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The structure of suspended graphene sheets

Authors:
Jannik Meyer at University of Tuebingen
Jannik Meyer
AK Geim
AK Geim
AK Geim
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Mikhail I. Katsnelson at Radboud University
Mikhail I. Katsnelson
K S Novoselov
K S Novoselov
K S Novoselov
  • This person is not on ResearchGate, or hasn't claimed this research yet.
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Abstract

The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles. However, the physical structure of graphene--a single layer of carbon atoms densely packed in a honeycomb crystal lattice--is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. On the other hand, perfect two-dimensional crystals cannot exist in the free state, according to both theory and experiment. This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix. Here we report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range crystalline order. However, our studies by transmission electron microscopy also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the observed corrugations in the third dimension may provide subtle reasons for the stability of two-dimensional crystals.
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∃∋,∃(∃∀,:++((∃4;
∀∃∀4∋%:∋&4+#4∋,∀∃
#∃+∃;.8<∗1=#∀+(#4∋∃∃
%4∃(∋,(4∋∃%∃%4∃((((∋
%∃4,,(∃44&(∃∃∀.701
∃,#,(+(∃++7#+4∃4∃4,9
∃,∀+(∋((∃.01>∀&4
(∃,(,##+4∃∃&#∀∀,∋∀4((
(&,(∃(∋+(
44∋+4 , ∀(   ∀( (∃,(  ∀44
∋∋#∀(,(4∃(∀.<1∋∃∃∃∃+(
(∋∃∋+4∋#(,∃7,+4(∀,∋∃+4
#∃#(∀,+4∃∃(∃79(∃∃∋∋(
5+∀#,+7∋(?+∋∋∀44∋44(
,44?++∀(∋∀+#
,≅(+(∃:5+;#∋,(∋((+#+4
,∃4(∃(∋∃∋∋((∀+∃∋,∃:+4∋5+;∀∃
∋(4(∃?+∀∋∀,∋+4∋((+4
∃4∃,(∋+7+4∋(&,(
:5+;?+∋∋∋+7#(∃,∀,5
∃45+,#∋(((+∋,+4#∃&,#(
∃∋(∀,7#(∀,>,∃∋∀#,∃∀∃(∀4
∋(∃+∀,∋(∋+7+4((,(
&4
((#∃∀((∃(+∀,#+7+4(∃4,
+,∃(∋∋∃4∋∋∋∀∃∋∃(∃
+4∃(∀∋∋∃#(∀4,#%∃4∃4∃5+∀
#&4∋(∋∋∃4+∋+4,∋5+
&4∃(#(∋∃∃4(+4(∃∋Α(Α
( # +7( 4   ∋ (∋∃ ∋ +7 +4   
∃4∃4∃:5+;9(2∀9(∋(+∋
(∋∋∃4∀(∃∃∀+∃,∀∋∃∃&((
((∃&∃,∀,(&45+∋4
∋(∋∋∃4:∗7∗;(:7∗;∋∀∃∋+∋+7
+4>∃∃+(4
    + # ∀ ∀∃ ∀ : ∃4  5+ ; 5
∃45++#∃4(+,∀∋,+4#
+4,∃∃4∀44(+(
∀(+37∋(∀(∀,(∋∃(∃(∋∋∃
(∀,,(:;∃+∋,∀+4
∃∃+4(Χ∃,∋∆.01(4(∋
∃+(#∃∋(∋∋∃#+∀!∀
+∀∋+7+4(∃,4(∋∀,+∀∀(∋∃
?
