Floating-Gate Type Organic Memory with Organic Insulator Thin Film of Plasma Polymerized Methyl Methacrylate

Abstract

Ferroelectric (Pb,Sr)TiO 3 (PST) thin films with a perovskite structure were prepared by the sol-gel technique. PST precursor solutions were prepared from lead (II) acetate, titanium tetraisopropoxide, and strontium acetate hemihydrate with solvents of acetic acid and 2-methoxyethanol. The PST film fabricated on an Ir/SiO 2 /Si substrate with a perovskite structure exhibited a ferroelectric hysteresis curve. The Pb/Sr ratio of the PST films could be controlled, however the Ti composition was larger than the stoichiometric value. It is important to obtain stoichiometric PST films for device applications, such as ferroelectric random access memories and piezoelectric filters.

Floating-gate type organic memory device with organic insulator film of plasma polymerized styrene

“…5 and 6, the OTFT device reveals distinctive memory effect for both of the double sweep procedure, and the memory effect is even larger for the case of double sweep from +30 to ¹30 V. Electrons or holes stored in pseudo-memory layer (ppS) caused increase or decrease of induced channel in semiconductor (pentacene) corresponding to change of capacitance value of the ppS gate dielectric. 17) It was reported that polystyrene thin film obtained from a wet process revealed a charge-storage effect, 24) and it could be thought that the ppS in this report shows also a similar charge-storage effect, which might be an origin for the hysteresis in the I-V characteristic curve for the OTFT device.…”

“…Configuration and process control are described in the previous report in more detail. 16,17) A base vacuum of 10 ¹7 Torr was obtained in the reaction chamber by rotary and turbo pump. To deposit the ppS thin film, process conditions were fixed: (1) working pressure of 10 mTorr; (2) rf power of 100 W; (3) substrate bias of 10 W; (4) plasma source to substrate distance of 50 mm; (5) deposition time of 40 min.…”

“…In case of the floating-gate type organic memory, the memory effect is enhanced by the additional floating-gate layer of Au in combination of the pseudo-charge-storage effect by the tunneling of ppS. 24,25) Performance of the ppS based floating-gate type organic memory is even better than that of the floating-gate type organic memory device with a plasma polymerized methyl methacrylate (ppMMA) as gate insulator in our previous report, 17) which confirms that the ppS shows better charge-storage property than that of the ppMMA for application in floating-gate type organic memory device. Hysteresis voltage at both of double sweep procedure was depicted in Fig.…”

“…Performance of a floating-gate type memory device is decided by charge-storage property in floating gate, and thin film of Au has been proposed due to superior charge-storage characteristic. 17) In this study, the Au thin film was deposited by vacuum thermal evaporation process. The Au floating gate revealed a thickness of 7 nm after ellipsometry and showed homogeneous thickness distribution (root-mean-square of 0.8 nm) after atomic force microscopy (AFM).…”

“…Plasma polymerization deposition technique has been successfully used for preparation of polymer insulator for organic semiconductor devices. [15][16][17] In this report, plasma polymerized styrene (ppS) thin films were prepared by a plasma enhanced chemical vapor depo-sition (PECVD) technology using an inductively coupled plasma (ICP) source. Composition and electrical behavior of the ppS thin films were investigated for application in floating-gate type organic memory device, where the ppS thin film was used as gate insulator as well as tunneling layer.…”