AMORPHIZATION TRANSFORMATION BY MECHANICAL ALLOYING IN THE Mo-Si SYSTEM

1.IntroductionInrecelltyears,MoSiZhasattractedconsiderableattentionasapotentialhigh-temperaturestructuralmaterial.Thecombinationofhighmeltingpoint(2030"C),moderatedensity(6.24gcm--'),excellentoxidationresistance,andhighmodulusatelevatedtemperaturemakesMoSiZoneofthemostpromisingmatrixphasetobeusedattemperaturesupto1600oC[l].Anothermolybdenumsilicide,Mo5Si3,hasbeenproposedasapotentialreinforcementforMoSt,[1,2].AmongawidevarietyofprocessingtechniquesutilizedtosynthesizeMoSt2,mechanicalalloy…     

Avoidance of stiction in the release of highly boron doped micro-actuators fabricated using BESOI substrates

This paper presents a new technique which has been successfully applied to the fabrication of micromachined components to avoid the ‘device stiction’ often encountered during the final processing steps of micro-fabrication. Based on the use of BESOI substrates, this technique involves the heavy boron doping of the final processed structure, followed by a timed wet etch which releases the micromachined device by controllably lowering the undoped Si substrate beneath it.     

Semiconducting (Conjugated) Polymers as Materials for Solid‐State Lasers

Light‐emissive polymers are outstanding laser materials because they are intrinsically “4‐level” systems, they have luminescence efficiencies higher than 60 % even in undiluted films, they emit at colors that span the visible spectrum, and they can be processed into optical quality films by spin casting. The important materials issues are reviewed and the prospects for making polymer diode lasers are discussed.     

部分耗尽SOI体接触nMOS器件的关态击穿特性

分别采用具有硅化物和不具有硅化物的SOI工艺制成了部分耗尽SOI体接触nMOS晶体管.在体接触浮空和接地的条件下测量了器件的关态击穿特性.通过使用二维工艺器件模拟,并测量漏体结的击穿特性,详细讨论和分析了所制成器件击穿特性的差异和击穿机制.在此基础上,提出了一个提高PD-SOI体接触nMOS击穿特性的方法.     

Fluid-kinetics enhanced selective etching process of NiPt film by piranha chemistry in silicide formation for complementary metal oxide semiconductor fabrication

NiPtSi is a prime candidate for the complementary metal-oxide-semiconductors CMOS self-aligned silicidation process beyond the 22 nm node. The formation of NiPt silicide in smaller geometries demands more Platinum (Pt) additive to control the silicide quality and a more capable NiPt selective etching process to remove surface residual metals for complementing the formation of silicide. Both higher Pt selective etch rate and lower surface material loss are desired in NiPt selective etching process.High temperature (> 150 °C) sulfuric acid base piranha chemistry in fresh dispensing on wafer can etch Pt with less damage to the exposed wafer surface. By using (1) a larger mass-to-charge density Pt redox reaction zone in the electrochemistry spectrum of the Pt redox behavior, (2) stronger chemical fluid kinetics and (3) intensified voltammetric cycles, the Pt selective removal rate can be boosted. Two types of wet chemical processors are used to examine the fluid-chemical kinetics effect on the Pt selective etching rate. It is shown that higher chemical flow rates and stronger fluid-kinetics can enhance the Pt transport behavior. The collateral wafer surface material loss rate also increases by higher chemical flow rates, but the amount of total material loss actually reduces due to a greater reduction in the required process time. The fluid-kinetics enhanced selective etching process can cover a wider range of NiPt film conditions (5% Pt, up to 200 Å, 10% Pt up to 180 Å).     

Synthesis of aligned copper oxide nanorod arrays by a seed mediated hydrothermal method

The synthesis of ordered copper oxide (CuO) nanorod arrays has been obtained using a seed-mediated hydrothermal method. Aligned CuO nanorods were obtained on fluorine doped tin oxide glass substrates over a large scale at low temperature ranging from 75 to 85 °C. It is found the CuO nanoseeds play an important role to facilitate the growth of those aligned CuO nanorods. The band gap energy of the CuO nanorods was estimated by ultraviolet-visible absorption spectroscopy. The growth mechanism of this method was also investigated.     

