Graphene(field,effect(transistors( - - PowerPoint PPT Presentation

Graphene(field,effect(transistors(

A(realis4c(alterna4ve(to(Si(based( technology?( ( ( ( ( (

Talk(by(Niclas(Müller(

1(

2( Graphene(field,effect(transistors(

Pictures(from: (F.(Schwierz,(Nature(Nanotechnology(5,(2010(

((

1.(Introduc4on(and(Mo4va4on(

Important(proper4es(of(FET:(

(

• Gate(length(
• On/Off,ra4o(

((

• Transconductance,(carrier(mobility((

Proper4es(of(field,effect(transistor(and(market(development(

3( Graphene(field,effect(transistors(

Structure(of(the(talk(

• Discovery(of(graphene(

( (

• (Electronic(proper4es(of(graphene(

( ( (

• (Graphene(FETs(for(high(frequency(applica4ons(

( ( (

• (Graphene(FETs(for(digital(logic(devices(

4( Graphene(field,effect(transistors(

Pictures(from: (Boehm(et(al.,(Anorg.(Allg.(Chem.(316,(1962( ( (Boehm(et(al.,(Carbon(24,(1986( ( ((

2.(Discovery(of(graphene(

Reduc4on(of(graphene(oxide(by(Boehm(et(al.(in(1962(

• Graphite(oxide(is(hydropilic(and(forms((

monolyer(flakes(in(water(

• (Reduc4on(with(hydrazine(hydrate(to((((

((((((graphene(

5( Graphene(field,effect(transistors(

8Å( 1μm(

Pictures(from: (Novoselov(et(al.,(Science(306,(2004( ((((((((((( (Novoselov(et(al.,(Appl.(Phys.(Lea.(91,(2007(((

(

2.(Discovery(of(graphene(

Produc4on(of(graphene(by(micromechanical(cleavage(2004(

• Micromechanical(cleavage(of(graphene(

from(graphite(

• Iden4fica4on(of(some(flakes(as(

monolayer(

(

• Making(graphene(visible(by(naked(eye(
• n(Si+300nm(SiO2(

6( Graphene(field,effect(transistors(

2.(Discovery(of(graphene(

Electrical(field(effect(in(graphene(2004(

Pictures(from: (Novoselov(et(al.,(Science(306,(2004(

( ((

7( Graphene(field,effect(transistors(

H = −t (ai,σ

+ bj,σ i, j,σ

∑

+ bi,σ

+ aj,σ )

− # t (ai,σ

+ aj,σ i≠j,σ

∑

+ bi,σ

+ bj,σ )

Tight,binding(hamiltonian:( Derived(energy(bands:(

E(kx,ky) = ±t 3+ f (kx,ky) + ! t ⋅ f (kx,ky)

with(

f (kx,ky) = 2cos 3kya

( )

+ 4cos 3 2 kya = ! " # $ % &cos 3 2 kxa ! " # $ % &

Pictures(from:(Castro(Neto(et(al.,(Rev.(Mod.(Phys(81,(2009(

( ((

3.(Electronic(proper4es(of(graphene(

Bandstructure(and(ladce(

8( Graphene(field,effect(transistors(

Pictures(from:( (Castro(Neto(et(al.,(Rev.(Mod.(Phys.(81,(2009( ( (J.(Hicks,(E.H.(Corad,(MRS(Bulle4n(37,(2012((

