Iron-Catalyzed Room Temperature Cross-Couplings of Bromophenols with Aryl Grignard Reagents

Article abstract of DOI:10.1002/adsc.201900839

Herein we report a room temperature Fe-catalyzed coupling reaction of various bromophenols with aryl Grignard reagents, which exhibits a wide substrate scope and high functional group tolerance. For the first time, the combination of simple Fe(acac)₃/PBu₃/Ti(OEt)₄ has been used as an effective catalyst for the biaryl couplings of bromophenols or their Na or K salts with debromination and etherification side reactions being well suppressed. Various biphenols including natural product garcibiphenyl C as well as pharmaceutical diflunisal and its ethyl ester were facilely synthesized using the present protocol. (Figure presented.).

Full text of DOI:10.1002/adsc.201900839

Article
pubs.acs.org/JPCC
Cite This: J. Phys. Chem. C 2019, 123, 8923−8931
Pervasive Ohmic Contacts in Bilayer Bi2O2Se−Metal Interfaces
Lianqiang Xu,†,‡,⊥ Shiqi Liu,‡,⊥ Jie Yang,‡ Bowen Shi,‡ Yuanyuan Pan,‡ Xiuying Zhang,‡ Hong Li,§
Jiahuan Yan,‡ Jingzhen Li,‡ Linqiang Xu,‡ Jinbo Yang,*,‡,∥ and Jing Lu*,‡,∥
†School of Physics and Electronic Information Engineering, Engineering Research Center of Nanostructure and Functional
Materials, Ningxia Normal University, Guyuan, Ningxia 756000, P. R. China
‡State Key Laboratory of Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, P. R. China
§College of Mechanical and Material Engineering, North China University of Technology, Beijing 100144, P. R. China
∥Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
ABSTRACT: Due to their outstanding gate electrostatics, two-dimensional (2D)
semiconducting materials are regarded as promising channel materials used in the next-
generation field-effect transistors (FETs). However, a Schottky barrier often existing at
the 2D semiconductor−metal interface can evidently degrade the device performance.
Very lately, 2D layered semiconducting bismuth oxyselenide (Bi2O2Se) is synthesized
and exhibits high carrier mobility and excellent air stability. We conduct a systematic
exploration, for the first time, on the interfacial nature of bilayer (BL) Bi2O2Se in
contact with six metals (Sc, Ti, Ag, Au, Pd, and Pt) that cover a wide work function
range by density functional theory-based band structure calculations and quantum
transport simulations in a FET configuration. Remarkably, our results reveal that all the
contacts in the lateral direction are n-type Ohmic due to the robust beyond-gap Fermi level pinning at the interface.
Experimentally, the actual BL Bi2O2Se FET with a Au/Pd electrode indeed shows an n-type Ohmic contact. Hence, low contact
resistance can easily be expected in BL Bi2O2Se devices.
300 K and 3 × 105 cm2 V−1 s−1 at 1.9 K), and remarkable
1. INTRODUCTION
structure stability under pressure (up to 30 GPa).28,29,31,32
In recent years, many research studies have proved that two-
dimensional (2D) semiconducting materials can effectively
suppress the short-channel effects in field-effect transistors
(FETs) owing to atomically thin uniform thickness and
Furthermore, it has been evidenced that the 2D Bi2O2Se-based
top-gated FETs with the Pd/Au metal electrode exhibit
superior current Ion/Ioff ratios (larger than 106) and a nearly
ideal subthreshold swing (about 65 mV dec−1 at 300 K).29
dangling-bond-free lateral pristine surfaces.1−9 Thus, 2D
Hence, as a competitive channel material, 2D Bi2O2Se is
semiconducting materials are regarded as very promising
anticipated to hold great potential applications in future high-
candidate channel materials for using them in the next decade
electronic and optoelectronic devices.1,3,6,7,9−12 In a practical
performance (HP) and low-power (LP) digital logic nano-
devices.29 In addition, it should be noted that 2D Bi2O2Se also
FET with a 2D semiconductor as the channel material,
however, the semiconductor−metal contact is commonly
required for the carrier injection due to the absence of an
displays exceptional thermoelectricity,33−35 photoresponsiv-
ity,36−39 piezoelectricity, and ferroelectricity.40 However, at
present, a comprehensive understanding about the nature of
effective substitutional doping scheme for 2D materi-
als.1,7,9,12−15 A Schottky barrier (SB) usually emerging at the
interface of the semiconductor−metal can remarkably lower
the carrier injection efficiency and significantly deteriorate the
FET performance.6,13,16,17 Therefore, to enhance the device
performance, it is essential to effectively decrease the contact
resistance or seek the Ohmic contact at the semiconductor−
metal interfaces for the upcoming 2D FETs.14−16,18−27
the 2D Bi2O2Se−metal contacts is still lacking. Consequently,
to fill the gap, it is imperative to implement a systematic
investigation of 2D Bi2O2Se−metal interfaces.
The bilayer (BL) Bi2O2Se can be regarded as the simplest
multilayer Bi2O2Se. In this paper, we carry out a systematic
exploration on the interfacial properties of BL Bi2O2Se
contacting with various metals (Sc, Ti, Ag, Au, Pd, and Pt)
spanning a broad work function scope in a FET geometry for
the first time. To achieve this goal, first-principles-based
electronic structure computations and quantum transport
simulations are employed to analyze the Schottky barrier
height (SBH) and contact polarity. It is found that in the
Most recently, the 2D layered bismuth oxyselenide
(Bi2O2Se) crystal, which has a body-centered tetragonal
structure composed of alternately arranged insulating
[Bi2O2]2+ layers and conducting [Se]2− layers, was discovered
via an artful and low-cost chemical vapor deposition
protocol.28−30 As a new star material, the 2D atomically thin
Bi2O2Se film has superb properties, such as outstanding air
stability, the layer-dependent bandgap (0.35−1.34 eV),
ultrahigh electron Hall mobility (about 450 cm2 V−1 s−1 at
Received: December 21, 2018
Revised: March 12, 2019
Published: March 15, 2019
© 2019 American Chemical Society
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vertical direction, electronic structure computations reveal that
the SB and tunneling barrier (TB) are absent at the interface of
the BL Bi2O2Se−metal contact owing to the intensive band
hybridization; in the lateral direction, quantum transport
simulations unmask that the n-type Ohmic contacts are always
formed at the interface between the BL Bi2O2Se−metal system
and channel BL Bi2O2Se. It should be highlighted that the
simulated results of the BL Bi2O2Se and Au/Pd contact are in
good agreement with the present experimental conclusion.29
Our calculated results indicate that the interface of BL Bi2O2Se
and the investigated metal tends to form a (quasi) Ohmic
contact, and BL Bi2O2Se is a distinguished candidate channel
material for the forthcoming sub-5 nm technology nodes.
