Electronic characteristics of fluorene/TiO2 molecular heterojunctions.
Electronic characteristics of fluorene/TiO2 molecular heterojunctions.
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芴/TiO2分子异质结的电子特性。
DOI：
10.1063/1.2423011
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
R. McCreery
中科院分区：
文献类型：
--
作者：
Jing Wu;Ken Mobley;R. McCreery
作为由分子单层和半导体氧化物组成的“分子异质结”的例子，一般类型的碳/分子/TiO 2 Au的分子结的电子性质进行了检查。将含有芴键合到热解光致抗蚀剂膜（PPF）的结与含有Al 2 O3而不是芴的结以及仅具有TiO 2层的结进行比较。对电压扫描和脉冲刺激的反应强烈依赖于结的组成和温度。持续几毫秒的瞬态电流响应的结果从注入和捕获的电子在TiO 2层，并发生在所有三个结类型的研究。PPFTiO 2 Au结中的传导在低电压下与空间电荷限制的传导一致，然后一旦空间电荷填充所有陷阱，电流急剧增加。与芴存在，有一个较慢的，持久的变化，在结电导，可以删除的反极性脉冲。这种“记忆”效应归因于TiO 2中的氧化还原过程，其产生TiIII和/或TiII，由于导带电子的存在，TiIII和/或TiII具有比TiO 2高得多的电导。氧化还原过程相当于通过施加的电场对TiO 2层的“动态掺杂”。记忆效应是由分子层和氧化物层的性质结合而产生的，是分子异质结结构的一种特殊性质。
The electronic properties of molecular junctions of the general type carbon/molecule/TiO2Au were examined as examples of "molecular heterojunctions" consisting of a molecular monolayer and a semiconducting oxide. Junctions containing fluorene bonded to pyrolyzed photoresist film (PPF) were compared to those containing Al2O3 instead of fluorene, and those with only the TiO2 layer. The responses to voltage sweep and pulse stimulation were strongly dependent on junction composition and temperature. A transient current response lasting a few milliseconds results from injection and trapping of electrons in the TiO2 layer, and occurred in all three junction types studied. Conduction in PPFTiO2Au junctions is consistent with space charge limited conduction at low voltage, then a sharp increase in current once the space charge fills all the traps. With fluorene present, there is a slower, persistent change in junction conductance which may be removed by a reverse polarity pulse. This "memory" effect is attributed to a redox process in the TiO2 which generates TiIII and/or TiII, which have much higher conductance than TiO2 due to the presence of conduction band electrons. The redox process amounts to "dynamic doping" of the TiO2 layer by the imposed electric field. The memory effect arises from a combination of the properties of the molecular and oxide layers, and is a special property of the molecular heterojunction configuration.