Effect of Gate Voltage on the Transport Properties in Thin Crystalline Graphite Films

Effect of Gate Voltage on the Transport Properties in Thin Crystalline Graphite Films

Graphite films are deposited on top of Si substrates from natural graphite by using mechanical exfoliation. The carrier type alternation has been confirmed by observing the Hall coefficient as a function of back gate voltage to the Si substrate. The electrons and the holes coexist at the back gate voltage (V_g) corresponding to the charge neutrality point, where the mobility and the mean free path show broad minima. The mean free time and the phase coherence time show a strong dependence on V_g. A weak localization effect is also found in the magnetoresistivity at low temperatures. However, a fit to the weak localization effect model reveals a deviation from the theoretical prefactor in the model equation for a 2-dimensional system. The weak localization effect is weakened quickly as the temperature rises above 10 K.

Graphite films are deposited on top of Si substrates from natural graphite by using mechanical exfoliation. The carrier type alternation has been confirmed by observing the Hall coefficient as a function of back gate voltage to the Si substrate. The electrons and the holes coexist at the back gate voltage (V_g) corresponding to the charge neutrality point, where the mobility and the mean free path show broad minima. The mean free time and the phase coherence time show a strong dependence on V_g. A weak localization effect is also found in the magnetoresistivity at low temperatures. However, a fit to the weak localization effect model reveals a deviation from the theoretical prefactor in the model equation for a 2-dimensional system. The weak localization effect is weakened quickly as the temperature rises above 10 K.