Hierarchical Nanostructures for Photo-Electro-Chemical Cells - Hierarchical Nanostructures for Energy Devices - page 188

d n 3 r 4 n g | 4

Figure 8.11 (a) Schematic diagram of the LIHG process by bottom laser focusing.

Adapted with permission from ref. 66. (Copyright 2013, WILEY-VCH
Verlag GmbH & Co. KGaA, Weinheim.) (b) Tilted SEM image of the ZnO
nanowire array synthesized by LIHG. Adapted with permission from ref.
66. (Copyright 2013, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
(c) A series of SEM images of nanowires grown with varying growth time
(from 5 to 3600 s). Adapted with permission from ref. 67. (Copyright
2013, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) (d) In situ
kinetic curves that were obtained with different beam diameters under
the same laser irradiation power. The inset shows the SEM image of
Run #1 (scale bar: 20 mm). The maximum height is about 58.8 mm.
Adapted with permission from ref. 67. (Copyright 2013, WILEY-VCH
Verlag GmbH & Co. KGaA, Weinheim.)

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Although hierarchical structure synthesis by the LIHG process has not been
reported yet, the LIHG process is capable of generating hierarchical struc-
tures by just supplementing intermediate seeding procedures between each
growth. Laser-induced hydrothermal growth might be more effective for
fabricating compact devices. However, utilizing high power lasers and ex-
panding the irradiated spot suggests a promising route towards a high
throughput process.

8.4.7 Heterostructures Composed of Two or More Materials
Regarding photocatalytic activities, heterostructures composed of two or
more materials with different bandgaps provide broadband absorption.