Material for memory and display system h

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1. S J B Institute of Technology Bangalore
PARAMESH.M.S
Asst Professor
Dept. of Chemistry
SJBIT, Bangalore –560
060
Sri Adichunchanagiri Shikshana Trust (R)
SJB INSTITUTE OF TECHNOLOGY
#67, BGS Health & Education City,
Dr. Vishnuvardhana Road, Kengeri, Bengaluru –560060.
KARNATAKA, INDIA.
MODULE 2: Materials for
Memory and Display Systems

2. Introduction
Objectives
Conclusion
References
Contents :

3. Definitionofmemorydevice:
Amemorydeviceisapieceofhardware
usedtostoredata.Mostelectronicdevicessuch
ascomputers,mobilephones,tablets,etcallhave
astoragedevicethatstoresdataand/orprograms.
BasicConceptsofElectronicMemoryAn
electronicmemorydeviceisaformof
semiconductorstoragewhichisfastinresponse
andcompactinsize.Asemiconductorstorage
systemwhichcanbereadandwrittenwhen
coupledwithacentralprocessingunit(CPU,a
processor).Thebasicgoalofamemorydeviceis
toprovideameansforstoringandaccessing
binarydigitaldatasequencesof“1’s”and“0’s”,

4. Electronicmemorydeviceconsistsof
1.Twoelectrodes
2.Switchinglayerbetweentwoelectrodes
ThelayerisoperatedfromHighResistance
State(HRS)toLowResistanceState(LRS)
underanexternalelectricvoltage.TheHRS
canberegardedas“0”bitindata
storage.(OFF)TheswitchingfromHRStothe
LowResistanceState(LRS)isequivalentto
“0”to“1”binaryconversion.(ON)Ifasingle
material(usedinmakingmemorydevice)
providesmorethantworesistancestates
(bistable),thestoragecapacityofasingle
memoryincreasesexponentially.

5. Conventional electronic memory Conventional
electronic memory devices are silicon-based and data
storage depends on the amount of charges available in the
memory cell. “Higher the charges available, greater would be
the data storage”.
Modern Memory is the requirement in UHDDS (Ultra High-
Density Data Storage) electronics and artificial intelligent
technologies.
Modern memory Organic/polymer electronic memory, which
uses various electrical conductivity states such as ON and OFF
in response to an applied electric field.
1.High storage capacity
2.Fast data transfer rate
3.Short access time
4.Low power consumption
5.Neuromorphic computing(use of artificial neurons)

6. Classification of Electrical
(electronic) Memory Devices:
1. Transistor-Type Electronic Memory
2. Capacitor-Type Electronic Memory
3. Resistor-Type Electronic Memory
4. Charge Transfer Effects

7. 1.Transistor-TypeElectronicMemory:
Transistorsaremadefromsilicon,asemiconductor.
Itisconvertedtop-typeandn-typesemiconductorby
dopingtrivalentandpentavalentimpurities.
Transistorsaremadeusingp-typeandn-type
semiconductor.Atransistorisaminiatureelectronic
componentthatcanworkeitherasanamplifierora
switch.
Acomputermemorychipconsistsofbillionsof
transistors,eachtransistorisworkingasaswitch,
whichcanbeswitchedONorOFF.Eachtransistorcan
beintwodifferentstatesandstoretwodifferent
numbers,ZEROandONE.Sincechipismadeof
billionsofsuchtransistorsandcanstorebillionsof
ZerosandOnes,andalmosteverynumberandletter
canbestored.

