光电化学刻蚀n型多孔硅过程中的介质增强荧光效应

光电化学阳极刻蚀n型单晶硅过程中,在电解液中加入适量钛溶胶,制得多孔硅（PS）,经荧光光谱（PL）检测,发光强度明显增强;傅里叶红外光谱（FT-IR）检测发现,在多孔硅结构中出现了亚甲基的伸缩振动吸收;用扫描电镜（SEM）和X射线光电子能谱（XPS）表征手段对其进行表征,发现表面的裂缝区域明显加大。在Fe（CN）63＋/Fe（CN）64-溶液中的测量了复合电极的光电流-电压关系,结果显示,用添加钛凝胶制备的多孔硅电极具有更好的光电流特性。     

浸泡后多孔硅的结构及光致发光特性

用电化学腐蚀方法制备了多孔硅样品,在浸泡液中浸泡使其表层多孔层与样品分离,在样品表面形成了丰富的SiO2包裹纳米硅颗粒结构,研究了样品的光致发光(PL)特性.结果表明,与剥离前相比,表层多孔层剥离后PL谱的强度约有10倍的增幅,峰位主要在蓝紫光范围内.在300℃干氧中退火后,样品的发光强度下降为退火前的三分之一,随着退火温度的升高,发光强度有所增强.退火前后有不同的发光机理,退火前光激发主要在纳米硅内,然后在二氧化硅层中的发光中心辐射复合;退火后光激发和光辐射都发生在二氧化硅层中.     

一种氮氧化物气体传感器元件的制备方法

申请（专利）号：201210400849.9公开（公告）日：2013．03．27申请（专利权）人：天津大学 摘要：本发明公开了一种氮氧化物气体传感器元件的制备方法,步骤为：（1）对n型单面抛光的单晶硅片进行清洗;（2）采用双槽电化学腐蚀法在硅片的抛光表面制备孔径尺寸在50～200nm的硅基孔洞有序多孔硅,腐蚀液为6％一8％的氢氟酸水溶液,施加的腐蚀电流密度为115～135mA／cm2,腐蚀时间为5—25min;（3）再将多孔硅置于超高真空对靶磁控溅射设备的真空室,制备基于硅基孔洞有序多孔硅的氮氧化物气体传感器元件。本发明的制备方法简单,灵活可调,工艺条件较少,易于控制;提供了一种可在室温及极低浓度（0．1×10-6）下具有高灵敏度、高选择性、快速响应／恢复特性、重复性好的氮氧化物气体传感器元件。     

多孔硅与聚甲基丙烯酸甲酯复合光致发光特性研究

多孔硅与有机材料复合可以改善多孔硅的光致发光特性。用化学腐蚀的方法制备了多孔硅，通过不同方法实现了多孔硅与聚甲基丙烯酸甲酯(PMMA)的复合。实验结果表明，用旋涂法实现的PMMA固化后再与多孔硅复合而制得的样品的结果最好，它与原始的多孔硅样品相比，发光峰发生了蓝移而且发光强度下降很小。PMMA层有限的厚度和PMMA对多孔硅表面的保护使复合后发光强度下降很小。制备的多孔／PMMA复合体系的发光强度几乎不随时间而下降，这可能是由于PMMA有效地隔绝多孔硅与空气的接触，保护了多孔硅的表面，不会产生更多的悬挂键。     

多孔硅的微结构及其冷阴极的电子发射特性研究

采用电化学腐蚀法在n型单晶Si基底上制备多孔硅(PS)膜,利用场发射扫描电子显微镜(FE-SEM)分析其微结构特征,研究了硅基底材料、腐蚀电流密度和腐蚀时间等制备条件和工艺参数对PS微结构的影响。实验结果表明,轻掺杂n型Si基底上形成的PS膜(n--PS)中的孔较深且孔径较大,而重掺杂n型Si基底上的PS膜(n+-PS)中的孔分布较为密集,而且呈多分枝结构;腐蚀电流密度相同时,PS的膜厚和腐蚀时间成正比,而在较高的腐蚀电流密度下制备得到的PS膜在结构上更为疏松。制作了基于n+型硅基底的PS阴极,此阴极的阈值电压约为14 V,高于该电压后发射电流随着二极管电压提高而呈指数性增加趋势,而且发射电流对环境气压不敏感,即使在0.1 Pa的低真空中也没有明显的衰减。     

