Playing Catch with Electrons: A Dynamic Metaphor for Chemical Bonding with an Extension of the Tunneling Model to Gas-Phase Molecules.

Quantum mechanical electron tunneling is explored as the mediator of chemical bonding. Three topics are addressed. First, a baseball game-of-catch metaphor is employed to elucidate the physics of chemical bonding.

Chemical Bonding with or without Tunneling.

A solid-state tunneling analysis is performed in order to assess whether a given chemical bond type is mediated by quantum mechanical electron tunneling. Four bond types are found to involve tunneling-covalent, ionic, polar covalent, and transition metal bonding. Two bond types do not rely on tunneling-free electron metal and van der Waals bonding.

New Perspective on Hydrogen Bonding.

A new model is proposed for hydrogen bonding in which an intermediate hydrogen atom acts as a bridge bond connecting two adjacent atoms, X and A, via quantum mechanical tunneling of the hydrogen electron. A strong hydrogen bond (X-H-A) is formed when the X-H and H-A interatomic distances are short and symmetric, thereby facilitating intense electron tunneling to and from both adjacent atoms. The hydrogen bond weakens (X-H···A) as the H···A interatomic distance lengthens compared to that of X-H since the H···A tunneling intensity degrades exponentially with increasing distance.

Bonding and Tunneling.

Quantum mechanical electron tunneling is proposed as the mediator of chemical bonding. Covalent, ionic, and polar covalent bonds all rely on quantum mechanical tunneling, but the nature of tunneling differs for each bond type. Covalent bonding involves bidirectional tunneling across a symmetric energy barrier.

Demonstration of Fowler-Nordheim Tunneling in Simple Solution-Processed Thin Films.

The production of high-quality thin-film insulators is essential to develop advanced technologies based on electron tunneling. Current insulator deposition methods, however, suffer from a variety of limitations, including constrained substrate sizes, limited materials options, and complexity of patterning. Here, we report the deposition of large-area AlO films by a solution process and its integration in metal-insulator-metal devices that exhibit I- V signatures of Fowler-Nordheim electron tunneling.

Structural convergence properties of amorphous InGaZnO from simulated liquid-quench methods.

The study of structural properties of amorphous structures is complicated by the lack of long-range order and necessitates the use of both cutting-edge computer modeling and experimental techniques. With regards to the computer modeling, many questions on convergence arise when trying to assess the accuracy of a simulated system. What cell size maximizes the accuracy while remaining computationally efficient? More importantly, does averaging multiple smaller cells adequately describe features found in bulk amorphous materials? How small is too small? The aims of this work are: (1) to report a newly developed set of pair potentials for InGaZnO and (2) to explore the effects of structural parameters such as simulation cell size and numbers on the structural convergence of amorphous InGaZnO.

Lanthanum aluminum oxide thin-film dielectrics from aqueous solution.

Amorphous LaAlO3 dielectric thin films were fabricated via solution processing from inorganic nitrate precursors. Precursor solutions contained soluble oligomeric metal-hydroxyl and/or -oxo species as evidenced by dynamic light scattering (DLS) and Raman spectroscopy. Thin-film formation was characterized as a function of annealing temperature using Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and an array of electrical measurements.

Atomic solid state energy scale.

A plot of electron affinity (EA) and ionization potential (IP) versus energy band gap (E(G)) for 69 binary closed-shell inorganic semiconductors and insulators reveals that E(G) is centered about the hydrogen donor/acceptor ionization energy ε(+/-). Thus, ε(+/-), or equivalently the standard hydrogen electrode (SHE) energy, functions as an absolute energy reference, determining the tendency of an atom to be either a cation or anion in a compound. This empirical trend establishes the basis for defining a new solid state energy (SSE) scale.

Aqueous inorganic inks for low-temperature fabrication of ZnO TFTs.

A simple, low-cost, and nontoxic aqueous ink chemistry is described for digital printing of ZnO films. Selective design through controlled precipitation, purification, and dissolution affords an aqueous Zn(OH)(x)(NH(3))(y)((2-x)+) solution that is stable in storage, yet promptly decomposes at temperatures below 150 degrees C to form wurtzite ZnO. Dense, high-quality, polycrystalline ZnO films are deposited by ink-jet printing and spin-coating, and film structure is elucidated via X-ray diffraction and electron microscopy.