含纳米硅和纳米锗的氧化硅薄膜光致发光的比较研究

分别以硅-二氧化硅和锗-二氧化硅复合靶作为溅射靶,采用磁控溅射技术在p型硅衬底上淀积了含纳米硅的氧化硅薄膜和含纳米锗的氧化硅薄膜.各样品分别在氮气氛中经过300至1100℃不同温度的退火处理.使用高分辨透射电子显微镜可以观察到经900和1100℃退火的含纳米硅的氧化硅薄膜中的纳米硅粒,和经900和1100℃退火的含纳米锗的氧化硅薄膜中的纳米锗粒.经过不同温度退火处理的含纳米硅的氧化硅和含纳米锗的氧化硅薄膜的光致发光谱均具有相似的峰型,且它们的发光峰位均位于580nm(2.1eV)附近.可以认为含纳米硅的氧化硅和含纳米锗的氧化硅薄膜的光发射主要来自于SiO₂层中发光中心上的复合发光,对实验结果进行了合理的解释     

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     

锗/多孔硅和锗/氧化硅薄膜光致发光的比较研究

采用磁控溅射技术,以锗为溅射靶,在多孔硅上沉积锗薄膜,沉积时间分别为4,8和12 min,及以锗-二氧化硅复合靶为溅射靶,在n型硅衬底上沉积了含纳米锗颗粒的氧化硅薄膜,锗与总靶的面积比分别为5%,15%,30%.各样品在氮气氛中分别经过300,600及900℃退火30 min.对锗/多孔硅和锗/氧化硅薄膜进行了光致发光谱的对比研究,用红外吸收谱分析了锗/多孔硅的薄膜结构.实验结果显示,锗/多孔硅薄膜的发光峰位于517 nm附近,沉积时间对发光峰的强度有显著影响,锗层越厚峰强越弱.锗/氧化硅薄膜的发光峰位于580 nm附近,锗与总靶的面积比对发光峰的强度影响较大,锗/氧化硅薄膜中的锗含量越高峰强越弱.不同的退火温度对样品的发光峰强及峰位均没有明显影响.可以认为锗/多孔硅的发光峰是由多孔硅与孔间隙中的锗纳米晶粒两者界面的锗相关缺陷引起的,而锗/氧化硅的发光峰来自于二氧化硅的发光中心.     

含纳米硅和纳米锗的氧化硅薄膜 光致发光的比较研究

分别以硅-二氧化硅和锗-二氧化硅复合靶作为溅射靶,采用磁控溅射技术在p型硅衬底上淀积了含纳米硅的氧化硅薄膜和含纳米锗的氧化硅薄膜.各样品分别在氮气氛中经过300至1100℃不同温度的退火处理.使用高分辨透射电子显微镜可以观察到经900和1100℃退火的含纳米硅的氧化硅薄膜中的纳米硅粒,和经900和1100℃退火的含纳米锗的氧化硅薄膜中的纳米锗粒.经过不同温度退火处理的含纳米硅的氧化硅和含纳米锗的氧化硅薄膜的光致发光谱均具有相似的峰型,且它们的发光峰位均位于580nm(2.1eV)附近.可以认为含纳米硅的氧化硅和含纳米锗的氧化硅薄膜的光发射主要来自于SiO     

含纳米锗粒二氧化硅薄膜的光致发光研究

以锗-二氧化硅(GSO)复合靶作为溅射靶，改变靶上锗与总靶面积比为0%，5%和10%，用射频磁控溅射方法在p型硅衬底上淀积了含锗量不同的三种二氧化硅薄膜.各样品分别在氮气氛中经过300至900℃不同温度的退火处理.通过对样品所作Raman散射光谱的分析，发现随着锗在溅射靶中面积比的增加，所制备的氧化硅薄膜中纳米锗粒的平均尺寸在增大.确定出随着退火温度由600℃升高到900℃，GSO(5%)样品中纳米锗粒的平均直径由5.4nm增至9.5nm.含纳米锗粒大小不同的二氧化硅薄膜的光致发光谱中都存在位于2.1eV     

掺铒Si/Al2O3多层结构中结晶形态对1.54 μm发光的影响

利用脉冲激光沉积的方法制备掺铒 Si/Al₂O₃多层结构薄膜,获得了由纳米结构的Si作为感光剂增强的Er³⁺在1.54 μm高效发光.利用拉曼散射、高分辨透射电镜和光致发光测量研究了在不同退火温度下（600—1000 ℃）纳米结构Si层的结晶形态变化,及对Er³⁺在1.54 μm的发光的影响特征.研究发现最佳发光是在退火温度600—700 ℃.在这个条件下纳米Si的尺寸和密度,Si和Er的作用距离以及Er^{3+ 关键词： 铒 纳米硅 能量转移 氧化铝}     

