纳米固体尺寸效应机理：键序-键长-键能相关理论及应用

da350d52ad02de80d4d84087 Size dependency of nanosolid materials (Digest)

Chang Q. Sun?

School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 Institute of Advanced Materials Physics and Faculty of Science, Tianjin University, 300072,

P. R. China

E-mail: ecqsun@da350d52ad02de80d4d84087.sg; URL: da350d52ad02de80d4d84087.sg/home/ecqsun/

(69.8 k words inclusive; 50 figs, 16 tab, 650 refs, Updated: 06/25/2005)

Full article is available:

da350d52ad02de80d4d84087/abs/cond-mat/0506113

Abstract

A review is presented on the recent progress in understanding the mechanism behind the tunability of nanosoild materials with emphasis on its practical applications in nanosolid materials design. Attempt has been made to reconcile all detectable and tunable properties and all available models by incorporating an intensively verified bond order-length-strength (BOLS) correlation mechanism as origin to all possible mechanisms and the huge database of experimental observations. The BOLS correlation indicates that bond order loss, or atomic coordination (CN) imperfection, causes the remaining bonds of the lower-coordinated atoms to contract spontaneously associated with bond strength gain. Consequently, densification and localization of charge, energy, and mass in surface skin and modification of cohesive energy of the discreted atoms take place, which dictate the performance of a nanosoild of which the portion of the lower-coordinated surface atoms increases with inverse of size. Consistency between BOLS predictions and experimental observations confirms the tremendous impact of bond order loss at grain boundaries on the performance of a nanosolid in mechanical strength, thermal stability, acoustic vibration, photoemission and photoabsorption, electronic configuration, magnetism and dielectrics, and on the activation energies for atomic diffusion, atomic dislocation, and chemical reactivity as well as self-assembly growth. Extension of the BOLS correlation to the understanding of liquid surfaces, structural defects, substitution impurities, junction interfaces, and amorphous state, as well as transport dynamics is also discussed, which might open up new directions of research.

Keywords: Nanostructures; low dimensional system; surface and interface; mesoscopic; chemical bond; coordination number; bond contraction; mechanical strength; compressibility; acoustics; thermal stability; optics; dielectrics; magnetism; phase transition; diffusivity; reactivity; crystal growth.

?E-mail: ecqsun@da350d52ad02de80d4d84087.sg; URL: da350d52ad02de80d4d84087.sg/home/ecqsun/

1

da350d52ad02de80d4d84087

?Motivation

Properties of solids determined by their shape and size are indeed fascinating and form the basis of the emerging field of nanoscience and nanotechnology that has been recognized as the key significance in science, technology, and economics in the 21st century. Overwhelming contributions have been made to atomic imaging and manipulating, nanosolid synthesizing, functioning, and characterizing as well as structuring patterning and lithographing. However, mechanism behind the nanosolid tunability remains yet infancy and predictive design of nanomaterials is a high challenge. For a single phenomenon, there are often numerous theories discussing from various perspectives. Origin behind all observations is yet poorly known. Furthermore, structural miniaturization provides us with an additional freedom that not only allows us to tune the properties by changing the shape and size, but also challenges us to gain information that is beyond traditional approaches. The BOLS correlation mechanism is initiated and intensively verified for this purpose.

?BOLS correlation theory

The BOLS correlation theory1,2 indicates that the CN imperfection of atoms at sites surrounding defects or near the surface edge dictates the tunability of a nanosolid of which the portion of such

lower-coordinated atoms increases inversely with solid size. Atomic CN imperfection causes the remaining bonds of the lower-coordinated atom to contract spontaneously associated with magnitude rise in bond energy, or intraatomic potential well deepening. Bond contraction and potential-well deepening causes densification of charge, mass, and energy in the relaxed region, which contribute to the work function and the magnetization in the relaxed region. Bond strengthening enhances the energy density per unit volume in the relaxed continuum region, which perturbs the Hamiltonian of an extended solid and the associated properties such as the band and band-gap widths, core-level shift, Stokes shift (electron-phonon interaction), and dielectric suppression. On the other hand, the

CN-imperfection lowers the cohesive energy per discrete atom of the lower-coordinated system, which dictates the thermodynamic process of the solid such as self-assembly growth, atomic vibration, phase transition, diffusitivity, sinterbility, chemical reactivity, and thermal stability. The joint effect of atomic cohesive energy depression and energy density enhancement dictates the mechanical strength (surface stress, surface energy, and Young’s modulus), and compressibility (extensibility, or ductility) of a nanosolid below the melting point that drops with the solid dimension.

