Advances in applications of nanostructured silicon as a new multifunctional material

Abstract

The presented method of surface modification of single-crystal silicon by chemical etching makes it possible to obtain homogeneous nanostructured silicon layers with a thickness from 3 to 60?nm for application in micro- and nano-electronics as new multifunctional material. These results could be applied to the creation of sensitive photodetectors for visible and ultraviolet ranges. The method of scanning tunneling spectroscopy shows, that the changes in the thickness of nanostructured silicon layers affect the type of conductivity, and it opens new prospective for a practical application of nanostructured silicon in nano-electronics. The obtained current-voltage characteristics of nanostructured silicon layers showed different degrees of filling of the valence band, the conduction band and the appearance on the curve of the tunneling conductance of new peaks in the gas environment. The latter gives the possibility to use the method of scanning tunneling spectroscopy for a generation of gas and biosensors. The immune biosensor is proposed in the lab on a chip form based on the nanostructured silicon for the simultaneous analysis of numerous samples. The developed biosensor based on nanostructured silicon is very promising for use in so-called systems of lab-on-chip because it can be used for rapid analysis of various immune responses and is fully compatible with silicon planar technology used in the manufacturing of the semiconductor devices.     

Rate-determining process in chemical vapor deposition of SiC on off-axis -SiC

Homoepitaxial growth on off-axis α-SiC at reduced pressures in a horizontal cold-wall chemical vapor deposition (CVD) system operating at has been investigated. The growth rate was found inversely proportional to the square root of total pressure or the partial pressure of H₂, a carrier gas. A model to explain the experimental results is proposed, where the rate-determining process in CVD is competition between Si species and hydrogen atoms for C (carbon) dangling bonds at SiC step edges.     

CrO2 (1 0 0) and TiO2 (1 0 0) film heteroepitaxy on a BaF2 (1 1 1)/Si (1 0 0) substrate

Multi-domained heteroepitaxial rutile-phase TiO₂ (1 0 0)-oriented films were grown on Si (1 0 0) substrates by using a 30-nm-thick BaF₂ (1 1 1) buffer layer at the TiO₂–Si interface. The 50 nm TiO₂ films were grown by electron cyclotron resonance oxygen plasma-assisted electron beam evaporation of a titanium source, and the growth temperature was varied from 300 to 600 °C. At an optimal temperature of 500 °C, X-ray diffraction measurements show that rutile phase TiO₂ films are produced. Pole figure analysis indicates that the TiO₂ layer follows the symmetry of the BaF₂ surface mesh, and consists of six (1 0 0)-oriented domains separated by 30° in-plane rotations about the TiO₂ [1 0 0] axis. The in-plane alignment between the TiO₂ and BaF₂ films is oriented as [0 0 1] TiO₂ || BaF₂ or [0 0 1] TiO₂ || BaF₂ . Rocking curve and STM analyses suggest that the TiO₂ films are more finely grained than the BaF₂ film. STM imaging also reveals that the TiO₂ surface has morphological features consistent with the BaF₂ surface mesh symmetry. One of the optimally grown TiO₂ (1 0 0) films was used to template a CrO₂ (1 0 0) film which was grown via chemical vapor deposition. Point contact Andreev reflection measurements indicate that the CrO₂ film was approximately 70% spin polarized.     

Boron segregation control in silicon crystal ingots grown in Czochralski process

Boron-doped silicon single crystals of 207 mm diameter with various growing conditions are grown from a large amount of the melt in the cusp-magnetic Czochralski method, and the effects of growing parameters on dopant concentrations in the crystals are experimentally investigated. Equilibrium distribution coefficient of boron calculated by BPS model is 0.716. With the crystal rotation (ω) of 13 rpm and the crucible rotation of , the effective distribution coefficient (k_e) is 0.751 in zero magnetic strength and increases up to 0.78 in the magnetic strength of 640 G. For , there is no significant influence of ω on k_e. With , k_e is almost unity. The experimental results are compared with theory.     

硅薄膜矩形空芯波导太阳能电池光捕获性能的研究

为提高薄膜电池对光的捕获能力, 将平面硅薄膜电池制 作成矩形空芯波导结构,对其太阳光注入方式、光捕获能力和光-电转换效能进行了理论和 实验探讨。基于 多层膜反射理论和波导反射模型对波导电池光捕获效果的预测表明,波导电池能够将入射光 限制在空芯结 构内多次反射和吸收,具有较平面电池更高的光捕获能力。测定了不同平行光束在不同入射角度 下平面和波导 电池的光捕获功率和光-电转换效能的结果表明,波导电池对入射光功率近似全部捕获,其 光-电功率转换效能 较对应的平面电池有3～5倍的提升。对不同截面尺寸和长度的单结空芯波导电池光捕获率 进行了计算,提 出从电池膜层结构和空芯几何尺寸参数优化硅薄膜矩形空芯波导电池的思路,通过优化有 望实现用小于多结平面电池外形尺寸的单结空芯波导电池达到更好的光捕获效果。     

