LIMITATIONS IN THE USE OF IR SPECTRA FOR THE DETERMINATION OF HYDROGEN CONCENTRATION IN a-Si: H FILMS (original) (raw)

Hydrogen in amorphous and microcrystalline silicon films prepared by hydrogen dilution

Journal of applied …, 1996

Hydrogen incorporation in silicon layers prepared by plasma-enhanced chemical-vapor deposition using silane dilution by hydrogen has been studied by infrared spectroscopy ͑IR͒ and elastic recoil detection analysis ͑ERDA͒. The large range of silane dilution investigated can be divided into an amorphous and a microcrystalline zone. These two zones are separated by a narrow transition zone at a dilution level of 7.5%; here, the structure of the material cannot be clearly identified. The films in/near the amorphous/microcrystalline transition zone show a considerably enhanced hydrogen incorporation. Moreover, comparison of IR and ERDA and film stress measurements suggests that these layers contain a substantial amount of molecular hydrogen probably trapped in microvoids. In this particular case the determination of the total H content by IR spectroscopy leads to substantial errors. At silane concentrations below 6%, the hydrogen content decreases sharply and the material becomes progressively microcrystalline. The features observed in the IR-absorption modes can be clearly assigned to mono-and/or dihydride bonds on ͑100͒ and ͑111͒ surfaces in silicon crystallites. The measurements presented here constitute a further indication for the validity of the proportionality constant of Shanks et al. ͓Phys. Status Solidi B 110, 43 ͑1980͔͒, generally used to estimate the hydrogen content in ''conventional'' amorphous silicon films from IR spectroscopy; additionally, they indicate that this proportionality constant is also valid for the microcrystalline samples.

Infrared absorption strength and hydrogen content of hydrogenated amorphous silicon

Physical review. B, Condensed matter, 1992

We have used infrared transmission and nuclear-reaction analysis to determine the ir absorption strength of the Si-H wagging and stretching modes in hydrogenated amorphous silicon (a-Si:H). The films were deposited by plasma-assisted chemical vapor deposition and reactive magnetron sputtering.

Effect of hydrogen on stability of amorphous silicon thin films

Solar Energy Materials and Solar Cells, 2002

This paper presents results of the investigation of hydrogen influence on the stability of low pressure chemical vapour deposition a-Si films. We measured boron-or phosphorus-doped films post-hydrogenated by ion implantation with different hydrogen doses. The dark conductivity after fast quenching and slow cooling and the isothermal relaxation were measured at different annealing temperatures. It was found that higher hydrogen concentration causes greater metastable changes but shorter relaxation time of defects. r

The effect of mixing hydrogen with silane on the electronic and optical properties of hydrogenated amorphous silicon thin films

Thin Solid Films, 1984

The electronic and optical properties of a-Si:H films prepared by the r.f. glow discharge method from a mixture of SiH4 and H2 were studied. The effects of variation in the concentration of H2 in the mixture were also investigated. The dark conductivity of a-Si:H films reaches a minimum at a low concentration of H2 and then increases with increasing concentration of H2. In addition, the photoconductive gain shows a maximum at a low concentration of H2. The band gap, however, remains virtually constant up to 25% H2 and then increases significantly as the H2 concentration is increased further. The activation energy increases slowly with H2 concentration up to 25% and then decreases with a further increase in the H2 concentration. IR vibrational spectra show an increase in the amount of Si—H bonding as the H2 concentration increases to 25% and then a decrease with a further increase in the H2 concentration.

Effect of substrate on hydrogen in and out diffusion from a-Si:H thin films

Journal of Materials Science: Materials in Electronics, 2007

We present a detailed study on the effect of the substrate on the structure and hydrogen evolution from p-type hydrogenated amorphous silicon thin films co-deposited on the grounded and RF electrodes of an asymmetric radio frequency glow discharge reactor, as well as the similar films exposed to an hydrogen plasma. We used spectroscopic ellipsometry and hydrogen evolution measurements to analyze the effects of the substrate, ion energy and hydrogen plasma on the films microstructure, thickness, hydrogen content, hydrogen binding and hydrogen evolution. The hydrogen evolution spectra show a strong substrate dependence. In particular on crystalline silicon substrate, we observe the formation of bubbles. For the various substrates, ion energy and hydrogen plasma treatment do not affect the hydrogen evolution spectra. These results indicate that the action of hydrogen in a-Si:H is modified by the nature of the substrate.

Structural changes studies of a-Si:H films deposited by PECVD under different hydrogen dilutions using various experimental techniques

Vacuum, 2009

Thin film silicon Medium-range order Grain size Hydrogen dilution Microstructure X-ray diffraction Raman analysis FTIR spectrometry a b s t r a c t Plasma enhanced chemical vapour deposition (PECVD) has been used to prepare hydrogenated amorphous silicon (a-Si:H) thin films at different hydrogen dilution of silane source gas. The films were deposited on Corning glass 1737 substrate and on (100) oriented c-Si wafers and characterized by XRD diffraction, micro-Raman and FTIR spectrometry. Experimental data show evolution from amorphous to nanocrystalline silicon and contain the medium-range order (MRO) with varying hydrogen dilution during deposition. From X-ray diffraction and Raman analysis, it is found that the presence of crystalline phase depends on the kind of substrate and on the dilution scale.