Interface diffusion and chemical reaction of PZT layer/Si (111) sample during the annealing treatment in air

The interface diffusion and chemical reaction between a PZT (PbZrxTi1-xO3) layer and a Si(111) substrate during the annealing treatment in air have been studied by using XPS (X-Ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy). The results indicate that the Ti element in the PZT precursor reacted with residual carbon and silicon, diffused from the Si substrate, to form TiCx, TiSix species in the PZT layer during the thermal treatment. A great interface diffusion and chemical reaction took place on the interface of PZT Si also. The silicon atoms diffused from silicon substrate onto the surface of PZT layer. The oxygen atoms, which came from air, diffused into silicon substrate also and reacted with Si atoms to form a SiO2 interlayer between the PZT layer and the Si (111) substrate. The thickness of SiO2 interlayer was proportional to the square root of treatment time. The formation of the SiO2 interlayer was governed by the diffusion of oxygen in the PZT layer at low annealing tempera     

In situ auger electron spectroscopy study of atomic layer deposition: growth initiation and interface formation reactions during ruthenium ALD on Si-H, SiO2, and HfO2 surfaces

Growth initiation and film nucleation in atomic layer deposition (ALD) is important for controlling interface composition and achieving atomic-scale films with well-defined composition. Ruthenium ALD is studied here using ruthenocene and oxygen as reactants, and growth initiation and nucleation are characterized on several different growth surfaces, including SiO2, HfO2, and hydrogen terminated silicon, using on-line Auger electron spectroscopy and ex-situ X-ray photoelectron spectroscopy. The time needed to reach the full growth rate (typically approximately 1 A per deposition cycle) is found to increase as the surface energy of the starting surface (determined from contact angle measurements) decreased. Growth starts more readily on HfO2 than on SiO2 or Si-H surfaces, and Auger analysis indicates distinct differences in surface reactions on the various surfaces during film nucleation. Specifically, surface oxygen is consumed during ruthenocene exposure, so the nucleation rate will depend on the availability of oxygen and the energetics of surface oxygen bonding on the starting substrate surface.     

V2O5/SiO2催化剂的异丁烷选择氧化反应性能

 采用溶胶－凝胶法和浸渍法制备了V2O5／SiO2催化剂,并用XRD,IR,TPD和活性评价等手段对催化剂的表面构造、化学吸附性能和异丁烷选择氧化反应性能进行了研究．结果表明：催化剂表面由Lewis碱位V＝O双键的端氧和Lewis酸位V5＋构成,异丁烷分子主要通过甲基中的H双位吸附在催化剂表面的Lewis碱位上,异丁烯分子可通过甲基的H吸附在催化剂表面的Lewis碱位,也可通过C＝C双键吸附在催化剂表面的Lewis酸位上．在常压条件下,异丁烷选择氧化产物主要有异丁烯、甲基丙烯醛和甲基丙烯酸,其中深度氧化产物CO2主要由通过C＝C吸附的异丁烯继续反应生成．     

具有辐射聚合能力的HfO2/SiO2溶胶-凝胶玻璃的制备及其X射线光刻性能研究

采用溶胶-凝胶方法制备了一种新颖的具有辐射聚合能力的HfO2/SiO2凝胶薄膜. 并采用X射线作曝光光源对薄膜进行了曝光, 通过FTIR的测试, 分析了薄膜曝光前后的结构变化. 结果表明, 该材料具有良好的辐射聚合能力. 采用XPS分析了薄膜的成分, 并证实了Hf元素的存在. 用椭偏仪测试了薄膜的折射率, 结果证实, 加入HfO2提高了体系的折射率. 利用其辐射聚合能力, 采用X射线通过掩模板进行曝光, 利用曝光部分与未曝光部分在溶剂中的溶解度差, 在薄膜上制备了高为0.8 μm、周期为1 μm的衍射光栅, 进一步证实了材料具有良好的辐射聚合能力.     

MoO3/SiO2催化剂的异丁烷选择氧化反应性能

分别采用浸渍法和溶胶－凝胶法制备了MoO3/SiO2催化剂，用XRD，TPR，IR，TPD和活性评价等手段对催化剂的影响，晶格氧活泼性，化学吸附性能和异丁烷选择氧化反应性能进行了研究。结果表明，催化剂表面由Lewis碱位Mo=M,Mo-O-Mo中的晶格氧和Lewis酸位Mo^6 构成，在MoO3/SiO2催化剂上，异丁烷主要通过甲基的H双位吸附在表面的Lewis碱位Mo=O上；在常压条件下，异丁烷选择氧化产物主要为异丁烷，甲基丙烯醛和甲基丙烯酸，其中深度氧化产物CO2主要由吸附的异丁烯继续反应生成；采用溶胶－凝胶法制备的MoO3/SiO2催化剂，可得到较高的异丁烷转化率和含氧有机物选择性。     