纳米Si/SiO2多层膜的结构表征及发光特性

采用等离子体化学气相沉积系统生长非晶硅薄膜并用原位等离子体氧化的方法制备出具有不同子层厚度的非晶Si/SiO₂多层膜,然后利用限制性晶化原理使非晶硅层晶化生成纳米硅。利用Raman、TEM等手段对薄膜结构进行了系统表征,在室温下观测到了光致发光信号,其发光峰峰位在750nm附近。进而在样品上下表面蒸镀电极,构建了电致发光原型器件并观测到了室温下的电致发光谱,开启电压约为6V,有两个明显的发光带,分别位于在650nm和520nm处。初步探讨了纳米硅及纳米硅/二氧化硅界面态对发光特性的影响。     

内电场对纳米硅光致发光谱的影响

从量子限制发光中心模型出发，计算了纳米硅的光致发光（PL）特征与发光中心间的关系. 研究发现，纳米硅与发光中心间的内电场对载流子复合率及峰位振荡有着十分重要的影响. 在2—5 nm的尺寸范围内，纳米硅发光中心上的载流子复合概率远大于内部复合概率，仅需考虑发光中心上的载流子复合发光. 还发现发光中心与纳米硅粒子间的内电场对于纳米硅的发光峰位振荡有着显著的影响.发光中心与纳米硅粒子间的内电场的存在会显著减小纳米硅粒子的内部发光效率以及外部相应发光中心上的发光强度，使得纳米硅PL谱的峰位随纳米晶粒尺寸变化而发生 关键词： 内电场 纳米硅 光致发光 量子限制发光中心     

SiOx∶H(0＜x＜2)薄膜光致发光的退火行为研究

采用退火后处理的方法，使SiO_x∶H(0＜x＜2)形成纳米硅与二氧化硅的镶嵌结构.利用红外透射谱、Raman谱和光致发光谱，系统地研究了不同退火温度对薄膜微结构及室温光致发光谱的影响.发现发光谱均由两个Gauss线组成，其中主峰随着退火温度的升高而红移，而位于835nm的伴峰不变.指出退火前在720—610nm的波长范围内强的主峰可能来源于膜中的非晶硅原子团，随退火温度的升高主峰的红移是由于非晶硅原子团的长大.而伴峰可能来自硅过剩或氧欠缺引入的某种发光缺陷.1170℃退火后在850n 关键词：     

溅射气氛和退火方式对硅纳米晶的形成及发光特性的影响

利用磁控溅射技术溅射硅靶,通过调节溅射气氛在硅衬底上生长了SiO/SiO₂超晶格,热退火处理后超晶格中的SiO发生相分离得到硅纳米晶。通过比较不同退火方式对于硅纳米晶的形成的影响发现,管式炉退火处理的样品给出非常强的室温光致发光,其发光峰的峰位随着硅纳米晶尺寸的增大而红移,且管式炉退火比快速热退火更有利于硅纳米晶的形成。     

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.     

Correlation between Light Emissions from Amorphous-Si：H/SiO2 and nc-Si/SiO2 Multilayers

We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.     

Characterization of Si nanocrystals into SiO2 matrix

Silicon nanocrystals (nc-Si) have gained great interest due to their excellent optical and electronic properties and their applications in optoelectronics. The aim of this work is the study of growth mechanism of nc-Si into a-SiO₂ matrix from SiO/SiO₂ multilayer annealing, using non-destructive and destructive techniques. The multilayer were grown by e-beam evaporation from SiO and SiO₂ materials and annealing at temperatures up to 1100 °C in N₂ atmosphere. X-rays reflectivity (XRR) and high resolution transmission electron microscopy (HRTEM) were used for the structural characterization and spectroscopic ellipsometry in IR (FTIRSE) energy region for the study of the bonding structure. The ellipsometric results gave a clear evidence of the formation of an a-SiO₂ matrix after the annealing process. The XRR data showed that the density is being increased in the range from 25 to 1100 °C. Finally, the HRTEM characterization proved the formation of nc-Si. Using the above results, we describe the growth mechanism of nc-Si into SiO₂ matrix under N₂ atmosphere.     

Investigation on preparation and physical properties of nanocrystalline Si/SiO2 superlattices for Si-based light-emitting devices

Structures containing silicon nanocrystals (nc-Si) are very promising for Si-based light-emitting devices. Using a technology compatible with that of silicon, a broader wavelength range of the emitted photoluminescence (PL) was obtained with nc-Si/SiO₂ multilayer structures. The main characteristic of these structures is that both layers are light emitters. In this study we report results on a series of nc-Si/SiO₂ multilayer periods deposited on 200 nm thermal oxide SiO₂/Si substrate. Each period contains around 10 nm silicon thin films obtained by low-pressure chemical vapour deposition at T=625°C and 100 nmSiO₂ obtained by atmospheric pressure chemical vapour deposition T=400°C. Optical and microstructural properties of the multilayer structures have been studied by spectroscopic ellipsometry (using the Bruggemann effective medium approximation model for multilayer and multicomponent films), FTIR and UV–visible reflectance spectroscopy. IR spectroscopy revealed the presence of SiO_x structural entities in each nc-Si/SiO₂ interface. Investigation of the PL spectra (using continuous wave-CW 325 nm and pulsed 266 nm laser excitation) has shown several peaks at 1.7, 2, 2.3, 2.7, 3.2 and 3.7 eV, associated with the PL centres in SiO₂, nc-Si and Si–SiO₂ interface. Their contribution to the PL spectra depends on the number of layers in the stack.     

