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。     

纳米TiO2薄膜的制备与表面形貌研究

研究退火温度对薄膜相结构、表面化学组成及形貌的影响。采用射频磁控溅射法在单晶硅片上淀积TiO2薄膜,通过X射线衍射（XRD）、原子力显微镜（AFM）和X光电子能谱（XPS）对其进行表征。结果表明,室温制备400℃以下退火的TiO2薄膜为无定形结构,400℃以上退火的TiO2薄膜出现锐钛矿相,600℃以上退火的TiO2薄膜开始出现金红石相,退火温度在1000℃以上时样品已经完全转变为金红石相;随着退火温度的升高,晶粒尺寸和表面粗糙度逐渐增大,但是当退火温度为1000℃时反而有所减小,晶粒尺寸和表面粗糙度在退火温度为1000℃时发生的这一突变现象,是由该退火温度下的相变导致。     

真空共蒸发法制备CuxTe薄膜的结构特性分析

用真空共蒸发法制备了CuxTe（1≤x≤2）薄膜,并通过X射线衍射（XRD）、X射线光电子能谱（XPS）及原子力显微镜（AFM）等表征手段分析了薄膜的结构特性,研究了热处理对不同Cu/Te配比的样品物相转变的影响。结果发现：刚沉积的薄膜非晶结构占主导地位,只有部分低Cu/Te比的薄膜出现多晶结构;退火后,薄膜发生晶相转变,且随着退火温度的升高,不同配比的样品有着不同程度的物相转变。其中,较低配比（x=11、.44）的样品多晶转变较为明显,结晶度较高,说明较小x值的薄膜晶化温度较低,而高x值的薄膜晶化温度较高。用CuxTe薄膜作为背接触层,获得了效率为12.5%的CdS/CdTe小面积太阳电池。     

退火温度对CsI（T1）薄膜微观结构和闪烁性能的影响

采用真空热蒸发法制备了CsI（T1）薄膜,然后进行了不同温度的真空热处理．用X射线衍射仪、扫描电子显微镜、X射线荧光光谱仪及正电子寿命谱仪对CsI（T1）薄膜样品进行了分析,并测得了样品的光产额．结果表明,该CsI（T1）薄膜沿（200）晶面择优取向生长．经过较低温度退火,CsI薄膜中的Tl^＋离子向薄膜表面扩散,薄膜中缺陷数量增加,且尺寸较大,光产额略微增高．经过250℃退火,薄膜中低温退火所形成缺陷得到恢复,薄膜缺陷尺寸变小,且数目减少,具有较好的结晶状态,光产额提高．经过400℃退火,薄膜结构发生显著变化,薄膜中缺陷大幅增加,结晶状态变差,Ti^＋含量减少,光产额急剧下降．     

RF磁控溅射法制备ZnO薄膜的XRD分析

采用RF磁控溅射法，在玻璃村底上制备多晶ZnO薄膜，并对所制备的ZnO薄膜在空气气氛中进行了不同温度（350～600℃）的退火处理和600℃时N2气氛中的退火处理。利用X射线衍射分析了溅射参数如溅射功率、溅射氧分压、衬底温度以及退火处理对ZnO薄膜结晶性能的影响。结果表明，合适的衬底温度和退火处理能够提高ZnO薄膜的结晶质量。     

磁控溅射制备五氧化二钒薄膜的研究

采用射频磁控溅射的方法,在不同条件下制备了氧化钒薄膜样品,分别在不同温度条件下做了退火处理,并对退火前后样品做了X射线衍射(XRD)、X射线光电子能谱(XPS)和激光扫描共聚焦显微镜测试与分析,旨在得出制备良好的V2O5 薄膜的条件。     