((

• Approxima4on(at(K,point:(

E±( q) = ±vF  q

• Compare(with(photon(dispersion(

rela4on:(

E( q) = c  q

with(Fermi(velocity(independent(

• f(mass(and(energy(

( (vF = 3ta / 2 ≈106m / s ≈ c / 300

• Electrons(have(to(be(described(

as(massless(rela4vis4c(par4cles( by(Dirac(equa4on(

(((

3.(Electronic(proper4es(of(graphene(

Bandstructure(and(charge,carrier(veloci4es(

9( Graphene(field,effect(transistors(

Pictures(from:( (Castro(Neto(et(al.,(Rev.(Mod.(Phys.(81,(2009( ( ((

((

• Approxima4on(at(K,point:(

E±( q) = ±vF  q

with(Fermi(velocity(independent(

• f(mass(and(energy(

( (vF = 3ta / 2 ≈106m / s ≈ c / 300

3.(Electronic(proper4es(of(graphene(

Bandstructure(and(charge,carrier(veloci4es(

• Density(of(states:(

10( Graphene(field,effect(transistors(

Pictures(from:( (Bolo4n(et(al.,(Solid(State(Comm.(146,(2008(

((

3.(Electronic(proper4es(of(graphene(

Charge,carrier(mobility(

• Charge,carrier(mobility(μ(=(How(quickly(can(charge,carrier(move,(when(pulled(

by(an(electric(field(E(

vD = µ ⋅ E

• Determine(carrier(density(by(

applying(magne4c(field:(

n(VG) = B e⋅ ρ26(VG, B)

• Measure(carrier(mobility:(

µ(n) = 1 neρ23

• Highest(value(measured:(

µmax = 230.000cm2 /Vs

11( Graphene(field,effect(transistors(

3.(Electronic(proper4es(of(graphene(

Charge,carrier(mobility(

• Charge,carrier(mobility(μ(=(How(quickly(can(charge,carrier(move,(when(pulled(

by(an(electric(field(E(

vD = µ ⋅ E

• Determine(carrier(density(by(

applying(magne4c(field:(

• Measure(carrier(mobility:(

µ(n) = 1 neρ23

• Highest(value(measured:(

µmax = 230.000cm2 /Vs

Other(materials:(

• 2DEG(
• Carbon(Nanotubes((
• IrSb(
• GaAs(
• Ge(
• Si(

100.000cm2 /Vs 3.000.000cm2 /Vs 78.000cm2 /Vs 9.200cm2 /Vs 3.900cm2 /Vs

1.400cm2 /Vs

n(VG) = B e⋅ ρ26(VG, B)

12( Graphene(field,effect(transistors(

Pictures(from:( (P.(Avouris(and(F.(Xia,(MRS(Bulle4n(37,(2012(

((

3.(GFETs(for(RF,applica4ons(

Characteris4cs(of(graphene(field,effect(transistors((GFETs)(

13( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Top,gated(GFETs(

14( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Top,gated(GFETs(

15( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Top,gated(GFETs(

16( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Problems:(Metal,graphene(contacts(

Effect(of(palladium(contacts(on(GFET( characteris4cs,(because(of(p,doping.( ( ! Forma4on(of(p,n,p(structure(in( graphene( ! Effect(stronger(with(decreasing(channel( length((

Pictures(from:( (P.(Avouris(and(F.(Xia,(MRS(Bulle4n(37,(2012(

((

17( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Problems:(Gate(dielectrics(and(substrate(

• Very(thin,(highly,dielectric(film(needed(
• Graphene(is(chemically(inert(and(

hydrophobic(

! insula4ng(materials(form(poor,

( (quality,(nonuniform(and(leaky(( ( (films((e.g.(SiO2,(HfO2,(Al2O3)(

( ! charges(trapped(at(graphene, (

( (insulator(interface(

( ! drama4c(decrease(of(carrier( (

( (mobility(

18( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

Problems:(Gate(dielectrics(and(substrate(

(

• Suitable(insulators:(Diamond,like(carbon,(

( ( ( ( ((h,BN(

! Carrier(mobili4es((for(h,BN)(

((

( (! Scaaering(mean(free(path((

( ((for(h,BN)(

>100.000cm2 /Vs

≅1µm

19( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

State(of(the(art(

Pictures(from:( (P.(Avouris(and(F.(Xia,(MRS(Bulle4n(37,(2012(

((

20( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

State(of(the(art(

Picture(adapted(from:(( (F.(Schwierz,(Nature(Nanotech,( ( ( (nology(5,(2010((

((

21( Graphene(field,effect(transistors(

3.(GFETs(for(RF,applica4ons(

State(of(the(art(

Pictures(from:(( (F.(Schwierz,(Nature(Nanotechnology(5,(2010( ( (L.(Liao(and(X.(Duan,(Materials(Today(15,(2012((

((

22( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Opening(a(Band(gap:(AB,stacked(Bilayer(Graphene(