8. 2.Capacitor-TypeElectronicMemory:
Acapacitorconsistsoftwometalplateswhichare
capableofstoringanelectriccharge.Itisusedtostoredata.Itis
likeabatterythatholdsdatabasedonenergy.Ifthecapacitoris
charged,itholdsthebinarynumeral,”1”andholds“0’whenthe
cellisdischarged.Iftheparallelplatesofacapacitorareseparated
bydielectriclayer,chargesdissipateslowlyandmemorywouldbe
volatile.
Ontheotherhand,ifthemediumbetweentheelectrodesis
ferroelectricinnature,canmaintainpermanentelectric
polarizationthatcanberepeatedlyswitchedbetweentwostable
states(bistable)byanexternalelectricfield.Thus,memorybased
onferroelectriccapacitors(FeRAM)isnon-volatilememory.

9. 3.Resistor-TypeElectronicMemory:
Memorydevicescontainingswitchableresistivematerialsare
classifiedasresistor-typememory,orresistiverandomaccess
memory(RRAM).Resistor-typeelectronicmemoryusuallyhasa
simplestructure,havingametal-insulator-metalstructuregenerally
referredtoasMIMstructure.Thestructurecomprisesofan
insulatinglayer(I)sandwichedbetweenthetwometal(M)
electrodesandsupportedonasubstrate(glass,siliconwafer,plastic
ormetalfoil).Initially,thedeviceisunderhighresistancestateor
“OFF”andlogically“0”state,whenresistancechangedorunder
externalappliedfieldchangestolowresistancestateor“ON”
logicalvalue“1”.

10. 4.ChargeTransferEffects:
Achargetransfer(CT)complexis
definedasanelectrondonor–acceptor
(D–A)complex,characterizedbyan
electronictransitiontoanexcitedstatein
whichapartialtransferofchargeoccurs
fromthedonormoietytotheacceptor
moiety.TheconductivityofaCT
complexisdependentontheionic
bindingbetweentheD–Acomponents.

11. Charge Transfer Effects :

12. AdditionalInformation:
Chargetransferischaracterizedbyan
electronictransitiontoanexcitedstateinwhichapartial
transferofchargeoccursfromthedonormoietytothe
acceptormoiety.Ifthedonorischaracterizedbysmall
sizeandlowionizationpotential,astronglyionicsalt
formsandacompletetransferofcharge(orwiththeCT
degreevalue,δ>0.7)occursfromthedonortothe
acceptor,makingtheionicsaltinsulating.Whenthe
donorisverylargeandhasahighionizationpotential,a
neutralmolecularsolid(δ<0.4)forms,whichisalso
insulating.Ifthedonorhasintermediatesizeand
ionizationpotential,ittendstoformaweaklyionicsalt
withtheacceptor,whichpossessesincompleteCT
(0.4<δ<0.7)andthusispotentiallyconductive.

13. Classificationofelectronicmemory
basedonstoragetypeofthedevice:
Electronicmemorycanbedividedintotwo
primarycategories:
volatileandnon-volatilememory.Non-
volatilememory:
Non-volatilememory(NVM)ornon-volatile
storageisatypeofmemorythatcanretainstored
informationevenafterpowerisremoved.
VolatileMemory:Volatilememoryisatypeof
memorythatmaintainsitsdataonlywhilethe
deviceispowered.Ifthepowerisinterruptedfor
anyreason,thedataislost.Furtheritisdivided
asshownbelow:

14. Further it is divided as shown below:

15. ROM:ReadOnlyMemory
•ROMisanon-volatilememory.
•InformationstoredinROMispermanent.
•Informationandprogramsstoredonit,wecanonly
read.
•InformationandprogramsarestoredonROMin
binaryformat.
•Itisusedinthestart-upprocessofthecomputer.
WORM(WriteOnceReadManytimes):
Describesadatastoragedeviceinwhichinformation
oncewritten,cannotbemodified.
Thiswriteprotectionaffordstheassurancethatthedata
cannotbetamperedwithonceitiswrittentothe
device,excludingthepossibilityofdatalossfrom
humanerror,computerbugs,ormalware.

