非晶SiOx:C薄膜的发光特性研究

采用双离子束溅射法制备了SiOx:C非晶薄膜,在室温下可观察到薄膜样品有强的420nm(紫光)、470nm(蓝绿光)的光致发光(PL).分别对样品在不同温度下退火后,PL测试显示随着退火温度的升高420nm处的峰带逐渐增强变为强的发光峰;470nm处的发光峰位来自于硅基薄膜中富硅引起的中性氧空位缺陷(O3≡Si-Si≡O3),是由与氧原子配位的二价硅的单态-单态之间的跃迁所致;420nm范围的峰带可能来自于薄膜中由C单质、以及Si、O、C三者组成的一个复杂结构.     

双离子束溅射法制备SiOxNy薄膜的结构与发光

本文采用双离子束溅射沉积法制备了SiOxNy复合薄膜,XRD、TEM测试表明薄膜呈非晶态,FTIR及XPS测试表明薄膜成分由Si、O、N组成,在室温下可观察到样品有400 nm（紫光）、470 nm（蓝光）的光致发光.根据测试分析研究了SiOxNy薄膜的可能的发光机理：470 nm处发光峰为来自于硅基薄膜中中性氧空位缺陷（O3≡Si-Si≡O3）,是由于氧原子配位的二价硅的单态-单态之间的跃迁所致,其发光强度随退火温度的升高而变化,800℃时最大,高于800℃时慢慢减弱;400 nm发光峰的发射与薄膜中的Si、O、N所形成的结构有关,它可能来自于Si、O、N结构所形成的发光中心,该峰位的强度随退火温度的升高而增强.     

退火对两种硅基薄膜的结构及发光影响

采用双离子束共溅射沉积方法制备了两种复合硅基薄膜SiOxCy和SiOxNy薄膜,对两种薄膜进行后退火处理,并分别对样品进行PL、FTIR、XPS谱测试分析,比较退火前后的发光及结构的变化。两种样品的光致发光测试谱(PL)表明:退火前后都有两个发光峰位-都存在470nm的发光峰位,它来自于硅基薄膜中中性氧空位缺陷(O3≡Si-Si≡O3),是由于氧原子配位的二价硅的单态-单态之间的跃迁所致,其发光强度随退火温度的升高而变化。进一步的FTIR和XPS的测试谱表明另外一个发光峰位420nm(SiOxCy薄膜)和400nm(SiOxNy薄膜)分别来自于掺杂杂质(C和N)与硅基薄膜中的Si、O组成的复合结构。而两种样品经过退火处理后掺杂所引起的发光峰位强度随退火温度的升高而增强,说明退火温度的升高有利于发光机制的形成。     

SiOx薄膜的制备及发光特性研究

本论文采用双离子束溅射沉积技术制备了非晶的SiOx薄膜，XPS的测试表明Si是以单原子或低价氧化物的形态存在于薄膜内；在波长为240nm紫外光的激发下，室温及1000℃退火后SiOx薄膜的PL谱图显示样品中存在峰位分别处于320nm，410nm，560nm，630nm四个相互分离的峰，其发光机制分别为来自中性氧空位缺陷（≡Si—O—O—Si≡）、双配位硅悬挂键（O-Si-O）、非桥氧空位中心以及其他缺陷所形成的发光中心。     

a-SiOx∶C薄膜的结构与发光特性研究

采用双离子束共溅射法制备了SiOx∶C薄膜.对样品的XRD和TEM测试结果表明薄膜为非晶结构;PL谱图显示有两个发光峰分别位于420 nm(紫光)、470 nm(蓝绿光)处;470 nm处的发光峰位来自于硅基薄膜中富硅引起的中性氧空位缺陷(O3Si-SiO3),是由与氧原子配位的二价硅的单态以及三态-单态之间的跃迁所致,而与掺碳无关.进一步的XPS测试分析表明,420 nm处的PL峰位可能来自于Si、C、O三者组成的复杂的结构.     

掺Er-Al2O3薄膜发光特性的研究

通过离子束辅助沉积(IBAD)在热氧化SiO2上沉积Al2O3薄膜,在120keV下注入5×10115cm-2Er离子,Ar气氛下773～1273K退火1h.低温下测试PL谱线,随退火温度升高,发光强度上升.973K退火下发光强度特别低,并观察到Si衬底的1140nm峰.光透射谱表明几乎在所有的测试范围内尤其在1530nm处973K退火样品的透射谱强度最强,波导损耗最低.1530nm发光强度随退火温度的变化跟发光强度的变化相反.说明Er离子在514.5nm泵谱吸收界面σ跟Al2O3的光吸收损耗有一定关系.     

