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SSPD_Chapter 1_Part 11_ Conclusion, describes the 1D,2D and 3D defects in crystals.

SSPD_Chapter 1_Part 11_Conclusion_Defects in Crystal structure

1.11.8. CRYSTAL DEFECTS- 1-D DEFECT, 2-D DEFECTS AND 3-D DEFECTS.

A regular array of atoms extending to infinity in all three dimensions is an ideal crystal. In real life , crystals are always surface bounded where we have dangling bonds and hence surface states. Therefore real crystals are never ideal. But apart from this non-ideality, we have externally introduced defects. This could be a missing atom, atoms out of place, irregular arrangement of atoms, irregularity in the spacing of the rows of atoms and the presence of impurities. These defects effect the electrical properties of the material and devices made out of these materials.

Point defects are the simplest category of defects. Vacancies, interstitial impurity atoms and substitutional impurity atoms comprise point defects. They are shown in Figure (1.63). Vacancies and interstitials occur in all crystals due to thermal excitation of 1~2 eV. As the ambient temperature increases the density of such point defects increases. By particle radiation such defects can be purposely introduced in a given sample for specific purposes such as decreasing the lifetime of the minority carriers. The lifetime of minority carriers can be changed from millisecond to pico-seconds. A relatively pure, single and defect-free crystal exhibits millisecond lifetime whereas with introduction of defects it falls. Particle radiation induced defects can kill the lifetime to as low as pico-seconds.

The controlled introduction of impurity dopents influence drift mobility, diffusion coefficient and lifetime. The dopents occupy either interstitial positions or substitutional positions.

Figure 1.63. Point defects in a crystal.(a)Vacancy, (b) Interstitial Donor Dopent (c) Substitutional Acceptor Dopent, (d) Interstitial Acceptor Dopent;

Line Defect(1-D defects) : Dislocations are line defects. These act as precipitate sites for metallic impurities. This degrades the performance of the device.

In edge defect, a line of atoms is not in proper position. This causes a permanent deformation in the crystal structure without the loss of a property called ductility. Metals have the maximum ductility because of the nature of metallic bond. We will discuss the nature of metallic bond in the next section. Edge Defect is illustrated in Figure 1.64.

In screw dislocation, a part of the crystal lattice is displaced with respect to the other part. The consequence of this displacement is that atomic layers spiral around this dislocation. Screw Defect is illustrated in Figure 1.65.

Plane Defects(2-D defects) : Solidification of a polycrystalline solid from the melt creates grain boundaries. When crystallographic plane of orientation abruptly changes there we have grain boundaries. Grain Boundaries are shown in Figure 1.66. Grain boundaries lower the mobility of the carriers. Anti-phase boundaries is 2D defect. This occurs in ordered alloy. Here the crystallographic plane direction is the same the layers are in opposite phase. Instead of layer order of ABABABAB…… it is arranged as ABABBABABAB……….Stack faults are also 2-D defect. They occur in a number of crystal structure. But they commonly occur in closed packed structure. Stacking fault is one or two layer interruption in the stacking sequence. Instead of ABCABCABCABC…….. arrangement as found in fcc structure we have ABCABABABC….. arrangements then we say that stacking fault has occurred.

Volume defects(3-D defects): Precipitates and voids are examples. Precipitates are reduced solubility of dopents at reduced temperature. Voids are shown in Figure 1.67

Figure 1.66. Grain Boundaries along with point defects and line defects.

Figure 1.67. Volume Defect such as void.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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