纳米硅量子线的发光特性研究

利用脉冲激光蒸发或高温物理升华的方法,制备出纯度极高、直径分布均匀(13nm左右)的硅的一维量子线.光致发光(PL)测量显示,在313.5nm激光激发下,室温下硅量子线具有红绿蓝三色发光.对硅量子线进行氧化处理后,随氧化时间的增加,红光PL峰发生蓝移,而绿、蓝峰没有移动.红光PL与量子尺寸限制效应有关,而绿、蓝光PL来源于表层氧化硅中的缺陷发光.     

多孔硅后处理研究进展

多孔硅（PS）后处理是一项能提高多孔硅发光效率和使用寿命的前沿技术。目前多孔硅后处理的方法很多，综述了各种后处理方法对PS发光的影响，并对其发展前景做了展望。     

纳晶硅氧化层中的陷阱态(英文)

由Si-H键钝化的多孔硅的光致荧光(PL)发光频移遵循量子受限效应,随着纳米结构尺寸的变小PL发光频率从红外蓝移到紫外。多孔硅被氧化后,PL发光带的中心波长被钉扎在700nm~750nm范围,且强度明显增加。计算表明,氧化后的Si=O键或Si—O—Si键能在展宽的导带下方形成电子陷阱态。由此提出量子受限与氧化陷阱态模型可以很好地解释PL发光的钉扎和增强效应。该模型中的电子陷阱态扮演了重要的角色。     

硝酸银水溶液处理新生多孔硅的研究

n型单晶硅经光电化学阳极刻蚀成多孔硅.研究了多孔硅经硝酸银(AgNO3)水溶液浸泡前后样品的光致发光(PL)性质,实验发现,浸泡很短时间内多孔硅发光强度增强,浸泡时间较长的样品发光强度会衰减直至猝灭,且浸泡液浓度越大荧光衰减越明显.通过扫描电子显微镜(SEM),傅立叶红外光谱(FTIR)和X射线光电子能谱(XPS)的检测显示,AgNO3水溶液浸泡的多孔硅样品表面有金属银析出.光致发光增强是多孔硅表面形成Si-O结构所致,荧光猝灭是因为银在多孔硅表面形成大量非辐射复合中心.     

铈掺杂多孔硅的形貌和光致发光研究

采用电化学方法在多孔硅中掺杂了稀土铈(Ce)元素.利用原子力显微镜表征了多孔硅和Ce掺杂多孔硅的表面形貌,采用荧光分光计对样品的光致发光(PL)特性进行了研究.多孔硅样品在480nm波长激发下PL谱上观察到两个发光峰,分别位于572和650nm;通过光致发光激发谱测量,得到位于572、650nm的发光峰对应的最佳激发波长分别为380和477nm.Ce掺杂多孔硅样品在480nm波长激发下,PL谱上只显示出多孔硅原有的发光增强;而在380nm波长激发下的PL谱上不仅显示多孔硅原有的发光增强,而且还出现了新的发光峰位于517nm.认为这分别是Ce3 与nc-Si发生了能量传递和Ce掺杂引入了新的发光中心所造成的.     

Optical and microstructural investigations of porous silicon

Raman scattering and photoluminescence (PL) measurements on (100) oriented n-type crystalline silicon (c-Si) and porous silicon (PS) samples were carried out. PS samples were prepared by anodic etching of c-Si under the illumination of light for different etching times of 30, 60 and 90 min. Raman scattering from the optical phonon in PS showed the redshift of the phonon frequency, broadening and increased asymmetry of the Raman mode on increasing the etching time. Using the phonon confinement model, the average diameter of Si nanocrystallites has been estimated as 2.9, 2.6 and 2.3 nm for 30, 60 and 90 min samples, respectively. Similar size of Si crystallites has been confirmed from the high resolution transmission electron microscopy (HRTEM). Using 2TO phonon mode intensity, we conjectured that the disordered Si region around the pores present in 30 min PS dissolved on etching for 90 min. The photoluminescence (PL) from PS increased in intensity and blue shifted with etching time from 2.1–2.3 eV. Blue shifting of PL is consistent with quantum confinement of electron in Si nanocrystallites and their sizes are estimated as 2.4, 2.3 and 2.1 nm for 30, 60 and 90 min PS, respectively which are smaller than the Raman estimated sizes due to temperature effect. Unambiguous dominance of quantum confinement effect is reported in these PS samples.     

