退火温度对嵌入Si中的β-FeSi2颗粒发光的影响

研究了退火温度对分子束外延(MBE)方法生长的Si基β-FeSi2颗粒的发光性质和电学特性的影响.结果表明,在900℃下退火的样品,虽然β-FeSi2的结晶质量有所提高,但是由于晶格失配和热膨胀系数的不同,在Si中引入位错,导致样品的光致发光谱展宽和形成的二极管漏电流增大.而在800℃下退火的样品,具有较低的漏电流和较强的室温电致发光谱.     

退火温度对嵌入Si中的β-FeSi2颗粒发光的影响

研究了退火温度对分子束外延(MBE)方法生长的Si基β-FeSi2颗粒的发光性质和电学特性的影响.结果表明,在900℃下退火的样品,虽然β-FeSi2的结晶质量有所提高,但是由于晶格失配和热膨胀系数的不同,在Si中引入位错,导致样品的光致发光谱展宽和形成的二极管漏电流增大.而在800℃下退火的样品,具有较低的漏电流和较强的室温电致发光谱.     

碳掺杂β-FeSi2薄膜的电子显微学研究

本文利用透射电子显微镜对离子注入合成的β-FeSi2和β-Fe(C,Si)2薄膜进行了对比研究.电镜观察结果表明,选择C作为掺杂元素,能够得到界面平直、厚度均一的高质量β相薄膜,晶粒得到细化,β-FeSi2层稳定性提高.尤其在60kV、4×1017ions/cm2条件下注入直接形成非晶,在退火后会晶化为界面平滑、厚度均匀的β-FeSi2薄膜.因此从微结构角度考虑,引入C离子有益于提高β-FeSi2薄膜的质量.     

C掺杂对离子注入合成β-FeSi2薄膜的影响

采用离子注入方法制备β-FeSi2薄膜,选择C作为掺杂元素,得到了β-FeSi2硅化物层与基体间的界面平直、厚度均一的高质量薄膜.经透射电镜分析可知,引入C离子后硅化物层的微结构向有利于薄膜质量的方向发展,晶粒得到细化,β-FeSi2层稳定性提高.从微结构角度考虑,引入C离子对于提高β-FeSi2薄膜的质量是很有益处的.进一步进行光学吸收表征,发现C离子的引入对β-FeSi2层的Egd值没有产生不良影响.讨论了Egd值的影响因素,如制备方法、工艺参数、基体取向、掺杂离子种类、掺杂离子数量、退火温度等等,解释了文献报道的不同Egd值.     

Si衬底上采用溅射Fe/Si纳米多层结构制备β-FeSi2薄膜

采用磁控溅射的方法在Si衬底上生长Fe/Si多层膜,退火后形成了硅化物薄膜。利用X射线衍射(XRD)、Raman光谱、原子力显微镜(AFM)研究了Fe/Si膜厚比和退火温度对薄膜结构特性的影响。研究表明,当Fe/Si膜厚比为1/2,预先在衬底上沉积Fe缓冲层,退火温度为750℃,形成的硅化物为β-FeSi2,晶粒的平均尺寸大约为50nm,且分布得比较均匀。如果Fe/Si厚度比为1/1或3/10时,形成的硅化物为ε-FeSi。随着退火温度的升高,Fe/Si之间的相互扩散逐渐增强,当退火温度为1 000℃时,形成了富硅的二硅化物的高温相α-FeSi2。     

退火气氛对铝诱导a-Si薄膜结晶过程的影响

以玻璃为衬底,室温条件下采用直流磁控溅射技术制备了Glass/Al/a-Si样品.在H2,N2和空气3种不同气氛中进行了退火处理.分别采用XRD,Raman光谱和SEM研究了退火气氛对a-Si薄膜销诱导晶化(AIC)过程的影响.XRD实验结果表明:a-Si薄膜在H2气氛中400℃下经过90min的退火处理就能得到结晶较好的poly-si薄膜.Raman光谱实验结果表明:在500℃下退火处理,相同时间内H2气氛中a-Si结晶程度最好,空气气氛中结晶程度最差.这是因为高温H2退火过程中,高活性H原子能将弱的Si-Si键破坏,并与之反应形成强Si-Si键,使得薄膜结构更加稳定有序,同时能加速薄膜中氧的外扩散,促使薄膜晶化.     

