p型纳米硅与a-Si∶H不锈钢底衬nip太阳电池

报道了选用厚度为0.05mm的不锈钢箔作衬底,B掺杂P型氢化纳米硅作窗口层,制备成功开路电压和填充因子分别达到0.90V和0.70的nip非晶硅基薄膜单结太阳电池.UV VIS透射谱和微区Raman谱证实所用p层具有典型氢化纳米硅的宽能隙和含有硅结晶颗粒的微结构特征.明确指出导致这种氢化纳米硅能隙展宽的物理机制是量子尺寸效应.     

p型纳米硅与a-Si：H不锈钢底衬nip太阳电池

报道了选用厚度为0．05mm的不锈钢箔作衬底，B掺杂P型氢化纳米硅作窗口层，制备成功开路电压和填充因子分别达到0．90V和0．70的nip非晶硅基薄膜单结太阳电池．UV-VIS透射谱和微区Raman谱证实所用p层具有典型氢化纳米硅的宽能隙和含有硅结晶颗粒的微结构特征．明确指出导致这种氢化纳米硅能隙展宽的物理机制是量子尺寸效应．     

氢稀释对FTS沉积a-Si:H薄膜结构特性的影响

采用对靶磁控反应溅射技术,以氢气作为反应气体在不同的氢稀释比条件下制备了氢化非晶硅薄膜.利用台阶仪、傅里叶红外透射光谱、Raman谱和紫外-可见光透射谱测量研究了不同氢稀释比对氢化非晶硅薄膜生长速率和结构特性的影响.分析结果发现,利用对靶磁控溅射技术能够实现低温快速沉积高质量氢化非晶硅薄膜的制备.随着氢稀释比不断增加,薄膜沉积速率呈现先减小后增大的趋势.傅里叶红外透射光谱表明,氢化非晶硅薄膜中氢含量先增大后变小.而Raman谱和紫外-可见光透射谱分析发现,氢稀释比的增加使氢化非晶硅薄膜有序度和光学带隙均先增大后减小.可见,此技术通过改变氢稀释比R能够实现氢化非晶硅薄膜结构的有效控制.     

氢稀释对FTS沉积a-Si∶H薄膜结构特性的影响

采用对靶磁控反应溅射技术,以氢气作为反应气体在不同的氢稀释比条件下制备了氢化非晶硅薄膜.利用台阶仪、傅里叶红外透射光谱、Raman谱和紫外-可见光透射谱测量研究了不同氢稀释比对氢化非晶硅薄膜生长速率和结构特性的影响.分析结果发现,利用对靶磁控溅射技术能够实现低温快速沉积高质量氢化非晶硅薄膜的制备.随着氢稀释比不断增加,薄膜沉积速率呈现先减小后增大的趋势.傅里叶红外透射光谱表明,氢化非晶硅薄膜中氢含量先增大后变小.而Raman谱和紫外-可见光透射谱分析发现,氢稀释比的增加使氢化非晶硅薄膜有序度和光学带隙均先增大后减小.可见,此技术通过改变氢稀释比R能够实现氢化非晶硅薄膜结构的有效控制.     

激光干涉结晶法制备一维周期结构的纳米硅阵列

利用激光干涉结晶方法,采用周期为400 nm的一维(1D)移相光栅掩模调制KrF准分子激光器的脉冲激光束斑的能量分布,在不同厚度的超薄氢化非晶硅(a-Si:H)膜内直接制备1D有序纳米硅(nc-Si)阵列.拉曼散射谱表明,样品上呈条状分布的受辐照区域发生晶化.原子力显微镜和透射电子显微镜测试结果表明：1D的nc-Si阵列的周期和移相光栅掩模一样.随着a-Si:H膜厚度从10nm降至4nm,通过控制激光的能量密度,每个周期中nc-Si条状分布区宽度可达到30nm.nc-Si条状分布区的高分辨电子显微镜照片显 关键词： 纳米硅 激光干涉结晶 移相光栅 定域晶化     

KrF准分子激光退火氢化非晶碳化硅薄膜的晶化研究

介绍了利用KrF准分子脉冲激光对氢化非晶碳化硅(a-SiC∶H)薄膜进行激光退火以实现薄膜的结晶化。利用等离子增强化学气相沉积(PECVD)在单晶Si(100)衬底上制备a-SiC∶H薄膜, 再用不同能量密度的激光对薄膜样品进行退火。分析表明, 选用合适能量密度的激光退火能够实现a-SiC∶H薄膜的结晶化, 且结晶颗粒大小随着入射激光能量密度的增加而增大; 显微图表明当入射能量密度超过200 mJ/cm2时, 薄膜表面出现由热弹性波引起的表面波纹现象, a-SiC∶H薄膜结晶过程为液相结晶; 傅里叶红外谱(FTIR)表明随着入射能量密度增加, 薄膜中氢含量降低, Si-C峰增强并且峰位出现蓝移, 薄膜的结晶度提高。     

