Contact-independent measurement of electrical conductance of a thin film with a nanoscale sensor.

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.

[1]  Zhenan Bao,et al.  Organic Field-Effect Transistors , 2007 .

[2]  David Cahen,et al.  Comparison of Electronic Transport Measurements on Organic Molecules , 2003 .

[3]  Michael S. Shur,et al.  An experimental study of contact effects in organic thin film transistors , 2006 .

[4]  V. V. Bryksin,et al.  Hopping Conduction in Solids , 1985 .

[5]  G. Nelles,et al.  Efficient electronic coupling and improved stability with dithiocarbamate-based molecular junctions. , 2010, Nature nanotechnology.

[6]  Gilles Horowitz,et al.  Organic Field‐Effect Transistors , 1998 .

[7]  J. W. Osmun.  Electron tunneling into amorphous germanium , 1970 .

[8]  The effect of electrostatic screening on a nanometer scale electrometer. , 2010, Nano letters.

[9]  E. Abrahams,et al.  Impurity Conduction at Low Concentrations , 1960 .

[10]  T. M. Donovan,et al.  Thickness Dependence of Hopping Transport in Amorphous-Ge Films , 1973 .

[11]  Measuring charge transport in a thin solid film using charge sensing. , 2009, Nano letters.

[12]  R. Howard,et al.  Discrete Resistance Switching in Submicrometer Silicon Inversion Layers: Individual Interface Traps and Low-Frequency ( 1 f ?) Noise , 1984 .

[13]  H. Rubahn,et al.  Interface controlled organic thin films , 2009 .

[14]  Zhenan Bao,et al.  Contact engineering for organic semiconductor devices via Fermi level depinning at the metal-organic interface , 2010 .

[15]  G. Schmid.  The Nature of Nanotechnology , 2010 .

[16]  Nevill Mott,et al.  Conduction in glasses containing transition metal ions , 1968 .

[17]  F. Xia,et al.  The origins and limits of metal-graphene junction resistance. , 2011, Nature nanotechnology.

[18]  Bishop,et al.  Aperiodic magnetoresistance oscillations in narrow inversion layers in Si. , 1985, Physical review letters.

[19]  John A. Rogers,et al.  Contact resistance in organic transistors that use source and drain electrodes formed by soft contact lamination , 2003 .

[20]  Stephen D. Senturia,et al.  The charge-flow transistor - A new MOS device. [for integrated sensor applications] , 1977 .

[21]  O. Seitz,et al.  Electronic Contact Deposition onto Organic Molecular Monolayers: Can We Detect Metal Penetration? , 2010 .

[22]  D. Cahen,et al.  Nondestructive Contact Deposition for Molecular Electronics: Si-Alkyl//Au Junctions , 2010 .