Step voltage with periodic hold-up etching: A novel porous silicon formation

A novel etching method for preparing light-emitting porous silicon (PS) is developed. A gradient steps (staircase) voltage is applied and hold-up for different periods of time between p-type silicon wafers and a graphite electrode in HF based solutions periodically. The single applied staircase voltage (0–30 V) is ramped in equal steps of 0.5 V for 6 s, and hold at 30 V for 30 s at a current of 6 mA. The current during hold-up time (0 V) was less than 10 μA. The room temperature photoluminescence (PL) behavior of the PS samples as a function of etching parameters has been investigated. The intensity of PL peak is initially increased and blue shifted on increasing etching time, but decreased after prolonged time. These are correlated with the study of changes in surface morphology using atomic force microscope (AFM), porosity and electrical conductance measurements. The time of holding-up the applied voltage during the formation process is found to highly affect the PS properties. On increasing the holding-up time, the intensity of PL peak is increased and blue shifted. The contribution of holding-up the applied steps during the formation process of PS is seen to be more or less similar to the post chemical etching process. It is demonstrated that this method can yield a porous silicon layer with stronger photoluminescence intensity and blue shifted than the porous silicon layer prepared by DC etching.     

硅基MEMS三维微电极阵列的超电容特性

三维微电极是一种具有空间结构优势、电化学性能比二维微电极更加优越的微型储能结构.本文提出一种基于光刻、感应耦合等离子体刻蚀和溅射等MEMS工艺加工三维结构硅基微电极阵列的新方法.采用电化学阴极沉积工艺在微电极表面制备了纳米氧化钌功能薄膜.借助扫描电子显微镜、循环伏安测试和电化学交流阻抗谱测试等手段对三维微电极的表面形貌和电化学性能进行了表征,系统研究了阴极沉积电流密度、电沉积时间以及硅基微结构表面"微草效应"对三维微电极超电容特性的影响.所制备三维微电极的比电容达到1.57 F/cm2,与平面电极比电容0.42 F/cm2相比明显提高,而电化学阻抗比二维平面微电极显著降低.相关实验数据表明基于MEMS技术加工的三维结构微电极具有优于平面电极的电化学电容储能特性.     

退火对多孔氧化铝膜光致发光的影响

用电化学阳极氧化方法在草酸溶液中制备了有序多孔氧化铝膜,研究了退火对其光致发光强度和峰位的影响,研究结果表明,多孔氧化铝膜光致发光强度随着退火温度的升高而增强,当退火温度为500℃时强度最大,随后进一步升高退火温度则强度又明显下降。同时,发光谱的峰位随着退火温度升高呈现蓝移规律,bk2．83eV蓝移到2．89eV。氧化铝膜中存在两种不同的发光中心F＋（单离子氧空位）和F心（俘获两个电子的氧空位）,用退火对两种氧空位浓度的影响解释了退火对光致发光的影响。     

微型FAIMS生化传感器的设计与制作

根据高场非对称波形离子迁移谱（high-field asymmetric waveform ion mobility spectrometry,FAIMS）原理,设计了一种微型生化传感器.采用真空紫外灯离子源在大气压环境下对样品进行电离,紫外灯发射的光子能量为10.6 eV,波长116.5 nm.迁移区由上下两块紫铜金属平板电极构成,尺寸为10 mm×10 mm×1 mm.完成了高场非对称方波电源的设计,所输出的射频电压最大值为1 180 V,最小值为-480 V,频率189 kHz,占空比30%.以丙酮为实验样品,通过高场非对称波形离子迁移谱-质谱联用技术进行传感器的性能验证实验,实验结果表明所设计的基于FAIMS原理的生化传感器可以实现离子分离和过滤功能.基于SIMION软件对FAIMS生化传感器进行仿真分析,仿真与实验结果相符.最后利用硅片双面感应耦合等离子体（inductively coupled plasma,ICP）刻蚀和硅-玻璃键合工艺,加工出基于微机电系统（micro electro mechanical system,MEMS）技术的微型FAIMS传感器芯片.采用频率2 MHz、最大电压364 V、占空比30%的高场非对称方波电压进行FAIMS芯片实验.载气流速80 L/h,补偿电压从-10 V～3 V以0.1 V的步长扫描,得到了丙酮的FAIMS谱图,验证了芯片的性能.     

