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Topics in Catalysis

, Volume 61, Issue 12–13, pp 1375–1382 | Cite as

Titanium Tetraisopropoxide Adsorption and Decomposition on Cu(111)

  • M. N. Petukhov
  • P. Birnal
  • S. Bourgeois
  • D. Vantalon
  • P. Lagarde
  • B. Domenichini
Original Paper
  • 160 Downloads

Abstract

Titanium tetraisopropoxide (TTIP) molecules have been deposited on the copper substrate Cu(111) with monolayer coverage at cryogenic, room and elevated temperatures and studied by variable temperature scanning tunneling microscope (STM), X-ray photoelectron spectroscopy (XPS), low electron energy diffraction (LEED) and X-ray absorption near edge structure (XANES) spectroscopy using the synchrotron radiation. Adsorption and irregular assembling of entire molecules are observed at low temperatures. At room temperature, STM reveals an agglomeration of TTIP molecular fragments. The XPS analysis confirms presence of ligand groups bonded to molecular center, indicating a partial decomposition process up to 670 K. TTIP molecules start to decompose completely on copper surface at elevated temperatures, higher than 800 K. Hexagonal surface oxide structure is formed after TTIP monolayer thermal decomposition at 870 K, as it is proved by LEED and STM.

Keywords

Titanium tetraisopropoxide Surface decomposition Copper X-ray absorption near edge structure X-ray photoelectron spectroscopy Scanning tunneling microscopy 

1 Introduction

Titanium tetraisopropoxide Ti(OC3H7)4 (TTIP) is one of predominant precursors used in the chemical vapour deposition (CVD) and atomic layer deposition (ALD) methods to synthesize titanium dioxide thin films. Study of adsorption, decomposition of TTIP molecules and kinetic mechanisms underlying the synthesis of TiO2 has a top interest for various applications. Knowledge of the reaction mechanism of precursors on a metallic substrate surface is essential for selection of the optimum process conditions. Understanding of interaction of growing semiconducting thin films with the copper substrate has particular importance, as copper is a widespread material for providing thermo- and electro-contacts in the modern technology.

Two principal reactions are known for thin film deposition of TiO2 using TTIP; the thermal decomposition [1]:
$${\text{Ti}}{\left( {{\text{O}}{{\text{C}}_3}{{\text{H}}_7}} \right)_4} \to {\text{Ti}}{{\text{O}}_2}+2{{\text{C}}_3}{{\text{H}}_6}+2{{\text{C}}_3}{{\text{H}}_7}{\text{OH}}$$
and hydrolysis
$${\text{Ti}}{\left( {{\text{O}}{{\text{C}}_3}{{\text{H}}_7}} \right)_4}+2{{\text{H}}_2}{\text{O}} \to {\text{Ti}}{{\text{O}}_2}+4{{\text{C}}_3}{{\text{H}}_7}{\text{OH}}.$$

Hydrolysis, having lower activation energy, is more favorable, than pyrolysis [2]. The temperature regimes in the presence of water can be lower. Nevertheless, the thermal treatment is important to improve crystallization of titanium dioxide films [3, 4], as titanium dioxide films in amorphous form have not photocatalytic activity. Temperature variation during CVD synthesis of TiO2 films from TTIP precursor carries out the film structures from polycrystalline anatase to polycrystalline rutile films [5]. Usually, growth at elevated temperatures significantly favors formation of three-dimensional titanium dioxide structures. The substrate material also influences on the TTIP decomposition process at an initial stage and, in the case of metal crystals, substantially modifies properties of ultrathin titanium dioxide films. The decomposition mechanism of TTIP at various temperatures in the absence of H2O was studied by temperature programmed desorption (TPD) method. Detection of reaction products in the gas phase allowed to make important conclusions on Ti(OC3H7)4 precursor transformations on Si(100) crystal [6] and platinum surface [7, 8]. Significant difference of the deposited structures was established for the first adsorbed monolayer and multilayers regime on Au(111) [9] and on Pd(100) and Pd(111) [10]. In the case of TTIP deposition on amorphous copper surface [11] and Cu(100) crystal [12], an oxygen pre-exposure procedure was used, as the growth on the clean surface was very slow. A low sticking coefficient during TTIP adsorption was also found in the case of the amorphous and crystalline copper surfaces. XPS and TPD methods observed very low reactivity during thermal CVD of TTIP on the clean Cu(100) crystal at a standard growth temperature [12].

