Characterization of a-B/C: H films deposited from different boron containing precursors

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

“…Because a-B x C:H y contains very low-Z atomic constituents (B, C, and H), which implies a low mass and electron density, we expect e 1 to be low, which is found to be the case here. The range of e 1 values observed is also consistent with those previously found in PECVD a-B x C:H y films, wherein e 1 values of $2-4 were observed, 35,49 and in higher density crystalline B x C, wherein e 1 values of $7 were measured. 97 Further, because a-B x C:H y contains only low polarity bonds (B-B, B-C, B-H, and C-H), which implies low distortion and orientation polarization contributions, we expect the electronic polarization contribution, e 1 , to dominate j, which is indeed observed.…”

“…In particular, the plasma-enhanced chemical vapor deposition (PECVD) of films from ortho-carborane (o-C 2 B 10 H 12 ), which typically yields amorphous hydrogenated boron carbide (a-B x C:H y ) when lower growth temperatures are used, has been shown to be suitable for producing films for device applications as well as conducive to tuning properties over a wide range. [35][36][37][38][39][40][41][42][43][44] With tunability, however, comes complexity, and although the ability to vary properties bodes well for optimizing a material system, there has neither been an extensive study on just how variable these properties can be nor an emphasis on understanding their physical underpinnings. Such investigations will be critical if boron-carbide-based materials are to meet the stringent material requirements for next-generation technologies.…”

The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights

“…In the pre-etched samples, a dominant peak at 284.2/284.7 eV is characteristic of adventitious hydrocarbon [24,40]. A second peak at 282.2/282.5 eV is characteristic of C-B bonds [22][23][24], consistent with the expected coordination environment of C in films based on the C 2 B 10 icosahedral subunit, wherein each C is expected to be bound to at least one adjacent C atom and five adjacent B atoms. A small shoulder at 286.2/286.5 eV is attributed to the presence of C-O or C=O species [40], and there is evidence for a small amount of carboxyl [C(=O)OH] species in the thermally treated sample via the presence of a very small peak at >288 eV [40].…”

“…The lowest BE component is near that expected for a pure boron film (at 187.9 eV) [28], and is characteristic of B atoms bound to other B atoms. The slightly higher BE component represents B atoms additionally bound to one or more C atoms [22,28]. However, because amorphous hydrogenated boron carbide exhibits a complex extended molecular structure and the B atoms exist in multiple bonding environments including B-H bonding environments (e.g., B-B 6 , B-B 5 C, B-B 4 C 2 , B-B 4 CH, etc), deconvolution into only two main peaks does not capture this complexity.…”

The local physical structure of amorphous hydrogenated boron carbide: insights from magic angle spinning solid-state NMR spectroscopy

“…Owing to their unique chemical, electrical, thermal, and mechanical properties, boron-rich carbide (BC) thin films have generated significant interest as heterostructure materials in high-temperature thermoelectric energy converters [1][2][3][4], as low-k dielectric materials for ultra-large-scale integrated circuits [5,6] and as p-type semiconductors for directconversion solid-state neutron detectors [7]. Of the many methods developed for the fabrication of BC films [8][9][10][11][12][13][14], the plasma-enhanced chemical vapour deposition (PECVD) of BC from the sublimed vapour of the single-source solid precursor orthocarborane (1,2-C 2 B 10 H 12 , 1a) stands out as a reliable route to high-resistivity (10 10 -10 13 cm) devicequality films [15][16][17][18][19][20][21]. This method produces hydrogenated B x C:H y films with a relatively narrow range of B x C stoichiometries (x ≈ 2-5) (compared to the wider range possible when using individual C-and B-containing precursors) [11], which do not show evidence of segregated carbon phases known to reduce bulk electrical resistivity [22] as commonly observed in BC films prepared by other methods [23][24][25][26][27].…”