phase-change materials (Ge Te Sb) 

transformation on (1,0) state--crystallization & amorphization 

1.Phase Change Materials PCM

• Group of semiconductors ( Ge, As, Te)
• Principle: Disordered amorphous phase 0 change to ordered crystalline phase 1

HDD and SSD -retain data for long time

DRAM ans SRAM - loss data when turn off

PCM- Storage class memory- inbetween the above 2

2.Switiching fast

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

• Higher melting point indicate strong bond strength
• Ecoh and COHP
• COHP- to find chemical stability of the system 

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

5. RESET

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