发蓝绿光纳米硅薄膜的快速热处理制备

使用除氢、高温成核和低温生长的三段式快速热处理方法,将常规方法制备的氢化非晶硅(a-SiH)薄膜晶化成纳米硅(nc-Si)薄膜。该薄膜在波长为457.9nm的Ar⁺激光的激发下,在室温发射出蓝绿光。     

非晶硅太阳能电池研究动向

氢化非晶硅材料对太阳光比通常的晶体硅材料具有较好的吸收特性,因此用非晶硅材料做太阳能电池所需材料较少.此外非晶硅可制成大面积薄膜太阳能电池组件,有大大降低电池造价的前景.因此国际上对非晶硅材料及电池等器件投入了较大的研究力量.近几年已在非晶硅太阳能电池转换效率     

脉冲激光晶化非晶硅薄膜的有限差分模拟

 根据热传导原理,建立了脉冲激光晶化非晶硅薄膜的理论模型。运用有限差分方法研究了不同激光波长、能量密度等因素对薄膜温度变化及相变过程的影响。计算了不同波长激光器对厚度500 nm非晶硅晶化的阈值能量密度。结果发现,准分子晶化的阈值能量密度最低,但是在同样的能量密度下,熔融深度却不及使用更长波长的激光器。计算并分析了升高衬底温度对结晶速度和晶粒尺寸的影响,模拟结果较好地验证了实验结论和规律。     

氢化非晶硅叠层薄膜对单晶硅表面钝化研究

采用等离子体增强化学气相沉积法生长的单层本征氢化非晶硅薄膜对单晶硅片进行钝化,结果表明增加氢稀释比有利于减少薄膜中的缺陷,增强钝化效果,过量的氢稀释比会导致非晶硅在硅片表面的外延晶化生长,降低钝化效果。退火导致非晶硅晶化程度增加,降低了钝化效果,同时退火提升了薄膜的质量,改变了H键合方式,增强了钝化效果。因此,单层氢化非晶硅只有在合适的氢稀释比和退火温度才可以获得最佳钝化效果。为了提高非晶硅薄膜对硅片的钝化效果,采用具有高低氢稀释比的叠层本征非晶硅薄膜对硅片进行钝化。因此将高氢稀释比沉积的非晶硅薄膜叠层生长于低氢稀释比的薄膜之上,避免非晶硅在硅片表面的外延生长。在退火过程中,高氢稀释比薄膜中的氢扩散到低氢稀释比薄膜中,有效地钝化了非晶硅中和单晶硅表面的悬挂键,改善了非晶硅/硅片的界面质量,叠层钝化后硅片的少子寿命为7.36 ms,隐含开路电压为732 mV。     

玻璃与液晶非线性光学界面反射特性的研究

本文系统地研究了由玻璃与液晶构成的非线性光学界面。用一台调Q的红宝石激光器研究了由玻璃与处于各向同性液相的液晶所构成的非线性界面。在不同入射角时非线性界面由内部全反射跃变到部分透射的阈值光强与Kaplen的平面波理论计算结果相一致。在T-T_c=2.5℃条件下测量了时间分辨的非线性界面的反射率。观察到了反射率的滞后迴线。非线性界面的这种反射率的滞后迴线可以归之于液晶分子退取向的弛豫过程。用Ar⁺激光器研究了玻璃与向列相液晶所构成的非线性光学界面,观察到了由相变而产 关键词：     

Phase transitions in <Emphasis Type="Italic">a</Emphasis>-Si:H films on a glass irradiated by high-power femtosecond pulses: Manifestation of nonlinear and nonthermal effects

The crystallization of amorphous silicon films 90-nm thick irradiated by laser pulses (a wavelength of 800 nm and a pulse duration of 120 fs) is investigated using Raman scattering spectroscopy and electron microscopy. The absorption coefficient for 800-nm low-power probe radiation by an a-Si:H film is small but can increase owing to nonlinear effects for high-power pulses. According to the estimates, the energy absorbed in the film is insufficient for its heating and complete melting but is sufficient for the generation of free charge carriers with a density of about 10²² cm^?3. The electron and phonon temperatures in this case are strongly different and silicon becomes unstable. Thus, the action of such a short laser pulse cannot be reduced only to the heating effects and subsequent phase transitions through the liquid or solid phase.     

