NICKEL CYCLOPENTADIENYLS

Nickel bis-cyclopentadienyl (Nickelocene) NiCp2

Nickel bis-cyclopentadienyl (Nickelocene) NiCp2 (or Ni(h5-C5H5)2: Green solid with melting point 173 °C.  

NiCp2 is paramagnetic (2.86 BM; 2 unpaired electrons), has 20-VE (valence electrons). NiCp2 reacts with oxygen, less reactive with H2O. 

NiCp2 is  thermally stable (Ni-CCp ) dissociation energy 285 kJ mol-1. 

NiCp2 can be easily reduced producing (Cp2Ni+: 19-VE, Cp2Ni2+: 18-VE): 

Cp2Ni (0.1 V) → Cp2Ni+ (0.74 V) → Cp2Ni2+ , also forms multidecker sandwich complexes, e.g. Ni2Cp3+. 

Synthesis of NiCp2 : Methathesis from anhydrous NiCl2 and sodium cyclopentadienyl: NiCl2 + 2 Na(C5H5) → Ni(h5-C5H5)2 + 2 NaCl 

NiCp2 is volatile - it has high vapor pressure (max. 43 Torr). 

Nickelocene NiCp2 as MOCVD precursor:

Nickelocene NiCp2 is much less toxic than Ni(CO)4, source temperature 150 °C (starts to decompose at 175 °C), growth can be done in hot-wall reactor (200 – 350 °C). Ni conc. (in gas phase) 0.3 – 1.5 mol %, growth rate 0.2 – 0.8 μm/h (growth rate is limited by mass transfer of NiCp2 to the substrate surface (190 – 230 °C). Composition of deposited layer: 90 wt% Ni, 10 wt% C. Volatile decomposition products of NiCp2: mainly cyclopentadiene, cyclopentene, cyclopentane. H2 as carrier gas is essential to obtain pure Ni films, (to avoid large C impurity.). Ni coatings grown using H2/ He (50%:50% mixture) : showed no C and only 2 at. % O. [i]

 [i] The Chemistry of Metal CVD, International Research Training Group, “Materials and Concepts for Advanced Interconnects”, Prof. Dr. Heinrich Lang

NiCp2 for metallic Ni films by MOCVD

     Nickelocene NiCp2 was applied as precursor for the growth of metallic Ni films by MOCVD; the influence of growth conditions to the growth rate and morphology was presented. Growth rates up to 1 μm/h were obtained; films had nodular morphology, with nodules consisting of small (∼20nm) crystallites. Deposition of Ni films was favored at 160-180°C temperatures, pressures >100 Torr, high H2 partial pressure. This parametric window was determined by the decrease of H2 dissociative adsorption on the surface and by the increase of NiCp2 desorption.[i]

    The composition (carbon impurity content) and the electrical and magnetic properties of NiCp2-grown Ni layers was investigated. The change of layer saturation magnetization with measurement temperature followed Bloch's law. It was found the C contamination decreased with increase of growth pressure, H2 flow rate and with decrease of NiCp2 precursor molar fraction. Higher carbon content worsened ferromagnetic properties (Curie temperature, saturation magnetization,) and electrical conductivity. Carbon impurity was present in the layers in carbidic (interstitial), aliphatic, or cyclic forms. Deposition of these forms and their correlation with the film properties was discussed.[ii]

[i] L. Brissonneau, C. Vahlas, Chem. Vapor Dep., 1999, Vol.5, Iss.4, p.135-142, « MOCVD‐Processed Ni Films from Nickelocene. Part I: Growth Rate and Morphology », https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1521-3862(199908)5:4%3C135::AID-CVDE135%3E3.0.CO;2-1, doi.org/10.1002/(SICI)1521-3862(199908)5:4<135::AID-CVDE135>3.0.CO;2-1

[ii] L. Brissonneau, D. de Caro, D. Boursier, R. Madar, C. Vahlas, Chem. Vapor Dep., 1999, Vol.5, Iss.4, p.143-149, « MOCVD‐Processed Ni Films from Nickelocene. Part II: Carbon Content of the Deposits », https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1521-3862(199908)5:4%3C143::AID-CVDE143%3E3.0.CO;2-5 

NiCp2 for NiO films by MOCVD

     Bis-π-cyclopentadienyl NiCp2 was proposed as precursor for the deposition of NiO films by MOCVD.  The transparent NiO layers were grown at 310°C deposition temperature. The NiO films had NaCl-type crystal structure, according to XRD. The optical properties of the NiCp2-deposited NiO films were determined: optical bandgap was 3.7 eV , refractive index was 2.1.[i]

[i] W.-Ch. Yeh,  M. Matsumura, Jap. J. Appl. Phys., Vol.36,  Part 1, No. 11, Chemical Vapor Deposition of Nickel Oxide Films from Bis-π-Cyclopentadienyl-Nickel, https://iopscience.iop.org/article/10.1143/JJAP.36.6884/meta 

Nickel bis(methylcyclopentadienyl) (Dimethylnickelocene) Ni(MeCp)2

Fig. Ni(MeCp)2 formula

     Nickel bis(methylcyclopentadienyl) (Dimethylnickelocene) Ni(MeCp)2 (M = 216.96) is low-melting solid (mp.34-36°C).

