High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure, Composition and Mobility During Catalytic Reactions on A Model SingleCrystal PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure, Composition and Mobility During Catalytic Reactions on A Model SingleCrystal PDF full book. Access full book title High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure, Composition and Mobility During Catalytic Reactions on A Model SingleCrystal by M. O. Montano. Download full books in PDF and EPUB format.
Author: M. O. Montano
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.
Author: M. O. Montano
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.
Author: David Chi-Wai Tang
Publisher:
ISBN:
Category :
Languages : en
Pages : 562
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 277
Get Book Here
Book Description
The aim of the work presented therein is to take advantage of scanning tunneling microscope’s (STM) capability for operation under a variety of environments under real time and at atomic resolution to monitor adsorbate structures and mobility under high pressures, as well as to design a new generation of STM systems that allow imaging in situ at both higher pressures (35 atm) and temperatures (350 °C).
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 854
Get Book Here
Book Description
Author: Kevin Shao-Lin Hwang
Publisher:
ISBN:
Category :
Languages : en
Pages : 272
Get Book Here
Book Description
Author: Keith Benton Rider
Publisher:
ISBN:
Category :
Languages : en
Pages : 310
Get Book Here
Book Description
Author: Dimitri B. Skliar
Publisher: ProQuest
ISBN: 9780549924609
Category : Scanning tunneling microscopy
Languages : en
Pages :
Get Book Here
Book Description
The understanding of the chemistry of silicon surfaces has been one of the major contributors in development and improvement of silicon based microelectronic devices in the past several decades. Progressively, the dimensions of devices have reduced by several orders of magnitude, presently at the length scale of few tens of nanometers, and are expected to decrease in size even more. For chemistry based film growth methods such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), control of film structure and composition in this spatial regime requires a very detailed nanoscopic understanding of silicon surface chemistry. A combined experimental and theoretical approach, utilizing ultra high vacuum scanning tunneling microscopy (UHV-STM) and density functional theory (DFT), to understanding the surface chemistry of Si(100) is illustrated in the context of ALD development for high dielectric constant metal oxides. As a first possible route to controllably deposit monolayer thick metal layer, the reaction of the metal-organic molecule with bare silicon surface is considered. The interaction of the protonated b-diketonate ligand, 2,2,6,6-tetramethyl-3,5-heptanedione (dpmH), which is a byproduct of the strontium metal-organic precursor vaporization, with Si(100)-2x1 surface is investigated. Two aspects of the molecule's interactions were addressed: the adsorption at room temperature as well as its thermal decomposition. By combination of the experiments with DFT calculations of adsorbate geometry, STM image simulations, and reaction pathways it was possible to propose unique binding configurations that match the experimentally observed adsorption features. Theoretical analysis of multiple competing reaction pathways showed that hydroxyl dissociation via a 1,7 H-shift mechanism is the dominant adsorption pathway. Several other pathways including [2+4] addition, [2+2] C=O intra-dimer addition, [2+2] C=O intra-dimer addition with OH dissociation on an adjacent dimer, [2+2] C=C intra-dimer addition, and "ene" addition are found to be barrierless with respect to the entrance channel, and have small barriers relative to a hypothesized adsorption precursor intermediate. Pathways involving 1,3 and 1,2 intra-molecular H-shifts are found to be highly activated and are expected to be inaccessible at room temperature. Several state inter-conversions are found to be unlikely as well. These results provide insight to the competitive adsorption pathways for multifunctional molecules on silicon. Investigations of thermally induced decomposition of adsorbed dpmH molecules showed that there are no significant products of desorption of carbon containing fragments of the molecule, i.e. most of the carbon atoms incorporate into the silicon surface causing it to reconstruct to a c(4x4) phase at exposures below ~ 0.15 L. At higher exposures formation of SiC islands is observed. These findings demonstrate that schemes to deposit materials from organometallic compounds containing b-diketone ligands onto clean Si(100)-2x1 surface cannot result in an ordered interfacial structure as carbon incorporation into the substrate is inevitable. An alternative strategy for depositing metal template layer is proposed, where the initial reacting surface will be terminated by water at room temperature. The stability of surface hydroxyl groups and mechanisms of their decomposition in 300-600K temperature range are analyzed. It is found that surface oxidation does not follow first order kinetics with respect to the hydroxyl groups. DFT calculations of oxygen insertion pathways point towards a catalytic effect of the dangling bonds and suggest that in the 500-550K range the insertion events should occur predominantly next to unoccupied surface silicon sites. A model is proposed, where diffusing dangling bonds act as moving catalysts for hydroxyl group decomposition. Kinetic Monte Carlo (kMC) simulations are used to compare the results of this model with experimental data. A strategy to increase hydroxyl group stability is demonstrated where the initial concentration of surface dangling bonds is decreased by water termination at 130K.
Author: Frederick Michael Leibsle
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
Get Book Here
Book Description
Scanning tunneling microscopy (STM), photoemission spectroscopy, and a variety of other experimental techniques have been used to examine both the initial stages of interface formation between various adsorbates, as well as, reconstructions occurring on the clean surfaces of Si and Ge. The initial stages of oxidation of the Si(111)-(7 x 7) and Ge(111)-c(2 x 8) surfaces were studied. Images of the same area of each surface were obtained from various exposures of oxygen. On the Si(111)-(7 x 7) surface, the results show that defect sites act as nucleation centers for the oxidation process. On the Ge(111)-c(2 x 8) surface, images of the surface for exposures of oxygen up to 1600 Langmuirs were obtained. The results show that the oxidized portions of the surface grow as islands which expand preferentially in the (112) direction. The "16 structure" and c(8 x 10) reconstructions occurring on the clean Ge(110) surfaces were examined. STM images show that the Ge(110)-"16 structure" reconstructed surface is composed of ordered facets as predicted by a low-energy-electron diffraction study. STM images of the Ge(110)-c(8 x 10) surface show that the unit cell is composed of alternating oblique sub-unit cells. Photoemission spectra of the Ge 3d core levels for both these surfaces show the presence of multiple surface-shifted components. Sb deposition on these surfaces has also been studied. Sb deposition results in the formation of a (1 x 1) or (3 x 2) ordered over-layer depending on the substrate temperature and Sb coverage. Both these surfaces have been observed with STM. Photoemission results for various coverages of Sb show that the surface-shifted components of the Ge 3d core level are suppressed by the deposition of Sb. A structural model, consistent with the data, for the (1 x 1) Sb-terminated surface is presented. Angle-resolved photoemission spectroscopy was used to measure the bulk band-dispersion relations along the high symmetry $Gamma$-$Sigma$-X directions for both Ge and Si.
Author: Yong Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 442
Get Book Here
Book Description
Author: David Mark Zeglinski
Publisher:
ISBN:
Category :
Languages : en
Pages : 292
Get Book Here
Book Description
