Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene
© Liu et al.; licensee Springer. 2013
Received: 2 July 2013
Accepted: 12 August 2013
Published: 22 August 2013
We have performed magnetotransport measurements on multilayer epitaxial graphene. By increasing the driving current I through our graphene devices while keeping the bath temperature fixed, we are able to study Dirac fermion heating and current scaling in such devices. Using zero-field resistivity as a self thermometer, we are able to determine the effective Dirac fermion temperature (TDF) at various driving currents. At zero field, it is found that TDF ∝ I≈1/2. Such results are consistent with electron heating in conventional two-dimensional systems in the plateau-plateau transition regime. With increasing magnetic field B, we observe an I-independent point in the measured longitudinal resistivity ρxx which is equivalent to the direct insulator-quantum Hall (I-QH) transition characterized by a temperature-independent point in ρxx. Together with recent experimental evidence for direct I-QH transition, our new data suggest that such a transition is a universal effect in graphene, albeit further studies are required to obtain a thorough understanding of such an effect.
KeywordsGraphene Magnetoresistivity measurements Direct insulator-quantum Hall transition
Graphene, which is an ideal two-dimensional (2D) system, has been attracting worldwide interest since its discovery in 2004 . While the sizes of mechanically exfoliated graphene are limited, its ultrahigh quality allows one to observe fascinating physical phenomena such as ambipolar characteristics , anomalous integer quantum Hall steps , Berry's phase [2, 3], and fractional quantum Hall effect [4–6]. On the other hand, graphene prepared by chemical vapor deposition (CVD) and epitaxial graphene can be used for potential device applications because the sizes of these systems should allow realization of wafer-scale integrated circuits based on graphene .
When a charge system is appreciably heated by a driving current, the equilibrium between the phonons and the charges collapses. In this situation, effective charge temperature (T c ) can be substantially higher than lattice temperature (T L ) . This interesting physical phenomenon is normally called the charge heating effect. In some cases, there exists a simple effective charge temperature-current relation T c ∝ I α , where α is an exponent that depends on charge-phonon scattering . It is now well established that the two-bath model can be used to describe charge heating and charge energy loss rate by charge-phonon scattering . The charge heating effect has become increasingly important as device dimensions are reduced and charge mobility is increased . In particular, Dirac fermion heating in graphene is an important physical phenomenon since it affects thermal dissipation and heat management in modern electronics  and low-temperature applications such as quantum resistance metrology .
Insulator-quantum Hall (I-QH) transition [12–15] is an interesting physical phenomenon in the field of 2D physics. Especially, a direct transition from an insulator to a high Landau level filling factor ν ≥ 3 QH state which is normally described as the direct I-QH transition continues to attract interest [16–18]. Very recently, experimental evidence for direct I-QH transition in epitaxial monolayer graphene  and in mechanically exfoliated multilayer graphene  has been reported. In order to further study direct I-QH transition in the graphene-based system, one may wish to investigate Dirac fermion heating in graphene. Moreover, it is a fundamental issue to see if a current-independent point in the longitudinal resistivity when the bath temperature is fixed exists since such a point should be equivalent to the direct I-QH transition. Furthermore, one could probe current scaling on both sides of the direct I-QH transition to further study Dirac fermion-phonon scattering as well as Dirac fermion-Dirac fermion scattering, both of which are very fundamental physical phenomena.
In this paper, we report magnetotransport measurements on multilayer epitaxial graphene of few layers obtained under conditions which favor controlled growth at high temperatures . Dirac fermion heating in the high current limit is studied. It is found that in the low magnetic field regime, the effective Dirac fermion temperature obeys a simple power law TDF ∝ I≈0.5. Such results suggest that the Dirac fermion-phonon scattering rate 1/τDFP ~ T2, consistent with those in conventional 2D electron systems. With increasing magnetic field, interestingly, a current-independent point in the longitudinal resistivity is observed. It was demonstrated that such a point corresponds to the direct I-QH transition characterized by a T-independent point in ρxx. This result is further supported by the vastly different I dependences for both sides of the I-QH transition. Our new experimental results, together with recent experimental results [19, 20], indicate that direct I-QH transition is a universal effect in graphene. We suggest that further experimental and theoretical studies are required to obtain a complete picture for direct I-QH transition in graphene-based devices.
