TiO_2掺杂量对PTFE/SiO_2复合材料性能的影响

采用新型化学工艺,制备了SiO2与TiO2共同填充的PTFE复合材料,系统研究了TiO2掺杂量对所制复合材料显微结构、微波介电性能和热膨胀系数的影响。结果表明,复合材料的密度、介电常数和热膨胀系数都随着掺杂量的增大而增加,吸水率随着掺杂量的增大而减小,介电损耗随着掺杂量的增大先减小后增大。当TiO2掺杂量为质量分数7%时,PTFE很好地包覆在SiO2表面,复合材料结构致密,具有与铜箔较为匹配的线膨胀系数(17.76×10–6/℃),且介电性能优良(εr=2.94,tanδ=0.000 82)。     

Pre-breakdown in thin SiO2 films

The on-off fluctuations of the tunnel current in 5.6 nm SiO₂ films before dielectric breakdown are analyzed in detail. For this purpose, a low noise measurement system has been realized which allows detection of pre-breakdown phenomena and interruption of the stress before catastrophic failure occurs. A spectral analysis of these fluctuations is presented along with preliminary results of the experiments made possible, for the first time, by the new measurement system     

TiO2/SiO2多层膜系一维光子晶体缺陷态特性研究

建立了一种基于TiO2/SiO2多层膜系并含缺陷层的一维光子晶体模型。基于时域有限差分(FDTD)算法,对其基本层周期数,缺陷层位置、光学厚度以及不同材料等情况下的带隙特性在理论上进行了系统的模拟与分析,发现这种一维光子晶体的缺陷态的透过率和带隙宽度受基本层周期数、缺陷层所在位置和材料的影响较大,而缺陷态中心波长位置仅由缺陷层的光学厚度决定。     

Photo-CVD process for ultra thin SiO2 films

In this paper we first report the use of very low deposition rate photo-induced chemical vapor deposition process, (below 0.05 nm/min). This photo-CVD process is adequate to grow very thin and ultra thin layers of SiO₂. Details on the design of the reaction chamber, reactive gases and process parameters to obtain the desired deposition regime are presented. Dependence of deposition rate on pressure in the chamber and gas flow ratio is discussed. Deposited layers were characterized using I–V and C–V techniques.     

Contact potential measurements on thin SiO2 films

Contact potential measurements by the Kelvin method were performed in vacuum on silicon wafers whose thermal oxide film was etched into the shape of a wedge. A given position along the oxide corresponded directly to a given depth and by scanning a reference electrode stripe across the wafer, information about the distribution of the oxide charge through the thickness was obtained. It was found that the oxide charge was positive and concentrated within a few hundred angstroms of the SiSiO₂ interface.     

Spin synthesis of monolayer of SiO2 thin films

The highly ordered monolayer of submicron size silica (SiO₂) particles (235 nm) is developed on p-silicon by using three-step spin-coating in colloidal suspension, which has significant potential in various applications. The influence of three-step spin speeds, spinning time, acceleration time between different steps, concentration of SiO₂ particles in the solution, solution quantity, and the ambient humidity (relative humidity) on the properties of monolayer SiO₂ are studied in order to achieve a large area monolayer film. A relatively high surface coverage and uniform monolayer film of SiO₂ particles in the range of 85%-90% are achieved by appropriate control of the preparative parameters. We conclude that this method can be useful in industrial applications, because of the fabrication speed, surface coverage and cost of the process.     

SiO2薄膜光学常数物理模型

SiO2薄膜是光学薄膜领域内常用的重要低折射率材料之一。在文中研究中,通过测量薄膜的椭偏参数,使用非线性最小二乘法反演计算获得薄膜的光学常数。采用离子束溅射和电子束蒸发两种方法制备了SiO2薄膜,在拟合过程中,基于L8（22）正交表设计了8组反演计算实验,以评价函数MSE为考核指标。实验结果表明:对IBS SiO2薄膜拟合MSE函数影响最大的为界面层模型,对EB SiO2薄膜拟合MSE函数影响最大的为Pore模型。同时确定了不同物理模型对拟合MSE函数的影响大小和反演计算过程模型选择的次序,按照确定的模型选择次序拟合,两种薄膜反演计算的MSE函数相对初始MSE可下降35%和38%,表明拟合过程模型选择合理物理意义明确。文中提供了一种判断薄膜物理模型中各因素对于薄膜光学常数分析作用大小的途径,对于薄膜光学常数分析具有指导意义。     

Structural properties of V2O5 thin films prepared by vacuum evaporation

Vanadium pentoxide (V₂O₅) films were deposited on glass substrates by vacuum evaporation technique at various deposition temperatures (T_s) viz., 300, 473, 573, 623 and 673 K. The structural and microstructural properties of the films are analyzed using XRD and Raman scattering measurements. X-ray characterization revealed the films deposited at T_s473 K are amorphous and the film deposited at T_s573 K are polycrystalline with orthorhombic symmetry. The corrected lattice constant values are determined from Nelson-Riely plots. The lattice constants “a” and “c” are found to decrease with increase in the deposition temperature, which may be attributed to the increase in non-stoichiometry. Change in the preferred orientation is observed for films deposited at substrate temperatures 623 K which is likely to be governed by the recrystallization process. Various structural parameters such as lattice constants, grain size, and microstrain and dislocation density are determined and the influence of deposition temperature on the structural parameters are discussed.     

