Report Materials Laboratory 1 Scanning Electron Microscopy.pdf

A vacuum is required when using an electron beam because electrons will quickly disperse or scatter due to collisions with other molecules.. This system consists of electromagnetic lense

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

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REPORT Materials Laboratory 1

SCANNING ELECTRON MICROSCOPY

Student: Hoang Trung Thang

Instructors: Hoang Van Vuong

Course

code:

MSE3317 - 738468

Hanoi, December 2023

I Introduction

1 A brief description of the principles of image formation in an SEM

1 Vacuum system A vacuum is required when using an electron beam because electrons will quickly disperse or scatter due to collisions with other molecules

2 Electron beam generation system This system is found at the top of the microscope column (Fig 1) This system generates the "illuminating" beam of electrons known as the primary (1o) electron beam

3 Electron beam manipulation system This system consists of electromagnetic lenses and coils located in the microscope column and control the size, shape, and position

of the electron beam on the specimen surface

4 Beam specimen interaction system This system involves the interaction of the electron beam with the specimen and the types of signals that can be detected

5 Detection system This system can consist of several different detectors, each sensitive to different energy / particle emissions that occur on the sample

6 Signal processing system This system is an electronic system that processes the signal generated by the detection system and allows additional electronic manipulation of the image

7 Display and recording system This system allows visualization of an electronic signal using a cathode ray tube and permits recording of the results using photographic or magnetic media

- Dip coating is a popular way of creating thin films for research purposes Uniform films can be applied onto flat or cylindrical substrates For industrial processes, spin coating is used more often

- The withdrawal speed, the solid content and the viscosity of the liquid define the thickness of coating

- The dip coating process can be separated into five stages:

 Immersion: The substrate is immersed in the solution of the coating material

at a constant speed (preferably jitter-free)

 Start-up: The substrate has remained inside the solution for a while and is starting to be pulled up

 Deposition: The thin layer deposits itself on the substrate while it is pulled up The withdrawing is carried out at a constant speed to avoid any jitters The speed determines the thickness of the coating (faster withdrawal gives thicker coating material)

 Drainage: Excess liquid will drain from the surface

- Evaporation: The solvent evaporates from the liquid, forming the thin layer For volatile solvents, such as alcohols, evaporation starts already during the deposition & drainage steps

1 Roll of coarse cloth

4 Liquid material

8 Excess liquid falls back

9 A coating remains on the fabric clot

II Experimental Produce

1 The SEM preparation

- Hydrothermal technology and chemical vapor deposition method (CVD) were used to prepare TiO2-base films on Ti substrate (10×10 mm ) 2

- Sodium hydroxide NaOH was dissolved in water corresponding to a Na+

concentration of about 5M

- The prepared Ti substrates were put in the NaOH solution with the concentration of 5M in the sample container and were then heated up to 250 C ino

12h

- After the hydrothermal process, the Ti samples were heated at 850 C in 2h foro

the CVD process

- After cooling in the furnace, the samples were cleaned by using an ultrasonic machine

- Ultrasonically clean (acetone, followed by an ethanol baths) and dry the samples; mount on standard SEM mounting stubs using carbon tape

- The TA will help the students mount their three different samples for SEM examination and imaging The TA will help load the samples and an Intel processor in the SEM and set up the initial operating conditions

- Finally, we will then use the SEM to explore the morphology and microstructure

of the samples and record images

2 Operating parameters of the SEM

- The SEM is an instrument that produces a largely magnified image

by using electrons instead of light to form an image

- A beam of electrons is produced at the top of the microscope by an electron gun The electron beam follows a vertical path through the microscope, which is held within a vacuum The beam travels through electromagnetic fields and lenses, which focus the beam down toward the sample Once the beam hits the sample, electrons and X-rays are ejected from the sample

- Detectors collect these X-rays, backscattered electrons, and secondary electrons and convert them into a signal that is sent to a screen similar to a television screen This produces the final image

III - Results and Discussion

 Accelerating Voltage: The accelerating voltage determines the energy of the electron beam Higher accelerating voltages increase the penetration depth of the electrons into the sample, allowing for better imaging of deeper features However, higher voltages can also cause increased sample damage and decreased resolution for surface details

 Working Distance: The working distance is the distance between the final lens

of the SEM and the sample surface It influences the depth of field and the magnification of the image A shorter working distance provides higher magnification but reduces the depth of field, limiting the sharpness of the image

 Beam Current: The beam current refers to the number of electrons in the beam per unit time Higher beam currents result in brighter images as more electrons interact with the sample surface However, high beam currents can also lead to increased charging effects and degradation of the sample

 Spot Size: The spot size refers to the size of the electron beam on the sample surface Smaller spot sizes provide higher resolution and sharper images However, smaller spot sizes may require higher beam currents, leading to increased charging effects and sample damage

 Imaging Mode: SEM offers various imaging modes, including secondary electron imaging (SEI) and backscattered electron imaging (BEI) SEI provides detailed surface topography information, while BEI can reveal compositional contrast Selecting the appropriate imaging mode depends on the specific sample and the information desired

 Detector Selection: Different detectors can be used to collect various signals emitted from the sample, such as secondary electrons, backscattered electrons, or characteristic X-rays The choice of detector affects the contrast, resolution, and information obtained in the images

 Vacuum Level: SEM operates under high vacuum conditions to minimize electron scattering and interactions with air molecules Maintaining a high vacuum level is essential for image clarity and resolution If the vacuum level

is insufficient, the electron beam may scatter, resulting in decreased image quality and reduced signal-to-noise ratio

3 A discussion of the morphology and microstructure of the samples

At the room temperature and magnification of 5,000, the size of particle exhibits large and short with non-uniformity Additionally, the particles tend to agglomerate and arrange in random orientations, resulting in cluster forming These clusters are found to be randomly ordered The presence of such irregularities in particle size and arrangement can have implications on the overall quality and performance of the material, and affect properties such as strength, conductivity, or reactivity Furthermore, checking out and optimization may be necessary to achieve a more uniform and desirable particle morphology

- There is a presence of high percentage of crystal, and the crystals sizes are similar

- The elements are distributed different amounts in each area, shown above 4 spectrums

- When we increase the temperature, the sample will change A more amorphous state will appear, and the phase of the sample is also changed

- In spectrum 1, 2, 3 and 4, XRD diagrams show the weight percent that the sample contains There are 5 elements, in order of Wt% from high to low: Ti, O, Na, C and Cl.Moreover, the table of each diagram illustrates detailed data of each element

- In spectrum 1, the Wt% of Ti, O, Na, and C have approximated values with 41.5%, 44.1%, 5.36%, and 9.08% respectively The weight percentage of crystalline phase

of Ti and O are both 0.42

- In spectrum 2, a similarity in portion of each element is shown The Wt% of Ti, O,

Na, and C have approximated value with 69.68%, 25.66%, 1.15%, and 3.51% respectively The weight percentage of crystalline phase of Ti and O are 0.33 and 0,31 respectively, lower than in spectrum 1

- In spectrum 3, the Wt% of Ti, O, Na, C and Cl have approximate values with 32.28%, 48.63%, 5.74%, 13.17% and 0.17% respectively The weight percentage

of crystalline phase of Ti and O are 0.33 & 0.38 respectively, nearly the same as shown in spectrum 2

- In spectrum 4, the Wt% of Ti, O, Na, and C have approximated values with 41.00%, 45.18%, 5.88%, 7.93% respectively The weight percentage of crystalline phase of Ti and O are 0.52 & 0.56 respectively, which are the highest values among 4 phases