Modified Photoluminescence by Silicon-Based One-Dimensional Photonic Crystal Microcavities

photoluminescence (PL) lrom one-dimensional photonic band structures is investigated. The doped photonic crystal with microcavitles are fabricated by using alternating hydrogenated amorphous silicon nitride (a-SiNx:H/a-SiNy:H) layers in a plasma enhanced chemical vapour deposition (PECVD) chamber. It is observed that microcavities strongly modify the PL spectra from active hydrogenated amorphous silicon nitride (a-SiNx:H) thin film. By comparison, the wide emission band width 208nm is strongly narrowed to 11 nm, and the resonant enhancement of the peak PL intensity is about two orders of magnitude with respect to the emission of the λ/2-thick layer of a-SiNx:H. A linewidth of Δλ=11 nm and a quality factor of Q=69 are achieved in our one-dimensional a-SiNz photonic crystal microcavities. Measurements of transmittance spectra of the as-grown samples show that the transmittance resonant peak of a cavity mode at 710nm is introduced into the band gap of one-dimensional photonic crystal distributed Bragg reflector (DBR), which further verifies the microcavity effects.     

Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiN_x matrix by the influence of near-interface oxide traps

Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method,followed by thermal annealing to form the Si nanocrystals(Si-NCs)embedded in Si Nx floating gate MOS structures.The capacitance–voltage(C–V),current–voltage(I–V),and admittance–voltage(G–V)measurements are used to investigate the charging characteristics.It is found that the maximum flat band voltage shift(△VFB)due to full charged holes(～6.2 V)is much larger than that due to full charged electrons(～1 V).The charging displacement current peaks of electrons and holes can be also observed by the I–V measurements,respectively.From the G–V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the Si O2/Si-substrate interface.Combining the results of C–V and G–V measurements,we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism.The evolution of G–V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.     

TRANSPORT PROPERTIES OF μc-Si:H FILMS PREPARED BY VERY HIGH HYDROGEN-DILUTED SILANE PLASMA

Highly hydrogen-diluted silane plasma is used to fabricate microcrystalline silicon films in a plasma-enhanced chemical vapour deposition system. X-ray diffraction and micro-Raman scattering spectroscopy are utilized to characterize their microstructure properties. Dark conductivity and drift mobility are measured by the travelling wave method. With the decreasing gas flow ratio of silane-to-hydrogen from 2% to 0.2%, the crystalline volume fraction and the drift mobility increase at room temperature. Meanwhile, the dark conductivity increases initially and then decreases. The relationship between the microstructures and transport properties is discussed.     

蓝青铜K0.3MoO3单晶Peierls相变研究

测量了蓝青铜K_0.3MoO₃单晶Ｒ-Ｔ曲线，发现曲线在２８０Ｋ左右有异常变化，计算得到１８０Ｋ以下的半导体能隙为１３２０Ｋ（０.１１ｅＶ）．液氮温度下测量了晶体的非线性导电性，得到电场阈值为０.1２９Ｖ／ｃｍ．样品ＤＳＣ研究表明，样品在２４０Ｋ处经历一新的Ｐｅｉｅｒｌｓ相变，且为一级相变，据此对相变的微观性质进行了定量计算．１８０Ｋ附近Δｃ_p-Ｔ曲线表明，１８０Ｋ处的相变为一个二级相变加一个一级相变 关键词：     

直拉法生长Y_3Al_5O_(12)(YAG)单晶体中的位错和包裹物

通过光双折射貌相法研究了YAG单晶体中位错、包裹物以及生长层间的关系,结果表明,包裹物优先吸附于固液界面上的位错露头点,而包裹物的大小与该处生长台阶的大小有关。     

铌酸钡钠和钽酸锂铁电相变的实地观察

本文报道了用透射电子显微镜实地观察铌酸钡钠和钽酸锂铁电相变的实验结果。在室温电畴的尺寸为0.2—1μm。当温度增加到接近居里点时,形成准规则排列的微畴结构,其尺寸为几百埃,实验结果用稍微修正了的模型进行了解释。在钽酸锂中当接近铁电相变温度时,发现了强烈的辐照损伤,这可能跟相变的软模有关。 关键词：     

熵与信息——麦克斯韦妖的启示

 在生物进化论的背后,存在两个带根本性的问题:一是生命的起源,即如何从无生命的物质变为有生命的物质,也可以说从无序到有序的问题;二是生物的遗传与变异,那就是从有序到有序的问题.对于第一个问题,目前科学家掌握的资料尚少,还没有得到明确的结论;而对于第二个问题,已经画出了一个基本的轮廓,这是20世纪自然科学的最重大成就之一.     

直拉法生长的LiNbO_3单晶体中的生长条纹和铁电畴组态间的对应关系

对应于旋转条纹和功率条纹,观测到晶体中铁电畴组态的相应变化,确定了旋转条纹与铁电畴组态间的一一对应关系,利用扫描电子显微镜中的X射线能谱分析测定了旋转条纹中的溶质浓度分布,得到了溶质浓度梯度决定了铁电畴组态的结论,自发极化与溶质浓度梯度间的耦合首次得到了实验证实。     

Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.     

界面稳定性与形态的演变

在生物学范围之外,人类所观察到的最为丰富多来的形态就要数相变过程中的产物.和复杂的生物形态的演变问题相比较,相变中对应的问题显然要简单得多,有可能作为理解这一具有普遍性问题的突破口.长期以来,晶莹对称的雪花赢得了人们的赞赏和惊奇.在中谷(U.Nakaya)的《雪晶》一书中[1],汇集了大量的雪花照片,琳琅满目,令人爱不释手.翻阅金属学家为钢铁生产实践需要所编纂的金相图谱[2],我们也为冶金和金属热处理过程之中所产生的千姿百态的显微组织所吸引,同时也体会到掌握这些形态演变的规律在生产实践中也是至关重要的.赏心悦目之余,探索这些…