A controlled sublimation method was used for graphene growth on a 6H-SiC (0001) surface . First, the SiC substrate was cleaned using a standard procedure for substrate cleaning . Second, the optically polished Si-face surface was placed face-to-face with a polished graphite disk (FTG) and arranged such that uniform Newton rings were observed in fluorescent light . The optically finished substrate surfaces resulted in a higher rate of SiC decomposition compared to chemical–mechanical processed (CMP) surfaces and created multiple graphene layers.
The epitaxial growth process was controlled by annealing in a sequence of temperature ramp and dwell stages in Ar background gas at a pressure slightly higher than 1 atm using a commercial furnace. The substrates were first dehydrated and cleaned in the furnace at 725°C for approximately 16 h. The temperature was ramped to 1,200°C for 30 min and then ramped at 100°C/min for graphene growth at a temperature (dwell time) of 1,850°C (45 min; samples 1 and 2) or 1,950°C (30 min; samples 3 and 4). The temperatures were measured and controlled using molybdenum-sheathed type ‘C’ thermocouples.
Results and discussion
If p = 2 [10, 25], then the exponent in the temperature-scaling relation is 0.5 [21, 26–28] which is consistent with our experimental results obtained on Dirac fermions. We note that our experimental results are equivalent to a T4 dependence of energy loss rate for Dirac fermions as calculated  and observed in epitaxial, CVD-grown and exfoliated graphene [10, 30]. It is worth pointing out that previous results are obtained in the plateau-plateau transition regime [26, 27, 31] and Shubnikov-de Haas region , which is in contrast with our case in the weak insulating regime where Landau quantization is not significant. Nevertheless, our data indeed indicate such a universal exponent at approximately 0.5 for heating in various 2D systems. Moreover, our results suggest that the Dirac fermion-phonon scattering rate 1/τDFP is proportional to T2. It is worth noting that enhanced mobility can be achieved in semiconductor quantum wires  and in semiconducting graphene nanoribbons  by a high dc electric field. Such interesting results are highly desirable for practical applications in narrow graphene devices in the high current limit.
n (1013 cm−2)
ρxx/ρxy at Bc
At the crossing fields, the corresponding Landau filling factors are much larger than 2. Therefore, we have observed direct I-QH transition in all our devices [17–20]. It was argued that for direct I-QH transition in conventional semiconductor-based 2D systems, near the crossing field, ρxx is approximately ρxy, and the product of μBc is close to 1 . However, in all our devices, ρxx/ρxy is much greater than 1, and μBc is always smaller than 1. Therefore, our data suggest that further studies are required to obtain a thorough understanding of the direct I-QH transition not only in conventional 2D systems but also in disordered graphene. The observation of a current-independent point in ρxx which corresponds to its temperature-independent counterpart suggests that applying a high current is equivalent to heating up the graphene lattice.
In conclusion, we have presented magnetoresistivity measurements on multilayer epitaxial graphene. It is found that a relation between the effective Dirac fermion temperature and the driving current can be given by TDF ∝ I≈0.5 in the low magnetic field regime. With increasing magnetic field, an I-independent point in ρxx is observed which is equivalent to its T-independent counterpart in the low current limit. Evidence for direct I-QH transition has been reported in four different graphene samples. Near the crossing field where the longitudinal resistivity is approximately T-independent, ρxx is at least two times larger than ρxy. Moreover, the product of Drude mobility and Bc is smaller than 1. We suggest that further studies are required to obtain a complete understanding of direct I-QH transition in disordered graphene.
This work was funded by the National Science Council (NSC), Taiwan and National Taiwan University (grant number 102R7552-2).
- Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Grigorieva IV, Firsov AA: Electric field effect in atomically thin carbon films. Science 2004, 306: 666. 10.1126/science.1102896View Article
- Zhang Y, Tan Y-W, Stormer HL, Kim P: Experimental observation of the quantum Hall effect and Berry’s phase in graphene. Nature 2005, 438: 201. 10.1038/nature04235View Article
- Novoselov KS, Geim AK, Morozov SV, Jiang D, Katsnelson MI, Grigorieva IV, Dubonos SV, Firsov AA: Two-dimensional gas of massless Dirac fermions in graphene. Nature 2005, 438: 197. 10.1038/nature04233View Article
- Bolotin KI, Ghahari F, Shulman MD, Stormer HL, Kim P: Observation of the fractional quantum Hall effect in graphene. Nature 2009, 462: 196. 10.1038/nature08582View Article
- Du X, Skachko I, Duerr F, Luican A, Andrei EY: Fractional quantum Hall effect and insulating phase of Dirac electrons in graphene. Nature 2009, 462: 192. 10.1038/nature08522View Article
- Feldman BE, Krauss B, Smet JH, Yacoby A: Unconventional sequence of fractional quantum Hall states in suspended graphene. Science 2012, 337: 1196. 10.1126/science.1224784View Article
- Lin Y-M, Valdes-Garcia A, Han S-J, Farmer DB, Meric I, Sun Y, Wu Y, Dimitrakopoulos C, Grill A, Avouris P, Jenkins KA: Wafer-scale graphene integrated circuit. Science 2011, 332: 1294. 10.1126/science.1204428View Article
- Wennberg AKM, Ytterboe SN, Gould CM, Bozler HM, Klem J, Morkoc H: Electron heating in a multiple-quantum-well structure below 1 K. Phys Rev B 1986, 34: 4409. 10.1103/PhysRevB.34.4409View Article
- Appleyard NJ, Nicholls JT, Simmons MY, Tribe WR, Pepper M: Thermometer for the 2D electron gas using 1D thermopower. Phys Rev Lett 1998, 81: 3491. 10.1103/PhysRevLett.81.3491View Article
- Baker AMR, Alexander-Webber JA, Altebaeumer T, McMullan SD, Janssen TJBM, Tzalenchuk A, Lara-Avila S, Kubatkin S, Yakimova R, Lin C-T, Li L-J, Nicholas RJ: Energy loss rates of hot Dirac fermions in epitaxial, exfoliated, and CVD graphene. Phys Rev B 2013, 87: 045414.View Article
- Tzalenchuk A, Lara-Avila S, Kalaboukhov A, Paolillo S, Syvajarvi M, Yakimova R, Kazakova O, Janssen TJBM, Fal’ko V, Kubatkin S: Towards a quantum resistance standard based on epitaxial graphene. Nat Nanotechnol 2010, 5: 186. 10.1038/nnano.2009.474View Article
- Kivelson S, Lee D-H, Zhang S-C: Global phase diagram in the quantum Hall effect. Phys Rev B 1992, 46: 2223. 10.1103/PhysRevB.46.2223View Article
- Jiang HW, Johnson CE, Wang KL, Hannah ST: Observation of magnetic-field-induced delocalization: transition from Anderson insulator to quantum Hall conductor. Phys Rev Lett 1993, 71: 1439. 10.1103/PhysRevLett.71.1439View Article
- Hughes RJF, Nicholls JT, Frost JEF, Linfield EH, Pepper M, Ford CJB, Ritchie DA, Jones GAC, Kogan E, Kaveh M: Magnetic-field-induced insulator-quantum Hall-insulator transition in a disordered two-dimensional electron gas. J Phys Condens Matter 1994, 6: 4763. 10.1088/0953-8984/6/25/014View Article
- Wang T, Clark KP, Spencer GF, Mack AM, Kirk WP: Magnetic-field-induced metal-insulator transition in two dimensions. Phys Rev Lett 1994, 72: 709. 10.1103/PhysRevLett.72.709View Article
- Lee CH, Chang YH, Suen YW, Lin HH: Magnetic-field-induced delocalization in center-doped GaAs/Al x Ga1- x As multiple quantum wells. Phys Rev B 1998, 58: 10629. 10.1103/PhysRevB.58.10629View Article
