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

Abstract

Contact effects are a common impediment to electrical measurements throughout the fields of nanoelectronics, organic electronics, and the emerging field of graphene electronics. We demonstrate a novel method of measuring electrical conductance in a thin film of amorphous germanium that is insensitive to contact effects. The measurement is based on the capacitive coupling of a nanoscale metal-oxide-semiconductor field-effect transistor (MOSFET) to the thin film so that the MOSFET senses charge diffusion in the film. We tune the contact resistance between the film and contact electrodes and show that our measurement is unaffected. With the MOSFET, we measure the temperature and field dependence of the conductance of the amorphous germanium, which are fit to a model of variable-range hopping. The device structure enables both a contact-independent and a conventional, contact-dependent measurement, which makes it possible to discern the effect of the contacts in the latter measurement. This measurement method can be used for reliable electrical characterization of new materials and to determine the effect of contacts on conventional electron transport measurements, thus guiding the choice of optimal contact materials.

Tuning the Electronic and Magnetic Properties of CuAlO2 Nanocrystals Using Magnetic Dopants

“…21 Localization lengths of the order of ∼1 nm are typically reported for amorphous Ge-based semiconductors. 22 For our larger nanocrystals, we estimate the localization length directly from the Wentzel–Kramers–Brillouin expression of the tunneling probability, a = 2ℏ/ m * E b , where m * is the effective mass of the charge carrier and E b is the barrier height. We look at two extreme cases of the barrier height.…”

“…However, there exists some scatter in the literature for the value of localization length, and length scales much smaller than the dot radius have been reported for ZnO nanocrystals . Localization lengths of the order of ∼1 nm are typically reported for amorphous Ge-based semiconductors . For our larger nanocrystals, we estimate the localization length directly from the Wentzel–Kramers–Brillouin expression of the tunneling probability, a = 2ℏ/ m * E b , where m * is the effective mass of the charge carrier and E b is the barrier height.…”

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. 28 We use a nanopatterning technique developed for colloidal dots 29 to integrate a charge sensor with the array of dots and fabricate the necessary devices.…”

“…28 The method has also been shown to be insensitive to contact effects such as blocking contacts. 28 We use a nanopatterning technique developed for colloidal dots 29 to integrate a charge sensor with the array of dots and fabricate the necessary devices. Nanopatterning also helps to minimize cracks and clusters in the array resulting in more conducting arrays and can be used to make samples whose dimensions approach the short ordering length scales of the dots.…”

“…In this Letter, we introduce a novel technique to study transport in weakly coupled PbS QD arrays, based on a time-resolved measurement of charge using a nanoscale charge sensor. This method has been previously used to study transport in highly resistive nanopatterned films of amorphous silicon and amorphous germanium . The method has also been shown to be insensitive to contact effects such as blocking contacts .…”