Strongly temperature dependent resistance of meander-patterned graphene

Abstract

We have studied the electronic properties of epitaxial graphene devices patterned in a meander shape with the length up to a few centimeters and the width of few tens of microns. These samples show a pronounced dependence of the resistance on temperature. Accurate comparison with theory shows that this temperature dependence originates from the weak localization effect observed over a broad temperature range from 1.5 K up to 77 K. The comparison allows us to estimate the characteristic times related to quantum interference. In addition, a large resistance enhancement with temperature is observed at the quantum Hall regime near the filling factor of 2. Record high resistance and its strong temperature dependence are favorable for the construction of bolometric photodetectors.Due to its unique properties, graphene is a promising material for constructing emitters and detectors of different frequency, including poorly developed terahertz (THz) range. THz hot electron bolometers, operating at cryogenic temperatures, were made of monolayer [1][2][3] and bilayer graphene. [4,5] However, the resistance of graphene typically depends weakly on the electron temperature, which is an obstacle to the creation of graphene-based devices with high efficiency. Recently, successful observation of bolometric signal in graphene was achieved in highly resistive samples of two different types: either in a strongly disordered graphene [6] or in a patterned sample. [7,8] In particular, epitaxial graphene on SiC patterned in a meander shape has been reported to demonstrate good performance in the terahertz region (1-3 THz). [7] In this paper we present magnetotransport studies of meander shaped samples with the ratio of the sample length to width exceeding 600. We show that without or at weak magnetic fields strong temperature dependence of the resistance up to 70 K is related to weak localization effect. [9][10][11][12][13][14] We investigate this effect in a wide range of temperatures and magnetic fields and find that our data are perfectly fitted by theory.[11] The times of dephasing, intra-valley and inter-valley scattering are obtained from the fitting. Another area of strong temperature dependence of the resistance is found in the quantum Hall regime at magnetic fields with the filling factor being equal to 2, where the longitudinal resistance is zero. The observed large temperature coefficient of the resistance in graphene near the integer QHE may be used to realize a photoresponse mechanisms related to optically induced breakdown of the quantum Hall effect.[15] These effects were investigated and confirmed in semiconductor heterostructures, but, until now, studies of graphene samples with a large ratio of length to width L/W have not been carried out.The graphene samples were obtained by sublimation at the Si face of a 4H-SiC substrate by thermal decomposition in an argon atmosphere. Raman spectroscopy shows that graphene is a monolayer with high quality. Using laser lithography, samples were patterned in meander shaped Hall dev...