退火对Fe/Al_2O_3纳米复合物微波吸收性能的影响

采用球磨法制备Fe/Al2O3纳米复合物,并在氩气保护下退火,研究了退火对Fe/Al2O3纳米复合物的微观结构、磁性和微波吸收性能的影响。结果表明,退火使样品的晶粒尺寸增大,缺陷减少,微观应力得到释放;同时,退火使Al2O3的缺陷发光峰强度明显减弱,398 nm和484 nm处的发光峰发生蓝移。厚度为7.7 mm的球磨样品,其反射损耗在15.5 GHz频率处达到最大值-11.4 dB。退火使样品的介电损耗和磁损耗均增大,电磁波吸收性能明显提高,厚度为6.4 mm时反射损耗在17 GHz频率处达到最大值-35.5 dB。     

退火对Cr3+离子掺杂Al2O3薄膜的结构及发光性能影响

用脉冲激光沉积技术在Si(100)基底上制备了纯Al2O3、掺杂浓度为0.3%、1%(质量分数)的Cr3+∶Al2O3薄膜。制备态的薄膜为立方γ-Al2O3结构,经800℃真空条件下退火1h样品的结晶度有所提高,呈现α-Al2O3相与γ-Al2O3相的衍射峰。薄膜基本保持了靶材中原有各元素成分比例,平均粒径为250nm,形貌为条形。与Al2O3粉体相比,制备态薄膜在386nm处的发光峰强度明显提高。这可归因于薄膜中氧空位的增加使双氧空位吸收电子所产生的F2+色心浓度提高。薄膜经真空退火后在332、398nm附近的发光峰强度明显增强,这是由于薄膜中氧空位的增加提高了F+、F色心浓度。与此同时,制备态薄膜在386nm附近发光峰经退火后由386nm蓝移至381nm,可归因于退火后制备态薄膜的内应力得到了释放。1%(质量分数)Cr3+掺杂薄膜在646、694nm出现Cr3+离子由4 T2能级跃迁至4 A2能级及由E-能级跃迁至4 A2能级产生的荧光发光峰。     

Nb金属氧化物非晶态纳米薄膜的制备及可见光区的光致发光现象

在较低的温度下,通过热氧化法在Si单晶基底上合成氧化铌(NbO_x)非晶结构纳米薄膜。样品的衍射谱为典型的漫散包,在450℃以下的退火样品都没有明显的晶化峰出现。SEM图片显示,薄膜是由一些准直阵列的椎形结构组成。在室温下对原始非晶膜以及退火处理过的样品作了PL谱分析,实验观测到:514nm激发光源下,样品在室温下可见光区出现红橙色发光,发光峰包较宽且很有特点。分峰拟合结果可明显看到发光峰包由630～715附近的两峰组成,通过性能检测发现,薄膜经低温段退火处理后在可见光区具有很好的光致发光,这一现象到目前为止尚少见报道。实验还研究了退火温度与发光强度的规律,初步研究表明,此光致发光机制与缺陷有关。     

SiC-SiO_2纳米复合薄膜的光致发光特性研究

利用射频 (RF) 共溅射的方法在n-Si(111)衬底上,以SiO_2为主靶,上面放置不同数量的Si片和石墨片,沉积出掺杂氧化物SiC复合薄膜,随后在不同温度下进行退火处理,并研究了其光致发光谱和光激发谱。不同C含量的样品在450nm和580nm附近均得到不同强度的发光峰,主要来自于Si、C注入后引起的基质成键变化而带来的氧空位缺陷和Si晶粒,对于C含量较高的样品在580nm处观察到黄光发射与C团簇有关。利用FTIR和XRD表征了复合膜的结构,UV—VIS分光光度计表征了复合膜的透射吸收特征。     

Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.     

[100]取向Al-Ti共掺杂ZnO薄膜的制备与光电性能研究

采用常压固相烧结法制备了Al-Ti共掺ZnO靶材, 采用射频磁控溅射技术及真空退火工艺, 在普通玻璃衬底上制备了具有[100]取向Al-Ti共掺杂ZnO薄膜(ZATO). 采用X射线衍射(XRD)、扫描电子显微镜(SEM)对ZATO薄膜的生长机理、显微结构、形貌进行了测试分析, 用四探针测试仪、紫外-可见分光光度计及荧光光谱仪对ZATO薄膜的光电性能进行了测试分析. 结果表明, ZATO薄膜经500℃保温3h退火后, 择优取向由(002)向(100)方向转变; 此时, 衍射谱上还观察到超点阵衍射线条. [100]取向ZATO薄膜的光学带隙从退火前的3.29降至2.86, 平均可见光透过率从90%降至70%, 表现为一般的透过性; 而电阻率则从1.89×10^-2Ω·cm降至1.25×10^-3Ω·cm, 呈现较好的导电性. 薄膜中均出现了380nm附近的带边发射(NBE)峰以及410、564nm的深能级发射峰, 且经500℃保温3h退火后, 这些峰的位置并未改变, 但峰强均明显减弱. 对上述实验机理进行了分析讨论.     

