1
|
Tanaka H, Ohno S, Miki K, Tanaka M. Thermal oxidation process on Si(113)-(3 × 2) investigated using high-temperature scanning tunneling microscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:172-181. [PMID: 35186651 PMCID: PMC8822459 DOI: 10.3762/bjnano.13.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 01/17/2022] [Indexed: 06/14/2023]
Abstract
Thermal oxidation of Si(113) in a monolayer regime was investigated using high-temperature scanning tunneling microscopy (STM). Dynamic processes during thermal oxidation were examined in three oxidation modes - oxidation, etching, and transition modes - in the third of which both oxidation and etching occur. A precise temperature-pressure growth mode diagram was obtained via careful measurements for Si(113), and the results were compared with those for Si(111) in the present work and Si(001) in the literature. Initial oxidation processes were identified based on high-resolution STM images.
Collapse
Affiliation(s)
- Hiroya Tanaka
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Shinya Ohno
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Kazushi Miki
- Department of Electrical Materials and Engineering, University of Hyogo, Shoya 2167, Himeji, Hyogo 671-2280, Japan
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Masatoshi Tanaka
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| |
Collapse
|
2
|
Owen JHG, Campbell Q, Santini R, Ivie JA, Baczewski AD, Schmucker SW, Bussmann E, Misra S, Randall JN. Al-alkyls as acceptor dopant precursors for atomic-scale devices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:464001. [PMID: 34399418 DOI: 10.1088/1361-648x/ac1ddf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 08/16/2021] [Indexed: 06/13/2023]
Abstract
Atomically precise ultradoping of silicon is possible with atomic resists, area-selective surface chemistry, and a limited set of hydride and halide precursor molecules, in a process known as atomic precision advanced manufacturing (APAM). It is desirable to expand this set of precursors to include dopants with organic functional groups and here we consider aluminium alkyls, to expand the applicability of APAM. We explore the impurity content and selectivity that results from using trimethyl aluminium and triethyl aluminium precursors on Si(001) to ultradope with aluminium through a hydrogen mask. Comparison of the methylated and ethylated precursors helps us understand the impact of hydrocarbon ligand selection on incorporation surface chemistry. Combining scanning tunneling microscopy and density functional theory calculations, we assess the limitations of both classes of precursor and extract general principles relevant to each.
Collapse
Affiliation(s)
- J H G Owen
- Zyvex Labs, Richardson, TX, United States of America
| | - Q Campbell
- Sandia National Labs, Albuquerque, NM, United States of America
| | - R Santini
- Zyvex Labs, Richardson, TX, United States of America
| | - J A Ivie
- Sandia National Labs, Albuquerque, NM, United States of America
| | - A D Baczewski
- Sandia National Labs, Albuquerque, NM, United States of America
| | - S W Schmucker
- Sandia National Labs, Albuquerque, NM, United States of America
| | - E Bussmann
- Sandia National Labs, Albuquerque, NM, United States of America
| | - S Misra
- Sandia National Labs, Albuquerque, NM, United States of America
| | - J N Randall
- Zyvex Labs, Richardson, TX, United States of America
| |
Collapse
|
3
|
Chang CY, Lin CY, Lin DS. How dissociated fragments of multiatomic molecules saturate all active surface sites-H 2O adsorption on the Si(100) surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:404004. [PMID: 34265758 DOI: 10.1088/1361-648x/ac14f7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 07/15/2021] [Indexed: 06/13/2023]
Abstract
A fundamental question for the adsorption of any gas molecule on surfaces is its saturation coverage, whose value can provide a comprehensive examination for the adsorption mechanisms, dynamic and kinetic processes involved in the adsorption processes. This investigation utilizes scanning tunneling microscopy to visualize the H2O adsorption processes on the Si(100) surface with a sub-monolayers (<0.05 ML) of chemically-reactive dangling bonds remaining after exposure to (1) a hydrogen atomic beam, (2) H2O, and (3) Cl2gases at room temperature. In all three cases, each of the remaining isolated single dangling bonds (sDB) adsorb and is passivated by either of the two dissociation fragments, the H or OH radical, to form a surface Si-H and Si-OH species. A new adsorption mechanism, termed 'dissociative and asynchronous chemisorption', is proposed for the observation presented herein. Upon approaching a sDB site, the H2O molecule breaks apart into two fragments. One is chemisorbed to the sDB. The other attaches to the same or the neighboring passivated dimer to form a transition state of surface diffusion, which then diffuses on the mostly passivated surface and is eventually chemisorbed to another reactive site. In other words, the chemisorption reactions of the two fragments after dissociation occur at different and uncorrelated time and places. This adsorption mechanism suggests that a diffusion transition state can be an adsorption product in the first step of the dissociative adsorption processes.
