h-BN has potential as an ideal dielectric material for 2D electronics. As a gate dielectric, h-BN provides improved carrier mobility and resists dielectric breakdown at high electric fields. When used as a substrate, h-BN enhances graphene conductivity and mobility while improving reliability by facilitating better heat dissipation than conventional dielectrics like SiO2. Overall, h-BN shows promise as an ubiquitous dielectric that can fulfill critical roles in 2D heterostructures and devices.

1. Hexagonal Boron Nitride: Ubiquitous Layered
Dielectric for Two-Dimensional Electronics
Nikhil Jain
Thesis Committee Members:
Prof. Bin Yu (Research Advisor)
Prof. Carl Ventrice Jr.
Prof. Vincent LaBella
Prof. Ernest Levine
Prof. Sergey Rumyantsev (RPI)

2. WWW.SUNYCNSE.COM
 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
2

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
3

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A Paradigm Shift
New Material Platform
“Ubiquitous” Electronics
 Ultra-thin materials
 Self-limited processing
 Ultimate scalability
 Hetero-integration
 Flexible, soft, transparent
 Open, connected “Things”
Silicon Platform
Micro/Nano Electronics
 Bulk materials
 Low scalability
 Stiff, hard, brittle
 Externally powered
 Packed, isolated “chips”
4

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What are 2D Layered Materials?
(Courtesy: Y. Cui, Stanford Univ.)
Materials where individual layers of covalently bonded
atoms/molecules are held together by van der Waals forces
5

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Graphene
Molybdenum Disulfide
2D Semi-Metal
3-atom-thick monolayer
Gallium Selenide
4-atom-thick monolayer 5-atom-thick monolayer
Bismuth Selenide
Hexagonal boron nitride
2D Insulator
2D Semiconductors
Classification of 2D Materials
based on electronic structure
6

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2004 Extraction of graphene by Andre Geim and Konstantin
Novoselov using scotch tape method
1937 R. E. Peierls and L. D. Landau suggest that strictly 2D
crystals could not exist
1962 Hanns-Peter Boehm coins the terms graphene
1980s Theoretical studies on graphene confirm massless Dirac
equation & anomalous Hall effect
2005
Geim and Novoselov exhibit free-standing 2D crystals
of boron nitride, several transition metal
dichalcogenides, and complex oxides
2D Materials: Brief History
1947 Wallace calculates the band structure of single-layer
graphite
7

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2D Materials – Extraction Methods
The crystalline quality and correspondingly the electronic properties rely
on the method used to extract the 2D material nanosheet under study.
Micromechanical exfoliation Liquid-phase
or
chemical exfoliation
Chemical vapor deposition
K. S. Novoselov et al, Phys. Scr., 2012
Image Source: http://www.azonano.com
Image Source: http://emps.exeter.ac.uk/
8

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Why Graphene?
The electrons in the pz
orbital hybridize to give
Π and Π* bands
 Momentum confined to
two dimensions
 Zero-gap semiconductor
 Two sets of 3 Dirac points
 Fermi energy at Dirac
Point
 Cone like linear dispersion
relation within 1eV of
Dirac point
 Zero effective mass of
charge carriers in the
region
 Fermi velocity, vF ≈ 106 m/s
Dirac Points
9
D. R. Cooper et al, International
Scholarly Research Notices 2012

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 Intrinsic advantages
 Superior electrical conduction
(µ ~ 20,000 cm2/Vs: 20X of
silicon
 Excellent thermal conduction
(~5.3x103 W/m-K: 10X of
copper)
 High mechanical strength
(Young’s modulus: 0.5 TPa)
 3-5% light absorption
(monolayer)
Graphene: Key Properties
TEM
Optical ImageLattice Structure
AFM
10

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Electrical Analysis
 Charge carrier density, n =
ε0
ε 𝑉𝑔
𝑡 𝑒
ε0ε: Permittivity of SiO2
e: Electron charge
t: SiO2 thickness
 Resistivity, 𝜌 =
𝑊
𝐿
.
𝑉
𝐼
 Mobility, µ =
1
𝑒𝑛ρ
 Alternately, field-effect mobility is given
by:
µ =
1
𝐶
.
𝑑σ
𝑑𝑉 𝑔
C =
𝑊.𝐿
𝑡
. ε0ε (Gate Capacitance)
In this work, the term mobility refers to
field-effect mobility.
At Vg = 0, n should vanish but
minimum conductivity is
introduced by thermally
generated carriers and
electrostatic spatial
inhomogeneity.
11