Bi2O2Se−metal interfacial system, the lattice parameter of six
metals is changed to match that of BL Bi2O2Se, and a vacuum
buffer space of not less than 20 Å is added in the erect
direction of the BL Bi2O2Se−metal interface. The 2 × 5 BL
Bi2O2Se matches 3 × 3 Ag and Au surfaces in the (111)
orientation, the 3 × 2 BL Bi2O2Se matches 2 × 21 Pd and
Pt surfaces in the (111) orientation, the 2 × 5 BL Bi2O2Se
matches the 7 × 3 Sc surface and the 2 × 10 BL
Bi2O2Se matches the 3 × 19 Ti surface in the (0001)
orientation, respectively. The mismatches between the six
metals and BL Bi2O2Se are 1.28−5.97%, as shown in Table 1.
Table 1. Calculated Properties of BL Bi2O2Se−Metal
a
2. METHODOLOGY
Interfaces
2.1. Interface Modeling. The optimized crystal structure
of BL Bi2O2Se, which is composed of alternately arranged two
buckled [Bi2O2]2+ layers and three planar [Se]2− layers, is
shown in Figure 1a,b. To balance the nonstoichiometry
Ag
Au
Pd
Pt
Sc
Ti
ε (%)
dz (Å)
dmin (Å)
Eb (eV)
WM (eV)
WS (eV)
ΦeL,W (eV)
ΦhL,W (eV)
ΦeL,T (eV)
ΦhL,T (eV)
ETg (eV)
4.59
2.20
2.53
2.67
4.46
4.02
0.07
0.36
−0.02
0.37
0.35
4.60
2.31
2.52
2.55
5.13
4.82
0.87
−0.44
−0.16
0.42
5.45
1.84
2.39
4.02
5.24
4.03
0.08
0.35
−0.16
0.38
0.22
5.97
1.93
2.41
4.66
5.67
4.72
0.77
−0.34
−0.05
0.55
1.28
2.00
2.61
4.36
3.54
3.25
−0.70
1.13
−0.33
0.82
0.49
5.05
1.84
2.60
5.25
4.27
3.85
−0.10
0.53
−0.45
0.85
0.40
̅
0.26
0.50
a
ε stands for the mean lattice constant mismatch of the BL Bi2O2Se−
̅
metal interface. dz stands for the mean distance of the BL Bi2O2Se−
metal interface along the vertical direction. dmin stands for the
minimum interatomic distance of the BL Bi2O2Se−metal interfaces.
The binding energy Eb stands for the energy per BL bismuth
oxyselenide unit required to remove BL Bi2O2Se from the metal
surface. WM and WS stand for the calculated WF of the clean metal
surface and the BL Bi2O2Se−metal system, respectively. ΦeL,W (ΦLh,W
)
Figure 1. (a) Side and (b) top views of freestanding BL Bi2O2Se.
Square indicates the unit cell of BL Bi2O2Se. (c) Initial geometry of
the BL Bi2O2Se−metal (blue ball) interface. (d, e) Band diagram and
partial density of states (PDOS) of intrinsic BL Bi2O2Se, respectively.
and ΦeL,T (ΦhL,T) stand for the lateral electron (hole) SBHs calculated
using the work function approximation method and the quantum
transport simulation approach, respectively. EgT stands for the
transmission gap of the BL Bi2O2Se FETs.
resulting from the additional [Se]2− layer, the two outermost
[Se]2− layers are passivated with H atoms. The relaxed lattice
constant of the Bi2O2Se bilayer is a = b = 3.981 Å, which is in
agreement with the reported results.29,33 As displayed in Figure
1d, the BL Bi2O2Se terminated with H atoms has an indirect
bandgap of 0.43 eV with the absence of spin−orbital coupling
at the density functional theory (DFT) level, which is
consistent with the previous study.29 The valence band
maximum (VBM) is located at the Γ point and the conduction
band minimum (CBM) is located at the N point, which is in
accordance with the former report.31 It should be emphasized
that BL Bi2O2Se has a body-centered tetragonal Brillouin zone
(BZ),31 rather than the simple tetragonal BZ adopted in
several simulations about Bi2O2Se.29,40 From the projected
density of states (PDOS) of BL Bi2O2Se exhibited in Figure 1e,
it can be observed that the states near the CBM and VBM
mainly originate from the p orbital of BL Bi2O2Se.
We employ six metals Sc, Ti, Ag, Au, Pd, and Pt, which
involve a broad scope of work functions, and BL Bi2O2Se to
construct the 2D semiconductor−metal interfacial system. As
illustrated in Figure 1d, the BL Bi2O2Se−metal interfacial
system is composed of five-layer metal atoms and BL Bi2O2Se,
and the top two layers of metal atoms are fixed in the process
of structure optimization. In the process of building the BL
2.2. Band Structure Calculations. The structure
relaxations, band structures, and DOS of the BL Bi2O2Se
crystal and the BL Bi2O2Se−metal interfacial system are
calculated using the Vienna ab initio simulation package.41,42
The plane-wave basis sets43 with a cutoff energy of 500 eV,
projected augmented wave pseudopotential,44,45 and general-
ized gradient approximation (GGA) of Perdew−Burke−
Ernzerhof (PBE) functional46,47 are chosen in this study.
The convergence tolerance for the residual force and total
energy are, respectively, set to not more than 0.02 eV Å−1 and
10−5 eV/atom. The k-mesh density based on the Monkhorst−
Pack scheme48 is adapted to less than 0.02 Å−1 in the Brillouin
zone sampling. Both van der Waals (vdW) interaction at the
DFT-D3 level49−51 and dipole correction are also considered
in all calculations.