退火温度对磁控溅射制备的β-FeSi2薄膜的影响

采用磁控溅射的方法，在高真空条件下，沉积金属Fe到Si（100）衬底上，然后通过真空退火炉在不同温度条件下对样品进行热处理，直接形成了β-FeSi2薄膜．采用X射线衍射仪（XRD）对样品进行了晶体结构分析，利用卢瑟福背散射（RBS）对Fe-Si化合物的形成过程中的Fe原子和Si原子的互扩散机理进行了研究，利用扫描电镜（SEM）对样品表面的显微结构进行表征，结果表明，在900℃条件下退火能够得到质量很好的β-FeSi2薄膜，超过这一温度β相将开始向α相转化，到1000℃，β-FeSi2全部转化为α-FeSi2。     

退火温度对二氧化钛薄膜结构和浸润性能的影响

采用多弧离子镀技术在玻璃上沉积单质Ti薄膜,利用稳压电源对单质Ti薄膜进行阳极氧化,随后在不同温度下对其进行退火处理,研究了退火温度对TiO_2薄膜结构和浸润性能的影响。利用X射线衍射仪、扫描电子显微镜、接触角测量仪分别测试薄膜样品的微观结构、表面形貌和浸润性。结果表明:退火处理使薄膜样品由处理前的非晶态转变成晶态,随着退火温度的升高,薄膜由锐钛矿相转变为金红石相;薄膜表面依次出现了螺旋线、纳米线、团絮状结构;接触角先增大后减小。退火温度为500℃时,薄膜样品的疏水性能最好,其接触角平均值最大,为121.78°。     

退火温度对TiO2薄膜结构和表面形貌的影响

研究了退火温度对中频交流反应磁控溅射技术制备的TiO2薄膜结构和表面形貌的影响。利用X射线衍射 仪和原子力显微镜，检测了TiO2薄膜的晶体结构和表面形貌。实验结果显示：沉积态TiO2薄膜为非晶态；低温（700℃以下）退火后，TiO2薄膜出现锐钛矿相，晶粒长大不明显；高温退火（900℃以上）后，薄膜转变为金红石相，晶粒由柱状转变为棱状，并迅速长大至微米量级。     

原子层沉积低温制备高取向锐钛矿TiO_2薄膜

利用原子层沉积(ALD)法分别在Si和石英衬底上制备了Ti O_2薄膜,并在N2氛围下对Ti O_2薄膜样品进行退火处理。采用X射线衍射、原子力显微镜和场发扫描电子显微镜对不同退火温度下样品晶体结构、表面形貌进行了分析。利用紫外-可见分光光度计对不同退火温度下的Ti O_2薄膜进行了光学性能测试,并分析了退火温度对其光学带隙的影响。发现利用ALD方法制备的沉积态Ti O_2薄膜为高度择优取向的锐钛矿结构;当退火温度升高到600℃时,Ti O_2薄膜晶体结构类型仍为锐钛矿型,晶粒略有变大;退火态Ti O_2薄膜粗糙度比沉积态Ti O_2薄膜的粗糙度大,而且粗糙度随退火温度升高而增大。根据薄膜的透射光谱拟合了光学带隙,退火后薄膜禁带宽度略有变宽,吸收边缘发生蓝移。     

Influence of hydrogen on thermally induced phase separation in GeO/SiO2 multilayers

The influence of the annealing atmosphere on the temperature induced phase separation of Ge oxide in GeO(x)/SiO(2) multilayers (x≈1), leading to size controlled growth of Ge nanocrystals, is explored by means of x-ray absorption spectroscopy at the Ge K-edge. Ge sub-oxides contained in the as-deposited multilayers diminish with increasing annealing temperature, showing complete phase separation at approximately 450?°C using inert N(2) ambient. The use of reducing H(2) in the annealing atmosphere influences the phase separation even at an early stage of the disproportionation. In particular, the temperature regime where the phase separation occurs is lowered by at least 50?°C. At temperatures above 400?°C the sublayer composition, and thus the density of the Ge nanocrystals, can be altered by making use of the reduction of GeO(2) by H(2).     

