Hideharu Tamura

Photopolymerization of monomolecular films with diacetylene bonds on an aqueous subphase

Abstract The photoreactivity of monomolecular films of a diacetylene derivative (10,12-pentacosadiynoic acid (PDA)) under UV irradiation has been investigated at the air-water interface. With decreasing molecular area, the reactivity of the Langmuir film (the Langmuir film is the monomolecular film on an aqueous subphase) decreased, and the colour transition of the Langmuir film polymerized by the UV irradiation was from blue to red. Furthermore, the colour transition (blue to red) was also caused by heating the polymerized Langmuir-Blodgett (LB) films at about 60°C. The colour transition of the polymerized PDA Langmuir film exhibited reversibility at the air-water interface when the condition of the subphase was changed, but that of the LB films did not exhibit reversibility. In the differential scanning calorimetry diagrams, the PDA LB films had an endothermal peak a 67°C, but the polymerized film had two peaks at about 70 and 200°C. These results indicate that the photoreactivity of the PDA monomolecular film at the air-water interface was affected by the molecular arrangement and density, and the colour transition of the PDA polymer may be caused by the structural disorder of the side-groups joined to the polymer backbone.

Electrical evaluation of ultrathin organic films on solid substrates

Abstract We established two evaluation methods for monolayer-order organic films on solid substrates and evaluated various kinds of films, i.e. Langmuir-Blodgett films of monoalkyl lipids, dialkyl lipids, dialkylsilane, and fluorocarbon, and chemically adsorbed films of three kinds of trichlorosilane compounds. One method is the measurement of the electroplating current during copper decoration, and the other the measurement of I–V characteristics using a micromanipulating mercury probe. Electrical characterization of the films with monolayer-order thickness is possible by using both types of liquid top electrodes, and a clear dependence of the electrical properties on monolayer number has been found quite reproducibly.

Preparation of multilayers using chemical adsorption and electron-beam irradiation

Abstract Multilayers of ω-nonadecenyl-trichlorosilane (V-NTS) have been prepared on SiO 2 /Si substrate by repeated cycles of chemical adsorption (CA) of V-NTS from a nonaqueous solution and electron-beam (EB) irradiation in air. The thickness of the multilayers was increased by a fixed value at every CA cycle. The molecular density and degree of arrangement of the V-NTS monolayer were higher than that of a ω-tricosenic acid (ωTSA) monolayer transferred onto a substrate by the Langmuir-Blodgett (LB) method. The vinyl group of V-NTS disappeared and hydroxyl, aldehyde, and/or carboxyl groups were formed when the irradiation was carried out in oxygen atmosphere, whereas imino and/or amino groups were formed when the irradiation was carried out in nitrogen atmosphere. Using this method, multilayers of high molecular density can be obtained easily.

Study on the photoreaction process of 6-octadecyl sulphane imide naphthoquinone diazide Langmuir films☆

6-octadecyl sulphane imide naphthoquinone diazide (OSN) Langmuir (L) films of different molecular arrangements or molecular densities were spread on a subphase of different temperatures and pH values and the photoreactivity of the OSN L films was investigated. The relation between molecular density or molecular arrangement and photoreactivity of the OSN molecule was studied using the method in which UV and visible absorption spectra are measured directly on the water surface during π-A curve measurement. The rate of the reaction is higher at lower temperatures and lower pH values of the subphase and at higher surface pressures, indicating that the molecular arrangement in the L film is favourable for the reaction under these conditions.

Spectroscopic Evaluation on Photosensitive Langmuir Films Using Multichannel Spectrophotometer

The UV and visible (VB) transmission spectra of monolayers of some materials having long hydrocarbon chains on a water surface (Langmuir (L) film) were obtained by the real time direct measurement using a multichannel spectrophotometer during surface pressure-area isotherm measurements. It was found that the change of surface pressure as a function of area (Π-A curve) does not always agree with that of optical absorption as a function of area, and therefore the Π-A curve does not always reflect the molecular arrangement of molecules in the L film. The rates of photochemical reaction of the L films can be studied in relation to the molecular arrangement of the monolayers using this method. The spectra of the L film which were obtained by a reflection method using polarized light were further proven to be valid in studying the molecular arrangement in the L film.

Preparation of Multilayers by Alternate Cycles of Chemical Adsorption and Electron Beam Irradiation

Multilayers of ω-nonadecenyl trichlorosilane (V-NTS) have been prepared on SiO2/Al/Si substrates by repeated cycles of chemical adsorption (CA) of V-NTS in solution and activation of terminal double bond by electron beam (EB) irradiation. The terminal double bond facing the outside of a V-NTS monolayer on the substrate reacted to form imino and/or amino groups when the irradiations were carried out in nitrogen atmosphere. This method provides a simple and rapid method of preparing multilayers with fewer defects on a large scale, which is important to the construction of the three-dimensional molecular structure.

Radiation chemical reaction and submicron pattern fabrication on 10,12-pentacosadiynoic acid LB films using X-ray irradiation

X-ray induced polymerization of 10,12-pentacosadiynoic acid (PDA) Langmuir-Blodgett (LB) films has been studied in relation to the molecular density or arrangement for use in X-ray resists. Two typical PDA LB films of different molecular densities were polymerized to form different polymer LB films by X-ray irradiation. The low-density PDA LB films (A type) were more sensitive than the high-density PDA LB films (B type) when X-ray was irradiated in helium atmosphere and the polymerization was caused topochemically on A-type film but not on B-type film. Decomposition of polymerized films was observed by excessive irradiation of X-ray for A-type film, but not for B-type film. Using both types of PDA LB films, 0.4 µm patterns could be fabricated by X-ray exposure.

Evaluation of LB Films for Excimer Laser and X-ray Resists

ハーフミクロン・ポトリソグラフィ実現のため, エキシマレーザ露光およびX線露光によりLB膜の評価を行った.評価した材料は, エキシマ用としてジアセチレン誘導体3種 (トリコサジイノイック酸 : TDA, ペンタコサジイノイック酸 : PDA, ヘプタコサジイノイック酸 : HDA) とオクタデジノレアクリル酸 : ODA, ω-トリコシイノイック酸 : TCAの5種類, X線用としてTCA, TSA, ADAの各3種類である.エキシマ露光ではPDAを用いて0.3μmパターン, X線露光ではTCAを用いて0.4μmパターンがそれぞれ形成された.エキシマレーザ露光の0.3μmは, 我々の使用したレンズの解像限界であり, X線露光の0.4μmは, 我々の入手したマスクの最小寸法である.なお, 実際にLB膜をレジストとして適用していくためには, 今後LB膜の製造能率を向上する必要がある.