基于石墨烯-硅混合集成光波导的电光半加器

设计了一种由基于马赫-曾德尔干涉结构的石墨 烯-硅混合集成光开关级联而成的电光 半加器。通过施加电压调节石墨烯化学势,改变石墨烯在平面方向上的介电常数,引起模式 有效折射 率发生变化,控制光波在基于马赫-曾德尔干涉结构的石墨烯-硅混合集成光开关不同端口 输出,实现 半加器逻辑功能。仿真结果表明:当石墨烯化学势在0.50eV与0.64eV两种状态切换下,在1520nm到1600nm波长范围内,基于马赫-曾 德尔干涉结构的石墨烯-硅混合集 成光开关的最差串扰为－21.57 dB, 插入损耗小于0.109 dB。当数据传输速率为10Gbit/s时,基于石墨 烯-硅混合集成光波 导的电光半加器在1550nm工作波长下,器件的 消光比大于41.05dB。     

基于高阻硅的毫米波IPD 滤波器研究

5G 通信迫切需要毫米波集成无源器件(Integrated Passive Device,IPD),要求该类器件低成本、高性能。基于高阻硅(High Resistivity Silicon, HRS)工艺设计并加工了一款四阶交叉耦合毫米波微带滤波器,基于测试结果和有耗耦合矩阵理论反提取得到四阶滤波器谐振器的真实无载品质因素。进而对高阻硅基的毫米波工艺参数(例如,损耗角正切)进行修正,利用电磁仿真软件进行验证;分析了金属粗糙度对于滤波器损耗的影响。修正后的模型仿真结果和测试结果吻合较好,验证了修正后毫米波段高阻硅基参数的有效性,为芯片级毫米波无源器件的设计提供了支撑。     

硅光电倍增器的变温伏安特性及水汽凝结对伏安特性的影响

为了研究硅光电倍增器(SiPM)在低温下能否正常工作,选取了两种典型的SiPM,通过液氮制冷方式,对SiPM在不同温度下的反向伏安特性进行了研究.结果显示,不同SiPM的过偏压范围(VB～Vb)随温度的变化差别很大,并且微量水蒸气凝结仅对未封装的SiPM伏安特性的Vb～VB段有明显影响.分析实验结果得出,SiPM正常工作电压的范围在很大程度上受到衬底材料中缺陷和陷阱浓度的影响.在低温下工作的SiPM,要求其衬底材料中缺陷和陷阱的浓度更低.在进行SiPM的低温应用和测量时,应密切监视偏压加在Vb～VB区间时,器件的电流是否有变化,而不能只观察击穿之前SiPM的漏电情况.     

单晶SiC微纳米压痕的力学行为及仿真分析

为了研究单晶SiC的微观力学性能和加工方式,开展了单晶6H SiC（0001）的微纳米压痕试验,并采用ABAQUS软件对纳米压痕过程进行了数值仿真及完成了试验验证。结果表明,单晶SiC在加载阶段的变形机理与压入载荷无关;硬度和弹性模量表现出了明显的尺寸效应;球形压头作用下的应力值最小,玻氏压头和维氏压头作用下的应力值相同,大于圆锥压头的应力值;压痕裂纹类型有主裂纹、侧向裂纹、主次型裂纹、平直型裂纹、间断型裂纹,裂纹的平均长度随着加载力的增加而逐渐增加。     

The BER theoretical model and properties of SiPM‐based receiver for OOK optical communication

The bit error rate (BER) theory of silicon photomultiplier (SiPM) based on‐off keying optical communication receiver, which introduces photon equivalent threshold is established. The optical crosstalk effect, the dark counts, the amplitude fluctuations of output pulses of SiPM, the baseline fluctuation, the shape of the incident light pulse, the adjacent symbol interference as well as the photon detection efficiency (PDE) are considered in the theory model. The numerical result shows that the average minimum optical power required is much smaller than that of the avalanche photodiode‐based receivers under the same conditions. The BER of SiPM‐based optical communication receiver is very sensitive to the PDE and optical crosstalk (OC) probability of SiPM. For the application of digital optical communication, a SiPM with high PDE but low OC probability and low dark count rate is a preference, under the premise that the output pulse is fast enough. For the state‐of‐the‐art SiPMs, the dark count rate is small enough to obtain adequate BER, and the OC effect is not a big limitation of the performance of SiPM‐based receiver. Moreover, the amplitude fluctuation and the baseline fluctuation of the SiPM‐based receiver are not bottlenecks of the performance in practice.