Selected deposition of high-quality aluminum film by liquid process.

For generation of a fine aluminum pattern by conventional vacuum processing, it is necessary not only to use complex and costly instruments but also to perform an additional etching process, which may result in physical and chemical damage to the target film surface. Herein we report a simple solution process for the selected deposition of an Al pattern. Al is obtained from the decomposition of alane under dehydrogenation catalysis of a Pt nanocrystalline pattern on a substrate at ∼105-120 °C, while the self-decomposition of alane in solution is avoided in the presence of high-boiling-point amine. This deposited film generates Al crystals with a diameter of several hundred nanometers, following an epitaxial growth to a continual film. The obtained film shows high conductivity, with a resistivity close to that of bulk Al.

Deposition of platinum patterns by a liquid process.

In contrast to the traditional chemical vapor deposition technique under high vacuum, we introduce a deposition method in liquid to prepare Pt patterns on substrate near 100 °C by seed growth.

Preparation of large thermally stable platinum nanocubes by using solvent-thermal reaction.

We describe the synthesis of single-crystalline Pt nanocubes with a large diameter (around 35 nm) using a solvent-thermal reaction in a polarity-controlled mixture of 1-butanol, toluene, and N,N-dimethylformamide at 185 °C.

Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents.

Cyclopentasilane (CPS) and polydihydrosilane, which consist of hydrogen and silicon only, are unique materials that can be used to produce intrinsic silicon film in a liquid process, such as spin coating or an ink-jet method. Wettability and solubility of general organic solvents including the above can be estimated by Hamaker constants, which are calculated according to the Lifshitz theory. In order to calculate a Hamaker constant by the simple spectral method (SSM), it is necessary to obtain absorption frequency and function of oscillator strength in the ultraviolet region. In this report, these physical quantities were obtained by means of an optical method. As a result of examination of the relation between molecular structures and ultraviolet absorption frequencies, which were obtained from various liquid materials, it was concluded that ultraviolet absorption frequencies became smaller as electrons were delocalized. In particular, the absorption frequencies were found to be very small for CPS and polydihydrosilane due to sigma-conjugate of their electrons. The Hamaker constants of CPS and polydihydrosilane were successfully calculated based on the obtained absorption frequency and function of oscillator strength.

Solution-processed silicon films and transistors.

The use of solution processes-as opposed to conventional vacuum processes and vapour-phase deposition-for the fabrication of electronic devices has received considerable attention for a wide range of applications, with a view to reducing processing costs. In particular, the ability to print semiconductor devices using liquid-phase materials could prove essential for some envisaged applications, such as large-area flexible displays. Recent research in this area has largely been focused on organic semiconductors, some of which have mobilities comparable to that of amorphous silicon (a-Si); but issues of reliability remain. Solution processing of metal chalcogenide semiconductors to fabricate stable and high-performance transistors has also been reported. This class of materials is being explored as a possible substitute for silicon, given the complex and expensive manufacturing processes required to fabricate devices from the latter. However, if high-quality silicon films could be prepared by a solution process, this situation might change drastically. Here we demonstrate the solution processing of silicon thin-film transistors (TFTs) using a silane-based liquid precursor. Using this precursor, we have prepared polycrystalline silicon (poly-Si) films by both spin-coating and ink-jet printing, from which we fabricate TFTs with mobilities of 108 cm2 V(-1) s(-1) and 6.5 cm2 V(-1) s(-1), respectively. Although the processing conditions have yet to be optimized, these mobilities are already greater than those that have been achieved in solution-processed organic TFTs, and they exceed those of a-Si TFTs (< or = 1 cm2 V(-1) s(-1)).