多孔硅的光学非线性效应

自从1990年英国皇家信号与雷达研究所的Canham发现了多孔硅的可见光发射现象以后[1],在国际上掀起了一股多孔硅发光研究的热潮.继光致发光以后,有好几个研究组已观察到多孔硅的固态电致发光[2],这是向多孔硅在光电子器件的应用方向迈出的一大步.对于多孔硅的发光机理,虽然多数人倾向于认为这是一种量子线或量子点结构的限制效应,但也有一些与之相矛盾的实验结果,以致提出了一些其他的可能机理,如 SiH2或Si6O2H5聚合物,a-St,应变和杂质的作用等.所以要最终确定多孔硅的发光究竟是否是一种量子限制效应,还有待于提供进一步的实验事实. 另一…     

多孔硅结构与发光机理的非线性光学研究

最近的研究中,采用1.06μm超短脉冲光激发,在多孔硅表面观察到了有效的红外多光子激发的荧光发射.研究表明,这是一个增强的三阶非线性光学过程.本文利用其三阶非线性特性对具有强可见光发射的多孔硅结构进行了研究,结果显示晶体硅的各向异性特征在多孔硅中几乎被保留;此外,较强的激光激发导致的红外上转换荧光信号衰减过程被归结为与多孔硅表面氢的脱附有关.     

CuO薄膜的三阶非线性光学特性研究

采用脉冲激光沉积技术在Si(100)和熔石英基片上制备了单相的CuO薄膜.通过X射线衍射仪,拉曼光谱仪,场发射扫描电镜和紫外可见光光度计对薄膜的结构,表面形貌和光学性质进行了表征. 场发射扫描电镜结果表明CuO薄膜中晶粒排列致密且分布均匀,其尺寸约为45nm.结合飞秒激光(800nm,50fs)和Z扫描方法测量了薄膜的三阶非线性光学特性,结果表明CuO薄膜具有超快的非线性光学响应且非线性折射率和非线性吸收系数均为负值,其大小分别为-3.96×10^-17 m^{2< 关键词： CuO薄膜 Z-扫描')" href="#">Z-扫描 三阶光学非线性}     

新型Ru配合物三阶非线性光学性质的Z—扫描研究

通过Ｚ－扫描的实验方法测量了几种新型的Ｒｕ配合物在４６０ｎｍ处的三阶非线性折射率ｎ２和非线性吸收系数β,并由此计算出它们的三阶百线性系数Ｘ＾（３）,分析了分子结构对其三阶非线性光学性质的影响。     

Sb量子点掺杂钠硼硅玻璃的三阶光学非线性

采用溶胶-凝胶法以正硅酸乙酯、硼酸、金属钠为前驱体合成了含Sb量子点的钠硼硅玻璃。紫外-可见(UV-vis)吸收光谱分析表明量子点玻璃的表面等离子体共振吸收峰在566nm附近;利用飞秒激光钛宝石Z-扫描(Z-scan)技术在800nm波长处对玻璃样品的非线性光学性质进行研究,得到了该玻璃的非线性折射率γ,非线性吸收系数β和三阶非线性极化率χ(3)分别为8.59×10-17 m2/W、1.80×10-10 m/W、4.75×10-11 esu;X-射线粉末衍射(XRD)分析表明具有斜方六面体晶相结构的Sb量子点成功的掺入到玻璃基体中;通过透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)对量子点的尺寸大小和颗粒分布进行了表征,结果显示Sb量子点在玻璃中呈规则的球形,并且颗粒尺寸在19~25nm之间。     

稠环芳烃有机物的三阶非线性光学性能研究

采用Ｎｄ：ＹＡＧ皮秒锁模脉冲激光λ＝５３２．０ｎｍ,运用３Ｄ前向简并四波混频（ＤＦＷＭ）的方法,测量了稠环芳烃中的１．２．５．６二苯并蒽（Ｃ２２Ｈ１４）,１．２．８．９．二苯并五苯（Ｃ３０Ｈ１８）的三阶非线性极化率Ｘ＾（３）,非线性折射系数ｎ２以及三阶非线性的时间响应。发现该类材料具有较大的非线性效应,文中分析了非线性形成机制以及相关的影响因素。     

一新型金属有机化合物在皮秒激光下的三阶非线性光学性质研究

利用皮秒激光光源,采用z扫描技术研究了一种新型金属有机化合物的三阶非线性光学性质以及光限幅特性.z扫描研究结果表明,这种化合物在1064 nm波长激光激发下的三阶非线性极化率χ(3)为3.8×１０-14 esu,并且存在双光子吸收.光限幅实验结果显示双光子吸收和非线性折射两种不同机制决定了该化合物的光限幅特性.     

