Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session H25: Focus Session: Dopants and Defects in Semiconductors - Si |
Hide Abstracts |
Sponsoring Units: DMP Chair: Pat Mooney, Simon Fraser University Room: D135 |
Tuesday, March 16, 2010 8:00AM - 8:12AM |
H25.00001: Isotopic Fingerprints of four and five-atom Pt luminescence centers in $^{28}$Si Michael Steger, Albion Yang, Takeharu Sekiguchi, Kamyar Saeedi, M.L.W. Thewalt, M.O. Henry, K. Johnston, H. Riemann, N.V. Abrosimov, P. Becker, H.-J. Pohl We have recently demonstrated that observing `isotopic fingerprints' in $^{28}$Si leads to many surprises regarding the actual constituents of supposedly well known deep luminescence centers. A series of four and five-atom complexes containing Cu, Ag, Au and Li were found. We now extend this by observing Pt containing centers in $^{28}$Si. The two previously observed Pt-related centers, with luminescence at 884 and 777 meV, are found to contain three and four Cu atoms, respectively, in addition to a single Pt atom. With the addition of Li to these Pt implanted samples we report on a series of four and five-atom complexes containing Cu, Pt and Li, similar to those found for Cu, Au and Li before. This further demonstrates the ubiquity of four- and five-atom luminescence centers in Si. [Preview Abstract] |
Tuesday, March 16, 2010 8:12AM - 8:24AM |
H25.00002: Modelling the Si(110) surface Veronika Brazdova, Martin Setvin, Kazushi Miki, Cyrus F. Hirjibehedin, David R. Bowler The Si(110) surface has been less intensively studied than Si(001) and Si(111). However, it also shows interesting scientific and technological properties, including a complex stepped (16x2) surface reconstruction. We will present results of comprehensive density functional theory studies on the diffusion of Si and H adatoms on Si(110)-(1x1), as well as of the driving mechanisms behind the surface reconstruction. The diffusion studies are a necessary starting point for understanding the growth of features with (110) sidewalls; the Si adatom diffusion will also feed into the studies of Si(110)-(16x2), as the formation of this reconstruction seems to involve significant amounts of mass transport. Barriers and structures resulting from diffusion will be presented, and their implications for growth and reconstruction will be discussed. We will discuss the implication of Si atom adsorption and surface defect formation on the reconstruction of the surface. [1] T Mizuno et al, IEEE Trans Electron Devices 2005, 52, 367. [2] Y Suda et al, Appl Surf Sci 2003, 216, 424. [Preview Abstract] |
Tuesday, March 16, 2010 8:24AM - 8:36AM |
H25.00003: Quantum confinement in P doped Si nanowires and nanofilms Jiaxin Han, Tzu-Liang Chan, James Chelikowsky Functionalized Si nanowires have been synthesized and used as interconnects in electronic circuits or building blocks for semiconductor nanodevices. Likewise, thin films of silicon have been incorporated in transistor applications. In order to understand how doping operates in these nanostructures, we employed a real-space pseudopotential method to study P-doped Si nanostructures. We will examine the size dependence of the electronic binding energy for the P donor level in nanowires and nanofilms as function of size and dimensionality. In particular, we will present results for P doped Si [110] nanowires as function of the wire diameter and P doped Si [111] nanofilms as a function of the film thickness. [Preview Abstract] |
Tuesday, March 16, 2010 8:36AM - 9:12AM |
H25.00004: Defects at the Nanoscale: The Role of Quantum Confinement and Dimensionality Invited Speaker: One of the most challenging issues in materials physics is to predict the properties of defects in matter. Such defects play an important role in functionalizing materials for use in electronic devices. As the length scale for such devices approaches the nano-regime, the interplay of dimensionality, quantum confinement and defects can be complex. In particular, the usual rules for describing defects in bulk may be inoperative, {\it i.e.}, a shallow defect level in bulk may become a deep level at the nanoscale. The development of theoretical methods to describe the properties of nanoscale defects is a formidable challenge. Nanoscale systems may contain numerous electronic and nuclear degrees of freedom, and often possess little symmetry. My presentation will center on recent advances in this area based on new algorithms, which allow a solution of the Kohn-Sham eigenvalue problem without any explicit diagonalization. I will apply these algorithms to nanoscale systems, and present calculations for the structural and electronic properties of dopants (Li, Zn, B, P, Mn..) in semiconductor (Si, InP, ZnO, CdSe, ...) nanostructures. We will vary the size and dimensionality of these nanostructures, by considering nanocrystals, nanowires and nanofilms. [Preview Abstract] |
