Orbitals of valence band electrons form sigma bonds and by sharing of valence electrons by each atom, valence band is fulled for each atom? How do then look orbitals of the conduction electrons? Nice video!
A individual Silicon atom has 4 electrons in the valence level ( level 3 ). In the lattice they combine to form the hybrid orbitals with the covalent bond, that its the explanation of the video, BUT they continue having 4xN electrons in the valence level with N the number of atoms in the crystal. Moreover, if you solve the Schrödinger ecuation with 3s 3px 3py 3pz orbitals where are placed 4 electrons (out of 8 that could be place in a sp orbitals) , you will get 4 (orbitals) x 2 (due to spin) = 8 bands, the first 4 full with 4xN electrons, then a GAP, and then another 4 bands empty in So, is the valence band fulled for each atom? If the temperature is 0 K, the electrons are not excited and stay in their energy levels (in the valence band, if we have a crystal), BUT exciting them, they can jump to a higher energy level leaving holes in the valence band. In the real space, in the case of silicon and due to the covalent bond, the electron is jumping in the same hybrid orbital (if you only consider sp orbitals) but to an external region of less probability because is occupied with an electron of the nearest atom, so, considering only sp orbitals the current is originated due to the jumping of the electrons in the sp hybrid orbitals with the covalent bonds. If you give more excitation energy to the electrons they can jump to more external orbitals like d orbitals (in where they are more free) and so on... Its important to remark that look of the orbital is a representation of the propability in where the electron could be localized, so for an H atom the orbitals have the same shape than Si, the difference is that H only has an electron in 1s orbital and Si has electrons in all the orbitals that are shown in the video. en.wikipedia.org/wiki/Atomic_orbital
Simple IV group elements obeys molecular orbital theory From the molecular orbital theory : No. Of atomic orbitals involved in bonding =no of molecular orbitals And No of molecular orbitals (always) =bonding orbitals +antibonding orbitals . Bonding orbitals =antibonding orbitals.... Energy of antibonding orbitals is always >either of the atomic orbitals Energy of bonding orbitals < either of the atomic orbitals.. Here.... Each silicon atom undergoes hybridisation and forms 4 ,sp³(3s, 3px, 3py, 3pz) hybrid orbitals which are equivalent in energy... And here our actual discussion starts....! Each hybridised silicon atom forms 4 covalent bonds with the other neighbouring (4)si atoms Here No of atomic orbitals involved =8[4 from one silicon atom +4 from neighboring silicon atom ] No. of bonding orbitals =4 No .of antibonding orbitals =4 All the electrons involved in covalent bond formation occupies bonding orbitals (4)and the Antibonding orbitals (4)which are at higher energy level are vacant In the semiconductor material: Let us consider there are :N such atoms Each atom has 4 hybridised orbitals with 4 electrons (unpaired) So there are total 4N electrons in semiconductor material. And All such N atoms forms the covalent bonds... So from the molecular orbital theory there are 8N atomic orbitals 4N bonding orbitals 4N antibonding orbitals are there in a semiconductor material All the 4N electrons occupies bonding orbitals and And All the Antibonding orbitals(4N) which are at higher energy level are vacant ....... This 4N antibonding orbitals which are vacant forms the conduction band ... And the 4N bonding orbitals which are filled forms the valance band... As energy of antibonding orbitals >energy of bonding orbitals This energy difference between them is called forbidden energy gap which is about 1.11ev.. Hope u will understand this.... ....
@@sindhupriyaa5718 i didnt get to think through everything that you wrote, but the type of orbital, weather it is bonding or antibonding affects the material nechanical properties mainly, i would guess. For us electronics engineers its inly important that we see a good dense conduction band, from whaterver orbital type.
This webinar helps me a lot to introduce silicon bonding and doping n-type, p-type for Si solar cell. That you so much
Orbitals of valence band electrons form sigma bonds and by sharing of valence electrons by each atom, valence band is fulled for each atom? How do then look orbitals of the conduction electrons? Nice video!