2.3. Quantum Transport Simulations. To comprehen-
sively examine the interfacial properties of BL Bi2O2Se−metal
contact via quantum transport simulations, we design a two-
probe FET model (Figure 2), which is composed of the
optimized BL Bi2O2Se−metal interfacial system (used as an
electrode) and intrinsic BL Bi2O2Se with a length of about 5
nm (used as a channel material). The two electrodes (left and
right) of the FET model are semi-infinite, and the types of
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3. RESULTS AND DISCUSSION
3.1. Geometries and Electronic Structures. The relaxed
BL Bi2O2Se−metal interfacial systems are presented in Figure
3. The positions of atoms at the BL Bi2O2Se−metal interface
Figure 2. Schematic diagram of a single-gated BL Bi2O2Se FET. A, C,
and E denote the three carrier (electron/hole) transfer regions. B
denotes the source or drain interface (pink dashed line) and D stands
for the source/drain-channel interface (blue dashed line). ΦV
represents the vertical SBH and ΦL denotes the lateral SBH.
boundary conditions along the x, y, and z directions are set as
periodic, Neumann, and Dirichlet, respectively. According to
the previous results, a 2D semiconducting FET with a channel
length of ∼5 nm can well satisfy the purpose of evaluating SBH
and contact polarity in a FET scheme.15,52,53
The transmission coefficient and local device density of
states (LDDOS) of the two-probe FET model constructed
above under zero bias-voltage and gate-voltage are simulated
via ab initio quantum transport simulations, which is based on
DFT combined with the nonequilibrium Green’s function
(NEGF) method and implemented in the Atomistix ToolKit
(ATK) 2017.12 package.54−56 The transmission coefficient
T(E) is derived from the mean value of k-dependent
transmission coefficients Tk∥(E) through the Brillouin zone,
and the Tk∥(E) at energy E can be defined as
Figure 3. Side view of the relaxed architectures and mean electrostatic
potential distribution in planes are perpendicular to the BL Bi2O2Se−
metal (Ag, Au, Pd, Pt, Sc, and Ti) interfaces. Fermi level is set as zero.
Purple, red, brown, and white balls represent Bi, O, Se, and H atoms,
respectively.
k//
k//
k//
k//
†
Tk (E) = Tr[ΓL (E)G (E)ΓR (E)(G (E)) ]
//
(1)
In Formula 1, the Gk∥(E) (Gk∥(E))† stands for the retarded
are strongly changed due to the intensive interaction of BL
Bi2O2Se and the metal surface. In this work, we define three
parameters, such as the binding energy (Eb), average distance
(dz), and minimum interatomic distance (dmin), to better
understand the interaction between BL Bi2O2Se and metal
surfaces. The binding energy Eb of BL Bi2O2Se−metal
interfacial systems is defined as
(advanced) Green function, and the ΓkL(R)(E) = i(∑L(R)
−
k∥
∥
(∑kL(R))†) represents the level broadening stemming from the
∥
left (right) electrode that is depicted by the electrode self-
k∥
56,57
energy ∑L(R)
.
The functional with the GGA−PBE form,
single-ξ polarized (SZP) basis set, real-space mesh cutoff of 75
Hartree, and electrode temperature of 300 K are adopted
throughout the whole calculations. The Monkhorst−Pack-
based k-point sampling in the electrode and the central region
of a FET model are 10 × 1 × 100 and 10 × 1 × 1, respectively.
It is important to address that, in the light of the published
works, the single-ξ polarized (SZP) basis set is usually
sufficiently accurate for the systems of bulk metal used as
the electrode.58 And, for a FET based on a 2D semiconductor,
the doped carriers originating from the metal electrode can
greatly shield the electron−electron interaction in the channel.
Consequently, the DFT−GGA strategy-based single electron
approximation is effective enough to describe the electron
behavior of the heavily doped 2D semiconductor and evaluate
the SBH in a FET configuration, comparing with the results of
the GW method and experiment.59 For instance, at the DFT−
GGA level, the calculated bandgap is 1.53 eV for a doped
degenerately ML MoSe2, which is in good agreement with the
results of the GW method (1.59 eV) and experiment (1.58
eV);60 the calculated electron (hole) SBH for the monolayer/
bilayer/trilayer black phosphorene FET using Ni as the
electrode is 0.39 (0.26)/0.52 (0.19)/0.48 (0.20) eV,15,61,62
which is also consistent with the experimental value of 0.64
(0.35)/0.48 (0.23)/0.40 (0.21) eV.63
Eb = (EBL Bi O Se + EM − ES)/N
2
2
where EBL Bi O Se, EM, and Es stand for the total energy of the
2
2
intrinsic BL Bi2O2Se, the clean metal surface, and the BL
Bi2O2Se−metal interfacial systems, respectively. N represents
the total number of BL Bi2O2Se unit cell, as shown in Figure
1b. dz is the mean distance between BL Bi2O2Se and contacted
metal along the vertical direction of the BL Bi2O2Se−metal
interface, and dmin is the minimum atomic distance of the
selenium atom to the metal atom, as presented in Figure 1c.
The calculated parameters including Eb, dz, and dmin are listed
in Table 1. The binding energy Eb of BL Bi2O2Se contacting
with Ag (2.67 eV) and Au (2.55 eV) is apparently smaller than
that of BL Bi2O2Se contacting with Pd (4.02 eV), Pt (4.66 eV),
Sc (4.36 eV), and Ti (5.25 eV); correspondingly, the interlayer
distance dz of BL Bi2O2Se-Ag (2.20 Å) and -Au (2.31 Å)
contact is obviously larger than that of BL Bi2O2Se-Pd (1.84
Å), -Pt (1.93 Å), -Sc (2.00 Å), and -Ti (1.84 Å) contact. In
spite of this, the values of Eb and dz still give rise to strong
bonding at the interface of the BL Bi2O2Se−metal contact,
which can be further verified in the following analyses.
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Figure 4. Band diagrams of BL Bi2O2Se−metal (Ag, Au, Pd, Pt, Sc, and Ti) systems. Gray and red lines represent band structures of the interfacial
system and band structures projected to BL Bi2O2Se, respectively. The Fermi level is set as zero and denoted by a dashed blue line.
Figure 5. Partial density of states (PDOS) of BL Bi2O2Se−metal (Ag, Au, Pd, Pt, Sc, and Ti) systems. Fermi level is set as zero and denoted by
dashed little-gray lines.
Figure 6. Total electron density distributions of the BL Bi2O2Se−metal (Ag, Au, Pd, Pt, Sc, and Ti) systems. Purple, red, brown, and white balls
represent Bi, O, Se, and H atoms, respectively.
