Polaron absorption in tungsten oxide nanoparticle aggregates

被引：45

作者：

Niklasson, GA ^{[1
]}

Klasson, J ^{[1
]}

Olsson, E ^{[1
]}

机构：

[1] Uppsala Univ, Angstrom Lab, Dept Mat Sci, SE-75121 Uppsala, Sweden

来源：

ELECTROCHIMICA ACTA | 2001年 / 46卷 / 13-14期

关键词：

nanoparticles; optical absorption; polaron; bandgap; tungsten oxide;

D O I：

10.1016/S0013-4686(01)00388-7

中图分类号：

O646 [电化学、电解、磁化学];

学科分类号：

081704 ;

摘要：

Small tungsten oxide nanoparticles were prepared from a heated tungsten filament, by gas evaporation in air at pressures between 1 and 9 Torr. Transmission electron microscopy showed that the median particle diameter increased with pressure during evaporation from 7 nm at 1 Torr to 21 nm at 9 Torr. X-ray diffraction measurements were in agreement with data for the monoclinic and triclinic structures of tungsten trioxide. Composition analysis by Rutherford backscattering spectrometry gave evidence for a substoichiometric composition of WO2.7 to WO2.8. Optical reflectance and transmittance of samples deposited on sapphire substrates were measured in the wavelength range of 0.2-10 mum. From these data the absorption coefficient of the particulate samples was obtained. A strong absorption peak in the near infrared was ascribed to polaron absorption. The peak wavelength consistently shifted towards longer wavelengths with increasing evaporation pressure. This is probably a particle size effect and may be connected to an observed bandgap widening with decreasing particle size. (C) 2001 Elsevier Science Ltd. All rights reserved.

引用

页码：1967 / 1971

页数：5

共 11 条

[1] POLARONS IN CRYSTALLINE AND NON-CRYSTALLINE MATERIALS
AUSTIN, IG
MOTT, NF
[J]. ADVANCES IN PHYSICS, 1969, 18 (71) : 41 - +
[2] Bryksin V. V., 1982, Soviet Physics - Solid State, V24, P627
[3] Structure and electronic properties of amorphous WO3
de Wijs, GA
de Groot, RA
[J]. PHYSICAL REVIEW B, 1999, 60 (24) : 16463 - 16474
[4] OPTICAL-PROPERTIES OF LARGE AND SMALL POLARONS AND BIPOLARONS
EMIN, D
[J]. PHYSICAL REVIEW B, 1993, 48 (18) : 13691 - 13702
[5] Granqvist C. G., 1995, HDB INORGANIC ELECTR
[6] ULTRAFINE METAL PARTICLES
GRANQVIST, CG
BUHRMAN, RA
[J]. JOURNAL OF APPLIED PHYSICS, 1976, 47 (05) : 2200 - 2219
[7] OPTICAL-ABSORPTION OF FREE SMALL POLARONS AT HIGH-TEMPERATURES
HE, T
[J]. PHYSICAL REVIEW B, 1995, 51 (23) : 16689 - 16694
[8] *INT CTR DIFFR DAT, 1997, POWD DIFFR FIL 20 13
[9] Deposition temperature dependence of optical gap and coloration efficiency spectrum in electrochromic tungsten oxide films
Kubo, T
Nishikitani, Y
[J]. JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 1998, 145 (05) : 1729 - 1734
[10] SALJE EKH, 1994, EUR J SOL STATE INOR, V31, P805

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