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Graphene:
One-atom-thick sheet with no “bulk”, but all surfaces
Behavior is extremely sensitive to its interface with
neighboring materials like:
 Supporting substrate
 Top surface (ambient environment)
The “Real Significance”
12

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Carrier mobility ~ 200,000 cm2/V.s for suspended graphene.
– Actual values: 1000 ~ 3000 cm2/V.s on SiO2 substrate
Graphene/Dielectric Interface
Graphene electrical conduction is largely impacted by
interface with dielectrics.
Images Courtesy: Enrico Rossi,
CMTC, University of Maryland
Spatial inhomogeneity increases ON current and scattering sites decrease the OFF
current.
13

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Joule-heating Induced Breakdown
Carrier scattering mechanisms increase resistivity in
graphene.
 Impurity and defect scattering – Interface effect
 Longitudinal acoustic (LA) phonon scattering – Intrinsic effect
 Surface polar phonon (SPP) scattering – Substrate effect
Voltag
e
Current Temperatur
eJoule Heating
I2R
Resistivit
y
Causes
Breakdown
LA and SPP scattering increases with
temperature.
Images Courtesy:
H.-S. P. Wong, Stanford University
14
Graphene
Breakdown creates
a gap

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h-BN: An Ideal 2D Dielectric
Hexagonal Boron Nitride
 High crystal quality (negligible defect density)
 Atomically smooth surface
 Free of surface state
 High-energy surface polar phonons
 Thermal conductivity: ~20 W/m-K (20X of SiO2)
Image Courtesy: C Casiraghi
15

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Problem Statement
 While 2D material-based heterostructures can be
immensely useful for next generation electronics, 2D
materials are extremely sensitive to their immediate
environment.
 SiO2 and other dielectrics currently used in the fab
make a highly invasive interface with 2D materials.
 Pristine properties of graphene can be seen in
suspended orientations but it is not feasible to make
chips using structures suspended in vacuum.
Can h-BN fulfill the role of an ideal dielectric neighbor to graphene for the
purpose of making on-chip components?
16

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Research Goals
 Develop effective processes to prepare 2D material-
based functional heterostructures
 Demonstrate prototypes of applications: field-effect
transistors (FETs) and on-chip Interconnects using
graphene/h-BN heterostructures
 Study the role of h-BN as a non-invasive dielectric
neighbor for graphene
 Explore basic physical/electrical behavior of interest
from the performance and reliability standpoint
17

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
18

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2D Based New 3D Solids
Rational Stacking-By-Design
A. K. Geim, Nature, 2013
Selective assembly of 2D materials can lead to innovative device
design
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Heterostructure Formation
2D heterostructures: building
elements in future electronics
ACVD over
Bex
ACVD stacked
over
BCVD
ACVD grown over
over BCVD/ex
In situ CVD
growth of A/B
• Subscript “Ex” signifies exfoliated material
• Subscript CVD signifies material growth by chemical vapor deposition
20

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CVD Graphene Growth
Step 1:
Ramp up to 1000C with Ar (80 sccm) + H2 (5
sccm)
Step 2:
Anneal the Cu strip at 1000C (Same gas flow)
Step 3:
Graphene growth in CH4 (30 sccm) + H2 (5 sscm)
Step 4:
Cool down in Ar (80 sccm) + H2 (5 sccm)
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 Layer by Layer (LbL) fabrication is efficiently used for emerging 2D layered
structures.
 Large-area assembly using CVD grown graphene monolayer is possible.
CVD graphene growth
Monolayer transferring
Multilayer stacking
Assembly of CVD Graphene
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** CAB – Cellulose Acetate Butyrate
Assembly of Exfoliated h-BN
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Summary
Facile processes to make 2D heterostructures have
been developed.
 CVD growth of graphene and transfer to any target
substrate has been demonstrated.
 Assembly of exfoliated materials to target substrate has
been demonstrated with multiple methods.
 Necessary as long as CVD growth methods for other materials
are still being developed.
 Layer-by-layer stacking of nanosheets to create ternary
(or thicker) heterostructures has been shown.
 With controlled precision on where the third layer is assembled.
24

