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.

Combinatorial high-vacuum chemical vapor deposition (HV-CVD) was used to identify the conditions required to obtain hafnium-doped lithium niobate thin films on sapphire {001} substrates. Niobium tetraethoxydimethylaminoethoxide (Nb(OEt) 4 (dmae)), lithium tert-butoxide (Li(OBu t )), and hafnium tert-butoxide (Hf(OBu t ) 4 ) were used as precursors. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that a single phase of textured {001} Hf-doped lithium niobate film was obtained under certain precursor flux conditions. The lithium content ()) of the textured film was estimated using Raman spectroscopy to be about 49 mol %. The presence of hafnium inside the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements, and the hafnium content of the textured film ([Hf]/([Hf] þ [Nb])) was estimated to be about 3 mol %. XPS data confirmed that Hf and Nb, respectively, are in the þ4 and þ5 oxidation states inside the film. The film consists of nearly parallel {001} hafnium-doped lithium niobate columns with different in-plane orientations.

Combinatorial high vacuum chemical vapor deposition ͑HV-CVD͒ of mixed HfO 2 -Nb 2 O 5 thin films has been demonstrated to yield amorphous layers at substrate temperatures where individually deposited pure HfO 2 and Nb 2 O 5 films are polycrystalline. Spectroscopic ellipsometry of the films shows that adding HfO 2 to Nb 2 O 5 improves the transparency of the films while still maintaining a high refractive index. Atomic force microscopy measurements show that the root-mean-square surface roughness of the films is about 1.2 nm.

A combinatorial chemical beam epitaxy technique was used to optimize deposition of ͕001͖ lithium niobate thin films on ͕001͖ sapphire substrates. Lithium tert-butoxide ͓Li͑OBu t ͔͒ and niobium tetra-ethoxy di-methyl-amino-ethoxide ͓Nb͑OEt͒ 4 ͑dmae͔͒ were used as precursors. The highest quality films obtained exhibited rocking curve full-width at half-maximum values of about 0.03°and lithium contents ͕͓Li͔/͓͑͑Li͒͒ + ͑Nb͔͖͒ larger than 48 ͑mol %͒ estimated by Raman spectroscopy. High-resolution transmission electron microscopy observations revealed that the lithium niobate film consists of a buffer layer ͑thickness Ͻ8 nm͒ with a high density of defects above which the epitaxial lithium niobate film was obtained.The increasing demand in high bandwidth telecommunication attracts a lot of interest to optical communication networks for both long-distance and metropolitan applications. 1 At the heart of these networks lie lithium niobate modulators, which modulate the electronic data onto the light. 2 Present optical modulators are realized in bulk lithium niobate, while the interest in higher integration and also better performance 3 drives efforts toward high quality epitaxial lithium niobate thin films. Implementing in thin film can also lead to improvements in other applications of lithium niobate, such as periodically poled lithium niobate devices for higher harmonics generation, 4 and in whispering gallery mode resonators. 5 In the past, lithium niobate has been deposited using several methods such as chemical vapor deposition ͑CVD͒, 6,7 pulsed laser deposition, 8 sputtering, 9 and chemical beam epitaxy ͑CBE͒. 10 Lithium tantalate, sapphire, and single crystal magnesium oxide ͑MgO͒ are substrates on which the epitaxial lithium niobate growth has been reported so far. Among these substrates, sapphire is the most interesting one because, compared to lithium tantalate, it has a larger refractive index in contrast with lithium niobate and compared to MgO, it has better mechanical properties. Additionally the ͑111͒ surface of MgO is unstable and is known to reconstruct during annealing. 11 This can have an adverse effect on film growth by hampering epitaxy.In this paper, we report on using combinatorial CBE to optimize the deposition conditions of obtaining epitaxial ͕001͖ lithium niobate thin films on ͕001͖ sapphire. CBE is a CVD process that is conducted under high vacuum conditions ͑pressure less than 5 ϫ 10 −5 mbar͒ in which the precursor molecules are nearly free from gas-phase collisions. Combinatorial methods have been widely applied in synthesis and screening of organic compounds, in particular, for drug discovery 12 as well as in building compound materials libraries. 13 They were introduced for fabrication and optimization of thin films through the pioneering work of Danielson et al., 14 in which they used a combinatorial electron-beam evaporation technique for discovery and development of new compounds for ultraviolet-excited phosphors for flat-panel displays.This work initiated a strong activity in developi...

The authors report on the ability to control the polarity of sputter deposited AlN(001) thin films using seed layers. Reactive sputter deposition leads to N-polarity on any substrate hitherto applied, i.e., Si(111), sapphire, SiO2, and polycrystalline metals such as Pt(111), Mo(110), and W(110). A site-controlled polarity allows for an efficient excitation of shear modes of surface, bulk, and Lamb waves by interdigitated electrodes. The authors were able to introduce the Al-polarity through a metal-organic chemical-vapor deposition seed layer. By subsequently patterning the substrate surface, it was possible to define the desired film polarity of sputter deposited AlN film. Polarities were determined by selective etching with KOH solutions and by piezoresponse force microscopy.