TITANIUM CYCLOPENTADIENYLS - HALIDES

Titanium bis(cyclopentadienyl) dichloride (Titanocene dichloride) Ti(η5-Cp)2TiCl2

Fig. Vapor pressure vs. temperature of TiCp2Cl2

Titanium bis(cyclopentadienyl) dichloride (Titanocene dichloride) Ti(η5-Cp)2TiCl2 is solid, which sublimes at temperatures <190°C without any structure modification.

    Synthesis of titanocene dichloride:

TiCl4 + 2 Na(Cp) → Ti(η5-Cp)2Cl2 + 2 NaCl 

      Vapor pressure equation of TiCp2Cl2 was determined (Fig.): 

 log (P, Pa) = 15.23 (A)–5704.7 (B)/ T(K) (in the range 402-506 K).  

TiCp2Cl2 TGA/DSC

Fig. TGA of TiCp2Cl2

   Thermal behaviour of TiCp2Cl2 was investigated by TGA and DSC by Slifirski et al.[i]. The TGA/DSC measurements demonstrate, that Cp2TiC12 sublimes without any structural modification up to 190°C. In the temperature range 190-290°C the sublimation is in competition with a phenomenon/ structural modification which increases the residue amount, but practically does not change the elemental composition (possibly it is dimerization or a polymerization). The melting temperature of the monomer (or dimer) is ~290 °C ; it is  accompanied or immediately followed by a decomposition of the compound. This decomposition is kinetically controlled whereas melting is only limited by heat transfer.

     From a CVD point of view the sublimation of the molecule and its subsequent decomposition in the thermal gradient layer in the vicinity of the substrate or the transfer in the gas phase of by-products (and probably also their transformation in the thermal gradient layer) ( resulting from the decomposition in the crucible) are not at all equivalent. In the first case a coating of poor quality was obtained at a low deposition rate, whereas the preliminary thermal decomposition at a higher growth rate produces a good quality layer.

     Thermodynamic analysis was applied as a useful tool for investigation of titanocene dichloride Cp2TiC12 as precursor material for MOCVD growth of Ti-containing electronic materials. [ii]

 [i] J. Slifirski, G. Huchet, F. Teyssandier, J. de Physique IV Colloque, 1991, 02 (C2), pp.C2-625-C2-631. « TITANOCENE-DICHLORIDE AS A METALORGANIC SOURCE FOR TITANIUM CARBIDE ». <10.1051/jp4:1991275>. <jpa-00249865>, https://hal.archives-ouvertes.fr/jpa-00249865/document

[ii] C. Bernard, A. Pisch, F. Weiss and R. Madar, MRS Symp. Proc. (Symp. BB – Metal-Organic Chemical Vapor Deposition of Electronic Ceramics II), 1995, Vol.415, 137, « Thermodynamic Analysis, a useful Tool for MOCVD », doi.org/10.1557/PROC-415-137 

TiCp2Cl2 for TiCx films by MOCVD

Fig. TiC composition vs. growth parameters (precursor composition, growth temperature)

Titanocene dichloride Ti(η5-Cp)2Cl2 was applied as single source Ti/C precursor for the growth of TiC thin films on steel at low temperatures. The advantage of TiCp2Cl2 is that it is readily decomposable precursor organometallic molecule. However optimal choice of deposition process conditions  ( temperature, pressure, and H2 dilution)  is needed to avoid excess carbon incorporation into the coating. Fig. shows the effect of precursor composition on the temperature of excess carbon appearance / deterioration in mechanical properties. [[i]]

[i] J. Slifirski, F. Teyssandier, Chem. Vap. Dep., 1996,Vol.2, Iss.6, p. 247-251, « Thermodynamic approach to the OMCVD of titanium carbide from titanocene dichloride », https://doi.org/10.1002/cvde.19960020608

https://onlinelibrary.wiley.com/doi/abs/10.1002/cvde.19960020608

TiCp2Cl2 for TiCx coatings on MW CNTs by MOCVD

    Bis(cyclopentadienyl)titanium dichloride precursor was applied as Ti precursior for the deposition of nanostructured titanium carbide (TiC) coatings on the surface of multiwalled carbon nanotubes (MWCNTs) by MOCVD. XRD, SEM and HRTEM were used to chaeracterize the obtained TiC/MWCNT hybrid materials. It was established that TiC coatings were deposited onto the MWCNT surface with the formation of a core–shell (MWSNT–TiC) type structure. [i]

[i] K. V. Kremlev, A. M. Ob”edkov, S. Yu. Ketkov, B. S. Kaverin, N. M. Semenov, S. A. Gusev, D. A. Tatarskii, P. A. Yunin, Technical Physics Letters, 2016, Vol.42, Iss. 5,  pp 517–519 , « Pyrolytic deposition of nanostructured titanium carbide coatings on the surface of multiwalled carbon nanotubes », https://link.springer.com/article/10.1134/S1063785016050278

TiCp2Cl2 for TiN/Ni composite coatings by MOCVD

      Dichlorobis(η5- cyclopentadienyl)titanium (IV) (or titanocene dichloride) TiCp2Cl2 was applied as Ti precursor (combined with  N,N'-ethylene-bis(2,4-pentanedion-iminoato)nickel(II) as Ni source and N2 plasma as N source) for the growth of titanium nitride (TiN)/nickel (Ni) composite coatings on Si and stainless steel substrates by plasma assisted MOCVD, at substrate temperatures 450- 550ºC and process pressure 0.5-1 mbar. The equilibrium vapour pressure measurements of TiCp2Cl2 by employing TG/DTA in transpiration mode were performed, the  standard enthalpy of sublimation (ΔHo sub) was determined to be 109.2 ± 5.6 kJ/mol.  Ni/TiN nanocomposite coating contained nanocrystals of Ni and TiN with face centered cubic structure, according to the phase identification using glancing incidence XRD. TIN/Ni nanocomposite layers grown using TiCp2Cl2 had uniform surface morphology by SEM, whereas EDX chemical analysis confirmed the presence of Ti, Ni and N in the composite films. [[i]]

Vapor pressure equation of TiCp2Cl2 was determined:

log (pe/Pa) =(15.23±1.27)(A)–(5704.7±53.7)(B)/T(K) (402-506 K)

[i] S. Arockiasamy, T. Maiyalagan, P. Kuppusami, C. Mallika, K.S. Nagaraja, Micro and Nanosystems, 2012, Vol.4, No. 3, pp. 199-207(9), « Deposition of Ni/TiN Composite Coatings by a Plasma Assisted MOCVD Using an Organometallic Precursor », www.ingentaconnect.com/content/ben/mns/2012/00000004/00000003/art00006

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