Non-volatile n+-TiO2 channel FETs with ferroelectric HfO2

Ferroelectric FETs (Fe-FETs) have been investigated for many years, because it may offer versatile opportunities in terms of low-power nonvolatile FETs. Recently, ferroelectric HfO2 was found experimentally [1], and has been investigated for various promising applications, because HfO2 is now dominantly used for advanced CMOS gate stacks. Substantial challenges of ferroelectric FETs for advanced device design are how to control the interface with semiconductors as well as the ferroelectric material properties. Furthermore, since the polarization charges are always too high for conventional semiconductor channels, it is required to reconsider the semiconductor material as well as appropriate FET structure. This paper discusses opportunities of ferroelectric FETs using doped HfO2 on an oxide semiconductor channel, and demonstrates its nonvolatile FET performance. Please click Additional Files below to see the full abstract

Thermal oxidation kinetics of germanium

We have studied Ge gate stacks for many years, and demonstrated very interesting properties in Ge [1]. Recently we have published a review paper on Ge from viewpoints of device and process for CMOS applications. Through this study, we have noticed that GeO2/Ge is so different from SiO2/Si. It means that the oxidation kinetics of Ge should be studied carefully and understood correctly, though that of Si is almost understood. We carried out the oxygen isotope (18O) tracing experiments in Ge oxidation process. Figure 1 shows a comparison between Si oxidation and Ge one, inspected by the SIMS. First, we prepared SiO2/Si and GeO2/Ge oxidized in 16O2, then both were reoxidized in 18O2. SIMS results clearly exhibit a significant difference of 18O profile in the oxides. The result in SiO2/Si system is as expected by the Deal-Grove type kinetics, while that in GeO2/Ge shows rather flat profile of 18O in GeO2 and not 18O accumulation at GeO2/Ge interface. The results demonstrate a significant difference of oxidation kinetics between Si and Ge. Please click Additional Files below to see the full abstract

Carrier density dependent energy band-gap and phonon frequency in Ge

Dopant atoms in nano-devices should be countable and dopant atom discreteness cannot be ignored. The energy band- gap and phonon frequency in a semiconductor are, however, believed to be material-specific constants except quantum size effects, though apparent band-gap narrowing and phonon-softening in doped semiconductors have been experimentally reported and theoretically discussed [1, 2]. On the other hand, in doped semiconductors, it is experimentally difficult to differentiate dopant effects from free carrier ones. Thus, the objective of this study is to separate the dopant from free carrier effects on “intrinsic properties in Ge” experimentally, and to discuss about their physical implications. Lightly doped GeOI wafers were used. Bottom gated FETs were fabricated with Y2O3 passivation on the top surface [3], as shown in Fig. 1. Thanks to this sample structure, PL and Raman investigations were successfully carried out for a same sample as a function of the bottom gate bias, from the top surface without being masked by the top gate metal. Please click Additional Files below to see the full abstract

ニワトリの神経におけるCholinesteraseの軸索内移動

1. The axoplasmic transport of cholinesterases was investigated in chicken vagus and sciatic nerve trunks by the ligature method. 2. Even 48 hours after ligation, the nerve segments in which the increased activity of acetylcholinesterase (AChE) was observed were ristricted within 5mm from the ligature. The activity of AChE in these segments increased linearly until 24 hours or 48 hours after ligation. 3. Two ligatures were made on sciatic nerve trunks and the change in activity of AChE between them was investigated. And it was found that only about 13% of AChE was moved by fast flow. The velocity was 233. 8mm/day in the anterograde and 97.7mm/day in the retrograde direction. 4. The activity of pseudo-cholinesterase (Ps-ChE) also accumulated with time at the proximal and distal side of the ligature

Studies on the Prevention of Leucocytozoon Infection of the Chicken. : IV. The Ecological Findings of Culicoides arakawae.

The following researchs have been carried out on the behavior of Culicoides arakawae, the intermediate host of leucocytozoon infection of the chicken. From 1961 to 1964, C. arakawae have been collected by a light trap once or twice every week at the hen house of our laboratory and a farmer's hen house at Hataayu, Makiishi in Okayama, city. The following items were also investigated: 1.)the successive change of the number of C. arakawae flied into the hen house in the evening, 2.)the number of C. arakawae caught by an insect net at various heights, 3.)the successive change of the number of C. arakawae caught by a light trap placed in the hen house. The results obtained were as follows. 1. C. arakawae comes flying into the hen house when the mean temperature is higher than 10℃. But, when the mean temperature is higher than 10℃, there are no clear correlation between the temperature, humidity and weather and the number of C. arakawae caught by light trap. The sex ratio of C. arakawae caught by a light trap varies with temperature, and the higher the temperature is, the greater is the percentage of the female. The ratio of engorged females to the whole females also varies with temperature. When the temperature is lower than 20℃, the percentage of engorged females is almost always below 50. When the temperature is higher than that, the percentage is from 70 to 90. 2. The number of C. arakawae caught by a light trap placed in the hen house shows the normal distribution with the central axis at 2 am. 3. It is probably certain that C. arakawae does not hibernate in the imaginal stage in the neighbourhood of Okayama city. 4. The number of C. arakawae come flying into the hen house in the evening, is most numerous during one hour following sunset. And in the summer season, in the flies caught by a light trap placed in the hen house, the percentage of females is usually far greater than that of males, but the sex ratio of C. arakawae, come flying into the hen house, is about 1:1. 5. C. arakawae usually flies below 20 m on the ground

Studies on the Prevention of Leucocytozoon Infection of the Chicken. : VI. The Observation of the Gametocytes of Leucocytozoon caulleryi in the Unstained Wet Blood Film.

