The Effects of Osmium Coating and Chemical Cleaning on SEM Images of Dispenser Cathode Surface Porosity

2006 ◽  
Author(s):  
J.O. Tarter ◽  
S. Roberts
Keyword(s):  
Cathode Surface ◽  
Surface Porosity ◽  
Chemical Cleaning ◽  
Sem Images ◽  
Dispenser Cathode

Design, Fabrication and Characterization of n-Si Columnar Structures for Solar Cell Applications

2020 ◽  
Vol 10 (1) ◽  
pp. 74-79 ◽  
Author(s):  
Aysegul Develioglu ◽  
Levent Trabzon ◽  
Yunus Alphan
Keyword(s):  
Thin Film ◽  
Contact Angle ◽  
Solar Cells ◽  
Glancing Angle Deposition ◽  
Surface Porosity ◽  
Sem Images ◽  
Vis Spectroscopy ◽  
Glancing Angle ◽  
Evaporation Technique ◽  
Angle Deposition

Background: Glancing Angle Deposition (GLAD) provides oblique deposition and substrate motion to engineer thin film microstructures in three dimensions on nano scale. Using this technique zigzag, chevrons, staircase, post, helical and various type of nanostructures including 3-D multilayers can be obtained from various metals with controllable morphologies. The aim of the study is to increase surface porosity and junction using GLAD method area for thin film solar cells and therefore to increase p-n junction area. This provides efficient charge separation and strong light absorption. Methods: Glancing angle deposition using e-beam evaporation technique has been employed to create 3- D silicon nano-structures on the surface. Al and Ag contact layers were deposited by thermal evaporation technique. Hole-conductor polymer PEDOT: PSS was spin coated onto n type silicon thin film. Reflectance spectra were measured using UV-VIS spectroscopy. Scanning electron microscopy was used to image surface and cross-section with and without PEDOT: PSS. Also, transmission spectra of PEDOT: PSS was measured using UV-VIS spectroscopy. Surface wettability properties and contact angles of silicon samples were measured by contact angle measurement with water. Results: Columnar structures possess less reflection compared to the flat surface depending on surface porosity. This phenomenon shows that these structures can be used as anti-reflection coatings for solar cells and optical devices to decrease reflectivity and increase light harvesting with higher efficiency. Contact angle decreases when surface roughness increases therefore we can see that columnar structures are more hydrophilic compared to dense films. Flat silicon has 98° contact angle while columnar structures have 71° and 61°. PEDOT: PSS exhibits high transparency in the range from 200 to 1100 nm of wavelength of light, which resembles to solar radiation inside the atmosphere. Also, SEM images of the samples show that silicon columnar structures form better contact with PEDOT: PSS than flat surface. Conclusion: GLAD technique has been used to achieve homogenous rough surface by e-beam evaporation. Both cross-sectional and top-view SEM images show that columnar structures have higher porosity than flat surfaces. The response of UV-VIS spectroscopy shows that columnar structures have less reflection due to highly porous surface. With increasing incident flux angle, antireflection property of the surfaces was enhanced by surpassing the surface reflection. Due to the reduced hydrophobicity of porous structures, organic polymer can be distributed homogenously in between the columnar structures with increased p-n junction interface area. PEDOT: PSS is highly conductive, and it is highly transparent material in the range of the wavelength typically seen in the solar radiation. This makes it easier for light to reach to Si interface to generate electrons and holes. These results provide better understanding of Si- based heterojunction solar cells efficiency improvement with surface modification. This study also shows dependency of optical and electrical activity to surface geometry and surface porosity.

Estimation of dispenser cathode surface temperature of a practical potted heater cathode assembly

1993 ◽  
Vol 40 (10) ◽  
pp. 1855-1863 ◽  
Author(s):  
A. Sil ◽  
N.K. Samria ◽  
A. Chatterjee ◽  
D.S. Venkateswarlu
Keyword(s):  
Surface Temperature ◽  
Cathode Surface ◽  
Dispenser Cathode ◽  
Cathode Assembly

scholarly journals Long-term effects of various cleaning methods on polypropylene/ethylene copolymer retainer material

2019 ◽  
Vol 89 (3) ◽  
pp. 432-437 ◽  
Author(s):  
Emily Wible ◽  
Manika Agarwal ◽  
Sibel Altun ◽  
Tyler Ramir ◽  
Grace Viana ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Artificial Saliva ◽  
Flexural Modulus ◽  
Light Transmittance ◽  
Long Term Effects ◽  
Chemical Cleaning ◽  
Sem Images ◽  
Ethylene Copolymer ◽  
Cleaning Methods

ABSTRACT Objectives: To evaluate long-term light transmittance, surface roughness, and flexural modulus of polypropylene/ethylene copolymer retainer material after exposure to different cleaning methods. Materials and Methods: Standardized polypropylene/ethylene copolymer retainer specimens (n = 70, 50.8 mm × 12.7 mm × 1.0 mm) were subjected to seven chemical cleaning solutions: Invisalign cleaning crystals, Retainer Brite, Polident, Listerine mouthwash, 2.5% acetic acid, 0.6% NaClO, and 3% H2O2 for 6 months. The specimens were exposed to the different solutions twice a week for 15 minutes or according to manufacturer's instructions, then stored in artificial saliva at 37°C. Another group of specimens (n = 10) were brushed with a standardized toothbrushing machine for 2 minutes twice a week. At baseline and 6 months, light transmittance, surface roughness, and flexural modulus of the specimens were quantified using spectrophotometry, profilometry and three-point bend testing, respectively. Qualitative analysis was performed using a scanning electron microscope (SEM). Statistical analyses were performed at a significance level of .05. Results: The results showed that light transmittance decreased significantly from baseline for all cleaning methods at 6 months. For an individual method, no significant differences were observed between specimens at baseline and 6 months in surface roughness and flexural modulus. No discernible differences in surface features were observed on SEM images. Conclusions: The results indicate that different cleaning methods affect the long-term light transmittance of the studied polypropylene/ethylene copolymer retainer material. However, for an individual cleaning method, no significant differences were shown for surface roughness or flexural modulus values at 6-months compared to baseline.

Analysis of Contrast Reversal in SEM Images

1972 ◽  
Vol 30 ◽  
pp. 398-399
Author(s):  
M. D. Coutts ◽  
E. R. Levin
Keyword(s):  
Incident Beam ◽  
Normal Incidence ◽  
Beam Current ◽  
Secondary Emission ◽  
Image Contrast ◽  
Sem Images ◽  
Secondary Electrons ◽  
Image Position

On tilting samples in an SEM, the image contrast between two elements, x and y often decreases to zero at θε, which we call the no-contrast angle. At angles above θε the contrast is reversed, θ being the angle between the specimen normal and the incident beam. The available contrast between two elements, x and y, in the SEM can be defined as,(1)where ix and iy are the total number of reflected and secondary electrons, leaving x and y respectively. It can easily be shown that for the element x,(2)where ib is the beam current, isp the specimen absorbed current, δo the secondary emission at normal incidence, k is a constant, and m the reflected electron coefficient.

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