Collapse
Affiliation(s)
- Chan-Yuen Chang
- Department of Physics, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan
| | - Cheng-Yu Lin
- Department of Physics, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan
| | - Deng-Sung Lin
- Department of Physics, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan
| |
Collapse
|
4
|
Stegmüller A, Werner K, Reutzel M, Beyer A, Rosenow P, Höfer U, Stolz W, Volz K, Dürr M, Tonner R. Surface Chemistry of tert-
Butylphosphine (TBP) on Si(001) in the Nucleation Phase of Thin-Film Growth. Chemistry 2016; 22:14920-14928. [DOI: 10.1002/chem.201602418] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Andreas Stegmüller
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 4 35032 Marburg Germany
| | - Katharina Werner
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Marcel Reutzel
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Andreas Beyer
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Phil Rosenow
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 4 35032 Marburg Germany
| | - Ulrich Höfer
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Wolfgang Stolz
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Kerstin Volz
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
| | - Michael Dürr
- Fachbereich Physik and Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 6 35032 Marburg Germany
- Institut für Angewandte Physik; Justus-Liebig-Universität Giessen; Heinrich-Buff-Ring 16 35392 Giessen Germany
| | - Ralf Tonner
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 4 35032 Marburg Germany
| |
Collapse
|
5
|
Smith R, Brázdová V, Bowler DR. Hydrogen adsorption and diffusion around Si(0 0 1)/Si(1 1 0) corners in nanostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:295301. [PMID: 24957137 DOI: 10.1088/0953-8984/26/29/295301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
While the diffusion of hydrogen on silicon surfaces has been relatively well characterized, both experimentally and theoretically, diffusion around corners between surfaces, as will be found on nanowires and nanostructures, has not been studied. Motivated by nanostructure fabrication by Patterned Atomic Layer Epitaxy, we present a density functional theory study of the diffusion of hydrogen around the edge formed by the orthogonal (0 0 1) and (1 1 0) surfaces in silicon. We find that the barrier from (0 0 1) to (1 1 0) is approximately 0.3 eV lower than from (1 1 0) to (0 0 1), and that it is comparable to diffusion between rows on a clean surface, with no significant effect on the hydrogen patterns at the growth temperatures used.
Collapse
Affiliation(s)
- Richard Smith
- London Centre for Nanotechnology, UCL, 17-19 Gordon St, London WC1H 0AH, UK. Department of Physics & Astronomy, UCL, Gower St, London WC1E 6BT, UK. Thomas Young Centre, UCL, Gower St, London WC1E 6BT, UK
| | | | | |
Collapse
|
6
|
Biswas S, Deshpande SV, Dunn DN, Narasimhan S. Tuning patterning conditions by co-adsorption of gases: Br2 and H2 on Si(001). J Chem Phys 2013; 139:184713. [PMID: 24320297 DOI: 10.1063/1.4828702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have studied the co-adsorption of Br2 and H2 on Si(001), and obtained co-adsorption energies and the surface phase diagram as a function of the chemical potential and pressure of the two gases. To do this, we have used density functional theory calculations in combination with ab initio atomistic thermodynamics. Over large ranges of bromine and hydrogen chemical potentials, the favored configuration is found to be either one with only Br atoms adsorbed on the surface, at full coverage, in a (3 × 2) pattern, or a fully H-covered surface in a (2 × 1) structure. However, we also find regions of the phase diagram where there are configurations with either only Br atoms, or Br and H atoms, arranged in a two-atom-wide checkerboard pattern with a (4 × 2) surface unit cell. Most interestingly, we find that by co-adsorbing with H2, we bring this pattern into a region of the phase diagram corresponding to pressures that are significantly higher than those where it is observed with Br2 alone. We also find small regions of the phase diagram with several other interesting patterns.