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
25

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Hexagonal Boron Nitride
 Single-crystalline
 Atomically smooth surface
 Free of surface state
 High-energy surface phonons
 Thermal conductivity: ~20 W/m-K (20X
of SiO2)
Silicon Dioxide
 Amorphous
 Surface roughness
 Rich in trapped charges
 Low-energy surface phonons
 Thermal conductivity: ~1.04 W/m-K
Graphene
h-BN
(lattice mismatch ~ 1.6%)
h-BN: Substrate for Graphene
Image Courtesy: Jarillo-Herrero Group,
Quantum Nanoelectronics, MIT
26

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Graphene On h-BN (GOBON)
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Electrical Performance of GOBON
Conductivity and mobility improvement is observed in
GOBON when compared with graphene (CVD or exfoliated)
on SiO2.
 Resistivity (at VG = 0V) drops by approximately 19x in GOBON as compared with
that on SiO2.
 At the carrier density of 1×1012 cm-2, carrier mobility in GOBON is improved by
about 17x compared with CVD graphene on SiO2. N. Jain et al, IEEE Electron Device
Letters, 33 (7), 2012 28

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Reliability Enhancement in GOBON
Due to improved thermal conductivity of h-BN, the permissible
current and voltage before permanent breakdown in graphene
are enhanced.
PBD = JBD (VBD – JBDRC)
 ~ 7X increased power density @ breakdown
 Thermal conductivity: ~20 W/m-K): ~20 times that in SiO2 (1.04 W/m-K)
 Prevent Joule heat built up in graphene
where,
JBD = Current density at
breakdown
VBD = Voltage at
breakdown
RC = Contact resistance
N. Jain et al, IEEE Electron Device Letters, 33 (7),
2012
29

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Electrical Annealing Effect
Electrical annealing shifts the Dirac point in graphene on SiO2,
but this change is avoided in GOBON due to less interfacial
trap charges
G/h-BN
G/SiO2
T. Yu, Applied Physics Letters 2011, 98, 243105.
N. Jain et al, IEEE Electron Device Letters, 33 (7), 2012
30

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Summary
h-BN has been shown to be an excellent substrate
for graphene.
 Graphene resistivity on h-BN is found to be 19 times
lower than on SiO2 (the current standard substrate).
 There is a 17-fold improvement in graphene mobility
when placed on h-BN compared with SiO2.
 Improved heat dissipation through h-BN results in
higher values of current density and power density
required to cause Joule heating-induced breakdown in
graphene.
 The Dirac point in GOBON structures is stable under the
effect of electrical annealing. 31

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
32

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h-BN as Gate Dielectric
h-BN could also serve as gate dielectric
k = 3.9
EG = 5.97 eV
self-terminating surface
chemically inert
Key questions:
What is the dielectric behavior?
33

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Titanium Nitride (TiN) filled trenches are created in a Si/SiO2
wafer to act as a gate for GOBON FET
Buried Gate Structures: Fabrication
* This process is
done in the fab
34

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GOBON FET with h-BN as Gate
Insulator
* FET fabrication process is same as shown in previous section.
G/h-BN/TiN
35

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Performance of GOBON FETs
Carrier mobility of CVD graphene on h-BN (on TiN) is 1.4X higher than mechanically
exfoliated graphene on SiO2 at effective electric field of 2x105 V-cm-1
N. Jain et al. Carbon, 54, 396–402 (2013)
36

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Dielectric Strength of h-BN
 No dielectric breakdown up to very high electric field (15 MV/cm)
 Transition from insulating to leakage occurs at a voltage that is directly
proportional to h-BN multilayer thickness
N. Jain et al. Carbon, 54, 396–402 (2013)
h-BN is a robust dielectric which resists dielectric breakdown
at high electric fields.
37

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Summary
h-BN has been shown to be a robust gate
dielectric for FETs made with graphene.
 Graphene mobility is enhanced in GOBON FETs
compared with graphene FETs with SiO2 as gate
dielectric.
 As a gate dielectric, h-BN does not undergo dielectric
breakdown even under very high electric field of
15MV/cm.
 h-BN undergoes a reversible transition to a leaky
dielectric at high fields, which is dependent on layer
thickness.
38

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
39

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Need for graphene encapsulation
 Whatever be the substrate, environmental adsorbents reduce graphene conduction
 Adsorbent sites act as charge traps
 Encapsulation with traditional capping materials degrades graphene quality
 h-BN as a passivating layer conforms to graphene surface
40