异丁烷部分氧化V-P-O/SiO2催化剂的研究

The V2O5/SiO2 and V2O5-P2O5/SiO2 catalysts were prepared by the Sol-gel method. The surface composition,structure,chemisorption and reactivity of the catalysts were systematically studied by using the techniques of XRD,TPR,IR,TPD and icro-reactor. The results showed that the active component was dispersed uniformly on the surface of amorphous SiO2 . There existed Lewis base sites（V=O and V-O-V）and Lewis acid sites （Vn+）on the surface of these catalysts. An addition of PO43- could lower the activity of surface terminal oxygen of Lewis base sites V=O. Iso-butane could chemisorbed on surface terminal oxygen of Lewis base sites V=O by one or two H atoms in -CH3 to form molecular adsorption states. Reaction products of i-C4H10 on the V-P-O/SiO2 catalyst were mainly i-C4H8,MAL,MAA and COx . Conversion of i-C4H10 was 5% and selectivity of partial oxidation products is above 72% at 300℃. The addition of PO43- could improve the selectivity of partial oxidation products on the VSiO catalyst because PO43- could reduce the activity of lattice oxygen in V = O bond,and weaken the adsorption intensity of i-C4H10 .     

Matrixreaktionen von SiO. IR-spektroskopischer Nachweis der Molekeln SiO2 und OSiCl2

Matrix Reactions of SiO. IR-spectroscopic Identification of the Molecules SiO₂ and OSiCl₂ SiO evaporated from Knudsen cell reacts in argon matrix with atomic oxygen generated by microwave excitation to molecular SiO₂. Bands at 1400 cm^?1 in the IR matrix spectrum are assigned to the ν₃-vibration of molecules Si¹⁶O₂, Si¹⁶O¹⁸O, and Si¹⁸O₂. In an argon matrix SiO can reach with Cl₂ by excitation of a high pressure mercury lamp to OSiCl₂. Isotopic splitting (¹⁶O/¹⁸O, ²⁸Si/²⁹Si, ³⁵Cl/³⁷Cl) and force constant calculations show that the observed frequencies can be assigned to a planar molecule OSiCl₂. The bending mode δ (SiCl₂) could not be observed. The force constant f(SiO) is 9. 10² N m^?1 for SiO₂ and OSiCl₂. According to the SIEBERT rule this valence force constant is expected for a double bond between silicon and oxygen.     

Scanning photoemission spectromicroscopic study of 4-nm ultrathin SiO(3.4) protrusions probe-induced on the native SiO(2) layer

Atomic force microscopy probe-induced large-area ultrathin SiO(x) (x ≡ O/Si content ratio and x > 2) protrusions only a few nanometers high on a SiO(2) layer were characterized by scanning photoemission microscopy (SPEM) and X-ray photoemission spectroscopy (XPS). SPEM images of the large-area ultrathin SiO(x) protrusions directly showed the surface chemical distribution and chemical state specifications. The peak intensity ratios of the XPS spectra of the large-area ultrathin SiO(x) protrusions provided the elemental quantification of the Si 2p core levels and Si oxidation states (such as the Si(4+), Si(3+), Si(2+), and Si(1+) species). The O/Si content ratio (x) was evidently determined by the height of the large-area ultrathin SiO(x) protrusions.     

Reactivity of molecularly chemisorbed oxygen on a Au/TiO2 model catalyst

We present results of an investigation into the reactivity of molecularly chemisorbed oxygen with CO on a Au/TiO2 model catalyst at 77 K. We previously discovered that exposing the model catalyst sample to a radio-frequency-generated plasma jet of oxygen results in co-population of both atomically and molecularly chemisorbed oxygen species on the sample. We tested the reactivity of the molecularly chemisorbed oxygen by comparing the CO2 produced from a sample populated with both species to the CO2 produced from a sample that has been cleared of molecularly chemisorbed oxygen employing collision-induced desorption. Samples that are populated with both species consistently result in greater CO2 produced than samples with only atomic oxygen. We interpret this result to indicate that molecularly chemisorbed oxygen on the sample can directly participate in the CO oxidation reaction. The reactivity of molecularly chemisorbed oxygen has been investigated for five different gold coverages (0.5, 0.75, 1, 1.25, and 2 ML), and we observe that there is a greater fractional difference in the CO2 produced (difference between sample populated with both molecularly and atomically adsorbed oxygen and sample populated solely with atomically adsorbed oxygen) for the 1 ML Au coverage than for the other coverages for equivalent oxygen plasma-jet exposures. However, it is not possible to unambiguously conclude that this observation is directly related to a particle size effect on the chemistry since the absolute O(2,a) and O(a) content on the various surfaces is different for all the coverages studied because of the plasma-jet technique that we employed for populating the surfaces with oxygen. Unfortunately, this precludes a direct comparison of the reactivity of molecular oxygen in the carbon monoxide oxidation reaction as a function of gold coverage and hence particle size.     

