Optical properties and chemical reactivity of hydrogenated amorphous boron thin films

Abstract

Hydrogenated boron thin films have been deposited at temperatures in the range 50-1 O0 ~ with the radiofrequency plasma decomposition of diborane B2H 6 diluted in hydrogen. The chemical composition of the films has been determined by elastic recoil detection and by the Castaing microprobe techniques. We have found that the as-deposited films contain 10-20 at % H and that they react with the ambient atmosphere within a few days and reach a final composition close to Bo.84 Ho. 120o.12Co.o8 No.os. The optical properties of the as-deposited films studied by spectroscopic phase-modulated ellipsometry in the range 1.7-5.0 eV are characteristic of the high optical gap semiconductors. The electron diffraction measurements performed on in situ annealed samples show that the films are amorphous up to 950 ~ Infrared spectroscopy investigations performed on the as-deposited films have revealed two hydrogen bonding sites: B-H terminal bonds and B-H-B bridge bonds, along with some B-O-B groups. Upon exposure'to the atmosphere, the vanishing of B-H-B and B-O-B bridge bonds and the increase of B-H and B-O-H absorption bands after 1 day, are observed.

Hot Filament Chemical Vapor Deposition of Crystalline Boron Films

“…One important advantage of HFCVD over other methods is its tendency to produce crystalline films. For example, Godet et al 30) prepared hydrogenated boron films by radio frequency plasma decomposition of diborane diluted in hydrogen in the temperature range 50100°C; in contrast to our results, they reported the synthesis of amorphous films up to 950°C. Something important to keep in mind is that no author has reported on the formation of regular faceted crystals, which is the case with this work.…”

Influence of the nitrogen flow rate on the order and structure of PECVD boron nitride thin films

“…Hydrogen content evaluation in the films with increasing r is found by the use of the proportionality constants reported earlier for B-H bending, B-H and N-H stretching bonds [28,29]. The bond concentrations for B-H and N-H modes are presented in Fig.…”

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

“…However, more often than not, such efforts lack sufficient direction and many years are required for applications to come to fruition. 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].…”