M. Samadashvili

Bio: M. Samadashvili is an academic researcher from Lawrence Berkeley National Laboratory. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Atomic structures and electronic properties of Ni or N modified Cu/diamond interface.

Abstract: The interfacial stability of copper/diamond directly affects its mechanical properties and thermal conductivity. The atomic structures and electronic properties of Cu/diamond and Cu/X/diamond interfaces have been identified to investigate the effect of interfacial additive X (X = Ni or N) on the low-index interfacial adhesion of copper/diamond composites. For unmodified composites, the interfacial stability decreases in the order of Cu(001)/diamond(001) > Cu(111)/diamond(111) > Cu(011)/diamond(011). The metallic interfacial additive Ni is found to enhance the Cu(011)/diamond(011) interfacial stability and exchange the interfacial stability sequence of (011) and (111) composites. The nonmetallic element N will promote the stability of Cu(111)/diamond(111) but not alter the stability order of the composites at different interface. To explain the origin of interfacial stability, a series of analyses on atomic structures and electronic properties have been carried out, including the identification of the type of formed interfacial boundary, the measurement of interfacial bond lengths, and the calculations of density of states, bond populations, and atomic charge. The stability of the interface is found to be related to the type of formed interfacial boundary and bond, the interfacial bond populations, and the interfacial bond numbers. The LPDOS reveals that all of the considered interfaces exhibit metallic character. The interfacial Ni additive is found to be an electron donor contributing the electrons to its bonded Cu and C atoms while interfacial N atom is an electron acceptor where it mainly accepts the electrons from its bonded Cu and C.

Identification of an AgS2 Complex on Ag(110).

Abstract: Adsorbed sulfur has been investigated on the Ag(110) surface at two different coverages, 0.02 and 0.25 monolayers. At the lower coverage, only sulfur adatoms are present. At the higher coverage, there are additional bright features which we identify as linear, independent AgS2 complexes. This identification is based upon density functional theory (DFT) and its comparison with experimental observations including bias dependence and separation between complexes. DFT also predicts the absence of AgS2 complexes at low coverage, and the development of AgS2 complexes around a coverage of 0.25 monolayers of sulfur, as is experimentally observed. To our knowledge, this is the first example of an isolated linear sulfur-metal-sulfur complex.

Investigations of sulfur-silver interactions and mass transport on silver and gold surfaces

Abstract: .................................................................................................................................. vi CHAPTER 1. GENERAL INTRODUCTION ............................................................................... 1 1. Motivation ............................................................................................................................... 1 1.1 Coinage metals ................................................................................................................ 2 1.2 Metal-sulfur complexes ..................................................................................................... 2 2. Experimental details and methods........................................................................................... 3 2.1 Equipment .......................................................................................................................... 3 2.2 Sample materials................................................................................................................ 6 2.3 Data analysis ...................................................................................................................... 9 3. Dissertation organization....................................................................................................... 10 4. References ............................................................................................................................. 11 CHAPTER 2. CHARACTERISTICS OF SULFUR ATOMS ADSORBED ON Ag(100), Ag(110), AND Ag(111) AS PROBED WITH SCANNING TUNNELING MICROSCOPY: EXPERIMENT AND THEORY .................................................................................................. 17 1. Abstract ................................................................................................................................. 17 2. Introduction ........................................................................................................................... 18 3. Methods ................................................................................................................................. 20 3.1 Experimental details ........................................................................................................ 20 3.2 Computational methodology ........................................................................................... 21 4. Experimental results .............................................................................................................. 27 4.1 S/Ag(100): STM results ................................................................................................... 27 4.2 S/Ag(110): STM results ................................................................................................... 30 5. DFT results ............................................................................................................................ 31 5.1. S/Ag(100): DFT results .................................................................................................. 32 5.2. S/Ag(110): DFT results .................................................................................................. 37 5.3. S/Ag(111): DFT results .................................................................................................. 38 6. Discussion ............................................................................................................................. 39 7. Conclusions ........................................................................................................................... 43 8. References ............................................................................................................................. 44 9. Acknowledgements ............................................................................................................... 48 10. Appendix 1: Coverage dependence of S/Ag(100)............................................................... 49 11. Appendix 2: STM tunneling conditions .............................................................................. 57