The transport properties of Dirac fermions in chemical vapour-deposited single-layer graphene

Abstract

The electronic transport properties of Dirac fermions in chemical vapour-deposited single-layer epitaxial graphene on anSiO 2 /Si substrate have been investigated using the Shubnikov-de Haas (SdH) oscillations technique. The magnetoresistance measurements were performed in the temperature range between 1.8 and 43 K and at magnetic fields up to 11 T. The 2D carrier density and the Fermi energy have been determined from the period of the SdH oscillations. In addition, the in-plane effective mass as well as the quantum lifetime of 2D carriers have been calculated from the temperature and magnetic field dependences of the SdH oscillation amplitude. The sheet carrier density (1.42 × 10 13 cm −2 at 1.8 K), obtained from the lowfield Hall Effect measurements, is larger than that of 2D carrier density (8.13 × 10 12 cm −2). On the other hand, the magnetoresistance includes strong magnetic field dependent positive, non-oscillatory background magnetoresistance. The strong magnetic field dependence of the magnetoresistance and the differences between sheet carrier and 2D carrier density can be attributed to the 3D carriers between the graphene sheet and the SiO 2 /Si substrate.

Low-temperature quantum magnetotransport of graphene on SiC (0 0 0 1) in pulsed magnetic fields up to 30 T

“…The value of T D µ = ħe/(πµ R k B m c ) ≈ 200 K coincides with T D within the error. Hence, the non-thermal broadening of the Landau levels is connected mainly to the short-range electron scattering, supporting the sufficiently high homogeneity of distribution of the electron concentration in our material and yielding the transport time τ ≈ 1.2 × 10 −14 s. It should be noted, that in graphene on SiO 2 and SiO 2 /Si substrates the ratio of T D /T D µ (or, equivalently, of the transport and the quantum time, respectively), has been observed within the interval of ~1.5-5.1 deviating substantially from unity [8,24]. Such deviations have been attributed to scattering from charged impurity residing within 2 nm of the graphene sheet, reflecting presumably an influence of the graphene/SiO 2 interface [24].…”

“…Hence, the temperature dependence of the resistivity in figure 3(a) should be analyzed with equation ( 6) at B = 0 and equation (8) with τ ϕt instead of τ ϕ. In turn, instead of equation (10a) we should use the expression…”

“…The experimental dependence of Δρ(T) in figure 3(a) has been fitted explicitly with the expression Δρ cal (T) = Δρ WL (T) + Δρ EEI (T) + Δρ CL (T). Here, Δρ WL (T) is calculated with equation (8) with τ ϕ substituted for τ ϕt , where the latter satisfies equation (10b), while the values of τ i and τ s are taken the same as those obtained in the MR analysis above. The function Δρ EEI (T) is obtained with equation ( 6) at B = 0, c = 3 and 7 at T < T i and T > T i , respectively (T i is marked in figure 3(a) with the vertical arrow), because T s ≈ 770 K exceeds considerably the investigated temperature range (see text below equation ( 6)).…”

“…The point is that the carrier mobility in these materials is much lower than in the mechanically deposited graphene layers, due to a high level of defects existing in the interface. Therefore, observations of the quantum effects in conductivity, such as the Shubnikov-de Haas (SdH) effect usually are much more problematic [8].…”

Переход между электронной локализацией и антилокализацией, а также проявление фазы Берри в графене на поверхности SiC

“…Наиболее перспективной технологией синтеза графена, которая позволяет получать высококачественный материал достаточно больших размеров и в то же время может быть интегрирована в промышленное производство, представляется термодеструкция поверхности полуизолирующих подложек карбида кремния (SiC). Такие структуры также достаточно хорошо изучены [4][5][6], однако полного понимания влияния интерфейсного слоя не существует. В частности, это связано с тем, что вследствие дефектного характера интерфейса подвижность носителей в таких структурах существенно меньше, чем в механически нанесенных монослоях графена.…”