To gain better insight into the interaction strength between
BL Bi2O2Se and the checked metals, we calculate the energy
band structures, partial density of states (PDOS) projected
onto BL Bi2O2Se, and total electron distribution of BL
Bi2O2Se−metal interfacial systems and show the analyzed
results in Figures 4, 5, and 6, respectively. As shown in Figure
4, the band structure of BL Bi2O2Se is intensively destroyed
and the Fermi level passes through the BL Bi2O2Se-derived
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bands all the time, indicating strong band hybridization and
metallization of BL Bi2O2Se in the examined BL Bi2O2Se−
metal systems. Correspondingly, a great deal of gap states
originating from BL Bi2O2Se spreads all over the band gap of
intrinsic BL Bi2O2Se, as illustrated in Figure 5.
As shown in Figure 6, there is notable electron accumulation
in the considered BL Bi2O2Se−metal interface region,
suggesting the formation of a robust covalent bonding between
BL Bi2O2Se and the metal surface. All the analytic results above
clearly indicate that the BL Bi2O2Se absorbed on Ag, Au, Pd,
Pt, Sc, and Ti substrates undergoes a forceful metallization and
strong covalent bonds are formed at the interface of the BL
Bi2O2Se−metal contact. Therefore, the vertical Schottky
barrier (which may exist at interface B in Figure 2) is absent,
and the corresponding Schottky barrier height (SBH), ΦV, is
zero due to the intensive metallization between BL Bi2O2Se
and all the investigated metals. It is noteworthy that the
interfaces between BL Bi2O2Se and the surveyed six metals all
form the favorable Ohmic contact. So, a high efficiency of
carrier injection can be anticipated when Ag, Au, Pd, Pt, Sc,
and Ti are used as electrode metals to contact BL Bi2O2Se.
The other important potential barrier, namely the tunneling
barrier (TB) that can also greatly influence the electrical
characteristic of a 2D semiconductor−metal interface, may
occur at interface B (as shown in Figure 2). To assess the TB
of the BL Bi2O2Se−metal interface, we plot the electrostatic
potential distribution of the studied 2D semiconductor−metal
interfacial systems. As shown in Figure 3, the TB vanishes at
the BL Bi2O2Se-Ag, Au, Pd, Pt, Sc, and Ti interfaces owing to
the drastic metallization of BL Bi2O2Se. The absence of SB and
TB at the checked BL Bi2O2Se−metal interface indicates that
electrons can easily flow from the investigated metals to the
contacted BL Bi2O2Se.
3.2. Lateral SBH Analysis. In a BL Bi2O2Se FET model,
the SB may exist at interface B (the vertical SB) and D (the
lateral SB), as shown in Figure 2. Based on the above analyses,
the vertical SBH is zero for all the checked BL Bi2O2Se−metal
interface. At present, there are two methods, work function
approximation (WFA) and quantum transport calculation, that
can be used to evaluate the lateral SBH of interface D. By
means of the WFA, the lateral electron SBH (ΦeL,W) (hole SBH
(ΦhL,W)) can be derived from the difference between the CBM
(VBM) of the intrinsic BL Bi2O2Se and the Fermi level of the
BL Bi2O2Se−metal interfacial system, and the computed
results are shown in Table 1. At the WFA level, two lateral
n-type Ohmic contacts are formed at interface D (Figure 2)
when Sc and Ti are used as electrodes, two lateral p-type
Ohmic contacts are found as Au and Pt are employed as
electrodes, and two n-type quasi Ohmic contacts are generated
with the electron (hole) SBHs of 0.06 (0.37) and 0.07 (0.36)
eV, respectively, while Ag and Pd are chosen as electrodes. The
SBH results obtained from the WFA method are illustrated in
Figure 7. It is noteworthy that the coupling between the
electrode region and the channel region is ignored in the WFA
strategy.
Figure 7. Comparison of the lateral SBHs obtained from the WFA
and the quantum transport simulations for the BL Bi2O2Se FET.
real-space energy band in a FET, is used to analyze the lateral
electron (hole) SBH that is quantitatively obtained from the
difference of the CBM (VBM) and the Fermi level of the
channel BL Bi2O2Se at interface D (Figure 2). The LDDOS
and its corresponding transmission spectrum in the BL
Bi2O2Se FET are shown in Figure 8. It should be noted that
the average SBH of the left and right interface is adopted if the
lateral electron (hole) SBH is not equal at the two
interfaces.15,61−63 For instance, the left and right lateral
electron (hole) SBHs of the BL Bi2O2Se FET with the Ag
electrode are 0.11 (0.25) eV and −0.14 (0.49) eV, respectively,
and the average lateral electron (hole) SBH of −0.02 (0.37) eV
is obtained. After careful analysis, six lateral n-type Ohmic
contacts are formed at interface D (Figure 2) when the
checked six metals are used as electrodes in a FET model.
Therefore, low contact resistance is anticipated in the BL
Bi2O2Se-based FETs using Ag, Au, Pd, Pt, Sc, and Ti as the
electrodes. The analytic results of the lateral electron (hole)
SBH ΦLe,T (ΦLh,T) derived from the quantum transport
calculation strategy are also displayed in Figure 7 and
compared with those obtained from the WFA method. It is
important to note that the formation of n-type Ohmic contact
at BL Bi2O2Se-Pd and BL Bi2O2Se-Au interfaces is well
consistent with the experimental results.29 As shown in Figure
8, the bands bend downward due to the electron transfer from
the electrode region to the channel area when Ag, Au, and Pt
are used as electrode metals.
The coupling between the electrode and the channel region
in a FET model can bring two influences. One is the
generation of the MIGS in the channel, and the MIGS serve as
a reservoir, while the charge transfer among the electrode and
the channel, usually resulting in the within-gap Fermi level
pinning (FLP).59 The other is the modulation of the Fermi
level of the relaxed BL Bi2O2Se−metal interfacial systems
through the formation of the dipole electric field at interface D.
The Fermi level modulation can lead to the within- and
beyond-gap FLP. As shown in Figure 9b, the Fermi level of the
electrode is modulated and lifted above the conduction band
of the channel, thus the FLP existing at interface D is
attributed to the beyond-gap FLP effect. So, interface D forms
the n-type Ohmic contact. The beyond-gap FLP resulting from
the Fermi level modulation have been reported at the
interfaces of the MoS2−metal and graphene−metal.64,65
To overcome the deficiency of the WFA scheme, a more
reliable protocol named quantum transport calculation, which
takes the electrode-channel coupling into account, is adopted
to evaluate the lateral SBH at interface D (Figure 2) in a two-
probe FET model with the channel length of about 5
nm.15,52,53,61 In the quantum transport calculation, the
LDDOS in the BL Bi2O2Se FET, which directly depicts the
distribution of the metal-induced-gap states (MIGS) and the
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Figure 8. LDDOS and transmission spectrums of the BL Bi2O2Se FET with (a) Ag, (b) Au, (c) Pd, (d) Pt, (e) Sc, and (f) Ti electrodes. Solid
white lines represent CBM and VBM of BL Bi2O2Se in the channel region. White dash lines and gray dashed lines are Fermi levels in LDDOS and
transmission spectrums, respectively. ΦeL,T represents the electron SBH and ΦLh,T stands for the hole SBH in the lateral direction. MIGS at the
source−channel interface is circled by the red curves. BL Bi2O2Se−metal system and the BL Bi2O2Se channel are separated by the upright black
lines.
