Raman spectroscopy as a versatile tool for studying the properties of graphene

Ferrari, Andrea C.; Basko, D. M.

doi:10.1038/nnano.2013.46

Cited by 5,810 publications

(4,987 citation statements)

References 181 publications

(519 reference statements)

Supporting

271

Mentioning

4,658

Contrasting

Unclassified

Order By: Relevance

“…Raman spectroscopy is widely used for nondestructive characterization of 2D crystals such as graphene and transition metal 5 dichalcogenides. 14,15 In magnetic crystals, low energy excitations such as two magnon scattering appears in the Raman spectrum, 16 or some of the Raman peak positions or intensities change when spins are ordered. 17,18 Since direct measurement of the magnetic properties of atomically thin magnetic materials is difficult, especially in the case of antiferromagnetism, the changes in the Raman spectrum concomitant with a magnetic transition are good alternatives for monitoring magnetic ordering in such materials.…”

Section: Introductionmentioning

confidence: 99%

Ising-Type Magnetic Ordering in Atomically Thin FePS₃

et al. 2016

View full text Add to dashboard Cite

Magnetism in two-dimensional materials is not only of fundamental scientific interest but also a promising candidate for numerous applications. However, studies so far, especially the experimental ones, have been mostly limited to the magnetism arising from defects, vacancies, edges or chemical dopants which are all extrinsic effects. Here, we report on the observation of intrinsic antiferromagnetic ordering in the two-dimensional limit. By monitoring the Raman peaks that arise from zone folding due to antiferromagnetic ordering at the transition temperature, we demonstrate that FePS3 exhibits an Ising-type antiferromagnetic ordering down to the monolayer limit, in good agreement with the Onsager solution for two-dimensional order-disorder transition.The transition temperature remains almost independent of the thickness from bulk to the 2 monolayer limit with TN ~118 K, indicating that the weak interlayer interaction has little effect on the antiferromagnetic ordering. KEYWORDSIsing model, Antiferromagentism, Magnetic ordering in 2 Dimension, FePS3, Iron phosphorus trisulfide, Raman spectroscopy 3 Magnetism has played an important role in advancing our understanding of the quantum nature of materials. Especially, low-dimensional magnetism has been a fertile playground, in which novel physical concepts have been learned and thereby moved the frontiers of the modern understanding of materials science. Most of the three-dimensional magnetic systems, other than some exceptional cases of quantum spin and/or strong frustration, host a magnetic order. On the other hand, fluctuations are so strong and easily destroy stabilization of order parameters in onedimensional systems as pointed out in the seminal work by Bethe. 1 Two-dimensional (2D) systems, on the other hand, have attracted much attention because the presence or absence of long-range order depends on the type of spin-spin interactions, which themselves compete with intrinsic fluctuations of either quantum and/or thermal nature.The XXZ Hamiltonian reads 2 ( )where XY J and I J are spin-exchange energies on the basal plane and along the c-axis, respectively; using an order-converting dual transformation that unlike the 1D system there is a phase transition at a finite temperature in the 2D Ising system. 4 Therefore, ferromagnetic or antiferromagnetic ordering in the 2D limit is possible only in the Ising model. There has been some indirect test of this prediction including the most notable one by Kim and Chan using CH4 molecules adsorbed 4 on graphite. 5 However, despite its fundamental importance, there has been no experimental work using a real 2D magnetic material.2D van der Waals (vdW) materials could be an ideal system for the study of 2D magnetism. 6 Unfortunately, however, finding suitable vdW materials and producing atomically thin magnetic materials have been a challenge. Although there have been a few reports of producing atomically thin samples of magnetic materials, 7-10 observation of magnetic ordering in the atomically thin limit has been l...

show abstract

Section: Introductionmentioning

confidence: 99%

Ising-Type Magnetic Ordering in Atomically Thin FePS₃

et al. 2016

View full text Add to dashboard Cite

show abstract

“…This allows monitoring defects, 42−45 as well as local doping. 6,42,46,47 The doping of the p−n junction can be determined by measuring the back gate voltage dependence of the photoresponse. Figure 3a compares the photovoltage in dependence of back gate voltage, V g , with the resistance, at an incident light wavelength of 633 nm.…”

mentioning

confidence: 99%

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

et al. 2014

View full text Add to dashboard Cite

Graphene's high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal−graphene−metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo-and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.KEYWORDS: Graphene, photodetectors, Raman spectroscopy, photoresponse, optoelectronics T he unique optical and electronic properties of graphene make it ideal for photonics and optoelectronics. 1 A variety of prototype devices have already been demonstrated, such as transparent electrodes in displays 2 and photovoltaic modules, 3 optical modulators, 4 plasmonic devices, 4−9 microcavities, 10,11 and ultrafast lasers. 12 Among these, a significant effort is being devoted to photodetectors (PDs). 6,10,11,13−25 Various photodetection schemes and architectures have been proposed to date. The simplest configuration is the metal− graphene−metal (MGM) PD, in which graphene is contacted with metal electrodes as the source and drain. 13−18 These PDs can be combined with metal nanostructures enabling local surface plasmons and increased absorption, realizing an enhancement in responsivity (i.e., the ratio of the lightgenerated electrical current to the incident light power). 6,26 Microcavity based PDs were also used, with increased light absorption at the cavity resonance frequency, again achieving an increase in responsivity. 10,11 Another scheme is the integration of graphene with a waveguide to increase the effective interaction length with light. 25,27 Hybrid approaches employ semiconducting nanodots as light-absorbing media. 22 In this case, light excites electron−hole (e−h) pairs in the nanodots; the electrons are trapped in the nanodot, while the holes are transferred to graphene, thus effectively gating it. 22 Under applied drain−source bias, this results in a shift in the Dirac point, thus a modulation of the drain−source current. 22 Due to the long trapping time of the electrons within the dot, the transferred holes can cycle many times through the phototransistor before relaxation and e−h recombination. This gives a photoconductive gain; i.e., one absorbed photon effectively results in an electrical current of several electrons. Responsivities >10 7 A/W were reported, 22 but with a millisecond time scale, not suitable for, e.g., high-speed optical communications. Devices were also fabricated for detection of THz light. 28,29 In this low energy range, Pauli blocking forbids the direct excitation of e−h pairs due to finite doping. Instead, an antenna coupled to source and gate of the device excites plasma waves within the channel. These are rectified, leading to a detectable dc out...

show abstract

“…[24] Precedents in the literature have also observed this shift and attributed it to charge transfer from G to the adsorbate. [29] Accordingly, the abnormal shift of the 2D band toward higher values could be attributed to a charge transfer from G to Au nanoplatelets due to the different work function of the two components.. X-ray photoelectron spectroscopy (XPS) establishes the composition and distribution of each element in the material into different coordination environments. As expected Au ̅̅̅̅ /fl-G films contain C (89 at%), N (1 at%), O (5 at%) and Au (4 at%).…”

mentioning

confidence: 99%