16. EPROM(Erasableprogrammableread-only
memory):
•EPROMalsocalledEROM,isatypeofPROMbut
itcanbereprogrammed.
•ThedatastoredinEPROM canbeerasedand
reprogrammedagainbyultravioletlight.
•Reprogrammedofitislimited.
•BeforetheeraofEEPROMandflashmemory,EPROMwas
usedinmicrocontrollers.
Hybridmemoriescanbereadandwrittenasdesired,like
RAM,butmaintaintheircontentswithoutelectricalpower,just
likeROM.ItisaNon-Volatilememory.
Flashisanelectronicnon-volatilecomputermemorystorage
mediumthatcanbeelectricallyerasedandreprogrammed.
Flashmemoryisanon-volatilememorychipusedforstorage
andfortransferringdatabetweenapersonalcomputer(PC)and
digitaldevices.

17. EEPROM(Electrically erasable programmable
read-only memory)
1.Electronically erasable programmable
read only memory, is a standalone
memory storage device such as a USB
drive.
2.Itisatypeofdatamemorydeviceusing
anelectronicdevicetoeraseorwrite
digitaldata.

18. RAM:RandomAccessMemory:
Itisacomputer'sshort-termmemory.Itcanbe
readandchangedinanyorder,typicallyusedto
storeworkingdataandmachinecode.
RAMsconsistofferromagneticparticles
embeddedinapolymermatrixhavingahigh
dielectricconstant.Oneofthemostcommon
RAMsiscalledironballpaint,whichcontains
tinymetal-coatedspheressuspendedinanepoxy-
basedpaint.Thespheresarecoatedwithferrite
orcarbonyliron.

19. DRAM (Dynamic random access memory) :
•It is a type of semiconductor memory that is typically
used for the data or program code needed by a
computer processor to function.
•All DRAM chips manufactured to date use capacitors
containing electrodes made of doped silicon or
polysilicon and dielectric films of silicon dioxide
and/or silicon nitride.
SRAM (Static Random Access Memory) :
•It is a type of RAM that holds data in a static form,
that is, as long as the memory has power.
•SRAM: It is made up of metal-oxide-semiconductor
field-effect transistors (MOSFETs).

20. Therearemanyproblemswithtraditional
methodsofdatastorage,
•Conventionalmemorydevicesareimplementedon
semiconductor-basedintegratedcircuits,suchas
transistorsandcapacitors.
•Inordertoachievegreaterdensityofdatastorageand
fasteraccesstoinformation,morecomponentsare
deliberatelypackedontoasinglechip.
•Silicon-basedsemiconductordevicesbecomeless
stablebelow22nm,andthereliabilitytostoreand
readindividualbitsofinformationwillbe
substantiallyreducedbysevere“cross-talk”issues.
•Powerconsumptionandunwantedheat
generationarealsoofincreasingconcern.

21. •Siliconbasedmemorydevicessuchas
transistors,capacitorandresistorsstored
datainthebinaryform“ZERO”and“ONE”,which
requiresdecodingofthedata.
•Thenewtechnologiesarebasedonelectrical
bistabilityofmaterialsarisingfromchangesincertain
intrinsicproperties,suchasmagnetism,polarity,phase,
conformationandconductivity,inresponsetothe
appliedelectricfield.
•Theefficiencyofmemorystructuresismeasuredin
termsofstoragecapacityandthespeedoffunctioning.
Therefore,Organicmemorydevices(OMDs)provide
anidealsolution,inbeinginexpensive,andatthesame
timepromisinghighperformance.

22. Definition:
Organicelectronicmemorydevicestores
databasedondifferentelectricalconductivitystates
(ONandOFFstates)inresponsetoanappliedelectric
field.
Theadvantagesoforganicandpolymerelectronic
memoryinclude,
•goodprocessability,
•moleculardesignthroughchemicalsynthesis,
•Simpledevicestructure,
•miniaturizeddimensions,
•low-cost,
•low-poweroperation,
•multiplestateproperties,and
•largecapacityfordatastorage.

23. ThankYouOneAndAll
AnyQuestions?