Collapse
Affiliation(s)
- Sananda Biswas
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore - 560064, India
| | | | | | | |
Collapse
|
7
|
Robles R, Kepenekian M, Monturet S, Joachim C, Lorente N. Energetics and stability of dangling-bond silicon wires on H passivated Si(100). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:445004. [PMID: 23018314 DOI: 10.1088/0953-8984/24/44/445004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We evaluate the electronic, geometric and energetic properties of quasi 1D wires formed by dangling-bonds on Si(100)-H(2 × 1). The calculations are performed with density functional theory (DFT). Infinite wires are found to be insulating and Peierls distorted, however finite wires develop localized electronic states that can be of great use for atomic scale devices. The ground state solution of finite wires does not correspond to a geometrical distortion but rather to an antiferromagnetic ordering. For the stability of wires, the presence of abundant H atoms in nearby Si atoms can be a problem. We have evaluated the energy barriers for intradimer and intrarow diffusion, finding all of them about 1 eV or larger, even in the case where a H impurity is already sitting on the wire. These results are encouraging for using dangling-bond wires in future devices.
Collapse
Affiliation(s)
- R Robles
- Centro de Investigación en Nanociencia y Nanotecnología, CIN2 (CSIC-ICN), Campus de la UAB, E-08193 Bellaterra, Spain.
| | | | | | | | | |
Collapse
|
8
|
Kottke M, Neuburger M, Fee D, Beyer J, Pullman D. Observation of an exceptionally high apparent kinetic order in the thermal desorption of D2from the Si(100) surface. Mol Phys 2012. [DOI: 10.1080/00268976.2012.695809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
9
|
Satta M, Flammini R, Goldoni A, Baraldi A, Lizzit S, Larciprete R. Fundamental role of the H-bond interaction in the dissociation of NH3 on Si(001)-(2×1). PHYSICAL REVIEW LETTERS 2012; 109:036102. [PMID: 22861874 DOI: 10.1103/physrevlett.109.036102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/12/2012] [Indexed: 06/01/2023]
Abstract
Further insight into the dissociative adsorption of NH3 on Si(001) has been obtained using a combined computational and experimental approach. A novel route leading to the dissociation of the chemisorbed NH3 is proposed, based on H-bonding interactions between the gas phase and the chemisorbed NH3 molecules. Our model, complemented by synchrotron radiation photoelectron spectroscopy measurements, demonstrates that the low temperature dissociation of molecular chemisorbed NH3 is driven by the continuous flux of ammonia molecules from the gas phase.
Collapse
Affiliation(s)
- Mauro Satta
- CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, Dipartimento di Chimica, Università di Roma La Sapienza I-00185, Roma, Italy
| | | | | | | | | | | |
Collapse
|
10
|
Brázdová V, Bowler DR. H atom adsorption and diffusion on Si(110)-(1×1) and (2×1) surfaces. Phys Chem Chem Phys 2011; 13:11367-72. [DOI: 10.1039/c1cp20108e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
11
|
Ning N, Vach H. Deposition Dynamics of Hydrogenated Silicon Clusters on a Crystalline Silicon Substrate under Typical Plasma Conditions. J Phys Chem A 2010; 114:3297-305. [DOI: 10.1021/jp909446c] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Ning Ning
- LPICM, Ecole Polytechnique, CNRS, 91128 Palaiseau, France
| | - Holger Vach
- LPICM, Ecole Polytechnique, CNRS, 91128 Palaiseau, France
| |
Collapse
|
12
|
Owen JHG. Competing interactions in molecular adsorption: NH(3) on Si(001). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:443001. [PMID: 21832459 DOI: 10.1088/0953-8984/21/44/443001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Ammonia is a good model system for the study of co-adsorption interactions, including indirect effects such as charge and strain-induced local effects on adsorption sites, and direct interactions such as hydrogen bonding. On the Si(001) surface, it adsorbs molecularly, via a dative bond from the N atom to the down atom of a buckled dimer, and is therefore very sensitive to the local charge conditions. It will then dissociate into -H and -NH(2) groups, adsorbed on the dangling bonds of the Si dimers. The NH(2) groups do not diffuse, so any correlations deriving from interactions during adsorption are preserved, and can be derived by analysis of the arrangements of the NH(2) groups. Hydrogen-bonding interactions are crucial in understanding the behaviour of this system, with significant co-adsorption interactions occurring both along and across rows, outweighing the electrostatic or buckling-related effects. In recent years, there have been several scanning tunnelling microscopy studies and extensive computational modelling of the NH(3) on Si(001) system, attempting to determine a dominant mechanism governing co-adsorption effects. In this review, I will discuss both experimental and theoretical results, make a comparison with similar molecules such as phosphine (PH(3)), and review the different ways in which experimentalists and modellers have approached this complex system.
