Efficient nanofabrication is still the problem awaiting solution in the nanotechnology field. Such nanofabrication should involve both economy and ecology-friendly process which produces high performance materials or devices. As seen in semiconductor industry, these fabrication technologies generally consume a large amount of energy under high-vacuum and/or high-temperature conditions. There is a strong need to switch to processes which are both eco-friendly and low-cost. Therefore pinpoint nanofabrication via eco-friendly process seems to be most promising.

From the viewpoint, we have developed nanoscale electrocrystallization for nanodevice fabrication.¹ This method allows everyone to grow nanocrystals, which consist of π-conjugated molecules, site-selectively within a gap between two electrodes fabricated on a substrate. In addition, this method also allows for the gap between the two electrodes to be bridged by the formed nanocrystals.

· Magnetic field effect devices

Magnetic field effect devices were designed by using dicyanoiron(III)phthalocyanine ([Fe(Pc)(CN)₂]^-) tetraphenylphosphonium (TPP⁺) salt as a starting material of nanoscale electrocrystallization. The electrolysis gave nanocrystals that exhibited a strong correlation between the localized spin and conduction electrons, TPP·[Fe(Pc)(CN)₂]₂ was obtained. A negative giant magnetoresistance was first observed as an organic nanocrystal.² Moreover, an angular dependence of the negative giant magnetoresistance that originates from the highly oriented growth of the nanocrystals was also observed.

· Electronic field effect devices

Electronic field effect devices such as field-effect transistors (FETs) were designed by using materials for organic conductors. A bottom-gate type FET structure was simply obtained when a silicon substrate with oxide layer was used for an electrode substrate. The two electrochemical electrodes were reused as source and drain electrodes. FET characteristics showed current enhancement in some kinds of samples.³ The device fabrication was also demonstrated via an eco-friendly and non-vacuum process using a material printer.⁴

Further details of fabrication, materials, and physical properties will be reported.

References

1. H. Hasegawa, T. Kubota, S. Mashiko, Thin Solid Films, 2003, 438–439, 352–355; H. Hasegawa, T. Kubota, S. Mashiko, Electrochim. Acta, 2005, 50, 3029–3032; H. Hasegawa, R. Ueda, T. Kubota, S. Mashiko, Thin Solid Films, 2006, 499, 289–292.

2. H. Hasegawa, M. Matsuda, H. Tajima, J. Mater. Chem. C, 2013, 1, 6416–6421.

3. H. Hasegawa, J. Mater. Chem. C, 2013, 1, 7890–7895; H. Hasegawa, New J. Chem., 2013, 37, 2271–2274; H. Hasegawa, Sci. Adv. Mater., 2014, 6, 1548-1552.

4. H. Hasegawa, Appl. Mater. Today, 2017, 9, 487–492.