Luminescence Properties of Nanometer Si with Embedded Structure

Blue luminescence at about 431 nm is obtained from epitaxial silicon after C^＋ implantation, annealing in hydrogen ambience and chemical etching sequentially. With increase of chemical etching, the blue peak is enhanced at first, then decreased and substituted by a red peak at last. C=O compounds are introduced during C^＋ implantation and embedded in the surface of nanometer Si formed during annealing, and at last is formed nanometer silicon with embedded structure, which contributes to the blue emission. Presented is the possible mechanism of photoluminescence.     

360-nm Photoluminescence from Silicon Oxide Films Embedded with Silicon Nanocrystals

Si-rich silicon oxide films were deposited by RF magnetron sputtering onto composite Si/SiO2 targets. After annealed at different temperature, the silicon oxide films embedded with silicon nanocrystals were obtained. The photoluminescenee（PL） from the silicon oxide films embedded with silicon nanocrystals was observed at room temperature. The strong peak is at 360 nm, its position is independent of the annealing temperature. The origin of the 360-nm PL in the silicon oxide films embedded with silicon nanoerystals was discussed.     

Molecular dynamics study on splitting of hydrogen-implanted silicon in Smart-Cut® technology

Defect evolution in a single crystal silicon which is implanted with hydrogen atoms and then annealed is investigated in the present paper by means of molecular dynamics simulation. By introducing defect density based on statistical average, this work aims to quantitatively examine defect nucleation and growth at nanoscale during annealing in Smart-Cut~ technology. Research focus is put on the effects of the implantation energy, hydrogen implantation dose and annealing temperature on defect density in the statistical region. It is found that most defects nucleate and grow at the annealing stage, and that defect density increases with the increase of the annealing temperature and the decrease of the hydrogen implantation dose. In addition, the enhancement and the impediment effects of stress field on defect density in the annealing process are discussed.     

Design and research of quasi-planar self-aligned silicon avalanche electron emission array

The device structure and technical processings of quasi-planar self-aligned silicon avalanche electron emission array arc introduced. The processing step at the edge of electron emission region is about 10nm only and the width of self-aligned current channel of shallow As implantation is about 3μm. Its I-V characteristics show a larger linear region and lower series resistance than that of the previous silicon avalanche electron emission devices. Some of the electron emission characteristics are also discussed in this paper.     

Fabrication of Ultrathin SiO2 Gate Dielectric by Direct Nitrogen Implantation into Silicon Substrate

Nitrogen implantation in silicon substrate at fixed energy of 35keV and split dose of 1e14～5×1e14cm－2 is performed before gate oxidation.The experiment results indicate that with the increasing of implantation dose of nitrogen,oxidation rate of gate decreases.The retardation in oxide growth is weakened due to thermal annealing after nitrogen implantation.After nitrogen is implanted at the dose of 2×1e14cm－2,initial O2 injection method which is composed of an O2 injection/N2 annealing/main oxidation,is applied for preparation of 3.4nm gate oxide.Compared with the control process,which is composed of N2 annealing/main oxidation，initial O2 injection process suppresses leakage current of the gate oxide.But Qbd and HF C-V characteristics are almost identical for the samples fabricated by two different oxidation processes.     

Solid-phase Crystallization of Hydrogenated Amorphous Silicon on Glass Substrates

Amorphous silicon films prepared by PECVD on glass substrate have been crystallized by conventional furnace annealing and rapid thermal annealing（RTA）, respectively. From the Raman spectra, X- ray diffraction and scanning electron microscope, it is found that the grain size is crystallized at 850 ℃ in both techniques. The thin film made by RTA is smooth and of perfect structure, the thin film annealed by FA has a highly structural disorder. An average grain size of about 30 nm is obtained by both techniques.     

Photoluminescence properties and chemical bond variations of SiN x :H films with silicon quantum dots

Hydrogenated silicon nitride(SiNx :H) thin films are deposited on p-type silicon substrates by plasma enhanced chemical vapor deposition(PECVD) using a gas mixture of ammonia and silane at 230 °C.The chemical compositions and optical properties of these films,which are dealt at different annealing temperatures,are investigated by Fourier transform infrared(FTIR) absorption spectroscopy and photoluminescence(PL) spectroscopy,respectively.It is shown that the FTIR presents an asymmetric Si-N stretching mode,whose magnitude is enhanced and position is shifted towards higher frequencies gradually with the increase of the annealing temperature.Meanwhile,it is found that the PL peak shows red shift with its magnitude decreasing,and disappears at 1100 °C.The FTIR and PL spectra characteristics suggest that the light emission is attributed to the quantum confinement effect of the carriers inside silicon quantum dots embedded in SiNx : H thin films.     