一种新的亚酞菁的共振三阶非线性光学性质

用简并四波混频技术研究了一种新的亚酞菁(三新戊氧基溴硼亚酞菁)的三阶非线性光学性质.测得纯固体三新戊氧基溴硼亚酞菁的三阶非线性极化率χ(3)pure和分子二阶超极化率〈γ〉分别为69×10-10esu和30×10-31esu.χ(3)pure的响应时间为20ps.并对这些结果进行了讨论 关键词：     

三-α-(2,4-二甲基-3-戊氧基)溴硼亚酞菁的三阶非线性光学性质研究

应用Z扫描技术，在波长为532nm、脉宽为8ns条件下，对一种新型亚酞菁配合物三-α-(2,4-二甲基-3-戊氧基)溴硼亚酞菁的三阶非线性光学特性进行了研究，结果发现，该新化合物有较强的反饱和吸收(β=3.7×10^-10 m/W)效应和非线性自聚焦折射效应(n₂=7.2×10^-11esu)，其三阶非线性极化率χ⁽³⁾=1.1×10^-11esu.分析了溴硼亚酞菁配合物特殊的锥形分子结构和重原子溴的轴向配位等因素对其三阶非线性光学性质的重要影响. 关键词： 亚酞菁 Z扫描 三阶光学非线性     

足球烯分子三阶非线性光学性质的研究

报道了有关足球烯分子甲苯溶液中简并四波混频实验.测量出足球烯C_(70)分子和C_(60)分子的三阶超极化率张量y_(1111)分量分别为1.2×10~(-30)esu和4.0×10~(-31)esu.对应于固体样品的三阶非线性光学系数X_(1111)分量分别是2.5×10~(-8)esu和8.5×10~(-9)esu.此结果表明了足球烯分子是现有的非线性光学材料中具有较大三阶非共振电子极化率材料之一.文中还利用自由电子模型解释了非线性光学极化率的起源.     

聚合物材料PMMA/DR1光漂白过程中折射率的变化

用双光束扫描法研究了在488nm的Ar^ 激光照射下，聚合物材料RMMA／DR1的光漂白过程，为精确测量光漂白模型中的参数提供了一种简单实验方法。这对于今后用光漂白的方法制备光波导器件具有重要意义。     

多孔氧化硅薄膜阴极射线谱的研究

采用近常压下等离子体增强化学气相沉积的方法制备得到多孔氧化硅薄膜,并在沉积区域加载偏压对薄膜形貌和性质进行调制。扫描电镜显示偏压条件下沉积的薄膜更加蓬松多孔,常温下阴极射线谱表明:增大偏压的占空比,CL谱中发光峰的位置并不改变,但谱线强度增大。发光峰的位置说明薄膜中的主要成分是Si-O-Si基团,且该种基团以非桥键的形式存在,薄膜中还存在少量的Si-H键,这与红外光谱测试结果一致。X射线衍射结果表明薄膜中的SiO2是非晶态的。     

多孔硅在30~180℃温区光致发光谱的研究

对长期存放在空气中的多孔硅样品和即时制备的多孔硅样品分别在室温~180℃下进行了光致发光（PL）温度效应的研究.两类样品的PL呈现不同的变化规律.前者的PL还表现为双峰,且长波PL峰随温度升高蓝移;后者的PL表现为单峰,且PL峰位随温度升高红移.基于量子限制效应对后者进行了解释;而前者难以用分立的量子限制和表面发光中心模型来解释,实验结果表明两种机制之间可能有较复杂的耦合效应发生.     

GaN1-xPx三元合金的光学与结构特性

对采用金属有机化学气相淀积(MOCVD)技术生长的GaN1-xPx三元合金进行了低温光致发光(PL)和X射线衍射(XRD)测试分析,与来自GaN层的带边发射相比,P的摩尔分数比为0．03,0．11和0．15的GaN1-xPx的光致发光峰分别呈现出了73meV,78meV和100meV的红移,文中将这种红移归因于GaN1-xPx合金具有大的带隙能量弯曲系数。X射线衍射结果表明GaN1-xPx三元合金仍为六方结构晶体,且随着P组份比的增加,GaN1-xPx合金的(0002)衍射峰逐渐向小角度方向移动,即晶格常量变大,同时,(0002)衍射峰谱线不断宽化,说明由于替位式P原子的不规则分布以及部分间隙P原子的影响造成了GaN1-xPx样品的晶格畸变。在GaN1-xPx的光致发光谱及X射线衍射谱中均未观测到相应的有关GaP的峰,表明所生长的高P含量的GaN1-xPx三元合金没有产生明显的相分离。     