Stacked Ge nanocrystals with ultrathin SiO₂ separation layers

The aim of this work is the tailored growth of Ge nanocrystals (NCs) in (GeO(x)/SiO(2)) multilayers (ML) for photovoltaic applications. For this purpose the fabrication of regularly stacked Ge NCs separated by ultrathin SiO(2) layers is essential to enable charge carrier transport by direct tunnelling. In this paper we report on the fabrication of (GeO(x)/SiO(2))(50) multilayer stacks via reactive dc magnetron sputtering and Ge NCs formation after subsequent annealing. It is shown that magnetron sputtering allows us to deposit very regular ML stacks with a total thickness of about 300 nm, characterized by ultrathin (down to 1 nm) and very smooth (roughness ～ 0.6 nm) SiO(2) separation layers. A main challenge is to keep these properties for a thermal budget necessary to form Ge NCs. For this reason, the temperature dependence of phase separation. Ge crystallization and ML morphology was investigated by Rutherford backscattering, x-ray scattering, Raman spectroscopy and electron microscopy. The formation of size confined Ge NCs of about 5 nm after annealing of only 550?°C is confirmed. This low thermal budget ensures the suppression of GeO emanation and multilayer stability. Spectroscopic ellipsometry was applied to determine the optical Ge NC bandgap to (1.65 ± 0.5) eV.     

Fabrication of multilayered Ge nanocrystals by magnetron sputtering and annealing

Multilayered Ge nanocrystals embedded in Si and Ge oxide films have been fabricated on Si?substrate by a (SiO(2)+Ge)/(SiO(2)+GeO(2)) superlattice approach, using an rf magnetron sputtering technique with a Ge+SiO(2) composite target and subsequent thermal annealing in N(2) ambient at 750?°C for 5?min. X-ray diffraction (XRD) measurements indicated the formation of Ge nanocrystals with an average size estimated to be 9.8?nm. Raman scattering spectra showed a peak of the Ge-Ge vibrational mode shifted downwards to 298.8?cm(-1), which was caused by quantum confinement of phonons in the Ge nanocrystals. X-ray photoemission spectroscopy (XPS) analysis demonstrated that the Ge chemical state is mainly Ge(0) in the (SiO(2)+Ge) layer and Ge(4+) in the (SiO(2)+GeO(2)) layer in the superlattice structure. Transmission electron microscopy (TEM) revealed that Ge nanocrystals were confined in (SiO(2)+Ge) layers, and had good crystallinity. This superlattice approach significantly improved both the size uniformity of Ge nanocrystals and their uniformity of spacing on the 'Z' growth direction compared with the conventional Ge-ncs fabrication method using a single and thick SiO(2) matrix film.     

Negative photoconductivity and memory effects of germanium nanocrystals embedded in HfO2 dielectric

A metal-insulator-semiconductor (MIS) structure containing an HfO2/SiO2 stack tunnel layer, isolated Germanium (Ge) nanocrystals, and an HfO2 capping layer, was obtained by an electron-beam evaporation method. A high-resolution transmission electron microscopy (HRTEM) study revealed that uniform and pronounced Ge nanocrystals had formed after annealing. Raman spectroscopy provided evidence for the formation of Ge-Ge bonds and the optimal annealing temperature for the crystallization ratio of the Ge. The electric properties of the MIS structure were characterized by capacitance-voltage (C-V) and current-voltage (I-V) measurements at room temperature. Negative photoconductivity was observed when the structure was under a forward bias, which screened the bias voltage, resulting in a decrease in the current at a given voltage and a negative shift in flat band voltage. A relatively high stored charge density of 3.27 x 10(12) cm 2 was also achieved.     

Ge-Si-O phase separation and Ge nanocrystal growth in Ge:SiO(x)/SiO(2) multilayers--a new dc magnetron approach

Ge:SiO(x)/SiO(2) multilayers are fabricated using a new reactive dc magnetron sputtering approach. The influence of the multilayer stoichiometry on the ternary Ge-Si-O phase separation and the subsequent size-controlled Ge nanocrystal formation is explored by means of x-ray absorption spectroscopy, x-ray diffraction, electron microscopy and Raman spectroscopy. The ternary system Ge-Si-O reveals complete Ge-O phase separation at 400?°C which does not differ significantly to the binary Ge-O system. Ge nanocrystals of < 5?nm size are generated after subsequent annealing below 700?°C. It is shown that Ge oxides contained in the as-deposited multilayers are reduced by a surrounding unsaturated silica matrix. A stoichiometric regime was found where almost no GeO(2) is present after annealing. Thus, the Ge nanocrystals become completely embedded in a stoichiometric silica matrix favouring the use for photovoltaic applications.     

