Bulletin of the American Physical Society
2005 TSAPS/AAPT/SPS Joint Fall Meeting
Thursday–Saturday, October 20–22, 2005; Houston, TX
Session B5: Computational I |
Hide Abstracts |
Room: Waldorf Astoria Main 210M |
Friday, October 21, 2005 2:00PM - 2:12PM |
B5.00001: Electronic structure and Schottky-barrier height of Si/PtSi interface Manish Niranjan, Stefan Zollner, Leonard Kleinman, Alex Demkov With the use of silicides in CMOS devices, the sheet and contact resistances in source/drain regions are greatly reduced, which eventually causes the device speed increase. However, for the ultra-scaled devices, the serial contact resistance coming from relatively high Schottky-barrier between Si in the source/drain regions and the metallic contact is expected to amount to one-fourth of the total parasitic resistance. This contribution will clearly only rise as the scaling continues. Over the past two decades, Titanium disilicide (TiSi$_{2})$ has become the preferred silicide in integrated circuit manufacturing. However, the sheet resistance of TiSi$_{2}$ increases significantly as one of the device dimensions is reduced. In deep submicron regime, PtSi and NiSi have been shown to be prospective candidates for replacing conventional silicides. PtSi has relatively low Schottky-barrier on Si (001) and its structural and electronic properties are less sensitive to lateral dimensions. We have performed density functional calculations of work functions and surface energies of PtSi for different surface orientations and calculated Schottky-barrier height of Si/PtSi interface. We have also studied the effects of Boron doping in PtSi on its electronic structure and Si/PtSi Schottky-barrier. Our results are consistent with the existing experimental results. Finally, we discuss how Boron doping in PtSi may improve its metallic character and influence Si/PtSi Schottky-barrier height. [Preview Abstract] |
Friday, October 21, 2005 2:12PM - 2:24PM |
B5.00002: Pressure-Induce phase transition of ZnS Israel Martinez, Murat Durandurdu We study the pressure-induced phase transition of ZnS using an ab initio constant pressure technique. The transition from the zinc-blende structure to a rocksalt structure is successfully reproduced through the simulation. The transformation mechanism is characterized and found that the transformation is due to the monoclinic modification of the simulation cell, similar to that found in SiC. [1, 2]. Furthermore, our finding supports the universal transition state of high-pressure zinc-blende to rocksalt transitions [3]. \newline \newline References: \newline [1] F. Shimojo, I. Ebbsj\"{o}, R. K. Kalia, A. Nakano, J. P. Rino, and P. Vashishta, Molecular Dynamics Simulation of Structural Transformation in Silicon Carbide under Pressure, Phys. Rev. Lett. 84, 3339 (2002). \newline [2] M. Durandurdu, Pressure-induce phase transition of SiC, J. Phys. Con. Mater 16 4411 (2004). \newline [3] M.S. Miao and W. R.L. Lambrecht, Universal Transition State for High-Pressure Zinc Blende to Rocksalt Phase Transitions, Phys. Rev. Lett., 94, 225501 (2005). [Preview Abstract] |
Friday, October 21, 2005 2:24PM - 2:36PM |
B5.00003: Internal dielectric interface: SiO$_{2}$/HfO$_{2}$. Onise Sharia, Alex Demkov, Genadi Bersuker, Byoung Hun Lee We investigate theoretically the atomic structure of the SiO$_{2}$-HfO$_{2}$ interface, its energretics, and thermodynamic stability with respect to oxygen exchange across the interface. We have examined the electronic properties of the interface including the band discontinuity. All calculations are performed using density functional theory. We employ ultra-soft pseudopotentials, and a plane wave basis set. To model the interface we build a supercell structure by connecting $\beta $-crystobalite (crystalline silica polymorph) and cubic hafnia. This model, while being obviously rather simplistic allows for systematic study of the dielectric thickness effects, and consistent placement of defects with respect to the interface. We use the idealized C9 structure of crystobalite (silica is assumed to be relaxed). The hafnia cell is matched to crystobalite \textit{via} a 45\r{ } rotation and is assumed to be under the 4{\%} tensile strain. Wee allow for the elongation of the c axis in response to strain. The striking atomic feature of the calculated interface structure is three-fold coordinated interfacial oxygen atoms connected to one Si and two Hf neighbors. The Si-O and Hf-O bond lengths are 1.62 and 2.1 {\AA}, respectively. The energy of the interface is estimated to be in the range of 900-4000 erg/cm$^{2}$ depending on the oxygen chemical potential. The structure has no states in the gap. We then consider the relative energies of oxygen vacancies on both sides of the interface. We investigate different positions and different charge states of the vacancy. [Preview Abstract] |
Friday, October 21, 2005 2:36PM - 2:48PM |
B5.00004: Surface States and Annihilation Characteristics of Positrons Trapped at Reconstructed Surfaces of Silicon Nail G. Fazleev Slow positron beam spectroscopies are currently being developed into sensitive tools for the characterization of surface and near surface phenomena in semiconductors and nanomaterials. Theoretical studies of positrons at surfaces are of intrinsic interest as they represent a system consisting of distinguishable quantum particles in a quasi 2-dimensional potential. Such studies are also necessary to derive the full power of the new surface positron spectroscopies. In this talk, I will report on recent developments in the theory of positron surface interactions and their application to positron surface states and annihilation characteristics of surface trapped positrons at the semiconductor surfaces. Calculations of positron states and annihilation characteristics are performed for the non-reconstructed and reconstructed Si(100)-(2x1), Si(100)-p(2x2), and Si(111)-(7x7) surfaces. The orientation-dependent variations of the atomic density and electron density are found to affect the localization of the positron surface state wave function at reconstructed surfaces. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of semiconductors. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700