高剂量Ge离子注入直接形成nc-Ge的研究

报道了分别采用剂量为1e1 6 ,1e1 7,5e 1 7和1e1 8cm- 2的高剂量Ge离子注入,不需退火即可在Si O2中直接形成Ge纳米晶的新现象.采用掠入射X射线衍射和激光喇曼谱等实验手段对样品进行了物相分析.结果表明,高剂量Ge离子注入可在SiO2 薄膜中直接形成Ge纳米晶(nc- Ge) ;非晶态Ge向晶态Ge发生相变的阈值剂量约为1e1 7cm- 2 ,离子注入直接形成的nc- Ge内部具有较大压应力,随着注入剂量的提高,nc- Ge的尺寸和含量均有提高.对纳米晶形成机理的研究认为,在Ge离子注入剂量达到阈值,此时膜中Ge非晶态团簇浓度达到饱和甚至过饱和,新入射的     

高剂量Ge离子注入直接形成nc-Ge的研究

报道了分别采用剂量为1×1016,1×1017,5×1017和1×1018cm-2的高剂量Ge离子注入,不需退火即可在SiO2中直接形成Ge纳米晶的新现象.采用掠入射X射线衍射和激光喇曼谱等实验手段对样品进行了物相分析.结果表明,高剂量Ge离子注入可在SiO2薄膜中直接形成Ge纳米晶(nc-Ge);非晶态Ge向晶态Ge发生相变的阈值剂量约为1×1017cm-2,离子注入直接形成的nc-Ge内部具有较大压应力,随着注入剂量的提高,nc-Ge的尺寸和含量均有提高.对纳米晶形成机理的研究认为,在Ge离子注入剂量达到阈值,此时膜中Ge非晶态团簇浓度达到饱和甚至过饱和,新入射的Ge离子把动能传递给膜中的非晶态Ge原子,使其部分析出并团聚形成能量最低且最稳定的Ge纳米晶态.     

飞秒激光前向转移诱导产生金属纳米结构薄膜

使用掺镱光子晶体光纤飞秒激光放大系统作为加工光源,利用激光诱导前向转移(LIFT)技术对铜膜进行加工,产生纳米结构。通过控制飞秒激光光源参数,得到不同纳米结构的金属薄膜。在功率较低时,能够得到纳米团簇;随着功率升高,团簇尺寸变大;到达一定功率时,出现纳米线结构。通过实验分析了飞秒激光与材料相互作用时发生的物理过程。利用该机理,对20,40,200nm三种厚度的铜膜在相同实验条件下的实验结果进行比较,获得了产生纳米团簇和纳米线结构薄膜的最佳条件。     

二硫化钼纳米片基纳米团簇的制备及其在近红外激光的热转换性能

探讨了γ-聚谷氨酸(γ-PGA)介导合成γ-PGA/二硫化钼(MoS_2)纳米团簇的可行性,分析了γ-PGA/MoS_2纳米团簇在近红外激光的热转换性能。将γ-PGA和合成MoS_2纳米片的前驱体四硫代钼酸铵同时溶解于蒸馏水中,通过水热法自下而上一步合成出了γ-PGA修饰的MoS_2纳米团簇,MoS_2纳米团簇的直径为(197.3±26.6)nm。团簇结构的形成可能与Mo~(4+)离子和γ-PGA链中羧基上氧原子的配位作用有关。在水热反应过程中,由于这种配位作用的存在,生成的MoS_2纳米片可能进一步以γ-PGA分子链中氧原子为中心形成团簇。该纳米团簇具有优异的胶体稳定性、光热转换性能(质量消光系数为11.23L·g~(-1)·cm~(-1))和细胞相容性,有望在肿瘤的光热治疗等领域得到应用。     

(Si/Ge)n多层薄膜的设计制备及光吸收性能

采用射频磁控溅射技术,在石英玻璃衬底上沉积了具有不同层数和厚度的(Si/Ge)n多层薄膜。XRD、Raman光谱测试表明,溅射态薄膜为微晶结构,在溅射过程中层间扩散形成Si-Ge振动键,溅射时间和薄膜层数影响着薄膜层间的扩散和结晶率;FESEM结果表明,薄膜表面由颗粒团簇构成,层与层之间有明显界面。UV-vis光谱测试表明,(Si/Ge)n多层薄膜在可见光范围内具有较宽的吸收,增加薄膜层数可扩大太阳能光谱的响应范围,而增加Si单层膜厚度对光吸收范围的影响较小。     

