Titanium (III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate) Ti(thd)3 was applied as Ti precursor (combined with [Ba(thd)2]4 and [Sr(thd)2]3 as Ba, Sr sources) for the direct liquid injection MOCVD growth of SrTiO3 and (Ba,Sr)TiO3 layers.
The choice of Ti(thd)3 as Ti precursor was explained as follows: Conventionally, Ti(OiPr)4 is used as Ti precursor for the growth of Ti-contaning multicomponent oxides containing titanium. However, in direct liquid injection MOCVD method, a cocktail source of Ti, Ba, Sr precursors dissolved in organic solvent is used. Thus, to avoid the interactions or ligand exchange among different organic groups (i.e., between the isopropoxide and thd), the homoleptic Ti(III) diketonate precursor Ti(thd)3 was selected as the Ti source.
SrTiO3 (or ST) and (Ba, Sr)TiO3 (or BST) thin films were deposited on Pt passivated Si substrates at deposition temperatures <400°C using Ti(thd)3 and Ba, Sr β-diketonates precursors by electron cyclotron resonance (ECR) plasma-enhanced CVD equipped
with direct liquid injection system; the grown layers were characterized by TEM, SEM and other characterization techniques. Design of experiments (DOE) method was utilized to optimize the process parameters for improving the phase purity, Sr/Ti ratio and permittivity.
As-deposited (at 390°C) unannealed SrTiO3 films demonstrated permittivity of 120 (attributed to the small grain size (150–200 Ả) and presence of Sr rich second phases), and an ohmic contact with the bottom
Pt electrode (related to the observed incubation period at the initial nucleation stages of film growth).[i]
[i] P. Alluri, P. Majhi, D. Tang, S.K. Dey, Integr. Ferroelectrics, An Intern. Journal, 1998, Vol. 21, Iss. 1-4, p. 305-318, « ECR-MOCVD of the Ba-Sr-Ti-O system below 400°C. Part I: Processing »,doi.org/10.1080/10584589808202072 ;www.tandfonline.com/doi/abs/10.1080/10584589808202072
https://www.researchgate.net/profile/Sandwip_Dey/publication/271940322_ECR-MOCVD_of_the_Ba-Sr-Ti-O_system_below_400_degrees_C_-_Part_I_Processing/links/5715202b08ae16479d8ac0f7/ECR-MOCVD-of-the-Ba-Sr-Ti-O-system-below-400-degrees-C-Part-I-Processing.pdf