Nanometer-scale wetting of the silicon surface by its equilibrium oxide

Despite the extremely broad technical applications of the Si/SiO2 structure, the equilibrium wetting properties of silicon oxide on silicon are poorly understood. Here, we produce new results in which a solid-state buffer method is used to systematically titrate oxygen activity about the Si/SiO2 coexistence value. The equilibrium morphology at the Si(001) surface over >8 decades of PO2 about coexistence is revealed to be a uniform sub-stoichiometric SiOx film of sub-nanometer thickness, coexisting with secondary island structures which coarsen with annealing time. A new thermodynamic method using chemical potential to stabilize and control surficial oxides in nanoscale devices is suggested.     

Effects of Pt diffusion barrier layer on the interface reaction and electric properties of PZT film/Si (111) sample

The effects of the Pt diffusion barrier layer on the interface diffusion and reaction, crystallization, dielectric and ferroelectric properties of the PZT/Si(111) sample have been studied using XPS, AES and XRD techniques. Hie results indicate that the Pt diffusion barrier layer between the PZT layer and the Si substrate prohibits the formation of TiCx TiSix and SiO2 species in the PZT layer. The Pt barrier layer also completely interrupts the diffusion of Si from the Si substrate into the PZT layer and impedes the diffusion of oxygen from air to the Si substrate greatly. Although the Pt layer can not prevent completely the diffusion and reaction between oxygen and silicon, it can prevent the formation of a stable SiO2 interface layer on the interface of PZT/Si. The Pt layer reacts with silicon to form PtSix species on the interface of Pt/Si, which can intensify the chemical binding strength between the Pt layer and the Si substrate. To play a good role as a diffusion barrier layer, the Pt barrier layer     

Electric field control and analyte transport in Si/SiO2 fluidic nanochannels

This article presents an analysis of the electric field distribution and current transport in fluidic nanochannels fabricated by etching of a silicon chip. The channels were overcoated by a SiO2 layer. The analysis accounts for the current leaks across the SiO2 layer into the channel walls. Suitable voltage biasing of the Si substrate allows eliminating of the leaks or using them to modify the potential distribution of the fluid. Shaping the potential in the fluid can be utilized for solute focusing and separations in fluidic nanochannels.     

Low-temperature reduction of NO(2) on oxidized Mo(110)

The reactions of nitrogen dioxide (NO(2)) were investigated on oxidized Mo(110) containing both chemisorbed oxygen and a thin film oxide. NO(2) reacts on both oxidized Mo(110) surfaces via a combination of reversible adsorption and reduction to NO, N(2), and trace amounts of N(2)O below 200 K. On the surface containing chemisorbed O, there is some complete dissociation of NO(2) to yield N(a) and O(a). N(2) forms at high temperatures through atom combination. On both surfaces, NO is the predominant product of NO(2) reduction. However, the chemisorbed layer which has a low oxidation state, and hence a greater capacity to accept oxygen, more effectively reduces NO(2). The selectivity for N(2) formation over N(2)O is greater for NO(2) as compared with NO on both surfaces studied. The selectivity changes are largely attributed to an increase in the concentration of Mo=O species and a change in the distribution of oxygen on the surface. Notably, more oxygen, in particular Mo=O moieties, is deposited by NO(2) reaction than by O(2) reaction, indicating that NO(2) is a stronger oxidant. The fact that there are several N-containing species on the surface at low temperatures may also affect the product distribution. On both surfaces, N(2)O(4), NO(2), and NO are identified by infrared spectroscopy upon adsorption at 100 K. All N(2)O(4) desorbs by 200 K, leaving only NO(2) and NO on the surface. Infrared spectroscopy of NO(2) on (18)O-labeled surfaces provides evidence for oxygen transfer or exchange between different types of sites even at low temperatures.     