红外透过、反射吸收光谱研究手性液晶(M1)LB膜的结构与取向

利用ＦＴＩＲ光谱研究了一种手性液晶化合物（Ｍ１）ＬＢ膜的结构与取向,该化合物可以形成稳定的单层与多层膜。手性分子中,芳香环平面向于垂直基片表面,分子中的烷基链部分则与基底表面法线方向成一定的角度。     

外部荧光种子植入法增强液芯光纤中CS2的受激拉曼散射研究

本文报道了运用外部荧光种子(罗丹明6G乙醇溶液)植入法对液芯光纤中CS2受激拉曼散射的增强研究。实验结果表明, CS2的二阶、三阶Stokes波分别获得了1.92和11.71倍的增益。并对外部荧光种子植入法增强液芯光纤中受激拉曼散射的机制进行了分析。     

STM studies of cyclohexene hydrogenation/dehydrogenation and its poisoning by carbon monoxide on Pt(1 1 1)

A scanning tunneling microscope that can be operated in ultra high vacuum (<10⁻⁹ Torr) as well as at high pressures (1 − 10³ Torr) has been utilized to study the structures formed by cyclic C₆ hydrocarbons adsorbed on a platinum (1 1 1) crystal surface. Catalytic reactions of cyclohexene were also studied in the presence of hydrogen at pressures (up to 200 mTorr) and 300 K-350 K temperature range. Cyclohexane and cyclohexene produced the same adsorbed structure, which is attributed to the partially dehydrogenated π-allyl (C₆H₉). 1,3-Cyclohexadiene produced structures similar to those produced by benzene. In contrast 1,4-cyclohexadiene forms a structure that we attribute to intact molecular 1,4-cyclohexadiene. During reaction the STM images appear disordered, indicative of rapid diffusion of surface species. Addition of 5 mTorr of CO stops the catalytic activity and forms an ordered structure on the surface.     

Si 2p and O 1s photoemission from oxidized Si(0 0 1) surfaces depending on translational kinetic energy of incident O2 molecules

The influence of translational kinetic energy of incident O₂ molecules for the passive oxidation of the partially oxidized Si(0 0 1) surface has been studied by photoemission spectroscopy. The incident energy of O₂ molecules was controlled up to 3 eV by a supersonic molecular beam technique. Two incident energy thresholds (1.0 and 2.6 eV) were found out in accordance with the first-principle calculations. Si 2p and O 1s photoemission spectra measured at representative incident energies showed the incident energy induced oxidation at the backbonds of the dimer and the second layer (subsurface) Si atoms. Moreover, the difference of oxygen chemical bonds was found out to be as the low and the high binding energy components in the O 1s photoemission spectra. They were assigned to bridge sites oxygen and dangling bond sites oxygen, respectively.     

Adsorption of 2-butyne on Si(0 0 1) at room temperature: A valence band photoemission study

We present an angle resolved ultraviolet photoemission spectroscopy study of the adsorption of 2-butyne (CH₃-CC-CH₃) on Si(0 0 1)-2 × 1 at room temperature. We recorded valence band photoemission spectra for two azimuthal positions of a vicinal silicon surface, where all the rows formed by the surface silicon dimers are parallel. The photoemission symmetry selection rules allow the determination of the orientation of the molecular orbitals. The photoemission signal of the HOMO is enhanced when the electric field is parallel to the dimer rows. This showed that the π orbital left intact after the cyclo-addition reaction of the molecule with one silicon dimer is parallel to the dimer rows. This indicates that each 2-butyne molecule adsorbs on one silicon dimer. In spite of the size of the system and the vicinity of the orbitals, the angle resolved study points out that no dispersion of the electronic bands occurs. Not all the surface dimers are reacted so some disorder still exists on the surface preventing the formation of Bloch states.     

High resolution X-ray photoelectron spectroscopy study on initial oxidation of 4H-SiC(0 0 0 1)-(√3 × √3)R30° surface

An initial oxidation dynamics of 4H-SiC(0 0 0 1)-(√3 × √3)R30° surface has been studied using high resolution X-ray photoelectron spectroscopy and supersonic molecular beams. Clean 4H-SiC(0 0 0 1)-(√3 × √3)R30° surface was exposed to oxygen molecules with translational energy of 0.5 eV at 300 K. In the first step of initial oxidation, oxygen molecules are immediately dissociated and atomic oxygens are inserted into Si-Si back bonds to form stable oxide species. At this stage, drastic increase in growth rate of stable oxide species by heating molecular beam source to 1400 K was found. We concluded that this increase in growth rate of stable oxide is mainly caused by molecular vibrational excitation. It suggests that the dissociation barrier is located in the exit channel on potential energy hypersurface. A metastable molecular oxygen species was found to be adsorbed on a Si-adatom that has two oxygen atoms inserted into the back bonds. The adsorption of the metastable species is neither enhanced nor suppressed by molecular vibrational excitation.