Localized CO2 laser annealing induced dehydrogenation/ablation and optical refinement of silicon-rich silicon dioxide film with embedded si nanocrystals

CO2 laser annealing induced effects of dehydrogenation, Si nanocrystal precipitation, ablation, and optical refinement in PECVD grown SiO1.25 film are investigated. Dehydrogenation shrinks SiO1.25 thickness by 40 nm after annealing at laser intensity (Plaser) of 4 kW/cm(2) for 1.4 ms. As Plaser increases to 6 kW/cm(2), the photoluminescence (PL) red-shifts to 806 nm due to the size enlargement of Si nanocrystals, while a reduced optical bandgap energy from 3.3 to 2.43 eV and an enlarged refractive index from 1.57 to 1.87 are also observed. Transmission electron microscopy analysis reveals that the randomly oriented Si nanocrystals exhibit an average diameter of 5.3 nm and a volume density of 1.9 x 10(18) cm(-3). CO2 Laser ablation initiates at intensity higher than 7 kW/cm(2), which introduces numerous structural defects with a strong PL at 410 nm. Such an ablation inevitably leads to a blue-shifted optical bandgap energy from 2.43 to 2.76 eV as Plaser enlarges from 6 to 12 kW/cm(2) are concluded.     

Ge-SiO2薄膜的结构及其发光特性的研究

采用射频磁控溅射技术制备了Ge-SiO2薄膜，在N2气氛下进行了不同温度的退火处理，分析了样品在室温下的光致发光（PL）特性，为探讨其发光机制，对薄膜的结构进行了表征，XRD、XPS、FTIR谱分析说明样品的发光特性与其结构相对应，394nmPL由GeO缺陷引起，580nmPL与Ge纳米晶粒和基质SiO2界面处的发光光中心相联系。     

Au／SiO2复合纳米颗粒膜及SiO2纳米线的制备

室温下用磁控溅射法在Si（111）衬底上生成Au／SiO2复合纳米颗粒膜,并分不同温度进行退火处理。1000℃退火时自组装生成空间分布均匀（直径约为70nm）的Au纳米点,从而用自组装生长方法制备了生长一维纳米材料的模板,然后,将Au催化剂模板在1100℃下退火处理,生成纳米线,SEM和TEM测试,制备的SiO2纳米线直径约为100nm,长度约为4μm,表面光滑,直且粗细均匀。     

Luminescence properties of spark-processed SiC

The photoluminescence (PL) properties of spark-processed SiC (sp-SiC) have been studied at various temperatures. Furthermore, scanning electron micrographs (SEM), X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy have been applied. The luminescence properties of sp-SiC are quite different from unspark-treated reference 6 H SiC. Specifically, the PL intensities of sp-SiC are at least two orders of magnitude larger than the reference SiC. Furthermore, the room temperature PL spectrum of sp-SiC exhibits two luminescence bands peaking at 3.18 eV, which are considerably blue shifted from SiC band gap of 2.9 and 2.43 eV. However, these two luminescence bands show an unusual red-shift of PL peak energies with decreasing temperature. Raman spectroscopy studies of sp-SiC display the emergence of a crystalline Si vibrational mode, whereas vibrational modes associated with 6H SiC are completely annihilated. XRD analysis exhibits the formation of polycrystalline Si after spark processing. Vibrational modes obtained from FTIR for sp-SiC are mainly composed of Si–O modes with some OH vibration. The results of low temperature PL studies, FTIR, XRD, XPS and Raman spectroscopy demonstrate that the luminescence properties of sp-SiC are similar to spark-processed Si.     

