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首页> 外文期刊>ACS applied materials & interfaces >Particle Consolidation and Electron Transport in Anatase TiO2 Nanocrystal Films
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Particle Consolidation and Electron Transport in Anatase TiO2 Nanocrystal Films

机译：锐钛矿TiO2纳米晶体膜中的颗粒固结和电子传输

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摘要

A sequence of chemical vapor synthesis and thermal annealing in defined gas atmospheres was used to prepare phase-pure anatase TiO_(2) nanocrystal powders featuring clean surfaces and a narrow particle size distribution with a median particle diameter of 14.5 ± 0.5 nm. Random networks of these nanocrystals were immobilized from aqueous dispersions onto conducting substrates and are introduced as model systems for electronic conductivity studies. Thermal annealing of the immobilized films at 100 °C < T < 450 °C in air was performed to generate particle–particle contacts upon virtual preservation of the structural properties of the nanoparticle films. The distribution of electrochemically active electronic states as well as the dependence of the electronic conductivity on the Fermi level position in the semiconductor films was studied in aqueous electrolytes in situ using electrochemical methods. An exponential distribution of surface states is observed to remain unchanged upon sintering. However, capacitive peaks corresponding to deep electron traps in the nanoparticle films shift positive on the potential scale evidencing an increase of the trapping energy upon progressive thermal annealing. These peaks are attributed to trap states at particle–particle interfaces in the random nanocrystal network (i.e., at grain boundaries). In the potential region, where the capacitive peaks are detected, we observe an exponential conductivity variation by up to 5 orders of magnitude. The potential range featuring the exponential conductivity variation shifts positive by up to 0.15 V when increasing the sintering temperature from 100 to 450 °C. Importantly, all films approach a potential- and sintering-temperature-independent maximum conductivity of ～10~(–4) Ω~(–1)·cm~(–1) at more negative potentials. On the basis of these results we introduce a qualitative model, which highlights the detrimental impact of electron traps located on particle–particle interfaces on the electronic conductivity in random semiconductor nanoparticle networks.
机译：使用定义的气体环境中的化学蒸汽合成和热退火的序列制备相纯锐钛矿TiO_（2）纳米晶体粉末，具有清洁表面和窄粒度分布，中值粒径为14.5±0.5nm。将这些纳米晶体的随机网络从含水分散体固定到导电基板上，并被引入作为电子电导性研究的模型系统。在100℃的空气中，在空气中的固定膜的热退火进行，以在虚拟保存纳米颗粒膜的结构性质时产生颗粒粒子触点。使用电化学方法在原位的水性电解质中研究了电化学活性电子状态的分布以及电子电导率对半导体膜中的FERMI水平位置的依赖性。观察到表面状态的指数分布在烧结时保持不变。然而，对应于纳米粒子膜中的深电子阱的电容峰值在逐渐热退火时向潜在的尺度移动正尺度的阳性尺度。这些峰值归因于在随机纳米晶体网络（即，在晶界）中的颗粒颗粒界面处的陷阱状态。在检测到电容峰值的潜在区域中，我们观察指数电导率变化最多5个幅度。当将烧结温度从100至450℃增加烧结温度时，具有指数电导率变化的潜在范围在烧结温度增加到0.15V。重要的是，所有薄膜在更负电位下接近〜10〜（-4）Ω〜（-1）·cm〜（-1）的电位和烧结温度最大导电率。在这些结果的基础上，我们介绍了一种定性模型，该模型突出了位于随机半导体纳米粒子网络中的电子电导率上的粒子粒子界面上的电子捕集器的有害冲击。

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