?Achievement

The BOLS correlation has enabled the following major progress:

(i)The unusual behavior of a nanosolid in mean lattice contraction,3,4 mechanical strength,,5,6 phase

transition,7,8,9 thermal stability,10 atomic vibration (acoustic and optical phonons),11,12,13

optoelectronics (photoemission and absorption),14,15,16,17 core level energy,18,19 magnetism,20,21 dielectrics,22,23,24,25,26 and chemical reactivity27 has been predicted and experimentally verified, which are generalized as functions of atomic CN imperfection and its derivatives on crystal binding intensity, electron-phonon interaction or atomic cohesion. This enables nanosolid to form with desired functions in a predictable way.

(ii)The bonding identities such as the length, strength, extensibility, and thermal and chemical stability,28 in metallic monatomic chains29,30 and in the carbon nanotubes31 have been determined.

Understanding has been extended to the mechanical strength and ductility of metallic nanowires, and the inverse Hall-Petch relationship that shows the puzzling transition from hardening to

softening in nanometer regime.32

2

3(iii) Most strikingly, a novel yet simple way has been developed to elucidating quantitative information

of single energy levels of an isolated (Si, Pd, Au, Ag and Cu) atom and its shift upon bulk and nanosolid formation by matching predictions, with no freely adjustable parameters, to the observed size and shape dependence of the XPS and Auger photoelectron coincidence spectroscopy

(APECS)33 data. This in turn enhances the capability of the existing XPS and APECS techniques.34 35,36

(iv) Quantitative information about dimer vibration 11 and electron-phonon interaction 37 has been

obtained by matching predictions to the measured shape and size dependence of the Raman and photoemission/absorption spectra of Si and other III-V and II-VI compounds. The phase stability of ferromagnetic, ferroelectric and superconductive nanosoilds has also been unified to the CN imperfection of different orders.38 The approach allows us to discriminate the extent of

oxidation 39and contribution of surface passivation 40 in the dielectrics of porous silicon, as well as superconductivity phase transition.41

1 Sun CQ, Tay BK, Zeng XT, et al., Bond-order-length-strength (BOLS) correlation mechanism for the shape and size dependency of a nanosolid. J. PHYS. CONDENS MATT. 2002;14:7781-95.

2 Sun CQ, Gong HQ, Hing P, et al. Behind the quantum confinement and surface passivation of nanoclusters. SURF REV LETT 1999;6:L171-6.

3 Sun CQ, Li S, and Tay BK, Laser-like mechanoluminescence in ZnMnTe-diluted magnetic semiconductor. APPL PHYS LETT 2003;82:3568-9.

4 Sun CQ. The lattice contraction of nanometer-sized Sn and Bi particles produced by an electrohydrodynamic technique. J PHYS-CONDENS MAT 1999;11:4801-3.

5 Zeng XT, Zhang S, Sun CQ, Liu YC. Nan metric-layered CrN/TiN thin films: mechanical strength and thermal stability. THIN SOLID FILMS 2003;424:99-102.

6 Sun CQ, Li S, Li CM, Impact of bond-order loss on surface and nanosolid mechanics, J PHYS CHEM

2005;B109:415-23. 7 Zhong WH, Sun CQ, et al. Curie temperature suppression of ferromagnetic nanosolids. J PHYS-CONDENS MAT 2002;14:L399-405. 8 Pan LK, Huang HT, Sun CQ. Dielectric transition and relaxation of nanosolid silicon. J APPL PHYS 2003;94:2695-700. 9 Ye HT, Sun CQ, Huang HT, et al. Dielectric transition of nanostructured diamond films. APPL PHYS LETT 2001;78:1826-8. 10 Sun CQ, Wang Y, Tay BK, et al. Correlation between the melting point of a nanosolid and the cohesive energy of a surface atom. J PHYS CHEM 2002;B106:10701-5. 11 Sun CQ, Pan LK, Li CM. Elucidating Si-Si dimer vibration from the size-dependent Raman shift of nanosolid Si. J PHYS CHEM 2004;B108(11): L3404-6. 12 Sun CQ, Pan LK, Fu YQ, et al. Size dependent 2p-level shift of nanosolid silicon. J PHYS CHEM 2003;B107:L5113-5. 13 Sun CQ, Sun XW, Gong HQ, et al. Frequency shift in the photoluminescence of nanometric SiOx: surface bond contraction and oxidation. J PHYS-CONDENS MAT 1999;11:L547-50. 14 Sun CQ, Li S, Tay BK, Chen TP, Upper limit of blue shift in the photoluminescence of CdSe and CdS nanosolids, ACTA MATERIALIA 2002;50:4687-93. 15 Pan LK, Sun CQ, Tay BK, et al. Photoluminescence of Si nanosolid near the lower end of the size limit. J PHYS CHEM 2002;B106:11725-7. 16 Sun CQ, et al. Effects of surface passivation and interfacial reaction on the size-dependent 2p-level shift of supported copper nanosolids. ACTA MATERIALIA 2003;51:4631-6. 17 Sun CQ, Chen TP, Tay BK, et al. An extended 'quantum confinement' theory: surface-coordination imperfection modifies the entire band structure of a nanosolid. J PHYS D 2001;34:3470-9. 18 Chen TP, Liu Y, Sun CQ, et al, Core-Level Shift of Si Nanocrystals Embedded in SiO 2 Matrix, J PHYS CHEM 2004: B 108;16609-12. 19 Sun CQ, Pan LK, Chen TP, Sun XW, Li S, and Li CM, Distinguishing the effect of crystal-field screening from the effect of valence recharging on the 2p 3/2 and 3d 5/2 level energies of nanostructured copper, APPL SURF SCI, in press da350d52ad02de80d4d84087