Collapse
Affiliation(s)
- J H G Owen
- Department of Condensed Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| |
Collapse
|
13
|
Hsieh MF, Chung JY, Lin DS, Tsay SF. Correlation of reaction sites during the chlorine extraction by hydrogen atom from Cl∕Si(100)‐2×1. J Chem Phys 2007; 127:034708. [PMID: 17655456 DOI: 10.1063/1.2752502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Cl abstraction by gas-phase H atoms from a Cl-terminated Si(100) surface was investigated by scanning tunneling microscopy (STM), high-resolution core level photoemission spectroscopy, and computer simulation. The core level measurements indicate that some additional reactions occur besides the removal of Cl. The STM images show that the Cl-extracted sites disperse randomly in the initial phase of the reaction, but form small clusters as more Cl is removed, indicating a correlation between Cl-extracted sites. These results suggest that the hot-atom process may occur during the atom-adatom collision.
Collapse
Affiliation(s)
- Ming-Feng Hsieh
- Institute of Physics, National Chiao-Tung University, 1001 Ta-Hsueh Road, Hsinchu 300, Taiwan
| | | | | | | |
Collapse
|
14
|
Shi J, Chuan Kang H, Tok ES, Zhang J. Evidence for hydrogen desorption through both interdimer and intradimer paths from Si(100)-(2 x 1). J Chem Phys 2007; 123:34701. [PMID: 16080749 DOI: 10.1063/1.1937392] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Despite intensive work there are still controversial issues about desorption and adsorption of hydrogen on Si(100)-(2 x 1). In particular, the relative importance of the various interdimer- and intradimer-desorption paths is not clear. Nanosecond-pulse-laser desorption data have been used to argue that the 4H interdimer path is important, while data from thermal-desorption time-of-flight measurements suggest a large translationally hot contribution which cannot arise from the 4H interdimer path. The observation of a translationally hot desorption fraction at low to medium coverage can be accounted for by including the 2H interdimer path in quantum dynamical calculations. In this paper we investigate this issue further and present evidence that supports the inclusion of the intradimer path. Specifically, our results show that the intradimer and 3H interdimer paths provide the major contributions to the translationally hot fraction in the desorbate. Our conclusions are based on density-functional calculations of hydrogen translational excitation, mean-field analysis of thermal-desorption experiments over a range of ramp rate, and Monte Carlo simulations of nanosecond-pulse-laser experiments.
