Dharmpal Singh BSE412a 12240

Lab Report-7

Scanning Electron Microscopy1. Aim: To image samples obtained by scanning electron microscopy and use gold

coating.

2. Principle: Surface characterization is done to understand the behaviour of various materials. One of the techniques as is scanning electron microscopy (SEM). Its capability to provide magnification is 250 times than that of light microscopy. SEM uses a high energy electron beam in or der to create variety of signals on the surface of the specimen. These signals are responsible for having various type of information including chemical information as well. Ideally this process is carried out in vacuum. It can be carried out in an open and high pressure environment as well.These signals are then detected by a detector, mainly in the form of Secondary Electrons (SE). Secondary electrons are the beams reflected by elastic scattering and are generated by the interaction of the beam with the surface of the specimen used. Along with SE’s there are other types of signals mainly consisting of back scattered electrons (BSE), characteristic X-rays and transmitted electrons. Intensity of BSE’s strongly varies with atomic number of the material used. As we use high energy electrons beam in the SEM, the sample needs to be conducting because if it isn’t conducting, the electrons will start accumulating on the surface of the material and in turn damage it.

3. Materials/Instruments Used: i. Scanning Electron Microscope

ii. Sputter Coateriii. Samples

4. Method: The specimens were put in the sputter coater and then coated. In case of scanning electron microscopy, the specimens were put in the SEM, which then followed by starting of vacuum pump and then the samples were scanned at different scales. The pressure maintained in the vacuum pump was 5 MPa.

5. Results: Images for the specimens were obtained at different magnifications. Nano Fibers:

Dharmpal Singh BSE412a 12240

30000X 10000X

Hydrogels:

Dharmpal Singh BSE412a 12240

Micro-Particles:

Nano-Particles:

6. Conclusion: Various images were clearly obtained by using SEM. 7. Discussion: The clarity of the images totally depends on the resolution. In some cases

the resolution wasn’t good enough to get good images. In the images of fibers, different fibers can easily be seen, while in cases of micro and nano-particles, different particles can be seen. Two sections of hydrogel were imaged under SEM, longitudinal and transverse.

8. Reference: i. https://en.wikipedia.org/wiki/Scanning_electron_microscope

ii. http://www.nanoscience.com/products/sem/technology-overview/

Dharmpal Singh BSE412a 12240