CVD TiN layers as diffusion barrier films on porous SiO2 aerogel

In this work the compatibility of MOCVD TiN barrier films on porous SiO₂ aerogel as low-k dielectric was investigated. The continuity, roughness, and sheet resistance, R_s, of the barrier as well as the electrical properties of the aerogel were investigated. A continuous TiN barrier on uncapped and PECVD SiN capped aerogel exists at 30 and ≤20 nm, respectively. The high surface roughness of the TiN is caused by the aerogel layer. TiN penetration into uncapped aerogel was detected in the interface region, whereas capped low-k material shows no interaction with the barrier film.     

非晶态SiO2过渡层对生长C轴取向LiNbO3薄膜的影响

采用磁控溅射方法,在Si衬底和LiNbO3薄膜之间引入SiO2过渡层制备LiNbO3薄膜。采用X射线衍射（XRD〉、傅里叶变换红外吸收光谱（FT-IR）和扫描电子显微镜（SEM）对LiNbO3薄膜的结晶取向、组成成分和表面形貌进行了表征,重点研究了非晶态SiO2过渡层对LiNbO3薄膜C轴取向的影响。结果表明,非晶态S...     

不同沉积方式SiO2薄膜的自然时效特性

SiO2薄膜是光学薄膜领域内常用的重要低折射率材料之一。文中采用不同沉积技术在Si基底上制备了SiO2薄膜,并研究了它们光学特性的自然时效特性。采用不同贮存时间的椭偏光谱表征SiO2薄膜的光学特性,随着时间的增加,EB-SiO2薄膜和IAD-SiO2薄膜的物理厚度和光学厚度随着增加,但IBS-SiO2薄膜随着减小,变化率分别为1.0%,2.3%和-0.2%。当贮存时间达到120天时,IBS-SiO2薄膜、EB-SiO2薄膜和IAD-SiO2薄膜的物理厚度和光学厚度趋于稳定。实验结果表明,IBS-SiO2薄膜的光学特性稳定性最好,在最外层保护薄膜选择中,应尽可能选择离子束溅射技术沉积SiO2薄膜。     

Influence of substrate temperature on the properties of fluorinated silicon-nitride thin films deposited by IC-RPECVD

Fluorinated silicon-nitride films have been prepared from an Ar/SiF₄/NH₃ gas mixture by inductively coupled remote plasma-enhanced chemical vapor deposition (IC-RPECVD) at different substrate temperatures, ranging from 150 to 300°C. All of the resulting deposited silicon-nitride films were free of Si-H bonds, showed high dielectric breakdown fields (≥8 MV cm^?1), and had root mean square (rms) surface roughness values below 3 Å. The films’ refractive indices and the contents of O and F remain constant, but Si/N ratios drop from 5 to 2 and N-H bond concentrations decrease in the range (1.3–0.9) × 10²² cm^?3 as the substrate temperature increases. The density of interface states (D_it) with c-Si was reduced from 2.4 × 10¹² to 8 × 10¹¹ eV^?1 cm^?2 at substrate temperatures ≥250°C.     

基于ZnS/SiO2量子点的EL器件及宽谱发射

将ZnS/SiO2量子点与PVP在甲醇溶液中充分混合作为活性层材料,通过匀胶方法制备了ITO//ZnS/SiO2∶PVP//Al结构的电致发光(EL)薄膜器件。器件的EL光谱由510～560nm波段的绿光发射和相对较弱的蓝紫光(400nm左右)发射组成,通过对发光光谱的分析发现,上述两个区域的发射均来自ZnS的缺陷能级。其中,绿色发光峰来源于较低能态的缺陷能级;而高能区域的蓝色发光则是由于高能态的缺陷能级俘获电子的几率增大,在这过程中,PVP形成的能级阶梯有效增加了高能态缺陷能级俘获电子的几率,提升了高能波段的发光效率,相应地,器件的色坐标也随之从(0.37,0.42)变化到(0.30,0.34),趋于白光发射。     

