Titanium thin films

Methods have been developed for fabrication of the highly-ordered titania nanotuhe arrays from titanium thin films atop a substrate compatible with photolithographic processing, notably silicon or FTO coated glass [104]. The resulting transparent nanotuhe array structure, illustrated in Fig. 5.16, is promising for applications such as anti-reflection coatings and dye sensitized solar cells (DSSCs). Fig. 5.17 shows the typical anodization behavior of a 400 nm Ti thin film anodized at 10 V in an HE based electrolyte. Eor a fixed HE concentration, the dimensions of the tube vary with respect to... 

Mor GK, Varghese OK, Paulose M, Grimes CA (2005) Transparent highly-ordered Ti02 nanotube-arrays via anodization of titanium thin films. Adv Funct Mater 15 1291-1296... 

Usually the nanotube arrays have been made from a titanium thick film or foil, in which case the resulting nanotubes rest upon an underlying Ti substrate as separated by a barrier layer. The nanotube arrays have also been fabricated from a titanium thin film sputtered onto a variety of substrates, such as silicon and fluorine doped tin oxide (FTO) coated conductive glass. This extends the possibility for preparing technical catalysts by deposing a thin Ti layer over a substrate (a foam, for example) and then inducing the formation of the nanostructured titania film by anodic oxidation. ... 

Compounds 1-3 were briefly reported as precursors to titanium thin films. 16 26 28 The thermoanalytical studies conducted on these molecules gave contradictory results to those reported in the literature. We found that these molecules do decompose, but form non-volatile products in the precursor vessel.29 Consequently, the formation of CVD films seems to be more difficult than previously reported. Compounds 4 and 5 contain large amounts of chlorine atoms that can participate in the formation of the film or combine with hydrogen atoms so as to corrode the steel substrates. However, these compounds are relatively volatile,29 and 5 has been successfully used for CVD of titanium carbide.26,30-33 In order to maintain sufficient volatility but reduce the Cl content of the molecule, we have studied compound 6 which contains just one Cl atom. The TG behavior of 6 remains similar to that of 5. The TG curve of Figure 15.3 shows a high volatility of this compound between 523 K and 573 K, and its decomposition below 623 K. Compound 6 can therefore be considered as a good candidate precursor to titanium carbide thin films.29... 

JM. Steigerwald, R. JGutmann, S. P. Murarica Electrochemical Effect in the Chemical Mechanical Polishing of Ct ipm and Titanium Thin Film Used For Multilevel Interconnect Schemes , Proc. of lEEE-VMIC (1993) P.205... 

Therefore, the better capacities obtained from ntTi02 layers formed onto Si are attributed to the nature of Ti thin film. Compared with ntTi02 layers grown from mechanically polished Ti foils, anodization of titanium thin film obtained by physical vapor deposition (PVD) process leads to the formation of highty flat ntTi02 layer. Thus, we assume that the contact between the ntTi02 layers and the electrolyte is drastically improved. 

Premchand, Y. D., Djenizian, T, Vacandio, F, and Knauth, P. (2006). Fabrication of self-organized Ti02 nanotubes from columnar titanium thin films sputtered on semiconductor surfaces. Eiectrochem. Commun. 8, pp. 1840-1844. 

Cai K, Frant M, Bossert J, Hildebrand G, Liefeith K, Jandt KD. Surface functionalized titanium thin films zeta-potential, protein adsorption and cell proliferation. Colloids Surf B Biointerfaces 2006 50 1-8. 

Figure 9.19 Normalized integral passive dissolution kinetics for titanium thin films immersed in EDTA/SIE (simulated interstitial electrolyte) (a) real time data empirically fitted with two-phase logarithmic law relationship (b) a semiloga-rithmic plot of the data demonstrating the two-phase logarithm relationship. The correlation coefficient for the least-squares fit of the linear functions are given. (Healy and Ducheyne, 1992.)...

Fang, Y., Raghavan, S., 2004. Electrochemical investigations during the abrasion of aluminum/ titanium thin-film stacks in iodate-based slurry. J. Electrochem. Soc. 151, G878—G881. 

Also studied by XPS recently have been the measurement of energies of adhesion of aluminum and silicon on molybdenum [63], the ion-enhanced adhesion of nickel to glassy carbon [64], the effects of pretreatments on paint-metal adhesion [65], and the adhesion of titanium thin films to various oxide surfaces [66],... 