Figure 9. (a) Variation of the lateral electron SBHs in the BL Bi2O2Se transistors with the bulk metal work function. S represents the pinning factor
that was calculated from the Schottky−Mott rule. (b) Demonstration of Fermi level pinning in the BL Bi2O2Se FET. Gray dashed lines and dotted
lines, respectively, represent the first and second change of the Fermi level.
The strength of FLP is quantitatively reflected by the
pinning factor S, which is obtained from the slope of the fitted
red line that depicts the variation of the lateral electron SBH
with the work function of the corresponding metal electrode,
as shown in Figure 9a. In this definition, 0 ≤ S ≤ 1, S = 0
means a total FLP and S = 1 stands for no FLP at interface D
in Figure 2. The fitted S is 0.16 in our investigated BL Bi2O2Se
FET, which is more smaller than the calculated S in ML MoS2
FET (S = 0.27),52 ML black phosphorene FET (S = 0.28),15
ML arsenene FET (S = 0.33),23,66 and ML blue phosphorene
FET (S = 0.42).20 The value of S = 0.16 indicates that the
beyond-gap FLP effect at the interface of the electrode and the
channel region in the BL Bi2O2Se transistor is much more
intensive than those in the above-mentioned FETs. Because of
the consideration of the coupling effect between the electrode
and the channel, the quantum transport calculation scheme is
more accurate than the WFA process to assess the SBH,
especially in a FET that has the strong FLP effect. The beyond-
gap FLP effect in the BL Bi2O2Se FET is illustrated in Figure
9b.
In a FET, the transport gap ETg is defined as the sum of the
lateral electron and hole SBH calculated via the quantum
transport calculation scheme, that is, ETg = ΦLe,T + ΦLh,T
.
Accordingly, the transport gap ETg of the BL Bi2O2Se transistor
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Article
with Ag, Au, Pd, Pt, Sc, and Ti as electrode metals is 0.35, 0.26,
0.22, 0.50, 0.49, and 0.40, respectively, as demonstrated in
Table 1. At the DFT−GGA−PBE level, most of these ETg are
close to the bandgap (0.43 eV) of intrinsic BL Bi2O2Se except
for BL Bi2O2Se FET with Au and Pd as electrodes due to
heavy doping.
ACKNOWLEDGMENTS
■
This work is financially supported by the Higher School
Scientific Research Project of Ningxia Education Department
of China (NGY2018-130/Document no. [2014] 222), the
Natural Science Foundation of Ningxia of China (No.
2018AAC03236/NZ15262), the key research and develop-
ment program of Ningxia of China (2018BEE03023), the key
Scientific Research Project of Ningxia Normal University of
China (No. NXSFZDA1807/NXSFZD1511), and the youth
talent support program of Ningxia of China (2016). This paper
is also funded by the National Natural Science Foundation of
China (No. 11674005/11664026/11704406), the Ministry of
Science and Technology of China (No. 2016YFB0700600
(National Materials Genome Project) and 2016YFA0301300).
4. CONCLUSIONS
In summary, for the first time, we employ two methods, ab
initio electronic structure calculations and first-principles
quantum transport simulations, to conduct a systematic and
comprehensive exploration on the contact properties in BL
Bi2O2Se FET using Ag, Au, Pd, Pt, Sc, and Ti as electrode
metals. The analytic results indicate that the vertical SB
(interface B in Figure 2) is absent owing to the strong
metallization of BL Bi2O2Se on the contact metal. The lateral
contact (interface D in Figure 2) is n-type Ohmic for all the
checked six metals owing to the intensive beyond-gap FLP at
the interface. Furthermore, the formation of the (quasi) Ohmic
contact at the interface between BL Bi2O2Se and other bulk
metal is always expected. The favorable contact properties
(Ohmic contact) of BL Bi2O2Se with the checked bulk metals
make BL Bi2O2Se a competitive candidate channel material for
using it in the electronic and optoelectronic applications in the
upcoming decade.
Our investigation gives a deep insight into the interfacial
properties of BL Bi2O2Se contacting with Ag, Au, Pd, Pt, Sc,
and Ti electrodes in theory, and provides an instruction for the
design of BL Bi2O2Se-based devices. Interestingly, the latest
theoretical investigations reveal that the double-gated mono-
layer and bilayer Bi2O2Se metal-oxide-semiconductor FETs
can satisfy the requirements of the International Technology
Roadmap for Semiconductors (2013 edition) for high-
performance devices.67,68 Thus, BL Bi2O2Se is deserved to
be deeply explored for using it as the channel material of
electronic and optoelectronic devices.
REFERENCES
■
(1) Fiori, G.; Bonaccorso, F.; Iannaccone, G.; Palacios, T.;
Neumaier, D.; Seabaugh, A.; Banerjee, S. K.; Colombo, L. Electronics
Based on Two-Dimensional Materials. Nat. Nanotechnol. 2014, 9,
768−779.
(2) Zeng, M.; Xiao, Y.; Liu, J.; Yang, K.; Fu, L. Exploring Two-
Dimensional Materials toward the Next-Generation Circuits: From
Monomer Design to Assembly Control. Chem. Rev. 2018, 118, 6236−
6296.
́
(3) Zhang, S.; Guo, S.; Chen, Z.; Wang, Y.; Gao, H.; Gomez-
Herrero, J.; Ares, P.; Zamora, F.; Zhu, Z.; Zeng, H. Recent Progress in
2d Group-Va Semiconductors: From Theory to Experiment. Chem.
Soc. Rev. 2018, 47, 982−1021.
(4) Quhe, R.; Li, Q.; Zhang, Q.; Wang, Y.; Zhang, H.; Li, J.; Zhang,
X.; Chen, D.; Liu, K.; Ye, Y.; Dai, L.; Pan, F.; Lei, M.; Lu, J.
