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.     

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.     

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.     

Effects of defect,carrier concentration and annealing process on the photoluminescence of silicon pn diodes

Silicon pn diodes were fabricated by ion implantation of B and P ions with different doses and subsequent annealing processes. Room temperature photoluminescence (PL) were investigated and the factors affecting the PL intensity were analyzed. Results show that both kinds of pn diodes have PL peak centered at about 1140 nm. Dislocation loops resulted from ion implantation and annealing process may enhance the light emission of silicon pn diode due to its band quantum confinement effect to carriers. The luminescence intensity depends on the carrier concentrations in the implantation region. It should be controlled at the range of 1–6×10¹⁶ cm⁻³. Moreover, the PL intensities of pn diodes with furnace annealing (FA) are higher than those with rapid thermal annealing, and the annealing temperature range for FA is 900–1100 °C.     

Optimisation of implantation conditions for the formation of buried SiO2 layers in silicon

The substrate temperature dependence of the IR transmission spectra of buried silicon dioxide layers formed by high dose ion implantation (~1017) was investigated for an ion dose ranging from 1017 to 1018 ions/cm2 at 250°C of 16O+ at 100 keV energy. The IR spectra indicate that the silicon/silicon-dioxide/silicon can be obtained after thermal annealing treatment of the implanted sample for 10 mm in hydrogen ambient at 1100°C.     

Crystallization induced by thermal annealing with millisecond pulses in silicon-on-insulator films implanted with high doses of hydrogen ions

The crystallization of silicon-on-insulator films, implanted with high doses of hydrogen ions, upon annealing with millisecond pulses is studied. Immediately after hydrogen-ion implantation, the formation of a three-phase structure composed of silicon nanocrystals, amorphous silicon, and hydrogen bubbles is detected. It is shown that the nanocrystalline structure of the films is retained upon pulsed annealing at temperatures of up to ～1000°C. As the temperature of the millisecond annealing is increased, the nanocrystal dimensions increase from 2 to 5 nm and the fraction of the nanocrystalline phase increases to ～70%. From an analysis of the activation energy of crystal phase growth, it is inferred that the process of the crystallization of silicon films with a high (～50 at %) hydrogen content is limited by atomic-hydrogen diffusion.     

Science and prospects for non-stoichiometry in dielectrics

Si nanodots (NDs) were produced in a silicon-rich dielectric matrix by plasma-enhanced chemical vapor deposition. After rapid thermal annealing at 900°C, the Si NDs have a mean diameter of 3 nm and a sheet density of 10¹¹/cm², as determined by the transmission electron microscopy. The photoluminescence (PL) spectrum is red-shifted after the annealing. The electroluminescence spectrum from Al/Si NDs embedded silicon nitride/ Si device structure was investigated. The spectrum was spread from 400 to 750 nm and is blue-shifted as compared to the PL spectrum. The device electrical characteristics, with as-deposited and annealed Si NDs embedded in the silicon nitride layer, were investigated at room temperature. The current transport was found to be strongly correlated to the Si NDs. The annealed Si NDs have lower energy states, which are consistent with the shift of the PL spectrum.     

MBE growth of ultrathin III–V nanowires on a highly mismatched SiC/Si(111) substrate

The possibility in principle of growing III–V GaAs, AlGaAs, and InAs nanowires (NWs) on a silicon substrate with a nanometer buffer layer of silicon carbide is demonstrated for the first time. The diameter of these NWs is smaller than that of similar NWs grown on a silicon substrate. In particular, the minimum diameter is less than 10 nm for InAs NWs. In addition, it was assumed on the basis of photoluminescence measurements that, when AlGaAs NWs are grown on these substrates, a complex structure is formed due to the self-organized formation of AlGaAs quantum dots with a lower content of aluminum, embedded in the NWs.     