Tuesday, March 16, 2010 9:12AM - 9:24AM |
H25.00005: Low temperature AFM/STM for characterization of Si:H(111) surfaces and measurement of subsurface donors Pavel Nagornykh, Michael Dreyer, Bruce E. Kane Hydrogen terminated Si(111) surfaces can be prepared to have a very low density of defects, manifested in mobility values for surface electrons as high as 100,000 cm2/Vs in gated FETs [1]. Using such surfaces, it may be possible to detect and manipulate single subsurface donors and their states. Achievement of such control could serve as a step in development of silicon-based quantum computing, and low temperature AFM is considered a candidate for such measurements. In order to do this type of experiment, we have converted a low temperature UHV STM into AFM/STM by using a tuning fork as the AFM sensor. Signal from the fork is amplified by a low temperature home-made preamplifier, which was used to decrease capacitive noise coupling. The shift in resonance frequency of the fork's signal serves as a control signal for AFM scanning. In case of STM mode, current through a tungsten tip attached to one of the prongs of tuning fork is used as a feedback control. Current progress in imaging of Si:H(111) by using our system at low temperatures($\sim$ 4K) will be discussed in detail. \\[4pt] [1] Robert N. McFarland et al., Phys. Rev. B 80, 161310(R) (2009) [Preview Abstract] |
Tuesday, March 16, 2010 9:24AM - 9:36AM |
H25.00006: The influence of a Pb surfactant on Mn delta-doped layers on Si(001) S. Kahwaji, S. Roorda, S. Q. F. Xiao, R. A. Gordon, E. D. Crozier, M. D. Robertson, T. L. Monchesky The high growth temperatures normally required for MBE growth of Si pose a challenge for the growth of dilute magnetic semiconductors based on Si. With the use of a Pb surfactant, we can drop the growth temperature of Si(001) below 200$^{o}$C, while preserving epitaxial growth, as shown by RHEED and TEM. The Pb surfactant also influences how a single Mn delta-doped layer grows on Si(001). ~For 0.7 monolayer Mn deposition onto Pb/Si(001), RBS/channeling measurements show that 25{\%} of the Mn occupies a substitutional-like site. This fraction increases with decreasing Mn concentration. Polarization-dependent XAFS measurements suggest that the samples grown without Pb exhibit a CsCl-like structure. XAFS results for 0.7 ML Mn on Pb/Si(001) differ from growth without Pb, with 2 types of Si neighbors at short (in-plane) and long Mn-Si distances and a ratio of coordination numbers comparable to the RBS results. [Preview Abstract] |
Tuesday, March 16, 2010 9:36AM - 9:48AM |
H25.00007: Determination of the energy level of boron induced charge traps in Si/SiO$_{2}$ systems by second harmonic generation Heungman Park, Jingbo Qi, Ying Xu, Kalman Varga, Gunter L\"upke, Norman Tolk Interfacial charge traps were characterized using second harmonic generation (SHG) in highly boron-doped Si/SiO$_{2}$ systems. We propose the presence of B$^{-}$ and B$^{+}$ ions in Si substrate and SiO$_{2}$ respectively across the interface [1]. A two color pump-probe SHG experiment was performed to determine the energy level of the B$^{+}$ ion in the oxide. A threshold wavelength of 475 nm (2.61 eV) was found for single photon excitation of electrons from the Si valence band to fill B$^{+}$ charge traps in SiO$_{2}$ [2]. This work was supported in part by DOE. \\[4pt] [1] H. Park and Y. Xu J. Qi, K. Varga, S. M. Weiss, B. R. Rogers, G. L\"upke, N. Tolk, Appl. Phys. Lett. 95, 062102 (2009). \\[0pt] [2] To be published. [Preview Abstract] |
Tuesday, March 16, 2010 9:48AM - 10:00AM |