Study of Ge2Sb2Te5 Film for Nonvolatile Memory Medium

The amorphous Ge2Sb2Te5 film with stoichiometric compositions was deposited by co-sputtering of separate Ge, Sb, and Te targets on SiO2/Si (100) wafer in ultrahigh vacuum magnetron sputtering apparatus. The crystallization behavior of amorphous Ge2Sb2Te5 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). With an increase of annealing temperature, the amorphous Ge2Sb2Te5 film undergoes a two-step crystallization process that it first crystallizes in face-centered-cubic (fcc) crystal structure and finally fcc structure changes to hexagonal (hex) structure. Activation energy values of 3.636±0.137 and 1.579±0.005 eV correspond to the crystallization and structural transformation processes, respectively. From annealing temperature dependence of the film resistivity, it is determined that the first steep decrease of the resistivity corresponds to crystallization while the second one is primarily caused by structural transformation from     

溶胶-凝胶法制备Ge/SiO2微晶复合薄膜

采用Ｓｏｌ－ｇｅｌ方法制备了ＧｅＯ２－ＳｉＯ２复合薄膜,并用Ｈ２／Ｎ２还原使得ＧｅＯ２转变成Ｇｅ微晶而镶嵌在ＳｉＯ２的玻璃网格中,其平均晶粒尺寸小于４ｎｍ 。随着热处理时间的增加,２４０ｎｍ 处吸收峰的强度随之增大,并且其吸收边产生红移,说明Ｇｅ 微晶的含量及晶粒尺寸都在增大     

氧化增强注氧隔离工艺制备绝缘体上的硅锗

提出一种氧化增强注氧隔离工艺,在退火前氧化得到SiO2层,再进行高温退火得到绝缘体上的硅锗材料.经X射线摇摆曲线和拉曼测试发现所制备的绝缘体上的SiGe材料锗含量没有发生损失,且应变弛豫完全.透射电镜和二次离子质谱分析结果显示样品多层结构清晰,埋氧层质量完好、平整度高、无不连续、无硅岛.研究表明,氧化增加工艺的引入是绝缘体上的硅锗材料锗质量提高的关键.     

Remote plasma enhanced chemical deposition of non-crystalline GeO2 on Ge and Si substrates

Non-crystalline GeO2 films remote were plasma deposited at 300 degrees C onto Ge substrates after a final rinse in NH4OH. The reactant precursors gas were: (i) down-stream injected 2% GeH4 in He as the Ge precursor, and (ii) up-stream, plasma excited O2-He mixtures as the O precursor. Films annealed at 400 degrees C displayed no evidence for loss of O resulting in Ge sub-oxide formation, and for a 5-6 eV mid-gap absorption associated with formation of GeOx suboxide bonding, x < 2. These films were stable in normal laboratory ambients with no evidence for reaction with atmospheric water. Films deposited on Ge and annealed at 600 degrees C and 700 degrees C display spectra indicative of loss of O-atoms, accompanied with a 5.5 eV absorption. X-ray absorption spectroscopy and many-electron theory are combined to describe symmetries and degeneracies for O-vacancy bonding defects. These include comparisons with remote plasma-deposited non-crystalline SiO2 on Si substrates with SiON interfacial layers. Three different properties of remote plasma GeO2 films are addressed comparisons between (i) conduction band and band edge states of GeO2 and SiO2, and (ii) electronic structure of O-atom vacancy defects in GeO2 and SiO2, and differences between (iii) annealing of GeO2 films on Ge substrates, and Si substrates passivated with SiON interfacial transition regions important for device applications.