and other damage.
In contrast, ion beam sputtering is a stress-free physical process whereby atoms are ejected from a target material due to bombardment of the target by energized particles.
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Focused Ion Beam (FIB)
FIB is generally used in the semiconductor industry to make modification on semiconductor devices like IC and LED. It uses a sharp focused beam of gallium ions that can be operated at low beam currents for imaging or high beam currents for site specific sputtering and milling. Application: Cross section preparation, TEM lamella preparation, FIB circuit edit
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Sputter Coating
Sputter coating for SEM is the process of depositing an ultra-thin layer of electrically-conducting metal – such as gold (Au) or platinum (Pt), onto a non-conducting or poorly conducting specimen. Sputter coating prevents charging of the specimen, which would otherwise occur because of the accumulation of static electric fields. It also increases the number of secondary electrons that can be detected from the surface of the specimen in the SEM and therefore increases the signal to noise ratio. Sputtered layer for SEM typically has a thickness range of 2–20 nm.
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Biological Sample Preparation
SEM samples must be completely dry and free of any organic contaminants that may potentially outgas in a high vacuum environment. This poses a problem when dealing with biological samples which are largely composed of water. Chemical drying agent, Hexamethyldisilizane (HMDS) can be used for sample fixation to ensure the native structure of the organism is retained.