A individual Silicon atom has 4 electrons in the valence level ( level 3 ). In the lattice they combine to form the hybrid orbitals with the covalent bond, that its the explanation of the video, BUT they continue having 4xN electrons in the valence level with N the number of atoms in the crystal. Moreover, if you solve the Schrödinger ecuation with 3s 3px 3py 3pz orbitals where are placed 4 electrons (out of 8 that could be place in a sp orbitals) , you will get 4 (orbitals) x 2 (due to spin) = 8 bands, the first 4 full with 4xN electrons, then a GAP, and then another 4 bands empty in So, is the valence band fulled for each atom? If the temperature is 0 K, the electrons are not excited and stay in their energy levels (in the valence band, if we have a crystal), BUT exciting them, they can jump to a higher energy level leaving holes in the valence band. In the real space, in the case of silicon and due to the covalent bond, the electron is jumping in the same hybrid orbital (if you only consider sp orbitals) but to an external region of less probability because is occupied with an electron of the nearest atom, so, considering only sp orbitals the current is originated due to the jumping of the electrons in the sp hybrid orbitals with the covalent bonds. If you give more excitation energy to the electrons they can jump to more external orbitals like d orbitals (in where they are more free) and so on... Its important to remark that look of the orbital is a representation of the propability in where the electron could be localized, so for an H atom the orbitals have the same shape than Si, the difference is that H only has an electron in 1s orbital and Si has electrons in all the orbitals that are shown in the video.
en.wikipedia.org/wiki/Atomic_orbital
Simple IV group elements obeys molecular orbital theory
From the molecular orbital theory :
No. Of atomic orbitals involved in bonding =no of molecular orbitals
And
No of molecular orbitals (always) =bonding orbitals +antibonding orbitals .
Bonding orbitals =antibonding orbitals....
Energy of antibonding orbitals is always >either of the atomic orbitals
Energy of bonding orbitals < either of the atomic orbitals..
Here....
Each silicon atom undergoes hybridisation and forms 4 ,sp³(3s, 3px, 3py, 3pz) hybrid orbitals which are equivalent in energy...
And here our actual discussion starts....!
Each hybridised silicon atom forms 4 covalent bonds with the other neighbouring (4)si atoms
Here
No of atomic orbitals involved =8[4 from one silicon atom +4 from neighboring silicon atom ]
No. of bonding orbitals =4
No .of antibonding orbitals =4
All the electrons involved in covalent bond formation occupies bonding orbitals (4)and the
Antibonding orbitals (4)which are at higher energy level are vacant
In the semiconductor material:
Let us consider there are :N such atoms
Each atom has 4 hybridised orbitals with 4 electrons (unpaired)
So there are total 4N electrons in semiconductor material.
And
All such N atoms forms the covalent bonds... So from the molecular orbital theory there are
8N atomic orbitals
4N bonding orbitals
4N antibonding orbitals are there in a semiconductor material
All the 4N electrons occupies bonding orbitals and
And
All the Antibonding orbitals(4N) which are at higher energy level are vacant .......
This 4N antibonding orbitals which are vacant forms the conduction band ...
And the
4N bonding orbitals which are filled forms the valance band...
As energy of antibonding orbitals >energy of bonding orbitals
This energy difference between them is called forbidden energy gap which is about 1.11ev..
Hope u will understand this.... ....
@@sindhupriyaa5718 i didnt get to think through everything that you wrote, but the type of orbital, weather it is bonding or antibonding affects the material nechanical properties mainly, i would guess. For us electronics engineers its inly important that we see a good dense conduction band, from whaterver orbital type.
Hi. May I know... how about metal's energy state, and energy band? Do they differ from semiconductor?
Would we get these sp3 orbitals when plugging the potential function of periodic silicon lattice into the Srodingers equation?
7:35 Yep