phase-change materials (Ge Te Sb)
transformation on (1,0) state--crystallization & amorphization
LASER -GMA H
Laser- based optical sensors
Laser principle: Absorption, spontaneous emission, and stimulated emission.
Ground state means - lowest possible energy.
When excited with addition of energy through photons the electron goes form ground state to and excited upper state.
Etot = Eel + Evib + Erot ( treat seperatly)
Eel due to electronic configration of electrons
Evib due to periodic displacment of atoms abt mean positions
Erot due to ratation of atoms abt common axis passing through center of mass
Seperation between Eel > Evib > Erot
Allowed transition is by planck's law
Wavlength in UV = Electronic transition occuring
LIGHT MATTER INTERACTION
Lines : Erot Bands: Evib System: Eelec
Lines: Single transition
Molecules with permanent dipole and can interact with microwave termed as microwave active (H2O, HCl )and those who does not have a permanent electric dipole are microwave inactive (N2, H2)
Erot = (1/2) IW2
Bands: Vibrations levels asscoiated with rotational levels.
Evib =( u+ 1/2) hw (h here is hcross=h/2*pi)
System : Transition between 2 electronic levels
Beer Lambert law: Ratio between intial intensity from Laser source to transmitted intensity by photodetector.
Quantitative way of applying absorbtion specta.
B= Rotational Constant = (28* 10^-40) / I
F(J)= BJ(J + 1) cm^-1
1.Power plant emissions (sensing gases)
2. Engine efficiency monitoring
3. Sensing benzene in environment
4. Ammonia sensor
1.Phase Change Materials PCM
HDD and SSD -retain data for long time
DRAM ans SRAM - loss data when turn off
PCM- Storage class memory- inbetween the above 2
amorphosrous = fast -picoseconds- upon exciting
Cryatallization- fast- nanoseconds
Upon heating for some nanoseconds amorphous phase can change into crystalline for PCM materials
3. Why GST is fast (GST- Germanium, antimony, Tellurium)
GST crystallises into cubic rocksalt phase
4. Improve writing speed
GST at high tempertsure of around 600K CYRSTALLINE phase fluctuate
From above 3 calculations it was found Sc2Te3 to be best system
So If Sc2Te3 is in a system with just 10% it could be good for nucleation
GST can withstand more heat upto 1200K without being changing into disordered state.
6 improve cycling endurance and stabilising
7. Prevent atomic migration.
Thickness of PCM is around several nanometers to 100nm
8 ageging tendency
ageing lead to lower energy
9 SET operations
10 To improve speed power consuption and cycling indurance