Simulation of the melting and crystallization processes in monocrystalline silicon exposed to nanosecond laser radiation

Numerical simulation of the melting and crystallization processes of monocrystalline silicon exposed to the nanosecond radiation of a ruby laser was carried out with the kinetics of the phase transformations accounted for on the basis of Kolmogorov equations. A two-dimensional mechanism of nucleation and growth of the new phase was invoked to describe the phase transitions. It was shown that the temporal dependences of monocrystal overheating and liquid phase supercooling in the melting and crystallization stages, respectively, are nonmonotonic and determined by the kinetics of the phase transitions. The maximum values of the overheating and supercooling were ∼100 K.     

Excimer laser crystallization of amorphous silicon on metallic substrate

An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J?cm^?2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J?cm^?2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites’ columnar growth.     

Laser Melting Solidification Process of Y-Ba-Cu-O Superconductors

Y-Ba-Cu-O orthorhombic superconducting phase direct crystallization from the 123 composition of liquid were realized by continuous wave CO2 laser using non equilibrium phase transformation of scanning laser melting solidification method. The transformation temperature 92 K of superconducting phase were measured. The characteristic peaks of YBa2Cu3O7 superconductors were shown by X-ray diffraction patterns. The sample of magnetization loop at 77 K and structure change were given.     

Laser Melting Solidification Process of Y BaCu O Superconductors

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Electrical assisted laser floating zone (EALFZ) growth of 2212-BSCCO superconducting fibres

The new electrical assisted laser floating zone (EALFZ) technique was used to grow superconducting fibres of Bi₂Sr₂CaCu₂O₈ (2212-BSCCO). The application of an electrical current through the crystallization interface proved to advantageously modify the phase nature and texture of 2212-BSCCO polycrystalline fibres compared to conventionally laser floating zone (LFZ) grown ones. The current application during the growth induces a selective and more intense ionic migration along the fibre axis. As a result, an increase in superconducting phase fraction and a decrease of residual melt were observed together with grain alignment intensification. The main outcome in the superconducting properties is the improvement of the critical current density at 77 K, from 1.2 × 10³ A/cm², in the LFZ fibres, to 2.8 × 10³ A/cm², in the EALFZ processed ones.     

Heat transfer and diffusion-controlled kinetics of liquid–solid phase in titanium matrix composite during selective laser melting

This study describes a self-consistent theoretical model of simulating diffusion-controlled kinetics on the liquid–solid phase boundary during high-speed solidification in the melt pool after the selective laser melting (SLM) process for titanium matrix composite based on Ti–TiC system. The model includes the heat transfer equation to estimate the temperature distribution in the melt pool and during crystallization process for some deposited layers. The temperature field is used in a micro region next to solid–liquid boundary, where solute micro segregation and dendrite growth are calculated by special approach based on transient liquid phase bonding. The effect of the SLM process parameters (laser power, scanning velocity, layer thickness and substrate size) on the microstructure solidification is being discussed.     

Solidification velocity in liquid silicon during excimer laser crystallization

Excimer laser crystallization (ELC) is commonly employed to fabricate low-temperature polycrystalline silicon. A time-resolved in-situ optical system with nanosecond response time is developed to monitor and record the phase transformation process during ELC. The average solidification velocity of liquid silicon (liquid Si) is investigated from the optical spectra recorded by a fast oscilloscope. It is found that the average solidification velocities of liquid Si in the partial-melting and complete-melting regimes are fundamentally different. In the partial-melting regime, the average solidification velocity decreases with increasing excimer laser energy density; while in the complete-melting regime, it increases abruptly due to the presence of deeply supercooled liquid Si.     

Phase and structural transformations in a molecular dynamics model of iron under ultrafast heating and cooling

It is shown that a system of classical particles considered in a molecular dynamics model with Pak-Doyama pairwise interatomic potential adequately describes not only the various structural states of iron (melt, bcc crystal, metal glass) but also the complex self-organization processes occurring in first-and second-order phase transitions (crystallization and vitrification, respectively). When the temperature is varied at a constant rate of 6.6×10¹¹ K/s, crystallization sets in from both the amorphous and the liquid state; at a rate of 1.9×10¹² K/s, crystallization is observed only in the amorphous state; and when heated at a rate of 4.4×10¹² K/s, the model amorphous iron transfers to the liquid state without crystallization. The energy of homogeneous formation of a crystal nucleus in the bulk of the amorphous phase of iron is calculated to be ～0.71 eV under the assumption that there is a spectrum of activation energies.