Increased drift carrier lifetime in semiconducting boron carbides deposited by plasma enhanced chemical vapor deposition from carboranes and benzene

Peterson, George; Echeverría, Elena; Dong, Bin; Silva, Joseph P.; Wilson, Ethiyal R.; Kelber, Jeffry A.; Nastasi, M.; Dowben, Peter A.

doi:10.1116/1.4973338

Cited by 10 publications

(17 citation statements)

References 19 publications

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“…The effective drift carrier lifetimes, characteristic of our semiconducting boron carbide alloyed films from aniline/orthocarborane, with 5:1 and 10:1 ratios deposited by PECVD, were extracted from the C ( V ) and I ( V ) curves. ,,, The procedure begins by extracting the slope of the I ( V ) curve. The slope is defined as the low frequency conductance, G 0 , and it can be defined as where I is the measured current and V a is the applied bias in volts.…”

Section: Resultsmentioning

confidence: 99%

“…The I ( V ) and C ( V ) measurements (Figure ) indicate rich carrier dynamics dependent upon aniline content. From the I ( V ) and C ( V ) measurements, an effective drift carrier lifetime can be determined. ,, For the PECVD boron carbide composite films, from an aniline/orthocarborane 5:1 mixture, the I ( V ) and C ( V ) data were used to extract a carrier lifetime on the order of 80 μs. As mentioned previously, the capacitance rises rapidly and saturates before 1 V (Figure b).…”

Section: Discussionmentioning

confidence: 99%

“…The results indicate that, in accord with other PECVD boron carbide films derived from aromatic/orthocarborane precursor mixtures, ,, states near the valence band maximum are aniline-like, while states near the conduction band minimum are either of aniline or carborane character. A novel finding for aniline/orthocarborane composites, however, is that the charge transport lifetimes vary significantly with aromatic content of the film, with lifetimes longer than those for PECVD boron carbide films made without aniline, but substantially shorter than lifetimes reported for other aromatic/carborane films, , and orders of magnitude longer than those for polymerized aniline. This indicates a charge transport mechanism (or mechanisms) substantially different from that of either polymerized aniline or of PECVD carborane films without aromatic content.…”

Section: Introductionmentioning

confidence: 90%

“…Hydrogenated boron carbide films, formed by PECVD of orthocarborane and aromatic species, are p-type. − I ( V ) and C ( V ) measurements were, therefore, carried out at applied ac voltage frequencies on diode structures formed by the PECVD of aniline/orthocarborane films on n-type Si substrates. Ti–Au contacts were deposited by dc magnetron sputtering in an UHV chamber with base pressure better than 1 × 10 –8 Torr, as previous work has shown that such contacts minimize Schottky barrier issues. , Charge transport lifetimes were extracted from C ( V ) data as discussed previously …”

Section: Methodsmentioning

confidence: 99%

“…Boron carbide films are of significant interest in applications such as neutron detection − and photocatalysis. , Recently, a class of such materials containing carborane icosahedra bonded to aromatic species, boron carbides alloyed with aromatic moieties, − has become of interest for such applications , due to enhanced electron–hole separation and drift carrier lifetimes compared to carborane-derived boron carbide films without aromatic content. − For example, plasma enhanced chemical vapor deposition (PECVD) films derived from orthocarborane and pyridine precursors exhibit an 850% increase in charge collection, on a per-B atom basis, compared to PECVD orthocarborane films without aromatic content, in zero bias neutron voltaic measurements. ,, Such aromatic moieties provide for π-bonded bridges between carborane icosahedra. − The detailed relationship between such chemical interactions and resulting charge transport properties, however, remains to be determined.…”

Section: Introductionmentioning

confidence: 99%

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Composition-Dependent Charge Transport in Boron Carbides Alloyed with Aromatics: Plasma Enhanced Chemical Vapor Deposition Aniline/Orthocarborane Films

et al. 2018

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Boron carbide films, alloyed with aniline moieties, were deposited by plasma enhanced chemical vapor deposition (PECVD) from aniline and orthocarborane precursors and were found to exhibit composition-dependent drift carrier lifetimes as derived from I( V) and C( V)) measurements. For a film with an aniline/carborane ratio of 5:1, the effective drift carrier lifetimes are ∼80 μs at low bias voltage but quickly drop to a few microseconds with increasing bias. A film with a 10:1 aniline/carborane ratio, however, exhibited lifetimes of ∼6 μs, or less, at 1 kHz, and much smaller values at 10 kHz. These lifetimes are orders of magnitude longer than those in polyaniline films and comparable to those in PECVD carborane films without aromatic content. X-ray photoelectron spectroscopy (XPS), FTIR, and ellipsometry, combined with density functional theory (DFT)-based cluster calculations, indicate that aniline and orthocarborane moieties are largely intact within the films. Bonding occurs primarily between aniline C sites and carborane B sites, and the aniline coordination number per carborane icosahedron is ∼2 as the aniline/carborane ratio is increased from 3:1 to 10:1. This aniline/carborane coordination ratio independent of aniline/orthocarborane stoichiometry is consistent with the dependence of charge transport properties on aniline film content at high bias voltage.

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