Simulations of Quantum Transport in Sub-5-nm Monolayer
Phosphorene Transistors. Phys. Rev. Appl. 2018, 10, No. 024022.
(5) Wang, Y.; Huang, P.; Ye, M.; Quhe, R.; Pan, Y.; Zhang, H.;
Zhong, H.; Shi, J.; Lu, J. Many-Body Effect, Carrier Mobility, and
Device Performance of Hexagonal Arsenene and Antimonene. Chem.
Mater. 2017, 29, 2191−2201.
(6) Ye, M.; Zhang, D.; Yap, Y. Recent Advances in Electronic and
Optoelectronic Devices Based on Two-Dimensional Transition Metal
Dichalcogenides. Electronics 2017, 6, No. 43.
(7) Sangwan, V. K.; Hersam, M. C. Electronic Transport in Two-
Dimensional Materials. Annu. Rev. Phys. Chem. 2018, 69, 299−325.
(8) Yoon, Y.; Ganapathi, K.; Salahuddin, S. How Good Can
Monolayer MoS2 Transistors Be? Nano Lett. 2011, 11, 3768−3773.
(9) Schwierz, F.; Pezoldt, J.; Granzner, R. Two-Dimensional
Materials and Their Prospects in Transistor Electronics. Nanoscale
2015, 7, 8261−8283.
(10) Shim, J.; Park, H.-Y.; Kang, D.-H.; Kim, J.-O.; Jo, S.-H.; Park,
Y.; Park, J.-H. Electronic and Optoelectronic Devices Based on Two-
Dimensional Materials: From Fabrication to Application. Adv.
Electron. Mater. 2017, 3, No. 1600364.
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: jbyang@pku.edu.cn (J.Y.).
*E-mail: jinglu@pku.edu.cn (J.L.).
ORCID
Lianqiang Xu: 0000-0002-6801-8587
Shiqi Liu: 0000-0002-9166-8254
Xiuying Zhang: 0000-0001-6427-9061
(11) Akinwande, D.; Petrone, N.; Hone, J. Two-Dimensional
Flexible Nanoelectronics. Nat. Commun. 2014, 5, No. 5678.
(12) Chhowalla, M.; Jena, D.; Zhang, H. Two-Dimensional
Semiconductors for Transistors. Nat. Rev. Mater. 2016, 1, No. 16052.
(13) Allain, A.; Kang, J.; Banerjee, K.; Kis, A. Electrical Contacts to
Two-Dimensional Semiconductors. Nat. Mater. 2015, 14, 1195−
1205.
(14) Kang, J.; Liu, W.; Sarkar, D.; Jena, D.; Banerjee, K.
Computational Study of Metal Contacts to Monolayer Transition-
Metal Dichalcogenide Semiconductors. Phys. Rev. X. 2014, 4,
No. 031005.
(15) Pan, Y.; Wang, Y.; Ye, M.; Quhe, R.; Zhong, H.; Song, Z.; Peng,
X.; Yu, D.; Yang, J.; Shi, J.; Lu, J. Monolayer Phosphorene−Metal
Contacts. Chem. Mater. 2016, 28, 2100−2109.
(16) Jena, D.; Banerjee, K.; Xing, G. H. 2D Crystal Semiconductors:
Intimate Contacts. Nat. Mater. 2014, 13, 1076−1078.
Author Contributions
⊥L.X. and S.L. contributed equally to this work.
Author Contributions
Jinbo Yang and Jing Lu conceived the original idea for the
project. Lianqiang Xu and Shiqi Liu carried out the project
with the help of Jie Yang, Bowen Shi, Yuanyuan Pan, Xiuying
Zhang, Hong Li, Jiahuan Yan, Jingzhen Li, and Linqiang Xu.
This manuscript was written by Lianqiang Xu and Shiqi Liu
with input from the other authors. All work was supervised by
Jinbo Yang and Jing Lu. All authors contributed to the
scientific planning and discussions.
Notes
The authors declare no competing financial interest.
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The Journal of Physical Chemistry C
Article
(17) Park, J. Y.; Cho, J.; Jun, S. C. Review of Contact-Resistance
Analysis in Nano-Material. J. Mech. Sci. Technol. 2018, 32, 539−547.
(18) Lv, X.; Wei, W.; Zhao, P.; Li, J.; Huang, B.; Dai, Y. Tunable
Schottky Contacts in MoSe2/NbSe2 (M = Mo and W) Hetero-
structures and Promising Application Potential in Field-Effect
Transistors. Phys. Chem. Chem. Phys. 2018, 20, 1897−1903.
(19) Liu, Y.; Guo, J.; Zhu, E.; Liao, L.; Lee, S.-J.; Ding, M.; Shakir, I.;
Gambin, V.; Huang, Y.; Duan, X. Approaching the Schottky−Mott
Limit in Van Der Waals Metal−Semiconductor Junctions. Nature
2018, 557, 696−700.
(20) Li, J.; Sun, X.; Xu, C.; Zhang, X.; Pan, Y.; Ye, M.; Song, Z.;
Quhe, R.; Wang, Y.; Zhang, H.; Guo, Y.; Yang, J.; Pan, F.; Lu, J.
Electrical Contacts in Monolayer Blue Phosphorene Devices. Nano
Res. 2018, 11, 1834−1849.
(21) Chen, Z.; Zhang, R.; Yang, J. First-Principles Study on Layered
C2N−Metal Interfaces. Langmuir 2018, 34, 2647−2653.
(22) Yang, L.; Charnas, A.; Qiu, G.; Lin, Y.-M.; Lu, C.-C.; Tsai, W.;
Paduano, Q.; Snure, M.; Ye, P. D. How Important Is the Metal−
Semiconductor Contact for Schottky Barrier Transistors: A Case
Study on Few-Layer Black Phosphorus? ACS Omega 2017, 2, 4173−
4179.
(23) Wang, Y.; Ye, M.; Weng, M.; Li, J.; Zhang, X.; Zhang, H.; Guo,
Y.; Pan, Y.; Xiao, L.; Liu, J.; Pan, F.; Lu, J. Electrical Contacts in
Monolayer Arsenene Devices. ACS Appl. Mater. Interfaces 2017, 9,
29273−29284.
(24) Hao, J.; Jianwei, L.; Langhui, W.; Ying, D.; Yadong, W.; Hong,
G. Ohmic Contact in Monolayer Inse-Metal Interface. 2D Mater.
2017, 4, No. 025116.
(25) Mojtaba, F.; Geert, B. Ohmic Contacts to 2D Semiconductors
through Van Der Waals Bonding. Adv. Electron. Mater. 2016, 2,
No. 1500405.