Usually the diagnosis of the infected chickens with leucocytozoon disease has been made by finding gametocyte of Leucocytozoon caulleryi in the blood smear stained by Giemsa's or May-Grunwald's method. But, as the inner part of the gametocyte can be observed in the unstained wet film of blood, the feature of the gametocyte considerably differs from that of the fixed sample. Method: One drop of blood from an affected chicken is placed on a cover-glass. This is inverted on a slide and the preparation is rimmed with paraffin. Then it is examined with phase-contrast microscopy at 37℃. Results and considerations: In macrogametocyte, the nucleus is rather small, usually have a curved or twisted rod shape and is suspended in protoplasm. The protoplasm is rich and filled with the immense number of fine granules. But in an usual smear sample, the nucleus shrinks and is covered with the granules at the time of smearing, and yet the granules are stained in dark purple by Giemsa's method, and hence it is considered that the shape of the nucleus is obscured. In microgametocyte, the nucleus is globular or oval, rather large in size compared with the size of the gametocyte itself, and placed at the nearly central point of the cell. The granules of protoplasm are a little larger in size and less in number than that of the macrogametocyte, and as the most of the granules are attached around the nucleus, these look like a pearl necklace in an optical section. As the nucleus expands at the time of smearing, it extends on nearly the whole surface of gametocyte and the protoplasm is seen indistinctly around it. As the granules are attached to the nucleus, they scatter on the surface of the nucleus as it expands. Most of the macro- and microgametocyte are covered with the membrane of the host cell. These cell membranes contain semifluid thinner than the protoplasm of the parasite. Some of which contain the granules of various sizes and they present the vivid Brownian motion. But these granules cannot be stained with Giemsa's dye

Studies on the Prevention of Leucocytozoon Infection of the Chicken : III. The Preventive Effect of Diaveridine.

1.diaveridineを飼料に最高0.01%から最低0.0001%までの各種の濃度になるように添加して,これを連続投与して本病の感染予防試験を行なった.その結果0.01%ならびに0.005%添加区においては感染が認められなかったが0.0025%以下の添加濃度では感染鶏が高率に認められた.従って本剤の最低有効濃度は一応0.005%の附近にあると思われる.しかしながら1964年度は,全国的に本病の予防剤としてpyrimethamineが発売されたため,岡山県下でも本病の発生が少なく,岡山大学農学部構内の鶏舎でも本病の感染率が一般に低かった.すなわち第1区の無添加対照区の感染率は35.0%であり,同時に行なった他の試験でも,薬剤無添加区での感染率は20～30%が普通であって,第1試験でみられたような濃厚感染は認められなかった.第2試験の0.001%添加区で81.3%の感染率を示したのはむしろ例外的現象と考えられる.従って第2試験の0.005%添加区がもしさらに濃厚な感染に曝された場合,果して完全に本病の感染を防ぎ得るか否かは疑問であるので,本剤を実地に応用する場合,最低有効濃度は0.005%より上にあると考えた方が安全と思われる.2.試験期間中における試験鶏の体重,産卵率,卵重等の推移を各区別の平均値で図示したように,いずれの場合も本剤がニワトリに対して毒性を示しているとは認められなかった.ただし第1図で,8月1日以後第3区および第4区の平均体重曲線が降下しているのは,第3区で2羽第4区で1羽がそれぞれ内臓型淋巴腫症に罹患し,体重が900gないし660gに減少したものが出たためであるが,8月29日現在の体重で,無添加対照区との間でF検定を行なっても5%の水準において有意の差は認められていない.第2図の平均産卵率の曲線についても,同様な傾向が見られるが,これも前記と同じ理由によるものと考えられ,期間中の総産卵個数について,対照区と各区の間でF検定を行なったが,いずれの場合も有意の差は認められなかった.3.ニワトリのcoccidium症に対するdiaveridineの効果は,前記の通りM. L. Clark3)によれば,sulfa剤と混じた場合0.001%であるといい,同じくpyrimethamineの効果は,S. B. Kendall&L. P. Joyner5)によると,sulfa剤と混合した場合0.004%が適当と認めている.従って,この両者はニワトリのcoccidiim症に対してはほぽ同等の効力を有しているものと見られるが,ニワトリのleucocytozoon病に対するpyrimethamineの最低有効濃度は著者ら2)の成績では0.00005%であるのに反し,diaveridineは前記の通り0.005%であるとすると,本病の予防効果では両者の間に100倍の開きが認められるわけであって興味深いことである.4.以上の試験により本剤単味の場合の最低有効濃度がほぼ0.005%であると判明したが,この濃度では実際の野外での応用の場合薬価の点で問題を生ずる恐れがある.したがってsulfa剤と混合投与した場合その相乗効果によりさらに投与濃度をさげる研究が行なわれないと本剤単味では応用範囲が限定されると考えられる

Studies on the Prevention of Leucocytozoon Infection of the Chicken. : V. The Leucocytozoon Infection in the Yearling Hen.

The investigations were carried out about the reinfection with leucocytozoon disease in yearling hens that were infected with this disease in the preceding year. From the investigations carried out in 1962, 1963 and 1964, the following results were obtained. 1. Among the 20 hens once infected with this parasite, the reinfection was not at all found in the same and the following years by the microscopic examination of blood smear sample made once every week. 2. Among the 22 yearling hens that were completely protected from leucocytozoon infection in the preceding year by the use of pyrimethamine or sulfadimethoxine, it was found by the blood examination that 11 hens (50%) were infected with this disease in the following year. 3. Eleven hens, in the blood of which no gametocyte had been detected in spite of the fact that they had been among the highly infected flock, were not at all infected in the following year. From the results mentioned above, we have come to the following conclusions. Hens recovered from natural infection of leucocytozoon disease acquire the strong immunity later. And the effect of pyrimethamine and sulfadimethoxine used in these experiments are quite perfect