H25.00008: Altering the Charge State of Surface Silicon Dangling Bonds using Nanoscale Schottky Contacts Jason Pitters, Iana Dogel, Robert Wolkow The study of surface defects, and in particular, dangling bonds (DBs) on semiconductor surfaces and at interfaces has been an area of interest for years. Interest has been driven from the unique characteristics of the DB, due to fact that the DB state lies within the bandbap of the semiconductor and can assume various charged states. Recently, we have demonstrated that negatively charged dangling bonds can act as a gate electrode to control the flow of current through single molecules. We have also shown that DB clusters enter into a tunnel coupled relationship at close distances providing a means to implement room temperature QCA schemes. In order advance these experiments, it is important to develop strategies that can control the charge state of DBs. This presentation will show that nanoscale Schottky contacts of Titanium disilicide on hydrogen terminated silicon surfaces can change the charge state of DBs. DBs created within the depletion region have a reduced charge compared to those created at a distance from the contact. We also directly observe the band bending at the nanoscale Schottky interface using scanning tunneling microscopy and spectroscopy. [Preview Abstract] |
Tuesday, March 16, 2010 10:00AM - 10:12AM |
H25.00009: Diffusion Monte Carlo Calculations of Formation Energies of Charged Self Interstitial Defects in Silicon Jonathan L. DuBois, Daniel Aberg, Vincenzo Lordi Scattering and trapping of carriers by charged point defects represent a significant limiting factor on carrier lifetimes in semiconductors. Given that long carrier lifetimes are essential for a wide range of semiconductor applications, accurate methods for predicting defect concentrations and defect-induced intragap energy levels are needed. Previous studies of neutral defects in silicon show significant deviations between DFT and Diffusion Monte Carlo (DMC) benchmark calculations of formation energies. Here we present DMC results for the formation energies of charged self interstitial defects in bulk silicon and extract charge state transition energy levels, which we compare to DFT LDA and hybrid functional results. [Preview Abstract] |
Tuesday, March 16, 2010 10:12AM - 10:24AM |
H25.00010: Investigation of charge trapping at grain boundaries in polycrystalline and multi-crystalline silicon solar cells Jennifer Heath, Chun-Sheng Jiang, Helio Moutinho, Mowafak Al-Jassim The electronic properties of grain boundaries in polycrystalline and multicrystalline silicon are known to vary significantly depending on the individual grain misorientations, due to differences in dangling bonds, strain, and impurity gettering.~ By correlating Electron Backscattering Diffraction maps with the Light Beam Induced Current data, we can see, as expected, that the minority carrier diffusion length is significantly reduced near certain grain boundaries (GB) while others are relatively benign.~ We have found that GBs with poor diffusion length also tend to have trapped charge, resulting in depletion regions along the GB visible in Scanning Capacitance Microscopy (SCM) data.~ Scans of SCM signal as a function of dc probe voltage and temperature allow these regions to be more quantitatively investigated. [Preview Abstract] |
Tuesday, March 16, 2010 10:24AM - 10:36AM |
H25.00011: Size Fractionation of Mechanochemical Synthesized Alkyl-Passivated Silicon Nanoparticles Luigi Verdoni, Brian Mitchell A novel top-down procedure was employed for the synthesis of stable alkyl-passivated silicon nanoparticles using reactive high energy ball milling (HEBM) as described in Heintz et al., (Adv. Mater. 2007, 19). The method provides for the simultaneous production of photo luminescent silicon nanoparticles and the passivation of the particle surface with alkyl groups covalently linked through Si-C bonds. As fresh silicon surface is formed during HEBM by particle fracture, the surface Si atoms react in-situ with liquid alkyls, such as 1-octyne and 1-hexyne. We present a multistage size selective fractionation process to isolate and purify initial sample polydispersities ranging from microns down to single nanometers (1 um - 1 nm). This process employs centrifugation, inline nano-filtration, both normal phase gel permission (GPC) and size exclusion chromatography (SEC), followed by recursive size selective precipitation (SSP). Size evolutions of fractions are monitored via UV/VIS absorbance, photoluminescence (PL), and electron microscopy (SEM/TEM). Elemental impurities are quantified through atomic absorption (AAS) and energy dispersive spectroscopy (EDS). Stages are performed in series to isolate and investigate the influence of initial alkyl and silicon reactants on product yields, size dispersity, and optical behavior. [Preview Abstract] |
Tuesday, March 16, 2010 10:36AM - 10:48AM |
H25.00012: ABSTRACT WITHDRAWN |
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