(26) Liu, Y.; Xiao, H.; Goddard, W. A. Schottky-Barrier-Free
Contacts with Two-Dimensional Semiconductors by Surface-Engi-
neered Mxenes. J. Am. Chem. Soc. 2016, 138, 15853−15856.
(27) Chuang, H.-J.; Chamlagain, B.; Koehler, M.; Perera, M. M.;
(35) Liangruksa, M. Effects of Negative Response of Electron
Transport to Thermoelectric Properties of Bi2O2Se. Comput. Mater.
Sci. 2016, 120, 142−148.
(36) Li, J.; Wang, Z.; Wen, Y.; Chu, J.; Yin, L.; Cheng, R.; Lei, L.;
He, P.; Jiang, C.; Feng, L.; He, J. High-Performance Near-Infrared
Photodetector Based on Ultrathin Bi2O2Se Nanosheets. Adv. Funct.
Mater. 2018, 28, No. 1706437.
(37) Yin, J.; Tan, Z.; Hong, H.; Wu, J.; Yuan, H.; Liu, Y.; Chen, C.;
Tan, C.; Yao, F.; Li, T.; Chen, Y.; Liu, Z.; Liu, K.; Peng, H. Ultrafast
and Highly Sensitive Infrared Photodetectors Based on Two-
Dimensional Oxyselenide Crystals. Nat. Commun. 2018, 9, No. 3311.
(38) Wu, J.; Liu, Y.; Tan, Z.; Tan, C.; Yin, J.; Li, T.; Tu, T.; Peng, H.
Chemical Patterning of High-Mobility Semiconducting 2D Bi2O2Se
Crystals for Integrated Optoelectronic Devices. Adv. Mater. 2017, 29,
No. 1704060.
(39) Fu, Q.; Zhu, C.; Zhao, X.; Wang, X.; Chaturvedi, A.; Zhu, C.;
Wang, X.; Zeng, Q.; Zhou, J.; Liu, F.; Tay, B. K.; Zhang, H.;
Pennycook, S. J.; Liu, Z. Ultrasensitive 2D Bi2O2Se Phototransistors
on Silicon Substrates. Adv. Mater. 2019, 29, No. 1804945.
(40) Wu, M.; Zeng, X. C. Bismuth Oxychalcogenides: A New Class
of Ferroelectric/Ferroelastic Materials with Ultra High Mobility.
Nano Lett. 2017, 17, 6309−6314.
(41) Kresse, G. Ab Initio Molecular Dynamics for Liquid Metals. J.
Non-Cryst. Solids 1995, 192−193, 222−229.
(42) Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid
Metals. Phys. Rev. B 1993, 47, 558−561.
(43) Kresse, G.; Furthmuller, J. Efficiency of Ab-Initio Total Energy
̈
Calculations for Metals and Semiconductors Using a Plane-Wave
Basis Set. Comput. Mater. Sci. 1996, 6, 15−50.
(44) Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the
Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758−
1775.
̈
(45) Blochl, P. E. Projector Augmented-Wave Method. Phys. Rev. B
1994, 50, 17953−17979.
(46) Perdew, J. P.; Burke, K.; Ernzerhof, M. ERRATA: Generalized
Gradient Approximation Made Simple. Phys. Rev. Lett. 1997, 78,
1396.
́
Yan, J.; Mandrus, D.; Tomanek, D.; Zhou, Z. Low-Resistance 2D/2D
Ohmic Contacts: A Universal Approach to High-Performance WSe2,
MoS2, and MoSe2 Transistors. Nano Lett. 2016, 16, 1896−1902.
(28) Wu, J.; Tan, C.; Tan, Z.; Liu, Y.; Yin, J.; Dang, W.; Wang, M.;
Peng, H. Controlled Synthesis of High-Mobility Atomically Thin
Bismuth Oxyselenide Crystals. Nano Lett. 2017, 17, 3021−3026.
(29) Wu, J.; Yuan, H.; Meng, M.; Chen, C.; Sun, Y.; Chen, Z.; Dang,
W.; Tan, C.; Liu, Y.; Yin, J.; Zhou, Y.; Huang, S.; Xu, H. Q.; Cui, Y.;
Hwang, H. Y.; Liu, Z.; Chen, Y.; Yan, B.; Peng, H. High Electron
Mobility and Quantum Oscillations in Non-Encapsulated Ultrathin
Semiconducting Bi2O2Se. Nat. Nanotechnol. 2017, 12, 530−534.
(30) Zhan, B.; Liu, Y.; Tan, X.; Lan, J.-l.; Lin, Y.-h.; Nan, C.-W.
Enhanced Thermoelectric Properties of Bi2O2Se Ceramics by Bi
Deficiencies. J. Am. Ceram. Soc. 2015, 98, 2465−2469.
(47) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient
Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868.
(48) Monkhorst, H. J.; Pack, J. D. Special Points for Brillouin-Zone
Integrations. Phys. Rev. B 1976, 13, 5188−5192.
(49) Bucko, T.; Lebegue, S.; Hafner, J.; Angyan, J. G. Improved
Density Dependent Correction for the Description of London
Dispersion Forces. J. Chem. Theory Comput. 2013, 9, 4293−4299.
(50) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping
Function in Dispersion Corrected Density Functional Theory. J.
Comput. Chem. 2011, 32, 1456−1465.
(51) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and
Accurate Ab Initio Parametrization of Density Functional Dispersion
Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010,
132, No. 154104.
(52) Zhong, H.; Quhe, R.; Wang, Y.; Ni, Z.; Ye, M.; Song, Z.; Pan,
Y.; Yang, J.; Yang, L.; Lei, M.; Shi, J.; Lu, J. Interfacial Properties of
Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the
Energy Band Calculations. Sci. Rep. 2016, 6, No. 21786.
́
̌
̀
́
́
́
(31) Pereira, A. L. J.; Santamaría-Perez, D.; Ruiz-Fuertes, J.; Manjon,
F. J.; Cuenca-Gotor, V. P.; Vilaplana, R.; Gomis, O.; Popescu, C.;
́
́
Munoz, A.; Rodríguez-Hernandez, P.; Segura, A.; Gracia, L.; Beltran,
̃
A.; Ruleova, P.; Drasar, C.; Sans, J. A. Experimental and Theoretical
Study of Bi2O2Se under Compression. J. Phys. Chem. C 2018, 122,
8853−8867.