高剂量离子注入直接形成Ge纳米晶的物理机理

研究了单束双能高剂量Ge离子注入、不经过退火在非晶态SiO2薄膜中直接形成镶嵌结构Ge纳米晶的物理机制．实验中利用不加磁分析器的离子注入机，采用Ge弧光放电离化自动形成的Ge+和Ge2+双电荷离子并存的单束双能离子注入方法，制备了1e16～1e18cm－2多种剂量Ge离子注入的Si基SiO2薄膜样品．用GIXRD表征了Ge纳米晶的存在，并仔细分析得到了纳米晶形成的阈值剂量．通过TEM分析了Ge纳米晶的深度分布和晶粒尺寸．用SRIM程序分别计算了双能离子在SiO2非晶层的射程和深度分布，与实验结合，得到纳米晶形成的物理机制，即纳米晶的形成与单束双能离子注入时Ge＋和Ge2＋相互碰撞产生的能量沉积在SiO2中形成的局域高温有关．     

热致漂白效应对非晶Ge34Ga2S64薄膜结构和光学特性的影响

采用热蒸发法技术沉积Ge34Ga2S64非晶薄膜,并对薄膜样品在375℃热处理2h。通过分光光度计、表面轮廓仪和显微拉曼光谱仪测试热处理前后薄膜样品的透过曲线、薄膜厚度和拉曼结构。利用薄膜干涉曲线的波峰和波谷计算了薄膜的厚度和折射率,并根据Swanepoel方法以及Tauc公式分别计算了薄膜折射率色散曲线和光学带隙等参数。结果表明,Ge34Ga2S64非晶薄膜经热处理后发生热致漂白效应,大分子团簇以及Ge-Ge、S-S同极错键含量明显减少,网络结构无序性降低,从而引起薄膜的光学吸收边蓝移、折射率降低、表面粗糙度(Ra)降低0.515nm和光学带隙增大0.118eV。     

高剂量离子注入直接形成Ge纳米晶的物理机理

研究了单束双能高剂量Ge离子注入、不经过退火在非晶态SiO2薄膜中直接形成镶嵌结构Ge纳米晶的物理机制.实验中利用不加磁分析器的离子注入机,采用Ge弧光放电离化自动形成的Ge+和Ge2+双电荷离子并存的单束双能离子注入方法,制备了1016～1018cm-2多种剂量Ge离子注入的Si基SiO2薄膜样品.用GIXRD表征了Ge纳米晶的存在,并仔细分析得到了纳米晶形成的阈值剂量.通过TEM分析了Ge纳米晶的深度分布和晶粒尺寸.用SRIM程序分别计算了双能离子在SiO2非晶层的射程和深度分布,与实验结合,得到纳米晶形成的物理机制,即纳米晶的形成与单束双能离子注入时Ge+和Ge2+相互碰撞产生的能量沉积在SiO2中形成的局域高温有关.     

CdSe纳米团簇的透射电镜研究

在沸石分子筛中组装ＣｄＳｅ而形成半导体纳米团簇材料，并将组装ＣｄＳｅ后的沸石微粉制成完整的透射电镜薄膜，结合能谱测试，在透射电镜下观察所制得的材料的微观结构和形貌．结果表明在沸石中形成了尺寸单一、分布均匀的团簇材料     

Pt/PZT铁电薄膜结晶性能与界面结构研究

锆钛酸铅[Pb(ZrxTi1-x)O3,PZT]薄膜具有优异的铁电性能,其中以(111)取向的PZT薄膜铁电性能更优异。目前对影响PZT薄膜取向生长的因素还未完全研究清楚,而PZT薄膜制备中,薄膜的择优取向生长控制是薄膜制备工艺的难点。采用TEM观察界面微观结构,利用高斯软件在TPSS/def2-TZVP水平下计算优化出PbxPt团簇分子的结构,发现界面层上形成的这类分子属于量子点范畴,结构上与PZT薄膜(111)晶面取向相似。提出高温退火生成的大量PbxPt团簇分子是(111)晶面取向生长的"诱导剂",控制界面层这种物质的生成和扩散可以控制PZT薄膜(111)取向生长。     

Self-organization of germanium highly ordered nanoclusters by the deposition of polycrystalline silicon films doped with germanium