- Song S-H, Shahar D, Tsui DC, Xie YH, Monroe D: New Universality at the magnetic field driven insulator to integer quantum Hall effect transitions. Phys Rev Lett 1997, 78: 2200. 10.1103/PhysRevLett.78.2200View Article
- Liang C-T, Lin L-H, Chen KY, Lo S-T, Wang Y-T, Lou D-S, Kim G-H, Chang Y-H, Ochiai Y, Aoki N, Chen J-C, Lin Y, Huang C-F, Lin S-D, Ritchie DA: On the direct insulator-quantum Hall transition in two-dimensional electron systems in the vicinity of nanoscaled scatterers. Nanoscale Res Lett 2011, 6: 131. 10.1186/1556-276X-6-131View Article
- Pallecchi E, Ridene M, Kazazis D, Lafont F, Schopfer F, Poirier W, Goerbig MO, Mailly D, Ouerghi A: Insulating to relativistic quantum Hall transition in disordered graphene. Sci Rep 2013, 3: 1791.View Article
- Chuang C, Lin L-H, Aoki N, Ouchi T, Mahjoub AM, Woo T-P, Bird JP, Ochiai Y, Lo S-T, Liang C-T: Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene. Nanoscale Res Lett 2013, 8: 214. 10.1186/1556-276X-8-214View Article
- Real MA, Lass EA, Liu F-H, Shen T, Jones GR, Soons JA, Newell DB, Davydov AV, Elmquist RE: Graphene epitaxial growth on SiC(0001) for resistance standards. IEEE Trans Instrum Meas 2013, 62: 1454.View Article
- de Heer WA, Berger C, Ruan M, Sprinkle M, Li X, Hu Y, Zhang B, Hankinson J, Conrad E: Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide. Proc Natl Acad Sci U S A 2011, 108: 16900. 10.1073/pnas.1105113108View Article
- Morozov SV, Novoselov KS, Katsnelson MI, Schedin F, Ponomarenko LA, Jiang D, Geim AK: Strong suppression of weak localization in graphene. Phys Rev Lett 2006, 97: 016801.View Article
- McCann E, Kechedzhi K, Fal’ko VI, Suzuura H, Ando T, Altshuler BL: Weak-localization magnetoresistance and valley symmetry in graphene. Phys Rev Lett 2006, 97: 146805.View Article
- Lara-Avila S, Tzalenchuk A, Kubatkin S, Yakimova R, Janssen TJBM, Cedergren K, Bergsten T, Fal’ko V: Disordered Fermi liquid in epitaxial graphene from quantum transport measurements. Phys Rev Lett 2011, 107: 166602.View Article
- Scherer H, Schweitzer L, Ahlers FJ, Bliek L, Losch R, Schlapp W: Current scaling and electron heating between integer quantum Hall plateaus in GaAs/Al x Gal−xAs heterostructures. Semicond Sci Technol 1995, 10: 959. 10.1088/0268-1242/10/7/010View Article
- Wei HP, Engel LW, Tsui DC: Current scaling in the integer quantum Hall effect. Phys Rev B 1994, 50: 14609. 10.1103/PhysRevB.50.14609View Article
- Brandes T, Schweitzer L, Kramer B: Multifractal wave functions and inelastic scattering in the integer quantum Hall effect. Phys Rev Lett 1994, 72: 3582. 10.1103/PhysRevLett.72.3582View Article
- Kubakaddi SS: Interaction of massless Dirac electrons with acoustic phonons in graphene at low temperatures. Phys Rev B 2009, 79: 075417.View Article
- Betz AC, Vialla F, Brunel D, Voisin C, Picher M, Cavanna A, Madouri A, Feve G, Berroir J-M, Placais B, Pallecchi E: Hot electron cooling by acoustic phonons in graphene. Phys Rev Lett 2012, 109: 056805.View Article
- Koch S, Haug RJ, von Klitzing K, Ploog K: Variable range hopping transport in the tails of the conductivity peaks between quantum Hall plateaus. Semicond Sci Technol 1995, 10: 209. 10.1088/0268-1242/10/2/015View Article
- Huang D, Gumbs G: Comparison of inelastic and quasielastic scattering effects on nonlinear electron transport in quantum wires. J Appl Phys 2010, 107: 103710. 10.1063/1.3373413View Article
