black phosphorus field effect transistors: passivation by...
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Black Phosphorus Field EffectTransistors: Passivation By Oxidation, and the Role of Anisotropy in Magnetotransport
Electrical and Computer Engineering, Physics
Tomasz Szkopek
231st ECS Meeting, 1 June 2017
New Orleans
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layered materials
C (graphite) P (black-P) MoS2 (transition
metal dichalcogenide)
MgB2
Bi2Se3
(sesquichalcogenid
e)
GaSe
(group III
monochalcogenide)
YBa2Cu3O7-x
(high-Tc cuprate)KAl2(AlSi3O10)(OH)2
(mica)
HgI2(transition metal
halide)
BN (white
graphite)
2
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C (graphite) P (black-P) MoS2 (transition
metal dichalcogenide)
MgB2
Bi2Se3
(sesquichalcogenid
e)
GaSe
(group III
monochalcogenide)
YBa2Cu3O7-x
(high-Tc cuprate)KAl2(AlSi3O10)(OH)2
(mica)
HgI2(transition metal
halide)
BN (white
graphite)
layered materials
3
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black phosphorus (bP)1914: Bridgman produces first bP
1953: Keyes studies bP as a
semiconductor
1968: Berman & Brandt; Witting & Mattias
observe superconductivity at high
pressure
1970’s - 1980’s: burst of activity in Japan
on electronic properties, Raman,
cyclotron resonance
2014: ultra-thin bP FETs reported by
Yuanbo Zhang (Fudan) and Peide Ye
(Purdue)bulk band gap = 0.3 eV
monolayer band gap ≈ 1.2
eV
A. Morita, “Semiconducting Black Phosphorus”, Appl. Phys. A39, 227 (1986). 4
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Fengnian Xia…, Nature Comm.
2014, Nature Comm. 2015.
bP anisotropy
armchair (x)
S. Narita, et al. J. Phys. Soc. Jpn.
52, 3544 (1983)
mx my mz
electron 0.083 1.027 0.128
hole 0.076 0.648 0.280
cyclotron effective mass
5
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bP photo-oxidation
Rapid bP photo-oxidation with combination of O2, H2O and
light
A. Favron …. R. Martel, Nature Materials,
2015.
20s exposure to ambient air + light
6
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outline
• oxidation for top-gated field effect transistors
• weak-localization & magnetorsistance and
anisotropy
7
manuscript in preparation
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oxidation for passivation and
thinning
microscop
y
Jiajie Pei, Xin Gai, … B. Luther Davies, Yurei Liu, Nature Comm., 2015.
PLoxidation
formationPL efficiency is preserved. Can oxidation be
used for gate dielectrics?
8
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bP FET fabrication
bulk bP source:
>99.9% purity
exfoliation & processing in glove
box
O2, H2O < 1ppm
e-beam lithography, Ti/Au
contacts
oxidation: 200 mTorr, 300 W RF,
1-3 minutes
e-beam lithography, Ti/Au top
gates
9
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etch rate by oxidation
oxidation: 10sccm O2, 200 mTorr, 300 W RF
etch rate: 0.10 nm/s or ~0.5 bP layers/s
10
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XPS + TEM
124 126 128 130 132 134 136 138 140 142 1440
0.5
1.0
1.5
2.0
Binding Energy (eV)
Cou
nt
10
4/s
P2p1/2
P2p3/2 P2p3/2
P2O
5P
oxidation of bulk bP crystal
XPS: elemental P and P2O5
present
oxidation of bP flake on SiO2/Si
TEM: amorphous layer (< 6nm
thick), interfacial roughness with
bP11
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field effect
top gate modulation
bottom gate modulation
12
I D
S(μ
A)
I D
S(μ
A)
I D
S(n
A)
I D
S(n
A)
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field effect mobility
13
μF
ET
(cm
2/V
s)
μF
ET
(cm
2/V
s)
I D
S(μ
A)
μF
ET
(cm
2/V
s)
I D
S(n
A)
top gate modulation
peak FET mobility:
90cm2/Vs
bottom gate modulation
peak FET mobility:
60cm2/Vs
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mobility limiting mechanisms
remote impurities surface roughness
scattering
+++
−
++ + +++ ++ + +
+
impurities
+++
−
++ +
V. Tayari et al., Phys. Rev. Applied 5, 064004 (2016)14
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future: split gate transistors
M.A. Topinka, et al., Science 289,
2323 (2000).
GaAs/AlGaAs quantum point contacts bP split-gate
structures
15
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outline
• oxidation for top-gated field effect transistors
• weak-localization & magnetorsistance and
anisotropy
16
N. Hemsworth, V. Tayari, F. Telesio, S. Xiang, S. Roddaro, M. Caporali,
A. Ienco, M. Serrano-Ruiz, M. Peruzzini, G. Gervais, T. Szkopek, and
S. Heun, Dephasing in strongly anisotropic black phosphorus, Phys.
Rev. B 94, 245404 (2016).
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anisotropy : Raman spectroscopy
Source
Drain
armchair (x)
ac
zz
armchair (x)
zigzag
(y)
17
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magnetoresistance
3
4
5
6
7
89
10
R2
P (
k)
35302520151050
B (T)
-50
-62.5
-75
-100-87.5
Vg=-37.5 V
(a)
4
5
67
1
2
3
Rx
x (
k)
35302520151050
B (T)
Vg=-27 V
-50
-62.5
-37.5
-75
-87.5 -100
(c)(c)
V. Tayari et al., Two dimensional magnetotransport in a
naked black phosphorus quantum well, Nature Comm. 2015.
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weak localization
Source
Drain
1
2
3
c)
4
b)
Source
Drain
PMMA
MMA
SiO2
Si
d)
10 m 10 m
19
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weak localization – fit with theory
20
∆σ B( ) = − e2
2π 2hΨ 1
2+
B0
B
− Ψ 1
2+
Bϕ
B
Ψ(x) = digamma function
S. Hikami, A I. Larkin, and Y. Nagaoka,
Prog. of Theor. Phys. 63, 707 (1980).
0
φ
B
Φ0
0= Dτ
0elastic scattering length:
inelastic scattering length: ϕ = Dτϕ
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localization & anisotropy
21
kx
ky
kz
kx
ky
kx
3D 2D 1D
ϕ ∝T −1/2
τϕ = T −1
Electron-electron scattering in a diffusive 2D conductor:
(quasi-1D)
(quasi-1D)
ϕ ∝T −1/3
τϕ = T −2/3
Electron-electron scattering in a diffusive 1D conductor:
Altshuler, Khmelnitzkii, Larkin, Lee, PRB (1980).Abrahams, Anderson, Lee, and Ramakrishnan, PRB (1981).
Appenzeller, Martel, Avouris, Stahl, Hunger, Lengeler, PRB (2001).Natelson, Willett, West, and Pfeiffer, PRL (2001).
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future: pnictogens
P :
puckered
honeycomb
As, Sb, Bi :
buckled
honeycomb
N
P
As
Sb
Bi
V
ban
d
overl
ap
sp
in o
rbit
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the team
Stefan
Heun
Pisa
Guillaume
GervaisMcGill
Vahid
Tayari
Nick
Hemsworth
Francesca
Telesio
Will
Dickerson
IbrahimFakih
TomaszSzkopek
McGill
MaurizioPeruzzini
Firenze
23
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thank you
24