Influence of annealing process on conductive properties of Nb-doped TiO2 polycrystalline films prepared by sol–gel method

Liu, Jinming; Zhao, Xiaoru; Duan, Libing; Cao, Minjuan; Sun, Huinan; Shao, Jifeng; Chen, Shuai; Xie, Haiyan; Chi, Xiao; Chen, Changle

doi:10.1016/j.apsusc.2011.07.009

Cited by 46 publications

(14 citation statements)

References 16 publications

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“…28 TiO 2 -based high electronic conductivity transparent conducting oxide systems such as Nb-doped TiO 2 have been investigated recently and are expected to exhibit significantly higher temperature stability than AZO films. 29 While more detailed experimental results for Nb-doped TiO 2 films will be presented in the future, preliminary results such as those presented in Figure 8 for 5 at. % Nb-doped TiO 2 films suggest that large and stable optical gas sensing responses can be achieved at temperatures greater than $500 C in doped TiO 2 -based systems.…”

Section: High Temperature Stable Gas Sensing Responses In Nb-doped Timentioning

confidence: 97%

Optical gas sensing responses in transparent conducting oxides with large free carrier density

Ohodnicki

Andio

Wang

2014

Journal of Applied Physics

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Inherent advantages of optical-based sensing devices motivate a need for materials with useful optical responses that can be utilized as thin film functional sensor layers. Transparent conducting metal oxides with large electrical conductivities as typified by Al-doped ZnO (AZO) display attractive properties for high temperature optical gas sensing through strong optical transduction of responses conventionally monitored through changes in measured electrical resistivity. An enhanced optical sensing response in the near-infrared and ultraviolet/visible wavelength ranges is demonstrated experimentally and linked with characteristic modifications to the dielectric constant due to a relatively high concentration of free charge carriers. The impact of light scattering on the magnitude and wavelength dependence of the sensing response is also discussed highlighting the potential for tuning the optical sensing response by controlling the surface roughness of a continuous film or the average particle size of a nanoparticle-based film. The physics underpinning the optical sensing response for AZO films on planar substrates yields significant insight into the measured sensing response for optical fiber-based evanescent wave absorption spectroscopy sensors employing an AZO sensing layer. The physics of optical gas sensing discussed here provides a pathway towards development of sensing materials for extreme temperature optical gas sensing applications. As one example, preliminary results are presented for a Nb-doped TiO2 film with sufficient stability and relatively large sensing responses at sensing temperatures greater than 500 °C.

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Section: High Temperature Stable Gas Sensing Responses In Nb-doped Timentioning

confidence: 97%

Optical gas sensing responses in transparent conducting oxides with large free carrier density

Ohodnicki

Andio

Wang

2014

Journal of Applied Physics

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“…The sol-gel process has distinct advantages over other techniques, including excellent compositional control, homogeneity at the molecular level due to the mixing of liquid precursors, and lower crystallization temperature [123][124][125][126]. Moreover, the microstructure (i.e., the pore size, pore volume, and surface area) of films can be tailored by controlling the processing parameters such as the ratio of the components and temperature [127].…”

Section: Sol-gelmentioning

confidence: 98%

Recent developments in TiO2 as n- and p-type transparent semiconductors: synthesis, modification, properties, and energy-related applications

2015

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TiO 2 -based thin films and nanomaterials have been fabricated via physical and solution-based techniques by various research groups around the globe. Generally, most applications of TiO 2 involve photocatalytic activity for water and air purification, self-cleaning surfaces, antibacterial activity, and superhydrophilicity. As a widebandgap semiconductor, modified TiO 2 belongs to a class of materials called transparent semiconducting oxides (TSOs), which are simultaneously optically transparent and electrically conductive. TSOs continue to be in high demand for a variety of applications ranging from transparent electronics and sensor devices to light detecting and emitting devices in telecommunications. However, reports on TiO 2 applications as an effective TSO for transparent electronics applications have been limited. In general, TiO 2 is intrinsically an n-type semiconductor but can be doped to have p-type semiconductivity. This provides a very important opportunity to fabricate all-transparent homojunction devices for light harvesting and energy storage. P-type TSOs have recently attracted tremendous interest in the field of active devices for emerging transparent electronics for potential use in ultra-violet light-based solar cells. Therefore, a detailed overview of the synthesis, band structure modification via doping, properties, and applications of modified TiO 2 as n-and p-type TSOs is warranted. This article comprehensively reviews the latest developments. The discussion includes solution-based wet chemical techniques and vacuum-based dry physical techniques fabricating TiO 2 -TSOs. The synthesis of p-TiO 2 in particular is discussed in detail as it may provide interesting breakthroughs in emerging transparent electronics applications. Also, the structural, optical, and electrical properties of TiO 2 are discussed in the context of TSO applications, specifically the defect chemistry of TiO 2 to obtain n-and p-type semiconductivity, which could provide interesting insights into the band structure engineering of TiO 2 for conductivity reversal. Applications of both nand p-type TiO 2 have been reviewed in detail in relation to thin film transparent homo/heterojunction devices, dyesensitized solar cells, electrochromic displays, and other energy-related applications.

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“…The ionic radius of Nb 5+ of 0.064 nm is slightly larger than Ti 4+ of 0.0605 nm. Therefore, Nb 5+ works as an n-type dopant in TiO 2 lattice and generates additional carriers in its CB, which can notably increase photocatalytic performance [181][182][183][184][185][186].…”

Section: Niobium (Nb) Dopingmentioning

confidence: 99%

Influences of Doping on Photocatalytic Properties of TiO2 Photocatalyst

Huang¹,

Yan²,

Zhao³

2016

Semiconductor Photocatalysis - Materials, Mechanisms and Applications

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As a kind of highly effective, low-cost, and stable photocatalysts, TiO 2 has received substantial public and scientific attention. However, it can only be activated under ultraviolet light irradiation due to its wide bandgap, high recombination, and weak separation efficiency of carriers. Doping is an effective method to extend the light absorption to the visible light region. In this chapter, we will address the importance of doping, different doping modes, preparation method, and photocatalytic mechanism in TiO 2 photocatalysts. Thereafter, we will concentrate on Ti 3+ self-doping, nonmetal doping, metal doping, and codoping. Examples of progress can be given for each one of these four doping modes. The influencing factors of preparation method and doping modes on photocatalytic performance (spectrum response, carrier transport, interfacial electron transfer reaction, surface active sites, etc.) are summed up. The main objective is to study the photocatalytic processes, to elucidate the mechanistic models for a better understanding the photocatalytic reactions, and to find a method of enhancing photocatalytic activities.

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Influence of annealing process on conductive properties of Nb-doped TiO2 polycrystalline films prepared by sol–gel method

Cited by 46 publications

References 16 publications

Optical gas sensing responses in transparent conducting oxides with large free carrier density

Optical gas sensing responses in transparent conducting oxides with large free carrier density

Recent developments in TiO2 as n- and p-type transparent semiconductors: synthesis, modification, properties, and energy-related applications

Influences of Doping on Photocatalytic Properties of TiO2 Photocatalyst

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