#(++∋∀,((∋∋∃4
#∃+(+#∀∀∃∀(+#((
(∋∋∃,∀%∃.1((∃((∋∋∃4
5+,∃,(#∃++(,∀+∀∃+∋
4∋∀#∋&,(+(∃∋∀∋
+7+4,∃,#,4(∃4(44∋
∀+454∋#,(+∃4∀&4∃(
49#∋&4,∃(∀∃∋
(∋∋∃4:%,76∋∃;,∀((,(+.1
5+∀&4#,(,(+&4∃(+4∋
#∀,∃∋∃,∋∀%5∀∋∋∋+4
∃:5+;∃∋∋(44(∃∀4∋∃4∃&+
∃:5+∃;?∃(∋∋∃4#7(∃:+,∃∋
?#(4;∀+%4∃4∃∀4∃∀∀++∋
(∋∋∃4∀(#∀+∀:∃;#∃+++
(&+4(∋((∃∀(,∃+
,(+∋(∋∋∃4 #∀ ∃+    4   (
#(∀(+(∃:5+(;∃4(+∀
:5+,;(∋∋∃4∋∋∃∃∋,∋∋%
∃#(∋∋#4∃+45+∀∀∃
∀+∀4(∋∋∃4∋∃(∃,∀44(,∃
#( # ∃+  +  (  (     ∀( ,
4∃∃(4(∋,≅∀+(∃,(∃,(,+(4(∃
∋∋#∃∃#∀∀5+∋
5 !∀  5+∀ ∋+ #  (( ∀ ∋ ,(+ ∋ 
(∋∋∃4#∃++∃(∃+>∃4≅#(∃
#(444≅4∃4∃4∃!∀
+#∀∀∋∃∀+(+4#(∋∃
45+∋+4((∃∀∋,≅∀+5(∋∋+7
,#∋∀(∃+,#8Φ(Φ∀∋∃((
∋(∃+,Γ0Φ5#7,∀#∋∀(,
#∃   ≈Φ :5+ +;   4     (∋∋∃ 4 ,(
4∃:5+∃7;∀∋∃4∃#(
(∃(,(# #2>#∋+4,
# ∃∀(   (∃ (∋∋∃ 4 #∀( 4(   (∃+ 
(∃∋∃∀+,∀∃4,∃,∃∀(,∀#
(∃(4∃#∀,+∀∀4∃(∋∋+4
∃∀∀∋0Φ(∃∋∀4Η#∃+,∀∀,#∀4∃
(∋(+∋(∋∃.3781
4&, ∋∋∀(∃∀+∀##,
5 , ∃,(∃:∋#;∃∃+∋
(∋∋∃(∃>###∀(&4∃44(∀∃+(
,#&4(∃∃∀(5+∋∃∃+(
,≈∗∃∀+∀∃4∃:;∃∃
∃(∀4∋(∋∋∃4!∀+∀,∋∋(∋∋
#∀,∃∀(#∃4(∀#∀44∋,
∀4∋ ∋Ι∗∗∃ ,≤0!∀∃(
+ # ∀ ∀( (∋∋∃ 4 ∋ ∃∀+( +4  :
∀44∋; 5  # ∃∀∀( 9 , ∋∃∀+ #
+≈
,(7∋7+∀(+∀44(,∃∀?
