基于纳米硅结构的氮化硅基发光器件电致发光特性研究

利用等离子体增强化学气相沉积法制备了镶嵌于氮化硅的高密度纳米硅薄膜,并以此作为发光有源层构建基于p-Si/氮化硅基发光层/AZO结构发光二极管,在室温下观察到了电致可见发光.在此基础上,在器件p-Si空穴注入层与氮化硅基发光层之间加入纳米硅薄层作为空穴阻挡层,研究器件电致发光性质,实验结果表明器件的发光强度显著增强,并且发光效率较无纳米硅阻挡层的发光器件提高了80%以上.     

基于Si-rich SiNx/N-rich SiNy多层膜结构的量子点构筑及发光特性

利用等离子体增强化学气相沉积法制备Si-rich SiN_x/N-rich SiN_y多层膜,分别使用热退火和激光辐照技术对多层膜进行退火,以构筑三维限制、尺寸可控、有序的硅纳米晶.实验结果表明,经退火后,纳米硅晶粒在Si-rich SiN_x子层内形成,其尺寸可由Si-rich SiN_x子层厚度调控.实验还发现,激光辐照技术相比于热退火能更有效地改善多层膜的微结构,提高多层膜的晶化率,以激光技术诱导晶化的Si-rich SiN_x/N-rich SiN_y多层膜作为有源层构建电致发光器件,在室温下观察到了增强的电致可见发光,并且发光效率较退火前提高了40%以上. 关键词： 氮化硅 多层膜 限制结晶 纳米晶硅     

发光纳米硅/二氧化硅多层膜的特性与氢气氛退火的影响

利用等离子体增强化学气相沉积法制备了氢化非晶硅/二氧化硅多层膜，通过两步热退火的方法获得了尺寸可控的纳米硅/二氧化硅多层结构，晶粒尺寸约为4nm，在室温下观察到了较强的光致可见发光，其发光峰位于750nm.在此基础上，发现合适的氢气氛退火能有效地提高材料的发光强度.电子顺磁共振实验表明氢气氛退火有效地降低了纳米硅中的非辐射复合中心而导致发光效率的提高.     

脉冲激光晶化超薄非晶硅膜的分子动力学研究

利用准分子脉冲激光晶化非晶硅薄膜是制备高密度尺寸可控的硅基纳米结构的有效方法之一.本文将脉冲激光对非晶硅超薄膜的影响处理为热传导问题,采用了基于Tersoff势函数的分子动力学方法模拟了在非晶氮化硅衬底上2.7 nm超薄非晶硅膜的脉冲激光晶化过程.研究了不同激光能量对非晶硅薄膜晶化形成纳米硅的影响,发现在合适的激光能量窗口下,可以获得高密度尺寸可控的纳米硅薄膜,进而模拟了在此能量作用下非晶硅膜中成核与生长的机理与微观过程,并对晶化所获得的纳米硅薄膜的微结构进行了分析. 关键词： 非晶硅 分子动力学 脉冲激光晶化     

激光晶化形成纳米硅材料的场电子发射性质研究

利用KrF准分子激光退火超薄非晶硅膜,并结合热退火技术制备了单层纳米硅薄膜并研究了薄膜的场电子发射性质.在晶化形成的纳米硅薄膜中可以观测到稳定的场电子发射现象,其开启电场从原始淀积的非晶硅薄膜的17V/μm降低到8.5V/μm,而场发射电流密度可以达到0.1mA/cm².激光晶化后形成的纳米硅材料的场电子发射特性的改善可以从薄膜表面形貌的改变以及高密度纳米硅的形成所导致的内部电场增强作用来解释. 关键词： 纳米硅 场发射 激光晶化     

富硅a-SiOxNy：H薄膜的电致发光特性

采用甚高频等离子体增强化学气相沉积方法制备富硅氮氧化硅(a-SiO_0.35N_0.59:H)薄膜,以这层薄膜作为有源层构建发光二极管。实验结果表明器件在室温下可观测到强的电致红光发射,发光峰在715 nm附近,与其光致发光峰位一致。电致发光谱测量还表明器件开启电压为8 V,器件的电致发光强度随注入电流的增大呈线性递增关系。电流-电压特性分析表明器件的载流子输运机制以Pool-Frenkel(P-F)发射模型为主。结合发光有源层的微结构分析,初步认为电致红光发射来自于电子和空穴通过有源层的带尾态的辐射复合。     

硅纳米晶的椭圆偏振光谱研究

硅纳米晶量子点是硅发光研究领域最有潜力、最重要的一个研究方向。用热蒸发法在硅片上生长了富含硅纳米晶体的SiO2薄膜,观测到嵌埋于SiO2薄膜中硅纳米晶的较强光致发光谱;室温下在可见光区对该薄膜进行了椭圆偏振光谱测量研究。用有效介质近似(EMA)模型结合洛伦兹色散模型对椭偏参数进行了拟合,得到直径分别约为3 nm和5 nm大小的硅纳米晶在约300~830 nm光谱区的光学常数值。这些数据在硅基微纳光子学器件的研究中具有一定的参考价值。     