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Fully Encapsulated Graphene
* CAB – Cellulose Acetate Butyrate 41

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Passivation Effect of Top h-BN
 Insensitive to environmental (ambient) impact
 R-V characteristics show no variation in air and in vacuum for
encapsulated device
 No variation in contact resistance between ambient and vacuum
N. Jain et al, Nanotechnology, 24, 355202 (2013)
42

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 67% increase in breakdown power
density compared to uncovered GOBON
devices due to increased heat
dissipation through both graphene
surfaces
 No reduction in carrier mobility
Electrical Behavior
N. Jain et al, Nanotechnology, 24, 355202 (2013)
43

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Summary
h-BN has been shown to be an effective passivation
layer for graphene devices.
 When passivated with h-BN, graphene performance
becomes insensitive to the measurement conditions
(ambient or vacuum).
 Graphene – Metal contact performance is improved.
 Higher current density and power density are needed to
cause breakdown in encapsulated graphene devices.
 The improvement is achieved without a compromise on
carrier mobility.
44

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
45

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Cu CNT Graphene
Max current density
(A/cm2)
~106 > 1x108 > 1x108
Melting Point (K) 1356 3800 (graphite) 3800 (graphite)
Tensile Strength (GPa) 0.22 22.2 23.5
Thermal Conductivity
(×103 W/m-K)
0.385
1.75
Hone, et al.
Phys. Rev. B 1999
3 - 5
Balandin, et al.
Nano Let., 2008
Temp. Coefficient of
Resistance (10-3 /K)
4
< 1.1
Kane, et al.
Europhys. Lett.,1998
-1.47
Shao et al.
Appl Phys. Lett.,
2008
Mean Free Path
@ room-T (nm)
40
> 1000
McEuen, et al.
Trans. Nano., 2002
~ 1000
Bolotin, et al.
Phys. Rev. Let. 2008
x102
x10
x25
x102
Graphene as a Conductor

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Towards “3-D Graphene”
 At small critical dimensions (width < 100 nm), ρGraphene < ρCu
 Small cross section in monolayer graphene limits conduction.
 Multilayer graphene has less sheet resistance than monolayer
graphene.
 Onset of inter-layer scattering of charge carriers in multi-layer
graphene doesn’t allow the sheet resistance to scale down as
expected 47

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Double-Layer Graphene (DLG):
Fabrication
DLG structure with h-BN between two monolayer graphene
sheets with direct metal contact with both graphene layers
48

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Massless Dirac Fermions in DLG
DFT simulation of the dispersion relation of the DLG structure
indicates that carriers are massless Dirac fermions
* DFT analysis was performed by our collaborators at University of Washington.
 Band splitting in
BLG
 Π and Π* bands
divide in four bands
due to interlayer
scattering
 Degeneracy is
restored in DLG
49

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Raman Spectra of Graphene
 Single 2D peak in monolayer graphene
 Due to coupling between layers, two or four peaks exist in 2D band (>2
layers)
1400 1600 1800 2000 2200 2400 2600 2800 3000
2D band
Normalizedintensity
Wavenumber (cm
-1
)
1layer 2layer 3layer
4layers 5layer Graphite
G band
More layer number - Intensity
ratio of G/2D increased
50
Freitag, M. Nat Phys, 2011, 7, 596–597

51. WWW.SUNYCNSE.COM
Raman Spectral Analysis for
Scattering Measurement
2D peak in the Raman spectrum of bilayer graphene is
composed of four components arising from the band split at
Dirac point.
 Reduced height of the
overall 2D peak
 Increase in IG/I2D
 Increase in FWHM2D
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Raman Spectral Analysis for
Scattering Measurement
Addition of graphene layers results in increase in IG/I2D and
FWHM2D.
 For stacked turbostratic graphene, addition of each layer results in
lesser increase than in exfoliated graphene, indicating reduced
scattering in stacked graphene
 Similar effect is seen in FWHM2D
52

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Raman Spectral Analysis
IG/I2D and FWHM2D in DLG is similar to monolayer
graphene (much lower than stacked or exfoliated BLG)
Introduction of h-BN as an intercalation layer in double-layer
graphene reduces interlayer carrier scattering.
53

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Electrical Characterization
Reduced interlayer scattering allows higher current in
DLG.
Current and conductivity in DLG ~ MLG > BLG
54