Pictures(from:(( (D.(Reddy(et(al.,(J.(Phys.:( ( (Appl.(Phys(D.(44,(2011(

((

• Band(gap,(which(depends(on(electric(

field(

(

• Parabolic(bandstructure((

(! No(more(rela4vis4c(behavior(of(( ( (electrons( (! Lower(carrier(mobili4es((

23( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Opening(a(Band(gap:(AB,stacked(Bilayer(Graphene(

Pictures(from:(( (Zhang(et(al.,(ACS(Nano(9,(2011((

• Molecules(are(used(to(dope(graphene(and(generate(electrical(field(
• On,Off(ra4os(up(to(70(

24( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Opening(a(Band(gap:(Graphene(nanoribbons(

Pictures(from:(( (L.P.(Biro(et(al.,(Nanoscale(4,(2012((

Armchair(GNR( Zigzag(GNR(

semiconduc4ng( metallic(

25( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Opening(a(Band(gap:(Graphene(nanoribbons(

Pictures(from:(( (L.P.(Biro(et(al.,(Nanoscale(4,(2012( ( (Huang(et(al.,(Mat.(Science(and(Eng.(70,(2010((

Armchair(GNR( ZigZag(GNR(

(Band(gap(inversly(propor4onal(( ((((( (to(width(of(GNR(

26( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Produc4on(methods(

Pictures(from:(( (Kosynkin(et(al.,(Nature(Leaers(458,(2009((

Unzipping(of(carbon(nanotubes(

27( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Produc4on(methods(

Pictures(from:((L.(Jiao(et(al.,(Nature(Nanotechnology(5,(2010((

Unzipping(of(carbon(nanotubes(

• Width(of(10,20nm(
• Carrier(mobility(of(

(

• Nanoribbon(yield(of(2%((

1.500cm2 /Vs

28( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Produc4on(methods(

Pictures(from:((J.(Bai(et(al.,(Nano(Leaers(9,(2009((

31nm( 23nm( 14nm( 9nm( 6nm(

Nanowire(mask(

• Silicon(nanowires(as(mask(
• Width(below(10nm(
• Controllable(diameter(

29( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Produc4on(methods(

Pictures(from:((Li(et(al.,(Science(319,(2008((

• Chemically(derived(
• On/Off,ra4os(up(

(((((to(10.000.000(

• Width(below(10nm(
• Bandgaps(up(to(((

(((((400meV(

(

• Carrier(mobili4es((

((((((of((

(

• All(GNR(produced(

((((((have(band,gap(

200cm2 /Vs

30( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Nanomeshes(

Pictures(from:((J.(Bai(et(al.,(Nature(Nanotechnology(5,(2010((

31( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Nanomeshes(

Pictures(from:((J.(Bai(et(al.,(Nature(Nanotechnology(5,(2010((

100nm( 100nm( 500nm(

32( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Nanomeshes(

Pictures(from:((J.(Bai(et(al.,(Nature(Nanotechnology(5,(2010((

• Driving(currents(100(4mes(higher(than(in(

graphene(nanoribbons((

• On/Off,ra4os(>(100(
• Neck(width(down(to(5nm(

500nm(

33( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Towards(industrial(applica4ons((

Pictures(from:((Sprinkle((et(al.,(Nature(Nanotechnology((5,(2010((

Epitaxial(growth(of(graphene(nanoribbons(on(SiC(

Etching(a(nanoscale(step( Hea4ng(to(1200°C( Further(hea4ng(to(1450°C( Fabrica4on(of(Electrodes(

• Carrier(mobilites(

up(to((

• On/Off,ra4os(of(

10(

• Width(of(40nm(

2700cm2 /Vs

34( Graphene(field,effect(transistors(

4.(GFETs(for(digital(logic(devices(

Graphene(nanoribbons(–(Towards(industrial(applica4ons((

Pictures(from:(M.(Ruan(et(al.,(MRS(Bulle4n(37,(2012((

10.000(transis, tors(fabricated(

• n(4mm(x(6mm((

chip(

35( Graphene(field,effect(transistors(

5.(Conclusion(and(outlook(

• Near(future(applica4ons(can(be(expected(in(RF,applica4ons(
• Main(advantages(of(GFETs:(thinness,(possible(short(gate(length((
• Latest(ITRS(roadmap(strongly(recommends(research(into(graphene(

Pictures(from: (F.(Schwierz,(Nature(Nanotechnology(5,(2010(

((