Collapse
Affiliation(s)
- J Shi
- Department of Chemistry, National University of Singapore
| | | | | | | |
Collapse
|
15
|
Dürr M, Höfer U. Comment on "Atomistic view of the recombinative desorption of H2 from H/Si(100)". PHYSICAL REVIEW LETTERS 2006; 96:209601; discussion 209602. [PMID: 16803216 DOI: 10.1103/physrevlett.96.209601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Indexed: 05/10/2023]
Affiliation(s)
- M Dürr
- Materials Science Laboratory Sony Deutschland GmbH Hedelfinger Strasse 61 D-70327 Stuttgart, Germany
| | | |
Collapse
|
16
|
Matsuno T, Niida T, Tsurumaki H, Namiki A. Coverage dependent desorption dynamics of deuterium on Si(100) surfaces: Interpretation with a diffusion-promoted desorption model. J Chem Phys 2005; 122:024702. [PMID: 15638609 DOI: 10.1063/1.1829994] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We studied coverage dependence of time-of-flight (TOF) spectra of D2 molecules thermally desorbed from the D/Si(100) surface. The mean translational energies Et of desorbed D2 molecules were found to increase from 0.20+/-0.05 eV to 0.40+/-0.04 eV as the desorption coverage window was decreased from 1.0 ML> or =thetaD> or =0.9 ML to 0.2 ML> or =thetaD> or =0 ML, being consistent with the kinetics switch predicted in the interdimer mechanism. The measured TOF spectra were deconvoluted into 2H, 3H, and 4H components by a curve fitting method along the principle of detailed balance. As a result, it turned out that the desorption kinetics changes from the 4H to the 3H situation at high coverage above thetaD=0.9 ML, while the 2H desorption is dominant for a quite wide coverage region up to thetaD=0.8 ML. A dynamic desorption mechanism by which the desorption is promoted by D-atom diffusion to dangling bonds was proposed.
Collapse
Affiliation(s)
- T Matsuno
- Department of Electrical Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
| | | | | | | |
Collapse
|
17
|
Hawa T, Zachariah MR. Internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles. J Chem Phys 2004; 121:9043-9. [PMID: 15527370 DOI: 10.1063/1.1797073] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We present a study of internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles of 2-10 nm diameter as a function of temperature, using molecular dynamics simulations employing a reparametrized Kohen-Tully-Stillinger interatomic potential. The internal pressure was found to increase with decreasing particle size but the density was found to be independent of the particle size. We showed that for covalent bond structures, changes in surface curvature and the associated surface forces were not sufficient to significantly change bond lengths and angles. Thus, the surface tension was also found to be independent of the particle size. Surface tension was found to decrease with increasing particle temperature while the internal pressure did not vary with temperature. The presence of hydrogen on the surface of a particle significantly reduces surface tension (e.g., drops from 0.83 J/m(2) to 0.42 J/m(2) at 1500 K). The computed pressure of bare and coated particles was found to follow the classical Laplace-Young equation.
Collapse
Affiliation(s)
- T Hawa
- Department of Mechanical Engineering and Department of Chemistry, University of Maryland, College Park, Maryland, USA
| | | |
Collapse
|
18
|
Tok ES, Ong SW, Kang HC. Hydrogen desorption kinetics from the Si(1−x)Gex(100)-(2×1) surface. J Chem Phys 2004; 120:5424-31. [PMID: 15267416 DOI: 10.1063/1.1645510] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the influence of germanium atoms upon molecular hydrogen desorption energetics using density functional cluster calculations. A three-dimer cluster is used to model the Si((1-x))Ge(x)(100)-(2x1) surface. The relative stabilities of the various monohydride and clean surface configurations are computed. We also compute the energy barriers for desorption from silicon, germanium, and mixed dimers with various neighboring configurations of silicon and germanium atoms. Our results indicate that there are two desorption channels from mixed dimers, one with an energy barrier close to that for desorption from germanium dimers and one with an energy barrier close to that for desorption from silicon dimers. Coupled with the preferential formation of mixed dimers over silicon or germanium dimers on the surface, our results suggest that the low barrier mixed dimer channel plays an important role in hydrogen desorption from silicon-germanium surfaces. A simple kinetics model is used to show that reasonable thermal desorption spectra result from incorporating this channel into the mechanism for hydrogen desorption. Our results help to resolve the discrepancy between the surface germanium coverage found from thermal desorption spectra analysis, and the results of composition measurements using photoemission experiments. We also find from our cluster calculations that germanium dimers exert little influence upon the hydrogen desorption barriers of neighboring silicon or germanium dimers. However, a relatively larger effect upon the desorption barrier is observed in our calculations when germanium atoms are present in the second layer.