Mo-P-O/SiO2催化剂上的异丁烷选择氧化反应

 采用溶胶－凝胶法制备了MoO3／SiO2和Mo－P－O／SiO2催化剂，用X射线衍射、红外光谱、程序升温还原、程序升温脱附和活性评价等手段研究了催化剂的表面结构、晶格氧活泼性、化学吸附性能以及异丁烷选择氧化反应性能．结果表明，活性组分在催化剂表面分散较好；异丁烷吸附在催化剂表面Lewis碱位的MoO端氧上形成分子吸附态；MoO3／SiO2和Mo－P－O／SiO2两种催化剂对异丁烷选择氧化都有较好的选择性，将PO3－4引入到MoO3／SiO2催化剂中可提高含氧化合物的选择性     

C(膜)/Si(SiO2 )(纳米微粒)/C(膜)热处理的形态及结构分析

用直流辉光溅射+真空镀膜法制备了一种新型结构的硅基纳米发光材料- C(膜)/Si(SiO2)(纳米微粒)/C(膜)夹层膜,并对其进行了退火处理.用TEM、 SEM、 XRD和XPS对其进行了形态结构分析.TEM观察表明: Si(SiO2)纳米微粒基本呈球形,粒径在30 nm左右.SEM观察表明: 夹层膜样品总厚度约为50 μm,膜表面比较平整、致密.400℃退火后,样品表面变得凹凸不平,出现孔状结构; 650℃退火后,样品表面最平整、致密且颗粒均匀.XRD分析表明:制备出的夹层膜主要由SiO2和Si组成,在C原子的还原作用和氧气的氧化作用的共同作用下, SiO2和Si的含量随加热温度的升高而呈现交替变化: 400℃时, C的还原作用占主导地位, SiO2几乎全部被还原成了Si,此时Si含量最高; 400～650℃时,氧化作用占主导地位, Si又被氧化成SiO2, Si含量降低, SiO2含量逐渐上升,在650℃达到最高.XPS分析表明: 在加热过程中, C原子逐渐扩散进入Si(SiO2)微粒层,在650℃与Si反应生成了新的SiC.     

Grazing incidence-X-ray fluorescence spectrometry for the compositional analysis of nanometer-thin high-kappa dielectric HfO2 layers.

In future microelectronic devices, SiO2 as a gate dielectric material will be replaced by materials with a higher dielectric constant. One such candidate material is HfO2. Thin layers are typically deposited from ligand-containing precursors in chemical vapor deposition (CVD) processes. In the atomic layer deposition (ALD) of HfO2, these precursors are often HfCl4 and H2O. Obviously, the material properties of the deposited films will be affected by residual ligands from the precursors. In this paper, we evaluate the use of grazing incidence--and total reflection-X-ray fluorescence spectrometry (GI-XRF and TXRF) for Cl trace analysis in nanometer-thin HfO2 films deposited using ALD. First, the results from different X-ray analysis approaches for the determination of Hf coverage are compared with the results from Rutherford backscattering spectrometry (RBS). Next, we discuss the selection of an appropriate X-ray excitation source for the analysis of traces within the high-kappa: layers. Finally, we combine both in a study on the accuracy of Cl determinations in HfO2 layers.     

Kinetics of CO oxidation on high-concentration phases of atomic oxygen on Pt(111)

Temperature-programmed reaction spectroscopy (TPRS) and direct, isothermal reaction-rate measurements were employed to investigate the oxidation of CO on Pt(111) covered with high concentrations of atomic oxygen. The TPRS results show that oxygen atoms chemisorbed on Pt(111) at coverages just above 0.25 ML (monolayers) are reactive toward coadsorbed CO, producing CO(2) at about 295 K. The uptake of CO on Pt(111) is found to decrease with increasing oxygen coverage beyond 0.25 ML and becomes immeasurable at a surface temperature of 100 K when Pt(111) is partially covered with Pt oxide domains at oxygen coverages above 1.5 ML. The rate of CO oxidation measured as a function of CO beam exposure to the surface exhibits a nearly linear increase toward a maximum for initial oxygen coverages between 0.25 and 0.50 ML and constant surface temperatures between 300 and 500 K. At a fixed CO incident flux, the time required to reach the maximum reaction rate increases as the initial oxygen coverage is increased to 0.50 ML. A time lag prior to the reaction-rate maximum is also observed when Pt oxide domains are present on the surface, but the reaction rate increases more slowly with CO exposure and much longer time lags are observed, indicating that the oxide phase is less reactive toward CO than are chemisorbed oxygen atoms on Pt(111). On the partially oxidized surface, the CO exposure needed to reach the rate maximum increases significantly with increases in both the initial oxygen coverage and the surface temperature. A kinetic model is developed that reproduces the qualitative dependence of the CO oxidation rate on the atomic oxygen coverage and the surface temperature. The model assumes that CO chemisorption and reaction occur only on regions of the surface covered by chemisorbed oxygen atoms and describes the CO chemisorption probability as a decreasing function of the atomic oxygen coverage in the chemisorbed phase. The model also takes into account the migration of oxygen atoms from oxide domains to domains with chemisorbed oxygen atoms. According to the model, the reaction rate initially increases with the CO exposure because the rate of CO chemisorption is enhanced as the coverage of chemisorbed oxygen atoms decreases during reaction. Longer rate delays are predicted for the partially oxidized surface because oxygen migration from the oxide phase maintains high oxygen coverages in the coexisting chemisorbed oxygen phase that hinder CO chemisorption. It is shown that the time evolution of the CO oxidation rate is determined by the relative rates of CO chemisorption and oxygen migration, R(ad) and R(m), respectively, with an increase in the relative rate of oxygen migration acting to inhibit the reaction. We find that the time lag in the reaction rate increases nearly exponentially with the initial oxygen coverage [O](i) (tot) when [O](i) (tot) exceeds a critical value, which is defined as the coverage above which R(ad)R(m) is less than unity at fixed CO incident flux and surface temperature. These results demonstrate that the kinetics for CO oxidation on oxidized Pt(111) is governed by the sensitivity of CO binding and chemisorption on the atomic oxygen coverage and the distribution of surface oxygen phases.     

