Search for: All records

Charge transport in ferroelectric (FE) gated graphene far from the Dirac point (DP) was studied in the temperature range 300 K < T < 350 K. A non-monotonic/monotonic/non-monotonic behavior in the conductivity [σ(T)] was observed as one moved away from the DP. As the gate polarization increased, additional impurity charges were compensated, which reduced charge scattering. The uncompensated charges doped graphene and σ(T) switched to a monotonic increase with increasing T. However, far from the DP, the polarization reached saturation, which resulted in still lower impurity charge scattering. The carrier concentration increased, and a non-monotonic response in σ(T) reappeared, which was attributed to phonon scattering. A theoretical model is presented that combined impurity charge and phonon scattering conduction mechanisms. The top gate polarizable FE provided a novel approach to investigate charge transport in graphene via controlled compensation of impurity charges, and in the process revealed non-monotonic behavior in σ(T) not previously seen in SiO2 back gated graphene devices. 

Charge transport near the Dirac point (DP) was investigated in graphene using ferroelectric (FE) gating in the temperature range of 300 < T < 350 K. We observed that the conductivity (σ) near the DP had a positive temperature gradient that switched to a negative temperature gradient with increasing temperature. The switch to a negative temperature gradient shifted to higher temperatures and gradually weakened upon moving away from the DP. Impurity charge compensation via polarization of the FE together with a temperature-dependent graphene–impurity charge separation was proposed as being responsible for the non-monotonicity in σ(T). A self-consistent theory for graphene transport with impurity charge scattering and phonon scattering was used to analyze the results. Non-monotonic charge transport was also observed in the temperature dependence of the residual conductivity (σr). Theoretical analysis of both σ and σr revealed a temperature independent contribution of ∼1.16e2h that is probably inherent to pristine graphene. 

Abstract The large‐scale growth of semiconducting thin films on insulating substrates enables batch fabrication of atomically thin electronic and optoelectronic devices and circuits without film transfer. Here an efficient method to achieve rapid growth of large‐area monolayer MoSe₂films based on spin coating of Mo precursor and assisted by NaCl is reported. Uniform monolayer MoSe₂films up to a few inches in size are obtained within a short growth time of 5 min. The as‐grown monolayer MoSe₂films are of high quality with large grain size (up to 120 µm). Arrays of field‐effect transistors are fabricated from the MoSe₂films through a photolithographic process; the devices exhibit high carrier mobility of ≈27.6 cm²V^–1s^–1and on/off ratios of ≈10⁵. The findings provide insight into the batch production of uniform thin transition metal dichalcogenide films and promote their large‐scale applications.