Substrate sequential deposition

The initial step in the preparation of the mixed-metal films consisted of vapor deposition, one metal at a time, onto a refractory substrate sequential deposition was necessary in order to track the doser-calibration conditions. Alloy formation was then carried out by a high-temperature treatment. Figme 5 shows LEISS spectra of a Mo(llO) substrate on which ten monolayers of a Pt-Co mixtrrre, deposited in a 1 4 monolayer ratio, was heated to selected temperatures. In Fig. 5a, 2 ML of Pt were deposited first, followed by 8 ML of Co in Fig. 5b, the reverse was done in which 8 ML of Co were generated first. 

In a similar way, electrochemistry may provide an atomic level control over the deposit, using electric potential (rather than temperature) to restrict deposition of elements. A surface electrochemical reaction limited in this manner is merely underpotential deposition (UPD see Sect. 4.3 for a detailed discussion). In ECALE, thin films of chemical compounds are formed, an atomic layer at a time, by using UPD, in a cycle thus, the formation of a binary compound involves the oxidative UPD of one element and the reductive UPD of another. The potential for the former should be negative of that used for the latter in order for the deposit to remain stable while the other component elements are being deposited. Practically, this sequential deposition is implemented by using a dual bath system or a flow cell, so as to alternately expose an electrode surface to different electrolytes. When conditions are well defined, the electrolytic layers are prone to grow two dimensionally rather than three dimensionally. ECALE requires the definition of precise experimental conditions, such as potentials, reactants, concentration, pH, charge-time, which are strictly dependent on the particular compound one wants to form, and the substrate as well. The problems with this technique are that the electrode is required to be rinsed after each UPD deposition, which may result in loss of potential control, deposit reproducibility problems, and waste of time and solution. Automated deposition systems have been developed as an attempt to overcome these problems. 

An example "double heterostructure" OLED shown in Figure 7c uses an ITO coated glass substrate, upon which a hole transporting layer, typically composed of a tertiary amine (eg, IV,IV-biphenyl-A IV7-bis(3-methylphenyl)l-l biphenyl-4,4 diamine, abbreviated TPD), a thin film of an emissive material such as aluminum-8-hydroxyquinoline(Alq3) and an electron-transporting layer (often an oxidiazole derivative) are sequentially deposited in vacuum (Fig. 

The multilayer sensor structure consists of cermet and polymer based layers sequentially deposited on a 96% alumina ceramic substrate using a thick film screen printing process. The cermet layers are of ceramic-metal composition which require firing at a temperature of 850°C and the polymer layers are cured at temperatures below 100°C. Layout of this multilayer sensor structure is shown in Figure 1. 

The Cu-Sn specimens for experiments were prepared by sequential deposition of copper (560 nm) and tin (200 or 560 nm) films on quartz discs under vacuum. To prevent any reaction during the specimen preparation, a tin film was deposited after cooling the substrate with a copper film down to the liquid nitrogen temperature (for more detail, see Ref. 64). 

Solvent/lithium interfaces are formed by sequentially depositing lithium onto the clean substrate and, following rapid AES characterization, condensing the solvent onto it, as shown schematically in Figure 5. An array of techniques, including XPS, AES, TPD and FTIR, are then used to examine their electronic, structural and vibrational properties. Additional insight into the effects induced by Li was also obtained from studies of the behavior of THF and PC condensed on bare, clean, nominally unreactive substrates such as Ag and Au. 

Photoreceptors are prepared by the sequential application of the various layers onto a web or drum substrate. Vapor-deposition methods can be used for some pigments. Most layers, however, are coated from solution or dispersions in organic solvents. Wicks (1986) has reviewed film formation from polymer solutions. The choice of solvent is determined by such factors as solubility, evaporation rates, surface tension, toxicity, as well as environmental... 

Figure 9. Schematic fabrication of LbL films comprising poly(vinylsulfonic acid) (PVS)and PAMAM-Au. The sequential deposition of LbL multilayers was carried out by immersing the substrate alternately into (a) PVS and (b) PAMAM-Au solutions for 5 min per step (c) After deposition of 3 bilayers, an ITO-PVS/PAMAM-Au)3 CoHCF electrode was prepared by potential cycling (d) The enzyme immobilization to produce ITO-PVS/PAMAM-Au)3 CoHCF-GOx was carried out in a solution containing BSA, glutaraldehyde and GOx (Adapted from Ref.[124])...

Fig. 20. a) In the quaternary masking scheme, deposition is carried out using a series of n different masks which subdivide the substrate into a series of nested quadrants. Each mask is used in four sequential deposition steps with a 90 rotation of the mask in each step, generating up to 4" compositions in An deposition steps, b) Photograph of the 1024-membered library (deposited on a Si substrate with an area of 2.54 x 2.54 cm ) under ambient light (top) and UV... 

The process of formation of a multilayer film on the ITO coated glass from sequential addition of PABA/RNA bilayers was observed with UV-Vis Spectroscopy as shown in Figure 3.34. The film growth observed with the deposition of additional bilayers suggests that the multilayer formation of PABA/RNA is reproducible with sequential deposition. All spectra exhibit an intense and sharp peak attributed to the w-tt and bipolaron band transitions. The bipolaron absorption band at 800 nm, associated with complexation of RNA with PABA, increases linearly with the number of PABA/RNA bilayers (Figure 3.34 inset). The linear relationship between absorbance and the number of deposited bilayers indicates that the deposition was reproducible from layer to layer, i.e., the amount of PABA adsorbed in each bilayer was the same. In addition to these results, multilayer formation was observed with ellipsometric and X-ray photoelectronic spectroscopy. The linear increase in film thickness with number of PABA/RNA bilayers was observed using ellipsometry. The average thickness of the PABA/RNA bilayer built up on a silicon substrate was approximately 10 nm. Additionally, X-ray photoelectron... 

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