Effects of post-annealing treatment on the structure and photoluminescence properties of CdS/PS nanocomposites prepared by sol-gel method

CdS nanocrystals have been successfully grown on porous silicon (PS) by sol-gel method. The plan-view field emission scanning electron microscopy (FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of CdS are broadly distributed on the surface of PS substrate. With the increase of annealing time, the CdS nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of ZnO/PS show that CdS nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence (PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of CdS/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.     

Surface roughening in ion implanted 4H-silicon carbide

Silicon carbide (SiC) devices have the potential to yield new components with functional capabilities that far exceed components based on silicon devices. Selective doping of SiC by ion implantation is an important fabrication technology that must be completely understood if SiC devices are to achieve their potential. One major problem with ion implantation into SiC is the surface roughening that results from annealing SiC at the high temperatures which are needed to activate implanted acceptor ions, boron or aluminum. This paper examines the causes and possible solutions to surface roughening of implanted and annealed 4H-SiC. Samples consisting of n-type epilayers (5 × 10¹⁵ cm⁻³, 4 μm thick) on 4H-SiC substrates were implanted with B or Al to a total dose of 4 × 10¹⁴ cm⁻² or 2 × 10¹⁵ cm⁻², respectively. Roughness measurements were made using atomic force microscopy. From the variation of root mean square (rms) roughness with annealing temperature, apparent activation energies for roughening following implantation with Al and B were 1.1 and 2.2 eV, respectively, when annealed in argon. Time-dependent activation and surface morphology analyses show a sublinear dependence of implant activation on time; activation percentages after a 5 min anneal following boron implantation are about a factor of two less than after a 40 min anneal. The rms surface roughness remained relatively constant with time for anneals in argon at 1750°C. Roughness values at this temperature were approximately 8.0 nm. Annealing experiments performed in different ambients demonstrated the benefits of using silane to maintain good surface morphology. Roughnesses were 1.0 nm (rms) when boron or aluminum implants were annealed in silane at 1700°C, but were about 8 and 11 nm for B and Al, respectively, when annealed in argon at the same temperature.     

Self-diffraction in Porous Silicon/PMMA-DR1 Composite Films

Two-layer structure consisting of PS/PMMA-DR1 composite film planar waveguide layer on porous silicon cladding layer was fabricated in our experiment. The induced grating based on the third nonlinear optical properties was formed by interaction of two Nd ： YAG laser beams at 1 064 nm in the porous silicon/PMMA-DR1 waveguide. The diffraction efficiency of the first order diffracted light is measured to be about 0.2% of the total output.     

注碳外延硅光致蓝光发射研究

N型外延硅经过碳注入、氢气氛下高温退火和电化学腐蚀后,发出峰值波长位于431nm左右的蓝色荧光。随电化学腐蚀条件的变化,蓝色荧光峰先变强后消失,并出现位于716nm处的红光峰。研究认为样品中C=O复合体杂质镶嵌在退火过程所形成的纳米硅颗粒的表面而形成的纳米硅镶嵌结构导致了蓝光发射。     

注C~+外延硅的光致发光特性

在N型外延硅中注入C+并经高温退火形成了Si C沉积.不同条件下进行阳极氧化腐蚀后,在2 6 0 nm光激发下获得了340 nm和4 30 nm的紫外和紫光峰,它们的单色性很好,半高宽(FWHM)约为10 nm.在以上条件下Si C沉积并未多孔化,认为340 nm和4 30 nm峰可能源于样品中的C、O杂质镶嵌于纳米硅表面所形成的发光中心.讨论了各种发光中心形成的可能条件,并对实验结果做出了初步解释.     

Growth of silicon nanoclusters in thermal silicon dioxide under annealing in an atmosphere of nitrogen

It is found for the first time that silicon nanoclusters are formed in the surface layer of thermal silicon dioxide under high-temperature annealing (T = 1150°C) in dried nitrogen. Analysis of the cathodoluminescence spectra shows that an imperfect surface layer appears upon such annealing of silicon dioxide, with silicon nanoclusters formed in this layer upon prolonged annealing. Transmission electron microscopy demonstrated that the silicon clusters are 3–5.5 nm in size and lie at a depth of about 10 nm from the surface. Silicon from the thermal film of silicon dioxide serves as the material from which the silicon nanoclusters are formed. This method of silicon-nanocluster formation is suggested for the first time.     