- Huang D, Gumbs G, Roslyak O: Field-enhanced electron mobility by nonlinear phonon scattering of Dirac electrons in semiconducting graphene nanoribbons. Phys Rev B 2011, 83: 115405.View Article
- Huang D, Lyo SK, Gumbs G: Bloch oscillation, dynamical localization, and optical probing of electron gases in quantum-dot superlattices in high electric fields. Phys Rev B 2009, 79: 155308.View Article
- Lo S-T, Wang Y-T, Bohra G, Comfort E, Lin T-Y, Kang M-G, Strasser G, Bird JP, Huang CF, Lin L-H, Chen JC, Liang C-T: Insulator, semiclassical oscillations, and quantum Hall liquids at low magnetic fields. J Phys Condens Matter 2012, 24: 405601. 10.1088/0953-8984/24/40/405601View Article
- Lin S-K, Wu KT, Huang CP, Liang C-T, Chang YH, Chen YF, Chang PH, Chen NC, Chang CA, Peng HC, Shih CF, Liu KS, Lin TY: Electron transport in In-rich In x Ga1−xN films. J Appl Phys 2005, 97: 046101. 10.1063/1.1847694View Article
- Renard VT, Gornyi IV, Tkachenko OA, Tkachenko VA, Kvon ZD, Olshanetsky EB, Toropov AI, Portal J-C: Quantum corrections to the conductivity and Hall coefficient of a two-dimensional electron gas in a dirty Al x Ga1−xAs/GaAs/Al x Ga1−xAs quantum well: from the diffusive to the ballistic regime. Phys Rev B 2005, 72: 075313.View Article
- Chen JH, Lin JY, Tsai JK, Park H, Kim G-H, Youn D, Cho HI, Lee EJ, Lee JH, Liang C-T, Chen YF: Experimental evidence for Drude-Boltzmann-like transport in a two-dimensional electron gas in an AlGaN/GaN heterostructure. J Korean Phys Soc 2006, 48: 1539.
- Huang CF, Chang YH, Lee CH, Chuo HT, Yeh HD, Liang CT, Lin HH, Cheng HH, Hwang GJ: Insulator-quantum Hall conductor transitions at low magnetic field. Phys Rev B 2002, 65: 045303.View Article
- Wang Y-T, Kim G-H, Huang CF, Lo S-T, Chen W-J, Nicholls JT, Lin L-H, Ritchie DA, Chang YH, Liang C-T, Dolan BP: Probing temperature-driven flow lines in a gated two-dimensional electron gas with tunable spin-splitting. J Phys Condens Matter 2012, 24: 405801. 10.1088/0953-8984/24/40/405801View Article
- Hang DR, Liang C-T, Juang JR, Huang T-Y, Hung WK, Chen YF, Kim G-H, Lee J-H, Lee J-H: Electrically detected and microwave-modulated Shubnikov-de Haas oscillations in an Al0.4Ga0.6N/GaN heterostructure. J Appl Phys 2003, 93: 2055. 10.1063/1.1539286View Article
- Juang JR, Huang T-Y, Chen T-M, Lin M-G, Kim G-H, Lee Y, Liang C-T, Hang DR, Chen YF, Chyi J-I: Transport in a gated Al0.18Ga0.82N/GaN electron system. J Appl Phys 2003, 94: 3181. 10.1063/1.1594818View Article
- Cho KS, Huang T-Y, Huang CP, Chiu YH, Liang C-T, Chen YF, Lo I: Exchange-enhanced g-factors in an Al0.25Ga0.75N/GaN two-dimensional electron system. J Appl Phys 2004, 96: 7370. 10.1063/1.1815390View Article
- Cho KS, Liang C-T, Chen YF, Tang YQ, Shen B: Spin-dependent photocurrent induced by Rashba-type spin splitting in Al0.25Ga0.75N/GaN heterostructures. Phys Rev B 2007, 75: 085327.View Article
- Liang C-T, Simmons MY, Smith CG, Kim GH, Ritchie DA, Pepper M: Spin-dependent transport in a clean one-dimensional channel. Phys Rev B 1999, 60: 10687. 10.1103/PhysRevB.60.10687View Article
- Huckestein B: Quantum Hall effect at low magnetic fields. Phys Rev Lett 2000, 84: 3141. 10.1103/PhysRevLett.84.3141View Article
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.