Matching Items (2)
Description
In this work, a new method, "Nanobonding" [1,2] is conceived and researched to bond Si-based surfaces, via nucleation and growth of a 2 D silicon oxide SiOxHx interphase connecting the surfaces at the nanoscale across macroscopic domains. Nanobonding cross-bridges two smooth surfaces put into mechanical contact in an O2/H2O mixed ambient below T <200 °C via arrays of SiOxHx molecules connecting into a continuous macroscopic bonding interphase. Nano-scale surface planarization via wet chemical processing and new spin technology are compared via Tapping Mode Atomic Force Microscopy (TMAFM) , before and after nano-bonding. Nanobonding uses precursor phases, 2D nano-films of beta-cristobalite (beta-c) SiO2, nucleated on Si(100) via the Herbots-Atluri (H-A) method [1]. beta-c SiO2 on Si(100) is ordered and flat with atomic terraces over 20 nm wide, well above 2 nm found in native oxides. When contacted with SiO2 this ultra-smooth nanophase can nucleate and grow domains with cross-bridging molecular strands of hydroxylated SiOx, instead of point contacts. The high density of molecular bonds across extended terraces forms a strong bond between Si-based substrates, nano- bonding [2] the Si and silica. A new model of beta-cristobalite SiO2 with its <110> axis aligned along Si[100] direction is simulated via ab-initio methods in a nano-bonded stack with beta-c SiO2 in contact with amorphous SiO2 (a-SiO2), modelling cross-bridging molecular bonds between beta-c SiO2 on Si(100) and a-SiO2 as during nanobonding. Computed total energies are compared with those found for Si(100) and a-SiO2 and show that the presence of two lattice cells of !-c SiO2 on Si(100) and a-SiO2 lowers energy when compared to Si(100)/ a-SiO2 Shadow cone calculations on three models of beta-c SiO2 on Si(100) are compared with Ion Beam Analysis of H-A processed Si(100). Total surface energy measurements via 3 liquid contact angle analysis of Si(100) after H-A method processing are also compared. By combining nanobonding experiments, TMAFM results, surface energy data, and ab-initio calculations, an atomistic model is derived and nanobonding is optimized. [1] US Patent 6,613,677 (9/2/03), 7,851,365 (12/14/10), [2] Patent Filed: 4/30/09, 10/1/2011
ContributorsWhaley, Shawn D (Author) / Culbertson, Robert J. (Thesis advisor) / Herbots, Nicole (Committee member) / Rez, Peter (Committee member) / Marzke, Robert F (Committee member) / Lindsay, Stuart (Committee member) / Chamberlin, Ralph V (Committee member) / Arizona State University (Publisher)
Created2011
Description
Cubic boron nitride (c-BN), hexagonal boron nitride (h-BN), and semiconducting diamond all have physical properties that make them ideal materials for applications in high power and high frequency electronics, as well as radiation detectors. However, there is limited research on the unique properties and growth of c-BN or h-BN thin films. This dissertation addresses the deposition of c-BN via plasma enhanced chemical vapor deposition (PECVD) on boron doped diamond substrates. In-Situ X-ray photoelectron spectroscopy (XPS) is used to characterize the thickness and hexagonal to cubic ratio of boron nitride thin films. The effects of hydrogen concentration during the deposition of boron nitride are investigated. The boron nitride deposition rate is found to be dependent on the hydrogen gas flow. The sp2 to sp3 bonding is also found to be dependent on the hydrogen gas flow. Preferential growth of h-BN is observed when an excess of hydrogen is supplied to the reaction, while h-BN growth is suppressed when hydrogen flow is reduced to be the limiting reactant. Reduced hydrogen flow is also observed to promote preferential growth of c-BN.
The hydrogen limited reaction is used to deposit c-BN on single crystal (100) boron-doped diamond substrates. In-situ ultra-violet photoelectron spectroscopy (UPS) and XPS are used to deduce the valence band offset of the diamond/c-BN interface. A valence band offset of -0.3 eV is measured with the diamond VBM above the VBM of c-BN. This value is then discussed in context of previous experimental results and theoretical calculations.
Finally, UPS and XPS are used to characterize the surface states of phosphorus-doped diamond. Variations within the processing parameters for surface preparation and the effects on the electronic surface states are presented and discussed.
ContributorsBrown, Jesse (Author) / Nemanich, Robert J (Thesis advisor) / Alarcon, Ricardo (Committee member) / Lindsay, Stuart (Committee member) / Zaniewski, Anna (Committee member) / Arizona State University (Publisher)
Created2021