An EELS and EXELFS study of amorphous hydrogenated silicon carbide

Abstract

Abstract.A series of thin films of amorphous hydrogenated silicon carbide (a-Si : C : H) produced by RF plasma decomposition of propane and silane has been studied by electron energy-loss spectroscopy (EELS) and extended energyloss fine structure (EXELFS) studies. The composition of the films has been determined by EELS and the nearest neighbour spacings have been determined by EXELFS. These results, along with the energy of the plasmon loss peaks, have been compared with the deposition conditions for each film. The results show that for a large gas ratio (C3Hs/(C3H8 + SiH4) ) the films have a high proportion of carbon and are similar to a-C : H in structure, whereas those films prepared with Y = 0.4 or 0.5 have nearest neighbour spacings consistent with those for tetrahedrally bonded carbon. The films prepared with lowest Y have nearest neighbour spacings similar to those for amorphous silicon carbide. The results for a-Si : C : H have been compared with the results of EELS and EXELFS of CVD diamond films, amorphous carbon and amorphous silicon.

Changes in chemical composition and nanostructure of SiC thin films prepared by PECVD during thermal annealing

“…The fine structure of both the SiL 2, 3 and the CK edges is not pronounced in the as‐deposited SiC films due to the amorphous network, where bond lengths and angles vary strongly. The ELNES of the SiL 2, 3 edge of a‐Si 0.4 C 0.6 (from Cook et al 13) is in good agreement with the spectra acquired from the as‐deposited stoichiometric SiC film. The ELNES of the as‐deposited Si‐rich Si 1– x C x film is less pronounced than the ELNES of the SiL 2, 3 edge of amorphous Si [Fig.…”

“… (a) the SiL 2, 3 edge of the as‐deposited Si‐rich Si 1– x C x thin films compared to the SiL 2, 3 edge of amorphous Si 12, and the SiL 2, 3 edge of the as‐deposited near stoichiometric SiC thin film is compared to the SiL 2, 3 edge of amorphous SiC (a‐Si 0.44 C 0.56 ) prepared by PEVCD 13. In (b) the SiL 2, 3 edges of the annealed near stoichiometric SiC film and Si‐rich Si 1– x C x film are compared to the SiL 2, 3 edges of crystalline SiC 14 and of the CZ Si substrate, respectively.…”

“… In (a) the CK edge of the as‐deposited stoichiometric SiC film and the as‐deposited Si‐rich SiC film are shown together with the CK edges of amorphous Si 0.56 C 0.44 and Si 0.6 C 0.4 from Ref. 13. (b) Displays the CK edges of the annealed stoichiometric SiC film and the Si‐rich Si 1– x C x film with the CK edges of crystalline SiC 15.…”

“…The plasmon energy of bulk Si is 16.8 eV 20. However, the plasmon energy is shifted to higher energies, when the cluster size of amorphous or nanocrystalline Si is in the range of a few nm 21.The plasmon energies can also be shifted due to the incorporation of C. Cook et al 13 described such a shift of the plasmon energy with chemical composition of a‐SiC:H films. The shoulder at around 8 eV is attributed to interface plasmons at Si clusters in the as‐deposited material or Si NCs in the annealed Si‐rich Si 1– x C x thin film.…”

“…In Fig. 9(a), the CK edges of the as‐deposited stoichiometric and Si‐rich Si 1– x C x films are compared to the CK edge of a‐Si 0.44 C 0.56 and a‐Si 0.6 C 0.4 , respectively 13. In the spectra of the CK edge of the as‐deposited stoichiometric SiC film, almost no pre‐peak (π* peak) can be observed, whereas the CK edge of the as‐deposited Si‐rich Si 1– x C x film shows a more pronounced π* peak.…”