PECVD纳米晶粒硅薄膜的可见电致发光

在用等离子体增强化学汽相淀积的嵌有纳米晶粒硅薄膜中观测到电致发光．发光谱处在500—800nm之间，它有两个分别位于630—680nm和730nm附近的峰，两个峰的强度与薄膜的电导率有密切关系．根据这种材料的结构特性对载流子的传导通道进行了讨论，并且对发光机制进行了初步解释 关键词：     

基于Si-rich SiNx/N-rich SiNy多层膜结构电致发光特性研究

利用等离子体增强化学气相沉积法制备了富硅氮化硅/富氮氮化硅多层膜,并以此氮化硅基多层膜作为有源层构建电致发光器件,在室温下观察到了较强的电致可见发光.在此基础上,研究多层膜结构中作为势垒层的富氮氮化硅层对器件电致发光性质的影响,实验结果表明通过改变势垒层的Si/N组分,调制其势垒高度,器件的电致发光效率可得到显著地提高. 关键词： 电致发光 多层膜 氮化硅     

氮化硅介质中双层纳米硅薄膜的两级电荷存储

研究镶嵌在超薄非晶氮化硅(a-SiN_x)层之间的双层纳米硅(nc-Si)的电荷存储现象.利用等离子体增强化学气相淀积(PECVD)技术在硅衬底上制备a-SiN_x/a-Si/a-SiN_x/a-Si/a-SiN_x多层薄膜结构.采用常规热退火方法使非晶硅(a-Si)层晶化，形成包含双层nc-Si的金属-氮化物-半导体(MIS)结构.通过电容电压(C-V)特性测量，观测到该结构中由于电荷存储引起的C-V回滞现象，并在室温下成功观察到载流子基于Fowler-Nordheim(F-N)隧穿注入到第一层、第二层nc-Si的两级电荷存储状态.结合电流电压(I-V)特性的测量，对电荷存储的机理进行了深入分析. 关键词： 纳米硅 氮化硅 电容电压法 电流电压法     

Amorphous Si/insulator multilayers grown by vacuum deposition and electron cyclotron resonance plasma treatment

a-Si/insulator multilayers have been deposited on (0 0 1) Si by electron gun Si evaporation and periodic electron cyclotron resonance plasma oxidation or nitridation. Exposure to an O or N plasma resulted in the formation of a thin SiO₂ and SiN_x layer whose thickness was self-limited and controlled by process parameters. For thin-layer (2 nm) Si/SiO₂ and Si/SiN_x multilayers no visible photoluminescence (PL) was observed in most samples, although all exhibited weak “blue” PL. For the nitride multilayers, annealing at 750°C or 850°C induced visible PL that varied in peak energy with Si layer thickness. Depth profiling of a-Si caps on thin insulating layers revealed no detectable contamination for the SiN_x layers, but substantial O contamination for the SiO₂ films.     

nc-Si/SiO2多层膜的制备及蓝光发射

在等离子体增强化学气相淀积(PECVD)系统中，采用a-Si∶H层淀积与原位等离子体氧化相结合的逐层生长的方法成功制备出a-Si∶H/SiO2多层膜 (ML)；利用限制性结晶原理通过两步退火处理使a-Si∶H层晶化获得尺寸可控的nc-Si/SiO2 ML，并观察到室温下的蓝光发射；结合Raman散射和剖面透射电子显微镜技术分析了nc-Si/SiO2 ML的结构特性；通过对晶化样品光致发光谱和紫外-可见光吸收谱的研究，探讨了蓝光发射的起源. 关键词： 纳米硅多层膜 等离子体氧化 蓝光发射 热退火     

原位等离子体逐层氧化a-Si:H/SiO2多层膜的光致发光研究

采用在等离子体增强化学汽相沉积系统中沉积a-Si:H和原位等离子体逐层氧化的方法制备a-Si:H/SiO2多层膜.改变a-Si:H层的厚度，首次在室温下观察到来自a-Si:H/SiO2多层膜较强的蓝色光致发光和从465到435nm的蓝移.x射线能谱证明，SiO2层是化学配比的SiO2；C-V特性表明，a-Si:H/SiO2界面得到了很好的钝化；透射电子显微镜表明，样品形成了界面陡峭的多层结构.结合光吸收谱和光致发光谱的研究，对其发光机理进行了讨论.用一维量子限制模型对光致发光峰随着a-Si:H层厚度的减小 关键词： a-Si:H/SiO2多层膜 光致发光     

Comparative investigation of unipolar resistance switching effect of Pt/Mg0.6Zn0.4O/Pt devices with different electrode patterns for nonvolatile memory application

In this report, we study crystallization and Raman spectral and transmission electron microscopy (TEM) changes in amorphous and nanocrystalline Si. Micro-Raman spectra combined with TEM show that considerable crystallization occurs in a-Si:H and a-Si(Al) (the structure of aluminum-diffused amorphous Si/Al/c-Si), but no additional crystallization was observed for nc-Si:H, after the exposure to a laser or accelerating electrons. Meanwhile, moving toward lower or higher energy for a-Si:H and nc-Si:H, by contrast, the Raman shift appeared for a-Si(Al) as if it were for single-crystalline Si, in which it remained constant at one energy, as the laser intensity increased or decreased.     