Aspects of the formation of self-organized clusters of germanium (Ge) and solid solution of SiGe, first formed in the mode of deposition of subthin polycrystalline silicon films doped with Ge on the nanoscale film of dielectrics were studied by techniques of atomic force microscopy and Raman scattering by optical phonons in germanium clusters. We found that in subthin polycrystalline silicon films (PSF) doped with Ge on the nanoscale films of dielectrics in conditions of PSF film deposition, there appeared correlated spatial distribution of germanium clusters, as well as silicon rich clusters in certain conditions, i.e., clusters of SiGe solid solution, with the modes of their formation. The relationship of the form, size, and density of Ge nanoclusters (NC), with the conditions of their self-organization is considered. The influence of interdiffusion processes on self-organizing of clusters is established, which is significant at high temperatures of the deposition and doping of PSF. It was found that clusters (islands) could occur on the cleavage surface in the form of four types of topographic features in a classical pyramid form, flat-topped pyramids, and domes and sharp spines, depending on the conditions of the deposition of PSF doped with Ge. The systems of highly organized Ge NC, measuring 3.5–40 nm and with a density of 2.7 × 10⁷–3.5 × 10 cm⁻² were obtained. The possibility, in principle, of managing the geometric parameters of self-organizing NC (nanoislands) by selecting the conditions of their self-organization in the mode of deposition of PSF doped with Ge, was shown.     

Selective Immobilization of Nanoparticles on Surfaces by Molecular Recognition using Simple Multiple H‐bonding Functionalities

Using a complementary pair of simple alkylthiolates with hydrogen‐bonding moieties, functionalized Au₅₅ clusters could be selectively deposited onto self‐assembled monolayers on gold that carry the opposite functionality. The deposition can be readily controlled by the medium in which the clusters are dissolved and by the density of the functionalities in the self‐assembled monolayers, and yields single clusters as well as two‐dimensional cluster assemblies on the surface. The clusters are sufficiently strongly bound to give structures that are stable at ambient temperature, and that allow scanning tunneling spectroscopy on single clusters on the surface.     

On the size distribution in three-dimensional quantum-dot crystals

The size distribution function of nanodots in artificial three-dimensional (Si)Ge/Si and In(Ga)As/GaAs quantum dot crystals grown using templates with perfect periodicity is calculated. Pyramidal nanodots were modeled by cone-shaped clusters for which the Thomson formula was derived, which is necessary to determine the growth (dissolution) rate of clusters during Ostwald ripening. A comparison of the calculated curve with experimental histograms shows that the size distribution itself is formed during Ostwald ripening and is caused by features of Ge and InAs quantum-dot formation on preliminarily textured Si and GaAs substrates.     

Formation and study of <Emphasis Type="Italic">p–i–n</Emphasis> structures based on two-phase hydrogenated silicon with a germanium layer in the <Emphasis Type="Italic">i</Emphasis>-type region

Four pairs of p–i–n structures based on polymorphous Si:H (pm-Si:H) are fabricated by the method of plasma-enhanced chemical vapor deposition. The structures in each pair are grown on the same substrate so that one of them does not contain Ge in the i-type layer while the other structure contains Ge deposited by molecular-beam epitaxy as a layer with a thickness of 10 nm. The pair differ from one another in terms of the substrate temperature during Ge deposition; these temperatures are 300, 350, 400, and 450°C. The data of electron microscopy show that the structures formed at 300°C contain Ge nanocrystals (nc-Ge) nucleated at nanocrystalline inclusions at the pm-Si:H surface. The nc-Ge concentration increases as the temperature is raised. The study of the current–voltage characteristics show that the presence of Ge in the i-type layer decreases the density of the short-circuit current in p–i–n structures when they are used as solar cells, whereas these layers give rise to an increase in current at a reverse bias under illumination. The obtained results are consistent with known data for structures with Ge clusters in Si; according to these data, Ge clusters increase the coefficient of light absorption but they also increase the rate of charge-carrier recombination.     

Investigation of Ge film growth on the Si(100) surface by recording diffractometry

A diagram of the structural and morphological state of a Ge film on a Si(100) surface is constructed using in situ recording of the reflection high-energy electron diffraction patterns. The diagram involves the following regions: the continuous film, hut-and dome-shaped clusters, and dome-shaped clusters with misfit dislocations at the interface. The variation in the lattice parameters of the Ge film during MBE growth on the Si(100) surface is measured for the first time, and the oscillations of the variation in the lattice parameter for the (100) plane during two-dimensional layer-by-layer growth are found.     