退火气氛对铝诱导a-Si薄膜结晶过程的影响

以玻璃为衬底,室温条件下采用直流磁控溅射技术制备了Glass/Al/a-Si样品.在H2,N2和空气3种不同气氛中进行了退火处理.分别采用XRD,Raman光谱和SEM研究了退火气氛对a-Si薄膜销诱导晶化(AIC)过程的影响.XRD实验结果表明:a-Si薄膜在H2气氛中400℃下经过90min的退火处理就能得到结晶较好的poly-si薄膜.Raman光谱实验结果表明:在500℃下退火处理,相同时间内H2气氛中a-Si结晶程度最好,空气气氛中结晶程度最差.这是因为高温H2退火过程中,高活性H原子能将弱的Si-Si键破坏,并与之反应形成强Si-Si键,使得薄膜结构更加稳定有序,同时能加速薄膜中氧的外扩散,促使薄膜晶化.     

直流磁控溅射工艺参数对β-FeSi_2薄膜性能的影响

采用室温直流磁控溅射Fe-Si组合靶的方法,经过后续Ar气氛围退火,在单晶Si(111)衬底上生长β-FeSi2薄膜。研究了溅射功率、工作气压、Ar气流量、沉积时间等工艺参数对β-FeSi2薄膜结构特性及电学特性的影响,通过Raman、Hall、X射线衍射(XRD)等测试对其性能进行表征,对工艺参数进行了优化,在溅射功率为80W、工作气压为1.3Pa和Ar气流量为35SCCM时溅射沉积Fe-Si薄膜,不仅可以得到单一相的β-FeSi2,而且薄膜结晶质量较好。最终,在上述实验条件下制备得到的未掺杂的β-FeSi2薄膜是n型导电的,β-FeSi2薄膜中载流子浓度约为3.3×1016cm-3,迁移率为381cm2/Vs。     

电致发光谱测量β-FeSi2-Si异质结载流子限制

设计了一种将β-FeSi2颗粒埋入非故意掺杂Si中的Si p-π-n二极管来确定β-FeSi2-Si异质结的能隙差.当二极管处于正向偏置时,通过Si n-p-结注入的电子扩散到β-FeSi2并由于Si与β-FeSi2之间的能隙差而受到限制,电荷在异质结的积累反过来阻挡了电子的继续扩散,将电子局域化在靠近Si n-p-结的p--Si区.少子的局域化减少了非辐射复合的途径,Si和β-FeSi2的发光增强,淬灭速率变慢,在室温低电流下仍可得到Si和β-FeSi2电致发光.Si和β-FeSi2发光强度的比率对温度的依存性表明同型异质结对电子限制能力的减弱符合热发射模型,由此确定出Si和β-FeSi2异质结导带带阶差为0.2eV.     

电致发光谱测量β-FeSi2-Si异质结载流子限制

设计了一种将β-FeSi2颗粒埋入非故意掺杂Si中的Si p-π-n二极管来确定β-FeSi2-Si异质结的能隙差.当二极管处于正向偏置时,通过Si n-p-结注入的电子扩散到β-FeSi2并由于Si与β-FeSi2之间的能隙差而受到限制,电荷在异质结的积累反过来阻挡了电子的继续扩散,将电子局域化在靠近Si n-p-结的p--Si区.少子的局域化减少了非辐射复合的途径,Si和β-FeSi2的发光增强,淬灭速率变慢,在室温低电流下仍可得到Si和β-FeSi2电致发光.Si和β-FeSi2发光强度的比率对温度的依存性表明同型异质结对电子限制能力的减弱符合热发射模型,由此确定出Si和β-FeSi2异质结导带带阶差为0.2eV.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

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正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its