Geometry of Chemical Beam Vapor Deposition System for Efficient Combinatorial Investigations of Thin Oxide Films: Deposited Film Properties versus Precursor Flow Simulations

Abstract

An innovative deposition system has been developed to construct complex material thin films from single-element precursors by chemical beam vapor deposition (CBVD). It relies on well distributed punctual sources that emit individually controlled precursor beams toward the substrate under high vacuum conditions combined with well designed cryo-panel surfaces that avoid secondary precursor sources. In this configuration the impinging flows of all precursors can be calculated at any substrate point considering the controlled angular distribution of the emitted beams and the ballistic trajectory of the molecules. The flow simulation is described in details. The major advantage of the deposition system is its ability to switch between several possible controlled combinatorial configurations, in which the substrate is exposed to a wide range of flow compositions from the different precursors, and a uniform configuration, in which the substrate is exposed to a homogeneous flow, even on large substrates, with high precursor use efficiency. Agreement between calculations and depositions carried out in various system configurations and for single, binary, or ternary oxides in mass transfer limited regime confirms that the distribution of incoming precursors on the substrate follows the theoretical models. Additionally, for some selected precursors and in some selected conditions, almost 100% of the precursor impinging on the substrate is incorporated to the deposit. The results of this work confirm the potentialities of CBVD both as a research tool to investigate efficiently deposition processes and as a fabrication tool to deposit on large surfaces.

Amorphous Silicon-Doped Titania Films for on-Chip Photonics

“…In the present work, we report on Chemical Beam Vapour Deposition (CBVD) of high optical quality Si:TiO 2 film whose amorphous state is preserved by doping with silicon [20]. The amorphisation of deposited TiO 2 with Si doping was already reported [21], and a more recent detailed study of amorphisation of Nb:TiO 2 thin films by doping with Si is reported elsewhere [22]. Even though this doping leads to a slight decrease in the refractive index of the film, in agreement with results achieved with other Chemical Vapour deposition techniques [23], the index is still high enough to support waveguiding on highindex optical crystals such as YAG and sapphire.…”

“…Oxide thin films were deposited by CBVD, as described in detail elsewhere [21]. The CBVD process makes use of thermal decomposition of organometallic precursors on a heated substrate in a high vacuum environment (≤ 10 −3 Pa).…”

Widely Tuneable Composition and Crystallinity of Graded Na1+xTaO3±δ Thin Films Fabricated by Chemical Beam Vapor Deposition

“…The depositions were carried out in a CBVD system able to accommodate a 450 mm diameter substrate (Sybilla-450, ABCD Technology, Ferney-Voltaire, France). A similar equipment (Sybilla 150) and the operating mode of this technique are described elsewhere [ 26 ]. Substrate heating is achieved by a graphite heating system radiatively heating the substrate up to 800 °C.…”

“…A multitude of combinatorial configurations are achievable with the possibility to obtain a wide range of flow compositions from the different precursors across the deposition area. In Sybilla equipment [ 26 ], the amount of each precursor reaching a given position of the substrate can, thus, be finely controlled and predicted by accurate calculations, enabling stoichiometry tuning. In addition to negligible gas phase collisions, CBVD has some further peculiarities compared to traditional CVD at higher pressure.…”

“…Furthermore, decomposition is a pure surface mechanism with no pre-activation in the gas phase that can lead to powders and trapping of by-products in the boundary layer, with both having fewer chances to be incorporated into the thin film. The used precursor must, however, have a high sticking coefficient and enhanced decomposition probability on the surface to avoid molecules bouncing off the substrate without reacting [ 26 ].…”