Annealing effects on the optical properties of semiconducting boron carbide

Abstract

Infrared vibrations of as-deposited and annealed semiconducting boron carbide thin films were investigated by midinfrared spectroscopic ellipsometry. The strong boron-hydrogen resonance at ϳ2560 cm −1 in as-deposited films reveals considerable hydrogen incorporation during plasma-enhanced chemical vapor deposition. Extended annealing at 600°C caused significant reduction in film thickness, substantial reduction of boron-hydrogen bond resonance absorption, and development of distinct blue-shifted boron-carbon and icosahedral vibration mode resonances. Our findings suggest that annealing results in substantial loss of hydrogen and in development of icosahedral structure, accompanied by strain relaxation and densification.

Tuning the properties of a complex disordered material: Full factorial investigation of PECVD-grown amorphous hydrogenated boron carbide

“…Therefore, we note that mobility can also apparently be maximized at high temperature/high power conditions, provided the temperature be suitably high (>450 °C), even though this was not evident from the current study as these conditions were not sufficiently explored. On a related note, post-deposition annealing is also known to have an effect on a-B x C:H y properties [57], and-although beyond the scope of the present study-is another important area for more detailed investigation.…”

“…In the case of a-B x C:H y , dozens of materials growth and characterization studies have been published [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], but because these have covered such a wide range of growth methods and resulting a-B x C:H y variants, and because these typically only focus on one or a small number of process conditions or properties at a time, they fail to provide a comprehensive picture of the process-property landscape for this entire material family or any specific variant. One fabrication method that has gained traction, particularly for device applications, is the plasma-enhanced chemical vapor deposition (PECVD) of a-B x C:H y using a single-source molecule-based ortho-carborane (o-C 2 B 10 H 12 ) precursor [48][49][50][51][52][53][54][55][56][57]. We hypothesize that this process yields a more uniform material (due to the 4 use of a single-source precursor), ultimately distinct from those produced using other common deposition methods such as sputtering from a B 4 C target or variations of CVD-based growth from gaseous precursors (e.g., B 2 H 6 , BCl 3 , CH 4 ).…”

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

“…The a-B x C:H y spectra exhibit similar features to those previously reported for other a-BC:H films. 44,[67][68][69] A peak at 3060-3070 cm À1 is attributed to an intra-icosahedral C-H stretching mode, and a peak at 2560 cm À1 to an intra-icosahedral B-H stretching mode. 70 Both of these peaks are also present in the ortho-carborane spectrum, 71 which reinforces their assignment.…”

“…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

“…It should be noted that these values do not take into account trace amounts of Ar observed in the films, present in quantities of 0.1%/0.4% (as-deposited/thermally treated) before sputtering and 1.3%/2.0% (as-deposited/thermally treated) after sputtering, nor do they take into account the presence of hydrogen in the films, which cannot be detected by XPS. The hydrogen concentration is expected to vary as a function of growth conditions and post-growth thermal treatment [25,26]. A significant decrease in the atomic % (at.%) C from ∼31% to ∼23% after surface etching is commensurate with the removal of adventitious hydrocarbon, and a corresponding decrease in the at.% O from 13.9%/16.2% to 11.8%/8.9% (as-deposited/thermally treated) is consistent with the removal of surface oxides [21,24,27].…”