++∋∀,ϑ∋∀∋+7+4∀∃#∃∀(
,∀9(,∃∀(∋∋∃#+(∃∀(:5+
∋;(((∃(∀∃∀+∃∀(,&4∃(∋∃,(>
(,∋&+∃∋#(+(4(
+:5++;(∃∃(+∀∋∃∀(∀∋∋#7+4∃,&4∃(
∀∋(∋∋,+∀∃∃5+/(∃∃∃
9∋∋##∃#,∋,+7+4
#44∃∀(,+4∃7∀+#
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∃∀+∃#∃+(∀+&4∀#∀((,∀+(
(44∃∋((∃
((∀∃4∋∃%∃∃∃&∀∋
(9∃∃(∋∃.)81,(∃∃4∃∃∀+∋%
+4((4((∀&4∃(∀∃∃
+!∀∋+4#(∃,>(∋∃
∃∃4∃∀+4(∀∃,∋(∋∋4,(∋(∋∋
4,∃,∋,+4((44∋∃,
4∃∀+∃+4,>(∃
+ ∋ % ,  4(∃(  (∃ , ∀+ ∃
∃∃4∃∃∀4++,(+,∀∃+.701,∀∃+∃
!∀+∋(∃.01,(&4∃(∀∃∋
:∃79(;,(+7∃,(>(
,(+∃∀(∋∃(!∀∀7∋74(∋+
+∋∃∃!∀+#∀,,∀∋∀
&4 ( ∃ ∀(  !∀(  ∃∋  (( ∃ ∋ 
∃∀++444∃∋∃∃∀+
∃#+,∋∃+∃+4.71(∃&4∋
∀∀∀4∃∃∃∀∃∀44∋#∃9.<1
∃∃∀∋7+++4∃∃,,Κ∃(∋∋&∃+
(∃∋∋∀∀∃,(∃∃4∃∀++,∋
∀∃∀,∋%,((∃∃∃∃∃4∃(
44∃,!∀&(%∃,4∀∃9+
44∃∀4∀,∋+7∀∃∃∃4(+
∋(∃∀∀+∃79,9+(∃,∃((∋
∃+#∃∀74(,∀∀,∋∋(+:∋
&4∃∃(∃;
?∃∃∋(∋∋∃∃∃,∋/03337
33<:∗∗/;
#7(+∋%∃∋+4∋
∗1<)7∗∗:∗∗0;
Λ+Μ6=2(−?&4,∋!∀∀=
∋∋∃(Ν4+4∋∗1∗7∗/:∗∗0;
/− ?∀+Ο,ϑ#(∀+4∀)∃32878:</;
0− ?Θ∀!∀444!∀(∃4(3.))7
:<0;
32(∀2%Λ∀(−∀#(∀+∃45.370:<);
)2(∀2%(2∋9?∃−+−>&∋(<8∗
8%(#(∃)200∗70/:<38;
<#7(∃∃∋3(3/%
∗/07∗/0:∗∗0;
∗+?∃∃∃∋(∃∃4(4&+4
%<7<3:∗∗3;
0
>#∃= ,+?+∃∃∀∃∀
∋,+4<07<0/:∗∗3;
∃47,(∃4∋∗∗%8783:∗∗3;
% (−25∀∃∀,#∃(&∃(6
∃7∗1∗807∗<:<8);
/ (92(2%∀−∋7∃∋49(,∃
),0+∗<7:<<;
0% −(6,+#
6(∃∋∃+4∗∗/
3(=∀+1∃#/∃&∃,(−>&∋(<0/
)%(6+=,∃∋∋+∋+7
#7(4∃=,+(∃),273:<33;
8Ρ,4%=,∀∃∀∃(#∋758
∃∗2:/;Σ<<7/0<:<8/;
<Λ+5(2,#=∀+∀∋∃
80:8;Σ))7/3:<<;
∗?6−4+∃∀(∀+4&∋
+#Σ5∋%((%∀(80:7;Σ78:∗∗3;
∀∃− #(?+22/#0
8∃>&∋(ϑ−<88
4∃=208∃>&∋(ϑ−∗∗
