增强型AlGaN/GaN高电子迁移率晶体管高温退火研究

深入研究了两种增强型AlGaN/GaN高电子迁移率晶体管(HEMT)高温退火前后的直流特性变化.槽栅增强型AlGaN/GaN HEMT在500 ℃ N₂中退火5 min后,阈值电压由0.12 V正向移动到0.57 V,器件Schottky反向栅漏电流减小一个数量级.F注入增强型AlGaN/GaN HEMT在 400 ℃ N₂中退火2 min后,器件阈值电压由0.23 V负向移动到-0.69 V,栅泄漏电流明显增大.槽栅增强型器件退火过程中Schottky有效势垒     

The ground-state entanglement in the spin-XX chain with a magnetization current

The ground-state entanglement in a transverse spin-1/2 XX chain with a magnetization current is studied. By introducing a magnetization current to the system, a quantum phase transition to current-carrying phase may be presented with the variation of the driving field λ for the magnetic field h>1; and the ground-state entanglement arises simultaneously at the critical point of quantum phase transition. In our model, the introduction of magnetization current may result in more entanglement between any two nearest-neighbour spins.     

Stable 85Rb micro vapour cells: fabrication based on anodic bonding and application in chip-scale atomic clocks

We describe the microfabrication of ⁸⁵Rb vapour cells using a glass-silicon anodic bonding technique and in situ chemical reaction between rubidium chloride and barium azide to produce Rb. Under controlled conditions, the pure metallic Rb drops and buffer gases were obtained in the cells with a few mm³ internal volumes during the cell sealing process. At an ambient temperature of 90 ℃ the optical absorption resonance of ⁸⁵Rb D1 transition with proper broadening and the corresponding coherent population trapping (CPT) resonance, with a signal contrast of 1.5% and linewidth of about 1.7 kHz, have been detected. The sealing quality and the stability of the cells have also been demonstrated experimentally by using the helium leaking detection and the after-9-month optoelectronics measurement which shows a similar CPT signal as its original status. In addition, the physics package of chip-scale atomic clock (CSAC) based on the cell was realized. The measured frequency stability of the physics package can reach to 2.1×10^-10 at one second when the cell was heated to 100 ℃ which proved that the cell has the quality to be used in portable and battery-operated devices.     

Accurate ab initio study of low-lying electronic states of phosphorus nitride radical

This paper employs the highly accurate valence internally contracted multireference configuration interaction method to investigate the potential energy curves (PECs) for the ground state (X¹Σ⁺) and two low-lying excited states (A¹Π and D¹Δ of phosphorus nitride (PN) radical with the correlation-consistent basis set, aug-cc-pV6Z, in the valence range. Relativistic effects are considered in these calculations. The spectroscopic constants of the X¹Σ⁺ and A¹Π states are calculated based on the PECs, and the results are in good accord with the available experimental data. The first 30 vibrational states for the A¹Π state and the first 40 vibrational states for the A¹Π state are determined when J=0. For each vibrational state, molecular constants G(υ), B(υ) and D(υ) are also attained.     

Magnetostriction of Fe81Ga19 oriented crystals

The effect of the orientation on the magnetostriction in Fe₈₁Ga₁₉ alloy has been investigated experimentally and theoretically. The Fe₈₁Ga₁₉ [001] and [110] oriented crystals were prepared and the magnetostriction was measured under different pre-stress. The saturation magnetostriction of the [001] oriented crystal increases from 170×10^-6 to 330×10^-6 under the pre-stress from 0 to 50 MPa. The [110] oriented crystal has a saturation magnetostriction from 20×10^-6 to 140×10^-6 with the compressive pre-stress from 0 to 40 MPa. The magnetostriction of [001] and [110] oriented crystals has been simulated based on the phenomenological theory. The domain rotation path has been determined and the resultant magnetostriction calculated under different pre-stress. The experimental and simulated results both show that the [001] oriented crystal exhibits better magnetostriction than [110] oriented crystal. The enhancement of the saturation magnetostriction by the compressive pre-stress in the [110] oriented crystal is higher than that in the [001] oriented crystal.     

