Dependence on Preparation Condition

To study the influence of the preparation conditions on the interface properties, a number of different interfaces have been prepared. Details of the preparation and the determined valence band offsets are listed in Table 4.2. The experiments include not only both deposition sequences, but also interfaces of Al-doped ZnO films, which have been conducted to elucidate the role of the undoped ZnO film as part of the Cu(In,Ga)Se2 solar cell. Details of the experimental procedures and a full set of spectra for all experiments are given in [70]. Table 4.2 includes a number of interfaces between substrates of undoped ZnO films and evaporated CdS layers (ZOCS A-D). In a recent publication [90] different values were given for the valence band offsets, as the dependence of BEvb(CL) on the deposition conditions was not taken into account in this publication. 

The experimentally determined valence band offsets span quite a large range from A Vb = 0.84 — 1.63 eV. The variation of 0.8 eV is considerably larger than the experimental uncertainty, which is 0.1 eV for most experiments with only a few exceptions. Experiments with a larger uncertainty have been omitted. 

The experimental procedure for the determination of the valence band offsets directly relies on the core level to valence band maximum binding energy differences BEvb(CL) as described in Sect. 4.1.3 and Fig. 4.3. The corresponding values for the Zn2p3/2 and the Cd3ds/2 core level are therefore included in Table 4.2. These values are determined directly from the respective interface experiments. With two exceptions (CSZA-E and ZACS-C), the values for the Zn2p3/2 core level show the same dependence on deposition conditions as given in Fig. 4.15. For these two exceptions, also the Fermi level position 

The experimental result of Ruckh et al. [102], which is obtained for comparable preparation conditions, deviates from the general behavior observed in our own data. The reason for this deviation is not clear. 

The interfaces prepared by sputter deposition of ZnO (filled square) or (Zn,Mg)0 (filled triangles) exhibit a valence band offset of AEyb = 1.2 eV. The ZnO and (Zn,Mg)0 films were prepared at room temperature in pure Ar and therefore exhibit a large disorder and a large BEve(Zn 2p3/2)- Compared with the interface with reverse deposition sequence, the offset is 0.35 eV larger. This indicates a rather strong influence of the deposition sequence on the band alignment at the CdS/ZnO interface, which is most likely related to the amorphous nucleation layer when ZnO is deposited onto CdS. 

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Note that scaling exponents depend on preparative conditions. ... 

A large set of results obtained in recent years for various carotenoids (see, e.g., Simonyi et al. (2003) for review) suggests that planarity of the carotenoid molecule is crucial for aggregation. This hypothesis is supported by the observation that zeaxanthin and astaxanthin, both fairly planar molecules, form aggregates more readily than other carotenoids. Moreover, zeaxanthin and astaxanthin are the only two carotenoids studied so far that can, depending on preparation conditions, form exclusively either H- or J-aggregates (Billsten et al. 2005, Kopsel et al. 2005, Avital... 

The overall yield is essentially 100 by any of the preparation methods, but the physical characteristics of the ion exchangers are dependent on preparation conditions. For example, sodium titanate prepared by Eqs. la and lb with hydrolysis in one liter of water per mole of Ti(OC3H7)4 has a bulk density of 0.U5 g/cm3 and a specific surface area of lO-UO m /g. The same material prepared by Eqs. la and lb and hydrolyzed in a solution of 100 ml of water in 1000 ml of acetone for each mole of Ti(OC2H7)4 has a bulk density of 0.35 g/cm3 and a specific surface area of 200-UOO m /g. In all cases, the materials consist of agglomerates of 50-100 A particles with the degree of aggregation of the particles determining both the bulk density and surface area. 

FIGURE 2.2 These honeycomb units further assemble into larger structures that can include worms, spheres, ovals, and so on, depending on preparative conditions. SOURCE Courtesy of Victor S. Lin, Iowa State University. 

The main chapters (4-14) are concerned with the preparative methods. For the majority of oxides particularly hematite and goethite more than one preparative method is described. Properties such as crystal morphology and surface area frequently depend on preparative conditions and a selection of methods is presented to enable a range of oxides with specific characteristics to be produced. The production of so-called monodis-perse Fe oxides, i. e. products with a rather narrow particle size distribution, is also included. 

The surface of silicon in air is always covered with a very thin oxide film. Table 2.10 shows that the thickness of native oxide formed on the surface of silicon after several days in air varies from 5 to 20 A depending on preparation conditions. Such a large variation in the thickness of native oxide indicates the great sensitivity of the surface reactivity to minute variations of environmental and material conditions. 