−+2?∃∃∃+∋∃(∃+4∋∃
/3073/8:<<<;
/%−(∀− ∃=75∃&7(∃∃+∋∃
3&∃3%∗<∗7<):<38;
0=∀∃,∋##∀∃∀(44686388∃∗%
2∗)7∗)3:∗∗;
3Μ∀554Τ ∀∋∋(+∋4∋+#
∃,∀,(∃∃44∃),1∗000Υ0000:∗∗∗;
)ΛΘ(∃ϑ+∋∃,∀,Σ∃
∀(∃)90.//∗0:∗∗;
8=∀+Μ∀44∃∃,∀,∋∗+8:∗∗3;
<9Ρ+∀44∋#∃9+4∃),+2
∗38∗:∗∗3;
365+(%∋5?∋4(+∃∃7
∀?##∀44(,?ϑ4Κ∃−??− :ϑ;(
 ∃∃#(+∋∃∀44∋5>:(;
4(∃(!∀∋∀(,(((:ςΚ(;
(:+ς∃∀;
3
4
5+∀Σ 5 +7∋(?+∋∀4((+4
,∃4:+∀(∋∀+(∃(,#;+7
+4?∃(∋∋∃+∋(∋∋∋∋#+
∃#∀(∃(4(,(+(+∋((+
+∃,0∗∗
)
5+∀Σ(?+∋∋(((+
∋+7(,7+44∃∀+−4∗∗?∃,
?∃(∋∋∃4∋+4∀(∃(∃+∋∗Φ/Φ(
3Φ4∃&9=#∀(Λ<?4(3∗Ρ
Ω∃(#:0µ;∃(4∀#(∀,
4∃∃4,#∀+∋∗3((∀
∋0∗((∋∋∃4#∃((%∋∋∀!∀
4,∃,(#∃+(∋∋∃+∋
4∋∀#∋&,!∀++∋∃#∀7
(∃:;∋+4&+(&∃4(
(∃:∗7∗;:Α4∃+;(:7∗;:Α4∃+;4∃
∋∀∃∋+∋4(4∋(∀∃∋
,++∋∃#∋(,∀(,∀∋+#∃((
4≅4+(#(((∀∃∀
#∃#∀(5∀∋∋4Κ∃(∃4.1(∃
∋∋∃4(./1 (∀∋#7+4
,
8
5+∀ Σ −   5 +4 ∃   4∃
:44∃ #;   ∋ ∃∀+( +4  # ∀+ 
!∀∋∀(&4∃4∃4∃∋∋∋(
:(;(∃(44(∃∀∃4∃∃∋+4:,∃&+;(5
∃∀+(∀44∋(∋∋∃+,∋∃∃4∃∋∋∋∃
∀(∃74(∀(∋∋∃4,∃,∀(++
:(∃(,((;(∋∋∃4∀∃(∋∀#∋&
:∃4#5+;%∋∋∃4,((∋∋+#∀
+4∀+?∀∋(∋∋∃4#++7+4
&4(4(∀∃#∃,∃∃#
45∃+,∃((4∃∃∋(∋∋∃4:∗7
∗;(:7∗;4≅∃(∋∀#(∋&:56=;∃4∃4∃
(,∃(4∃∃4∃#∃:∗Φ(/Φ;∃((
#∋∀,,∀∃∀∃∀∃∀(,#∋(,
∀4(,∃##(∋(∋∋∃44(∀∃
∃∃,(+∀++(,∀(:4(;56=∋:∗7∗;(∋∋∃
4+7(,7,(+4∋∃∋∀∃∋+
((∋(++∀+∋+,#∗Φ
0Φ(∋∋∃4(∀∃4#(∋∃∃4∀
+
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5+∀/Σ 3 ?+∋∋#7
+4,(+#∀,∋((∃∃∋/
∃∀∋∋#7+4∃∃(4(+∃(∃+
  :∋# (+;    ∀∋∃  ,∃ ,  ∃7
∀++#∃(,∀+5?∃∃+∋∗∗Ρ∃
,
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



!
