Charge storage characteristics of hydrogenated nanocrystalline silicon film prepared by rapid thermal annealing

The early stages of hydrogenated nanocrystalline silicon (nc-Si:H) films deposited by plasma-enhanced chemical vapour deposition were characterized by atomic force microscopy. To increase the density of nanocrystals in the nc-Si:H films, the films were annealed by rapid thermal annealing (RTA) at different temperatures and then analysed by Raman spectroscopy. It was found that the recrystallization process of the film was optimal at around 1000℃. The effects of different RTA conditions on charge storage were characterized by capacitance--voltage measurement. Experimental results show that nc-Si:H films obtained by RTA have good charge storage characteristics for nonvolatile memory.     

Size control of Si nanocrystals by two-step rapid thermal annealing of sputtered Si-rich oxide/SiO2 superlattice

Controllable size of silicon (Si) nanocrystals can be achieved by a two-step rapid thermal annealing technique consisting of rapid annealing at 1000°C in nitrogen ambient and rapid oxidation at 600–800°C of a radio frequency magnetron co-sputtered Si-rich oxide/SiO₂ superlattice structure. The photoluminescence (PL) spectra related to Si nanocrystals were observed in the visible range (600–900 nm). After rapid oxidation, the size of the nanocrystals was reduced and the quality of the Si nanocrystal/SiO₂ interface was improved, resulting in a blue shift and an increase of the PL peak intensity. Finally, annealing in air increases the PL intensity further.     

Beneficial effect of rapid recurrent thermal annealing on magnetic properties of SmCo-based films

The effects of conventional thermal annealing (CTA) and rapid recurrent thermal annealing (RRTA) on the magnetic properties of the SmCo-based films were investigated. The results show that the CTA-treated films exhibit amorphous structure with coercivity insensitively depending on annealing parameters as anticipated. As for the RRTA-treated films, single TbCu₇-type phase structure with well crystallization is observed. The coercivity of the RRTA-treated films is strongly correlated with annealing parameters, and its optimum value is larger than that of the CTA-treated films. It is suggested that the RRTA treatment has beneficial effects on the magnetic properties of the SmCo-based films.     

Size and density control of silicon oxide nanowires by rapid thermal annealing and their growth mechanism

In this work, we demonstrate a fast approach to grow SiO₂ nanowires by rapid thermal annealing (RTA). The material characteristics of SiO₂ nanowires are investigated by field emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field (HAADF) imaging, electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM). The HAADF images show that the wire tip is predominantly composed of Pt with brighter contrast, while the elemental mappings in EFTEM and EELS spectra reveal that the wire consists of Si and O elements. The SiO₂ nanowires are amorphous with featureless contrast in HRTEM images after RTA at 900°C. Furthermore, the nanowire length and diameter are found to be dependent on the initial Pt film thickness. It is suggested that a high SiO₂ growth rate of >1 μm/min can be achieved by RTA, showing a promising way to enable large-area fabrication of nanowires.     

Structural and electrochemical investigation of Zn-doped LiCoO2 powders

A commercial cathode material (LiCoO₂) was modified by doping with Zn to improve its performance in lithium battery. The structure and morphology of the doped cathode material were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). The synthesized samples were characterized using X-ray photoelectron spectra (XPS), used to investigate the elementary states on the system. The electrical conductivity variations of doped powders were measured in the temperature range between 30 and 150?°C. The 3?mol% Zn-doped LiCoO₂ sample shows the highest reversibility capacity (178?mA?h g^?1) after 30 cycles in the voltage window 3.0?C4.5?V.     

Formation of palladium silicide by rapid thermal annealing

The formation of palladium silicide Pd₂Si by rapid thermal annealing of Pd layers on silicon has been studied as a function of annealing time (1–60s) in the temperature range 350–500 °C. It is shown that the results found for conventional furnace annealing (long duration, low temperature) can be extrapolated for rapid thermal annealing (shorter time, higher temperature) when taking into account the exact time dependence of the short temperature cycle. The growth rate is essentially diffusion limited and the activation energy is close to 1.1±0.1 eV. Silicide resistivity of about 30–40 cm was obtained for 200–400 nm thick Pd₂Si layers formed at 400 °C for a few seconds.     