Salts formed with the metalloorganic cations tetraphenylphosphonium and tetra-phenylarsonium can be prepared as relatively large crystals by electrochemical methods and are not air sensitive, contrary to the other monoanionic fullerides mentioned above as a consequence, they have been extensively studied by several methods [40 4]. The composition of the crystals is always two counterions to one fulleride monoanion, and charge neutrality is preserved by one halide ion (Cl , Br or I ) per fulleride ion. The type of the halide ion depends on preparation conditions and can be homogeneous or a mixture of two kinds of halides. This fact introduces an additional disorder into the structure, but as we will see, its impact is relatively weak. 

Si Al ratio of the outer layers (ca. 10 A) of the zeolite crystals. The extent to which the surface composition differs from the bulk composition appears to depend on preparation conditions, and all three possible situations (silicon rich surface, silicon deficient surface and surface composition equal to bulk composition) have been reported (refs. 12-14). Variations in aluminium distribution have also been probed by high resolution scanning electron microscopy (ref. 15) and energy dispersive X-ray analysis (ref. 16). 

VOCl2 vox 2 0.01 optical properties strongly dependent on preparation conditions... 

In the surface mirror, modern technology has enabled an improved method of construction the reflecting metal film is coated under high vacuum on the side on which radiation is incident. Various metals are applied for the different types of surface mirrors. Their reflectance is shown in Fig.26 of Chapter 8. The most frequently used metal for surface mirrors is aluminium. Its reflectance as a function of wavelength and its dependence on preparation conditions is shown in Fig.l 1. 

TlgO, brown to black, depending on preparative conditions. M.p. 71 rC under 1 atm. of O3 Insoluble in water, d (x-ray) 10.11. C sesquioxide structure type. 

Black, with varying air sensitivity, depending on preparative conditions. Almost completely resistant to and dilute acids. Decomposed by concentrated and HNQg. Insoluble in organic... 

The extent to which the carrier mobilities depend on preparation conditions is not well understood. One reason for this is that, unlike optical measurements, for example, the time-of-flight measiu ments can only be made on material for which the carrier lifetimes against deep trapping are sufficiently long for the charges to traverse the sample with a reasonable field, as pointed out earlier. This feature of the time-of-ffight experiment has been exploited by Street (1982) and Steemers et al. (1983), who have used the technique to explore the electronic properties of defects and the influence of preparation conditions on defect density. 

In general, the particle sizes found for these AuNPs and related metal nanoparticles may vary between about 2 to 100 nm, depending on preparative conditions, with most examples falling in the large-diameter range. 

S.P. Nunes, F. Galembeck, N. Barelu, Cellulose Acetate Membranes for Osmo-sedimentation Performance and Morphological Dependence on Preparation Conditions. Pdymer 27 (1986) 937 943. 

Table 1 illustrates typical data for a number of different materials. They are only approximate, for the values are dependent on preparation conditions, and proximity to Curie point etc. The single-crystal materials are not suitable,in that they are only available in bulk form. The ceramic materials have a high value of p,but this is offset by their large values of relative permittivity. The polymeric materials are of some... 

Depending on preparation conditions, liposomes generated from solvent-based proliposomes have been danonstrated to be OLVs [49], MLVs [64], a mixture of MLVs and OLVs [65,66], or, under static conditions, LUVs with the occasional presence of MLVs [67],... 

In conclusion it can be said that, even with the above-mentioned drawbacks, the ASYNNNI model has considerably helped to understand the difficulties of the superstructure problem. The delicate balance resulting from eqs. (3) and (4) indicates the strong dependence on preparation conditions to be expected. The complexity of superstructures dictates extremely slow cooling and low-temperature annealing. Here, however, the freezing of the mobility of oxygen puts a natural limitation. 

Hydrous titanium oxides are important ion exchangers with different selectivities to different ions, exhibiting certain desirable catalytic and adsorptive properties [1-6]. One particular advantage to these hydrous oxides is their good thermal and radiation stabilities. Studies undertaken by a number of workers have shown that hydrous titanium oxide has ion exchange characteristics that are highly dependent on preparative conditions[7-8], and that the titania surface displayed amphoteric characteristics [9-10]. 

Many metal nanoparticles can be prepared by several different reduction methods. For example, Mayer and Mark prepared Ag, Pd, Au, and Pt nanoparticles in solution using alcohols, KBH4, and photochemical reduction, with amphiphilic diblock copolymers as protection agents (136). The particle sizes were in the 1- to 7-nm range, depending on preparation conditions. 

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