The present work is aimed at understanding how the TTIP precursor adsorbs and decomposes at various temperatures on a clean Cu(111) single crystal. We investigate interaction of titanium tetraisopropoxide molecules mainly in monolayer coverage to eliminate difficulties of the interface formation during titanium dioxide film growth on the clean copper surface.

2 Experimental

The experiment was carried out in an ultra high vacuum chamber with a base pressure 1 × 10−10 mbar equipped with variable temperature STM (Omicron Nanotechnology), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) techniques. The clean surface of Cu(111) crystal (MaTecK, Germany) was prepared by cycles of argon ion sputtering (0.8 keV, 15 min.) followed by annealing at 700 K. The cleaning cycles were repeated until a sharp pattern of well ordered p(1 × 1) structure of the surface was observed by LEED and no contamination was detectable by means of XPS. The surface remains atomically clean within several hours. A clean well-defined Cu(111) (1 × 1) structure was confirmed by STM images with atomic resolution at room temperature and after liquid nitrogen cooling to 160 K.

X-ray absorption near edge structure (XANES) spectra were obtained in LUCIA beamline of synchrotron SOLEIL. The XANES spectra were acquired in the total yield mode. The clean copper (111) crystal was cooled down to 120 K for TTIP molecules exposition and then warmed up to room temperature and 670 K (standard temperature for titanium dioxide film synthesis from TTIP).

Al Kα excitation was used for XPS spectra acquisition. All spectra were referenced to the Cu 2p3/2 peak of the clean copper surface at 932.7 eV [13]. The XPS spectra were acquired at the emission angle of 60° with respect to the surface normal. The sample was cooled down every time from elevated temperatures to 300–330 K for XPS and LEED analysis, and to room temperature for STM.

STM images were taken with etched Pt/Ir tips. The tips were cleaned by ion sputtering (Ar+, 0.8 keV) and annealed in vacuum at 600 K. The value of copper unit cell aCu = 2.56 Å, was used for calibration of obtained STM images. The STM images were treated by Scanning Probe Image Processor (SPIP) software [14]. The temperature of the sample during STM experiment was controlled by a chromel–alumel thermocouple mounted on the microscope sample holder.

TTIP liquid was placed in a glass tube and mounted on the STM chamber through a leak valve. A few cycles of cooling by the water ice (melting point of TTIP equals 287–290 K) and heating to room temperature were done for TTIP liquid cleaning from dissolved gases. During the cleaning procedure, the volume with the precursor was pumped by a turbo pump to the pressure ~ 10−5 mbar. The tube was further pumped for 10 min every time before the exposition. During TTIP deposition, the pressure inside the system was at order of 10−8 mbar. TTIP molecule has a low sticking coefficient (0.3) [2] and it was expected to have the coverage of few monolayers after 10 L exposition, monolayer after 4 L exposition, and submonolayer after 1 L exposition.

After exposition, the copper crystal was placed on the analysis chamber manipulator equipped by PBN ceramic heating element. The sample was further annealed at 670 K. This temperature was selected as a standard temperature for growth of thick TiO2 films [1, 2, 3, 4, 5]. The elevated temperature 870 K was suggested by TPD studies, as the temperature of total TTIP decomposition on platinum and Si(100) surfaces [8, 9, 10].

3 Results

3.1 XANES

Ti K-edge XANES spectra of TTIP molecules after 10 L of exposition are shown in Fig. 1. The spectra have a peak before the principal edge structure at lower energy close to 4970 eV. This pre-edge peak, corresponding to 1s → 3d excitation, is very sensitive to the local coordination chemistry of titanium atom. This fact is well established by XANES studies of titanium alkoxides [15, 16] and supported by XANES spectra analysis in a large number of minerals containing Ti and O atoms [17]. Intense structure and energy position 4969.5 eV of the spectrum obtained after adsorption at 120 K (Fig. 1a) indicate fourfold coordination of Ti compound, which means that entire molecules of TTIP are adsorbed on copper surface at cryogenic temperature. Significant decreasing of the pre-edge peak intensity and a slight enlargement to higher energy position of the spectrum at room temperature (Fig. 1b) points out partial decomposition of titanium tetraisopropoxide. However, the pre-edge peak maximum is still at the same energy value of 4969.5 eV (see also an inset in Fig. 1), which testifies presence of two components; fourfolds coordinated of entire molecules and fivefolds coordinated of partially decomposed TTIP fragments. The XANES spectrum after annealing at 670 K (Fig. 1c) resembles the spectrum of Ti in fivefold coordination: the pre-edge peak has maximum at 4970.5 eV and a developed edge structure at energy, higher than 4990 eV [17]. However, the pre-edge peak position, the peak intensity and its structure differ from Ti K-edge XANES spectra of antase and rutile lattices of titanium dioxide [15, 17]. Hence, the annealing at 670 K is sufficient for decomposition of TTIP molecules, but is not enough for titanium dioxide formation on the clean Cu(111) surface. Additional data are necessary for identification of the decomposition products on the copper surface after annealing at 670 K.

