Molecular control over Au/GaAs diodes

Abstract

The use of molecules to control electron transport is an interesting possibility, not least because of the anticipated role of molecules in future electronic devices. But physical implementations using discrete molecules are neither conceptually simple nor technically straightforward (difficulties arise in connecting the molecules to the macroscopic environment). But the use of molecules in electronic devices is not limited to single molecules, molecular wires or bulk material. Here we demonstrate that molecules can control the electrical characteristics of conventional metal-semiconductor junctions, apparently without the need for electrons to be transferred onto and through the molecules. We modify diodes by adsorbing small molecules onto single crystals of n-type GaAs semiconductor. Gold contacts were deposited onto the modified surface, using a 'soft' method to avoid damaging the molecules. By using a series of multifunctional molecules whose dipole is varied systematically, we produce diodes with an effective barrier height that is tuned by the molecule's dipole moment. These barrier heights correlate well with the change in work function of the GaAs surface after molecular modification. This behaviour is consistent with that of unmodified metal-semiconductor diodes, in which the barrier height can depend on the metal's work function.

Molecules on Si: Electronics with Chemistry

“…[64] Such molecules are expected to conduct much better than alkyl monolayers. MOMS research, though, is mostly limited to simple alkanes.…”

“…(1)), the same cannot be said about the critical role of interface dipoles that form upon bonding at any inorganic interface [13,14] and act to minimize C SC by Le Chatelier's principle (negative feedback). [13,14] We [3,64,109,110] and others [63,[111][112][113] have shown that adsorbing molecules with intrinsic dipoles and/or polar bonding to a solid can change the barrier height for transport in an MS/MIS junction. The theoretical potential drop, C I , can be calculated from: [114,115] .…”

“…The reason is that a strong dipole effect is commonly achieved by the terminal groups of the molecules, [17,53,63,114,119] which are the ones most likely to interact with the deposited metal contact, via polarization or even charge transfer (i.e., change of m Me/Hg ). [49,64] One way to study the effect of such direct interactions is to add a second monolayer on the metal side as a dipolar [109] or blocking [120] layer.…”

“…Still, the TE model is commonly assumed as a simple means for comparing samples/ data, using an ''effective barrier height'' that is deduced from J-V measurements, SBH(J 0 ). [19,56,63,64,88,90,135] Alternatively, the barrier height can be extracted from reverse bias C-V data with the MottÀSchottky relation (see Eq. (4), SBH(C 0 ) ¼ C SC þ j).…”

Molecular interfaces for plasmonic hot electron photovoltaics

“…Instead, a more versatile approach can be envisaged through the exploitation of molecular species in self assembled monolayers. 27 Molecules, unlike inorganic wide bandgap semiconductors, possess a plurality of structural parameters that can be tuned in these systems: the length of the molecule, the conjugated or aliphatic character and the end-functional groups that serve to strongly bind on a given surface and passivate electronic defect states. [27][28][29][30][31][32][33][34][35] Not to exclude also their solution processability which is a significantly lower cost manufacturing process compared to atomic layer deposition.…”