The various versions of inverse photoemission have been applied to purely basic problems, just as with UPS and ELS. Recent typical examples include the bonding of Hj on Ni (110) 3I4J the oxidation of a titanium thin film [315] the effects on Ht chemisorption of a monolayer of nickel on Cu (111) [316] unoccupied electronic structure in La2Cu04 [317] and in Bi2Sr2CaCu20g [318] and KRIPES studies of the Ge (113) (2x1) [319] and TiNo.8.1 (100) [320] surfaces. 

Case Study 1 - Titanium Oxidation States ON Titanium Thin Films and Bulk Surfaces... 

Titanium is a popular material in industrial and medical applications because of its high corrosion resistance and biocompatibility. These properties are enhanced by the formation of a protective passive oxide film which spontaneously forms on titanium surfaces [11-16], It has been shown that titanium oxide l er enhances the body s ability to incorporate the implant, and reduces the risk of rejection [11, 15, 17-26], In this study. X-ray photoelectron spectroscopy was used to investigate the chemical compositions of titanium thin films on glass and silicon, and to compare these to the surface compositions of bulk titanium disks after different polishing treatments. 

Ivanova, EP Truong, VK Wang, JY Bemdt, CC Jones, RT Yusuf, II Peake, I Schmidt, HW Fluke, C Barnes, D Crawford, RJ. Impact of Nanoscale Ronghness of Titanium thin films surfaces on Bacterial Retention. Langmuir, 2009, in press. 

Cai, K Muller, M Bossert, J Rechtenbach, A Jandt, KD. Surface structure and composition of flat titanium thin films as a function of film thickness and evaporation rate. Applied Surface Science, 2005, 250,252-267. 

Jeyachandran, YL Karunagaran, B Narayandass, SK Mangalaraj, D Jenkins, TE Martin, PJ. Properties of titanium thin films deposited by dc magnetron sputtering. Materials Science and Engineering A, 2006,431,277-284. 

N. Ozkucur, C. Wetzel, F. Hollstein, E. Richter, R.H. Funk, T.K. Monsees, Physical vapor deposition of zirconium or titanium thin films on flexible polyurethane highly support adhesion and physiology of human endothelial cells, J. Biomed. Mater. Res. Part A 89 (2009) 57-67. 

The deposition of titanium oxide thin-films on Mo(l 10) represents a case where the stoichiometry of the film is sensitive to the deposition conditions [4T]. It was found that both Ti02 and Ti203 thin-films could be made. 

Similar to IFP s Dimersol process, the Alphabutol process uses a Ziegler-Natta type soluble catalyst based on a titanium complex, with triethyl aluminum as a co-catalyst. This soluble catalyst system avoids the isomerization of 1-butene to 2-butene and thus eliminates the need for removing the isomers from the 1-butene. The process is composed of four sections reaction, co-catalyst injection, catalyst removal, and distillation. Reaction takes place at 50—55°C and 2.4—2.8 MPa (350—400 psig) for 5—6 h. The catalyst is continuously fed to the reactor ethylene conversion is about 80—85% per pass with a selectivity to 1-butene of 93%. The catalyst is removed by vaporizing Hquid withdrawn from the reactor in two steps classical exchanger and thin-film evaporator. The purity of the butene produced with this technology is 99.90%. IFP has Hcensed this technology in areas where there is no local supply of 1-butene from other sources, such as Saudi Arabia and the Far East. 

Both anatase and mtile are broad band gap semiconductors iu which a fiUed valence band, derived from the O 2p orbitals, is separated from an empty conduction band, derived from the Ti >d orbitals, by a band gap of ca 3 eV. Consequendy the electrical conductivity depends critically on the presence of impurities and defects such as oxygen vacancies (7). For very pure thin films, prepared by vacuum evaporation of titanium metal and then oxidation, conductivities of 10 S/cm have been reported. For both siugle-crystal and ceramic samples, the electrical conductivity depends on both the state of reduction of the and on dopant levels. At 300 K, a maximum conductivity of 1 S/cm has been reported at an oxygen deficiency of... 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Metals that depend on a relatively thick protective coating of corrosion product for corrosion resistance are frequently subject to erosion-corrosion. This is due to the poor adherence of these coatings relative to the thin films formed by the classical passive metals, such as stainless steel and titanium. Both stainless steel and titanium are relatively immune to erosion-corrosion in most cooling water environments. 