Fig. 1

Ti K-edge XANES spectra of adsorbed TTIP on Cu(111) at low temperature. Intense pre-edge peak at 4970 eV indicates an entire molecules adsorption (see also text); (a) 120 K; (b) room temperature; (c) after annealing at 670 K

3.2 LEED

Before determination of chemical structure of surface products, electron diffraction method has been used to study structural transformation on the surface after 4 L of TTIP exposition and annealing. LEED patterns of initial clean Cu(111) surface and after TTIP molecules exposition with further annealing are shown in Fig. 2. The pattern of the clean copper surface (Fig. 2a) characterizes a well ordered 6-folded symmetry of the Cu(111) crystal with large terraces (more than 100 nm, as it is revealed by STM). The pattern after 4 L of TTIP exposition at room temperature (Fig. 2b) has a slightly elevated background and less narrow principal spots of the reciprocal lattice. The background of LEED pattern becomes brighter and the spots are much more diffuse after annealing at 670 K (Fig. 2c), indicating on a decrease of the ordering on the surface. The degradation of LEED pattern after annealing at 670 K evidences a partial decomposition and presence of different compounds on the surface, which causes significant surface disordering. An ordered superlattice is formed on the Cu(111) surface only after annealing at elevated temperature 870 K (Fig. 2d).

Fig. 2

The LEED patterns of the initial clean Cu(111) surface (a); after 4 L TTIP exposition at room temperature (b); after annealing at 670 K; after annealing at 870 K. The primary beam energy is Eb = 65 eV

3.3 XPS

The XPS spectra of Ti 2p signal at room temperature and after annealing are shown in Fig. 3. The binding energy of Ti 2p3/2 peak of 4 L TTIP on Cu(111) at room temperature is 459.2 eV, which is close to the literature data of Ti 2p3/2 line binding energy in bulk titanium dioxide (459.0–459.2 eV) and in thick titanium dioxide films grown on metal surfaces (458.6–459.0 eV) [18, 19]. The position of Ti 2p3/2 peak at 458.9 eV was measured after saturation exposure of TTIP on oxidized amorphous copper surface at room temperature [11]. The measured position of Ti 2p3/2 line at room temperature in Fig. 3 is indicative of fully oxidized titanium state after 4 L exposition of TTIP, supposing that mainly four oxygen atoms are bounded to the Ti atom.

Fig. 3

Evolution of Ti 2p XPS spectrum of 4 L exposition of TTIP on Cu(111) at room temperature and after annealing at 670 and 870 K

Figure 4 shows the C1s region of the XPS spectrum at room temperature. The peak shape has a primary maximum around 285 eV and a shoulder at higher binding energy, which suggests that carbon atoms are present in two states. After peak fitting procedure, the binding energy of the first peak at 285.1 eV is consistent with carbon atoms in terminal methyl groups, while the higher energy shoulder at 286.6 eV is well assigned to carbon bounded to the oxygen atom. The measured intensity ratio of 1.8:1 between intensities of two peaks is in good agreement with expected theoretical ratio 2:1 for intact isopropoxide groups. At room temperature, the ratio of elements Ti:O:C is 1:3.4:8.7 after correction of Ti 2p, O1s and C1s peaks intensities on photoionization cross sections. This ratio is reasonably close to theoretical stoichiometry 1:4:12, taking into account uncertainty level of XPS technique. It confirms the fact, that the isopropoxide groups remain on the surface at room temperature.