(53) Pan, Y.; Li, S.; Ye, M.; Quhe, R.; Song, Z.; Wang, Y.; Zheng, J.;
Pan, F.; Guo, W.; Yang, J.; Lu, J. Interfacial Properties of Monolayer
MoSe2−Metal Contacts. J. Phys. Chem. C 2016, 120, 13063−13070.
(54) Soler, J. M.; Artacho, E.; Gale, J. D.; García, A.; Junquera, J.;
(32) Chen, C.; Wang, M.; Wu, J.; Fu, H.; Yang, H.; Tian, Z.; Tu, T.;
̈
Peng, H.; Sun, Y.; Xu, X.; Jiang, J.; Schroter; Niels, B. M.; Li, Y.; Pei,
D.; Liu, S.; Ekahana, S. A.; Yuan, H.; Xue, J.; Li, G.; Jia, J.; Liu, Z.;
Yan, B.; Peng, H.; Chen, Y.; et al. Electronic Structures and Unusually
Robust Bandgap in an Ultrahigh-Mobility Layered Oxide Semi-
conductor, Bi2O2Se. Sci. Adv. 2018, 4, No. eaat8355.
́
́
Ordejon, P.; Sanchez-Portal, D. The Siesta Method for Ab Initio
Order-N Materials Simulation. J. Phys.: Condens. Matter 2002, 14,
2745−2779.
(33) Yu, J.; Sun, Q. Bi2O2Se Nanosheet: An Excellent High-
Temperature N-Type Thermoelectric Material. Appl. Phys. Lett. 2018,
112, No. 053901.
(34) Liu, R.; Lan, J.-L.; Tan, X.; Liu, Y.-c.; Ren, G.-k.; Liu, C.; Zhou,
Z.-f.; Nan, C.-w.; Lin, Y.-h. Carrier Concentration Optimization for
Thermoelectric Performance Enhancement in N-Type Bi2O2Se. J. Eur.
Ceram. Soc. 2018, 38, 2742−2746.
̌
(55) Smith, D. R.; Schultz, S.; Markos, P.; Soukoulis, C.
Determination of Effective Permittivity and Permeability of
Metamaterials from Reflection and Transmission Coefficients. Phys.
Rev. B 2002, 65, No. 195104.
́
(56) Brandbyge, M.; Mozos, J.-L.; Ordejon, P.; Taylor, J.; Stokbro,
K. Density-Functional Method for Nonequilibrium Electron Trans-
port. Phys. Rev. B 2002, 65, No. 165401.
8930
DOI: 10.1021/acs.jpcc.8b12278
J. Phys. Chem. C 2019, 123, 8923−8931

The Journal of Physical Chemistry C
Article
(57) Kim, W. Y.; Kim, K. S. Carbon Nanotube, Graphene,
Nanowire, and Molecule-Based Electron and Spin Transport
Phenomena Using the Nonequilibrium Green’s Function Method at
the Level of First Principles Theory. J. Comput. Chem. 2008, 29,
1073−1083.
(58) Quhe, R.; Feng, S.; Lu, J.; Lei, M. Electronic Properties of
Layered Phosphorus Heterostructures. Phys. Chem. Chem. Phys. 2017,
19, 1229−1235.
(59) Liu, S.; Li, J.; Shi, B.; Zhang, X.; Pan, Y.; Ye, M.; Quhe, R.;
Wang, Y.; Zhang, H.; Yan, J.; Xu, L.; Guo, Y.; Pan, F.; Lu, J. Gate-
Tunable Interfacial Properties of in-Plane ML MX2 1T′-2H
Heterojunctions. J. Mater. Chem. C 2018, 6, 5651−5661.
(60) Liang, Y.; Yang, L. Carrier Plasmon Induced Nonlinear Band
Gap Renormalization in Two-Dimensional Semiconductors. Phys. Rev.
Lett. 2015, 114, No. 063001.
(61) Zhang, X.; Pan, Y.; Ye, M.; Quhe, R.; Wang, Y.; Guo, Y.; Zhang,
H.; Dan, Y.; Song, Z.; Li, J.; Yang, J.; Guo, W.; Lu, J. Three-Layer
Phosphorene-Metal Interfaces. Nano Res. 2018, 11, 707−721.
(62) Pan, Y.; Dan, Y.; Wang, Y.; Ye, M.; Zhang, H.; Quhe, R.;
Zhang, X.; Li, J.; Guo, W.; Yang, L.; Lu, J. Schottky Barriers in Bilayer
Phosphorene Transistors. ACS Appl. Mater. Interfaces 2017, 9,
12694−12705.
(63) Das, S.; Zhang, W.; Demarteau, M.; Hoffmann, A.; Dubey, M.;
Roelofs, A. Tunable Transport Gap in Phosphorene. Nano Lett. 2014,
14, 5733−5739.
(64) Gong, C.; Colombo, L.; Wallace, R. M.; Cho, K. The Unusual
Mechanism of Partial Fermi Level Pinning at Metal−MoS2 Interfaces.
Nano Lett. 2014, 14, 1714−1720.
(65) Zheng, J.; Wang, Y.; Wang, L.; Quhe, R.; Ni, Z.; Mei, W. N.;
Gao, Z.; Yu, D.; Shi, J.; Lu, J. Interfacial Properties of Bilayer and
Trilayer Graphene on Metal Substrates. Sci. Rep. 2013, 3, No. 2081.
(66) Guo, Y.; Liu, D.; Robertson, J. 3D Behavior of Schottky Barriers
of 2D Transition-Metal Dichalcogenides. ACS Appl. Mater. Interfaces
2015, 7, 25709−25715.
(67) Quhe, R.; Liu, J.; Wu, J.; Yang, J.; Wang, Y.; Li, Q.; Li, T.; Guo,
Y.; Yang, J.; Peng, H.; Lei, M.; Lu, J. High-performance Sub-10 nm
Monolayer Bi2O2Se Transistors. Nanoscale 2019, 11, 532−540.
(68) Yang, J.; Quhe, R.; Li, Q.; Liu, S.; Xu, L.; Pan, Y.; Zhang, H.;
Zhang, X.; Li, J.; Yan, J.; Shi, B.; Pang, H.; Xu, L.; Zhang, Z.; Lu, J.;
Yang, J. Sub 10 nm Bilayer Bi2O2Se Transistors. Adv. Electron. Mater.
2019, 5, No. 1800720.
8931
DOI: 10.1021/acs.jpcc.8b12278
J. Phys. Chem. C 2019, 123, 8923−8931