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Performance Enhancement
Mobility and breakdown current density in DLG show
enhancement.
 Carrier Mobility in DLG > MLG
 JBD in DLG > 2x JBD in BLG
55

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Reliability Improvement
Under extreme electrical stress, DLG resists breakdown more
than MLG and BLG.
 At an elevated temperature (150C) under the effect of a constant
voltage (10V), the DLG sample withstands a current density of ~ 475
mA/cm2
 The mean time to failure (MTTF) for DLG is ~ 75 and ~4000 times
higher than that for BLG and MLG systems
56

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Summary
h-BN has been shown to be an interposer layer that
prevents interlayer scattering from degrading the
performance of double-layer graphene.
 Increase in the IG/I2D ratio and FWHM2D have been shown
as indicators of interlayer scattering.
 Random-stacked (turbostratic) graphene shows lower
interlayer scattering than Bernal-stacked graphene.
 As an intercalation layer, h-BN removes interlayer
scattering resulting in ideal current scaling due to layer
stacking.
 Higher carrier mobility and resistance to breakdown at
extreme electrical stressing conditions are also observed in
DLG.
57

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 Introduction to 2D materials
 Graphene/h-BN heterostructures
 h-BN as an ubiquitous dielectric
 Substrate
 Gate dielectric
 Passivation layer
 Intercalation layer
 Conclusions and future directions
Outline of Presentation
58

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Conclusions
 h-BN has been explored as a multi-function dielectric for future 2D
material enabled electronics.
 Facile assembly/fabrication processes for 2D heterostructures have
been demonstrated.
 h-BN serves as excellent supporting substrate, largely preserving
“pristine” graphene electronic transport.
 h-BN is demonstrated as a highly robust gate dielectric (medium-k
value).
 Fully encapsulated 2D heterostructure (h-BN/graphene/h-BN)
provides passivation and enhancement of maximum power density
in graphene without compromising electrical conduction.
 As an intercalation layer between graphene layers, h-BN reduces
interlayer scattering and restores mobility to ‘monolayer-like’ value
while also making the structures more robust to stress.
59

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Future Directions
(1) Direct all-CVD growth process
 GOBON: Graphene growth on exfoliated h-BN
 BNOG: h-BN growth on CVD/exfoliated graphene
(2) Study of 2D heterostructure properties
(3) On-chip device, interconnect, circuit demonstration
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Future Directions
CVD growth of h-BN on copper
61

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Superlattice-like structures of graphene/h-BN
Future Directions
62

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Acknowledgments
Lab Members (Present and Past):
 Dr. Bhaskar Nagabhirava
 Dr. Tianhua Yu
 Dr. Tanesh Bansal
 Dr. Mariyappan Shanmugam
 Dr. Fan Yang
 Robin Jacobs-Gedrim
 Eui Sang Song
 Thibault Sohier
 Christopher Durcan
Our Collaborator:
 Prof. M. P. Anantram (Univ. of Washington,
Seattle)
CNSE CSR Team:
 Dr. Vidya Kaushik
 Dr. Prasanna Khare
 Megha Rao
63