da350d52ad02de80d4d84087

20 Zhong WH, Sun CQ, Li S, Bai HL, Jiang EY. Impact of bond order loss on surface and nanosolid magnetism,

ACTA MATERIALIA, IN PRESS.

21 Zhong WH, Sun CQ, Li S, Size effect on the magnetism of nanocrystalline Ni films at ambient temperature.

SOLID STATE COMMUN. 2004;13:603-6.

22 Huang HT, Sun CQ, Zhang TS. Grain-size effect on ferroelectric Pb(Zr1-xTix)O-3 solid solutions induced by

surface bond contraction. PHYS REV 2001;B63:184112( 9 pages).

23 Huang HT, Sun CQ, Hing P. Surface bond contraction and its effect on the nanometric sized lead zirconate

titanate. J PHYS-CONDENS MAT 2000;12:L127-32.

24 Sun CQ, Sun XW, Tay BK, et al. Dielectric suppression and its effect on photoabsorption of nanometric

semiconductors. J PHYS D 2001;34:2359-62.

25 Ye HT, Sun CQ, Hing P. Control of grain size and size effect on the dielectric constant of diamond films. J

PHYS D 2000;33:L148-52.

26 Pan LK, Sun CQ, Dielectric suppression of nanosolid Si, NANOTECHNOLOGY 2004;15:1802-6.

27 Pan LK, Ee YK, Sun CQ, Yu GQ, Band gap expansion, core level shift and dielectric suppression of nanosolid

Si passivated by plasma fluorination. J VAC SCI TECHNOL 2004;B22:583-7

28 Sun CQ, Bai HL, Li S, et al. Size effect on the electronic structure and the thermal stability of a gold nanosolid.

ACTA MATERIALIA 2004;52:501-5.

29 Sun CQ, Bai HL, Li S, et al. Length, strength, extensibility and thermal stability of an Au-Au bond in the gold

monatomic chain. J PHYS CHEM 2004;B108:2162-7.

30 Sun CQ, Li C, and Li S. Breaking limit of atomic distance in an impurity-free monatomic. PHYS REV

2004;B69:245402 (6 pages).

31 Sun CQ, Bai HL, Tay BK, et al. Dimension, strength, and chemical and thermal stability of a single C-C bond in

carbon nanotubes. J PHYS CHEM 2003;B107:7544-6.

32 Sun CQ, Thermo-mechanics of low dimensional systems: strain, strength, extensibility, and stability (15 k

words; 180 refs, 12 figures; 5 tables) under review

33 Sun CQ, et al. Effects of screen shielding and catalytic recharging on the simultaneous shift of 3d

and 2p3/2

5/2 levels of Cu. COMMUNICATED

34 Sun CQ, Tay BK, Fu YQ, Discriminating crystal bonding from the atomic trapping of a core electron at energy

levels shifted by surface relaxation or nanosolid formation. J PHYS CHEM 2003;B107:L411-4.

35 Sun CQ. Atomic-coordination-imperfection-enhanced Pd-3d

crystal binding energy. SURF REV LETT

5/2

2003;10:1009-13.

36 Sun CQ. Surface and nanosolid core-level shift: impact of atomic coordination number imperfection. PHYS

REV 2004;B69:045105 (8 pages).

37 Pan LK, Sun CQ. Coordination imperfection enhanced electron-phonon interaction in nanosolid silicon. J

APPL PHYS 2004; 95:3819-21.

38 Sun CQ, Zhong WH, Li S, et al. Coordination imperfection suppressed phase stability of ferromagnetic,

ferroelectric, and superconductive nanosolids. J PHYS CHEM 2004;B108(3):1080-4.

39 Pan LK, Sun CQ, Li CM, Estimating the extent of surface oxidation by measuring the porosity dependent

dielectrics of oxygenated porous silicon, APPL SURF SCI. 2005;240:19-23.

40 Pan LK, Sun CQ, et al., Distinguishing the effect of surface passivation from the effect of size on the photonic

and electronic behavior of porous silicon, J APPL PHYS 2004; 96:1704-8.

41 Li S, White T, Sun CQ, et al., Discriminating Lattice Structural Effects from Electronic Contributions to the

Superconductivity of Doped MgB2 with Nanotechnology, J PHYS CHEM 2004;B 108:16415-9.

4

本文来源：https://www.bwwdw.com/article/b4fl.html