It has now gained acceptance as an impressed current anode for cathodic protection and has been in use for this purpose since 1971. The anode consists of a thin film of valve and precious metal oxides baked onto a titanium substrate and when first developed was given the proprietary name dimensionally stable anode , sometimes shortened to DSA. Developments on the composition of the oxide film have taken place since Beer s patent, and this type of anode is now marketed under a number of different trade names. 

Quite recently (2001) titanium dioxide has been used to coat "self-cleaning" windows with a very thin film about 5 x 10-6 cm thick. The titanium dioxide acts as a catalyst for the decomposition of dust and grime by solar ultraviolet light. Probably more important, it lowers surface tension so that rain water "sheets down" the window, washing away dirt. 

DLC coatings are already in production in several areas (optical and IR windows) and appear particularly well-suited for abrasion and wear applications due to their high hardness and low coefficient of friction. They have an extremely smooth surface and can be deposited with little restriction of geometry and size (as opposed to CVD diamond). These are important advantages and DLC coatings will compete actively with existing hard coatings, such as titanium carbide, titanium nitride, and other thin film... 

Interconnect. Three-dimensional structures require interconnections between the various levels. This is achieved by small, high aspect-ratio holes that provide electrical contact. These holes include the contact fills which connect the semiconductor silicon area of the device to the first-level metal, and the via holes which connect the first level metal to the second and subsequent metal levels (see Fig. 13.1). The interconnect presents a major fabrication challenge since these high-aspect holes, which may be as small as 0.25 im across, must be completely filled with a diffusion barrier material (such as CVD titanium nitride) and a conductor metal such as CVD tungsten. The ability to fill the interconnects is a major factor in selecting a thin-film deposition process. 

Titanium(IV) guanidinato complexes, which are easily accessible by the standard synthetic routes (cf. Section III.B.2), have been studied as precursors to titanium carbonitride. Thin films of titanium carbonitride were obtained by low-pressure chemical vapor deposition of either [(Me3Si)2NC(NPE)2]TiCl(NMe2)2 or [Me2NC(NPE)2]2TiCl2 at 600 Most recent developments in this field... 

Darkowski and Cocivera [94] investigated trialkyl- or triarylphosphine tellurides, as low-valent tellurium sources, soluble in organic solvents. They reported the cathodic electrodeposition of thin film CdTe on titanium from a propylene carbonate solution of tri-n-butylphosphine telluride and Cd(II) salt, at about 100 °C. Amorphous, smooth gray films were obtained with thicknesses up to 5.4 p,m. The Te/Cd atomic ratio was seen to depend on applied potential and solution composition with values ranging between 0.63 and 1.1. Polycrystalline, cubic CdTe was obtained upon annealing at 400 C. The as-deposited films could be either p- or n-type, and heat treatment converts p to n (type conversion cf. Sect. 3.3.2). 

Lead sulfide, PbS, nanoparticulate thin films having pancake-like geometry and exhibiting ID quantum confinement, as controlled by the lowest dimension of the particles, have been synthesized by cathodic electrodeposition on TTO/glass and titanium electrodes from a pH 0.62 solution containing Pb(N03)2 and Na2S203 [162]. 

Gonbeau D, Guimon C, Pfister-Guillouzo G, Levasseur A, Meunier G, Dormoy R (1991) XPS study of thin films of titanium oxysulfides. Surface Sci 254 81-89... 

The tltanla-based thin film catalyst models were constructed by first oxidizing the titanium surface In 5 x 10 torr of O2 for approximately 30 minutes at 775 K. This produced an AES llneshape consistent with fully oxidized TIO2. The metal was then vapor deposited onto the oxide support with the latter held at 130 K. The thickness of the metal overlayer and Its cleanliness were verified by AES. After various annealing and adsorption procedures, these thin films were further characterized using SSIMS, AES and TDS. For comparison, some work was done with Pt on Al20s. In this case a Mo foil covered with AI2O3 replaced the Tl(OOOl) substrate. 

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