Transient Behavior of Low Enriched Uranium Silicide Plate-Type Fuel for Research Reactors during Reactivity Initiated Accident Conditions

Abstract

This paper describes the results of transient experiments using a low enriched uranium silicide miniplate fuel for research reactor. The pulse irradiation was performed in the Nuclear Safety Research Reactor (NSRR) at the Japan Atomic Energy Research Institute (JAERI).

The results obtained in this study are summarized as follows :

(1) The tested fuel plates were damaged with energy depositions above 94 cal/g·fuel, but remained intact below 82cal/g·fuel. A failure threshold should therefore exist between these two values.

(2) Four of the fuel plates that showed peak cladding surface temperatures <330°C were damaged by the thermal stress during quenching. These damaged fuel plates revealed small intergranular cracks that propagated perpendicularly to the axial direction of the plate, from the Al cladding surface to the fuel core, without significant dimensional changes. On the other hand, when peak cladding surface temperatures were >400°C, the test fuel plates were damaged mainly by melting of the Al cladding, accompanying significant dimensional changes.

(3) The thermal stress of the damaged fuel plates calculated on the basis of the maximum transient temperature drop during quenching was greater than the tensile stress that occurred during fabrication.     

Failure Mechanism of Silicide and Aluminide Fuels During Power Transient

The quantitative failure mechanism of the silicide and aluminide fuels (the test specimens) was studied using the 4.8 g/cc silicide fuels as the references. (1) The onset of the departure from the nucleate boiling (DNB) was determined to be 188 ± 27°C for the test specimens and 182 ± 15°C for the references. The difference was insignificant. (2) The failure mechanism of both fuels was attributed to the quench stress that occurred owing to the uneven temperature profile across the fuel plate. In-core quantitative data indicated that when the temperature drop ΔT was greater than 94°C and the time to quench tq was shorter than 0.13 s, through-plate cracking could occur. (3) Irrespective of the fuel initial density, the plate bow increased with an increase in the PCST. The worst bow up to 228°C (JRR-3 operational limit) was 15%.     

Growth mechanism of epitaxial CoSi2 on Si and reactive deposition epitaxy of double heteroepitaxial Si/CoSi2/Si

The growth mechanism of epitaxial CoSi₂ was studied using Co/Ti/Si multilayer solid phase reaction. Results showed that phase formation was controlled by diffusion of Co through the growing CoSi_x, although at the early stage of CoSi₂ growth the diffusion of Co could be controlled by a Ti layer. A reactive deposition technique was also evaluated by using a conventional magnetron sputtering system. Results showed that an epitaxial CoSi₂ layer was formed by controlling the Co sputtering rate not to exceed the Co diffusion rate through CoSi_x. However, the surface of CoSi₂ became rough when the deposition rate was much slower than the Co diffusion rate through CoSi_x. The roughness was caused by the formation of CoSi₂ (111) facets at the interface between CoSi₂ and the Si substrate. Si/CoSi₂/Si double heteroepitaxial structures were fabricated when Si and Co were sequentially sputter-deposited on a Si (100) substrate.     

A new diketopyrrolopyrrole-based co-polymer for ambipolar field-effect transistors and solar cells

A new thieno[3,2-b]thiophenediketopyrrolopyrrole-benzo[1,2-b:4,5-b′]dithiophene based narrow optical gap co-polymer (PTTDPP-BDT) has been synthesized and characterized for field-effect transistors and solar cells. In field-effect transistors the polymer exhibited ambipolar charge transport behaviour with maximum hole and electron mobilities of 10⁻³ cm² V⁻¹ s⁻¹ and 10⁻⁵ cm² V⁻¹ s⁻¹, respectively. The respectable charge transporting properties of the polymer were consistent with X-ray diffraction measurements that showed close molecular packing in the solid state. The difference in hole and electron mobilities was explained by density functional theory calculations, which showed that the highest occupied molecular orbital was delocalized along the polymer backbone with the lowest unoccupied molecular orbital localized on the bis(thieno[3,2-b]thiophene)diketopyrrolopyrrole units. Bulk heterojunction photovoltaic devices with the fullerene acceptor PC₇₀BM were fabricated and delivered a maximum conversion efficiency of 3.3% under AM1.5G illumination.