Ge-nanocluster formation in Ge-doped polysilicon films under oxidation and heat treatment

An experimental investigation is conducted into the formation Ge nanoclusters by heat treatment of germanosilicate-glass (Si _x Ge _y O _z ) films that are produced by oxidation of Ge-doped nanostructured polysilicon. It employs Auger and IR spectroscopy, high-resolution electron microscopy, and x-ray diffraction. The process by which Ge atoms in the films are transported toward the substrate is found to include the following stages: (1) the formation of a GeO₂ and a SiO₂ phase, (2) the reduction of GeO₂ to Ge by Si, (3) Ge-crystallite nucleation, and (4) Ge-crystallite growth. Heat treatment in humid oxygen at ≥ 800°C is found to increase Ge-nanocluster size, the point of crystallization being 500°C. It is established that heat treatment at a temperature close to the Ge melting point results in complete aggregation of the germanium into clusters, with a twofold increase in both the mean size and the number of clusters. Germanium is found to accumulate at the interface between oxidized and unoxidized polysilicon.     

Spin-orbit interaction of charge carriers with impurities in aligned Ge<Subscript>0.99</Subscript>Me<Subscript>0.01</Subscript> (Me = Mn,Cr, Co,Fe) nanowires

Aligned Ge_0.99Me_0.01 (Me = Mn, Cr, Co, Fe) nanowires have been investigated by electron spin resonance (ESR). Resonance lines corresponding to a magnetically ordered subsystem of localized spins (clusters of Ge alloys with transition metals) and an asymmetric Dysonian line, corresponding to the ESR of charge carriers in Ge, are identified in the ESR spectra. A systematic decrease in the effective g factor of the asymmetric Dysonian line with enhancement of spin-orbit interaction is found in the series of transition-metal ions Mn²⁺, Cr²⁺, Fe³⁺, and Co²⁺, which were used to dope Ge nanowires.     

Suppression of dome-shaped clusters during molecular beam epitaxy of Ge on Si(100)

Morphological properties of Ge nanoscale island arrays formed on the Si(100) surface during molecular beam epitaxy are studied using reflection high-energy electron diffraction and atomic-force microscopy. It is shown that codeposition of Sb and Ge significantly increases the density of final island arrays and suppresses the formation of dome-shaped clusters at substrate temperatures of 550–600°C. The results are discussed in the context of the kinetic model of formation of elastically strained islands in heteroepitaxial systems with a lattice mismatch.     

Boron retarded diffusion in the presence of indium or germanium

Experimental results of germanium (Ge) and indium (In) preamorphization by ion-implantation show that the diffusion of boron (B) is retarded by the presence of Ge or In and that this retardation is more important than the preamorphization (dechanneling) effect. Result shows that In retards B diffusion more than Ge and the retardation effect due to In becomes greater with increasing retained dose of In. Larger In doses cause larger strain, which results in more B being tied up in immobile clusters near the surface. In order to achieve adequate retained dose of In, the implanted dose of In must be increased to 5/spl times/10/sup 15/ cm/sup -2/. After anneal, the junction depth (at 10/sup 18/ cm/sup -3/) is reduced from 628 /spl Aring/ in the control wafer (no In co-implant) to 480 /spl Aring/.     

Synthesis of ZnO: Ge nanocomposite thin films by plasma gas condensation

In this work, we introduce a new method for the synthesis of Ge nanoparticles embedded ZnO thin films that are considered to be a potential candidate for photovoltaic applications. As opposed to current techniques, for the independent preparation of Ge nanoparticles, we propose using Cluster Deposition Source (CDS), which utilizes gas condensation of sputtered Ge atoms. For the synthesis of ZnO thin film host material conventional sputtering technique is employed. In the proposed technique independently synthesized Ge nanoparticles and ZnO thin films are combined into a composite structure on (100) oriented Si substrates. X-ray diffraction (XRD) patterns of the samples have revealed that Ge nanoparticles preferentially settle on (113) planes on top of the (002) oriented ZnO layer. It is realized that Ge nanoparticles with sizes ranging from 16 nm to 20 nm could be embedded into a well-defined ZnO matrix. In fact, transmission electron microscopy (TEM) studies performed on Ge nanoparticles captured on a Cu grids placed just above the substrate during deposition for about 60 s have manifested that Ge nanoparticles reach to ZnO matrix as clusters composed of particles with sizes of about 7–8 nm and then eventually grow larger due to substrate heating implemented during capping layer deposition. Optical absorption measurements have revealed that Ge nanoparticle inclusion lead to an additional absorption edge at about 2.75 eV along with 3.17 eV edge resulting from ZnO host.