Chemical vapor deposition precursor chemistry. 3. Formation and characterization of crystalline nickel boride thin films from the cluster-assisted deposition of polyhedral borane compounds

Abstract

compounds and to elucidate the important factors for determining the suitability of a source compound for the formation of desirable thin film materials. Acknowledgment. We thank Dr.The deposition of both metal-rich and boron-rich thin-film phases of nickel boride from boron-containing precursor compounds by a cluster deposition process is reported. The thin films were characterized by EDXA, AES, SEM, XRD, FT-IR, TEM, and electron diffraction experiments. The films were shown by AES to be compositionally uniform in the bulk sample. Film thicknesses up to 3 l m were readily prepared by controlling the flow rate of the borane into the cell, the substrate temperature, and the duration of the deposition. The stoichiometric composition of the films was controlled by regulating the deposition temperature, the borane flow rate into the reador, and the base vacuum conditions during the film formation. A relationship was found to exist between the temperature during deposition and the film composition with a maximum nickel content reached at approximately 530 "C. The effect of annealing both the nickel-rich and the boron-rich films was studied by SEM, XRD, and electron diffraction experiments. SEM data for the annealed boron-rich f i showed the formation of perfect hexagonal crystals in a channelled columnar matrix. Electron diffraction data showed that this crystalline phase is hexagonal Ni7B3 isolated in a Ni3B matrix. The as-deposited nickel-rich f i were found by XRD studies to be primarily pure nickel, containing relatively small amounts of the Ni3B phase relative to the pure nickel phase. This has been attributed to the precipitation of boron-rich phases as very small crystallites at the grain boundaries of the pure nickel material. XRD spectra for the boron-rich films showed that the films consisted of Ni3B with no pure nickel observed. Annealing of these films did not result in the formation of pure nickel phases in the XRD spectra. (1) Part 1: Glass, J. A,, Jr.; Kher, S.; Spencer, J. T. Thin Solid F i l m 1992,207,15. Part 2 Glass, J. A., Jr.; Kher, S. S.; Spencer, J. T. Chem. Mater., previous paper in this issue. (2) (a) Thompson, R. Prog. Boron Chem. 1970,2,173. (b) Schwarzkopf, P.; Kieffer, R.; Leszynski, W.; Benesovsky, K. Refractory Hard Metals, Borides, Carbides, Nitrides, and Silicides; MacMillan: New York, 1953. (c) Aronsson, B.; Lundstrom, T.; Rundqvist, S. Borides, Silicides and Phosphides; Wiley: New York, 1965. (d) Boron and Refractory Borides; Matkovick, v. I., Ed.; Springer-Verb: New York, 1977. (e) Samsonov, G. V.; Goryachev, Y. M.; Kovenskaya, B. A.

Chemical vapor deposition of metal borides: 6. The formation of neodymium boride thin film materials from polyhedral boron clusters and metal halides by chemical vapor deposition

“…Appropriate care was taken in handling the boron hydrides under inert atmosphere conditions. [25,26] The anhydrous (99.9%) neodymium(III) chloride (NdCl 3 ) and cobalt(II) chloride (CoCl 2 ) were purchased form Cerac Inc. and were used as received and always handled under an inert atmosphere.…”

“…[25] A quartz reactor tube apparatus (1 × 10 −6 Torr ultimate vacuum) was used which employed a 10 mm (o.d.) tube with an overall length of 60 cm.…”

“…The overall experimental operation of the reactor employed here was similar to that described previously. [1,25] In a typical experiment, 1.0 g (4.0 mmol) of anhydrous (99.9%) neodymium(III) chloride was placed in a quartz boat with the deposition substrates (pyrex, quartz, copper metal or ceramic) suspended directly over the top of the boat. The boat and substrates were then placed in the hot zone of the deposition system at ambient temperature using inert atmosphere techniques.…”

“…In our previous investigations, we demonstrated the deposition of very high quality crystalline solid-state thin films of several metal borides by chemical vapor deposition through the vacuum copyrolysis of gas phase borane hydride clusters and metal halide vapor. [1,20,21,25] These deposition processes were found to occur at significantly lower temperatures, about 800…”

Nano-Metal Borides of Cobalt, Nickel and Copper

“…Wodnieka et al crystallized amorphous Nickel-boride alloys and observed a side product in the final yield [3]. A similar behavior was seen when thin films of Ni 3 B were synthesized by chemical vapor deposition method [4] or during the crystallization of Nickel-Boron metallic glasses [5]. Machizaud et al studied an amorphous alloy, Ni 66 B 34 , and postulated that Ni 7 B 3 decomposes above 500°C to form Ni 3 B and Ni 2 B [6].…”