无定型SiO2对纳米ZnO缺陷发光的辅助增强效应研究

利用正硅酸乙酯水解后的无定型SiO2网络结构,合成了不同尺度的纳米ZnO。X射线衍射(XRD)谱显示,当正硅酸乙酯的量从0ml增加到5ml,ZnO的粒径从14.6nm减小到1.9nm;光致发光(PL)光谱显示,发射峰位从560nm蓝移到510nm,发射强度明显增强。利用紫外-可见(UV-VIS)吸收光谱、PL光谱以及能级结构分析,我们认为,纳米ZnO随尺度下降所产生的发光增强来源于无定形SiO2所抑制的ZnO表面非辐射跃迁过程以及二者之间的再吸收过程;此外,纳米ZnO尺度的下降,使得其表面的光生电子和晶格内部的O空位(Vo)之间的距离减小,提高了辐射跃迁的几率也是获得高荧光效率的可能原因。     

Low-temperature deposition of SiO2 films using plasma-enhanced oxygen with reduction of oxygen-originated damage

Plasma-enhanced chemical vapor deposition of SiO₂ with well-suppressed subcutaneous oxidation is demonstrated to be a promising technology for eliminating defect generation and fabricating thin gate SiO₂ films by means of a totally low-temperature process. An anomalous increase in electron density was observed in Si substrates irradiated by plasma-activated oxygen during the formation of gate SiO₂ films using an ultrahigh-vacuum system. The origin of this phenomenon was related to the donors generated by a high-energy species of oxygen radicals. For a deposition process, ionized oxygen may be effective but the radicals may cause plasma-enhanced oxidation with defect generation.     

Evaluation of trap creation and charging in thin SiO2 using both SCM and C-AFM

Conductive atomic force microscopy (C-AFM) and scanning capacitance microscopy (SCM) are used in this work to characterize trap creation and charge trapping in ultra-thin SiO₂. It is found that C-AFM working at normal operational voltages causes severe damage and subsequent negative charge trapping in the oxide. Permanent hillocks are seen in the topography of stressed regions. The height of these features is determined rather by the applied voltage than the electric field. Electrostatic repulsion between tip and sample and Si epitaxy underneath the oxide are the two most probable causes of this feature. The immediate physical damage caused in the oxide during high field C-AFM measurements is a possible showstopper for use of the C-AFM to investigate differences in pristine interface states. SCM operates at lower voltages, yielding less oxide damage and is able to indicate the interface state density variations through hysteresis in the dC/dV vs. V curves.     

基于PECVD的SiO2薄膜制备研究进展

二氧化硅(SiO₂)薄膜因其卓越的光学性能,在半导体器件、集成电路、光学涂层等领域具有巨大的应用潜力。然而,SiO₂薄膜制备过程中面临表面粗糙度、杂质控制和致密性等问题。为解决这些问题,研究者们通过工艺改进和表面修饰等手段来提高SiO₂薄膜的性能。在众多SiO₂薄膜制备技术中,等离子体增强化学气相沉积(Plasma-Enhanced Chemical Vapor Deposition, PECVD)技术由于沉积SiO₂薄膜所需温度低、原位生长等优势,成为制备SiO₂薄膜最常用的方法。综述了用PECVD技术制备SiO₂薄膜的发展历程,并探讨了关键工艺参数和后处理工艺对薄膜质量的影响。对PECVD技术的深入研究,有助于实现对SiO₂薄膜生长的更精准控制,进一步拓展其广泛的应用前景。     

Effect of PECVD of SiO2 passivation layers on GaN and InGaP

Thin (200 ) layers of SiO₂ were deposited by plasma enhanced chemical vapor deposition onto GaN and InGaP patterned with transmission line measurement contact pads. The sheet resistance of n-GaN and n- and p-InGaP was measured as a function of N₂O/SiH₄ ratio, rf chuck power, pressure and substrate temperature during the SiO₂ deposition. The sheet resistance ratio before and after the deposition varied from 0.7 to 1.2, reflecting a competition between mechanisms that decrease doping (hydrogen passivation, ion-induced deep traps) and those that increase it (creation of shallow donor states in n-type material through preferential ion of the group V elements, gettering of hydrogen in p-type material). Under most conditions, SiO₂ deposition creates minimal changes to the electrical properties of GaN and InGaP.     

ZnO量子点／SiO2复合器件的可调控电致发光研究

在不同浓度的SiO2乙醇溶液中制备了一系列ZnO量子点／SiO2复合材料,通过匀胶方法将其制备成复合薄膜器件。器件的电致发光（EL）随着SiO2浓度的增加逐渐蓝移。通过实验,探索了发生蓝移的机制。选取一种ZnO量子点／SiO2复合材料均匀混入不同质量的纯SiO2后,测试结果表明,该蓝移现象不是SiO2自身发光引起的。通...