Fig. 4

XPS spectrum of C1s line at room temperature and the peak fitting compounds corresponding to C–C; C–H and C–O bonds

The XPS spectrum of Ti 2p3/2 signal after annealing at 670 K in Fig. 3 is slightly shifted to lower binding energy 458.5 eV and has a larger line width. It supports the LEED result of surface disordering in Fig. 2c and indicates changing of chemical composition of initially adsorbed molecules. Indeed, the intensity analysis of Ti 2p, O1s and C1s peaks after sensitivity factors correction gives 1:2.7:5.3 ratio for Ti:O:C contents, suggesting a partial decomposition of at least one isopropoxide group. The intensities ratio of Ti 2p and Cu 2p signals decreases by a factor of 2 after annealing. It can be caused by either a titanium atoms redistribution with an increasing of the inelastic mean free path of photoelectrons in the copper substrate, or a partial desorption of entire molecules during annealing.

Further annealing at 870 K decreases Ti 2p3/2 binding energy to 456.0 eV, which is sufficiently lower, than binding energy of a bulk titanium dioxide and higher than the typical energy 454.1 eV of a titanium metallic state [20]. The measured value of EB is close to the binding energy of Ti 2p3/2 level in monolayer surface oxides TiOx on Ni (457.0 eV) [21], on Au(111) (456.3 eV) [22], Pt(111) surface (456.4 eV) [19], and upon oxidation of Ni96Ti6 alloy (110) crystal (456.9 eV) [23]. In such a surface oxide, each titanium atom is bonded to two oxygen atoms and also interacts with electronic system of metallic substrate having a formal valency Ti3+ [24].

The binding energy of O1s peak of a monolayer and a few layers exposition is usually close to 531 eV with some shift on the order of 0.5 eV. After annealing at 670 K and up to 870 K, the O1s peak slightly replaces on 0.3 eV to lower binding energy and shows a pronounced tail at the higher binding energy side. The C1s line intensity of the annealed crystal slightly decreases with regard to oxygen content. The binding energy of the principal C1s peak of Fig. 3 shifts to 284.9 eV after annealing. Whereas, the higher energy component of C–O bonding at 286.5 eV significantly decreases the intensity by a factor of 4. Consequently, the C1s XPS line principally consists of hydrocarbon contaminating products formed after ligand decomposition.

3.4 STM

The model of TTIP molecule is presented in the inset of Fig. 5. The central titanium atom is surrounded by oxygen atoms in tetrahedral orientation. Every oxygen atom is bonded to the propylene group in its turn. The entire molecule is not planar and has a complex 3D configuration [25]. The single isopropoxide branch is about 4 Å long (giving approximately 8 Å in diameter for the entire molecule), which fits well with the estimation of the molecular diameter of TTIP of 7.9 Å from the density and molecular mass of the corresponding liquid [26]. So, one TTIP molecule covers about 50 Å2 of surface area, which is huge in comparison with Cu(111) elementary unit cell area of 5.6 Å2. XPS analysis exhibits good adsorption of TTIP molecules with monolayer coverage on the copper surface at room temperature. The image of TTIP of submonolayer coverage (ca 0.1 ML) at room temperature is shown in Fig. 5. Elongated clusters of 1–3 nm long and around 1 nm large are seen on the clean copper surface. The apparent height of the bright spots of the clusters is 1.2 Å at tunneling current equals to 0.8 nA. It is worthwhile to note, that clusters are aligned by their longer size with Cu(111) surface principal directions \(\left\langle {\bar {1}10} \right\rangle\). It means, that the cluster forming objects have a higher surface diffusion coefficient along the principal directions of (111) plane. The image is obtained at a positive bias voltage (VB = 400 mV) and formed by tunneling into empty states of the electronic density on the surface. Hence, the bright spots of the clusters in Fig. 5 are the titanium atoms and less intense structure, surrounding the spots, corresponds to the ligand groups of TTIP molecule. In order to settle the surrounding structure, further increasing of the tunneling current usually results in clusters instability and stimulates diffusion under the scanning tip. After few consecutive scans, the cluster can totally disappear from the scanned area, which means that the cluster forming objects interact with the surface by weak van-der-Waals forces and/or have low surface diffusion barriers.

