Measuring Charge Transport in a Thin Solid Film Using Charge Sensing

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