In situ surface oxidation study of a planar Co/SiO2/Si(100) model catalyst with nanosized cobalt crystallites under model Fischer-Tropsch synthesis conditions

The oxidation of nanosized metallic cobalt to cobalt oxide during Fischer-Tropsch synthesis (FTS) has long been postulated as a major deactivation mechanism. In this study a planar Co/SiO(2)/Si(100) model catalyst with well-defined cobalt crystallites, close to the threshold value reported for oxidation in the literature (4-10 nm), was prepared by the spin coating method. The planar Co/SiO(2)/Si(100) model catalyst was characterized with atomic force microscopy, X-ray photoelectron spectroscopy, and Rutherford backscattering. The surface oxidation behavior of the nanosized metallic cobalt crystallites of 4-5 nm was studied using in situ near-edge X-ray absorption fine structure under model FTS conditions, i.e., H(2)/H(2)O = 1, P(Total) = 0.4 mbar, and 150-450 degrees C. No surface oxidation of metallic cobalt was observed under these model FTS conditions over a wide temperature range, i.e., 150-400 degrees C.     

Oxidation pattern of small silicon oxide clusters: structures and stability of Si6On (n = 1-12)

We have performed systematic ab initio calculations to study the structures and stability of Si(6)O(n)() clusters (n = 1-12) in order to understand the oxidation process in silicon systems. Our calculation results show that oxidation pattern of the small silicon cluster, with continuous addition of O atoms, extends from one side to the entire Si cluster. Si atoms are found to be separated from the pure Si cluster one-by-one by insertion of oxygen into the Si-O bonds. From fragmentation energy analyses, it is found that the Si-rich clusters usually dissociate into a smaller pure Si clusters (Si(5), Si(4), Si(3), or Si(2)), plus oxide fragments such as SiO, Si(2)O(2), Si(3)O(3), Si(3)O(4), and Si(4)O(5). We have also studied the structures of the ionic Si(6)O(n)(+/-) (n = 1-12) clusters and found that most of ionic clusters have different lowest-energy structures in comparison with the neutral clusters. Our calculation results suggest that transformation Si(6)O(n)+(a) + O --> Si(6)O(n+1)+(a) should be easier.     

Spectroscopic and electrical properties of SiO2 films prepared by simple and cost effective sol-gel process

Amorphous SiO2 thin films were prepared on glass and silicon substrates by cost effective sol-gel method. Tetra ethyl ortho silicate (TEOS) was used as the precursor material, ethanol as solvent and concentrated HCl as a catalyst. The films were characterized at different annealing temperatures. The optical transmittance was slightly increased with increase of annealing temperature. The refractive index was found to be 1.484 at 550 nm. The formation of SiO2 film was analyzed from FT-IR spectra. The MOS capacitors were designed using silicon (100) substrates. The current-voltage (I-V), capacitance-voltage (C-V) and dissipation-voltage (D-V) measurements were taken for all the annealed films deposited on Si (100). The variation of current density, resistivity and dielectric constant of SiO2 films with different annealing temperatures was investigated and discussed for its usage in applications like MOS capacitor. The results revealed the decrease of dielectric constant and increase of resistivity of SiO2 films with increasing annealing temperature.