Measuring Charge Transport in a Thin Solid Film Using Charge Sensing

Abstract

We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using a nanometer scale silicon MOSFET as a charge sensor. This charge detection technique makes possible the measurement of extremely large resistances. At high temperatures, where the a-Si:H resistance is not too large, the charge detection measurement agrees with a direct measurement of current. The device geometry allows us to probe both the field effect and dispersive transport in the a-Si:H using charge sensing and to extract the density of states near the Fermi energy.

The Effect of Electrostatic Screening on a Nanometer Scale Electrometer

“…1 are acquired. At this temperature, the a-Si:H is so resistive that it does not charge up on the time scale of the experiment [9], so that we can add charge to the a-Si:H gold contacts but not to the a-Si:H itself. The results are shown in Fig.…”

Measuring Ligand-Dependent Transport in Nanopatterned PbS Colloidal Quantum Dot Arrays Using Charge Sensing

“…This method has been previously used to study transport in highly resistive nanopatterned films of amorphous silicon 27 and amorphous germanium. 28 The method has also been shown to be insensitive to contact effects such as blocking contacts.…”

“…As we apply a negative voltage step to the gold electrode connected to the nanopattern, we observe an instantaneous jump in the MOSFET conductance followed by a further decrease slowly with time (which we call the charge transient). The time dependence of the charging transient from the nanopattern has been shown to be accurately exponential, 27 and the resistance of the nanopattern can be extracted from an exponential fit to this transient response. The voltage step and the transient response of the MOSFET are shown in Figure 1b.…”

Contact-Independent Measurement of Electrical Conductance of a Thin Film with a Nanoscale Sensor

“…al. 9 When a resistive film with a distributed capacitance is subject to an electric field in a direction parallel to the surface, charge diffuses through the film with a diffusion constant of D = 1/R sq C where R sq is the resistance per square and C is the capacitance per unit area of the film. By solving the diffusion equation for this system, it is found that the charge per unit area at any point in the film varies with time according to σ(t) ≈ σ 0 + Aexp(−Γt) where Γ = π 2 D/L 2 , L is the length of the film, and D is the diffusion constant.…”