Direct probe of heterojunction effects upon photoconductive properties of TiO2 nanotubes fabricated by atomic layer deposition

被引：53

作者：

Chang, Yung-Huang ^{[1
]}

Liu, Chien-Min ^{[1
]}

Tseng, Yuan-Chieh ^{[1
]}

Chen, Chih ^{[1
]}

Chen, Chia-Chuan ^{[2
]}

Cheng, Hsyi-En ^{[2
]}

机构：

[1] Natl Chiao Tung Univ, Dept Mat Sci & Engn, Hsinchu 30010, Taiwan

[2] So Taiwan Univ, Dept Electroopt Engn, Tainan 710, Taiwan

来源：

NANOTECHNOLOGY | 2010年 / 21卷 / 22期

关键词：

SOLAR-CELLS; WATER; ARRAYS; SIZE; PHOTODETECTORS; PHOTORESPONSE; TRANSPORT; SCHOTTKY;

D O I：

10.1088/0957-4484/21/22/225602

中图分类号：

TB3 [工程材料学];

学科分类号：

0805 ; 080502 ;

摘要：

This study investigated Schottky- and ohmic-contact effects upon the photoresponses of ITO/TiO2/Si and Ti/TiO2/Si nanotube-based photodiodes. The TiO2 tube arrays were fabricated by atomic layer deposition (ALD) and shaped by an anodic aluminum oxide (AAO) template on a p-type Si substrate. The contact area between the electrode (Ti or ITO) and the TiO2's tip was varied by tuning the tube's inner wall thickness with ALD, providing a direct and systematic probe of the heterojunction effects upon the photodiodes' responses. Results show that the Ti/TiO2/Si diode exhibits a highly thickness-dependent photoresponse. This is because the photocurrent is driven by the p-n junction at TiO2/Si alone and it faces no retarding at the ohmic contact of Ti/TiO2. For the ITO/TiO2/Si diode, the Schottky contact at ITO/TiO2 regulates photocurrent overriding TiO2/Si as a result of higher efficiency in photogeneration, leading to the opposite response compared with the Ti/TiO2/Si diode. Respective energy band diagrams are provided to support the statements above, and a consistent picture is obtained for both time response and quantum efficiency measurements.

引用

页数：7

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