退火对B掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用热丝化学气相沉积法制备B掺杂纳米金刚石薄膜,并对薄膜进行真空退火处理,系统研究了不同退火温度对B掺杂纳米金刚石薄膜的微结构和电化学性能的影响.结果表明,当退火温度升高到800 ℃后,薄膜的Raman谱图中由未退火时在1157,1346,1470,1555 cm^-1处的4个峰转变为只有D峰和G峰,说明晶界上的氢大量解吸附量减少,并且D峰和G峰的积分强度比I_D/I_G值变为最小,即sp²相团簇     

Morphological and optical properties of soft-landed supported nanoclusters: effect of rapid thermal annealing

We report the formation of large islands of bi-modal lateral size distributions having one peak at lateral size ～100 nm (height ～70 nm) and another at ～160 nm (height ～110 nm) by soft-landing of size-selected copper nanoclusters (3 nm in diameter) at room temperature (26 °C). Si(100) wafer containing native oxide is used as substrate. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to study the morphological aspects and for optical aspect cathodoluminescence measurement is used. Rapid thermal annealing (RTA) (200 °C, dry N₂, 120 s) induced effects on the morphology shows that individual islands are morphologically stable. A careful qualitative study of the optical property using cathodoluminescence in a SEM before and after the thermal treatment, using RTA, reveals very low diffusion of the cluster material into the substrate.     

Effects of rapid thermal annealing on the morphology and optical property of ultrathin InSb film deposited on SiO2/Si substrate

Ultrathin InSb films on SiO2/Si substrates are prepared by radio frequency(RF) magnetron sputtering and rapid thermal annealing(RTA) at 300,400,and 500℃,respectively.X-ray diffraction(XRD) indicates that InSb film treated by RTA at 500℃,which is higher than its melting temperature(about 485℃),shows a monocrystalline-like feature.A high-resolution transmission electron microscopy(HRTEM) micrograph shows that melt recrystallization of InSb film on SiO2/Si(111) substrate is along the(111) planes.The transmittances of InSb films decrease and the optical band gaps redshift from 0.24 eV to 0.19 eV with annealing temperature increasing from 300℃ to 500℃,which is indicated by Fourier transform infrared spectroscopy(FTIR) measurement.The observed changes demonstrate that RTA is a viable technique for improving characteristics of InSb films,especially the melt-recrystallized film treated by RTA at 500℃.     

退火时间对硼掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用高分辨透射电镜、紫外和可见光Raman光谱及循环伏安法研究了1000 ℃下退火不同时间的硼掺杂纳米金刚石薄膜的微结构和电化学性能. 结果表明,随退火时间的延长,薄膜中纳米金刚石晶粒尺寸逐渐减小.当退火时间为0.5 h时, 金刚石晶粒尺寸由未退火样品的约15 nm减小为约8 nm, 金刚石相含量增加;当退火时间为2.0 h时,金刚石晶粒减小为2—3 nm, 此时晶界增多,金刚石相含量减少;退火时间为2.5 h时纳米金刚石晶粒尺寸和金刚石相含量又略有上升.晶粒尺寸和金刚石相含量的变化表明薄膜在退火过程中发生了金刚石和非晶碳相的相互转变.可见光Raman光谱测试结果表明,不同退火时间下, G峰位置变化趋势与I_D/I_G值变化一致,说明薄膜内sp²碳团簇较大时, 非晶石墨相的有序化程度较高.退火0.5, 1.0, 1.5和2.0 h时, 电极表面进行准可逆电化学反应,而未退火和退火时间为2.5 h时电极表面进行不可逆电化学反应.退火有利于提高薄膜电极的传质效率, 退火0.5 h时薄膜电极的传质效率最高,催化氧化性能最好.较小的晶粒尺寸、 较高的金刚石相含量以及纳米金刚石晶粒的均匀分布有利于提高电极表面反应的可逆性和催化氧化性能.     

A comprehensive overview on the structure and comparison of magnetic properties of nanocrystalline synthesized by a thermal treatment method

This study reports the simple synthesis of MFe₂O₄ (where M=Zn, Mn and Co) nanostructures by a thermal treatment method, followed by calcination at various temperatures from 723 to 873 K. Poly(vinyl pyrrolidon) (PVP) was used as a capping agent to stabilize the particles and prevent them from agglomeration. The pyrolytic behaviors of the polymeric precursor were analyzed by use of simultaneous thermo-gravimetry analyses (TGA) and derivative thermo-gravimetry (DTG) analyses. The characterization studies were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of metal oxide bands for all the calcined samples. Magnetic properties were demonstrated by a vibrating sample magnetometer (VSM), which displayed that the calcined samples exhibited different types of magnetic behavior. The present study also substantiated that magnetic properties of ferrite nanoparticles prepared by the thermal treatment method, from viewing microstructures of them, can be explained as the results of the two important factors: cation distribution and impurity phase of α-Fe₂O₃. These two factors are subcategory of the preparation method which is related to macrostructure of ferrite. Electron paramagnetic resonance (EPR) spectroscopy showed the existence of unpaired electrons ZnFe₂O₄ and MnFe₂O₄ nanoparticles while it did not exhibit resonance signal for CoFe₂O₄ nanoparticles.     

