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

Abstract

The chemical vapor deposition (CVD) of crystalline thin films of neodymium hexaboride (NdB 6 ) was achieved using either nido-pentaborane(9) or nido-decaborane(14) with neodymium(III) chloride on different substrates. The highly crystalline NdB 6 films were formed at relatively moderate temperatures (835• C, ca. 1 µm/h) and were characterized by scanning electron microscopy, X-ray emission spectroscopy, X-ray diffraction and glow discharge mass spectrometry. The NdB 6 polycrystalline films were found to be pure and uniform in composition in the bulk material. Depositions using CoCl 2 , NdCl 3 and B 5 H 9 as the CVD precursors resulted in the formation of a mixture of NdB 6 and CoB phases, rather than the ternary phase.

Excellent Field‐Emission Performances of Neodymium Hexaboride (NdB6) Nanoneedles with Ultra‐Low Work Functions

“…No characteristic peaks of impurities are detected, indicating the high purity of the synthesized product. All the diffraction peaks can be well indexed to cubic NdB 6 with a lattice of a = 0.41 nm and a space group of Pm‐3m , in good agreement with the literature values 4a. Figure b displays the RT Raman spectra of the NdB 6 nanoneedles (sample d ).…”

“…Rare‐earth hexaboride (REB 6 ) nanostructures are ideal materials for FE application as an electrical field‐induced ion and electron point source due to their miniature dimensions, low work functions, as well as excellent electrical, thermal, and mechanical properties . The advantages of using REB 6 as a FE candidate originate from their crystal structure, in which the rare‐earth metal atom is embedded inside a stable boron octahedral network.…”

Nanoscaled Metal Borides and Phosphides: Recent Developments and Perspectives

“…This enthusiasm is certainly related to the well-known field emission properties of these compounds, which are enhanced when the materials are shaped into one-dimensional structures, whose synthesis by CVD is relatively straightforward. When rare earth hexaborides are deposited from solely rare earth chlorides and pentaborane or decaborane between 800 and 1000 °C, microparticles are usually obtained. − In order to decrease the particle size, a simple strategy consists of the use of preformed metal nanoparticles, so-called “catalysts” although they are used in stoichiometric quantities: each metal nanoparticle increases the nucleation rate of one nanostructure. Because the nucleation and growth steps are substrate-mediated, the catalyzed CVD process yields one-dimensional growth of metal hexaborides, despite their cubic structure.…”

Nucleophilic Substitution Reactions in the [B3H8]− Anion in the Presence of Lewis Acids

“…The high content of hydrogen [ 11 ] in some adducts determines their use as chemical accumulators of hydrogen [ 7 , 12 , 13 ]. In addition, substituted derivatives of the octahydrotriborate anion can act as ligands in complexes of transition metals [ 14 , 15 , 16 ], which does not exclude their use in the preparation of boride coatings [ 17 , 18 ], as was previously shown for some complexes of the octahydrotriborate anion [ 19 , 20 ]. Substituted [B 3 H 8 ] − derivatives can also be considered as precursors to substituted higher boron clusters (e.g., B 5 H 9 , B 4 H 10 ).…”