Study of silicon doped with zinc ions and annealed in oxygen

The results of studies of the surface layer of silicon and the formation of precipitates in Czochralski n-Si (100) samples implanted with ⁶⁴Zn⁺ ions with an energy of 50 keV and a dose of 5 × 10¹⁶ cm^–2 at room temperature and then oxidized at temperatures from 400 to 900°C are reported. The surface is visualized using an electron microscope, while visualization of the surface layer is conducted via profiling in depth by elemental mapping using Auger electron spectroscopy. The distribution of impurity ions in silicon is analyzed using a time-of-flight secondary-ion mass spectrometer. Using X-ray photoelectron spectroscopy, the chemical state of atoms of the silicon matrix and zinc and oxygen impurity atoms is studied, and the phase composition of the implanted and annealed samples is refined. After the implantation of zinc, two maxima of the zinc concentration, one at the wafer surface and the other at a depth of 70 nm, are observed. In this case, nanoparticles of the Zn metal phase and ZnO phase, about 10 nm in dimensions, are formed at the surface and in the surface layer. After annealing in oxygen, the ZnO · Zn₂SiO₄ and Zn · ZnO phases are detected near the surface and at a depth of 50 nm, respectively.     

纳米硅/二氧化硅发光膜的窄发光带

用电化学方法制备了含有纳米硅点的光致发光二氧化硅膜,发现其激发谱分别在２４６ ｎｍ 及５０６ ｎｍ 附近有极大值。当激发波长在５０６ ｎｍ 附近时,观测到一个强度很弱但发射谱线宽度只有约０ ．０５ ｅＶ 的发光带,远小于２５０ ｎｍ 激发时的发射光谱的宽度（ 约０ ．５０ ｅＶ） 。此窄发光带的发光波长及峰型随激发波长的变化而变化,分析表明它起源于硅氧化合物中的纳米硅点,而短波长（２５０ ｎｍ） 光波激发时的宽发射谱主要来自于二氧化硅中的杂质与缺陷     

Characterization of ultra-shallow p+-n junction diodesfabricated by 500-eV boron-ion implantation

Ultrashallow gated diodes have been fabricated using 500-eV boron-ion implantation into both Ge-preamorphized and crystalline silicon substrates. Junction depths following rapid thermal annealing (RTA) for 10 s at either 950°C or 1050°C were determined to be 60 and 80 nm, respectively. These are reportedly the shallowest junctions formed via ion implantation. Consideration of several parameters, e.g. reduced B⁺ channeling, increased activation, and reduced junction leakage current, lead to the selection of 15 keV as the optimal Ge preamorphization energy. Transmission electron microscope results indicated that an 850°C/10-s RTA was sufficient to remove the majority of bulk defects resulting from the Ge implant. Resulting reverse leakage currents were as low as 1 nA/cm² for the 60-nm junctions and diode ideality factors for crystalline and preamorphized substrates ranged from 1.02 to 1.12. Even at RTA temperatures as low as 850°C, the leakage current was only 11 nA/cm ². The final junction depths were found to be approximately the same for both preamorphized and nonpreamorphized samples after annealing at 950°C and 1050°C. However, the preamorphized sample exhibited significantly improved dopant activation     

n/p ultra-shallow junction formation with plasma immersion ion implantation

n⁺/p ultra-shallow junctions formed by PH₃ plasma immersion ion implantation (PIII) have been studied and diodes with good electrical characteristics have been obtained. The influence of annealing conditions and carrier gas on junction depth and sheet resistance have been studied. It is found that a higher content of H and/or He in silicon can slow down the diffusion of phosphorus and the activation ability of implanted dopant ions in silicon; a shallower junction can been obtained with He rather than H₂ as the carrier gas; and the influence of annealing at 850°C for 20 s on sheet resistance is opposite to that of annealing at 900°C for 6 s on sheet resistance. In addition, mechanisms of unusual electrical characteristics for some diodes are discussed and analyzed in this paper.     

GaN p–n junction diode formed by Si ion implantation into p-GaN

²⁸Si⁺ implantation into Mg-doped GaN, followed by thermal annealing in N₂ was performed to achieve n⁺-GaN layers. The carrier concentrations of the films changed from 3×10¹⁷ (p-type) to 5×10¹⁹ cm⁻³ (n-type) when the Si-implanted p-type GaN was properly annealed. Specific contact resistance (ρ_c) of Ti/Al/Pt/Au Ohmic contact to n-GaN, formed by ²⁸Si⁺ implantation into p-type GaN, was also evaluated by transmission line model. It was found that we could achieve a ρ_c value as low as 1.5×10⁻⁶ Ω cm² when the metal contact was alloyed in N₂ ambience at 600 °C. Si-implanted GaN p–n junction light-emitting diodes were also fabricated. Electroluminescence measurements showed that two emission peaks at around 385 and 420 nm were observed, which could be attributed to the near band-edge transition and donor-to-acceptor transition, respectively.