The quantum scattering time and its implications on scattering sources in graphene

TL;DR

This study measures quantum scattering times in graphene, revealing the dominant role of surface charges in limiting mobility and providing insights into scattering sources affecting electronic properties.

Contribution

It offers a comprehensive analysis of scattering times in graphene and links scattering sources to surface charges affecting mobility.

Findings

Quantum scattering times range from 25 to 74 fs.

The ratio tau_t/tau_q varies between 1.5 and 5.1.

Surface charges on SiO_2 dominate scattering in current samples.

Abstract

We determine the quantum scattering time tau_q in six graphene samples with mobility of 4,400 < mu < 17,000 cm^2/Vs over a wide range of carrier density (1.2 < n < 6x10^{12}/cm^2). tau_q derived from Shubnikov-de Haas oscillations ranges ~25-74 fs, corresponding to a single-particle level broadening of 4.5-13 meV. The ratio of the transport to quantum scattering time tau_t/tau_q spans 1.5-5.1 in these samples, which can be quantitatively understood combining scattering from short-ranged centers and charged impurities located within 2 nm of the graphene sheet. Our results suggest that charges residing on the SiO_2 surface play a dominant role in limiting carrier mobility in current samples.