∀##∃%&∋(
∃%&
)∋∗∀+∃%&∋∗
,∗∀+∋∗
#−.)∋/∀∋
−01,#
∋
#)∋,∀∋
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#
 −   10   ∋       
 2∋)∋,3 
∋

#
+
 4(∋         )∋ !∗∀     ++ ∀
+2#∀5
6
6∀

 ∋ ∗ +2    )∋ !/∋ ∗    
##)∋!,∋
#++
∋)7
               
∀∋ ∗   ) 7 
∋/
  #!−∀
∋
   #  
∋ 8     # #    −9   ∀ 
 : ≈;  ∋)−
!19
)∋!4∋8;
)∋∀
#∋8)∋
−∀    #        ∋ 
     #     < 
∋#
           ∋ 8     
)∋=∀)∋!∋)
;−∋>#
!#

!!∋

)
)? +
∀
∋(∋≅#
        #   ∋   
/,∀∋/+4(
∋?−.∀.∀−∀∋
)!?(∋∀
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... While the formidability of the challenge was further revealed by many audacious endeavors using specialized or advanced equipment, e.g. in situ nanomechanical scraping 14 and in situ or pre-situ high-temperature annealing, [9][10][11] limited improvements have been made over a three-stage cleaning procedure established more than a decade ago. 15 These contaminants cast doubt on the existence of truly freestanding graphene, in light of possible roles played by the irremovable contaminants in stabilizing graphene, 7 even after the recognition 16 that out-of-plane undulations stabilize extended 2D structures. The contaminants have until now prevented the acquisition of electron energy loss (EEL) spectra of graphene with data quality comparable to those of graphite 17 to reflect the chemical bonding and band structure similarities. ...
Ultraclean suspended graphene by radiolysis of adsorbed water
Preprint
Full-text available
  • May 2024
Access to intrinsic properties of a 2D material is challenging due to the absence of a bulk that would dominate over surface contamination, and this lack of bulk also precludes effective conventional cleaning methods that are almost always sacrificial. Suspended graphene and carbon contaminants represent the most salient challenge. This work has achieved ultraclean graphene, attested by electron energy loss (EEL) spectra unprecedentedly exhibiting fine-structure features expected from bonding and band structure. In the cleaning process in a transmission electron microscope, radicals generated by radiolysis of intentionally adsorbed water remove organic contaminants, which would otherwise be feedstock of the notorious electron irradiation induced carbon deposition. This method can be readily adapted to other experimental settings and other materials, to enable previously inhibited undertakings that rely on the intrinsic properties or ultimate thinness of 2D materials. Importantly, the method is surprisingly simple and robust, easily implementable with common lab equipment.
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... Graphene is a monolayer of sp 2 hybridized carbon atoms packed into a hexagonal structure [4]. GO is graphene containing various oxygen functional groups attached to its surface [5]. ...
Comparison of Antimicrobial Properties of Graphene Oxide-Based Materials, Carbon Dots, and Their Combinations Deposited on Cotton Fabrics
Article
Full-text available
  • May 2024
  • INT J MOL SCI
The rise in the antibiotic resistance of bacteria has increased scientific interest in the study of materials with unique mechanisms of antimicrobial action. This paper presents the results of studies on the antimicrobial activity of carbon materials and textiles decorated with them. A comparative analysis of the bactericidal and fungicidal activities of graphene oxide, electrochemically exfoliated multigraphene, carbon dots, and their combinations was performed. Microbiological studies on reference strains of E. coli, S. aureus, and C. albicans showed that graphene oxide inhibited growth with up to 98% efficiency. Electrochemically exfoliated multigraphene was less effective (up to 40%). This study found no significant antimicrobial activity of carbon dots and the combination of carbon dots with graphene oxide significantly weakened their effectiveness. However, the combination of electrochemically exfoliated multigraphene and carbon dots exhibits a synergistic effect (up to 76%). A study on the antimicrobial activity of decorated cotton textiles demonstrated the effectiveness of antimicrobial textiles with graphene oxide, electrochemically exfoliated multigraphene, and a combination of carbon dots with electrochemically exfoliated multigraphene.