The structure and photoluminescence properties of ZnO/SiC multilayer film on Si substrate

ZnO/SiC multilayer film has been fabricated on a Si (111) substrate with a silicon carbide (SiC) buffer layer using the RF (radio frequency)-magnetron technique with targets of a ceramic polycrystalline zinc oxide (ZnO) and a composite target of pure C plate with attached Si chips on the surface. The as-deposited films were annealed at a temperature range of 600–1000°C under nitrogen atmosphere. The structure and photoluminescence (PL) properties of the samples were measured using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and PL spectrophotometry. By increasing the annealing temperature to 800°C, it is found that all the ZnO peaks have the strongest intensities, and the crystallinity of ZnO is more consistent on the SiC buffer layer. Further increase of the annealing temperature allows the ZnO and SiC layers to penetrate one another, which makes the interface between ZnO and SiC layer become more and more complicated, thus reduces the crystallinities of ZnO and SiC. The PL properties of a ZnO/SiC multilayer are investigated in detail. It is discovered that the PL intensities of these bands reach their maximum after being annealed at 800°C. The PL peaks shift with an increase in the annealing temperature, which is due to the ZnO and SiC layers penetrating reciprocally. This makes the interface more impacted and complicated, which induces band structure deformation resulting from lattice deformation.     

Spectroscopic analysis on metal-oxide-semiconductor light-emitting diodes with buried Si nanocrystals and nano-pyramids in SiO(x) film

The difference between the white and near-infrared electroluminescence of metal-oxide-semiconductor light-emitting diodes fabricated on 1,100 degrees C-annealed Si-rich SiO(x)/p-Si substrate with interfacial pyramidal Si dots (Si nano-pyramids) was characterized. By changing the substrate temperature and induced coupled plasma power during the plasma enhanced chemical vapor deposition of Si-rich SiO(x) films, the effects of the growth conditions on the defect- and Si nano-pyramid-related carrier transport and Si nanocrystal-related electroluminescence spectroscopy were also investigated. The annealed Si-rich SiO(x)/p-Si films grown at higher synthesized substrate temperate (350 degrees C) show the larger Si nano-pyramids precipitating near the Si/SiO2 interface. The indium tin oxide/Si-rich SiO(x)/p-Si/Al metal-oxide-semiconductor light-emitting diodes with Si-rich SiO(x) films exhibit different white-light electroluminescence spectra at wavelengths from 400 to 650 nm. The Si nanocrystal-related electroluminescence spectra at 650-850 nm are confirmed, whereas the electroluminescence spectra are shorter wavelengths is attributed to oxygen related defects. These defects become an electron-preferred transporting path within the Si-rich SiO(x) film, whose densities are decreased by increasing the substrate temperature or reducing the induced coupled plasma power. Defect-related white-light electroluminescence emits power for a relatively short lifetime. The lifetime can be lengthened and the electroluminescence power can be raised simultaneously by increasing deposition temperature to 350 degrees C and adjusting the induced coupled plasma power to a threshold of 30 W, which effectively increases the densities of Si nanocrystals and nano-pyramids in the Si-rich SiO(x) film with Si concentration of up to 40 at%. A nearly defect-free Si-rich SiO(x) sample can be grown under such conditions, which contributes to the most stable and largest near-infrared electroluminescence with the longest lifetime, although the power-current slope of purely Si nanopyramid related electroluminescence at near-infrared wavelengths is slightly lower.     

Characterization of implantation induced defects in Si-implanted SiO2 film

Si-implanted thermal SiO2 layers and their annealing behaviour were investigated. In the results of variable-energy positron annihilation spectroscopy, the defects caused by ion implantation are manifested as a particularly low S parameter in the Si ion implantation region of the SiO2 layer. Compared with Fourier transform infrared measurements, it suggests that the decrease of the line shape S parameter after implantation is related to the compaction of implanted layers induced by the breaking of the SiO2 network structure. The presence of blue band emission (430-470 nm) in the implanted SiO2 layer is associated with neutral oxygen vacancy. An increase of the S parameter in the implanted layers is observed after annealing at different temperatures, but it is impossible completely recover the pre-implantation condition after a thermal treatment.     

BaTiO3铁电薄膜的光致发光研究

以分析纯的乙酸钡和钛酸正四丁酯为前躯体溶液,冰乙酸为溶剂,乙酰丙酮为稳定剂,采用溶胶-凝胶法在硅基上制备了钛酸钡(BaTiO3)铁电薄膜.研究了BaTiO3铁电薄膜的光致发光性能.结果表明,室温下非晶态的BaTiO3铁电薄膜在蓝光激发下具有很强的光致发光现象.其中,经8h 673K退火处理的非晶BaTiO3铁电薄膜的光致发光性能最佳,当455nm光激发时,非晶薄膜在540～660nm内发出强烈的黄光,峰值波长为580～610nm,峰宽约30nm,发光强度随薄膜的厚度增加而增强.晶态BaTiO3铁电薄膜无任何发光现象.