Fig. 5

STM image (20 × 20 nm2; Ub = 400 mV; It = 0.8 nA) of TTIP submonolayer on Cu(111) at room temperature. Left inset: 5.5 × 5.5 nm2 zoom of TTIP fragments agglomeration. The closest distance between two titanium atoms of neighboring fragments of 5.2 Å is shown by the cross section line. Right inset: a model of single TTIP molecule; the central grey ball—titanium atom, the red balls—oxygen atoms, the dark grey—carbon atoms and the bright gray—hydrogen atoms

There is no well determined ordering of the bright spots inside the clusters in Fig. 5. Nevertheless, analysis of the closest distance between the bright features gives the value 5.2–5.6 Å for two spots (left inset of Fig. 5) and for three consecutive spots (up left part of the image Fig. 5). This distance is significantly lower, than the value of 8 Å of characteristic molecular size of the entire TTIP molecule. Consequently, the cluster forming objects are partially dissociated tetraisopropoxide molecules. The less intense structures, surrounding the spots, are the ligand groups of the molecule. Some of them are free ligands after partial dissociation, as the structure is not well ordered and widespread up to 20 Å around the bright spots. An order of dissociation cannot be exactly established, however, it is supposed at least the loss of the one isopropoxide group.

The STM image of the exposed copper surface after annealing at 870 K is shown in Fig. 6. Ordered standalone islands around 100–200 Å in size are formed on the Cu(111) surface. The surface of the island is slightly masked by residual gas contamination. However, the islands have a two-dimensional hexagonal structure with the lattice cell constant of 10 Å, see Fig. 6. The bright spots of the structure form a honeycomb arrangement (p6mm 2D symmetry) with the closest distance of 6.0 ± 0.2 Å between the spots. The fast Fourier transform of the island image is shown in the right inset. The structure of the island corresponds well to the obtained LEED pattern after annealing at 870 K, see Fig. 2d. Indeed, the pattern can be simulated by incommensurated superlattice structure with the matrix: \(\left( {\begin{array}{*{20}{c}} {2\frac{2}{3}1\frac{1}{3}} \\ {1\frac{1}{3}2\frac{2}{3}} \end{array}} \right)\), which gives the distance 5.9 Å for the hexagon side and 10.2 Å for the honeycomb unit cell.

Fig. 6

STM image (31 × 31 nm2; Ub = 400 mV; It = 0.8 nA) of the surface oxide island formed on Cu(111) surface after annealing of TTIP monolayer at 870 K. Left inset: 3.5 × 3.5 nm2 zoom of the honeycomb hexagonal structure of the island with the unit cell of 10 Å. Right inset: fast Fourier transform of the island image

4 Discussion

The entire TTIP molecules adsorb on Cu(111) surface at low temperature. XANES Ti K-edge spectrum at 120 K in Fig. 1 unambiguously corresponds to fourfold coordination of Ti atom surrounded by the isopropoxide ligands. The surface diffusion on the copper crystal at cryogenic temperatures is low, as there is no ordering or molecular self-organisation. After heating of a few TTIP monolayers to room temperature, X-ray adsorption spectrum indicates a partial appearance of the 5-folded coordination of titanium atoms. The Ti 2p3/2 peak of XPS spectrum for 1 ML of TTIP at room temperature (Fig. 3) has the high binding energy value EB = 459.2 eV typical for bulk TiO2 oxides [18] and for thick molecular layer after saturated exposition with TTIP vapour [11, 12]. The C1s XPS line peak fitting corresponds to isopropoxide group and the quantitative analysis of Ti 2p, O1s and C1s peak intensities ratio suggests the stoichiometry of the entire TTIP molecule. However, STM study of the submonolayer coverage (Fig. 5) demonstrates the decomposed fragments of TTIP molecules indicating a first step of molecular dissociation on the surface. This fact relates quite well with TPD experiments on Si(100) and Pt surfaces, where the partial TTIP dissociation on the substrate surface was proved at ambient temperature [6, 7].

The annealing at 670 K evidently implements TTIP decomposition, as it is established by XANES and XPS data. However, the quantitative XPS analysis indicates only partial decomposition, because of presence of the ligand components on the surface. The LEED pattern (Fig. 2c) shows the strong disordering, which supports the uncompleted TTIP decomposition. Since the temperature of 670 K is the usual temperature of titanium dioxide film growth (i.e. growth on TiO2 film surface), it is natural to assume that an interaction between TTIP fragments and copper atoms of the surface prevents the definitive fragments decomposition at standard temperature (670 K). Consequently, under CVD deposition with a high coverage, the interface of a titanium dioxide film becomes highly contaminated by carbon and hydrogen.