     Ni(MeCp)2 is volatile (boiling point 85-90°C/1Torr) and was therefore proposed as potential precursor for the growth of Ni-containing layers by MOCVD.

    Synthesis of Ni(MeCp)2: Methathesis from anhydrous NiCl2 and sodium cyclopentadienyl: NiCl2 + 2 Na(C5H4Me) → Ni(h5-C5H4Me)2 + 2 NaCl

     Dimethylnickelocene due to its volatility, was applied as MOCVD precursor for the controlled growth of nickel nanoparticles on silicon substrates. Possible use for metallic nickel nanoparticles embedded on Si include the manufacturing of high-density storage media.

     Nickel oxide thin films were from Ni(MeCp)2 as precursor via MOCVD in the presence of O2 or H2O2[.i]

[i] Kumagai, H. et al. J. Mater. Sci. Lett. 15, 1081, (1996)

Nickel bis(ethylcyclopentadienyl) (Diethylnickelocene) Ni(EtCp)2

Fig. Ni(EtCp)2 formula

    Nickel bis(ethylcyclopentadienyl) (Diethylnickelocene) Ni(EtCp)2 (M = 245), is liquid nickel precursor (density d = 1.137 g/mL at 25 °C)

     Ni(EtCp)2 is volatile (boiling point bp.90°C), and was therefore proposed as potential precursor for the MOCVD growth of Ni-containing films.

Ni(EtCp)2 for metal Ni films by MOCVD

       Nickel bis-(ethylcyclopentadienyl) Ni(EtCp)2 was studied as precursor for the CVD deposition of metallic Ni films in 2 reaction systems: Ni(EtCp)2–H2–Ar and Ni(EtCp)2–Ar. Time-of-flight mass-spectrometry of the reaction gas phase studies were used to develop a model reaction scheme of Ni(EtCp)2 transformations  during Ni film growth. The study of process kinetics and layer morphology suggested that the Ni film growth process is controlled by nucleation step in the growth temperature range 760–840 K (487-567°C) in case of Ni(EtCp)2 pyrolysis (without H2) and at 640–810 K (367-537°C) when H2 was added (at Ni precursor partial pressure P[Ni(EtCp)2] = 75 Pa). The values of activation energy of Ni growth processes from Ni(EtCp)2 were 189 ± 9 (without H2) and 115 ± 6 kJ/mol (with H2) for the mentioned temperature regions.[i]

[i] V.S. Protopopova,  S.E. Alexandrov, Surf. Coat. Techn., avail online 20 June 2013, In Press, Corrected Proof « Mass-spectrometric and kinetic study of Ni films MOCVD from bis-(ethylcyclopentadienyl) nickel » 

Ni(EtCp)2 for NiO films by MOCVD

      Nickel bis(ethylcyclopentadienyl) nickel [Ni(EtCp)2], combined with O2 or O3 as oxidant, was applied as precursors for the growth of NiO films by MOCVD. The kinetic regularities of MOCVD processes were studied for the 2 reaction systems: Ni(EtCp)2–O2–Ar and Ni(EtCp)2–O3–O2–Ar, at growth temperatures 600‐820 K (327-547°C). It was found that in the temperature range 600‐700 K (327-427°C) the growth process was controlled by kinetics; the activation energy of the processes was 80±5 kJ·mol−1 in both cases. In the temperature region 700–840 K (427-567°C) the growth process was controlled by mass transport. Nearly twofold decrease of deposition rate was observed on introduction of O3 in the reaction gas phase,  probably due to homogeneous reactions with Ni(EtCp)2.[i]

[i] A. S. Kondrateva, M. Mishin, A. Shakhmin, M. Baryshnikova, S. E. Alexandrov, Physica Status Solidi C, 2015, Vol.12, Iss.7, Special Issue: 20th Biennial European Conference on Chemical Vapor Deposition (EuroCVD 20), see further papers in Phys. Status Solidi A 212, No. 7, p.912-917 , « Kinetic study of MOCVD of NiO films from bis‐(ethylcyclopentadienyl) nickel »,doi.org/10.1002/pssc.201510014, onlinelibrary.wiley.com/doi/abs/10.1002/pssc.201510014 

Share this page