Electrical activation of boron-implanted silicon during rapid thermal annealing

The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B⁺ fluences ranging between 5×10¹⁴ and 1×10¹⁶cm⁻² and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT<1000°C and cannot be completed in times typical of rapid thermal annealing (a few tens of seconds). The analysis of carrier profiles indicates that the time constant for activation is strongly affected by local damage and dopant concentration. If the total boron concentration exceeds equilibrium solubility, precipitation occurs concomitant to activation, even if the substitutional boron fraction is still lower than equilibrium solubility. ForT≧1000°C complete activation is obtained in times of about 10 s. In the case of preamorphized Si the activation occurs very quickly, during the recrystallization of the amorphous layer, for all the examined temperatures.     

利用快速退火法从非晶硅薄膜中生长纳米硅晶粒

报道了一种从非晶硅薄膜中生长纳米硅晶粒的方法。含氢非晶硅薄膜经过快速热退火处理后，用拉曼散射和X射线衍射技术对样品进行分析。实验结果表明：纳米硅晶粒不但能在非晶硅薄膜中形成，而且所形成的纳米硅晶粒的大小随着热退火过程中升温快慢而变化。在升温过程中，若单位时间内温度变化量较大（－100℃/s），则所形成纳米硅粒较小（1．6－15nm）； 若单位时间内温度变化量较低（－1℃/s），则纳米硅粒较大（23－46nm）。根据晶体生长理论和计算机模拟，讨论了升温快慢与所形成的纳米硅颗粒大小的关系。     

Effects of rapid thermal annealing on the structural properties of TiO2 nanotubes

The structural properties of TiO₂ nanotubes with rapid thermal annealing (RTA) and traditional thermal annealing in O₂ were studied by X-ray diffraction (XRD) and Raman scattering measurements. From analyzing the line width of XRD and the correlation length of the Raman peak, we demonstrate that RTA can be an effective tool for amorphous-anatase transformation in TiO₂ nanotubes. The Raman peak redshifts and reduces its line width after thermal annealing and RTA, which may involves the reduction of oxygen-related defects.     

Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species

The growth kinetics is characterized and the moving species is identified for the formation of Ni₂Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a 100 Si substrate. The interfacial Ni₂Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350–450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni₂Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni₂Si formation.     

Studies on the effect of titanium addition on LiCoO2

The lithiated transition metal oxide has been used as the cathode materials for lithium ion rechargeable batteries. Among the various cathode materials, LiCoO₂ has been widely used. There are lot of reports on the substituted LiCoO₂ replacing small amount of Cobalt with other transition and nontransitional metals. Here, we focus on to a tetravalent transition metal atom such as titanium, as an addition in LiCoO₂ and studied its performance. The titled cathode material was synthesized by solid-state reaction method. Thermogravimetric/differential thermal analysis, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and particle size analysis were carried out to assess the effect of addition of titanium on LiCoO₂. Electrochemical studies were carried out by cyclic voltammetry and life cycle analyzer.     

Structural characterization of SiGe nanoclusters formed by rapid thermal annealing

This work presents the structural characterization of nanoclusters formed from a-Si:H/Ge heterostructures processed by rapid thermal annealing (RTA) at 1000 °C for annealing times varying between 30 s and 70 s. The a-Si:H layers were grown on electron cyclotron resonance (ECR) using SiH₄ and Ar precursor gases. The Ge layer was grown in an e-beam evaporation system. The structural characterizations were performed by high-resolution X-ray diffractometer (HRXRD) on grazing incidence X-ray reflection mode (GIXRR) and micro-Raman measurements. The average grain size, Ge concentration (x_Ge) and strain were estimated from Lorentzian GIXRR peak fit. The average grain size varied from 3 nm to 7.5 nm and decreased with annealing time. The x_Ge increase with annealing time and varied from 8% to 19%, approximately. The strain calculated for (1 1 1), (2 2 0) and (3 1 1) peaks at 40 s, 50 s, 60 s and 70 s annealing time suggest the geometrical changes in nanoclusters according to process time.     

Effects of annealing temperature on YAG:Ce synthesized by spray-drying method

In this report, YAG:Ce phosphors were synthesized by spray-drying method. The effects of annealing temperature on crystal structure, morphology and photoluminescence property (PL) of as-prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrofluorometer, respectively. The XRD patterns showed all the samples are in consistence with a single garnet phase, and the location of strongest peak shifts to smaller angle with increasing the annealing temperature. The SEM micrographs revealed the sample annealed at 1200 °C appears to be a spherical polycrystalline aggregate; as the samples were annealed at 1300?1400 °C, spherical grains obviously grow up; but the sample annealed at over 1400 °C forms an irregular bulk. The emission spectra of samples indicated the PL of samples annealed at 1200?1400 °C improve with increasing the annealing temperature because of the diffusion of Si⁴⁺ ions; whereas the PL of sample annealed at the temperature over 1400 °C decreases likely resulting from inflection effects of multiangular shape of grains. Therefore, the samples annealed at 1400 °C are suitable for gaining phosphor with high brightness and good morphology.