Low mechanical pressure during electrochemical etching: induced modification in optical and structural properties of n-type porous silicon

In this study, n-type porous silicon (PS) layers are formed in the dark with the assistance of a low mechanical pressure during electrochemical etching process. Pressure-induced stress/strain modifies the resistivity of the silicon substrate to enhance the etching process. Under the same equivalent etching condition, pressure-assisted etching can yield PS layer with stronger room temperature photoluminescence intensity than the layer formed by ordinary electrochemical etching. The porosity of pressure-assisted etched PS layers is found to be much higher than that of ordinary etched layer. Fourier transformation infrared absorption spectroscopy and grazing incidence X-ray diffraction measurements and analysis show that application of the pressure during electrochemical etching promotes the degree of oxidation and reduces the crystallites size of the PS layer. The effect of the pressure during etching process on the surface topography of PS is revealed by scanning electron microscopy imaging.     

Effect of etch-treatment upon the intensity and peak position of photoluminescence spectra for anodic alumina films with ordered nanopore array

Porous anodic alumina membranes (AAMs) were prepared in oxalic acid and then carried on an etch-treatment in phosphoric acid. Using the etch-treatment the photoluminescence (PL) intensity of AAMs increases by a factor of 1/3. The effect of etch-treatment upon the intensity and peak position of photoluminescence (PL) spectra was investigated. It was found that the intensity of the photoluminescence (PL) spectra increased with the etching time increasing. A PL spectrum can be divided into two subbands with the peak at 434 and 460 nm, respectively. As the etching time prolongs, the intensity of the peak of 434 nm subband increases and that of the 460 nm subband rises firstly and then decreases. It can be explained by that two luminescence centers (F and F⁺ centers) coexist in AAMs. F centers are concentrated in the surface layer and F⁺ centers are enriched in the depth of pore wall. The increment of the PL intensity comes from the contribution of F⁺ photoluminescence centers concentrated in the depth of pore wall in AAMs. This work will be beneficial to improving the photoluminescence intensity and understanding the light-emitting mechanisms for related materials.     

铝在硫酸银溶液中的脉冲电解着色工艺

目前,脉冲电源在铝合金微弧氧化方面应用较广,而在传统氧化着色领域应用较少。采用数控脉冲电源在硫酸银溶液中对铝进行电解着色,探讨了脉冲电解着色工艺参数对着色速度和膜层颜色的影响。结果表明:在着色溶液浓度和着色时间不变的条件下,脉冲电解着色工艺参数为工作频率50 Hz,总占空比30%,正占空比30%,反占空比70%,正向电压13 V,反向电压14 V时,膜层颜色与白色相比具有最大的色差值,着色速率最大。     

Correlation of electrical conductivity and photoluminescence in nanoporous silicon

The effective electrical conductivity of p type porous silicon is determined both theoretically and experimentally for different porosities ranging from 30% to 80%. In this work, Effective Medium Approximation (EMA) model was used as a theoretical support. The porous silicon samples were prepared by the electrochemical etching method for different values of the anodic current. The porous material is assumed to be formed of three phases; vacuum, oxide and Si nanocrystallites. The analytical expression of the electrical conductivity of the Si nanocrystallites was established using the quantum confinement theory. This enables us to correlate the electrical conductivity of a PS layer, to the peak energy of its photoluminescence (PL) spectrum. A perfect agreement between the theoretical and the experimental electrical conductivity values was obtained for all prospected PS porosities. The results are discussed as regard to other works.