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Journal Publications
1. N. Jain, M. Murphy, R. B. Jacobs-Gedrim, M. Shanmugam, F. Yang, E. S. Song, and B. Yu, “Electrical Conduction and Reliability in
Dual-Layered Graphene Heterostructure Interconnects,” IEEE Electro Device Letters, vol. 35, no. 12, 1311-1313 (2014).
2. R. B. Jacobs-Gedrim, M. Shanmugam, N. Jain, C. A. Durcan, M. T. Murphy, T. M. Murray, R. J. Matyi, R. L. Moore, and B. Yu,
“Extraordinary photoresponse in two-dimensional In2Se3 nanosheets,” ACS Nano, 8, 1, 514-521 (2014).
3. N. Jain, C. A. Durcan, R. B. Jacobs-Gedrim, Y. Xu, and B. Yu, “Graphene interconnects fully encapsulated in layered insulator
hexagonal boron nitride,” Nanotechnology, 24, 355202 (2013).
4. N. Jain, T. Bansal, C. A. Durcan, Y. Xu, and B. Yu, “Monolayer Graphene/Hexagonal Boron Nitride Heterostructure,” Carbon, 54, 396–
402 (2013).
5. T. Bansal, C. A. Durcan, N. Jain, R. B. Jacobs-Gedrim, Y. Xu, and B. Yu, “Synthesis of Few-to-Monolayer Graphene on Rutile Titanium
Dioxide,” Carbon, 55, 168-175 (2013).
6. M. Shanmugam, N. Jain, R. B. Jacobs-Gedrim, Y. Xu, and B. Yu, “Layered insulator hexagonal boron nitride for surface passivation in
quantum dot solar cell,” Applied Physics Letters, 103, 243904 (2013).
7. R. B. Jacobs-Gedrim, C. A. Durcan, N. Jain, and B. Yu, “Chemical Assembly and Electrical Characteristics of Surface-Rich Topological
Insulator Bi2Se3 Nanoplates and Nanoribbons,” Applied Physics Letters, 101, 143103 (2012).
8. E. Kim, N. Jain, R. Jacobs-Gedrim, Y. Xu, and B. Yu, “Exploring Carrier Transport Phenomena in CVD-Assembled Graphene FET on
Hexagonal Boron Nitride,” Nanotechnology, 23, 125706 (2012).
9. N. Jain, T. Bansal, C. Durcan, and B. Yu, “Graphene-Based Interconnects on Hexagonal Boron Nitride (h-BN) Substrate,” IEEE Electro
Device Letters, vol. 33, no. 7, 925-927 (2012).
ARTICLES UNDER REVIEW
1. N. Jain, R. Jacobs-Gedrim, Y. Xu, and B. Yu, “Resistive Switching in Ultra-Thin Two-Dimensional van der Waals Dielectric” Nature
Communications (2015).
2. N. Jain, R. B. Jacobs-Gedrim, M. Murphy, M. Shanmugam, F. Yang, Y. Xu, and B. Yu, “Electrical Conduction in Two-Dimensional
Graphene/Hexagonal Boron Nitride/Graphene Heterostructure,” Nano Letters (2015).
3. R. Jacobs-Gedrim, M. Murphy, N. Jain, F. Yang, M. Shanmugam, E. Song, Y. Kandel, P. Hesamaddin, D. B. Janes, and B. Yu, “Reversible
Crystalline-Amorphous Phase Transition in Chalcogenide Nanosheets”, Nature Materials (2015).
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Thank You for Your Attention
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Significance of Environment
Open graphene is subject to severe degradation
over time due to the effect of adsorption of
ambient molecules like N2, H2O and O2
Graphene/metal contact I-V behavior Time-dependent contact resistance shift
Demand: Graphene covered with an insulator
which protects its pristine electrical behavior

67. WWW.SUNYCNSE.COM
Metal Contacts Graphene at
1-D Edge
Fabrication made simpler with only one patterning step for
the G/h-BN/G stack and one metallization step
L Wang et al, Science 342, 614 (2013)

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2D Band Curve Fitting Results
Bilayer Graphene Trilayer Graphene
2600 2650 2700 2750 2800
P1: 2656
P2: 2688
P3: 2707
P4: 2722
Wavenumber (cm
-1
)
2600 2650 2700 2750 2800
P1: 2694
P2: 2719
Wavenubmer (cm
-1
)
2600 2650 2700 2750 2800
P1: 2696
P2: 2722
Wavenumber (cm
-1
)
Four Layer Graphene
2600 2650 2700 2750 2800
P1: 2695
P2: 2725
Wavenumber (cm
-1
)
Five Layer Graphene

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Raman Spectra of s-MLG
More layer number:
•2D band blue shift
•Intensity ratio of
G/2D increased.
• Less coupling between layers, only one peak exists in 2D band (2~5 layers)
1400 1600 1800 2000 2200 2400 2600 2800 3000
Wavenumber (cm
-1
)
as -- --
-- -- --
2D bandG band
400 1600 1800 2000 2200 2400 2600 2800 3000
2D band
Wavenumber (cm
-1
)
1layer 2layer 3layer
4layers 5layer Graphite
G band

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Lifetime Reliability Study
 Sustained current in graphene can lead
to degradation and eventual failure of
the wire
 Comparison of stacked BLG and G-BN-G
heterostructure can provide information
about improvement in graphene
interconnect reliability by incorporation
of h-BN between graphene layers
 Mean Time to fail (MTTF) in G-BN-G
heterostructure will be higher than MLG
and stacked BLG at same current
density
X Chen et al, IEEE EDL 2012