Collapse
Affiliation(s)
- E S Tok
- Department of Materials Science, National University of Singapore, 10 Science Drive 4, Singapore 117543
| | | | | |
Collapse
|
19
|
Chen D, Boland JJ. Dimer-anticorrelation-induced stabilization of adsorbate clustering on the Si100-(2 x 1) surface. PHYSICAL REVIEW LETTERS 2004; 92:096103. [PMID: 15089492 DOI: 10.1103/physrevlett.92.096103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2003] [Indexed: 05/24/2023]
Abstract
It is well established that absorbate-absorbate interactions play a key role in determining the distribution of adsorbates on surfaces. In cases where these interactions are repulsive adsorbates frequently arrange so as to minimize these unfavorable interactions. This simple picture, however, neglects the influence of adsorption on the properties on the underlying substrate. Here, using STM, we show that on Si(100) many intrinsically repulsive adsorbates cluster to form surface patches even at low surface coverages. With the aid of density functional theory calculations and Monte Carlo simulations, we show that patch formation is an intrinsic property of the Si(100) surface that is driven by the energy lowering associated with the formation of extended regions of bare dimers. The enhanced attraction between anticorrelated tilted bare dimers is sufficient to offset the repulsions between adsorbates.
Collapse
Affiliation(s)
- Dongxue Chen
- Venable and Kenan Laboratories, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA
| | | |
Collapse
|
20
|
Dürr M, Höfer U. Molecular beam investigation of hydrogen dissociation on Si(001) and Si(111) surfaces. J Chem Phys 2004; 121:8058-67. [PMID: 15485270 DOI: 10.1063/1.1797052] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The influence of molecular vibrations on the reaction dynamics of H2 on Si(001) as well as isotopic effects have been investigated by means of optical second-harmonic generation and molecular beam techniques. Enhanced dissociation of vibrationally excited H2 on Si(001)2 x 1 has been found corresponding to a reduction of the mean adsorption barrier to 390 meV and 180 meV for nu=1 and nu=2, respectively. The adsorption dynamics of the isotopes H2 and D2 show only small differences in the accessible range of beam energies between 50 meV and 350 meV. They are traced back to different degrees of vibrational excitation and do not point to an important influence of quantum tunneling in crossing the adsorption barrier. The sticking probability of H2 on the 7 x 7-reconstructed Si(111) surface was found to be activated both by H2 kinetic energy and surface temperature in a qualitatively similar fashion as H2/Si(001)2 x 1. Quantitatively, the overall sticking probabilities of H2 on the Si(111) surface are about one order of magnitude lower than on Si(001), the influence of surface temperature is generally stronger.
Collapse
Affiliation(s)
- M Dürr
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg, Germany
| | | |
Collapse
|
21
|
Dürr M, Biedermann A, Hu Z, Höfer U, Heinz TF. Probing high-barrier pathways of surface reactions by scanning tunneling microscopy. Science 2002; 296:1838-41. [PMID: 12052951 DOI: 10.1126/science.1070859] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The ability of scanning tunneling microscopy to probe the pathways of thermally activated high-barrier surface processes is frequently limited by competing low-barrier processes that can confuse measurement of the true initial and final configuration. We introduce an approach to circumvent this difficulty by driving the surface process with nanosecond laser heating. The method is applied to determine the pathway of recombinative desorption in the H/Si(001) system. The observed configuration of dangling bonds after laser heating reveals that the desorbed hydrogen molecules are not formed on single dimers, but rather from neighboring silicon dimers via an interdimer reaction pathway.
Collapse
Affiliation(s)
- M Dürr
- Departments of Physics and Electrical Engineering, Columbia University, New York, NY 10027, USA.
| | | | | | | | | |
Collapse
|
22
|
Bulanin KM, Shah AG, Teplyakov AV. Infrared spectroscopy studies of iodoethane on Si(100)-2×1: Adsorption and thermal decomposition leading to adsorbate ordering. J Chem Phys 2001. [DOI: 10.1063/1.1405156] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|