退火温度对碳注入外延硅蓝光发射特性的影响

获得了不同退火温度注碳外延硅的蓝光发射谱,分析了退火温度对其蓝光发射特性的影响,发现退火温度为 1 000℃样品具有最强的发射强度。认为经碳注入所引入的杂质C = O 复合体是发光的重要因素;经碳注入氮气氛中退火及电化学腐蚀处理形成纳米硅镶嵌结构,因量子限制效应–表面复合效应而发光。     

Effect of the annealing conditions on the electrical characteristics of p+/n shallow junctions

Shallow p+/n junctions are produced by low-energy (10-keV) boron implantation into amorphous silicon layers formed by a prior implantation of Si+ ions. Junctions about 0.1 µm deep with good electrical characteristics (reverse current density Jr< 10^-7A/cm²at - 1 V) are obtained both by electron-beam annealing (1100°C, 2 s) and conventional furnace annealing (800°C, 30 min). It is shown that, in the case of the furnace treatment, lower annealing temperatures produce very high reverse currents, while excellent electrical characteristics (Jr< 10^-8A/cm²) are achieved at higher annealing temperatures (900°C), the junction extending, however, much deeper into silicon (0.26 µm).     

Mo＋C双注入纯铁纳米相结构的形成和改性机理研究

Mo C双注入H13钢可明显地改善钢表面的抗腐蚀特性，然而改性机理却很少报道，我们对Mo C双注入纯铁微观结构变化进行了分析，用透射电子显微镜首次发现三元FeMo2C相，这种相在较低的束流密度和注入量下首先形成，随着束流密度和注入量的增加，碳化钼和碳化铁相形成。这些FeMo2C和MoC相均匀地弥散在注入层中，其尺寸在10－30nm，当束流密度增加到0.5A.m^-2，这些纳米相的密度和尺寸增加，形成了均匀的弥散强化结构，并且发现MoC相均匀分布在晶界间，这种结构形成了抗磨损的优化表面层和抗腐蚀的印化层，明显改善了材料表面抗磨损，抗疲劳和抗腐蚀特性。     

Formation of cobalt silicided shallow junction using implantinto/through silicide technology and low temperature furnace annealing

This work investigates the shallow CoSi₂ contacted junctions formed by BF₂⁺ and As⁺ implantation, respectively, into/through cobalt silicide followed by low temperature furnace annealing. For p⁺n junctions fabricated by 20 keV BF₂⁺ implantation to a dose of 5×10¹⁵ cm^-2, diodes with a leakage current density less than 2 nA/cm² at 5 V reverse bias can be achieved by a 700°C/60 min annealing. This diode has a junction depth less than 0.08 μm measured from the original silicon surface. For n⁺p junctions fabricated by 40 keV As⁺ implantation to a dose of 5×10¹⁵ cm^-2, diodes with a leakage current density less than 5 nA/cm² at 5 V reverse bias can be achieved by a 700°C/90 min annealing; the junction depth is about 0.1 μm measured from the original silicon surface. Since the As⁺ implanted silicide film exhibited degraded characteristics, an additional fluorine implantation was conducted to improve the stability of the thin silicide film. The fluorine implantation can improve the silicide/silicon interface morphology, but it also introduces extra defects. Thus, one should determine a tradeoff between junction characteristics, silicide film resistivity, and annealing temperature     

Formation of nickel disilicide using nickel implantation and rapid thermal annealing

Transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS), and x-ray photoemission spectroscopy (XPS) have been used to investigate the nucleation, growth, and ripening behavior of nickel-disilicide precipitates formed by Ni implantation in an amorphous-Si layer on (100) Si and followed by a two-step annealing treatment. The TEM and XPS results show that amorphous-disilicide precipitates are formed in a depth of ∼21 nm in the amorphous-Si layer when pre-annealed at 380°C for 30 sec. It is also shown that the second-step annealing at temperatures in the range of 450–600°C causes the amorphous precipitates to transform to randomly oriented crystalline ones embedded in the amorphous-Si layer. Annealing above 550°C is shown to induce the crystallization of amorphous Si by solid-phase epitaxial growth (SPEG). It is further shown that, in a prolonged annealing at high temperatures, the disilicide has dissolved and reprecipitated on the Si surface. Based on the roles of the silicide-mediated crystallization (SMC), the dissolution and reprecipitation of silicides, and SPEG, possible mechanisms are given to explain how the surface-disilicide islands are formed during annealing at temperatures of 550–950°C.