Effects of hydrogen plasma annealing on the luminescence from a-Si:H/SiO2 and nc-Si/SiO2 multilayers

Effects of post-hydrogen plasma annealing (HPA) on a-Si:H/SiO₂ and nc-Si/SiO₂ multilayers have been investigated and compared. It is found that photoluminescence (PL) from hydrogen-passivated samples was improved due to the reduction of non-radiative recombination defects. Some interesting difference is that during HPA, atomic hydrogen can directly passivate defects of a-Si:H/SiO₂, which results in the reappearance of luminescence band at 760 nm, while for nc-Si/SiO₂, hydrogen passivation requires additional thermal annealing after nc-Si/SiO₂ multilayer was treated by HPA. It is indicated that higher atomic mobility is needed to passivate defects at nc-Si/SiO₂ interface compared with a-Si:H/SiO₂ interface.     

Visible photoluminescence from a-Si : H/SiO2 superlattices fabricated by UHV evaporation

Hydrogenated amorphous-Si/SiO₂ (a-Si:H/SiO₂) superlattices with different a-Si : H thickness in the range of a few nanometers have been fabricated by ultra high vacuum evaporator (UHV evaporator). The photoluminescence (PL) of our superlattices is observed in the visible spectral region and the peak energy shifts to higher energy as the a-Si : H layer thickness decreases. The temperature dependence of the PL spectra reveals four sub-bands by fitting. Bands at 2.2, 1.9, 1.65 and 1.45 eV are detected and are attributed to E′δ centers, nonbridging-oxygen–hole centers (NBOHC), Si/SiO₂ interface and a-Si : H layer, respectively. We explain the overall blueshift of the PL spectra by the modification of the contribution of these sub-bands.     

Thermal annealing of a-Si:H/a-SiNx:H multilayers

The crystallinity of Si/SiN_x multilayers annealed by a rapid thermal process and furnace annealing is investigated by a Raman-scattering technique and transmission electron microscopy. It is found that the crystallization temperature varies from 900 °C to 1000 °C when the thickness of a-Si:H decreases from 4.0 nm to 2.0 nm. Raman measurements imply that the high crystallization temperature for the a-Si:H sublayers originates from the confinement modulated by the interfaces between a-Si:H and a-SiN_x:H. In addition to the annealing temperature, the thermal process also plays an important role in crystallization of a-Si sublayers. The a-Si:H sublayers thinner than 4.0 nm can not be crystallized by furnace annealing for 30 min, even when the annealing temperature is as high as 1000 °C. In contrast, rapid thermal annealing is advantageous for nucleation and crystallization. The origin of process-dependent crystallization in constrained a-Si:H is briefly discussed. Received: 11 April 2001 / Accepted: 20 June 2001 / Published online: 30 August 2001     

Pseudo nanocrystal silicon induced .luminescence enhancement in a-Si/SiO2 multilayers

Enhanced photoluminescence （PL） at room temperature from thermally annealed a-Si：H/SiO2 multilayers is observed through the step-by-step thermal post-treatment. The correlation between the PL and the crystallization process is studied using temperature-dependent PL, Raman, cross section high-resolution transmission electron microscopy （XHRTEM） and x-ray diffraction （XRD） techniques. An intensified PL band around 820 nm is discovered from the sample annealed near the crystallization onset temperature, which is composed of two peaks centred at 773 nm and 863 nm, respectively. It is found that the PL band centred at 863 nm is related to the pseudo nanocrystal （p-nc-Si） silicon, and the PL band centred at 773 nm is attributed to Si = O bonds stabilized in the p-nc-Si surface.     

The origin of blue photoluminescence from nc-Si/SiO2 multilayers

Intensive blue photoluminescence (PL) was observed at room temperature from the nanocrystalline-Si/SiO$_{2}$ (nc-Si/SiO$_{2})$ multilayers (MLs) obtained by thermal annealing of SiO/SiO$_{2}$\,MLs for the first time. By controlling the size of nc-Si formed in SiO sublayer from 3.5 to 1.5 nm, the PL peak blueshifts from 457 to 411 nm. Combining the analysis of TEM, Raman and absorption measurement, this paper attributes the blue PL to multiple luminescent centres at the interface of nc-Si and SiO$_{2}$.