西湖凹陷油气成藏的主控因素

西湖凹陷位于东海大陆架边缘,地壳为相对软弱的过渡壳。西湖凹陷中新世末以前属于萎缩型盆地,上新世伴随冲绳海槽的形成才成为扩张性盆地。受构造控制盆地萎缩期沉积有以下3个特点：第一,整体表现为海退;第二,沉积范围逐次减小;第三,泥岩百分比越来越低,盖层条件越来越差。平湖组存在区域盖层,钻遇断块气藏;花港组存在局部盖层,背斜充满度高,断背斜充满度低,断块未成藏;新近系盖层条件更差,断背斜亦未能成藏。由此可见保存条件是西湖凹陷油气成藏的主控因素,保存条件好的领域是西湖凹陷下一步勘探的方向。     

西湖凹陷中南部油气成藏动力学特征及成藏机理

西湖凹陷以始新世末的玉泉运动和中新世末的龙井运动形成的不整合面为界,将盆地的发展演化分为裂陷、坳陷和区域沉降三个阶段。在盆地演化的不同阶段,不同构造带的沉降速率存在差异,烃源岩的热成熟演化史也不一致。生、排烃史模拟表明：平湖组烃源岩的生烃强度最高,花港组烃源岩的生烃强度相对较小;中央背斜带及其两侧深凹部位烃源岩的生烃强度大于保斜坡带;主要应用Basin Mod盆地模拟软件系统,通过对流体势、温压系统、异常压力的分析,探讨西湖凹陷中南部油气运聚成藏的机理。     

Paleoenvironmental implications of the guano phosphatic cementation on Dongdao Island in the South China Sea

The phosphatic cement in the bioclastic sediment sequence on the northeastern shore of Dongdao Island in the South China Sea was studied and its paleoenvironmental implications discussed. Petrological characteristics and major, trace, REE element data unequivocally supported the notion that phosphatization was closely associated with avian guano decomposition and leaching, whereas carbon and oxygen isotope results further revealed that meteoric water were involved in these processes. AMS ¹⁴C dates on the brown phosphate cements indicate that they were formed around 5700, 5000–5100 and 2900 yr BP, respectively. The multi-episodes of phosphatization very likely correspond to intermittent seabird occupation on this island — possibly reflecting Holocene sea-level oscillation and/or long term climate changes in the South China Sea that have controlled seabird habitat. The phosphate cementation, which occurs widely in tropical islands, may be another useful monitor for sea-level and/or paleoclimate changes.     

Analysis of second-order resonance in wave interactions with floating bodies through a finite-element method

A time-domain method is employed to analyse the resonant oscillations of the liquid confined within the two floating bodies. The velocity potentials at each time step are obtained through a finite-element method (FEM) with quadratic shape functions. The matrix equation of the FEM is solved through an iteration. The radiation condition is satisfied through a combination of the damping zone method and the Sommerfeld–Orlanski equation. A detailed analysis is made for two rectangular floating cylinders undergoing forced oscillation. The first-order potential reveals the resonant behaviour of the wave motion at certain frequencies ω_i, which is similar to sloshing in a tank. More interestingly, the second-order theory further reveals that when the oscillation frequency is at ω_i/2 or half of the resonant frequency, no first-order resonance is observed as expected, but the second-order resonant motion becomes evident, which does not seem to have been extensively investigated so far. Detailed results for two rectangular cylinders are provided to show some insights into the resonant effect due to the interaction between the bodies. The first- and second-order resonant phenomena have been observed and the result has shown that the second-order components have significant influence on the wave and force in some cases, especially at the second-order resonance.     

Formation of saddle dolomites in Upper Cambrian carbonates, western Tarim Basin (northwest China): Implications for fault-related fluid flow

The saddle dolomites occur more intensely in cores closely to fault than that in cores far away from the fault in Upper Cambrian carbonate of western Tarim basin, suggesting that formation of the saddle dolomites is likely related to fault-controlled fluid flow. They partially fill in fractures and vugs of replacement dolomite. The saddle dolomites exhibit complex internal textures, commonly consisting of core and cortex. In comparison with the matrix dolomites, the saddle dolomites show lower Sr-content and ⁸⁷Sr/⁸⁶Sr ratios, higher Fe- and Mn-content, and more negative δ¹⁸O values. Combined with high Th (100–130 °C) of primary fluid inclusions, it is suggested that the saddle dolomites precipitated from hydrothermal fluid derived from the deep evaporite-bearing Middle Cambrian strata, and the magnesium source may be due to dissolution of host dolomite during hydrothermal fluid migration. Fault activity resulted in petrographic and geochemical difference of the core and cortex of the saddle dolomites. The cores precipitated from the formation water mixed by deep brines at the early stage of fault activity, and the cortexes precipitated from the deep fluid with higher temperatures through the Middle Cambrian later. In summary, the formation of the saddle dolomites implies a hydrothermal fluid event related to fault activity, which also resulted in high porosity in Upper Cambrian carbonate in western Tarim Basin.