The rise of the annealing temperature up to 870 K leads to ordering of the deposited surface structure. The hexagonal lattice observed by STM (Fig. 6) and LEED (Fig. 2d) has the honeycomb structure. The honeycomb-like hexagonal structure of the first monolayer of titanium oxide was previously observed on Pt(111) after reactive evaporation of titanium in oxygen atmosphere with the unit cell value of 6 Å [19] and on Au(111) crystals after post annealing of metallic titanium in oxygen with the (2 × 2) unit cell (i.e. 5.8 Å) [27]. The same value of 5.8 Å at (2 × 2) registry with Au(111) substrate was obtained for the two-dimensional honeycomb lattice of TiOx deposited by CVD using TTIP as a precursor [9]. The value of 10 Å determined from the STM image of honeycomb structure on Cu(111) deviates from the value of 6 and 5.7 Å obtained for the honeycomb structures on Pt(111) and Au(111) accordingly. This deviation can be explained by a shorter surface unit cell distance of 2.56 Å for Cu(111), than the cell parameters for Pt(111) of 2.76 Å and for Au(111) of 2.88 Å. The factor of different chemistry of the substrate material cannot be also excluded. For example, the first monolayer structure of TiOx on Pd(111) crystal (lattice constant 2.75 Å), obtained after thermal decomposition of TTIP, has not a honeycomb structure, but a complex zigzag pattern [10]. The Ti 2p3/2 line of XPS spectrum shifts to lower binding energy value EB = 456.0 eV (Fig. 3). Close binding energy values were measured in numerical studies of submonolayer TiOx oxide growth on metal crystals and were attributed to the reduced surface titanium oxide (see XPS results presentation).

An important issue of the submonolayer TiOx structures growth on different substrates is a stacking sequence of Ti, O and a substrate atom, i.e. a sequence of atom layers of the grown oxide structure. Proposed models of stacking type Ti–O–metal or O–Ti–metal vary on the substrate metal used. The stacking of O–Ti–Pt was suggested from XPS data and approved by density functional theory calculations for the TiOx honeycomb structure on Pt(111) [19, 24]. The similar stacking sequence O–Ti–Au was concluded as energetically favorable for surface titanium oxide on Au(111) [27]. In the case of Ni(110) crystal, the interface oxygen layer (Ti–O–Ni stacking) was proposed for titanium reactive oxidation after analysis of Ni 2p3/2 core level spectra [28]. In our case, XPS Cu 2p3/2 spectrum does not allow to make an unambiguous conclusion after annealing of TTIP submonolayer. However, electronegativity of copper is significantly lower, than electronegativity of Pt and Au, and close to the one of Ni, which permits to assume the same layer stacking for copper substrate. Consequently, formation of highly oxidized titanium oxide is complicated for the first monolayer on metallic copper. Indeed, a preliminary saturation by chemisorbed oxygen of Cu(001) crystal was used in a number of studies of titanium oxide ultrathin films deposition [29, 30]. Even after oxygen preadsorption, next few monolayers with complex surface oxide structure are necessary to deposit for accordance of the film lattice to bulk anatase or rutile TiO2 structures [31].

5 Conclusions

We have presented the comprehensive study on details of adsorption and decomposition of titanium tetraisopropoxide on Cu(111) surface at different temperatures. The entire TTIP molecules physisorb on Cu(111) crystal at low temperature (120 K). At room temperature, the first molecular monolayer dissociates on the clean copper surface to Ti(OC3H7)x fragments, where 2 ≤ x ≤ 3. The detached ligands agglomerate with the TTIP fragments on the clean copper surface. The fragments interact with the surface by weak van-der-Waals forces and have anisotropic surface diffusion depending on the surface direction. However, the TTIP molecules are intact for the next layers in multilayer deposition regime.

Annealing at 670 K is not sufficient to complete titanium tetraisopropoxide decomposition on Cu(111) with formation of an ordered titanium oxide. The interaction of TTIP fragments with the copper metal atoms of the surface hampers the titanium oxide formation. Further annealing at 870 K in monolayer coverage transforms deposited TTIP molecules into the hexagonal honeycomb structure of the surface titanium oxide.

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • M. N. Petukhov
    • 1
  • P. Birnal
    • 1
  • S. Bourgeois
    • 1
  • D. Vantalon
    • 2
  • P. Lagarde
    • 2
  • B. Domenichini
    • 1
  1. 1.ICB, UMR 6303 CNRS-Université de Bourgogne Franche-ComtéDijonFrance
  2. 2.Synchrotron SOLEIL, L’Orme des MerisiersGif-sur-YvetteFrance

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