Hydrogenation effect on enhancement of photoluminescence of Er and Si nanocrystallites in Er-doped SiO2 synthesized by laser ablation

Significant enhancement of photoluminescence (PL) was attained for Er ions and Si nanocrystallites (nc-Si) in SiO₂ films by two kinds of hydrogenation, using H₂ molecules or H atoms. Er-doped SiO₂ films containing Er impurities and a high density of nc-Si were fabricated by laser ablation of Er films deposited on Si substrate in an O₂ gas atmosphere, followed by annealing at high temperatures in flowing Ar gas. Hydrogenation at 300–500 °C was found to effectively increase the PL intensity of Er ions as well as that of nc-Si. In particular, the hydrogen atom treatment dramatically shortens the hydrogenation time for the enhancement of Er PL compared to the hydrogen molecule treatment. Spectra of electron spin resonance showed a decrease in residual defects, namely, P_b-type defects located at the interfaces between nc-Si and SiO₂ by hydrogenation. These results clearly show the effectiveness of hydrogen passivation for Si nanostructures; i.e., the increase in the Er PL and nc-Si PL due to hydrogen passivation of the nonradiative recombination centers located at the interfaces between nc-Si and SiO₂. PACS 78.67.Bf; 71.20.Eh; 76.30.Mi; 81.15.Fg     

a-Si ∶H/SiO2多量子阱材料制备及其光学性能和微结构研究

利用等离子体增强化学气相沉积技术制备了a-Si ∶H/SiO₂多量子阱结构材料.对a-Si ∶H/SiO₂多量子阱样品分别进行了3种不同的热处理,其中样品经1100 ℃高温退火可获得尺寸可控的nc-Si:H/SiO₂量子点超晶格结构,其尺寸与非晶硅子层厚度相当.比较了a-Si ∶H/SiO₂多量子阱材料与相同制备工艺条件下a-Si ∶H材料的吸收系数,在紫外/可见短波段前者的吸收系数明显增大,光学吸收边蓝移,说明该材料 关键词： 多量子阱 量子限制效应 光学吸收 能带结构     

Structural and optical properties of Si/SiO2 multi-quantum wells

Structural and optical properties of Si/SiO₂ multi-quantum wells (MQW) were investigated by means of Raman scattering and photoluminescence (PL) spectroscopy. The MQW structures were fabricated on a quartz substrate by remote plasma enhanced chemical vapour deposition (RPECVD) of alternating amorphous Si and SiO₂ layers. After layer deposition the samples were subjected to heat treatments, i.e. rapid thermal annealing (RTA) and furnace annealing. Distinct PL signatures of confined carriers evidenced formation of Si-nanocrystals (nc-Si) in annealed samples. Analyses of Raman spectra also show presence of nc-Si phase along with amorphous-Si (a-Si) phase in the samples. The strong influence of the annealing parameters on the formation of nc-Si phase suggests broad possibilities in engineering MQW with various optical properties. Interestingly, conversion of the a-Si phase to the nc-Si phase saturates after certain time of furnace annealing. On the other hand, thinner Si layers showed a disproportionately lower crystalline volume fraction. From the obtained results we could assume that an interface strain prevents full crystallization of the Si layers and that the strain is larger for thinner Si layers. The anomalous dependence of nc-Si Raman scattering peak position on deposited layer thickness observed in our experiments also supports the above assumption.     

Ar irradiation of Si nanocrystal-doped SiO2: Evolution of photoluminescence

We report the evolution of photoluminescence (PL) of Si nanocrystals (nc-Si) embedded in a matrix of SiO₂ during Ar⁺ ion bombardment. The integrated intensity of nc-Si PL falls down drastically before the Ar⁺ ion fluence of 10¹⁵ ions cm⁻², and then decreases slowly with the increasing ion fluence. At the meantime, the PL peak position blueshifts steadily before the fluence of 10¹⁵ ions cm⁻², and then changes in an oscillatory manner. Also it is found that the nc-Si PL of the Ar⁺-irradiated sample can be partly recovered after annealing at 800 °C in nitrogen, but can be almost totally recovered after annealing in oxygen. The results confirm that the ion irradiation-induced defects are made up of oxygen vacancies, which absorb light strongly. The oscillatory peak shift of nc-Si can be related to a size-distance distribution of nc-Si in SiO₂.     

a-Si∶O∶H薄膜微结构及其高温退火行为研究

以微区Raman散射、X射线光电子能谱和红外吸收对等离子体增强化学气相沉积(PECVD)法制备的氢化非晶硅氧(a-Si∶O∶H)薄膜微结构及其退火行为进行了细致研究.结果表明a-Si∶O∶H薄膜具有明显的相分离结构,富Si相镶嵌于富O相之中,其中富Si相为非氢化四面体结构形式的非晶硅(a-Si),富O相为Si,O,H三种原子随机键合形成的SiO_x∶H(x≈1.35).经1150℃高温退火,薄膜中的H全部释出;SiO_x∶H(x≈1.35)介质在析出部分Si原子的同