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Unique Characteristics of Electrochemically Exfoliated Multidimensional Graphene and Its Derivatives
Chapter
  • May 2024
Graphene, a single atomic layer of graphite, is considered superior to other carbon-based graphitic allotropes due to its distinctive topologies, intriguing electrical, optical, and mechanical properties, and promising nanoelectronics. It has numerous applications in nanotechnology, including electrochemical exfoliation, which involves the use of natural graphite foils, sheets, or rods. Ion intercalations increase the interlayer gap in the electrochemical exfoliation of graphite, producing pure graphene in monolayer or multilayer forms using chemical vapor deposition and pulsed laser deposition techniques. Electrochemical exfoliation techniques dope graphene materials, incorporate covalent functional groups, integrate nanoparticles, and assemble graphene structures. Compared to other processes, electrochemical exfoliation offers benefits such as simplicity, cost-effectiveness, environmental friendliness, high production rate, and high-quality few-layered graphene sheets. EG also provides a large sheet, less oxygen content, a high C/O ratio, and outstanding electrical characteristics. This chapter’s goal is to inform readers about the characteristics and applications of currently recognized electrochemically exfoliated multidimensional graphene structures, including graphene quantum dots (GQDs), one-dimensional (1D) graphene nanoribbons (GNRs) and graphene fibers (GFs), two-dimensional (2D) graphene nanomeshes (GNMs), rippled/wrinkled graphene, and 2D graphene membranes (GMs) and three-dimensional graphene (3DG) architectures made of graphene oxide (GO) and reduced GO (rGo) and highlight their unique properties which are based on the configuration of carbon atoms.
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Bending rigidity, sound propagation and ripples in flat graphene
Article
Full-text available
  • May 2024
  • NAT PHYS
Many of the applications of graphene rely on its uneven stiffness and high thermal conductivity, but the mechanical properties of graphene—and, in general, of all two-dimensional materials—are still not fully understood. Harmonic theory predicts a quadratic dispersion for the out-of-plane flexural acoustic vibrational mode, which leads to the unphysical result that long-wavelength in-plane acoustic modes decay before vibrating for one period, preventing the propagation of sound. The robustness of quadratic dispersion has been questioned by arguing that the anharmonic phonon–phonon interaction linearizes it. However, this implies a divergent bending rigidity in the long-wavelength regime. Here we show that rotational invariance protects the quadratic flexural dispersion against phonon–phonon interactions, and consequently, the bending stiffness is non-divergent irrespective of the temperature. By including non-perturbative anharmonic effects in our calculations, we find that sound propagation coexists with a quadratic dispersion. We also show that the temperature dependence of the height fluctuations of the membrane, known as ripples, is fully determined by thermal or quantum fluctuations, but without the anharmonic suppression of their amplitude previously assumed. These conclusions should hold for all two-dimensional materials.
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Making 2‐D Materials Mechanochemically by Twin‐Screw Extrusion: Continuous Exfoliation of Graphite to Multi‐Layered Graphene
Article
Full-text available
  • May 2024
Mechanochemistry has developed rapidly in recent years for efficient chemicals and materials synthesis. Twin screw extrusion (TSE) is a particularly promising technique in this regard because of its continuous and scalable nature. A key aspect of TSE is that it provides high shear and mixing. Because of the high shear, it potentially also offers a way to delaminate 2‐D materials. Indeed, the synthesis of 2‐D materials in a scalable and continuous manor remains a challenge in their industrialization. Here, as a proof‐of‐principle, the automated, continuous mechanochemical exfoliation of graphite to give multi‐layer graphene (MLG, ≈6 layers) by TSE is demonstrated. To achieve this, a solid‐and‐liquid‐assisted extrusion (SLAE) process is developed in which organic additives such as pyrene are rendered liquid due to the high temperatures used, to assist with the exfoliation, and simultaneously solid sodium chloride is used as a grinding aid. This gave MLG in high yield (25 wt%) with a short residence time (8 min) and notably with negligible evidence for structural deterioration (defects or oxidation).
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Electrochemical-repaired porous graphene membranes for precise ion-ion separation
Article
Full-text available
  • May 2024
The preparation of atom-thick porous lattice hosting Å-scale pores is attractive to achieve a large ion-ion selectivity in combination with a large ion flux. Graphene film is an ideal selective layer for this if high-precision pores can be incorporated, however, it is challenging to avoid larger non-selective pores at the tail-end of the pore size distribution which reduces ion-ion selectivity. Herein, we develop a strategy to overcome this challenge using an electrochemical repair strategy that successfully masks larger pores in large-area graphene. 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer is successfully deposited on graphene, thanks to a strong π-π interaction in these two materials. While the CMP layer itself is not selective, it effectively masks graphene pores, leading to a large Li⁺/Mg²⁺ selectivity from zero-dimensional pores reaching 300 with a high Li⁺ ion permeation rate surpassing the performance of reported materials for ion-ion separation. Overall, this scalable repair strategy enables the fabrication of monolayer graphene membranes with customizable pore sizes, limiting the contribution of nonselective pores, and offering graphene membranes a versatile platform for a broad spectrum of challenging separations.
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Advancement of Next-Generation DNA Sequencing through Ionic Blockade and Transverse Tunneling Current Methods
Article
  • May 2024
  • SMALL
DNA sequencing is transforming the field of medical diagnostics and personalized medicine development by providing a pool of genetic information. Recent advancements have propelled solid‐state material‐based sequencing into the forefront as a promising next‐generation sequencing (NGS) technology, offering amplification‐free, cost‐effective, and high‐throughput DNA analysis. Consequently, a comprehensive framework for diverse sequencing methodologies and a cross‐sectional understanding with meticulous documentation of the latest advancements is of timely need. This review explores a broad spectrum of progress and accomplishments in the field of DNA sequencing, focusing mainly on electrical detection methods. The review delves deep into both the theoretical and experimental demonstrations of the ionic blockade and transverse tunneling current methods across a broad range of device architectures, nanopore, nanogap, nanochannel, and hybrid/heterostructures. Additionally, various aspects of each architecture are explored along with their strengths and weaknesses, scrutinizing their potential applications for ultrafast DNA sequencing. Finally, an overview of existing challenges and future directions is provided to expedite the emergence of high‐precision and ultrafast DNA sequencing with ionic and transverse current approaches.
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Relativistic Hartree–Fock X-ray and electron scattering factors
Article
  • May 1968
Kinematic X-ray and electron scattering factors, found with the use of relativistic Hartree–Fock atomic fields, are tabulated for 76 atoms and ions. Parametric fits to these are given in the range of sin θ/λ from 0.0 to 2.0 Å−1. A method is developed to obtain the electron structure factor for forward scattering for a crystal containing ionized atoms.
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Electronic Confinement and Coherence in Patterned Epitaxial Graphene
Article
  • Mar 2007
Transport in ultrathin graphite films grown on single-crystal silicon carbide is dominated by the electron-doped epitaxial graphene layer at the interface and shows graphene characteristics. Epitaxial graphene provides a platform for studying the novel electronic properties of this 2D electron gas in a controlled environment. Shubnikov-de Haas oscillations in the magnetoresistance data indicate an anomalous Berry's phase and reveal the Dirac nature of the charge carriers. The system is highly coherent with phase coherence lengths beyond 1 micrometer at cryogenic temperatures, and mobilities exceeding 2.5 square meters per volt-second. In wide structures, evidence is found for weak anti-localization in agreement with recent graphene weak-localization theory. Patterned narrow ribbons show quantum confinement of electrons. Several Hall bar samples reveal anomalous magnetoresistance patterns consisting of large structured non-periodic oscillations that may be due to a periodic superlattice potential.
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Electron atomic scattering factors and scattering potentials of crystals
Article
  • Dec 1999
  • MICRON
The concepts of complex electron atomic scattering factors and principles for evaluating these factors are discussed and their applicability is examined. Numerical procedures and routines for calculating these factors are described, and for 98 neutron atoms and 109 ions the real part of the electron atomic scattering factors were parameterized using 10 and eight parameters, respectively. Procedures for constructing two and three dimensional scattering potentials using the complex atomic scattering factors are illustrated with examples; effects of thermal vibrations of the crystal lattice are discussed.
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